Intervals for Oscillometric Arterial Pressure Monitoring during Noncardiac Surgery: The "2.5-Minute versus 5-Minute" Randomized Clinical Trial.

BACKGROUND

Guidelines recommend measuring arterial pressure at least every 5 min during surgery. However, it remains unknown whether shortening the measurement interval of intermittent oscillometric arterial pressure monitoring can help reduce intraoperative hypotension. This trial tested the primary hypothesis that oscillometric arterial pressure monitoring at 2.5-min versus 5-min intervals reduces intraoperative hypotension in noncardiac surgery patients with general anesthesia.

METHODS

In this single-center trial, 264 noncardiac surgery patients were randomized to oscillometric arterial pressure measurements with an upper-arm cuff at 2.5-min or 5-min intervals during surgery. The primary outcome was the amount of intraoperative hypotension quantified as the time-weighted average mean arterial pressure (MAP) less than 65 mmHg during surgery assessed using blinded continuous finger-cuff arterial pressure monitoring. Secondary outcomes included the administered time-weighted cumulative amount of norepinephrine indexed to body weight.

RESULTS

Of the 264 patients randomized (132 to each group), the primary outcome analysis included 132 patients in the 2.5-min group and 131 in the 5-min group. The median (IQR) time-weighted average MAP less than 65 mmHg was 0.00 (0.00, 0.04) mmHg in patients assigned to the 2.5-min group and 0.00 (0.00, 0.21) mmHg in patients assigned to the 5-min group (estimated location shift, -1.40 × 10 -5 mmHg; 95% CI, -6.64 × 10 -5 to 2.93 × 10 -6 mmHg; P = 0.27). Seven patients (5.3%) in the 2.5-min group had at least one 1-min episode of a MAP less than 50 mmHg versus 13 patients (9.9%) in the 5-min group ( P = 0.24). The median (IQR) time-weighted cumulative amount of norepinephrine indexed to body weight administered during surgery was 0.05 (0.03, 0.08) µg · kg -1 · min -1 in the 2.5-min group and 0.05 (0.02, 0.08) µg · kg -1 · min -1 in the 5-min group ( P = 0.40).

CONCLUSIONS

In this trial of patients having elective low- to moderate-risk noncardiac surgery with general anesthesia, arterial pressure was tightly controlled with norepinephrine, and the amount of intraoperative hypotension was low-irrespective of the randomized arterial pressure measurement interval. Although oscillometric arterial pressure monitoring at 2.5-min intervals-compared to 5-min intervals-did not reduce the time-weighted average MAP less than 65 mmHg, the authors cannot exclude that monitoring at 2.5-min intervals helps reduce profound hypotension.