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Surgery_Schwartz. in water) to minimize errors resulting from warming of the fluid as it transferred from its reservoir to a syringe for injection.Technologic innovations have been introduced that per-mit continuous measurement of QT by thermodilution. In this approach, thermal transients are not generated by injecting a bolus of a cold indicator, but rather by heating the blood with a tiny filament located on the PAC upstream from the thermistor. By correlating the amount of current supplied to the heating element with the downstream temperature of the blood, it is pos-sible to estimate the average blood flow across the filament and thereby calculate QT. Based upon the results of several studies, continuous determinations of QT using this approach agree well with data generated by conventional measurements using bolus injections of a cold indicator.15 Information is lacking regarding the clinical value of being able to monitor QT continuously.Mixed Venous OximetryThe Fick equation can be written


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Surgery_Schwartz. using bolus injections of a cold indicator.15 Information is lacking regarding the clinical value of being able to monitor QT continuously.Mixed Venous OximetryThe Fick equation can be written as222QVO(COCO)Tav=−where CaO2 is the content of oxygen in arterial blood and CvO2 is the content of oxygen in mixed venous blood. The oxygen content in both arterial and venous blood is a function of the hemoglobin concentration in the blood, the hemoglobin satura-tion, and the partial pressure of oxygen:CO1.36HgbSO1000.0031POa/v2a/v2a/v2=××˛˝˙ˆˇ˘+×CO1.36HgbSO100//av2av2=××˛˝˙ˆˇ˘where Sa/vO2 is the fractional saturation of hemoglobin in either arterial or venous blood, Hgb is the concentration of hemoglobin Brunicardi_Ch13_p0433-p0452.indd 43922/02/19 2:21 PM 440BASIC CONSIDERATIONSPART Iin blood, and Pa/vO2 is the partial pressure of oxygen in the arte-rial or venous blood. Under most circumstances the contribution of dissolved oxygen to both CaO2 and CvO2 is negligible, allow-ing the


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Surgery_Schwartz. blood, and Pa/vO2 is the partial pressure of oxygen in the arte-rial or venous blood. Under most circumstances the contribution of dissolved oxygen to both CaO2 and CvO2 is negligible, allow-ing the second portion of equation to be functionally eliminated (see previous equation). Given that, if the Fick equation is rear-ranged to the following:2COCOVOQv2a2T=−Oxygen saturation can replace oxygen content, yielding the final clinically valuable equation:(1.36)222SOSOVOQHgbvaT=−××where SVO2 is the fractional saturation of hemoglobin in mixed venous blood, SaO2 is the fractional saturation of hemoglobin in arterial blood, and Hgb is the concentration of hemoglobin in blood. Thus, it can be seen that SVO2 is a function of VO2 (i.e., metabolic rate), QT, SaO2, and Hgb. Accordingly, subnormal val-ues of SVO2 can be caused by a decrease in QT (due, for example, to heart failure or hypovolemia), a decrease in SaO2 (due, for example, to intrinsic pulmonary disease), a decrease in Hgb (i.e.,


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Surgery_Schwartz. val-ues of SVO2 can be caused by a decrease in QT (due, for example, to heart failure or hypovolemia), a decrease in SaO2 (due, for example, to intrinsic pulmonary disease), a decrease in Hgb (i.e., anemia), or an increase in metabolic rate (due, for example, to seizures or fever). With a conventional PAC, measurements of SVO2 require aspirating a sample of blood from the distal (i.e., pulmonary arterial) port of the catheter and injecting the sample into a blood gas analyzer. Therefore, for practical purposes, mea-surements of SVO2 can be performed only intermittently.By adding a fifth channel to the PAC, it is possible to mon-itor SVO2 continuously. The fifth channel contains two fiber-optic bundles, which are used to transmit and receive light of the appropriate wavelengths to permit measurements of hemoglobin saturation by reflectance spectrophotometry. Continuous SVO2 devices provide measurements of SVO2 that agree quite closely with those obtained by conventional analyses of


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Surgery_Schwartz. measurements of hemoglobin saturation by reflectance spectrophotometry. Continuous SVO2 devices provide measurements of SVO2 that agree quite closely with those obtained by conventional analyses of blood aspi-rated from the pulmonary artery. Despite the theoretical value of being able to monitor SVO2 continuously, data are lacking to show that this capability favorably improves outcomes. In a prospective, observational study of 3265 patients undergoing cardiac surgery with either a standard PAC or a PAC with con-tinuous SVO2 monitoring, the oximetric catheter was associated with fewer arterial blood gases and thermodilution cardiac out-put determinations but no difference in patient outcome.16 Since pulmonary artery catheters that permit continuous monitoring of SVO2 are more expensive than conventional PACs, the routine use of these devices cannot be recommended.The saturation of oxygen in the right atrium or superior vena cava (ScvO2) correlates closely with SvO2 over a wide range


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Surgery_Schwartz. conventional PACs, the routine use of these devices cannot be recommended.The saturation of oxygen in the right atrium or superior vena cava (ScvO2) correlates closely with SvO2 over a wide range of conditions,17 although the correlation between ScvO2 and SvO2 has been questioned.18 Since measurement of ScvO2 requires placement of a central venous catheter rather than a PAC, it is somewhat less invasive and easier to carry out. By using a cen-tral venous catheter equipped to permit fiber-optic monitoring of ScvO2, it may be possible to titrate the resuscitation of patients with shock using a less invasive device than the PAC.17,19 The Surviving Sepsis Campaign international guidelines for the management of severe sepsis and septic shock recommends that during the first 6 hours of resuscitation, the goals of initial resuscitation of sepsis-induced hypoperfusion should include all of the following: CVP 8 to 12 mm Hg, MAP ≥65 mm Hg, urine output ≥0.5 mL/kg per hour, and ScvO2 of 70% or


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Surgery_Schwartz. the goals of initial resuscitation of sepsis-induced hypoperfusion should include all of the following: CVP 8 to 12 mm Hg, MAP ≥65 mm Hg, urine output ≥0.5 mL/kg per hour, and ScvO2 of 70% or SvO2 65%.20EFFECT OF PULMONARY ARTERY CATHETERIZATION ON OUTCOMEDespite initial enthusiasm for using the PAC in the manage-ment of critically ill patients, several studies have failed to show improved outcomes with their use. Connors and col-leagues reported results of a major observational study evaluat-ing the value of pulmonary artery catheterization in critically ill patients.21 These researchers compared two groups of patients: those who did undergo placement of a PAC during their first 24 hours of ICU care and those who did not. The investiga-tors recognized that the value of their intended analysis was completely dependent on the robustness of their methodology for case-matching because sicker patients (i.e., those at greater risk of mortality based upon the severity of their illness) were


Surgery_Schwartz

Surgery_Schwartz. was completely dependent on the robustness of their methodology for case-matching because sicker patients (i.e., those at greater risk of mortality based upon the severity of their illness) were presumably more likely to undergo pulmonary artery catheter-ization. Accordingly, the authors used sophisticated statistical methods for generating a cohort of study (i.e., PAC) patients, each one having a paired control matched carefully for severity of illness. Connors and associates concluded that placement of a pulmonary artery catheter during the first 24 hours of stay in an ICU is associated with a significant increase in the risk of mortality, even when statistical methods are used to account for severity of illness.A number of prospective, randomized controlled trials of pulmonary artery catheterization are summarized in Table 13-2. The study by Pearson and associates was underpowered with only 226 patients enrolled.22 In addition, the attending anes-thesiologists were permitted to


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Surgery_Schwartz. catheterization are summarized in Table 13-2. The study by Pearson and associates was underpowered with only 226 patients enrolled.22 In addition, the attending anes-thesiologists were permitted to exclude patients from the CVP group at their discretion; thus randomization was compromised. The study by Tuman and coworkers was large (1094 patients were enrolled), but different anesthesiologists were assigned to the different groups.23 Furthermore, 39 patients in the CVP group underwent placement of a PAC because of hemodynamic complications. All of the individual single-institution studies of vascular surgery patients were relatively underpowered, and all excluded at least certain categories of patients (e.g., those with a history of recent myocardial infarction).24,25In the largest randomized controlled trial of the PAC, Sandham and associates randomized nearly 2000 American Society of Anesthesiologists (ASA) classes III and IV patients undergoing major thoracic, abdominal, or


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Surgery_Schwartz. randomized controlled trial of the PAC, Sandham and associates randomized nearly 2000 American Society of Anesthesiologists (ASA) classes III and IV patients undergoing major thoracic, abdominal, or orthopedic surgery to placement of a PAC or CVP catheter.26 In the patients assigned to receive a PAC, physiologic goal-directed therapy was imple-mented by protocol. There were no differences in mortality at 30 days, 6 months, or 12 months between the two groups, and ICU length of stay was similar. There was a significantly higher rate of pulmonary emboli in the PAC group (0.9% vs. 0%). This study has been criticized because most of the patients enrolled were not in the highest risk category.In the “PAC-Man” trial, a multicenter, randomized trial in 65 UK hospitals, over 1000 ICU patients were managed with or without a PAC.27 The specifics of the clinical management were then left up to the treating clinicians. There was no dif-ference in hospital mortality between the 2 groups (with PAC


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Surgery_Schwartz. managed with or without a PAC.27 The specifics of the clinical management were then left up to the treating clinicians. There was no dif-ference in hospital mortality between the 2 groups (with PAC 68% vs. without PAC 66%, P = 0.39). However, a 9.5% com-plication rate was associated with the insertion or use of the PAC, although none of these complications were fatal. Clearly, these were critically ill patients, as noted by the high hospital mortality rates. Supporters of the PAC may cite methodology problems with this study, such as loose inclusion criteria and the lack of a defined treatment protocol.Brunicardi_Ch13_p0433-p0452.indd 44022/02/19 2:21 PM 441PHYSIOLOGIC MONITORING OF THE SURGICAL PATIENTCHAPTER 13Table 13-2Summary of randomized, prospective clinical trials comparing pulmonary artery catheter (PAC) with central venous pressure (CVP) monitoringAUTHORSTUDY POPULATIONGROUPSOUTCOMESSTRENGTHS/WEAKNESSESPearson et al22“Low risk” patients undergoing cardiac or vascular


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Surgery_Schwartz. pulmonary artery catheter (PAC) with central venous pressure (CVP) monitoringAUTHORSTUDY POPULATIONGROUPSOUTCOMESSTRENGTHS/WEAKNESSESPearson et al22“Low risk” patients undergoing cardiac or vascular surgeryCVP catheter (group 1); PAC (group 2); PAC with continuous Sv–O2 readout (group 3)No differences among groups for mortality or length of ICU stay; significant differences in costs (group 1 < group 2 < group 3)Underpowered (266 total patients enrolled); compromised randomization protocolsTuman et al23Cardiac surgical patientsPAC; CVPNo differences between groups for mortality, length of ICU stay, or significant noncardiac complicationsLarge trial (1094 patients); different anesthesiologists for different groupsBender et al24Vascular surgery patientsPAC; CVPNo differences between groups for mortality, length of ICU stay, or length of hospital stayRelatively underpoweredValentine et al25Aortic surgery patientsPAC + hemodynamic optimization in ICU night before surgery; CVPNo


