Blood cardioplegia serves as a bicarbonate donor to the myocardium during ischemia: Effects of anoxia and hypercapnia on acid-base characteristics of blood cardioplegic solution

摘要

Objectives: We investigated the alterations of acid-base characteristics of the blood cardioplegia (BCP) solution during aortic cross-clamping in hearts arrested with BCP and during in vitro-simulated ischemia. Methods: Following aortic cross-clamping, the hearts of 40 patients undergoing cardiac surgery were intermittently infused with an 18°C BCP solution and finally with a 34°C BCP solution prior to aortic cross-clamp release. We measured the pH, partial CO 2 pressure (pCO 2), [HCO 3 -], and [Cl -] of the coronary sinus effluent in the final BCP solution. The BCP solution was assessed under in vitro gassing at 34°C with 95% N 2 + 5% CO 2 (n = 6), 50% N 2 + 50% CO 2 (n = 3), or 100% CO 2 (n = 6). Results: The coronary sinus effluent, compared with the preinfusion BCP solution, exhibited a significantly lower pH and a greater pCO 2 with no change in the [HCO 3 -] level. In vitro, the 95% N 2 + 5% CO 2 gassing (simulated hypoxia) group exhibited a slight increase in [HCO 3 -] with no change in pCO 2 or pH whereas the 50% N 2 + 50% CO 2 gassing and the 100% CO 2 gassing (simulated hypoxia and hypercapnia) groups exhibited a significant increase in [HCO 3 -] under high pCO 2-induced acidification. Conclusions: Under anoxia and CO 2 retention during aortic cross-clamping, the BCP solution can be a bicarbonate donor to the myocardium.