THE RELATION BETWEEN PUMP FLOW-RATE AND PULSATILITY ON CEREBRAL HEMODYNAMICS DURING PEDIATRIC CARDIOPULMONARY BYPASS

Objectives: Neurologic impairment, at least partly ischemic in origin, has been reported in up to 25% of infants undergoing cardiopulmonary bypass, with or without circulatory arrest, Controversy continues abou t the effect of pump flow, pulsatile or nonpulsatile, on the brain and in particular on cerebral blood flow. This study examines the relatio nship between pump flow rate and cerebral hemodynamics during pulsatil e and nonpulsatile cardiopulmonary bypass. Method: Near-infrared spect roscopy was used to determine cerebral blood flow and cerebral blood v olume (measured as concentration change) in a randomized crossover stu dy. Pulsatile and nonpulsatile flow were used for six 5-minute interva ls at each of three different pump flow rates (0.6, 1.2, and 2.4 L.m(2 ).min(-1)) in 40 patients, median age 2 months (range 2 weeks to 20 ye ars 5 months), The relations between pulsatile flow, pump flow rate, c erebral blood flow, hemoglobin concentration change (cerebral blood vo lume), mean arterial pressure, arterial carbon dioxide tension, and he matocrit value were prospectively examined by means of multivariate an alysis. Results: Cerebral blood flow decreased 36% per L.m(-2).min(-1) decrease in pump flow rate and was associated with changes in mean ar terial pressure but did not differ according to pulsatility. Change in hemoglobin concentration was unrelated to changes in pulsatility of p ump flow. Conclusion: Cerebral blood flow is related to pump flow rate . Pulsatile flow delivered with a Stockert pump does not increase cere bral blood flow or alter hemoglobin concentration during cardiopulmona ry bypass in children.