EARLY CEREBRAL FUNCTIONAL OUTCOME AFTER CORONARY-ARTERY BYPASS-SURGERY USING DIFFERENT ACID-BASE MANAGEMENT DURING HYPOTHERMIC CARDIOPULMONARY BYPASS

Background: Cerebral injury can render meaningless an otherwise succes sful cardiac operation. As carbon dioxide management during hypothermi c cardiopulmonary bypass has a major impact on cerebral blood flow dur ing bypass, it may also influence postoperative cerebral function. The objective of this prospective, controlled, double-blind study was to compare the effect of pH-stat (temperature correction of blood gas ana lyses) or alpha-stat (no temperature correction) on brain function. Me thods: Cerebral function was assessed non-invasively using neurologica l examination, a neuropsychological test battery, quantitative electro encephalogram and the cognitive evoked potential P300 preoperatively a nd on postoperative day 7 or 8. Forty-five patients undergoing electiv e aortocoronary bypass grafting in barbiturate/opiate anesthesia were randomised into a pH-stat- (n=23) and an alpha-stat-group (n=22). Memb rane oxygenators with arterial line filtration and non-pulsatile flow at a perfussion pressure of 50-60 mmHg were used throughout. Results: One patient in each group developed a new paresis. Among 49 comparison s of cerebral function parameters, only 3 showed significant differenc es at the 5%-level, i.e. exactly what is expected purely by chance. Th ese differences were too small to be clinically relevant and favored e ither pH-stat (theta-amplitude) or alpha-stat (subtest 3 of syndrome-s hort-test, number of mistakes in aiming). Conclusion: Under the bypass conditions of this study there was no difference in early cerebral fu nctional outcome between pH- or alpha-stat carbon dioxide management d uring hypothermic cardiopulmonary bypass.