Association between preoperative blood pressure and outcomes in cardiac surgery: results of a prospectively planned cohort study.

Background: It is unknown whether unwitnessed BP (UBP) measurement or ambulatory BP (ABP) monitoring improves the prediction of adverse events estimated by risk scores. We intended to study associations between preoperative BP measured through these two methods and the incidence of adverse outcomes in patients undergoing cardiac surgery.

Methods: We included a cohort of 167 patients undergoing elective or urgent cardiac surgeries. Preoperative BP was measured by UBP and 24-hour ABP. Primary outcome was the combination of mortality from any cause, nonfatal myocardial infarction, nonfatal stroke, new hospital admission, and dialysis occurring within 30 days after surgery. The associations between preoperative BP and surgical outcomes were tested using the Chi-square test and Analysis of Variance. A generalized linear model with a logistic link function and a robust estimator was used to adjust for the EuroScore-II risk estimation.

Results: The incidence of the primary outcome increased in parallel with the quartiles of the 24-hour ABP in participants submitted to CABG: 10% in the first quartile, 13% in the second, 37% in the third, and 53% in the fourth quartile (P for trend<0.01). Quartiles of overnight ABP were also significantly associated with postoperative complications in patients undergoing CABG (P=0.04). The risks in CABG patients were independent of the EuroScore-II. There was no association between BP and outcomes in patients submitted to other surgeries.

Conclusions: High preoperative BP measured by ABP monitoring is a risk factor for postoperative complications in patients submitted to CABG.