Aim: Aim of this study was to elucidate if postoperative neurocognitive function after biological aortic valve replacement (AVR) can be influenced by temperature management during cardiopulmonary bypass (CPB).
Methods: In this prospective randomized study, we measured the effect of mild hypothermic (32 °C, N.=30) vs. normothermic (37 °C, N.=30) CPB on neurocognitive function. All patients underwent elective isolated biological AVR (mean age 67 ± 8 years, mean additional EuroSCORE 5.6 ± 2.4). Neurocognitive function was objectively measured by means of objective P300 auditory-evoked potentials before surgery, one week and four months after surgery. Clinical data and outcome were monitored.
Results: P300 evoked potentials were comparable between patients operated with mild hypothermic (370 ± 30 ms) and normothermic CPB (373 ± 32 ms) before surgery (P=0.85). P300 peak latencies were prolonged (=impaired) in patients operated with normothermic (402 ± 29, P<0.0001) as well as with mild hypothermic CPB (405 ± 30 ms, P<0.0001) one week after surgery. Even four months after surgery, still impairment of P300 peak latencies could be documented in either patients operated with normothermic (394 ± 28 ms) and mild hypothermic CPB (400 ± 33 ms,) in repeated measures analysis of variance (P=0.042). Group comparison revealed no difference between patients operated with normothermic and mild hypothermic CPB at one week (P=0.54) and four months (P=0.67) after surgery. Clinical data as well as postoperative adverse events were comparable between the two groups.
Conclusion: Normothermic temperature management during CPB is non-inferior to hypothermic in means of neuroprotection. Since patients after biological aortic valve replacement show a subclinical but measurable cognitive deficit up to four months after surgery, other factors have to be addressed to add further benefit to the extremely good results of open biological AVR.