Blood ionized calcium measurements during aortocoronary bypass graft operations

Electrode technology has made it feasible to measure and report arterial blood ionized calcium (Ca++) simultaneously with arterial blood gases and pH during aortocoronary bypass graft operations requiring prolonged (duration 1.23-4.43 hours) extracorporeal circulation and moderate hypothermia (25-28 degrees C). Blood Ca++ in 22 consecutive patients remained surprisingly constant at a moderately hypocalcaemic level despite the multiplicity of disturbing factors, but rewarming and blood transfusion did cause a small, but significant decline of blood Ca++. Management of patients has been changed by routine availability of close to real time Ca++ measurements, which are more convenient and faster in this situation than plasma total calcium, which is meaningless or even misleading.