Timing, Threshold, and Duration of Intraoperative Hypotension in Cardiac Surgery: Their Associations With Postoperative Delirium

Abstract

Objectives: To study the timing, threshold, and duration of intraoperative hypotension (IOH) associated with the risk of postoperative delirium (POD).

Design: A single-center retrospective observational study.

Setting: University teaching hospital.

Participants: A total of 503 adult patients who underwent cardiac valvular surgery that required cardiopulmonary bypass (CPB).

Measurements and main results: The authors predefined the following 4 periods: (1) during surgery, (2) pre-CPB, (3) during CPB, and (4) post-CPB, and 8 thresholds of mean arterial pressure for IOH according to every 5 mmHg between 50 mmHg and 85 mmHg. The authors calculated the cumulative duration below the 8 thresholds in each period. The primary outcome was delirium defined as a score of ≥4 for at least one Intensive Care Delirium Screening Checklist assessment during 48 h after the surgery. Among 503 patients, POD occurred in 95 patients (18.9%). There was no significant association of POD with all of the thresholds of IOH in the periods of pre-CPB, during CPB, and during surgery. However, in the post-CPB period, the patients with POD had a significantly longer cumulative duration of IOH according to all of the thresholds of mean arterial pressure. In multivariate analyses, 4 IOH thresholds in the post-CPB period were associated independently with POD: <60 mmHg (odds ratio [OR] =1.84 [95% CI 1.10-3.10]), <65 mmHg (OR = 1.72 [1.01-2.92]), <70 mmHg (OR = 1.83 [1.03-3.26]), and <75 mmHg (OR = 1.94 [1.02-3.69]).

Conclusions: A longer cumulative duration of IOH with the threshold between <60 and <75 mmHg that occurred after CPB was independently associated with the risk of POD.

Keywords: Cardiac valvular surgery; Intraoperative hypotension; Post cardiopulmonary bypass; Postoperative delirium; Threshold of mean arterial pressure.