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Surgery_Schwartz. groups for mortality, length of ICU stay, or length of hospital stayRelatively underpoweredValentine et al25Aortic surgery patientsPAC + hemodynamic optimization in ICU night before surgery; CVPNo difference between groups for mortality or length of ICU stay; significantly higher incidence of postoperative complications in PAC groupRelatively underpoweredSandham et al26“High risk” major surgeryPAC; CVPNo differences between groups for mortality, length of ICU stay; increased incidence of pulmonary embolism in PAC groupLargest RCT of PAC utilization; commonly criticized for smaller number of highest risk category patientsHarvey S et al27PAC-Man TrialMedical and surgical ICU patientsPAC vs no PAC, with option for alternative CO measuring device in non-PAC groupNo difference in hospital mortality between the 2 groups, increased incidence of complications in the PAC groupLoose inclusion criteria with lack of a defined treatment protocol for use of PAC dataBinanay et al29ESCAPE


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Surgery_Schwartz. mortality between the 2 groups, increased incidence of complications in the PAC groupLoose inclusion criteria with lack of a defined treatment protocol for use of PAC dataBinanay et al29ESCAPE TrialPatients with CHFPAC vs no PACNo difference in hospital mortality between the groups, increased incidence of adverse events in the PAC groupNo formal treatment protocol for PAC-driven therapyWheeler et al30FACTT TrialPatients with ALIPAC vs CVC with a fluid and inotropic management protocolNo difference in ICU or hospital mortality, or incidence of organ failure between the groups; increased incidence of adverse events in the PAC group ALI = acute lung injury; CHF = congestive heart failure; CO = cardiac output; CVC = central venous catheter; ICU = intensive care unit; PAC = pulmonary artery catheter; Sv–O2 = fractional mixed venous (pulmonary artery) hemoglobin saturation.A meta-analysis of 13 randomized studies of the PAC that included over 5000 patients was published in 2005.28 A broad


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Surgery_Schwartz. Sv–O2 = fractional mixed venous (pulmonary artery) hemoglobin saturation.A meta-analysis of 13 randomized studies of the PAC that included over 5000 patients was published in 2005.28 A broad spectrum of critically ill patients was included in these hetero-geneous trials, and the hemodynamic goals and treatment strate-gies varied. While the use of the PAC was associated with an increased use of inotropes and vasodilators, there were no differ-ences in mortality or hospital length of stay between the patients managed with a PAC and those managed without a PAC.The ESCAPE trial (which was one of the studies included in the previous meta-analysis)29 evaluated 433 patients with severe or recurrent congestive heart failure (CHF) admitted to the ICU. Patients were randomized to management by clinical assessment and a PAC or clinical assessment without a PAC. The goal in both groups was resolution of CHF, with addi-tional PAC targets of a pulmonary capillary occlusion pressure of 15 mmHg and a


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Surgery_Schwartz. assessment and a PAC or clinical assessment without a PAC. The goal in both groups was resolution of CHF, with addi-tional PAC targets of a pulmonary capillary occlusion pressure of 15 mmHg and a right atrial pressure of 8 mmHg. There was no formal treatment protocol, but inotropic support was dis-couraged. Substantial reduction in symptoms, jugular venous pressure, and edema was noted in both groups. There was no significant difference in the primary end point of days alive and out of the hospital during the first 6 months, or hospital mortality (PAC 10% vs without PAC 9%). Adverse events Brunicardi_Ch13_p0433-p0452.indd 44122/02/19 2:21 PM 442BASIC CONSIDERATIONSPART Iwere more common among patients in the PAC group (21.9% vs 11.5%; P = 0.04).Finally, the Fluids and Catheters Treatment Trial (FACTT) conducted by the Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network was published in 2006.30 The risks and benefits of PAC compared with central venous catheters


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Surgery_Schwartz. Trial (FACTT) conducted by the Acute Respiratory Distress Syndrome (ARDS) Clinical Trials Network was published in 2006.30 The risks and benefits of PAC compared with central venous catheters (CVC) were evaluated in 1000 patients with acute lung injury. Patients were randomly assigned to receive either a PAC or a CVC to guide management for 7 days via an explicit protocol. Patients also were randomly assigned to a conservative or liberal fluid strategy in a 2 × 2 factorial design (outcomes based on the fluid management strategy were published separately). Mortality dur-ing the first 60 days was similar in the PAC and CVC groups (27% and 26%, respectively; P = .69). The duration of mechani-cal ventilation and ICU length of stay also were not influenced by the type of catheter used. The type of catheter employed did not affect the incidence of shock, respiratory or renal failure, ventilator settings, or requirement for hemodialysis or vaso-pressors. There was a 1% rate of crossover from


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Surgery_Schwartz. of catheter employed did not affect the incidence of shock, respiratory or renal failure, ventilator settings, or requirement for hemodialysis or vaso-pressors. There was a 1% rate of crossover from CVC-guided therapy to PAC-guided therapy. The catheter used did not affect the administration of fluids or diuretics, and the fluid balance was similar in the two groups. The PAC group had approxi-mately twice as many catheter-related adverse events (mainly arrhythmias).Few subjects in critical care medicine have historically gen-erated more emotional responses among experts in the field than the use of the PAC. As these studies demonstrate, it is not possible to show that therapy directed by use of the PAC saves lives when it is evaluated in a large population of patients. Certainly, given the available evidence, routine use of the PAC cannot be justified. Whether selective use of the device in a few relatively uncommon clinical situations is warranted or valuable remains a controversial


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Surgery_Schwartz. available evidence, routine use of the PAC cannot be justified. Whether selective use of the device in a few relatively uncommon clinical situations is warranted or valuable remains a controversial issue. Consequently, a marked decline in the use of the PAC from 5.66 per 1000 medical admissions in 1993 to 1.99 per 1000 medical admissions in 2004 has been seen.31 Based upon the results and exclusion criteria in these pro-spective randomized trials, reasonable criteria for perioperative monitoring without use of a PAC are presented in Table 13-3.One of the reasons for using a PAC to monitor critically ill patients is to optimize cardiac output and systemic oxygen delivery. Defining what constitutes the optimum cardiac out-put, however, has proven to be difficult. A number of random-ized trials evaluating the effect on outcome of goal-directed as compared to conventional hemodynamic resuscitation have 2Table 13-3Suggested criteria for perioperative monitoring without use of a pulmonary


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Surgery_Schwartz. evaluating the effect on outcome of goal-directed as compared to conventional hemodynamic resuscitation have 2Table 13-3Suggested criteria for perioperative monitoring without use of a pulmonary artery catheter in patients undergoing cardiac or major vascular surgical proceduresNo anticipated need for suprarenal or supraceliac aortic cross-clampingNo history of myocardial infarction during 3 months prior to operationNo history of poorly compensated congestive heart failureNo history of coronary artery bypass graft surgery during 6 weeks prior to operationNo history of ongoing symptomatic mitral or aortic valvular heart diseaseNo history of ongoing unstable angina pectorisbeen published. Some studies provide support for the notion that interventions designed to achieve supraphysiologic goals for DO2, VO2, and QT improve outcome.32,33 However, other pub-lished studies do not support this view, and a meta-analysis con-cluded that interventions designed to achieve supraphysiologic goals


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Surgery_Schwartz. for DO2, VO2, and QT improve outcome.32,33 However, other pub-lished studies do not support this view, and a meta-analysis con-cluded that interventions designed to achieve supraphysiologic goals for oxygen transport do not significantly reduce mortality rates in critically ill patients.34,35 At this time, supraphysiologic resuscitation of patients in shock cannot be endorsed.There is no simple explanation for the apparent lack of effectiveness of pulmonary artery catheterization, although sev-eral concurrent possibilities exist. First, even though bedside pulmonary artery catheterization is quite safe, the procedure is associated with a finite incidence of serious complications, including ventricular arrhythmias, catheter-related sepsis, cen-tral venous thrombosis, pulmonary arterial perforation, and pul-monary embolism.26 The adverse effects of these complications on outcome may equal or even outweigh any benefits associated with using a PAC to guide therapy. Second, the data


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Surgery_Schwartz. perforation, and pul-monary embolism.26 The adverse effects of these complications on outcome may equal or even outweigh any benefits associated with using a PAC to guide therapy. Second, the data generated by the PAC may be inaccurate, leading to inappropriate thera-peutic interventions. Third, the measurements, even if accurate, are often misinterpreted.36 Furthermore, the current state of understanding is primitive when it comes to deciding what is the best management for certain hemodynamic disturbances, par-ticularly those associated with sepsis or septic shock. Taking all of this into consideration, it may be that interventions prompted by measurements obtained with a PAC are actually harmful to patients. As a result, the marginal benefit now available by placing a PAC may be quite small. Less invasive modalities are available that may provide clinically useful hemodynamic information.It may be true that aggressive hemodynamic resusci-tation of patients, guided by various forms


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Surgery_Schwartz. small. Less invasive modalities are available that may provide clinically useful hemodynamic information.It may be true that aggressive hemodynamic resusci-tation of patients, guided by various forms of monitoring, is valuable only during certain critical periods, such as the first few hours after presentation with septic shock or during surgery. For example, Rivers and colleagues reported that survival of patients with septic shock is significantly improved when resus-citation in the emergency department is guided by a protocol that seeks to keep ScvO2 greater than 70%.19 Similarly, a study using an ultrasound-based device (see “Doppler Ultrasonogra-phy”) to assess cardiac filling and SV showed that maximizing SV intraoperatively results in fewer postoperative complications and shorter hospital length of stay.37MINIMALLY INVASIVE ALTERNATIVES TO THE PULMONARY ARTERY CATHETERBecause of the cost, risks, and questionable benefit associated with bedside pulmonary artery catheterization,


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Surgery_Schwartz. length of stay.37MINIMALLY INVASIVE ALTERNATIVES TO THE PULMONARY ARTERY CATHETERBecause of the cost, risks, and questionable benefit associated with bedside pulmonary artery catheterization, there has been interest in the development of practical means for less invasive monitoring of hemodynamic parameters. Several approaches have been developed that have achieved variable degrees of suc-cess. None of these methods render the standard thermodilution technique of the pulmonary artery catheter obsolete. However, these strategies may contribute to improvements in the hemody-namic monitoring of critically ill patients.Transpulmonary ThermodilutionIn the standard PAC thermodilution technique, measurements rely on the detection of temperature changes in a relatively small area from the injection port to the thermistor on the same catheter. In contrast, the transpulmonary thermodilution (TPTD) technique measures temperature changes from cold Brunicardi_Ch13_p0433-p0452.indd 44222/02/19


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Surgery_Schwartz. port to the thermistor on the same catheter. In contrast, the transpulmonary thermodilution (TPTD) technique measures temperature changes from cold Brunicardi_Ch13_p0433-p0452.indd 44222/02/19 2:21 PM 443PHYSIOLOGIC MONITORING OF THE SURGICAL PATIENTCHAPTER 13bolus solution injected centrally, then measured using an arte-rial thermistor on a special arterial line, generally placed in the femoral artery. Both standard PAC thermodilution and TPTD make use of the Stewart-Hamilton equation to subsequently cal-culate cardiac output. Studies have demonstrated that this tech-nique provides comparable estimates of cardiac output when compared to routine PAC thermodilution and can accurately detect changes in cardiac output as small as 12%.38 However, due to the large blood circuit between the central injection point and the thermistor, data can be challenging to interpret in cer-tain pathophysiologic conditions (e.g., in pulmonary edema, as excess lung water serves as a temperature sink).


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Surgery_Schwartz. central injection point and the thermistor, data can be challenging to interpret in cer-tain pathophysiologic conditions (e.g., in pulmonary edema, as excess lung water serves as a temperature sink). On the other hand, thoughtful application of TPTD data allows clinicians access to several additional variables that the traditional PAC does not provide, such as estimation of the global end-diastolic volume (GEDV) and the extravascular lung water volume (EVLW).38 While these variables are of scientific interest, they are not yet in wide clinical use, and further studies are required to determine their utility. However, TPTD does currently play a prominent in the real-time calibration of pulse contour analysis, described in greater detail later in this chapter.Doppler UltrasonographyWhen ultrasonic sound waves are reflected by moving erythro-cytes in the bloodstream, the frequency of the reflected signal is increased or decreased, depending on whether the cells are mov-ing toward or away


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Surgery_Schwartz. sound waves are reflected by moving erythro-cytes in the bloodstream, the frequency of the reflected signal is increased or decreased, depending on whether the cells are mov-ing toward or away from the ultrasonic source. This change in frequency is called the Doppler shift, and its magnitude is deter-mined by the velocity of the moving red blood cells. Therefore, measurements of the Doppler shift can be used to calculate red blood cell velocity. With knowledge of both the cross-sectional area of a vessel and the mean red blood cell velocity of the blood flowing through it, one can calculate blood flow rate. If the ves-sel in question is the aorta, then QT can be calculated as:QT = HR × A × ∫ V(t)dtwhere A is the cross-sectional area of the aorta and ∫V(t)dt is the red blood cell velocity integrated over the cardiac cycle.Two approaches have been developed for using Doppler ultrasonography to estimate QT. The first approach uses an ultrasonic transducer, which is manually positioned in


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Surgery_Schwartz. over the cardiac cycle.Two approaches have been developed for using Doppler ultrasonography to estimate QT. The first approach uses an ultrasonic transducer, which is manually positioned in the suprasternal notch and focused on the root of the aorta. Aortic cross-sectional area can be estimated using a nomogram, which factors in age, height, and weight, back-calculated if an indepen-dent measure of QT is available, or by using two-dimensional transthoracic or transesophageal ultrasonography. While this approach is completely noninvasive, it requires a highly-skilled operator in order to obtain meaningful results and is labor-intensive. Moreover, unless QT measured using thermodilution is used to back-calculate aortic diameter, accuracy using the suprasternal notch approach is not acceptable. Accordingly, the method is useful only for obtaining very intermittent estimates of QT, and it has not been widely adopted by clinicians.A more promising, albeit more invasive, approach has been


Surgery_Schwartz

Surgery_Schwartz. Accordingly, the method is useful only for obtaining very intermittent estimates of QT, and it has not been widely adopted by clinicians.A more promising, albeit more invasive, approach has been introduced. In this method blood flow velocity is con-tinuously monitored in the descending thoracic aorta using a continuous-wave Doppler transducer introduced into the esoph-agus. The probe is connected to a monitor which continuously displays the blood flow velocity profile in the descending aorta as well as the calculated QT. In order to maximize the accuracy of the device, the probe position must be adjusted to obtain the peak velocity in the aorta. In order to transform blood flow in the descending aorta into QT, a correction factor is applied that is based on the assumption that only 70% of the flow at the root of the aorta is still present in the descending thoracic aorta. Aortic cross-sectional area is estimated using a nomogram based on the patient’s age, weight, and height. Results


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Surgery_Schwartz. the flow at the root of the aorta is still present in the descending thoracic aorta. Aortic cross-sectional area is estimated using a nomogram based on the patient’s age, weight, and height. Results using these methods appear to be reasonably accurate across a broad spectrum of patients. A meta-analysis of the available data shows a good correlation between cardiac output estimates obtained by trans-esophageal Doppler and PAC in critically ill patients.39 The ultrasonic device also calculates a derived parameter termed flow time corrected (FTc), which is the systolic flow time in the descending aorta corrected for heart rate. FTc is a function of preload, contractility, and vascular input impedance. Although it is not a pure measure of preload, Doppler-based estimates of SV and FTc have been used successfully to guide volume resuscitation in high-risk surgical patients undergoing major operations.37Impedance CardiographyThe impedance to flow of alternating electrical current in


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Surgery_Schwartz. have been used successfully to guide volume resuscitation in high-risk surgical patients undergoing major operations.37Impedance CardiographyThe impedance to flow of alternating electrical current in regions of the body is commonly called bioimpedance. In the thorax, changes in the volume and velocity of blood in the tho-racic aorta lead to detectable changes in bioimpedance. The first derivative of the oscillating component of thoracic bio-impedance (dZ/dt) is linearly related to aortic blood flow. On the basis of this relationship, empirically derived formulas have been developed to estimate SV, and subsequently QT, nonin-vasively. This methodology is called impedance cardiography. The approach is attractive because it is noninvasive, provides a continuous readout of QT, and does not require extensive train-ing. Despite these advantages, measurements of QT obtained by impedance cardiography are not sufficiently reliable to be used for clinical decision making and have poor


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Surgery_Schwartz. not require extensive train-ing. Despite these advantages, measurements of QT obtained by impedance cardiography are not sufficiently reliable to be used for clinical decision making and have poor correlation with thermodilution.40Because of the limitations of bioimpedance devices, a newer approach for processing the impedance signal was devel-oped and commercialized. This approach is based on the recog-nition that the impedance signal has two components: amplitude and phase. Whereas the amplitude of the thoracic impedance signal is determined by all of the components of the thoracic cavity (bone, blood, muscle, and other soft tissues), phase shifts are determined entirely by pulsatile flow. The vast majority of pulsatile flow is related to blood moving within the aorta. There-fore, the “bioreactance” signal correlates closely with aortic flow, and cardiac output determined using this approach agrees closely with cardiac output measured using conventional indica-tor dilution


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Surgery_Schwartz. the “bioreactance” signal correlates closely with aortic flow, and cardiac output determined using this approach agrees closely with cardiac output measured using conventional indica-tor dilution techniques.41Pulse Contour AnalysisAnother method for determining cardiac output is an approach called pulse contour analysis for estimating SV on a beat-to-beat basis. The mechanical properties of the arterial tree and SV determine the shape of the arterial pulse waveform. The pulse contour method of estimating QT uses the arterial pressure waveform as an input for a model of the systemic circulation in order to determine beat-to-beat flow through the circulatory system. The parameters of resistance, compliance, and imped-ance are initially estimated based on the patient’s age and sex and can be subsequently refined by using a reference standard measurement of QT. The reference standard estimation of QT is obtained periodically using the indicator dilution approach by injecting the indicator


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Surgery_Schwartz. subsequently refined by using a reference standard measurement of QT. The reference standard estimation of QT is obtained periodically using the indicator dilution approach by injecting the indicator into a central venous catheter and Brunicardi_Ch13_p0433-p0452.indd 44322/02/19 2:21 PM 444BASIC CONSIDERATIONSPART Idetecting the transient increase in indicator concentration in the blood using an arterial catheter. In one commercially available embodiment of this approach, the lithium ion (Li+) is the indi-cator used for the periodic calibrations of the device. The lith-ium carbonate indicator can be injected into a peripheral vein, and the doses do not exert pharmacologically relevant effects in adult patients. The Li+ indicator dilution method has shown to be at least as reliable as other thermodilution methods over a broad range of CO in a variety of patients.41 In another com-mercially available system, a conventional bolus of cold fluid is used as the indicator for


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Surgery_Schwartz. as other thermodilution methods over a broad range of CO in a variety of patients.41 In another com-mercially available system, a conventional bolus of cold fluid is used as the indicator for calibration, via TPTD approaches as described previously. When the pulse contour analysis is com-bined with intermittent TPTD in this fashion, the continuous data provided by contour analysis is more precise than TPTD alone.38Measurements of QT based on pulse contour monitoring using these two approaches are comparable in accuracy to stan-dard pulmonary artery catheter (PAC)-thermodilution methods, but they are less invasive because transcardiac catheterization is not needed.42 Using online pressure waveform analysis, the computerized algorithms can calculate SV, QT, SVR, and an estimate of myocardial contractility, the rate of rise of the arte-rial systolic pressure (dP/dT). The use of pulse contour analy-sis has been applied using noninvasive photoplethysmographic measurements of arterial


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Surgery_Schwartz. contractility, the rate of rise of the arte-rial systolic pressure (dP/dT). The use of pulse contour analy-sis has been applied using noninvasive photoplethysmographic measurements of arterial pressure. However, the accuracy of this technique has been questioned, and its clinical utility remains to be determined.43One commercially available device that can be used for estimating cardiac output does not require external calibration. Instead, the relationship between pulse pressure and stroke vol-ume is determined using a proprietary algorithm that uses bio-metric data, such as age, gender and height, as inputs. Although this methodology is gaining fairly wide acceptance in critical care medicine, reported accuracy (in comparison to “gold stan-dard” approaches) is not very good.41Partial Carbon Dioxide RebreathingPartial carbon dioxide (CO2) rebreathing uses the Fick prin-ciple to estimate QT noninvasively. By intermittently altering the dead space within the ventilator circuit via a


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Surgery_Schwartz. Carbon Dioxide RebreathingPartial carbon dioxide (CO2) rebreathing uses the Fick prin-ciple to estimate QT noninvasively. By intermittently altering the dead space within the ventilator circuit via a rebreathing valve, changes in CO2 production (VCO2) and end-tidal CO2 (ETCO2) are used to determine cardiac output using a modified Fick equation:Q=VETTCOCO22˜˜Commercially available devices use this Fick principle to cal-culate QT using intermittent partial CO2 rebreathing through a disposable rebreathing loop. These devices consist of a CO2 sen-sor based on infrared light absorption, an airflow sensor, and a pulse oximeter. Changes in intrapulmonary shunt and hemody-namic instability impair the accuracy of QT estimated by partial CO2 rebreathing. Continuous inline pulse oximetry and inspired fraction of inspired O2 (Fio2) are used to estimate shunt fraction to correct QT.Some studies of the partial CO2 rebreathing approach sug-gest that this technique is not as accurate as


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Surgery_Schwartz. and inspired fraction of inspired O2 (Fio2) are used to estimate shunt fraction to correct QT.Some studies of the partial CO2 rebreathing approach sug-gest that this technique is not as accurate as thermodilution, the gold standard for measuring QT.42,44 However, other studies sug-gest that the partial CO2 rebreathing method for determination of QT compares favorably to measurements made using a PAC in critically ill patients.45Transesophageal EchocardiographyTransesophageal echocardiography (TEE) has made the transi-tion from operating room to intensive care unit. TEE requires that the patient be sedated and usually intubated for airway pro-tection. Using this powerful technology, global assessments of LV and RV function can be made, including determinations of ventricular volume, EF, and QT. Segmental wall motion abnor-malities, pericardial effusions, and tamponade can be readily identified with TEE. Doppler techniques allow estimation of atrial filling pressures. The technique is


