Superior cerebral protection with profound hypothermia during circulatory arrest.
ABSTRACT The optimal temperature for cerebral protection during hypothermic circulatory arrest is not known. This study was undertaken to test the hypothesis that deeper levels of cerebral hypothermia (< 10 degrees C) confer better protection against neurologic injury during prolonged hypothermic circulatory arrest ("colder is better"). Twelve male dogs (20 to 25 kg) were placed on closed-chest cardiopulmonary bypass via femoral artery and femoral/external jugular vein. Using surface and core cooling, tympanic membrane temperature was lowered to 18 degrees to 20 degrees C (deep hypothermia, n = 6) or 5 degrees to 7 degrees C (profound hypothermia, n = 6). After 2 hours of hypothermic circulatory arrest, animals were rewarmed to 35 degrees to 37 degrees C on cardiopulmonary bypass. All were mechanically ventilated and monitored in an intensive care unit setting for 20 hours. Neurologic assessment was performed every 12 hours using a species-specific behavior scale that yielded a neurodeficit score ranging from 0% to 100%, where 0 = normal and 100% = brain dead. After 72 hours, animals were sacrificed and examined histologically for neurologic injury. Histologic injury scores were assigned to each animal (range, 0 [normal] to 100 [severe injury]). At the end of the observation period, profoundly hypothermic animals had better neurologic function (neurodeficit score, 5.7% +/- 4.0%) compared with deeply hypothermic animals (neurodeficit score, 41% +/- 9.3%; p < 0.006). Every animal had histologic evidence of neurologic injury, but profoundly hypothermic animals had significantly less injury (histologic injury score, 19.2 +/- 1.2 versus 48.3 +/- 1.5; p < 0.0001).
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ABSTRACT: Profound hypothermia (,5°C) may afford better neurologi- cal protection after circulatory arrest; however, there are the- oretical concerns related to microcirculatory sludging of blood components at these ultra-low temperatures. We hy- pothesized that at temperatures ,5°C, complete blood re- placement results in superior neurological outcome. Twelve Yorkshire pigs (30 kg) underwent thoracotomy, cardiopul- monary bypass (CPB), and were randomly assigned to one of three target hematocrits during circulatory arrest: 0%, 5%, 15%. Hextend® (6% hetastarch in a balanced electrolyte ve- hicle) was used for the CPB prime and as an exchange fluid. Animals were cooled to a temperature ,5°C, underwent 1-h circulatory arrest, and were warmed to 35°C with adminis- tration of blood to increase the hematocrit to .25% before separation from CPB. The primary outcome, peak postoper- ative neurobehavioral score, was compared between groups. The 0% group (mean 6 sd) had significantly (P , 0.02) better neurobehavioral scores than the 5% and 15% groups (6.0 6 2.9 vs 1.3 6 1.0 and 1.5 6 0.6) respectively. Other variables (e.g., intracranial pressure) were similar be- tween groups. In a porcine model of profound hypothermia (,5°C) and circulatory arrest, complete blood replacement resulted in superior neurological outcome. This finding sug- gests that at ultralow temperatures, the presence of some blood component (e.g., erythrocytes, leukocytes) may be deleterious.Anesthesia & Analgesia 01/2001; 93(6):329-334. DOI:10.1097/00000539-200102000-00008 · 3.42 Impact Factor
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ABSTRACT: The thoracic aorta, thoraco-abdominal aorta, or aortic arch surgeries, especially when performed on profound hypothermia and circulatory arrest (PHCA), have a high incidence of cardiac complications. The purpose of this study was to determine cut-off values for cardiac troponin I in diagnosis of cardiac complications in patients undergoing such surgery. We prospectively studied 52 consecutive patients divided into two groups: group I, ascending aorta or aortic arch repair via sternotomy and group II, thoracic aortic aneurysm repair. In patients without cardiac complication, peak for cTnl was observed on D1. Cut-off values of cTnl were 12.2 μg L−1 in sternotomy group, and higher in group II (20.5 μg L−1). These results suggest that the absence of cardioplegia, difficult to achieve via a thoracotomy, is probably responsible for the dramatic increase in cTnl cut-off values in group II.Immuno-analyse & Biologie Spécialisée 07/1999; 14(4):237-239. DOI:10.1016/S0923-2532(99)80058-1 · 0.11 Impact Factor