UC Irvine

Background

Vasopressors are a cornerstone for the management of vasodilatory hypotension. Vasopressor infusions are currently adjusted manually to achieve a predefined arterial pressure target. We have developed a closed-loop vasopressor (CLV) controller to help correct hypotension more efficiently during the perioperative period. We tested the hypothesis that patients managed using such a system postcardiac surgery would present less hypotension compared to patients receiving standard management.

Methods

A total of 40 patients admitted to the intensive care unit (ICU) after cardiac surgery were randomized into 2 groups for a 2-hour study period. In all patients, the objective was to maintain mean arterial pressure (MAP) between 65 and 75 mm Hg using norepinephrine. In the CLV group, the norepinephrine infusion was controlled via the CLV system; in the control group, it was adjusted manually by the ICU nurse. Fluid administration was standardized in both groups using an assisted fluid management system linked to an advanced hemodynamic monitoring system. The primary outcome was the percentage of time patients were hypotensive, defined as MAP <65 mm Hg, during the study period.

Results

Over the 2-hour study period, the percentage of time with hypotension was significantly lower in the CLV group than that in the control group (1.4% [0.9-2.3] vs 12.5% [9.9-24.3]; location difference, -9.8% [95% CI, -5.4 to -15.9]; P < .001). The percentage of time with MAP between 65 and 75 mm Hg was also greater in the CLV group (95% [89-96] vs 66% [59-77]; location difference, 27.6% [95% CI, 34.3-19.0]; P < .001). The percentage of time with an MAP >75 mm Hg (and norepinephrine still being infused) was also significantly lower in patients in the CLV group than that in the control group (3.2% [1.9-5.4] vs 20.6% [8.9-32.5]; location difference, -17% [95% CI, -10 to -24]; P < .001).The number of norepinephrine infusion rate modifications over the study period was greater in the CLV group than that in the control group (581 [548-597] vs 13 [11-14]; location difference, 568 [578-538]; P < .001). No adverse event occurred during the study period in both groups.

Conclusions

Closed-loop control of norepinephrine infusion significantly decreases postoperative hypotension compared to manual control in patients admitted to the ICU after cardiac surgery.