A simple mean arterial pressure alarm at 72 mmHg matched the Hypotension 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 the threshold for mean arterial pressure below 65 mmHg

Effect

3.75 vs 4.00 mmHg·min; log-scale mean difference 0.03 (95% CI -0.24 to 0.29); noninferiority margin -0.4

In this single-centre, blinded trial, 143 adults having moderate- or high-risk elective noncardiac surgery with continuous arterial pressure monitoring were assigned to a mean arterial pressure alarm below 72 mmHg or to a Hypotension Prediction Index alarm above 85. The primary outcome was the area under the threshold for a mean arterial pressure below 65 mmHg.

The median area was 3.75 mmHg·min (IQR 0.00 to 22.62) with the pressure alarm and 4.00 (0.00 to 19.00) with the index. After log transformation the mean difference was 0.03 (95% CI -0.24 to 0.29), with the lower bound above the noninferiority margin of -0.4. Secondary measures, including acute kidney and myocardial injury, 30-day mortality, length of stay and drug and fluid use, showed no differences.

The trial was single-centre and small, and not powered for patient outcomes. It supports a low-cost alert as a reasonable alternative where the proprietary index is unavailable, which suits many Indian operating theatres. It does not show the index is inferior or that either alarm improves outcomes.

• Consider setting the pressure alarm slightly above your treatment threshold, such as 72 mmHg for a 65 mmHg target, if no prediction index is available.
• Do not read this as proof that either approach improves kidney or cardiac outcomes.
• Tailor thresholds to the patient's baseline pressure and comorbidity.
• Audit time spent below 65 mmHg in your own cases.
• Check how your monitor allows an early-warning alarm to be configured.

Why it matters

It suggests much of the benefit of early warning may come from alerting sooner rather than from the proprietary algorithm.

Don't overread it

A single-centre trial of 143 patients with intermediate-risk surgery cannot show that either strategy lowers acute kidney injury or mortality.

The statistics, in plain English

A noninferiority trial asks whether the new option is not worse than the comparator by more than a set margin. Here the interval's lower limit (-0.24) stayed above the margin (-0.4), so the simple alarm was not meaningfully worse for time below 65 mmHg. Absence of difference in secondary outcomes with 143 patients is not evidence of equivalence for those outcomes.

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