Clinical evaluation of closed-loop control of blood pressure in seriously ill patients

To compare the effectiveness of a new method of closed-loop (automatic) control of BP with usual manual control.

Within-subject crossover trial.

General and open heart ICUs in a university teaching hospital.

Convenience sample of 74 seriously ill patients aged 17 to 88 yr. Twenty had hypertension: postoperative (n = 7), neurologic damage (n = 6), miscellaneous (n = 7), and were prescribed nitroprusside (n = 11) or nitroglycerin (n = 9). Fifty-four had hypotension: septic (n = 33), other (n = 21), and were prescribed norepinephrine (n = 30), dopamine (n = 11), epinephrine (n = 8), or dobutamine (n = 5). An additional 21 trials were omitted from analysis because of technical (n = 7), clinical (n = 1), or drug-related problems (n = 13).

Closed-loop and manual drug administrations 1-hr were studied during periods in each patient. The target and observed mean arterial pressure (MAP) and drug infusion rate were recorded electronically every 30 sec.

Time taken to achieve initial control (min); fidelity of control (the integral of size and duration of error from target MAP +/- 10% in mm Hg.hr/hr); and average drug dose administered (microgram/min as % maximum possible per drug).

Compared with manual control, closed-loop achieved faster initial control (log-rank chi 1 = 5.04, p less than .05) and greater fidelity (mean 1.37 vs. 2.36; F = 7.15, p less than .01). There was no difference in average drug dose administered. There was uniformity in the efficacy advantage of closed-loop drug administration across drugs and patient classifications.

The new closed-loop system is more effective than the usual manual control in managing acute BP disturbances in the seriously ill patient.