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Surgery_Schwartz. QT. Segmental wall motion abnor-malities, pericardial effusions, and tamponade can be readily identified with TEE. Doppler techniques allow estimation of atrial filling pressures. The technique is somewhat cumbersome and requires considerable training and skill in order to obtain reliable results. Recently, a TEE probe has been introduced into practice that is small enough in diameter that it can be left in place for as long as 72 hours. While only limited data are cur-rently available with this probe, it seems like it will be a useful cardiac monitoring tool for use in selected, complex patients.Assessing Preload ResponsivenessAlthough pulse contour analysis or partial CO2 rebreathing may be able to provide estimates of SV and QT, these approaches alone can offer little or no information about the adequacy of preload. Thus, if QT is low, some other means must be employed to estimate preload. Many clinicians assess the adequacy of car-diac preload by determining CVP or PAOP. However,


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Surgery_Schwartz. about the adequacy of preload. Thus, if QT is low, some other means must be employed to estimate preload. Many clinicians assess the adequacy of car-diac preload by determining CVP or PAOP. However, neither CVP nor PAOP correlate well with the true parameter of inter-est, left ventricular end-diastolic volume (LVEDV).46 Extremely high or low CVP or PAOP results are informative, but readings in a large middle zone (i.e., 5 to 20 mmHg) are less useful. Fur-thermore, changes in CVP or PAOP fail to correlate well with changes in stroke volume.47,48 Echocardiography can be used to estimate LVEDV, but this approach is dependent on the skill and training of the individual using it, and isolated measure-ments of LVEDV fail to predict the hemodynamic response to alterations in preload.49When intrathoracic pressure increases during the appli-cation of positive airway pressure in mechanically ventilated patients, venous return decreases, and as a consequence, left ventricular stroke volume


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Surgery_Schwartz. intrathoracic pressure increases during the appli-cation of positive airway pressure in mechanically ventilated patients, venous return decreases, and as a consequence, left ventricular stroke volume (LVSV) also decreases. Therefore, pulse pressure variation (PPV) during a positive pressure episode can be used to predict the responsiveness of cardiac output to changes in preload.50,51 PPV is defined as the differ-ence between the maximal pulse pressure and the minimum pulse pressure divided by the average of these two pressures (Fig. 13-4). This approach has validated this by comparing PPV, CVP, PAOP, and systolic pressure variation as predictors of pre-load responsiveness in a cohort of critically ill patients. Patients were classified as being “preload responsive” if their cardiac index increased by at least 15% after rapid infusion of a standard volume of intravenous fluid.52 Receiver-operating characteristic (ROC) curves demonstrated that PPV was the best predictor of preload


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Surgery_Schwartz. increased by at least 15% after rapid infusion of a standard volume of intravenous fluid.52 Receiver-operating characteristic (ROC) curves demonstrated that PPV was the best predictor of preload responsiveness. Although atrial arrhythmias can inter-fere with the usefulness of this technique, PPV remains a useful approach for assessing preload responsiveness in most patients because of its simplicity and reliability.49Near-Infrared Spectroscopic Measurement of Tissue Hemoglobin Oxygen SaturationNear-infrared spectroscopy (NIRS) allows continuous, nonin-vasive measurement of tissue hemoglobin oxygen saturation (StO2) using near-infrared wave lengths of light (700–1000 nm). This technology is based on Beer’s law, which states that the transmission of light through a solution with a dissolved Brunicardi_Ch13_p0433-p0452.indd 44422/02/19 2:21 PM 445PHYSIOLOGIC MONITORING OF THE SURGICAL PATIENTCHAPTER 13Figure 13-4. Calculation of pulse pressure variation as it would appear on bedside


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Surgery_Schwartz. Brunicardi_Ch13_p0433-p0452.indd 44422/02/19 2:21 PM 445PHYSIOLOGIC MONITORING OF THE SURGICAL PATIENTCHAPTER 13Figure 13-4. Calculation of pulse pressure variation as it would appear on bedside monitor. This provides a helpful and rapid assessment of fluid responsiveness in the critically ill mechanically ventilated patient.PPmax + PPmin2PPV (%) =PPmax – PPmin× 100InspirationArterial blood pressure (mmHg)ExpirationInspirationInspirationExpirationTimePPminPPmaxsolute decreases exponentially as the concentration of the sol-ute increases. In mammalian tissue, three compounds change their absorption pattern when oxygenated: cytochrome aa3, myoglobin, and hemoglobin. Because of the distinct absorption spectra of oxyhemoglobin and deoxyhemoglobin, Beer’s law can be used to detect their relative concentrations within tissue. Thus, the relative concentrations of the types of hemoglobin can be determined by measuring the change in light inten-sity as it passes through the tissue. Since


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Surgery_Schwartz. concentrations within tissue. Thus, the relative concentrations of the types of hemoglobin can be determined by measuring the change in light inten-sity as it passes through the tissue. Since about 20% of blood volume is intra-arterial and the StO2 measurements are taken without regard to systole or diastole, spectroscopic measure-ments are primarily indicative of the venous oxyhemoglobin concentration.NIRS has been evaluated to assess the severity of traumatic shock in animal models and in trauma patients. Studies have shown that peripheral muscle StO2, as determined by NIRS, is as accurate as other endpoints of resuscitation (i.e., base deficit, mixed venous oxygen saturation) in a porcine model of hemor-rhagic shock.53 Continuously measured StO2 has been evaluated in blunt trauma patients as a predictor of the development of multiple organ dysfunction syndrome (MODS) and mortality.54 383 patients were prospectively studied at seven level I trauma centers. StO2 was monitored for 24


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Surgery_Schwartz. as a predictor of the development of multiple organ dysfunction syndrome (MODS) and mortality.54 383 patients were prospectively studied at seven level I trauma centers. StO2 was monitored for 24 hours after admission along with vital signs and other endpoints of resuscitation such as base deficit (BD). Minimum StO2 (using a minimum StO2 ≤75% as a cutoff) had a similar sensitivity and specificity in predicting the development of MODS as BD ≥6 mEq/L. StO2 and BD were also comparable in predicting mortality. Thus, NIRS-derived muscle StO2 measurements perform similarly to BD in identify-ing poor perfusion and predicting the development of MODS or death after severe torso trauma, yet have the additional advan-tages of being continuous and noninvasive. Ongoing prospec-tive studies will help determine the clinical utility of continuous monitoring of StO2 in clinical scenarios such as trauma, hemor-rhagic shock, sepsis, etc.RESPIRATORY MONITORINGThe ability to monitor various parameters of


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Surgery_Schwartz. the clinical utility of continuous monitoring of StO2 in clinical scenarios such as trauma, hemor-rhagic shock, sepsis, etc.RESPIRATORY MONITORINGThe ability to monitor various parameters of respiratory func-tion is of utmost importance in critically ill patients. Many of these patients require mechanical ventilation. Monitoring of their respiratory physiology is necessary to assess the adequacy of oxygenation and ventilation, guide weaning and liberation from mechanical ventilation, and detect adverse events associ-ated with respiratory failure and mechanical ventilation. These parameters include gas exchange, neuromuscular activity, respi-ratory mechanics, and patient effort.Arterial Blood GasesBlood gas analysis may provide useful information when caring for patients with respiratory failure. However, even in the absence of respiratory failure or the need for mechanical ventilation, blood gas determinations also can be valuable to detect alterations in acid-base balance due to low


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Surgery_Schwartz. However, even in the absence of respiratory failure or the need for mechanical ventilation, blood gas determinations also can be valuable to detect alterations in acid-base balance due to low QT, sepsis, renal failure, severe trauma, medication or drug overdose, or altered mental status. Arterial blood can be analyzed for pH, Po2, Pco2, HCO3– con-centration and calculated base deficit. When indicated, carboxy-hemoglobin and methemoglobin levels also can be measured. In recent years, efforts have been made to decrease the unnecessary use of arterial blood gas analysis. Serial arterial blood gas deter-minations are not necessary for routine weaning from mechanical ventilation in the majority of postoperative patients.Most bedside blood gas analyses still involve removal of an aliquot of blood from the patient, although continuous bedside arterial blood gas determinations are now possible without sam-pling via an indwelling arterial catheter that contains a biosensor. In studies


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Surgery_Schwartz. of blood from the patient, although continuous bedside arterial blood gas determinations are now possible without sam-pling via an indwelling arterial catheter that contains a biosensor. In studies comparing the accuracy of continuous arterial blood gas and pH monitoring with a conventional laboratory blood gas analyzer, excellent agreement between the two methods has been demonstrated.55 Continuous monitoring can reduce the volume of blood loss due to phlebotomy and dramatically decrease the time necessary to obtain blood gas results. Continuous monitor-ing, however, is expensive and is not widely employed.Determinants of Oxygen DeliveryThe primary goal of the cardiovascular and respiratory systems is to deliver oxygenated blood to the tissues. DO2 is dependent to a greater degree on the oxygen saturation of hemoglobin (Hgb) in arterial blood (Sao2) than on the partial pressure of oxygen in arterial blood (Pao2). DO2 also is dependent on QT and Hgb. As discussed earlier and


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Surgery_Schwartz. on the oxygen saturation of hemoglobin (Hgb) in arterial blood (Sao2) than on the partial pressure of oxygen in arterial blood (Pao2). DO2 also is dependent on QT and Hgb. As discussed earlier and illustrated mathematically by previous equations, the dissolved oxygen in blood makes only a negligible contribution to DO2. Sao2 in mechanically venti-lated patients depends on the mean airway pressure, the frac-tion of inspired oxygen (Fio2), and SvO2. Thus, when Sao2 is low, the clinician has only a limited number of ways to improve this parameter. The clinician can increase mean airway pres-sure by increasing positive-end expiratory pressure (PEEP) or inspiratory time. Fio2 can be increased to a maximum of 1.0 by decreasing the amount of room air mixed with the oxygen sup-plied to the ventilator. SvO2 can be increased by increasing Hgb Brunicardi_Ch13_p0433-p0452.indd 44522/02/19 2:21 PM 446BASIC CONSIDERATIONSPART Ior QT or decreasing oxygen utilization (e.g., by administering a


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Surgery_Schwartz. SvO2 can be increased by increasing Hgb Brunicardi_Ch13_p0433-p0452.indd 44522/02/19 2:21 PM 446BASIC CONSIDERATIONSPART Ior QT or decreasing oxygen utilization (e.g., by administering a muscle relaxant and sedation).Peak and Plateau Airway PressureAirway pressures are routinely monitored in mechanically ven-tilated patients. The peak airway pressure measured at the end of inspiration (Ppeak) is a function of the tidal volume, the resistance of the airways, lung/chest wall compliance, and peak inspiratory flow. The airway pressure measured at the end of inspiration when the inhaled volume is held in the lungs by briefly clos-ing the expiratory valve is termed the plateau airway pressure (Pplateau). As a static parameter, plateau airway pressure is indepen-dent of the airway resistance and peak airway flow and is related to the lung/chest wall compliance and delivered tidal volume. Mechanical ventilators monitor Ppeak with each breath and can be set to trigger an alarm if the


