Assessment of myocardial oxygen consumption during hypothermic perfusion on arrested heart with perfluorochemical and blood cardioplegia
Tamura, K.
Nihon Kyobu Geka Gakkai 37(4): 612-621
1989
ISSN/ISBN: 0369-4739 PMID: 2768936 Document Number: 328062
Perfluorochemicals (PFC) have been utilized attempting to improve the myocardial protective effect of hypothermic cardioplegia (CP). This study was performed to evaluate the efficacy of PFC against blood in oxygen utilization under hypothermic continuous perfusion of chemically arrested heart and to estimate the maximum ocygen consumption (max, M.ovrhdot.VO2) under unlimited oxygen delivery. Canine hearts isolated hemodynamically were perfused continuously using either PFC-CP or blood CP. In experiment A (n=8 in PFC-CP, 7 in blood-CP), perfusion temperature was dropped from 25 to 4.degree.C at a constant perfusion pressure of 40 mmHg at aortic root. M.ovrhdot.VO2 showed gradual falls as temperature dropped in both groups, and significant difference in M.ovrhdot.VO2 between two groups was obtained at 10.degree.C (PFC-CP 15.0 .+-. 6.5 (SD), blood-CP 9.7 .+-. 4.3 .mu.l/min/g dry wt, p < 0.05), and 4.degree.C (PFC-CP 11.3 .+-. 3.7, blood-CP 7.6 .+-. 3.3 .mu.l/min/g dry wt, p < 0.05). There was no significant difference in M.ovrhdot.VO2 between two groups at 25.degree. C (PFC-CP 24.6 .+-. 3.5, blood-CP 24.0 .+-. 6.6 .mu. l/min/g dry wt) and 20.degree. C (PFC-CP 19.9 .+-. 4.7, blood-CP 18.6 .+-. 4.9 .mu.l/min/g dry wt). In experiment B, the perfusion temperature was kept constant at either 20.degree.C (n=6 in PFC-CP, 6 in blood CP) or 4.degree.C (n=8 in PFC-CP, 7 in blood-CP), and oxygen delivery was increased until the plateay in M.ovrhdot.VO2 was obtained by increasing the perfusion flow. The asymptote in a hyperbolic realtion between oxygen delivery and M.ovrhdot.VO2 was estimated and considered as max M.ovrhdot.VO2. At 20.degree.C, max M.ovrhdot.VO2 was 20.4 .mu.l/min/g dry wt with PFC-PC and 21.4 .mu.l/min/g dry wt with blood -CP, without significant difference. At 4.degree.C, max M.ovrhdot.VO2 was significantly higher (p < 0.05) in PFC-CP (20.8 .mu.l/mi/g dry wt) than blood-CP (13.9 .mu.l/min/g dry wt). In conclusion, there seems no significant fall in maxM.ovrhdot.VO2 below 20.degree.C under unlimited oxygen delivery by PFC-CP and the superiority in oxygen utilization by PFC-CP can be obtained at the myocardial temperature less than 20.degree.C.