renal-exam 1-sodium homeostasis

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renal-exam 1-sodium homeostasis
2010-03-02 20:52:59

exam 1
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  1. normal serum sodium
    135-145 mEq/L, >90% of the osmolality of the ECF
  2. hypertonic hyponatremia
    serum osmolality >285, excessive nonsodium effective osmoles, excess glucose, treatment: treat underlying cause
  3. isotonic hyponatremia
    serum osmolality 280-285, more of a lab artifact and pretty much a non-issue today because of improved laboratory methods of measuring serum sodium
  4. hypotonic hyponatremia
    serum osmolality <280, can be hyper, iso and hypovolemic
  5. calculate serum osmolality
    P osm=2 * (Na) + glu/18 + BUN/2.8
  6. hyponatremia
    serum sodium <135 mEq/L
  7. hyponatremia signs and sx
    n&V, anorexia, lethargy, HA, muscle cramps
  8. neurologic sx of hyponatremia
    restlessness, disorie, agitation, psychosis, depressed deep tendon reflexes (DTR), Cheyne-stokes respiration, seizures, coma, respiratory depresion, permanent brain damage, death
  9. osmolar gap
    measured serum osmolality-calculated osmolality>15 indicates presence of excess hyperosmolar compounds-may be due to hyperglycemia, for every 100 mg/dl increase in blood sugar>normal, serum sodum decreases 1.7 mEq/L, admin of hyperosmolar solution (mannitol, glycerin), toxicity/poisoning (ethanol, methanol, ethylene glycol)
  10. hypovolemic hyponatremia
    posm<280, loss of sodium and water but sodium >>water loss
  11. signs of being hemodynamically unstable
    postural hypotension, HR > or equal 100bpm, SBP <100 mmHg
  12. renal sodium losses
    >20mEq/L(most common cause) thiazide diuretics(decreased sodium reabsorption), sodium losing renal diseases (nephritis, salt wasting nephropathy), addison's disease (lack of aldosterone)
  13. treatment of hypovolemic hyponatremia
    1. hemodynamically unstable 2. CNS symptoms present 3. rate of sodium replacement
  14. if hemodynamically unstable
    restore intravascular volume 1st (NS or LR 200-300mL/hr, faster if need more volume
  15. No CNS symptoms)
    restore ECF volume deficit=ECF norm-ECF current(use ABW even if >130%), kg * 0.2, give NS or LR at 100-150 mL/hr for L needed
  16. CNS symptoms present
    restore sodium deficit, endpoint 120-125 mEq/L or until symptoms abadate, use CBW or ABW
  17. restoring sodium deficit with CNS symptoms, acute
    <48 hours, NaCl infusion or 3%, calculate change in serum sodium=mEq Na/L in replacement IV-serum Na/(TBW +1), 1. replace with 0.9 plus or minus loop diuretic 2. replace with 3%(potential for error is higher), (513mEq/L plus or minus loop, MUST use infusion pump to deliver no faster than 1-2 mL/kg/hr inititially for first 1-3 hours(100-150mL/hr) 3. check serum sodium q 2-4 hours titrate infusion to raise serum sodium no faster than 2 mEq/L/hr
  18. restoring sodium deficit with CNS symptoms, chronic
    >48 hours, 1. estimate volume of NaCl infusion req to restore sodium deficit using normal saline,2. replace 1/2 over 1st 24 hours and remainder over next 24-72 hours 3. check serum sodium q 4-6 hours initially, titrate infu to raise serum sodium no faster than 0.5mEq/L/hr
  19. maxiumum rate to replace serum sodium to prevent osmotic demyelination syndrome and both acute and chronic
    no more than 8-12 mEq/L/day
  20. isovolemic (euvolemic) hyponatremia
    normal total body sodium and a small increase in total body water, ALWAYS an imbalance of water intake and excretion due to 1.altered thirst 2. inappropriate ADH secretion, 3. defective renal diluting mechanisms
  21. conditions assoc with isovolemic hyponatremia
    severe hypothyroidism, GC deficiency, psychogenic water drinking(>20L/d), SIADH
  22. diagnostic clues of euvolemia
    Uosm>>100mOsm, UNa>>20 mEq/L(very concentrated urine)
  23. etiologies of SIADH
    cancer(secrete ADH), CNS disorders or insults, pulmonary, major surgery, pain, decreased solute intake
  24. drugs that can cause isovolemic hyponatremia
    nicotine, opiates, cyclophosphamide, vinc/vinblastine, phenothiazines, tricyclics, MAOI, carbamazepine, NSAIDs, desmopressin, oxytocin, ecstacy, SSRIs
  25. treatment of isovolemia hyponatremia, moderate to severe CNS symptoms (agitation, seizures, delirium)
