Ionized calcium and magnesium in the baboon: Hemorrhagic shock and resuscitation

Ionized calcium (Ca²⁺) and ionized magnesium (Mg²⁺) are important intracellular 'second messengers' and control excitation-contraction coupling excitation-secretion coupling, oxidative phosphorylation, and mitochondrial acid-base balance. This study examines the effect of hemorrhagic shock on serum Ca²⁺ and Mg²⁺. Eight baboons were subjected to severe hemorrhagic shock and then resuscitated. Ca²⁺ was measured by the Orion SS-20 flow-through calcium electrode and Mg²⁺ was calculated by the method of Killen. Other measurements included: total calcium, bound calcium, total magnesium, bound magnesium, albumin, globulin, total protein, phosphate, pH, and hematocrit. This study shows that there are significant disturbances of Ca²⁺ and Mg²⁺ during resuscitation from hemorrhagic shock. These disturbances may in part explain cellular dysfunctions during shock, including decreased myocardial contractility, inappropriate secretion of endocrine cells, decrease in oxidative phosphorylation, and mitochondrial acidosis.