One of the key elements of intraoperative myocardial protection is maintaining myocardial temperature below 20° C during ischemic arrest; however, many diverse techniques have been advocated to achieve this goal. One hundred and thirteen patients undergoing myocardial revascularization with one period of ischemic arrest were randomized: group A (n = 52) received continuous (150 to 200 cc/min) profound (4° C) topical hypothermia and group B (n = 61) received identical topical hypothermia plus one initial 500 cc aortic root bolus of cold (4° C) hyperkalemic cardioplegic solution. Perfusion technique was identical for both groups. The two groups were statistically indistinguishable when 30 preoperative and intraoperative characteristics were compared, including the distribution and number of vessels diseased, degree of left ventricle dysfunction, average number of coronary artery bypass grafts, aortic crossclamp times, and cardiopulmonary bypass times. Myocardial septal temperature (° C ± SD) was measured following each distal anastomosis. For group A the values were 29.6 ± 2.7° C for the first anastomosis, 24.4 ± 2.7° C for the second anastomosis, 20.8 ± 2.57° C for the third anastomosis, and 21.5 ± 3.3° C for the fourth anastomosis (p < 0.001). For group B the values were 18.7 ± 4.2° C for the first anastomosis, 17.5 ± 2.9° C for the second anastomosis, 16.7 ± 3.1° C for the third anastomosis, and 16.7 ± 3.1° C for the fourth anastomosis (p < 0.001). These data show that midseptal myocardial temperature can be reliably maintained below 20° C for up to 1 hour of ischemic arrest in patients undergoing coronary artery bypass grafting after one bolus of cold cardioplegia if: (1) perfusion flow and pressure are lowered, (2) venous drainage is maximized, and (3) supplemental topical hypothermia is assiduously carried out. Furthermore, myocardial temperature in group B was reduced more rapidly and remained significantly lower than that in group A. This simplified technique provides effective myocardial cooling without the complexities of multidose cardioplegia or profound systemic hypothermia.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine