IMPROVED TOLERANCE OF THE PEDIATRIC MYOCARDIUM TO BRAIN-DEATH

The occurrence of brain death has been shown to significantly diminish left ventricular function in the adult porcine model. This study exam ined whether the pediatric myocardium is as sensitive as the adult myo cardium to the detrimental effects of brain death in the porcine model . Left ventricular intracavitary pressure and major and minor axis epi cardial dimensions were measured in eleven 1-month old pigs (7.5 to 10 kg) during a vena caval occlusion Brain death was induced in six pigs by acutely ligating the brachiocephalic and left subclavian arteries. The remaining five pigs served as controls. Data were then collected every hour for 6 hours. The plot of the stroke work versus the end dia stolic volume, called the preload recruitable stroke work relationship , was determined from the measured pressure and calculated intracavita ry volume data. The slope of this linear relationship is an index of c ontractility, and the chi intercept (V-o) is an index of diastolic mec hanics. At each hour after instrumentation two vena caval occlusions w ere performed, and the mean slope of the preload recruitable stroke wo rk line was calculated as a percentage of the baseline slope in both t he brain-dead and control group. The mean values from the brain-dead p igs were 118%, 138%, 126%, 154%, 123%, and 87% of the baseline value f or the 6 hours after brain death. The mean control values were 128%, 1 17%, 133%, 123%, 114%, and 111% of baseline for the 6 hours after inst rumentation alone. There was no statistical difference between groups with the rank sum test. The shift in the chi intercept was calculated for each group at each hour as well. The mean group shifts from the ba seline V-o in the brain-dead pigs were 0.97, 2.40, 2.63, 4.86, 5.00, a nd 5.00 ml. The mean control group shifts from the baseline V-o were - 0.63, 2.85, 3.29, 2.76, 2.96, and 2.69 ml. Only at the fourth and fif th hours were there any statistically significant differences between the groups with the rank sum test (p < 0.03). During acute brain death , the pediatric porcine myocardium is significantly more stable than t he adult porcine myocardium, which rapidly declines to 8% of the basel ine slope within 6 hours of brain death. If the mechanism for this tol erance is determined, perhaps it could be applied to the adult populat ion of brain-dead donors to expand the organ supply. We conclude that in the porcine model of brain death, the pediatric myocardium demonstr ates no decremental decline in left ventricular systolic function in c ontrast to the adult myocardium.