Impaired Autoregulation

Mechanism of Injury

• Cerebral autoregulation maintains cerebral blood flow during fluctuations in mean arterial pressure. However, once mean arterial pressure passes above or below the limits of autoregulation, cerebral blood flow becomes pressure dependent.
• In patients undergoing cardiopulmonary bypass, the lower limit of autoregulation can vary widely, from 40 to 90 mmHg.([FOOTNOTE=Joshi B, Ono M, Brown C, et al. Predicting the limits of cerebral autoregulation during cardiopulmonary bypass. Anesthesia and analgesia. 2012;114(3):503-510.],[ANCHOR=],[LINK=])
• Up to 50% of patients demonstrate impaired cerebral autoregulation during cardiac surgery during rewarming.([FOOTNOTE=Joshi B, Brady K, Lee J, et al. Impaired autoregulation of cerebral blood flow during rewarming from hypothermic cardiopulmonary bypass and its potential association with stroke. Anesthesia and analgesia. 2010;110(2):321-328.],[ANCHOR=],[LINK=])

Associated Outcome

• CABG patients with impaired autoregulation are more likely to suffer perioperative stroke than those with intact autoregulation.([FOOTNOTE=Ono M, Joshi B, Brady K, et al. Risks for impaired cerebral autoregulation during cardiopulmonary bypass and postoperative stroke. British journal of anaesthesia. 2012;109(3):391-398.],[ANCHOR=],[LINK=])
• The incidence of delirium is four times higher in patients whose MAP exceeds the upper limit of autoregulation.([FOOTNOTE=Hori D, Brown C, Ono M, et al. Arterial pressure above the upper cerebral autoregulation limit during cardiopulmonary bypass is associated with postoperative delirium. British journal of anaesthesia. 2014;113(6):1009-1017.],[ANCHOR=View Abstract],[LINK=/content/mitg/websites/languagemasters/emea/en-gb/support/clinical-evidence.html?id=883105])
• Ono et al. determined that the time and magnitude of blood pressure below the threshold of cerebral autoregulation was independently associated with major morbidity and mortality.([FOOTNOTE=Ono M, Brady K, Easley RB, et al. Duration and magnitude of blood pressure below cerebral autoregulation threshold during cardiopulmonary bypass is associated with major morbidity and operative mortality. The Journal of thoracic and cardiovascular surgery. 2014;147(1):483-489.],[ANCHOR=],[LINK=])