Brain damage following low flow cardiopulmonary bypass in pigs

Abstract

Reduction of pump flow during cardiopulmonary bypass (CPB) reduces the formation of microemboli and trauma to the blood components, reduces both rewarming of the heart and the noncoronary collateral flow, and improves surgical exposure. Recent studies indicate that a reduction in pump flow, even at normothermia, does not increase the incidence of postoperative cerebral dysfunction. We examined the cerebral consequences of 2 h of normothermic CPB in pigs carried out at pump flows of either 70 ml/kg per min or 50 ml/kg per min, and compared the results with those of a nonperfused control group. We measured the regional cerebral glucose metabolism and the regional capillary diffusion capacity simultaneously in ten different brain regions. Brain morphology, the blood-brain barrier permeability to serum proteins and the regional cerebral water content were also determined in the same animals. Glucose metabolism decreased significantly in both CPB groups (P < 0.001), and significant differences were found between the capillary diffusion capacities of the three groups (P < 0.05), with decreases in eight out of ten brain regions examined in the 50 ml/kg per min group. The results indicate that a reduction of pump flows from 70 ml/kg per min to 50 ml/kg per min is deleterious to the brain, and that a pump flow of 70 ml/kg per min itself has an injurious effect, when normothermic CPB is carried out for 2 h without the use of vasoactive drugs to maintain the blood pressure. Mean arterial blood pressure (MAP) rather than pump flow seemed to determine the adequacy of the cerebral perfusion.

Recognition and Prevention of Neurological Complications in Pediatric Cardiac Surgery

“…Those who have claimed that there is no effect of changing pump flow have studied adults and have reduced pump flow no lower than half of the calculated full requirement. It has been argued that the reduction in CBF is actually related to the reduction in blood pressure that usually occurs in parallel rather than to decreased pump flow per se [121,168,200], and there is some evidence that the capacity of the cerebral circulation to vasodilate is reduced at mean arterial pressures below 40 mmHg during CPB [51]. From a practical point of view, in children undergoing CPB, CBF is reduced at low pump flow.…”

The Neurovascular Unit: Effects of Brain Insults During the Perinatal Period

“…Surgical procedures such as cardiopulmonary bypass (CPB) have also demonstrated potential to cause extensive neonatal BBB compromise, increasing with duration of CPB (Cavaglia et al, 2004). Such compromise is not seen in adult brain tissue (Laursen et al, 1986;Gillinov et al, 1992;Waaben et al, 1994), suggesting an enhanced vulnerability to insults in the developing brain.…”