The cardiovascular effects of low levels of ionized calcium produced by the chelating effect of acid-citrate- dextrose or citrate-phospate-dextrose preservative in bank blood are still controversial. The introduction of a rapid, clinically feasible method of determining ionized calcium and the use of the Swan-Ganz catheter to measure pulmonary artery wedge pressure and cardiac output permits investigation of this subject in the operating room. The clinical material consisted of 21 patients with extensive thoracic or abdominal operations requiring massive blood replacement. Blood samples for pH, ionized calcium and total calcium were drawn preoperatively, at frequent intervals during operation and at completion. Blood pressure, central venous pressure and a recorded electrocardiogram were obtained simultaneously with each sample. Each electrocardiogram was analyzed for the Q-Tc and Q-oTc interval. In ten patients, cardiac output was measured in addition to the previous blood samples and monitoring parameters. The results of these studies were compared at three points: preoperative, lowest level of ionized calcium and end operation. The Q-Tc and Q-oTc intervals increased in length as the ionized calcium level fell and correlated statistically with the level of ionized calcium. Prolongation of the Q-Tc interval was not accompanied by other cardiovascular changes. The blood pressure, central venous pressure, cardiac output and pulmonary artery wedge pressure remained stable during operation, even in the presence of ionized calcium levels as low as 0.72 milliequivalent per liter, 0.36 millimole per liter. From these studies, it appears unnecessary to administer exogenous calcium to massively transfused adult patients to improve cardiac function. Since we have no experience with cardiac bypass operations or exchange transfusions in children, we cannot transfer our results to these categories.
|Number of pages
|Surgery Gynecology and Obstetrics
|Published - 1977