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Blood pressure and brain injury in cardiac surgery: a secondary analysis of a randomized trial
Anne G Vedel1,2, Frederik Holmgaard1, Else R Danielsen3
1D epartment of Cardiothoracic Anaesthesiology, Heart Center, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
Insights
Higher mean arterial pressure during cardiac surgery bypass was linked to impaired brain metabolism. This study found decreased grey matter N-acetylaspartate-to-total-creatine ratios, indicating potential ischemic injury, in the high-target group.
Area of Science:
- Neurology
- Cardiovascular Surgery
- Medical Imaging
Background:
- Brain dysfunction is a significant complication following cardiac surgery.
- Maintaining adequate cerebral perfusion pressure during cardiopulmonary bypass (CPB) is crucial for preventing neurological damage.
Purpose of the Study:
- To investigate the impact of different mean arterial pressure (MAP) targets during CPB on cerebral metabolism.
- To assess postoperative changes in cerebral metabolites, specifically the N-acetylaspartate-to-total-creatine ratio in grey matter (GM), as an indicator of ischemic injury.
Main Methods:
- A secondary analysis of the Perfusion Pressure Cerebral Infarcts trial involving 197 cardiac surgery patients.
- Magnetic resonance spectroscopy was used to measure cerebral metabolites (GM and white matter) preoperatively and postoperatively.
- Cognitive function was assessed at multiple time points.
Main Results:
- A postoperative decrease in the GM N-acetylaspartate-to-total-creatine ratio was observed in the high-target MAP group (70-80 mmHg), suggesting potential ischemic changes.
- No significant differences in other metabolite ratios were found in GM or white matter (WM).
- Changes in metabolite ratios did not correlate with new cerebral infarcts, WM lesion scores, or cognitive dysfunction.
Conclusions:
- Higher MAP during CPB was associated with signs of impaired cerebral metabolism, although not reaching the predefined statistical significance level.
- No significant association was found between altered metabolite ratios and subsequent neuroradiological findings or cognitive decline.
Objectives:
Brain dysfunction is a serious complication after cardiac surgery. In the Perfusion Pressure Cerebral Infarcts trial, we allocated cardiac surgery patients to a mean arterial pressure of either 70-80 or 40-50 mmHg during cardiopulmonary bypass (CPB). In this secondary analysis, we compared selected cerebral metabolites using magnetic resonance spectroscopy hypothesizing that a postoperative decrease in occipital grey matter (GM) N-acetylaspartate-to-total-creatine ratio, indicative of ischaemic injury, would be found in the high-target group.
Methods:
Of the 197 patients randomized in the Perfusion Pressure Cerebral Infarcts trial, 55 and 42 patients had complete and useful data from GM and white matter (WM), respectively. Spectroscopies were done preoperatively and on postoperative days 3-6. Cognitive function was assessed prior to surgery, at discharge and at 3 months. We predefined the statistical significance level to be 0.01.
Results:
A postoperative decrease was found in GM N-acetylaspartate-to-total-creatine ratio in the high-target group [mean difference -0.09 (95% confidence interval -0.14 to -0.04), P = 0.014]. No significant differences were found in other metabolite ratios investigated in GM or WM. No significant association was found between changes in metabolite ratios and new cerebral infarcts, WM lesion score or cognitive dysfunction.
Conclusions:
A higher mean arterial pressure during CPB was associated with signs of impaired cerebral metabolism, though not at the predefined significance level of 0.01. No significant association was found between metabolite ratio changes and neuroradiological pathology or change in cognitive function.
Clinical Trial Registration Number:
Clinicaltrials.gov: NCT02185885.
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