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Surgery_Schwartz. and peak airway flow and is related to the lung/chest wall compliance and delivered tidal volume. Mechanical ventilators monitor Ppeak with each breath and can be set to trigger an alarm if the Ppeak exceeds a predetermined thresh-old. Pplateau is not measured routinely with each delivered tidal vol-ume but rather is measured intermittently by setting the ventilator to close the exhalation circuit briefly at the end of inspiration and record the airway pressure when airflow is zero.If both Ppeak and Pplateau are increased (and tidal volume is not excessive), then the problem is a decrease in the compli-ance in the lung/chest wall unit. Common causes of this problem include pneumothorax, hemothorax, lobar atelectasis, pulmo-nary edema, pneumonia, acute respiratory distress syndrome (ARDS), active contraction of the chest wall or diaphragmatic muscles, abdominal distention, and intrinsic PEEP, such as occurs in patients with bronchospasm and insufficient expira-tory times. When Ppeak is


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Surgery_Schwartz. active contraction of the chest wall or diaphragmatic muscles, abdominal distention, and intrinsic PEEP, such as occurs in patients with bronchospasm and insufficient expira-tory times. When Ppeak is increased but Pplateau is relatively nor-mal, the primary problem is an increase in airway resistance, such as occurs with bronchospasm, use of a small-caliber endo-tracheal tube, or kinking or obstruction of the endotracheal tube. A low Ppeak also should trigger an alarm, as it suggests a discon-tinuity in the airway circuit involving the patient and the ventila-tor. These scenarios are outlined in Table 13-4.Ventilator-induced lung injury (VILI) is now an estab-lished clinical entity of great relevance to the care of critically ill patients. Excessive airway pressure and tidal volume adversely affect pulmonary and possibly systemic responses to critical illness. Subjecting the lung parenchyma to excessive pressure, known as barotrauma, can result in parenchymal lung injury, diffuse


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Surgery_Schwartz. affect pulmonary and possibly systemic responses to critical illness. Subjecting the lung parenchyma to excessive pressure, known as barotrauma, can result in parenchymal lung injury, diffuse alveolar damage similar to ARDS, and pneumothorax, and can impair venous return and therefore limit cardiac output. Lung-protective ventilation strategies have been developed to prevent the development of VILI and improve patient outcomes. Table 13-4Scenarios associated with different combinations of Ppeak and Pplateau in ventilated patientsCONDITIONPpeakPplateauDecreased compliance of the system (ARDS, abdominal distention, intrinsic PEEP)⇑⇑Increase in airway resistance (bronchospasm, endotracheal tube obstruction/kinking, or small-caliber endotracheal tube)⇑normalDisconnected circuit⇓⇓In a large, multicenter, randomized trial of patients with ARDS from a variety of etiologies, limiting plateau airway pressure to less than 30 cm H2O and tidal volume to less than 6 mL/kg of ideal body weight


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Surgery_Schwartz. multicenter, randomized trial of patients with ARDS from a variety of etiologies, limiting plateau airway pressure to less than 30 cm H2O and tidal volume to less than 6 mL/kg of ideal body weight reduced 28-day mortality by 22% relative to a ventilator strategy that used a tidal volume of 12 mL/kg.56 For this reason, monitoring of plateau pressure and using a low tidal volume strategy in patients with ARDS is now the standard of care. Recent data also suggest that a lung-protective ventila-tion strategy is associated with improved clinical outcomes in ventilated patients without ARDS.57 Importantly, this strategy also has been shown to have benefit for high-risk patients under-going general anesthesia for surgical procedures, leading to a reduced overall rate of pulmonary complications in the peri-operative period as well as a reduced length of stay following surgery.58Pulse OximetryThe pulse oximeter is a microprocessor-based device that inte-grates oximetry and plethysmography to


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Surgery_Schwartz. in the peri-operative period as well as a reduced length of stay following surgery.58Pulse OximetryThe pulse oximeter is a microprocessor-based device that inte-grates oximetry and plethysmography to provide continuous noninvasive monitoring of the oxygen saturation of arterial blood (Sao2). It is considered one of the most important and useful technologic advances in patient monitoring. Continuous, noninvasive monitoring of arterial oxygen saturation is pos-sible using light-emitting diodes and sensors placed on the skin. Pulse oximetry employs two wavelengths of light (i.e., 660 nm and 940 nm) to analyze the pulsatile component of blood flow between the light source and sensor. Because oxyhemoglobin and deoxyhemoglobin have different absorption spectra, differ-ential absorption of light at these two wavelengths can be used to calculate the fraction of oxygen saturation of hemoglobin. Under normal circumstances, the contributions of carboxyhe-moglobin and methemoglobin are minimal.


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Surgery_Schwartz. at these two wavelengths can be used to calculate the fraction of oxygen saturation of hemoglobin. Under normal circumstances, the contributions of carboxyhe-moglobin and methemoglobin are minimal. However, if car-boxyhemoglobin levels are elevated, the pulse oximeter will incorrectly interpret carboxyhemoglobin as oxyhemoglobin and the arterial saturation displayed will be falsely elevated. When the concentration of methemoglobin is markedly increased, the Sao2 will be displayed as 85%, regardless of the true arterial saturation.59 The accuracy of pulse oximetry begins to decline at Sao2 values less than 92% and tends to be unreliable for values less than 85%.60Several studies have assessed the frequency of arterial oxygen desaturation in hospitalized patients and its effect on outcome. Monitoring pulse oximetry in surgical patients is asso-ciated with a reduction in unrecognized deterioration, rescue events, and transfers to the ICU.61 Because of its clinical rel-evance, ease of


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Surgery_Schwartz. Monitoring pulse oximetry in surgical patients is asso-ciated with a reduction in unrecognized deterioration, rescue events, and transfers to the ICU.61 Because of its clinical rel-evance, ease of use, noninvasive nature, and cost-effectiveness, pulse oximetry has become a routine monitoring strategy in patients with respiratory disease, intubated patients, and those undergoing surgical intervention under sedation or general anes-thesia. Pulse oximetry is especially useful in the titration of Fio2 and PEEP for patients receiving mechanical ventilation, and during weaning from mechanical ventilation. The widespread use of pulse oximetry has decreased the need for arterial blood gas determinations in critically ill patients.Pulse CO-OximetryWhile simple pulse oximeters such as those described previ-ously are helpful for determination of the Sao2, extensions of the technology may prove valuable for determination of total hemoglobin concentration as well. Through the use of multiple


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Surgery_Schwartz. previ-ously are helpful for determination of the Sao2, extensions of the technology may prove valuable for determination of total hemoglobin concentration as well. Through the use of multiple additional wavelengths of light, clinicians can leverage the dif-ferent spectrophotometric properties of the multiple different Brunicardi_Ch13_p0433-p0452.indd 44622/02/19 2:21 PM 447PHYSIOLOGIC MONITORING OF THE SURGICAL PATIENTCHAPTER 13oxidative states of hemoglobin to get a complete readout of the total hemoglobin present in a given volume, leading to a noninvasive measurement of Hgb. These devices are referred to as pulse CO-Oximeters, as opposed to pulse oximeters, to dif-ferentiate that they are capable of measuring other hemoglobin moieties. Currently, there are two such devices that are com-mercially available for clinical use.Theoretically, the capacity to noninvasively measure Hgb concentration in real time would offer significant clinical ben-efit. These include obviating the


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Surgery_Schwartz. are com-mercially available for clinical use.Theoretically, the capacity to noninvasively measure Hgb concentration in real time would offer significant clinical ben-efit. These include obviating the need for serial blood draws, the early detection of potential postsurgical hemorrhage, and more judicious usage of blood transfusions. In practice, there are mul-tiple factors that currently affect the accuracy of the technique. Multiple studies have demonstrated that biases with noninvasive Hgb monitoring are inversely correlated with hemoglobin con-centration in a variety of monitoring scenarios; with decreasing hemoglobin values the noninvasive approaches tend to overes-timate the true Hgb.62-64 This poses a significant challenge for monitoring the critically ill patient, as frequently anemia is a common comorbid condition. On the other hand, if the continu-ous monitoring capacity afforded by these monitors can provide usable trend data, that may still provide clinical utility despite


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Surgery_Schwartz. is a common comorbid condition. On the other hand, if the continu-ous monitoring capacity afforded by these monitors can provide usable trend data, that may still provide clinical utility despite less accuracy at low hemoglobin levels. To date, there have been relatively few studies validating the trending capacity of noninvasive Hgb monitoring compared to serial blood draws, with limited agreement due to differences in analysis and study design.65 Further studies are required to evaluate the clinical utility of this potentially useful technology.CapnometryCapnometry is the measurement of carbon dioxide in the airway throughout the respiratory cycle. Capnometry is most commonly measured by infrared light absorption. CO2 absorbs infrared light at a peak wavelength of approximately 4.27 µm. Capnom-etry works by passing infrared light through a sample chamber to a detector on the opposite side. More infrared light passing through the sample chamber (i.e., less CO2) causes a larger


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Surgery_Schwartz. µm. Capnom-etry works by passing infrared light through a sample chamber to a detector on the opposite side. More infrared light passing through the sample chamber (i.e., less CO2) causes a larger sig-nal in the detector relative to the infrared light passing through a reference cell. Capnometric determination of the partial pressure of CO2 in end-tidal exhaled gas (Petco2) is used as a surrogate for the partial pressure of CO2 in arterial blood (Paco2) during mechanical ventilation. In healthy subjects, Petco2 is about 1 to 5 mmHg less than Paco2.66 Thus, Petco2 can be used to estimate Paco2 without the need for blood gas determination. However, changes in Petco2 may not correlate with changes in Paco2 dur-ing a number of pathologic conditions.Capnography allows the confirmation of endotracheal intubation and continuous assessment of ventilation, integrity of the airway, operation of the ventilator, and cardiopulmonary function. Capnometers are configured with either an inline


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Surgery_Schwartz. endotracheal intubation and continuous assessment of ventilation, integrity of the airway, operation of the ventilator, and cardiopulmonary function. Capnometers are configured with either an inline sen-sor or a sidestream sensor. The sidestream systems are lighter and easy to use, but the thin tubing that samples the gas from the ventilator circuit can become clogged with secretions or condensed water, preventing accurate measurements. The inline devices are bulky and heavier but are less likely to become clogged. Continuous monitoring with capnography has become routine during surgery under general anesthesia and for some intensive care patients. A number of situations can be promptly detected with continuous capnography. A sudden reduction in Petco2 suggests either obstruction of the sam-pling tubing with water or secretions, or a catastrophic event such as loss of the airway, airway disconnection or obstruction, ventilator malfunction, or a marked decrease in QT. If the airway


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Surgery_Schwartz. sam-pling tubing with water or secretions, or a catastrophic event such as loss of the airway, airway disconnection or obstruction, ventilator malfunction, or a marked decrease in QT. If the airway is connected and patent and the ventilator is functioning prop-erly, then a sudden decrease in Petco2 should prompt efforts to rule out cardiac arrest, massive pulmonary embolism, or cardio-genic shock. Petco2 can be persistently low during hyperven-tilation or with an increase in dead space such as occurs with pulmonary embolization (even in the absence of a change in QT). Causes of an increase in Petco2 include reduced minute ventilation or increased metabolic rate.RENAL MONITORINGUrine OutputBladder catheterization with an indwelling catheter allows the monitoring of urine output, usually recorded hourly by the nurs-ing staff. With a patent Foley catheter, urine output is a gross indicator of renal perfusion. The generally accepted normal urine output is 0.5 mL/kg per hour for adults and


