Peri-op Hypotension Associated With Post-op Delirium in Critically Ill

Author: Chase Doyle

Anesthesiology News

Perioperative hypotension may be associated with postoperative delirium in critical care patients, according to a new study, underscoring the risks of low blood pressure in the perioperative setting.

This retrospective analysis of more than 900 patients admitted directly to the surgical ICU from the OR showed that intraoperative hypotension was moderately associated with higher odds of postoperative delirium. A drop in arterial pressure in the postoperative period, however, was significantly associated with a higher hazard for delirium.

According to the researchers, given its association with postoperative adverse outcomes, hypotension should be avoided by clinicians in the perioperative period.

For this study, Dr. Maheshwari and his colleagues used a Cox proportional hazard survival model to assess the association between the amount of intraoperative hypotension—measured as the time-weighted average of mean arterial pressure (MAP) lower than 65 mm Hg—and delirium in 908 postoperative patients in the ICU, while also adjusting for potential confounding variables. A Cox model with the lowest MAP on each ICU day was used as a time-varying covariate to assess the association of hypotension during ICU stay with delirium.

The association with delirium was even stronger for postoperative hypotension. According to the data, a 10-mm Hg reduction in the lowest MAP on each day during the ICU stay was significantly associated with a higher hazard of delirium, with an adjusted hazard ratio of 1.16 (P<0.001).

A Widespread Occurrence

Postoperative delirium is a common problem in hospitals, with a reported incidence of up to 43%. Although postoperative patients admitted to critical care units have the highest rate of delirium, the differential effect of intraoperative and postoperative hypotension on this outcome remains poorly understood in this patient population.

As Dr. Maheshwari reported, two previous studies at the Cleveland Clinic have identified an association between low blood pressure and both myocardial and kidney injury. Recent changes in documentation at their institution have now made it possible to study the association with delirium in medical–surgical critically ill patients.

“In the past few years, it’s become standard in critical care units to assess patients for delirium at least twice per day with the Confusion Assessment Method for the ICU,” Dr. Maheshwari said.

The researchers acknowledged limitations to the study. “We are testing the hypothesis that low blood pressure is associated with delirium, but there are multiple other factors that affect the incidence of delirium, such as a patient’s sickness level and the administration of different medications,” Dr. Maheshwari said. “We did adjust for these known confounders in our analysis, but unknown confounders cannot be ruled out, and that’s one of the limitations of retrospective research. The goal is to find a signal so that you can carry out other future, prospective confirmatory studies.”