Local vascular effects of hypokalemia, alkalosis, hypercalcemia, and hypomagnesemia

Abstract

Blood flowing through the vascular beds of the dog forelimb, kidney, and heart was transiently rendered hypokalemic (1.9 meq/ liter), alkalotic (pH 7.54), hypercalcemic (6.4 to 13.5 meq/ liter), hypomagnesemic (1.2 meq/liter), and hypocalcemic (3.0 meq/liter), singly and in various combinations, while observing resistance to flow and heart contractility. This was accomplished by holding flow rate constant while measuring the effects of rapid intra-arterial infusion of various artificial solutions upon perfusion pressure and left ventricular contractile force. The new findings are a) in situ limb small vessels and kidney vessels respond to local hypokalemia with slight constriction; b) in situ limb small vessels and kidney vessels respond to combinations of local hypokalemia, hypercalcemia, alkalosis, and hypomagnesemia with much more marked constriction than occurs with any one of the abnormalities alone; c) intact heart responds to local hypercalcemia with increased contractile force, to alkalosis with increased coronary resistance, and to combinations of hypokalemia, hypercalcemia, alkalosis, and hypomagnesemia with increased contractile force and increased coronary resistance; and d) in situ limb small vessels and intact heart respond to local hypocalcemia with dilation and decreased contractile force, respectively.