Nadir oxygen delivery to the brain as a risk factor for post-operative neurocognitive impairment in patients undergoing coronary artery bypass grafting: A myth or fact

Background

There are many factors that determine the best neurocognitive outcome following cardiac surgery. Optimum oxygen delivery to the tissues has always been the goal to optimum perfusion. Some patients may exhibit neurocognitive impairments in the early postoperative period; that could be easily missed clinically as they are not associated with radiographic evidence of structural brain damage. At this study we aimed to correlate the lowest oxygen delivery levels with incidence of neurocognitive impairment in the early postoperative period by Folstein test.

Methods

A non-randomized, prospective pilot study was designed to correlate the nadir oxygen delivery (DO₂) during CPB with post-operative cognitive impairment. The study included 271 patients of both sexes, an age group of 50–60 years with university level of education, scheduled for elective, isolated CABG for three vessel disease. All patients underwent pre-and post-operative neurocognitive test by a specialized neuropsychiatric doctor.

Results

with a mean nadir DO₂ of 291 mL/min/m², the majority of the patients exhibited “normal” results, with a mean nadir DO₂ of 266 mL/min/m² 92 patients showed mild impairment in their cognitive behavior, while the worst results “moderate” and “severe” were associate with means of 244,200 mL/min/m² successively.

Conclusions

The nadir oxygen delivery is a risk factor for development of post-operative neurocognitive impairment. A level below 260 mL/min/m² is generally associated with higher risk while a level below 220 mL/min/m² carries the worst prognosis.