    fluid restrict to 1-1.5 L/d plus or minus furosemide (20 mg q 4-6 hours) 1. correct with 3%(need to use), endpoint 120-125mEq/L, must use infusion pump to deliver NFT 1-2cc/kg/hr initially, monitor Na, VS, sx, and fluid status q 2-4 hours in first 24 hou, titrate to raise NFT 1-2 mEq/L/hr in first 24 hours and then decrease over remaining 24 hours
  26. 2nd option for mod-sev CNS symptoms with isovolemic hyponatremia
    AVP receptor antagonsits (aquaretics)-contra in hypovolemia, conivaptan or tolvaptan
  27. treatment of isovolemic hyponatremia, asymptomatic or mild CNS symptoms
    fluid restrict 1-1.5 L/day plus or minus demeclocycline 300 mg qid-blocks effects of ADH in collecting ducts, onset 3-6 days(long) or plus or minus increase solute ingestion and increase free water excretion by increasing salt intake (2-3 gm over usual + lasix) or urea 30gm/d
  28. hypervolemic hypotonic hyponatremia
    increased total body water and sodium but water>>sodium
  29. conditions associated with hypervolemic hypotonic hyponatremia
    CHF, syndromes assoc with decreased plasma alb (cirrhosis, nephritic syndrome, malnutrition), chronic renal failure(renin-angio system), pregnancy(increased blood volume)
  30. treatment of hypervolemic hypotonic hyponatremia
    correct underlying cause, fluid restrict, saline restrict(<2.4g/d), loop diuretics (increase free H20 excretion)
  31. hypernatremia
    >145 mEq/L, always hypertonic-reflects a water deficit relative to sodium, classify according to volume status
  32. initial signs and sx of hypernatremia
    thirst, fever, NV, Gi cramping, lethargy
  33. neurologic symptoms of hypernatremia
    only if acute increase in serum sodium, altered mental status, irritability, restless, muscle spasm, hyperreflexia, spaticity, seizures, coma, death
  34. treatment of hypernatremia
    slow correction is mandatory as rapid lowering may result in cerebral edema, seizures, permanent neurological sequelae and death can occur
  35. hypovolemic hypernatremia
    TBW loss
  36. renal causes of hypovolemic hypernatremia
    diuretics, glycosuria, acute/chronic renal failure
  37. non-renal causes of hypovolemic hypernatremia
    adrenal, GI losses, repiratory losses, skin losses
  38. treatment of hypovolemic hypernatremia
    1. hemodynamically unstable, yes replace intravascular (200-300mL/hr with NS or LR, if not 2. replace TBW deficit
  39. TBW deficit for hypovolemic hypernatremia
    TBW deficit(L)=Current TBW x [(na/140)-1], use CBW or ABW, replace with , use D5W(0 mEq/L) or 0.45(77mEq/L), or oral water, double check with change in serum sodium=mEq Na/L in replacement IV-serum Na conc/TBW +1
  40. infusion rate of replace TBW deficit in hypovolemic hypernatremia
    1/2 over first 24 hours, remainder over next 24-72 hours, monitor Na, fluid status, sx q 2-4 hours x 1st 24 hours
  41. rate of correction of hypovolemic hypernatremia, acute
    <24 hours-serum sodium should decrease NFT 1mEq/L/hr
  42. rate of correction of hypovolemic hypernatremia, chronic
    >24 hours, serum sodium should decrease NFT 0.5 mEq/L/hr
  43. targer serum sodium of hypovolemic hypernatremia
    Na<145 mEq/L, replace ongoing water loss
  44. isovolemic hypernatremia
    clinically euvolemic, total body sodium normal; small volume of pure water loss
  45. causes of isovolemic hypernatremia
    central diabetes insipidus(insufficient amt of ADH),nephrogenic diabetes insipidus(kidneys don't respond to ADH), drugs(demeclocycline, lithium, phenytoin, clozapine), high insensible loss(skin and respiratory), Iatrogenic(insufficeient fluid intake)
  46. treatment of isovolemic hypernatremia
    calc water deficit and correct with free water, treat underlying cause
  47. treatment for diabetes insipidus
    desmopressin (DDAVP), aqueous vasopression (ADH), chlorpropamide(increase kidney's response to ADH), clofibrate(increase ADH release), carbamazepine(increase response to ADH), HCTZ(increase sodium excretion), indomethacin(inhibits PG in kidneys(increase ADH effect)
  48. hypervolemic hypernatremia
    increased total body sodium>>increased total body water
  49. causes of hypervolemic hypernatremia
    iatrogenic, MC excess(primary aldosteronism, cushing's syndrome, congenital adrenal hyperplasia, admin of GC or MCs)
  50. treatment of hypervolemic hypernatremia
    d/c offending hypertonic agent, diuretics(loops and thiazides), hemodialysis(with acute renal failure)

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