Background-The advantages of blood cardioplegia include the oxygen-carrying capacity, superior oncotic and buffering properties, and endogenous antioxidants contained in blood. However, the partial dilution of blood in 4:1 (blood:crystalloid) cardioplegic solutions may nullify these advantages and progressively dilute blood during continuous retrograde delivery. This study tested the hypothesis that all-blood (66:1) cardioplegia provides superior myocardial protection compared with dilute (4:1)

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... cardioplegia delivered in a continuous retrograde modality during surgical reperfusion of evolving myocardial infarction. Methods and Results-After 60 minutes of left anterior descending coronary artery (LAD) occlusion, anesthetized canines were placed on cardiopulmonary bypass and randomized to either all-blood cardioplegia (AB group) or dilute blood cardioplegia (Dil group). After cross clamping, arrest was induced with 5 minutes of tepid (30°C) antegrade potassium all-blood or dilute blood cardioplegia and maintained with tepid retrograde coronary sinus cardioplegia for a total of 1 hour. The LAD was released after 30 minutes of arrest, simulating revascularization. The cardioplegia hematocrit for the Dil group was lower than that for the AB group (7Ϯ1% versus 12Ϯ2%, PϽ0.05); at the end of bypass, systemic hematocrit was lower in the Dil group than in the Ab group (15Ϯ1% versus 20Ϯ1%, PϽ0.05). Infarct size (triphenyltetrazolium chloride staining) was comparable between the AB and Dil groups (29.6Ϯ2.9% versus 30.3Ϯ3.9% of area at risk), and there was no difference in area-at-risk myocardium systolic shortening (by sonomicrometry, Ϫ0.3Ϯ1% versus Ϫ0.4Ϯ1%). Tissue edema after bypass tended to be greater in the Dil group compared with the AB group in the heart (82Ϯ0% versus 81Ϯ1%), lung (79Ϯ1% versus 78Ϯ1%), liver (75Ϯ1% versus 74Ϯ0%), and skeletal muscle (76Ϯ1% versus 73Ϯ2%) and was significantly greater in the duodenum (80Ϯ1% versus 79Ϯ1%, PϽ0.05) and kidney (82Ϯ1% versus 79Ϯ1%, PϽ0.05). Postexperimental endothelial function (relaxation of acetylcholine) was impaired in LADs of the AB group versus the Dil group (59Ϯ6% versus 77Ϯ5%, PϽ0.05). Conclusions-Both all-blood cardioplegia and dilute cardioplegia have disadvantages, but these do not have an impact on the pathogenesis of infarct size or recovery of regional contractile function. (Circulation. 2001;104[suppl I]:I-296-I-302.)