Tracking hypotension and dynamic changes in arterial blood pressure with brachial cuff measurements

Arterial cannulation is strongly recommended during shock. Nevertheless, this procedure is associated with significant risks and may delay other emergent procedures. We assessed the discriminative power of brachial cuff oscillometric noninvasive blood pressure (NIBP) for identifying patients with an invasive mean arterial blood pressure (MAP) below 65 mm Hg or increasing their invasive MAP after cardiovascular interventions.

This prospective study, conducted in three intensive care units, included adults in circulatory failure who underwent 45 degrees passive leg raising, 300 mL fluid loading, and additional 200 mL fluid loading. The collected data were four invasive and noninvasive MAP measurements at each study phase.

Among 111 patients (50 septic, 15 cardiogenic, and 46 other source of shock), when averaging measurements of each study phase, NIBP measurements accurately predicted an invasive MAP lower than 65 mm Hg: area under the receiver operating characteristic curve 0.90 (95% CI: 0.71-1), positive and negative likelihood ratios 7.7 (95% CI: 5.4-11) and 0.31 (95% CI: 0.22-0.44) (cutoff 65 mm Hg). For identifying patients increasing their invasive MAP by more than 10%, the area under the receiver operating characteristic curve was 0.95 (95% CI: 0.92-0.96); positive and negative likelihood ratios (cutoff 10%) were 25.7 (95% CI: 10.8-61.4) and 0.26 (95% CI: 0.2-0.34).

NIBP measurements have a good discriminative power for identifying hypotensive patients and performed even better in tracking MAP changes, provided that one averages four NIBP measurements.