THE RELATION BETWEEN ARTERIAL OXYGEN-TENSION AND CEREBRAL BLOOD-FLOW DURING CARDIOPULMONARY BYPASS

Objectives: Neurological impairment occurs in up to 25% of infants und ergoing cardiopulmonary bypass with or without circulatory arrest. Pot ential causes include alterations in cerebral blood flow, hypoxia and embolisation. During cardiopulmonary bypass, arterial oxygen tension i s maintained at levels which under normal conditions cause cerebral va soconstriction; this is a potential mechanism for ischaemia. The aim o f this study was to explore the relation between arterial oxygen tensi on and cerebral blood flow during cardiopulmonary bypass. Methods: Nea r infrared spectroscopy was used to explore the relation between arter ial oxygen tension and cerebral blood flow in 14 patients (median age 8 months; range 1 month to 10 years 11 months). The relations between arterial oxygen tension, arterial carbon dioxide tension, temperature, haematocrit, pump flow rate, mean arterial pressure and cerebral bloo d flow, were examined using multivariate analysis, Results: There was no relation between cerebral blood flow and arterial oxygen tension, b ut a highly significant relation was observed between cerebral blood f low and pump flow rate, with cerebral blood flow decreasing 3.2-fold p er L.m(-2).min(-1) decrease of pump flow rate. Conclusion: There was n o relation between arterial oxygen tension and cerebral blood flow dur ing cardiopulmonary bypass, but low pump flow rate may lead to reduced cerebral blood flow. (C) 1997 Elsevier Science B.V.