Calcium shifts during hemorrhagic shock in baboons

Myocardial contractility after resuscitation from deep shock is often transiently depressed, despite adequate volume replacement. Contraction of myofilaments in myocardium and other striated muscles is mediated by calcium. This study with 14 baboons was designed to measure changes in calcium in the extracellular and intracellular spaces of skeletal muscle of primates in deep hemorrhagic shock. The extracellular pool of skeletal muscle Ca⁺⁺ decreases markedly during deep hemorrhagic shock, and returns to preshock values 2.5 hr after resuscitation. Ca⁺⁺ shifts are correlated with shifts of Na⁺ and H₂O, consistent with the hypothesis that transport of Ca⁺⁺ and Na⁺ across the cell membrane is linked by a common mechanism. Similar shifts may occur in other tissues, particularly the heart, and could be responsible for depressing myocardial contractility in patients being resuscitated from shock.