Neurologic monitoring on cardiopulmonary bypass: what are we obligated to do?

Improving survival from congenital cardiac repairs using cardiopulmonary bypass has appropriately shifted focus to neurologic outcomes. Hypoxic-ischemic mechanisms are the major cause of neurologic injury in neonatal cardiac surgery, and modifications of techniques of cardiopulmonary bypass can affect organ oxygen delivery and the propensity to injury both during and after surgery. Through successive refinements in the techniques of cardiopulmonary bypass, the risk factors for hypoxic-ischemic injury have been reduced, but not eliminated. The application of specific monitoring to enhance detection of hypoxic conditions associated with neurologic injury would both allow intervention on individual patients and drive refinements in strategies to further reduce risk. Specific neurologic monitoring techniques that can be used during cardiopulmonary bypass include near-infrared spectroscopy, transcranial Doppler ultrasonography, and electroencephalographic techniques. Of these, only near-infrared spectroscopy provides a continuous quantitative signal of the physiologic variable most related to injury and most amenable to intervention. This review will advocate wide adoption of near-infrared spectroscopy monitoring throughout the perioperative period, to enhance detection of hypoxic conditions and to drive patient-specific interventions.