A MAP alarm at 72 mmHg prevented hypotension as well as the prediction index

Design

Single-centre blinded randomised noninferiority trial

Population

143 adults having moderate- or high-risk elective noncardiac surgery with arterial monitoring

Primary outcome

Area under MAP 65 mmHg threshold

Effect

Median 3.75 vs 4.00 mmHg·min; log mean difference 0.03 (95% CI −0.24 to 0.29)

The Hypotension Prediction Index is a proprietary algorithm designed to warn of hypotension minutes before it occurs, but it correlates closely with mean arterial pressure. A blinded single-centre randomised trial in Anesthesiology tested whether a simple MAP alarm set at 72 mmHg could do the same job as the index's default alarm (above 85).

In 143 adults having moderate- or high-risk elective noncardiac surgery with arterial lines, time-weighted hypotension below 65 mmHg was similar: median area under the threshold 3.75 mmHg·min with the MAP alarm against 4.00 with the index. The log-transformed mean difference was 0.03 (95% CI −0.24 to 0.29), within the noninferiority margin. Vasopressor and fluid use, alarm burden, kidney and myocardial injury, and length of stay did not differ.

The implication is that much of the index's benefit may come from prompting earlier action, which a raised MAP alarm can also do on any monitor at no cost. The trial was small and single-centre and was not powered for organ injury outcomes.

• Consider setting the intraoperative MAP alarm at 72 mmHg to prompt earlier treatment of falling pressure.
• A raised MAP alarm was noninferior to the Hypotension Prediction Index for limiting time below 65 mmHg.
• This approach needs no special monitor and works with any arterial line.
• Vasopressor and fluid use did not increase with the earlier alarm.
• The trial was not powered to show differences in kidney or myocardial injury.

Why it matters

Proactive blood pressure management may not need costly technology, just an earlier alarm.

Don't overread it

Noninferiority on hypotension time in 143 patients does not establish equivalent effects on organ injury.

The statistics, in plain English

Noninferiority means the MAP alarm was shown not to be meaningfully worse, because the confidence interval's lower bound (−0.24) stayed above the prespecified margin (−0.4). It does not mean it was better.

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