Non-invasive cerebral oximetry monitoring during cardiopulmonary bypass in congenital cardiac surgery: a starting point

Introduction: Non-invasive cerebral monitoring with the INVOS cerebral oximeter is an accepted good indicator of cerebral metabolism. In recent years, it has been used in the monitoring of patients who underwent cardiac surgery. Herein, we describe the INVOS trend during cardiopulmonary bypass (CPB) in a cohort of patients operated in our institution for congenital heart disease. Patients and methods: Between December 2009 and March 2010, 40 patients (mean age 8.4 years; range 11 days-60 years) underwent cardiac surgical procedures using CPB. Values of INVOS cerebral parameter, pH, oxygen saturation, and CO2 level were collected pre CPB, during cooling, re-warming and weaning, and post CPB. INVOS parameters were evaluated according to CPB priming, age and preoperative oxygen saturation. Results: Patients were divided according to CPB priming (haematic vs clear), age (≤1 vs >1 year of age) and oxygen saturation (≤92% vs >92%). During the operations, the trend demonstrated a reduction in INVOS value at the institution of CPB and a further reduction during the cooling phase in all groups.This has been correlated to the loss of pulsatile flow. However, the value recovered during re-warming, weaning and CPB discontinuation. Cyanotic patients presented a lower cerebral oximetry compared to acyanotic patients during the whole CPB period. Between age and priming groups, we noticed a statistical difference in cerebral oximetry, with a lower value in the younger patients and in the haematic priming group. This might be interrelated because all patients younger than 1 year old always received haematic CPB priming. Conclusions: We demonstrated that cerebral oximetry decreases with the loss of pulsatile flow regardless of the mean arterial pressure and, furthermore, is not directly related to the haematocrit value in patients with reduced pulmonary blood flow.