[Assessment of myocardial oxygen consumption during hypothermic perfusion on arrested heart with perfluorochemical and blood cardioplegia].

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 oxygen consumption (max MVO2) 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 degrees C at a constant perfusion pressure of 40 mmHg at aortic root. MVO2 showed gradual falls as temperature dropped in both groups, and significant difference in MVO2 between two groups was obtained at 10 degrees C (PFC-CP 15.0 +/- 6.5 (SD), blood-CP 9.7 +/- 4.3 microliters/min/g dry wt, p less than 0.05) and 4 degrees C (PFC-CP 11.3 +/- 3.7, blood-CP 7.6 +/- 3.3 microliters/min/g dry wt, p less than 0.05). There was no significant difference in MVO2 between two groups at 25 degrees C (PFC-CP 24.6 +/- 3.5, blood-CP 24.0 +/- 6.6 microliters/min/g dry wt) and 20 degrees C (PFC-CP 19.9 +/- 4.7, blood-CP 18.6 +/- 4.9 microliters/min/g dry wt). In experiment B, the perfusion temperature was kept constant at either 20 degrees C (n = 6 in PFC-CP, 6 in blood-CP) or 4 degrees C (n = 8 in PFC-CP, 7 in blood-CP), and oxygen delivery was increased until the plateau in MVO2 was obtained by increasing the perfusion flow. The asymptote in a hyperbolic relation between oxygen delivery and MVO2 was estimated and considered as max MVO2. At 20 degrees C, max MVO2 was 20.4 microliters/min/g dry wt with PFC-PC and 21.4 microliters/min/g dry wt with blood-CP, without significant difference. At 4 degrees C, max MVO2 was significantly higher (p less than 0.05) in PFC-CP (20.8 microliters/min/g dry wt) than blood-CP (13.9 microliters/min/g dry wt). In conclusion, there seems no significant fall in maxMVO2 below 20 degrees 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 degrees C.