Intraoperative hypotension tied to increased postoperative delirium risk

A large retrospective study presented at the Anesthesiology 2021 annual meeting suggested that intraoperative hypotension may be tied to an increased risk of short-term postoperative delirium.

“In patients undergoing non-cardiac surgery, a mean arterial pressure (MAP) lower than 55 mm Hg was associated with a duration-dependent increase in the risk of postoperative delirium. The effect was magnified in patients who underwent surgery of long duration,” said the authors.

“Our research suggests rapidly addressing low blood pressure during surgery may prevent delirium and help with recovery,” noted senior author Professor Matthias Eikermann from the Montefiore Medical Center and Albert Einstein College of Medicine, New York, New York, US.

Participants in this multicentre study were 316,717 adults who underwent non-cardiac surgery under general anaesthesia at Beth Israel Deaconess Medical Center (BIDMC) or Massachusetts General Hospital, Boston, Massachusetts, US, between 2005 and 2017. Duration of intraoperative hypotension (reduction in MAP to <55 mg Hg) was categorized as no intraoperative hypotension, short (<15 minutes), and prolonged (≥15 minutes). Short and prolonged intraoperative hypotension were documented in 41.7 and 2.6 percent of participants, respectively. Patients with a history of delirium, dementia, or mild cognitive impairment were excluded.

Within 30 days post-surgery, 0.7 percent (n=2,183) of participants had a new diagnosis of delirium. [Anesthesiology 2021, abstract A1023]

Short duration of intraoperative hypotension was significantly associated with postoperative delirium (adjusted odds ratio [adjOR], 1.24, 95 percent confidence interval [CI], 1.13–1.35; p<0.001), with an even greater association noted with prolonged duration of intraoperative hypotension (adjOR, 1.58, 95 percent CI, 1.28–1.96; p<0.001).

A decrease in MAP by >30 percent from baseline did not affect the risk of postoperative delirium, be it hypotension of short duration (adjOR, 1.14, 95 percent CI, 0.92–1.41; p=0.224) or prolonged duration (adjOR, 1.20, 95 percent CI, 0.96–1.51; p=0.113).

Exploratory analysis showed that the effect of intraoperative hypotension on the risk of postoperative delirium was modified by duration of surgery, with a greater impact noted in patients whose surgeries were longer than 3 hours (adjOR, 1.40, 95 percent CI, 1.23–1.61) compared with ≤3 hours (adjOR, 1.17, 95 percent CI, 1.04–1.32; p_interaction=0.046). Conversely, age, history of arterial hypertension, obesity, and preoperative benzodiazepine use did not affect the association.

“Postoperative delirium is a major obstacle to a quick recovery from surgery, because patients are more dependent on others for activities of daily living and it can lead to an accelerated cognitive decline,” said Eikermann.

“Physician anaesthesiologists measure patients’ blood pressure at least every 3 minutes during surgery. The study shows they can help decrease the risk of postoperative delirium by immediately providing medication to increase blood pressure when it falls,” he noted.