Assessment of cerebral oxygenation using near infrared spectroscopy during isovolemic hemodilution in pediatric patients

Abstract

One means of limiting the need for allogeneic blood transfusions is isovolemic hemodilution where blood is removed in the operating room and replaced with isotonic fluids to maintain euvolemia. Although the delivery of oxygen to the tissues is generally maintained by compensatory physiologic mechanisms, there are limited data evaluating tissue oxygenation in actual clinical practice. The current study evaluates the effects of isovolemic hemodilution on cerebral oxygenation using near-infrared spectroscopy (NIRS). NIRS was monitored and isovolemic hemodilution achieved in 12 pediatric patients who ranged in age from 12 to 16 years. After anesthetic induction, isovolemic hemodilution was carried out by phlebotomy and the collection of blood which was replaced with colloid to achieve a final hematocrit of 25–30%. There was no statistically significant change in heart rate, mean arterial pressure or central venous pressure during isovolemic hemodilution. The baseline cerebral oximeter obtained after the induction of anesthesia was 81±8 on the right and 82±7 on the left. At the completion of isovolemic hemodilution, the cerebral saturations were 77±10 on the right and 78±8 on the left. No patient had a decreased in cerebral oxygenation of greater than 10 during isovolemic hemodilution. The greatest decrease in the cerebral oximeter reading during isovolemic hemodilution was 8. Our data provides preliminary evidence supporting the safety of moderate isovolemic hemodilution in a pediatric population. We found that cerebral oxygenation is well maintained by compensatory mechanisms. Modalities such as NIRS to monitor end-organ oxygenation may be particularly valuable in patients with co-morbid disease processes which may affect end organ oxygenation or prevent the compensatory mechanisms that maintain oxygen delivery during anemia.