Postoperative cognitive dysfunction and cerebral tissue oxygenation : Can oxygenation predict cognitive outcome?

Background: Coronary artery bypass grafting (CABG) is a surgical procedure that is used in patients with coronary artery disease. Nowadays it can be performed without a cardiopulmonary bypass apparatus, also called off-pump CABG. It is commonly thought that off-pump CABG causes less postoperative complications when compared to on-pump CABG. However, little evidence supports this assumption. Postoperative cognitive dysfunction (POCD) is a common complication in patients after major cardiac surgery. Objective: To determine whether there is a difference in the incidence of POCD between on- and off-pump CABG surgery by using CogState cognitive function tests and relate these results to brain oxygenation. Methods: We analyzed 34 patients (31 men (91.2%) and mean [SD] age of 64 [±9] years) who were scheduled for a CABG procedure eligible for both on-pump and off-pump. Before surgery patients were tested with CogState testing battery for baseline performance. Cerebral oxygenation was measured during the procedure with INVOS and Foresight oximeters. Results: Patients who underwent CABG developed short-term POCD in 50 % of the cases. Although not significant, POCD occurred more often in off-pump patients. Baseline oxygenation, ScO2 after 5 minutes of 100% oxygen, and perioperative cerebral desaturations did not predict nor influence POCD development significantly. However, there is an association that relates high reaction to 100% O2 and large AUC to less cognitive decline after surgery. Conclusion: These findings suggest that off-pump CABG has no benefit above on-pump CABG based on neurocognitive outcome and that high cerebral oxygen reactivity before and during surgery is associated with better cognitive outcome.