Relationship of internal jugular venous oxygen saturation and perfusion flow rate in children and adults during normothermic and hypothermic cardiopulmonary bypass.

Introduction: This study was designed to elucidate the trends in cerebral venous oxygen saturation in cyanotics and acyanotics undergoing normothermic and hypothermic cardiopulmonary bypass (CPB) and its relationship to perfusion flow rates.

Methods: Five hundred and forty-eight patients (253 cyanotics) undergoing first surgical correction using CPB were included in this prospective study. One hundred and seventy-two patients underwent surgical correction under normothermic CPB (34-36 degrees C) - group I; 142 patients were operated under moderately hypothermic CPB - group II; and 234 patients were operated under deep hypothermic CPB - group III. The perfusion flow rates were adjusted to maintain the internal jugular venous oxygen saturation (IJVO2) between 70-80% in both cyanotics and non-cyanotics.

Results: The prevalence of preoperative cerebral venous desaturation was 17.4% and 5.1% in cyanotic and acyanotic groups, respectively. All patients undergoing hypothermic CPB had IJVO 2 >75% at the recommended perfusion flow rate. During surgery, 87.2% of group I patients undergoing normothermic CPB and 88.5% of group II and III patients undergoing hypothermic CPB had IJVO 2 <75% during re-warming and required an increased perfusion flow rate to maintain IJVO2 >75%. The cyanotics demonstrated a higher incidence of cerebral desaturation in all three groups. Patients aged <4 years had almost the same prevalence of cerebral desaturation compared to the older patients.

Conclusions: We conclude that patients undergoing normothermic CPB are at greater risk of cerebral desaturation. The cyanotics are at greater risk compared to acyanotics during normothermic CPB and during the re-warming phase of hypothermic CPB and require an individualised increased perfusion flow rate.