Effect of Targeting Mean Arterial Pressure During Cardiopulmonary Bypass by Monitoring Cerebral Autoregulation on Postsurgical Delirium Among Older Patients

Abstract

; and the Cerebral Autoregulation Study Group IMPORTANCE Delirium occurs in up to 52% of patients after cardiac surgery and may result from changes in cerebral perfusion. Using intraoperative cerebral autoregulation monitoring to individualize and optimize cerebral perfusion may be a useful strategy to reduce the incidence of delirium after cardiac surgery. OBJECTIVE To determine whether targeting mean arterial pressure during cardiopulmonary bypass (CPB) using cerebral autoregulation monitoring reduces the incidence of delirium compared with usual care. DESIGN, SETTING, AND PARTICIPANTS This randomized clinical trial nested within a larger trial enrolled patients older than 55 years who underwent nonemergency cardiac surgery at a single US academic medical center between October 11, 2012, and May 10, 2016, and had a high risk for neurologic complications. Patients, physicians, and outcome assessors were masked to the assigned intervention. A total of 2764 patients were screened, and 199 were eligible for analysis in this study. INTERVENTION In the intervention group, the patient's lower limit of cerebral autoregulation was identified during surgery before CPB. On CPB, the patient's mean arterial pressure was targeted to be greater than that patient's lower limit of autoregulation. In the control group, mean arterial pressure targets were determined according to institutional practice. MAIN OUTCOMES AND MEASURES The main outcome was any incidence of delirium on postoperative days 1 through 4, as adjudicated by a consensus expert panel. RESULTS Among the 199 participants in this study, mean (SD) age was 70.3 (7.5) years and 150 (75.4%) were male. One hundred sixty-two (81.4%) were white, 26 (13.1%) were black, and 11 (5.5%) were of other race. Of 103 patients randomized to usual care, 94 were analyzed, and of 102 patients randomized to the intervention 105 were analyzed. Excluding 5 patients with coma, delirium occurred in 48 of the 91 patients (53%) in the usual care group compared with 39 of the 103 patients (38%) in the intervention group (P = .04). The odds of delirium were reduced by 45% in patients randomized to the autoregulation group (odds ratio, 0.55; 95% CI, 0.31-0.97; P = .04). CONCLUSIONS AND RELEVANCE The results of this study suggest that optimizing mean arterial pressure to be greater than the individual patient's lower limit of cerebral autoregulation during CPB may reduce the incidence of delirium after cardiac surgery, but further study is needed. TRIAL REGISTRATION ClinicalTrials.gov identifier: NCT00981474

The Impact of Preoperative Risk on the Association between Hypotension and Mortality after Cardiac Surgery: An Observational Study

“…This same group of authors also reported in a substudy of a RCT (N = 36), that sublingual microcirculatory flow was no different in patients whose MAP was maintained in the 70–80 mmHg vs. 40–50 mmHg range during CPB [ 19 ]. In addition, a recent RCT (N = 199) reported that maintenance of MAP during CPB at the lower limit of the individual’s cerebral autoregulation reduced the incidence of delirium after cardiac surgery [ 20 ].…”

Personalizing the Definition of Hypotension to Protect the Brain

“…A subset of 199 patients enrolled in that trial underwent detailed assessments for postoperative delirium. 44 We found that the odds of delirium was reduced by 45% in the group whose MAP target were determined by autoregulation monitoring compared with the usual care (odds ratio, 0.55; 95% CI, 0.31 to 0.97; P = 0.04). Although preliminary, these data suggest that optimizing MAP to be higher than an individual's lower limit of autoregulation, but lower than the upper limit, during CPB may be a strategy to reduce the frequency of postoperative delirium.…”

“…52 Thus far, our group has (1) validated clinically feasible methods of cerebral blood flow autoregulation in laboratory animals and humans; (2) demonstrated a relationship between a MAP outside the autoregulation boundaries and brain dysfunction and other organ injury; and (3) shown that acting on MAP that is lower than the lower limit of autoregulation during cardiac surgery reduces the frequency of delirium after surgery. 17,29,37,40,[42][43][44] We acknowledge that the majority of our clinical findings linking MAP outside the limits of autoregulation and adverse patient outcomes have been in the setting of cardiac surgery, and these results may not necessarily be easily extrapolated to other noncardiac surgery settings. Certainly, more research is necessary to confirm and extend our results.…”

Real-Time Intraoperative Determination and Reporting of Cerebral Autoregulation State Using Near-Infrared Spectroscopy

“…In a recent nested analysis of a prospectively randomized clinical trial, basing patient MAP targets on LLA information was shown to reduce the frequency of carefully assessed postoperative delirium compared with usual care. 30 Thus, a monitoring technology based on the proposed rS o 2 method would enable the clinician to rapidly respond intraoperatively to MAP below the LLA, possibly reducing adverse outcomes.…”