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Chapter 046. Sodium and Water (Part 13)

Redistribution into Cells Movement of K+ into cells may transiently decrease the plasma K + concentration without altering total body K+ content. For any given cause, the magnitude of the change is relatively small, often | Chapter 046. Sodium and Water Part 13 Redistribution into Cells Movement of K into cells may transiently decrease the plasma K concentration without altering total body K content. For any given cause the magnitude of the change is relatively small often 1 mmol L. However a combination of factors may lead to a significant fall in the plasma K concentration and may amplify the hypokalemia due to K wasting. Metabolic alkalosis is often associated with hypokalemia. This occurs as a result of K redistribution as well as excessive renal K loss. Treatment of diabetic ketoacidosis with insulin may lead to hypokalemia due to stimulation of the Na -H antiporter and secondarily the Na K -ATPase pump. Furthermore uncontrolled hyperglycemia often leads to K depletion from an osmotic diuresis see below . Stress-induced catecholamine release and administration of 02-adrenergic agonists directly induce cellular uptake of K and promote insulin secretion by pancreatic islet 0cells. Hypokalemic periodic paralysis is a rare condition characterized by recurrent episodic weakness or paralysis Chap. 382 . Since K is the major ICF cation anabolic states can potentially result in hypokalemia due to a K shift into cells. This may occur following rapid cell growth seen in patients with pernicious anemia treated with vitamin B12 or with neutropenia after treatment with granulocyte-macrophage colony stimulating factor. Massive transfusion with thawed washed red blood cells RBCs could cause hypokalemia since frozen RBCs lose up to half of their K during storage. Nonrenal Loss of Potassium Excessive sweating may result in K depletion from increased integumentary and renal K loss. Hyperaldosteronism secondary to ECF volume contraction enhances K excretion in the urine Chap. 336 . Normally K lost in the stool amounts to 5-10 mmol d in a volume of 100-200 mL. Hypokalemia subsequent to increased gastrointestinal loss can occur in patients with profuse diarrhea usually secretory villous adenomas .