Clinical Disorders of Hyperkalemia

Abstract

Potassium DistributionTotal body potassium in a healthy adult is approximately 50 meqlkg body weight or about 3500 meq for a 70-kg man (1, 2). Most of this is located within cells (Figure 1), primarily muscle, at a concentration of about 150 meq/L. Only 2% of total body potassium is located in the extracellular fl uid, normally at concentrations of 3.5 -5.0 meq/L. The maintenance of this high intracellular to extracellular K concentration depends upon the Na-K ATPase pump (3, 4) as well as other fac tors, including H+ balance, plasma tonicity, and plasma insulin, epinephrine, and aldosterone concentrations (5). The large difference in potassium concentration across the cell mem brane is critical for normal cell fu nction since it is the primary determinant of the resting membrane potential. Small changes in the intracellular/ex tracellular K ratio can severely disturb neuromuscular fu nction, particu larly of the heart. A gain (or loss) fr om the extracellular space of an amount of potassium equal to only I % of the total body K content (35 meq) can cause a 50% increase (or decrease) in plasma K concentration. Such a change would have pronounced effects on neuromuscular func ti on. Like wise, redistribution of a similar amount of potassium fr om the intracellular to extracellular (or vice versa) fluid compartmen t without net gain or loss of K fr om the body, would similarly affect neuromuscular excitability. Thus, it is important that both the total amount of potassium within the body and the distribution of potassium between intracellular and extracellu lar fl uid compartments be closely regulated.In healthy man, potassium enters only via the gastrointestinal tract. Approximately 100 meq of K is ingested per day and essentially all of this is absorbed fr om the stomach and upper gastrointestinal tract. Approxi-521 0066-4219/8 2/040 1-0521 $02.00 Annu. Rev. Med. 1982.33:521-554. Downloaded from www.annualreviews.org Access provided by Haifa University on 01/05/15. For personal use only.Quick links to online content Further ANNUAL REVIEWS

Hyperaldosteronemia in Rabbits Inhibits the Cardiac Sarcolemmal Na + -K + Pump

“…However, the decrease in serum K ϩ in our study was considerably less than the decrease usually associated with downregulation of the pump. Because skeletal muscles contain Ϸ75% of the total body K ϩ content, 22 a major effect of aldosterone on K ϩ balance should also be reflected in the skeletal muscle K ϩ content. We did not find an aldosterone-induced reduction in K ϩ contents of skeletal muscle or myocardium.…”

Combined Effect of Bicarbonate and Insulin with Glucose in Acute Therapy of Hyperkalemia in End-Stage Renal Disease Patients

“…Principal mecha nisms utilized in acute therapy of hyperkalemia, as de scribed in the standard medical or nephrology textbooks, can be divided into three general categories [1,11]: (a) to oppose the direct toxic effects of hyperkalemia on the cell membrane with calcium salts, (b) to promote cellular uptake of potassium by sodium bicarbonate, insulin and glucose, or (^-adrenergic agonists, (c) to remove potas sium from the body with diuretics, cation-exchange res ins, or dialysis. These measures for acute therapy of hyperkalentic emergencies could be applied to patients with or without end-stage renal disease.…”

“…The standard nephrology and electrolyte textbooks as well as directors of nephrology training programs have recommended the use of bicarbonate and insulin with glu cose as the preferred measures for acute therapy of severe hyperkalemia [1,3,11,15], However, previous observa tions have been made on the individual effect of sodium bicarbonate or on that of insulin and glucose, but not on that of the combined treatment. The main aim of this study was to compare the potassium-lowering effect of the combined regimen of bicarbonate and insulin with glu cose, with that of either regimen alone.…”

“…Despite the widely held view in previous reviews or in a recent survey [1,3,11,15,16] that bicarbonate is effec tive in lowering plasma potassium, it has been shown that sodium bicarbonate is not very effective in reducing plas ma potassium whether it is given for 60 min or for the more extended period of 2-6 h [4. 5].…”

“…Severe hyperkalemia exceeding 6.0 niEq/1 of plasma potassium in patients with end-stage renal disease (ESRD) or oliguria requires urgent management, prefera bly hemodialysis, as a definitive therapy to remove the excess body potassium [1,2]. However, initiation of dialy sis is often delayed, especially on weekends or at night, and other therapeutic approaches have been utilized as temporizing measures until dialysis becomes available.…”