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Surgery_Schwartz. hourly by the nurs-ing staff. With a patent Foley catheter, urine output is a gross indicator of renal perfusion. The generally accepted normal urine output is 0.5 mL/kg per hour for adults and 1 to 2 mL/kg per hour for neonates and infants. Oliguria may reflect inadequate renal artery perfusion due to hypotension, hypovolemia, or low QT. Low urine flow also can be a sign of intrinsic renal dysfunc-tion. It is important to recognize that normal urine output does not exclude the possibility of impending renal failure.Bladder PressureThe triad of oliguria, elevated peak airway pressures, and ele-vated intra-abdominal pressure is known as abdominal com-partment syndrome (ACS). This syndrome, first described in patients after repair of ruptured abdominal aortic aneurysm, is associated with interstitial edema of the abdominal organs, resulting in elevated intra-abdominal pressure (IAP). When IAP exceeds venous or capillary pressures, perfusion of the kidneys and other intra-abdominal


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Surgery_Schwartz. interstitial edema of the abdominal organs, resulting in elevated intra-abdominal pressure (IAP). When IAP exceeds venous or capillary pressures, perfusion of the kidneys and other intra-abdominal viscera is impaired. Oligu-ria is a cardinal sign. While the diagnosis of ACS is a clinical one, measuring IAP is useful to confirm the diagnosis. Ideally, a catheter inserted into the peritoneal cavity could measure IAP to substantiate the diagnosis. In practice, transurethral bladder pressure measurement reflects IAP and is most often used to confirm the presence of ACS. After instilling 50 to 100 mL of sterile saline into the bladder via a Foley catheter, the tubing is connected to a transducing system to measure bladder pressure in the supine position at end-expiration.Intra-abdominal hypertension is defined as an IAP ≥12 mmHg recorded on three standard measurements conducted 4 to 6 hours apart and is separated into several grades. The diag-nosis of ACS is the presence of an IAP ≥20


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Surgery_Schwartz. is defined as an IAP ≥12 mmHg recorded on three standard measurements conducted 4 to 6 hours apart and is separated into several grades. The diag-nosis of ACS is the presence of an IAP ≥20 mmHg recorded by three measurements 1 to 6 hours apart, along with new onset of organ dysfunction (Table 13-5).67-69 Less commonly, gastric or inferior vena cava pressures can be monitored with appropriate catheters to detect elevated intra-abdominal pressures.NEUROLOGIC MONITORINGIntracranial PressureBecause the brain is rigidly confined within the bony skull, cere-bral edema or mass lesions increase intracranial pressure (ICP). Monitoring of ICP is currently recommended in patients with severe traumatic brain injury (TBI), defined as a Glasgow Coma Scale (GCS) score less than or equal to 8 with an abnormal computed tomography (CT) scan, and in patients with severe TBI and a normal CT scan if two or more of the following are present: age >40 years, unilateral or bilateral motor posturing,


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Surgery_Schwartz. an abnormal computed tomography (CT) scan, and in patients with severe TBI and a normal CT scan if two or more of the following are present: age >40 years, unilateral or bilateral motor posturing, Brunicardi_Ch13_p0433-p0452.indd 44722/02/19 2:21 PM 448BASIC CONSIDERATIONSPART ITable 13-5Bladder pressure measurements in the assessment of intra-abdominal hypertension or abdominal compartment syndromeRECORDED PRESSURE (mmHg)GRADE OF IAH OR ACS5–7NormalIn the absence of organ dysfunction:12–15Grade I IAH16–20Grade II IAH21–25Grade III IAH>25Grade IV IAHIn the presence of new onset organ dysfunction:>20ACSData from Kirkpatrick AW, Roberts DJ, De Waele J, et al. Intra-abdominal hypertension and the abdominal compartment syndrome: updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome, Intensive Care Med. 2013 Jul;39(7):1190-1206.or systolic blood pressure <90 mmHg.70 ICP monitoring also is indicated in patients with


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Surgery_Schwartz. from the World Society of the Abdominal Compartment Syndrome, Intensive Care Med. 2013 Jul;39(7):1190-1206.or systolic blood pressure <90 mmHg.70 ICP monitoring also is indicated in patients with acute subarachnoid hemorrhage with coma or neurologic deterioration, intracranial hemorrhage with intraventricular blood, ischemic middle cerebral artery stroke, fulminant hepatic failure with coma and cerebral edema on CT scan, and global cerebral ischemia or anoxia with cerebral edema on CT scan. The goal of ICP monitoring is to ensure that cerebral perfusion pressure (CPP) is adequate to support perfu-sion of the brain. CPP is equal to the difference between MAP and ICP: CPP = MAP – ICP.One type of ICP measuring device, the ventriculostomy catheter, consists of a fluid-filled catheter inserted into a cere-bral ventricle and connected to an external pressure transducer. This device permits measurement of ICP but also allows drain-age of cerebrospinal fluid (CSF) as a means to lower ICP and


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Surgery_Schwartz. into a cere-bral ventricle and connected to an external pressure transducer. This device permits measurement of ICP but also allows drain-age of cerebrospinal fluid (CSF) as a means to lower ICP and sample CSF for laboratory studies. Other devices locate the pressure transducer within the central nervous system and are used only to monitor ICP. These devices can be placed in the intraventricular, parenchymal, subdural, or epidural spaces. Ventriculostomy catheters are the accepted standard for moni-toring ICP in patients with TBI due to their accuracy, ability to drain CSF, and low complication rate. The associated com-plications include infection (5%), hemorrhage (1.1%), catheter malfunction or obstruction (6.3–10.5%), and malposition with injury to cerebral tissue.71The purpose of ICP monitoring is to detect and treat abnormal elevations of ICP that may be detrimental to cere-bral perfusion and function. In TBI patients, ICP greater than 20 mmHg is associated with unfavorable


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Surgery_Schwartz. ICP monitoring is to detect and treat abnormal elevations of ICP that may be detrimental to cere-bral perfusion and function. In TBI patients, ICP greater than 20 mmHg is associated with unfavorable outcomes.72 However, few studies have shown that treatment of elevated ICP improves clinical outcomes in human trauma patients. In a randomized, controlled, double-blind trial, Eisenberg and colleagues dem-onstrated that maintaining ICP less than 25 mmHg in patients without craniectomy and less than 15 mmHg in patients with craniectomy is associated with improved outcome.73 In patients with low CPP, therapeutic strategies to correct CPP can be directed at increasing MAP or decreasing ICP. While it has been recommended that CPP be maintained between 50 and 70 mmHg, the evidence to support this recommendation are not overly compelling.74 Furthermore, a retrospective cohort study of patients with severe TBI found that ICP/CPP-targeted neurointensive care was associated with prolonged


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Surgery_Schwartz. this recommendation are not overly compelling.74 Furthermore, a retrospective cohort study of patients with severe TBI found that ICP/CPP-targeted neurointensive care was associated with prolonged mechanical ventilation and increased therapeutic interventions, without evi-dence for improved outcome in patients who survive beyond 24 hours.75Electroencephalogram and Evoked PotentialsElectroencephalography offers the capacity to monitor global neurologic electrical activity, while evoked potential monitor-ing can assess pathways not detected by the conventional EEG. Continuous EEG (CEEG) monitoring in the intensive care unit permits ongoing evaluation of cerebral cortical activity. It is especially useful in obtunded and comatose patients. CEEG also is useful for monitoring of therapy for status epilepticus and detecting early changes associated with cerebral ischemia. CEEG can be used to adjust the level of sedation, especially if high-dose barbiturate therapy is being used to manage


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Surgery_Schwartz. status epilepticus and detecting early changes associated with cerebral ischemia. CEEG can be used to adjust the level of sedation, especially if high-dose barbiturate therapy is being used to manage elevated ICP. Somatosensory and brain stem evoked potentials are less affected by the administration of sedatives than is the EEG. Evoked potentials are useful for localizing brain stem lesions or proving the absence of such structural lesions in cases of metabolic or toxic coma. They also can provide prognostic data in posttraumatic coma.An advance in EEG monitoring is the use of the bispectral index (BIS) to titrate the level of sedative medications. While sedative drugs are usually titrated to the clinical neurologic examination, the BIS device has been used in the operating room to continuously monitor the depth of anesthesia. The BIS is an empiric measurement statistically derived from a data-base of over 5000 EEGs.76 The BIS is derived from bifrontal EEG recordings and analyzed for


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Surgery_Schwartz. monitor the depth of anesthesia. The BIS is an empiric measurement statistically derived from a data-base of over 5000 EEGs.76 The BIS is derived from bifrontal EEG recordings and analyzed for burst suppression ratio, rela-tive alpha to beta ratio, and bicoherence. Using a multivariate regression model, a linear numeric index (BIS) is calculated, ranging from 0 (isoelectric EEG) to 100 (fully awake). Its use has been associated with lower consumption of anesthet-ics during surgery and earlier awakening and faster recovery from anesthesia.77 The BIS also has been validated as a useful approach for monitoring the level of sedation for ICU patients, using the revised Sedation-Agitation Scale as a gold standard.78Transcranial Doppler UltrasonographyThis modality provides a noninvasive method for evaluating cerebral hemodynamics. Transcranial Doppler (TCD) measure-ments of middle and anterior cerebral artery blood flow velocity are useful for the diagnosis of cerebral vasospasm after


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Surgery_Schwartz. for evaluating cerebral hemodynamics. Transcranial Doppler (TCD) measure-ments of middle and anterior cerebral artery blood flow velocity are useful for the diagnosis of cerebral vasospasm after sub-arachnoid hemorrhage. Qureshi and associates demonstrated that an increase in the middle cerebral artery mean flow velocity as assessed by TCD is an independent predictor of symptom-atic vasospasm in a prospective study of patients with aneurys-mal subarachnoid hemorrhage.79 In addition, while some have proposed using TCD to estimate ICP, studies have shown that TCD is not a reliable method for estimating ICP and CPP and currently cannot be endorsed for this purpose.80 TCD also is useful to confirm the clinical examination for determining brain death in patients with confounding factors such as the presence of CNS depressants or metabolic encephalopathy.Jugular Venous OximetryWhen the arterial oxygen content, hemoglobin concentration, and the oxyhemoglobin dissociation curve are constant,


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Surgery_Schwartz. the presence of CNS depressants or metabolic encephalopathy.Jugular Venous OximetryWhen the arterial oxygen content, hemoglobin concentration, and the oxyhemoglobin dissociation curve are constant, changes in jugular venous oxygen saturation (Sjo2) reflect changes in the difference between cerebral oxygen delivery and demand. Brunicardi_Ch13_p0433-p0452.indd 44822/02/19 2:21 PM 449PHYSIOLOGIC MONITORING OF THE SURGICAL PATIENTCHAPTER 13Generally, a decrease in Sjo2 reflects cerebral hypoperfusion, whereas an increase in Sjo2 indicates the presence of hyperemia. Sjo2 monitoring cannot detect decreases in regional cerebral blood flow if overall perfusion is normal or above normal. This technique requires the placement of a catheter in the jugular bulb, usually via the internal jugular vein. Catheters that permit intermittent aspiration of jugular venous blood for analysis or continuous oximetry catheters are available.Low Sjo2 is associated with poor outcomes after TBI.81


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Surgery_Schwartz. jugular vein. Catheters that permit intermittent aspiration of jugular venous blood for analysis or continuous oximetry catheters are available.Low Sjo2 is associated with poor outcomes after TBI.81 Nevertheless, the value of monitoring Sjo2 remains unproven. If it is employed, it should not be the sole monitoring technique, but rather should be used in conjunction with ICP and CPP monitoring. By monitoring ICP, CPP, and Sjo2, early interven-tion with volume, vasopressors, and hyperventilation has been shown to prevent ischemic events in patients with TBI.82Transcranial Near-Infrared SpectroscopyTranscranial near-infrared spectroscopy (NIRS) is a noninvasive continuous monitoring method to determine cerebral oxygen-ation. It employs technology similar to that of pulse oximetry to determine the concentrations of oxyand deoxyhemoglobin with near-infrared light and sensors and takes advantage of the relative transparency of the skull to light in the near-infrared region of the spectrum.


