CURRENT Essentials of Critical Care.pdf

Chapter 5 Fluids, Electrolytes, & Acid-Base 55Hyperkalemia■ Essentials of Diagnosis• Serum potassium [K ] level 5 mEq/L• Weakness beginning in legs, paresthesias, hyporeflexia• ECG changes occur at plasma [K ] 5.7 mEq/L with peakedT-waves; subsequent ECG progression: reduced P-wave amplitude,PR prolongation, QRS widening, broad sine waves, ventricularfibrillation• Transtubular potassium gradient (TTKG) can differentiate renalfrom nonrenal causes: Urine/Plasma (K ) Plasma/Urine (Osm);product 6 renal or hypoaldosterone effect; 10 nonrenal■ Differential Diagnosis• Excess intake: potassium supplements or salts• Reduced excretion: renal failure, adrenal insufficiency, hypoaldosteronism,type IV renal tubular acidosis• Intracellular shift: acidosis, rhabdomyolysis, tumor lysis, severehemolysis, burns• Factitious: hemolysis of blood sample, extreme leukocytosis orthrombocytosis• Medications: K -sparing diuretics, ACE-inhibitors, beta-blockers,succinylcholine, penicillin VK, trimethoprim-sulfamethoxazole■ Treatment• Calcium gluconate or chloride solution: immediate cardioprotectiveeffect; drug of choice with acute ECG changes• Bicarbonate shifts potassium intracellularly, especially if acidemic• Nebulized beta-agonist albuterol can decrease [K ] by 0.6mEq/L within 1 hour• Insulin shifts potassium intracellularly and should be givenalong with dextrose infusion• Binding resin kayexalate removes potassium enterally; use cautiouslyin constipation as may develop concretions• Loop diuretics lower body potassium over hours• Hemodialysis most reliable and efficient method in reducing totalbody potassium• Limit potassium in diet, intravenous fluids, medications■ PearlAttempts made to correct hyperkalemia in the setting of acidosis mayresult in significant total body potassium depletion and serum hypokalemiaonce acidosis is resolved.ReferenceKim HJ et al: Therapeutic approach to hyperkalemia. Nephron 2002;92:33.[PMID: 12401936]