Cerebral hypoperfusion in immediate postoperative period following coronary artery bypass grafting, heart valve, and abdominal aortic surgery

Perioperative levels of jugular bulb oxyhaemoglobin saturation (Sj(O2)) and lactate concentration (Lj), and postoperative duration of Sj(O2) <50% were compared between patients undergoing coronary artery bypass grafting (CABG ) (n=86), heart valve (n=14) and abdominal aortic (n=16) surgery. Radial ar tery and jugular bulb blood samples were aspirated after induction of anaes thesia, during re-warming on cardiopulmonary bypass (CPB) (36<degrees>C), o n arrival in the intensive care unit (ICU) and, subsequently, at 1, 2 and 6 h after ICU admission. Most patients having heart surgery were hypocapnic at 36 degreesC on CPB. Following CABG and heart valve surgery, many patient s were hypocapnic whereas after abdominal aortic surgery, most were hyperca pnic. During CPB and postoperatively, Sj(O2) and Lj were significantly corr elated to Pa-CO2 and the arterial concentration of lactate (La) respectivel y (P<0.05). After correction for arterial carbon dioxide tension (Pa-CO2) a nd La, there were no significant changes in Sj(O2) or Lj on CPB. Postoperat ively, having corrected for Pa-CO2, there were significant effects on Sj(O2 ) over all groups as a result of time from surgery (P<0.001) and its intera ction with operation type (P<0.001). Following correction for La, there wer e no postoperative effects on Li. No significant differences (P=0.2) in dur ation of Sj(O2) <50% existed between patients undergoing CABG (1054 (82) mi n), abdominal aortic (893 (113) min) and heart valve (1073 (91) min) surger y. The lack of significant reciprocal effects on Lj combined with the frequ ency of hypocapnia and strong influence of Pa-CO2 on Sj(O2), suggest that S j(O2) <50% during CPB and after cardiac surgery represents hypoperfusion as a consequence of hypocapnia rather than cerebral ischaemia.