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Surgery_Schwartz. the concentrations of oxyand deoxyhemoglobin with near-infrared light and sensors and takes advantage of the relative transparency of the skull to light in the near-infrared region of the spectrum. Continuous monitoring of cerebral per-fusion via transcranial NIRS may provide a method to detect early cerebral ischemia in patients with traumatic brain injury.83 Nevertheless, this form of monitoring remains largely a research tool at the present time.Recently, some authors have reported its use as a poten-tial triage tool for prehospital care in the management of TBI, as NIRS allows for rapid screening for intracranial hematoma. Two small EMS studies demonstrated that handheld NIRS devices may be feasible adjunct tools in this setting, particularly when CT scanners may not be readily available.84,85Brain Tissue Oxygen TensionWhile the standard of care for patients with severe TBI includes ICP and CPP monitoring, this strategy does not always prevent secondary brain injury. Growing


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Surgery_Schwartz. Tissue Oxygen TensionWhile the standard of care for patients with severe TBI includes ICP and CPP monitoring, this strategy does not always prevent secondary brain injury. Growing evidence suggests that moni-toring local brain tissue oxygen tension (PbtO2) may be a useful adjunct to ICP monitoring in these patients. Normal values for PbtO2 are 20 to 40 mmHg, and critical levels are 8 to 10 mmHg. A recent clinical study sought to determine whether the addi-tion of a PbtO2 monitor to guide therapy in severe traumatic brain injury was associated with improved patient outcomes.86 Twenty-eight patients with severe traumatic brain injury (GCS score ≤8) were enrolled in an observational study at a level I trauma center. These patients received invasive ICP and PbtO2 monitoring and were compared with 25 historical controls matched for age, injuries, and admission GCS score that had undergone ICP monitoring alone. Goals of therapy in both groups included maintaining an ICP <20 mmHg and a CPP


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Surgery_Schwartz. with 25 historical controls matched for age, injuries, and admission GCS score that had undergone ICP monitoring alone. Goals of therapy in both groups included maintaining an ICP <20 mmHg and a CPP >60 mmHg. Among patients with PbtO2 monitoring, therapy also was directed at maintaining PbtO2 >25 mmHg. The groups had similar mean daily ICP and CPP levels. The mortality rate in the historical controls treated with standard ICP and CPP management was 44%. Mortality was significantly lower in the patients who had therapy guided by PbtO2 monitoring in addition to ICP and CPP (25%; P <.05). The benefits of PbtO2 monitoring may include the early detection of brain tissue isch-emia despite normal ICP and CPP. In addition, PbtO2-guided management may reduce potential adverse effects associated with therapies to maintain ICP and CPP.CONCLUSIONSModern intensive care is predicated by the need and ability to continuously monitor a wide range of physiologic parameters. This capability has


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Surgery_Schwartz. with therapies to maintain ICP and CPP.CONCLUSIONSModern intensive care is predicated by the need and ability to continuously monitor a wide range of physiologic parameters. This capability has dramatically improved the care of critically ill patients and advanced the development of the specialty of critical care medicine. In some cases, the technological abil-ity to measure such variables has surpassed our understanding of the significance or the knowledge of the appropriate inter-vention to ameliorate such pathophysiologic changes. In addi-tion, the development of less invasive monitoring methods has been promoted by the recognition of complications associated with invasive monitoring devices. The future portends the con-tinued development of noninvasive monitoring devices along with their application in an evidenced-based strategy to guide rational therapy.REFERENCESEntries highlighted in bright blue are key references. 1. Bur A, Herkner H, Vlcek M, et al. Factors influencing the


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Surgery_Schwartz. application in an evidenced-based strategy to guide rational therapy.REFERENCESEntries highlighted in bright blue are key references. 1. Bur A, Herkner H, Vlcek M, et al. Factors influencing the accu-racy of oscillometric blood pressure measurement in critically ill patients. Crit Care Med. 2003;31(3):793-799. 2. Fischer MO, Avram R, Carjaliu I, et al. Non-invasive continu-ous arterial pressure and cardiac index monitoring with Nexfin after cardiac surgery. Br J Anaesth. 2012;109(4):514-521. 3. Traore O, Liotier J, Souweine B. Prospective study of arterial and central venous catheter colonization and of arterialand central venous catheter-related bacteremia in intensive care units. Crit Care Med. 2005;33(6):1276-1280. 4. Landesberg G, Mosseri M, Wolf Y, Vesselov Y, Weissman C. Perioperative myocardial ischemia and infarction: identifica-tion by continuous 12-lead electrocardiogram with online ST-segment monitoring. Anesthesiology. 2002;96(2):264-270. 5. Ollila A, Virolainen J,


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Surgery_Schwartz. myocardial ischemia and infarction: identifica-tion by continuous 12-lead electrocardiogram with online ST-segment monitoring. Anesthesiology. 2002;96(2):264-270. 5. Ollila A, Virolainen J, Vanhatalo J, et al. Postoperative cardiac ischemia detection by continuous 12-lead electrocardiographic monitoring in vascular surgery patients: a prospective, observa-tional study. J Cardiothorac Vasc Anesth. 2017;31(3):950-956. 6. Yu H, Pi-Hua F, Yuan W, et al. Prediction of sudden cardiac death in patients after acute myocardial infarction using T-wave alter-nans: a prospective study. J Electrocardiol. 2012;45(1):60-65. 7. Chen WL, Tsai TH, Huang CC, Chen JH, Kuo CD. Heart rate variability predicts short-term outcome for successfully resusci-tated patients with out-of-hospital cardiac arrest. Resuscitation. 2009;80(10):1114-1118. 8. Hravnak M, Edwards L, Clontz A, Valenta C, Devita MA, Pinsky MR. Defining the incidence of cardiorespiratory instabil-ity in patients in step-down units using an


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Surgery_Schwartz. 2009;80(10):1114-1118. 8. Hravnak M, Edwards L, Clontz A, Valenta C, Devita MA, Pinsky MR. Defining the incidence of cardiorespiratory instabil-ity in patients in step-down units using an electronic integrated monitoring system. Arch Intern Med. 2008;168(12):1300-1308. 9. Hravnak M, Devita MA, Clontz A, Edwards L, Valenta C, Pinsky MR. Cardiorespiratory instability before and after implementing an integrated monitoring system. Crit Care Med. 2011;39(1):65-72. 10. Rothman MJ, Rothman SI, Beals J 4th. Development and vali-dation of a continuous measure of patient condition using the Electronic Medical Record. J Biomed Inform. 2013;46(5):837-848. 11. Tepas JJ 3rd, Rimar JM, Hsiao AL, Nussbaum MS. Auto-mated analysis of electronic medical record data reflects the pathophysiology of operative complications. Surgery. 2013;154(4):918-924; discussion 924-926. 12. Piper GL, Kaplan LJ, Maung AA, Lui FY, Barre K, Davis KA. Using the Rothman index to predict early unplanned surgical intensive


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Surgery_Schwartz. complications. Surgery. 2013;154(4):918-924; discussion 924-926. 12. Piper GL, Kaplan LJ, Maung AA, Lui FY, Barre K, Davis KA. Using the Rothman index to predict early unplanned surgical intensive care unit readmissions. J Trauma Acute Care Surg. 2014;77(1):78-82. 13. Wengerter BC, Pei KY, Asuzu D, Davis KA. Rothman Index variability predicts clinical deterioration and rapid response activation. Am J Surg. 2017;215(3):37-41.Brunicardi_Ch13_p0433-p0452.indd 44922/02/19 2:21 PM 450BASIC CONSIDERATIONSPART I 14. Hayashi H, Amano M. Does ultrasound imaging before puncture facilitate internal jugular vein cannulation? Prospective random-ized comparison with landmark-guided puncture in ventilated patients. J Cardiothorac Vasc Anesth. 2002;16(5):572-575. 15. Mihm FG, Gettinger A, Hanson CW 3rd, et al. A multicenter evaluation of a new continuous cardiac output pulmonary artery catheter system. Crit Care Med. 1998;26(8):1346-1350. 16. London MJ, Moritz TE, Henderson WG, et al. Standard


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Surgery_Schwartz. 3rd, et al. A multicenter evaluation of a new continuous cardiac output pulmonary artery catheter system. Crit Care Med. 1998;26(8):1346-1350. 16. London MJ, Moritz TE, Henderson WG, et al. Standard ver-sus fiberoptic pulmonary artery catheterization for cardiac surgery in the Department of Veterans Affairs: a prospec-tive, observational, multicenter analysis. Anesthesiology. 2002;96(4):860-870. 17. Rivers EP, Ander DS, Powell D. Central venous oxygen satura-tion monitoring in the critically ill patient. Curr Opin Crit Care. 2001;7(3):204-211. 18. Varpula M, Karlsson S, Ruokonen E, Pettila V. Mixed venous oxygen saturation cannot be estimated by central venous oxygen saturation in septic shock. Intens Care Med. 2006;32(9):1336-1343. 19. Rivers E, Nguyen B, Havstad S, et al. Early goal-directed therapy in the treatment of severe sepsis and septic shock. N Engl J Med. 2001;345:1368-1377. 20. Dellinger RP, Levy MM, Rhodes A, et al. Surviving sepsis cam-paign: international guidelines for


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Surgery_Schwartz. therapy in the treatment of severe sepsis and septic shock. N Engl J Med. 2001;345:1368-1377. 20. Dellinger RP, Levy MM, Rhodes A, et al. Surviving sepsis cam-paign: international guidelines for management of severe sep-sis and septic shock: 2012. Crit Care Med. 2013;41(2):580-637. 21. Connors AF, Jr, Speroff T, Dawson NV, et al. The effec-tiveness of right heart catheterization in the initial care of critically ill patients. SUPPORT Investigators. JAMA. 1996;276(11):889-897. 22. Pearson KS, Gomez MN, Moyers JR, Carter JG, Tinker JH. A cost/benefit analysis of randomized invasive monitor-ing for patients undergoing cardiac surgery. Anesth Analg. 1989;69(3):336-341. 23. Tuman KJ, McCarthy RJ, Spiess BD, et al. Effect of pulmonary artery catheterization on outcome in patients undergoing coro-nary artery surgery. Anesthesiology. 1989;70(2):199-206. 24. Bender JS, Smith-Meek MA, Jones CE. Routine pulmonary artery catheterization does not reduce morbidity and mortality of elective vascular


