Risks for impaired cerebral autoregulation during cardiopulmonary bypass and postoperative stroke

Ono M et al. – Impaired cerebral blood flow (CBF) autoregulation occurs in 20% of patients during cardiopulmonary bypass (CPB). Patients with impaired autoregulation are more likely than those with functional autoregulation to have perioperative stroke. Non–invasive monitoring autoregulation may provide an accurate means to predict impaired autoregulation.

Methods

• Two hundred and thirty-four patients were monitored with transcranial Doppler and NIRS.
• A continuous, moving Pearson's correlation coefficient was calculated between mean arterial pressure (MAP) and cerebral blood flow (CBF) velocity, and between MAP and NIRS data, to generate the mean velocity index (Mx) and cerebral oximetry index (COx), respectively.
• Functional autoregulation is indicated by an Mx and COx that approach zero (no correlation between CBF and MAP); impaired autoregulation is indicated by an Mx and COx approaching 1.
• Impaired autoregulation was defined as an Mx≥0.40 at all MAPs during CPB.

Results

• Twenty per cent of patients demonstrated impaired autoregulation during CPB.
• Based on multivariate logistic regression analysis, time-averaged COx during CPB, male gender,paco2 , CBF velocity, and preoperative aspirin use were independently associated with impaired CBF autoregulation.
• Perioperative stroke occurred in six of 47 (12.8%) patients with impaired autoregulation compared with five of 187 (2.7%) patients with preserved autoregulation (P=0.011).

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