Comparison of neurologic outcome after deep hypothermic circulatory arrestwith alpha-stat and pH-stat cardiopulmonary bypass in newborn pigs

Objective: Deep hypothermic circulatory arrest for neonatal heart surgery p oses the risk of brain damage. Several studies suggest that pH-stat managem ent during cardiopulmonary bypass improves neurologic outcome compared with alpha-stat management. This study compared neurologic outcome in a surviva l piglet model of deep hypothermic circulatory arrest between alpha-stat an d pH-stat cardiopulmonary bypass, Methods: Piglets were randomly assigned to alpha-stat (n = 7) or pH-stat (n = 7) cardiopulmonary bypass, cooled to 19 degreesC brain temperature, and subjected to 90 minutes of deep hypothermic circulatory arrest. After bypas s rewarming/reperfusion, they survived 2 days. Neurologic outcome was asses sed by neurologic performance (0-95, 0 = no deficit and 95 = brain death) a nd functional disability scores, as well as histopathology. Arterial pressu re, blood gas, glucose, and brain temperature were recorded before, during, and after bypass. Results: All physiologic data during cardiopulmonary bypass were similar be tween groups (pH-stat vs alpha-stat) except arterial pH (7.06 +/- 0.03 vs 7 .43 +/- 0.09, P < .001) and arterial PCO2 (98 <plus/minus> 8 vs 36 +/- 8 mm Hg, P < .001). No differences existed in duration of cardiopulmonary bypas s or time to extubation. Performance was better in pa-stat versus alpha-sta t management at 24 hours (2 <plus/minus> 3 vs 29 +/- 17, P = 0.004) and 48 hours (1 +/- 2 vs 8 +/- 9, P = .1). Also, functional disability was less se vere with pH-stat management at 24 hours (P = .002) and 48 hours (P = .053) . Neuronal cell damage was less severe with pH-stat versus alpha-stat in th e neocortex (4% +/- 2% vs 15% +/- 7%, P < .001) and hippocampal CA1 region (11% <plus/minus> 5% vs 33% +/- 25%, P = .04), but not in the hippocampal C A3 region (3% +/- 5% vs 16% +/- 23%, P = .18) or dentate gyrus (1% +/- 1% v s 3% +/- 6%, P = .63). Conclusions: pH-stat cardiopulmonary bypass management improves neurologic outcome with deep hypothermic circulatory arrest compared with alpha-stat b ypass. The mechanism of protection is not related to hemodynamics, hematocr it, glucose, or brain temperature.