Effect of potassium depletion on acidosis-induced changes in plasma potassium concentration.

It is unknown whether acute metabolic acidosis causes increases in plasma potassium concentration despite pre-existing potassium depletion. In fact, it has long been assumed clinically that acidosis-induced acute hyperkalemia may be masked by potassium depletion. In order to assess this question, moderate to severe potassium depletion was produced in 7 female mongrel dogs (potassium-depleted group) over a 12-day period with injections of desoxycorticosterone acetate (DOCA), NaCl added to the drinking water, and a potassium-free diet. Six dogs (control group) received regular chow, identical NaCl supplements, and sham injections of DOCA. The achievement of potassium depletion was documented by significant differences between the two groups in urinary potassium and in muscle and plasma potassium levels (potassium-depleted group: 0.9 +/- 0.2 mEq/24 h, 19 +/- 3 mEq/100 g dry weight, 1.9 +/- 0.1 mEq/1; control group: 44 +/- 11 mEq/24 h [p less than 0.025], 30 +/- 1 mEq/100 g [p less than 0.005], 3.5 +/- 0.1 mEq/l [p less than 0.005]). There were no statistically significant differences between the groups in blood pH or [HCO3]. On day 13, an NH4Cl acid-load was given (5 mEq/kg body weight i.v. over 3 h in 0.45% NaCl using pentobarbital anesthesia). Following acid-loading, the increases in plasma [K] were significantly greater in the control group than in the potassium-depleted group only at 90 and 120 min. There were no significant differences in the maximal increases from baseline in plasma [K] (potassium-depleted group: 0.6 +/- 0.1 mEq/l, 31 +/- 6%; control group: 1.5 +/- 0.4 mEq/l, 41 +/- 10%).(ABSTRACT TRUNCATED AT 250 WORDS)