Landymore R W, Marble A, Trillo A, Faulkner G, Chaisson P, Islam M, Fris J
Department of Surgery, Dalhousie University, Halifax, Nova Scotia, Canada.
Eur J Cardiothorac Surg. 1994;8(9):493-8; discussion 499. doi: 10.1016/1010-7940(94)90021-3.
Experimental observations in our laboratory indicate that myocardial recovery is similar following warm or cold antegrade blood cardioplegia when the core temperature is maintained at 37 degrees C. To determine the effects of hypothermia on myocardial recovery, 15 adult mongrel dogs were randomized to normothermic or hypothermic bypass (28 degrees C) during 60 min of continuous warm antegrade blood cardioplegia. The hypothermic group was rewarmed after releasing the aortic cross-clamp and bypass was discontinued at 30 min in both groups. Myocardial recovery was assessed at 60, 90, and 120 min after the arrest. Core temperature was maintained in the normothermic group but gradually decreased after bypass in the hypothermic group, reaching a low of 33.8 +/- 1 degrees C at 120 min. Myocardial functional recovery was preserved after normothermic bypass. The decrease in core temperature, however, that was observed after systemic hypothermia, was paralleled by significant decreases in the maximum rate of left ventricular pressure rise (dp/dt), the maximum elastance of the left ventricle, and preload recruitable stroke work. Diastolic function decreased slightly, but not significantly, during reperfusion following systemic hypothermia but was unaltered after normothermic bypass. Myocardial oxygen consumption was unchanged in both groups. Myocardial ultrastructure was preserved after normothermic bypass. In contrast, cellular oedema and mild ultrastructural changes were evident after systemic hypothermia. We therefore conclude that the use of systemic hypothermia during bypass is associated with lower core temperatures during early recovery which results in impaired functional recovery.
我们实验室的实验观察表明，当核心体温维持在37摄氏度时，温血或冷血顺行性心脏停搏后的心肌恢复情况相似。为了确定低温对心肌恢复的影响，15只成年杂种犬在60分钟持续温血顺行性心脏停搏期间被随机分为常温或低温体外循环组（28摄氏度）。低温组在松开主动脉阻断钳后复温，两组均在30分钟时停止体外循环。在心脏停搏后60、90和120分钟评估心肌恢复情况。常温组维持核心体温，而低温组在体外循环后核心体温逐渐下降，在120分钟时降至33.8±1摄氏度的低点。常温体外循环后心肌功能恢复得以保留。然而，全身低温后观察到的核心体温下降，与左心室压力上升最大速率（dp/dt）、左心室最大弹性和前负荷可募集搏功的显著下降平行。全身低温后的再灌注期间舒张功能略有下降，但不显著，而常温体外循环后舒张功能未改变。两组的心肌耗氧量均未改变。常温体外循环后心肌超微结构得以保留。相比之下，全身低温后细胞水肿和轻度超微结构改变明显。因此，我们得出结论，体外循环期间使用全身低温与早期恢复期间较低的核心体温相关，这导致功能恢复受损。
