EVIDENCE THAT CONTINUOUS NORMOTHERMIC BLOOD CARDIOPLEGIA OFFERS BETTER MYOCARDIAL PROTECTION THAN INTERMITTENT HYPOTHERMIC CARDIOPLEGIA

Objectives-To compare transmyocardial ischaemia and oxidative stress, as well as non-infarction myocardial injury, in patients randomised to intermittent hypothermic cardioplegia or continuous normothermic bloo d-potassium cardioplegia. Design-Prospective randomised trial. Setting -Tertiary cardiac referral centre. Methods-24 patients undergoing elec tive coronary artery bypass surgery were randomised to hypothermic (13 patients, mean (SEM) age 59.5 (2.6) years) or normothermic (11 patien ts, mean (SEM) age 59.7 (3.3) years) cardioplegia. Transmyocardial oxi dative stress and ischaemia were assessed by the difference in plasma concentrations of oxidised glutathione and lactate respectively, from samples taken simultaneously from the coronary sinus and aortic root. Blood samples were taken just before cross clamp application and at in tervals up to 15 min after cross clamp release. Non-infarction myocard ial injury was assessed by measurement of creatine kinase MB isoenzyme activity from peripheral venous blood taken 2 and 18 h after surgery. Results-intermittent hypothermic cardioplegia resulted in a significa nt increase in transmyocardial ischaemia (P < 0.001) and oxidative str ess (P < 0.001). Evidence of significantly increased myocyte damage wa s also present (P < 0.01). No significant corresponding changes were p resent with normothermic cardioplegia. Conclusions-Normothermic blood cardioplegia seems to avoid significant changes in myocardial ischaemi c status and consequent oxidative stress. This study provides direct e vidence that normothermic cardioplegia offers enhanced myocardial prot ection compared with that of hypothermic cardioplegia. Certain subsets of patients may derive more benefit from normothermic cardioplegia, a lthough it is unclear whether this would be the case for all patients.