HIGHER HEMATOCRIT IMPROVES CEREBRAL OUTCOME AFTER DEEP HYPOTHERMIC CIRCULATORY ARREST

Background: Various degrees of hemodilution are currently in clinical use during deep hypothermic circulatory arrest to counteract deleterio us theologic effects linked with brain injury by previous reports, Mat erial and methods: Seventeen piglets were randomly assigned to three g roups, Group I piglets (n = 7) received colloid and crystalloid prime (hematocrit < 10%), group II piglets (n = 5) received blood and crysta lloid prime (hematocrit 20%), group III piglets (n = 5) received blood prime (hematocrit 30%), All groups underwent 60 minutes of deep hypot hermic circulatory arrest at 15 degrees C, with continuous magnetic re sonance spectroscopy and near-infrared spectroscopy Neurologic recover y was evaluated for 4 days (neurologic deficit score 0, normal, to 500 , brain death; overall performance category 1, normal, to 5, brain dea th), Neurohistologic score (0, normal, to 5+, necrosis) was assessed a fter the animals were euthanized on day 4, Results: Group I had signif icant loss of phosphocreatine and intracellular acidosis during early cooling (phosphocreatine in group I, 86.3% +/- 26.8%; group II, 117.3% +/- 8.6%; group III, 110.9% +/- 2.68%; p = 0.0008; intracellular pH i n group I, 6.95 +/- 0.18; group II, 7.28 +/- 0.04; group III, 7.49 +/- 0.04; p = 0.0048), Final recovery was the same for all groups, Cytoch rome aa(3) was more reduced in group I during deep hypothermic circula tory arrest than in either of the other groups (group I, -43.6 +/- 2.6 ; group II, -16.0 +/- 5.2; group III, 1.3 +/- 3.1; p < 0.0001). Neurol ogic deficit score was best preserved in group III (p < 0.05 group II vs group III) on the first postoperative day, although this difference diminished with time and all animals were neurologically normal after 4 days, Histologic assessment was worst among group I in neocortex ar ea (group I, 1.33 +/- 0.3; group II, 0.22 +/- 0.1; group III, 0.40 +/- 0.2, p < 0.05, group I vs group II; p 0.0287, group I vs group III). Conclusion: Extreme hemodilution during cardiopulmonary bypass may cau se inadequate oxygen delivery during early cooling, The higher hematoc rit with a blood prime is associated with improved cerebral recovery a fter deep hypothermic circulatory arrest.