Development and evaluation of an automated phenylephrine delivery system by lower limit control for managing intraoperative hypotension

PURPOSE

In this study, we aimed to develop and evaluate an automated phenylephrine delivery system by lower limit control for the management of intraoperative hypotension, assessing its efficacy in maintaining adequate blood pressure levels.

METHODS

Twenty patients undergoing surgery with anticipated blood pressure fluctuations were enrolled in this study. Patients were randomly assigned to two groups. Noninvasive blood pressure (NIBP) was measured at 2.5-min intervals using an upper arm cuff. In the automated group, phenylephrine administration was governed by an automated system that delivered bolus doses and adjusted the continuous infusion rate when mean blood pressure (MBP) dropped below 65 mmHg. In the manual group, phenylephrine administration was initiated by the attending anesthesiologist under the same MBP threshold. Propofol, remifentanil, and rocuronium were administered via the automated delivery system for total intravenous anesthesia, to minimize hemodynamic variability between groups. The primary end point was the percentage of time during which MBP remained above 65 mmHg and systolic blood pressure below 140 mmHg, measured from the initiation to the cessation of intravenous anesthesia and assessed using a non-inferiority test.

RESULTS

The automated group adequately maintained blood pressure within the target range for 84.53% of the time, compared to 72.45% in the manual group, confirming statistical non-inferiority (p < 0.001).

CONCLUSION

This system effectively managed intraoperative hypotension using intermittent NIBP measurements, which are more feasible in clinical practice. Despite relying on less frequent and lower-resolution blood pressure data, it demonstrated efficacy comparable to anesthesiologist-led management, indicating its potential for broader clinical application.