Common clinical thresholds of intraoperative hypotension and 30-day mortality following surgery: A retrospective cohort study

Abstract

Background: A wide range of thresholds define intraoperative hypotension and can be used to guide intraoperative blood pressure management. Many clinicians use the systolic blood pressure (SBP) <80 mmHg, the mean arterial pressure (MAP) <60 mmHg and the SBP percent drop from baseline (ΔSBP) >20% as alarming limits that should not be exceeded. Whether these common thresholds are valid limits that can inform clinicians on a possible increased risk of post-operative complications, particularly 30-day mortality, is currently unclear. Methods: We performed a retrospective registry-based cohort study between January 2015 and July 2016 using departmental hospital databases and the National Death Registry. Uni- and multivariate analyses were performed to assess the association between each of these three thresholds and 30-day post-operative mortality. Six specific markers of hypotension were used. Results: Of 11 304 patients, 86 (0.76%) died within 30 days following surgery. All intraoperative hypotension markers for SBP < 80 mmHg and MAP < 60 mmHg were significantly associated with 30-day mortality (P 20% were not significant. After adjustment for age, gender, American Society of Anesthesiologists (ASA) score, emergency status and risk related to the type of surgery, both SBP < 80 mmHg and MAP < 60 mmHg (the per cent area under the threshold marker) showed the strongest associations with 30-day mortality, with odds ratios (ORs) of 3.02 (95% confidence interval (CI) 1.81-5.07) and 3.77 (95% CI 2.25-6.31) respectively. Conclusions: Commonly accepted thresholds of intraoperative hypotension, such as an SBP of 80 mmHg and an MAP of 60 mmHg, are valid alarming limits that are significantly and independently associated with 30-day mortality.