Background: In addition to the known pre- and intraoperative risk factors for brain injury in infants undergoing corrective surgery of congenital heart defects, alteration of cerebral oxygenation and hemodynamics during the early postoperative period could be a contributing factor. Continuous monitoring of regional cerebral hemoglobin saturation (rSaO2) by near-infrared spectroscopy (NIRS) which correlates with cerebral venous blood saturation determined by invasive methods may provide non-invasive and bedside information on cerebral oxygen supply and consumption in critically ill infants. The aim of the study was to measure continuously the change in rSaO2 immediately after cardiac surgery involving hypothermic cardiopulmonary bypass(CPB) in young infants.

Methods: Continuous measurements of rSaO2 by means of NIRS (INVOS 3100A) were performed in 17 infants (age 3.7±2.5 monthes) during the first 72 postoperative hours after correctiv cardiac surgery. The sensor with a light source and superficial and deep receiver was placed in standardized localisation at the temporal head side. Arterial blood gases and other hemodynamic parameters were simultaneously registered. Cardiac surgery was performed using full-flow CPB (120-150 ml/kg/min) with moderate hypothermia(rectal temp. 20±4). Intraoperative management of acide-base status was used according to the alpha-stat method.

Results: There were significant lower values of rSaO2 (p<0.05) independent of the arterial oxygen tension (pO2) during the first 24 postoperative hours (table, mean±SD). No relationship was found between the rSaO2 and change in pCO2 and mean arterial blood pressure.

Table 1
Full size table

Conclusion: The significantly lower rSaO2 independent of a stable pO2 during the early postoperative period may indicate an alteration of regional brain oxygenation due to persistent higher brain oxygen demand and utilization after hypothemic CPB. Optimal oxygenation and cardiac-output immediately after surgery is necessary to avoid possible silent cerebral hypoxic events during this vulnerable phase.