Cerebral Small Vessel, But Not Large Vessel Disease, Is Associated With Impaired Cerebral Autoregulation During Cardiopulmonary Bypass

METHODS: A retrospective cohort analysis of data from 346 patients undergoing cardiac surgery with CPB enrolled in an ongoing prospectively randomized clinical trial of autoregulation monitoring were evaluated. The study protocol included preoperative transcranial Doppler (TCD) evaluation of major cerebral artery flow velocity by a trained vascular technician and brain magnetic resonance imaging (MRI) between postoperative days 3 and 5. Brain MRI images were evaluated for chronic white matter hyperintensities (WMHI) by a vascular neurologist blinded to autoregulation data. “Large vessel” cerebral vascular disease was defined by the presence of characteristic TCD changes associated with stenosis of the major cerebral arteries. “Small vessel” cerebral vascular disease was defined based on accepted scoring methods of WMHI. All patients had continuous TCD-based autoregulation monitoring during surgery.

RESULTS: Impaired autoregulation occurred in 32.4% (112/346) of patients. Preoperative TCD demonstrated moderate-severe large vessel stenosis in 67 (25.2%) of 266 patients with complete data. In adjusted analysis, female sex (odds ratio [OR], 0.46; 95% confidence interval [CI], 0.25–0.86; P = .014) and higher average temperature during CPB (OR, 1.23; 95% CI, 1.02–1.475; P = .029), but not moderate-severe large cerebral arterial stenosis (P = .406), were associated with impaired autoregulation during CPB. Of the 119 patients with available brain MRI data, 42 (35.3%) demonstrated WMHI. The presence of small vessel cerebral vascular disease was associated with impaired CBF autoregulation (OR, 3.25; 95% CI, 1.21–8.71; P = .019) after adjustment for age, history of peripheral vascular disease, preoperative hemoglobin level, and preoperative treatment with calcium channel blocking drugs.

CONCLUSIONS: These data confirm that impaired CBF autoregulation is prevalent during CPB predisposing affected patients to brain hypoperfusion or hyperperfusion with low or high blood pressure, respectively. Small vessel, but not large vessel, cerebral vascular disease, male sex, and higher average body temperature during CPB appear to be associated with impaired autoregulation.

KEY POINTS

• Question: Is cerebral small or large vessel vascular disease, a prevalent condition in elderly patients, associated with impaired cerebral blood flow autoregulation during cardiopulmonary bypass?
• Finding: We found stenosis of large cerebral arteries in 25% of patients, and brain magnetic resonance imaging detected white matter hyperintensities, an indicator of stenosis of small cerebral arterioles, in 35% of patients having brain magnetic resonance imaging. White matter hyperintensities, but not large cerebral arterial disease, were associated with impaired cerebral autoregulation.
• Meaning: Cerebral autoregulation monitoring may offer a potential biomarker of white matter hyperintensities in patients who may require careful perioperative blood pressure management and initiation of secondary stroke prevention strategies.