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Surgery_Schwartz. artery surgery. Anesthesiology. 1989;70(2):199-206. 24. Bender JS, Smith-Meek MA, Jones CE. Routine pulmonary artery catheterization does not reduce morbidity and mortality of elective vascular surgery: results of a prospective, random-ized trial. Ann Surg. 1997;226(3):229-236. 25. Valentine RJ, Duke ML, Inman MH, et al. Effectiveness of pul-monary artery catheters in aortic surgery: a randomized trial. J Vasc Surg. 1998;27(2):203-211; discussion 211-212. 26. Sandham JD, Hull RD, Brant RF, et al. A randomized, con-trolled trial of the use of pulmonary-artery catheters in high-risk surgical patients. N Engl J Med. 2003;348(1):5-14. 27. Harvey S, Harrison DA, Singer M, et al. Assessment of the clinical effectiveness of pulmonary artery catheters in manage-ment of patients in intensive care (PAC-Man): a randomised controlled trial. Lancet. 2005;366(9484):472-477. 28. Shah MR, Hasselblad V, Stevenson LW, et al. Impact of the pul-monary artery catheter in critically ill patients:


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Surgery_Schwartz. care (PAC-Man): a randomised controlled trial. Lancet. 2005;366(9484):472-477. 28. Shah MR, Hasselblad V, Stevenson LW, et al. Impact of the pul-monary artery catheter in critically ill patients: meta-analysis of randomized clinical trials. JAMA. 2005;294(13):1664-1670. 29. Binanay C, Califf RM, Hasselblad V, et al. Evaluation study of congestive heart failure and pulmonary artery catheterization effectiveness: the ESCAPE trial. JAMA. 2005;294(13):1625-1633. 30. National Heart, Lung, and Blood Institute Acute Respira-tory Distress Syndrome (ARDS) Clinical Trials Network; Wheeler AP, Bernard GR, Thompson BT, et al. Pulmonary-artery versus central venous catheter to guide treatment of acute lung injury. N Engl J Med. 2006;354(21):2213-2224. 31. Wiener RS, Welch HG. Trends in the use of the pulmo-nary artery catheter in the United States, 1993-2004. JAMA. 2007;298(4):423-429. 32. Shoemaker WC, Appel PL, Kram HB, Waxman K, Lee TS. Prospective trial of supranormal values of survivors as


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Surgery_Schwartz. pulmo-nary artery catheter in the United States, 1993-2004. JAMA. 2007;298(4):423-429. 32. Shoemaker WC, Appel PL, Kram HB, Waxman K, Lee TS. Prospective trial of supranormal values of survivors as therapeutic goals in high-risk surgical patients. Chest. 1988;94(6):1176-1186. 33. Bishop MH, Shoemaker WC, Appel PL, et al. Prospective, randomized trial of survivor values of cardiac index, oxygen delivery, and oxygen consumption as resuscitation endpoints in severe trauma. J Trauma. 1995;38(5):780-787. 34. Heyland DK, Cook DJ, King D, Kernerman P, Brun-Buisson C. Maximizing oxygen delivery in critically ill patients: a methodologic appraisal of the evidence. Crit Care Med. 1996;24(3):517-524. 35. Alia I, Esteban A, Gordo F, et al. A randomized and controlled trial of the effect of treatment aimed at maximizing oxygen delivery in patients with severe sepsis or septic shock. Chest. 1999;115(2):453-461. 36. Gnaegi A, Feihl F, Perret C. Intensive care physicians’ insuf-ficient knowledge of


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Surgery_Schwartz. aimed at maximizing oxygen delivery in patients with severe sepsis or septic shock. Chest. 1999;115(2):453-461. 36. Gnaegi A, Feihl F, Perret C. Intensive care physicians’ insuf-ficient knowledge of right-heart catheterization at the bedside: time to act? Crit Care Med. 1997;25(2):213-220. 37. Gan TJ, Soppitt A, Maroof M, et al. Goal-directed intraopera-tive fluid administration reduces length of hospital stay after major surgery. Anesthesiology. 2002;97(4):820-826. 38. Monnet X, Teboul JL. Transpulmonary thermodilution: advan-tages and limits. Crit Care. 2017;21(1):147. 39. Dark PM, Singer M. The validity of trans-esophageal Doppler ultrasonography as a measure of cardiac output in critically ill adults. Intensive Care Med. 2004;30(11):2060-2066. 40. Imhoff M, Lehner JH, Lohlein D. Noninvasive whole-body electrical bioimpedance cardiac output and invasive thermodi-lution cardiac output in high-risk surgical patients. Crit Care Med. 2000;28(8):2812-2818. 41. Marik PE. Noninvasive


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Surgery_Schwartz. whole-body electrical bioimpedance cardiac output and invasive thermodi-lution cardiac output in high-risk surgical patients. Crit Care Med. 2000;28(8):2812-2818. 41. Marik PE. Noninvasive cardiac output monitors: a state-of the-art review. J Cardiothorac Vasc Anesth. 2013;27(1):121-134. 42. Mielck F, Buhre W, Hanekop G, Tirilomis T, Hilgers R, Sonntag H. Comparison of continuous cardiac output measurements in patients after cardiac surgery. J Cardiothorac Vasc Anesth. 2003;17(2):211-216. 43. Remmen JJ, Aengevaeren WR, Verheugt FW, et al. Finapres arterial pulse wave analysis with Modelflow is not a reliable non-invasive method for assessment of cardiac output. Clin Sci (Lond). 2002;103(2):143-149. 44. van Heerden PV, Baker S, Lim SI, Weidman C, Bulsara M. Clinical evaluation of the non-invasive cardiac output (NICO) monitor in the intensive care unit. Anaesth Intensive Care. 2000;28(4):427-430. 45. Odenstedt H, Stenqvist O, Lundin S. Clinical evaluation of a partial CO2 rebreathing


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Surgery_Schwartz. cardiac output (NICO) monitor in the intensive care unit. Anaesth Intensive Care. 2000;28(4):427-430. 45. Odenstedt H, Stenqvist O, Lundin S. Clinical evaluation of a partial CO2 rebreathing technique for cardiac output moni-toring in critically ill patients. Acta Anaesthesiol Scand. 2002;46(2):152-159. 46. Godje O, Peyerl M, Seebauer T, Lamm P, Mair H, Reichart B. Central venous pressure, pulmonary capillary wedge pressure and intrathoracic blood volumes as preload indicators in cardiac surgery patients. Eur J Cardiothorac Surg. 1998;13(5):533-539. 47. Pinsky MR, Teboul JL. Assessment of indices of preload and vol-ume responsiveness. Curr Opin Crit Care. 2005;11(3):235-239. 48. Lichtwarck-Aschoff M, Zeravik J, Pfeiffer UJ. Intrathoracic blood volume accurately reflects circulatory volume status in critically ill patients with mechanical ventilation. Intens Care Med. 1992;18(3):142-147. 49. Gunn SR, Pinsky MR. Implications of arterial pressure varia-tion in patients in the intensive


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Surgery_Schwartz. status in critically ill patients with mechanical ventilation. Intens Care Med. 1992;18(3):142-147. 49. Gunn SR, Pinsky MR. Implications of arterial pressure varia-tion in patients in the intensive care unit. Curr Opinion Crit Care. 2001;7(3):212-217. 50. Mesquida J, Kim HK, Pinsky MR. Effect of tidal volume, intrathoracic pressure, and cardiac contractility on variations in pulse pressure, stroke volume, and intrathoracic blood volume. Intens Care Med. 2011;37(10):1672-1679. 51. Michard F, Chemla D, Richard C, et al. Clinical use of respiratory changes in arterial pulse pressure to monitor the hemodynamic effects of PEEP. Am J Resp Crit Care. 1999;159(3):935-939.Brunicardi_Ch13_p0433-p0452.indd 45022/02/19 2:21 PM 451PHYSIOLOGIC MONITORING OF THE SURGICAL PATIENTCHAPTER 13 52. Michard F, Boussat S, Chemla D, et al. Relation between respi-ratory changes in arterial pulse pressure and fluid responsive-ness in septic patients with acute circulatory failure. Am J Resp Crit Care.


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Surgery_Schwartz. F, Boussat S, Chemla D, et al. Relation between respi-ratory changes in arterial pulse pressure and fluid responsive-ness in septic patients with acute circulatory failure. Am J Resp Crit Care. 2000;162(1):134-138. 53. Crookes BA, Cohn SM, Burton EA, Nelson J, Proctor KG. Noninvasive muscle oxygenation to guide fluid resuscitation after traumatic shock. Surgery. 2004;135(6):662-670. 54. Cohn SM, Nathens AB, Moore FA, et al. Tissue oxygen satu-ration predicts the development of organ dysfunction during traumatic shock resuscitation. J Trauma. 2007;62(1):44-54; discussion; 54-55. 55. Haller M, Kilger E, Briegel J, Forst H, Peter K. Continuous intra-arterial blood gas and pH monitoring in critically ill patients with severe respiratory failure: a prospective, criterion standard study. Crit Care Med. 1994;22(4):580-587. 56. The Acute Respiratory Distress Syndrome Network; Brower RG, Matthay MA, Morris A, et al. Ventilation with lower tidal vol-umes as compared with traditional tidal


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Surgery_Schwartz. Care Med. 1994;22(4):580-587. 56. The Acute Respiratory Distress Syndrome Network; Brower RG, Matthay MA, Morris A, et al. Ventilation with lower tidal vol-umes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342(18):1301-1308. 57. Serpa Neto A, Cardoso SO, Manetta JA, et al. Associa-tion between use of lung-protective ventilation with lower tidal volumes and clinical outcomes among patients without acute respiratory distress syndrome: a meta-analysis. JAMA. 2012;308(16):1651-1659. 58. Futier E, Constantin JM, Paugam-Burtz C, et al. A trial of intra-operative low-tidal-volume ventilation in abdominal surgery. N Engl J Med. 2013;369(5):428-437. 59. Tremper KK, Barker SJ. Pulse oximetry. Chest. 1989; 70(1):713-715. 60. Shoemaker WC, Belzberg H, Wo CCJ, et al. Multicenter study of noninvasive monitoring systems as alternatives to invasive monitoring of acutely ill emergency patients. Chest.


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Surgery_Schwartz. 1989; 70(1):713-715. 60. Shoemaker WC, Belzberg H, Wo CCJ, et al. Multicenter study of noninvasive monitoring systems as alternatives to invasive monitoring of acutely ill emergency patients. Chest. 1998;114(6):1643-1652. 61. Taenzer AH, Pyke JB, McGrath SP, Blike GT. Impact of pulse oximetry surveillance on rescue events and intensive care unit transfers: a before-and-after concurrence study. Anesthesiology. 2010;112(2):282-287. 62. Applegate RL 2nd, Barr SJ, Collier CE, Rook JL, Mangus DB, Allard MW. Evaluation of pulse cooximetry in patients undergoing abdominal or pelvic surgery. Anesthesiology. 2012;116(1):65-72. 63. Gayat E, Aulagnier J, Matthieu E, et al. Non-invasive measure-ment of hemoglobin: assessment of two different point-of-care technologies. PLoS One. 2012;7:e30065. 64. Park YH, Lee JH, Song HG, Byon HJ, Kim HS, Kim JT. The accuracy of noninvasive hemoglobin monitoring using the radical-7 pulse CO-Oximeter in children undergoing neurosur-gery. Anesth Analg.