In patients with shock, whether noninvasive blood-pressure monitoring is an effective alternative to the recommended use of an arterial catheter is uncertain.

In this multicenter, open-label, noninferiority trial, we randomly assigned patients who had shock and had been admitted to an intensive care unit within the past 24 hours to receive early insertion (<4 hours after randomization) of an arterial catheter (invasive strategy) or to be monitored with an automated brachial cuff (noninvasive strategy). Insertion of an arterial catheter was allowed later in patients assigned to the noninvasive-strategy group who met prespecified safety criteria. The primary outcome was death from any cause at day 28 (noninferiority margin, 5 percentage points). Adverse events of special interest related to the blood-pressure–monitoring device that was used were recorded, as was patient-reported pain or discomfort related to the ongoing presence of the device.

A total of 1010 patients underwent randomization; 504 patients assigned to the noninvasive-strategy group and 502 assigned to the invasive-strategy group were included in the analyses. A total of 74 patients (14.7%) in the noninvasive-strategy group and 493 (98.2%) in the invasive-strategy group underwent insertion of an arterial catheter. Death within 28 days occurred in 173 patients (34.3%) in the noninvasive-strategy group and 185 (36.9%) in the invasive-strategy group (adjusted risk difference, −3.2 percentage points; 95% confidence interval, −8.9 to 2.5; P=0.006 for noninferiority). Results of per-protocol analyses were similar in the two groups. A total of 66 patients (13.1%) in the noninvasive-strategy group and 45 (9.0%) in the invasive-strategy group had at least 1 day of pain or discomfort related to the ongoing presence of the blood-pressure–monitoring device. Hematoma or hemorrhage related to the arterial catheter occurred in 5 patients (1.0%) in the noninvasive-strategy group and 41 patients (8.2%) in the invasive-strategy group.

Among patients with shock, results for death from any cause at day 28 indicated that management without early arterial catheter insertion was noninferior to early catheter insertion. (Funded by the French Ministry of Health; ClinicalTrials.gov number, NCT03680963.)