European Journal of Cardio-Thoracic Surgery, Vol 8, 493-498, Copyright © 1994 by European Association for Cardio-thoracic Surgery
Influence of systemic hypothermia on systolic and diastolic functional recovery after continuous warm antegrade blood cardioplegia
RW Landymore, A Marble, A Trillo, G Faulkner, P Chaisson, M Islam and J Fris
Department of Surgery, Dalhousie University, Halifax, Nova Scotia, Canada.
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.
