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Normothermic cardiopulmonary bypass is beneficial for cognitive brain function after coronary artery bypass
1Department of Cardiothoracic Surgery, University of Vienna, Währinger Gürtel 18-20 A-1090, Vienna, Austria. michael.grimm@akh-wien.ac.at
Insights
Mild hypothermia during cardiopulmonary bypass (CPB) may impair cognitive brain function, as indicated by P300 auditory-evoked potentials. Normothermic CPB did not show significant cognitive impairment in patients undergoing coronary artery bypass grafting.
Area of Science:
- Cardiovascular Surgery
- Neuroscience
- Anesthesiology
Background:
- Cardiopulmonary bypass (CPB) temperature management impacts cardiac and neurologic outcomes.
- Uncertainty exists regarding cerebrovascular risk and cognitive dysfunction with normothermic CPB.
Purpose of the Study:
- To compare the effects of mild hypothermic versus normothermic CPB on cognitive brain function.
- To objectively measure cognitive changes using P300 auditory-evoked potentials and psychometric tests.
Main Methods:
- Prospective randomized study of 144 patients undergoing coronary artery bypass grafting.
- Comparison of mild hypothermic (32°C) versus normothermic (37°C) CPB.
- Assessment of cognitive function via P300 auditory-evoked potentials and psychometric tests (trailmaking test A, mini-mental state) pre-surgery and at 1 week and 4 months post-surgery.
Main Results:
- Mild hypothermia group showed prolonged P300 latencies at 1 week and 4 months post-surgery (P<0.001).
- Normothermic CPB group did not exhibit significant P300 latency changes.
- Psychometric tests did not differentiate cognitive changes between groups. Five patients died postoperatively (3 mild hypothermia, 2 normothermia).
Conclusions:
- Mildly hypothermic CPB is associated with more pronounced subclinical cognitive brain function impairment compared to normothermic CPB.
- P300 auditory-evoked potentials provide objective evidence of cognitive changes after CPB.
- Further research may be needed to fully elucidate long-term cognitive effects and optimize CPB temperature strategies.
Background:
Hypothermic and normothermic cardiopulmonary bypass (CPB) have resulted in apparently contradictionary cardiac and neurologic outcome. Cerebrovascular risk and cognitive dysfunction associated with normothermic CPB still remain uncertain.
Materials And Methods:
In a prospective randomized study, we measured the effects of mildly hypothermic (32 degrees C, n=72) vs. normothermic (37 degrees C, n=72) CPB on cognitive brain function. All patients received elective coronary artery bypass grafting (mean age 62.1+/-6.3 years, mean ejection fraction 60.4+/-13%). Cognitive brain function was objectively measured by cognitive P300 auditory-evoked potentials before surgery, 1 week and 4 months after surgery, respectively. Additionally, standard psychometric tests ('trailmaking test A', 'mini-mental state') were performed and clinical outcome was monitored.
Results:
Patients, operated with mild hypothermia, showed a marked impairment of cognitive brain function. As compared with before surgery (370+/-45 ms), P300 evoked potentials were prolonged at 1 week (385+/-37 ms; P<0.001) and even at 4 months (378+/-34 ms, P<0.001) after surgery, respectively. In contrast, patients operated with normothermic CPB, did not show an impairment of P300 peak latencies (before surgery 369+/-36 ms, 1 week after surgery 376+/-38 ms, n.s.; 4 months after surgery 371+/-32 ms, n.s.). Group comparison revealed a trend towards prolonged P300 peak latencies in the patient group undergoing mildly hypothermic CPB (P=0.0634) 1 week after surgery. Four months postoperatively, no difference between the two groups could be shown (P=n.s.) Trailmaking test A and mini mental state test failed to discriminate any difference. Five patients died (mild hypothermia n=3, normothermia n=2) postoperatively (cardiac related n=3, sepsis n=2). None of the patients experienced major adverse cerebrovascular events.
Conclusions:
Objective cognitive P300 auditory evoked potential measurements indicate, that subclinical impairment of cognitive brain function is more pronounced in patients undergoing mildly hypothermic CPB as compared with normothermic CPB for CABG.