Arterial Blood Gases Interpretation


Purpose of ABG
–    Assess degree to which lungs are able to provide adequate oxygen & remove CO2 & degree to which the kidneys are able to reabsorb or excrete HCO3
1.    Establish the diagnosis and severity of respiratory failure
2.    Manage patients in intensive therapy units admitted for:
–      Respiratory failure or dysfunction
–      Cardiac failure
–      Renal or hepatic failure
–      Poly trauma and multiorgan failure
–      Diabetic ketoacidosis
–      Sepsis and burns
–      Poisoning
3. Guide therapy in patients in the ICU, e.g.
–    Oxygen administration
–    Mechanical ventilation
4. Monitor patients during
–    Cardiopulmonary surgery
–    Cardiopulmonary exercise testing
–    Sleep studies
5. Determine prognosis in critically ill patientsAcid Base Balance
ABG analysis
1.    Metabolic: referring to
–    Metabolism: the sum of all chemical processes that take place in the body as they relate to the movement of nutrients in the blood after digestion, resulting in growth, energy, release of wastes, and other body functions.
2.    Respiratory: referring to breathing (respiration).
–    Respiration: breathing, the give and take of oxygen and carbon dioxide in the body’s tissues, from the lungs to the level of the cells. The rate changes with the age and condition of the person.
3.   Acidosis: is the process that cause acidemia.
–    Acidemia: is a condition in which the hydrogen ion concentration of the blood is elevated, the blood has an acid excess or base deficit (pH < 7.35).
4.   Alkalosis: is the process that cause alkalemia.
–    Alkalemia: is a condition in which the hydrogen ion concentration of the blood is reduced, the blood has an acid deficit or base excess (pH > 7.45).
ABG analysis


–    PH: is a measure of its hydrogen-ion concentration.
–    CO2: Carbonic dioxide, is a potential acid, when dissolve in water, its comes Carbonic acid H2CO3
–    HCO3: bicarbonate, is a base and accepting or combine with H+ ions to remove these ions from a solution.
–    PO2: Partial Pressure of Oxygen
–    PAO2: Partial Pressure of Alveolar oxygen
–    O2 Saturation: Percentage of haemoglobin which oxygenated (oxyhaemoglobin). At low partial pressures of oxygen, most hemoglobin is deoxygenated.
–     O2 Saturation  > 88% = Arterial
< 88% = Mixed, Venous
–    BE: Base Excess, Base that must be added to Restore a normal pH . The value is usually reported in units of (mEq/L).
•    Normal  Range: -2 to +2 meq/L
–    Positive (Base Excess): Metabolic Alkalosis
–    Negative (Base Deficit): Metabolic Acidosis

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