An experimental evaluation of continuous normothermic, intermittent hypothermic, and intermittent normothermic coronary perfusion

Abstract

Hedley Brown, A., Braimbridge, M. V., Darracoft, Sally, Chayen, J., and Kasap, H. (1974). Thorax, 29,[38][39][40][41][42][43][44][45][46][47][48][49][50]. An

Experimental study of intermittent crossclamping with fibrillation and myocardial protection: Reduced injury from shorter cumulative ischemia or intrinsic protective effect?

“…Marked differences exist between the present study, the more recent clinical studies, [5][6][7][8][9][10][11] and previous experimental and clinical investigations, [22][23][24][25] in which a loss of cardiac protection was demonstrated when intermittent crossclamping (global ischemia) was used. These differences involve the relative durations of ischemia and reperfusion that were used; when repeated episodes of ischemia of around 10 to 20 minutes in duration were interspersed with reperfusion durations of only 3 to 5 minutes, poor cardiac protection was observed.…”

“…A growing body of evidence suggests that the duration and number of cycles of ischemia and reperfusion necessary to confer protection may vary between species and between the end points assessed. 28 In studies in which the time ratio of ischemia to reperfusion is high (such as was the case in previous studies [22][23][24][25] ), any potential benefit that might have occurred as a result of ischemic preconditioning was not seen. In fact, this high ratio, together with the longer total ischemic time, caused severe myocardial injury.…”

Myocardial protection during revascularization for myocardial ischemia

“…This was true for both contractile function and metabolic activity. Brown et al [48] examined the effects of multiple ischemic arrests of 10 minutes with 3-minute reperfusions both at normothermia and at 30~ Unfortunately, the number of such arrests performed was excessive compared with clinical application, but the researchers concluded that significant injury occurred at normothermia with less injury at 30~ Most recently, Smith et al [36] showed impairment of function following 5-minute occlusions in working dog hearts that worsened during a 30-minute reperfusion period. I have been unable to find a report of an experiment that parallels absolutely the clinical use of this technique.…”

Protective effect of methylprednisolone on ischaemic myocardium assessed by ventricular function.

“…1969;Tyers et al, 1974;MacGregor et al, 1975), and doubling the duration of anoxia without loss of contractility (Enright et al, 1970). But hypothermia may cause oedema of the myocardium and this reduces compliance (Salisbury et al, 1961) and is inferior to continuous normothermic perfusion (Brown et al, 1974). However, continuous perfusion has its hazards also (Shaw et al, 1962;Blackstone et al, 1968;Brown et al, 1969).…”