Myocardial oxygen tension during surgical revascularization. A clinical comparison between blood cardioplegia and crystalloid cardioplegia

Objective: The aim of this study was to assess the effect of cardioplegic solutions on myocardial oxygenation during surgical revascularization. Methods: In 30 patients, randomized to receive crystalloid (CC) or blood (BC) cardioplegia, myocardial oxygen tension was measured continuously by potarography. Results: The two groups were comparable in terms of patients' age, sex, pre-operative ejection fraction, coronary disease, perfusion time, and aorta cross-clamping time. However, the BC group required 22% more of cardioplegic solution to stop electrical activity of the heart. Throughout the pre- and post-cardiac arrest periods, oxygen tension between the two groups was similar. At the end of the observation (4th day), myocardial oxygenation increased over 200% in relation to the values before revascularization. During the first infusion of cardioplegia, oxygen tension in the CC group was lower compared to the BC group (0.1 mmHg vs 1.3 mmHg; P < 0.05) being the only significant difference between the two groups during cardiac arrest. Throughout the cardiac arrest, myocardial oxygen tension was close to zero regardless of the type of cardioplegia used. Post-operatively, addition of oxygen to the respiratory air increased myocardial oxygenation by over 17% resulting in a positive correlation (r = 0.94; P < 0.05) between myocardial oxygen tension and peripheral saturation. Conclusions: In conclusion, the differences in myocardial oxygen tension between the CC and BC groups are trivial. Thus, any potential beneficial effect of blood cardioplegia compared to crystalloid cardioplegia must be due to other circumstances than its oxygen carrying capacity. An important observation is a significant increase in myocardial oxygenation during oxygen supplement to the respiratory air. (c) 2005 Published by Elsevier B.V.