Reduced lactate washout from the myocardium after combining St. Thomas I type cardioplegia with topical cooling of the heart. Myocardial oxygenation and performance after cardioplegia in coronary artery bypass grafting patients.

The myocardial oxygen extraction was diminished with a resulting coronary sinus blood oxygen saturation of 48 +/- 5 (SEM) %, as compared to the pre-bypass control level of 30 +/- 1%, two minutes after the ischaemic period in St. Thomas I type cardioplegia (CPL) with topical cooling of the heart during a coronary bypass operation. The myocardial oxygen extraction returned to prebypass levels after ten minutes of reperfusion following ischaemia and remained so after the bypass. The postischaemic myocardial lactate washout of the CPL-patients was compared to that of another group of coronary surgical patients, in whom intermittent ischaemia and topical cooling (IITC) were used for myocardial protection. It was found that the lactate washout two minutes after the single ischaemic period in the CPL-patients was far less than the lactate washout two minutes after each ischaemic period in the IITC-group. The greatest arterial-coronary sinus lactate difference in the IITC-group was -1.7 +/- 0.2 mmol/l and in the CPL-group -0.7 +/- 0.2 mmol/l. Cardiac performance (assessed by the CI-PCWP relationship) which was moderately depressed by the anaesthesia and surgery before bypass, returned gradually to the control level within 20 hours after operation. The present study shows that no apparent postischaemic abnormality in myocardial oxygen utilization develops when single dose cardioplegia, together with topical cooling of the heart, is used for myocardial protection, and that the accumulation of myocardial lactate during ischaemia is less during cardioplegia with topical cooling of the heart than during intermittent ischaemic with topical cooling for coronary artery bypass grafting operations.