The Annals of Thoracic Surgery, Vol 57, 326-331, Copyright © 1994 by The Society of Thoracic Surgeons
Myocardial function is normal after rapid cooling of the in vivo neonatal heart
JS Heinle, AJ Lodge, JR Mault, EG Whitaker and RM Ungerleider
Department of Surgery, Duke University Medical Center, Durham, NC 27710.
Rapid cooling (RC) on cardiopulmonary bypass (CPB) has been reported to be
injurious to the neonatal myocardium when compared with slow cooling (SC).
However, previous studies have been performed on isolated heart
preparations using asanguineous perfusates and may not represent clinically
valid conclusions. In this study, the effect of RC versus SC on post-CPB
cardiac function in an in vivo neonatal heart model using a blood perfusate
was investigated. Thirteen neonatal piglets underwent median sternotomy.
Left ventricular ultrasonic dimension transducers were placed in the minor
and major axis diameters, and an intraventricular micromanometer was
placed. Baseline left ventricular pressure-dimension data were obtained
during transient vena caval occlusion. Animals were then placed on CPB
(blood prime; mean hematocrit, 25%) with the prime temperature at either 18
degrees C (RC) or 37 degrees C (SC) and perfusion cooled either quickly
(RC) or gradually (SC) such that within 2 minutes of cooling the average
myocardial temperature was 23.5 degrees C in the RC group versus 33.8
degrees C in the SC group (p = 0.0001). Animals were cooled to 20 degrees
C, rewarmed to 37 degrees C, and then weaned from CPB. Left ventricular
pressure-dimension data were obtained 30 minutes after CPB and compared
with baseline. The slope (MW) and x-intercept (Vo) of the linear stroke
work-end-diastolic volume relationship were used as load- insensitive
indices of left ventricular function at baseline and after CPB. There was
no statistically significant difference in baseline versus postbypass MW or
Vo in the RC or SC groups.(ABSTRACT TRUNCATED AT 250 WORDS)
