NMS. Surgery

9

Chapter 1 ♦ Principles of Surgical Physiology

2. Diagnosis/etiology: Rarely found in healthy humans with normal diet and kidneys. a. Renal: Diuretics, vomiting (renal excretion of K + to preserve Na + ), renal tubular acidosis. b. Extrarenal: Diarrhea, burns. c. Intracellular shift: Insulin, alkalotic state. d. Medical disease: Hyperaldosteronism, Cushing syndrome. 3. Treatment a. If symptoms are severe, then administer potassium IV centrally in a monitored setting. b. If symptoms are mild, then infuse 20 mEq/hr maximum in the unmonitored patient and 40 mEq/hr in the monitored patient. c. Administration for more chronic conditions can be via the enteral route. B. Hyperkalemia (K + ≥ 6 mEq/L) 1. Signs and symptoms: Diarrhea, cramping, nervousness, weakness, and flaccid paralysis; more often, cardiac dysrhythmias occur before other symptoms. (ECG changes include peaked T waves and widened QRS, and ventricular fibrillation.) 2. Diagnosis/etiology (numerous): Most common include the following: a. Renal failure: With inappropriate consumption and administration of K + . b. Extracellular shift: Rhabdomyolysis, massive tissue necrosis, metabolic acidosis, hyperglycemia. c. Medical disease: Addison disease, major burns, uncontrolled diabetes. 3. Treatment a. Acutely symptomatic patient (1) IV calcium stabilizes cardiac myocyte membranes and can prevent dysrhythmias. (1 g Ca++ gluconate IV is a standard dose.) (2) Glucose/insulin shifts K+ intracellularly acutely and quickly. (1 ampule of D50 with 10 units of regular insulin is often sufficient.) (3) Bicarbonate shifts K + intracellularly. b. To remove K + and lower body stores permanently: (1) Ion-exchange resin: oral or rectal: binds K+, facilitating excretion. (2) Furosemide: Only use if kidneys are functional; monitor electrolytes and fluid balance. (3) Dialysis. IV. Chloride A. Hypochloremia (Cl − < 90 mEq/L) 1. Signs and symptoms: Associated with dehydration or hypokalemia due to GI losses. 2. Diagnosis/etiology a. Gastric hydrochloric acid (HCl) is lost from vomiting, leading to low chloride and a buildup of bicarbonate, causing a metabolic alkalosis . b. Hypochloremia is often associated with paradoxical aciduria . As the dehydration worsens, the kidneys’ drive to retain sodium predominates, and the kidneys excrete both K + and H + to conserve sodium.