Calcium regulation and nonprotective properties of calcium in surgical ischemia.

Calcium is one of the most important electrolytes in the body. Calcium regulation involves the intricate interaction between intracellular and extracellular levels with the free form of calcium determining function. The parathyroid gland is the principal regulator of ionized calcium in the serum. The kidney and gastrointestinal tract calcium receptors respond to the incorporation of calcium into the cytosol for muscle contraction, cell-cell communication, coagulation, and hormonal and neurotransmitter release functions. The regulation of calcium and the role of calcium antagonists are discussed as they relate primarily to the gastrointestinal tract and liver functions. The use of calcium-channel blockers has augmented myocardial function and has met with some success in decreasing hemorrhagic mucosal ischemia after shock. However, clinical studies evaluating the role of these agents in ischemia have yet to be initiated.