POTASSIUM HOMEOSTASIS

I. Hypokalemia:

  1. Causes: vomiting, diuretics, hyperaldo (liver failure, CHF, Cushing's), diarrhea, renal tubular dis.
  2. Effects: U waves bigger than T's on EKG; ventr. ectopy
  3. Treatment: oral K supplements (40-80mEq in divided doses), IV K (40-80mEq in 500ml D5W IV over 3-6h with cardiac monitor; max. 0.5 mEq/kg/h up to 30mEq/h in adults, ?given as max 40mEq/l unless in central line?)

II. Hyperkalemia:

  1. Causes:
  1. Reduced kaliuresis
  1. Reduced GFR: Acute or Chronic RF of any cause
  2. Reduced tubular K secr.: Addison's & other hypoaldo states, K-sparing diuretics
  1. Shifts between fluid compartments
  1. Acidosis
  2. Cell destruction (tumor lysis, burns, hemolysis)
  3. Hypoinsulinemia, esp. with hyperglycemia
  1. Exogenous K admin. with decr. ability to excrete
  1. Straight K admin
  2. Transfusion
  1. Digitalis
  1. Effects:
  1. Cardiac: Peaked T's @ 6.5mEq/l; Inc. PR intvl @ 7-8, then lost P & wide QRS; asystole @ 8-10
  1. Management options
  1. CaGluconate--counters cardiac f/x; May unmask Dig toxicity
  2. Glucose + Insulin IV
  3. HCO3 IV
  4. Dialysis
  5. Increase potassium excretion with
  1. Diuretics
  2. Hemodialysis
  3. Exchange resins, e.g. Kayexelate (risk of Na overload)--can give PR if pt can't take PO