UMEM Educational Pearls

Title: Meticulous MAP Monitoring or Disbelief in the Dogma -- Can we hold off on arterial lines in our ED patients with shock?

Keywords: Shock, procedures, arterial line, blood pressure, mean arterial pressure, MAP (PubMed Search)

Posted: 12/2/2025 by Kami Windsor, MD
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We have all been there – an ED patient with circulatory shock requiring vasoactive medications and, therefore, an arterial line for accurate and close monitoring of the MAP and appropriate titration of the infusions. But does it save lives?

The recently published NEJM article by Muller et al. takes a look at noninvasive BP monitoring (NIBP) by cuff versus early arterial catheterization in patients with hypotension and evidence of tissue hypoperfusion:

Open-label, pragmatic, parallel-group, noninferiority, multicenter RCT across 9 ICUs in France
Adult patients enrolled within 24h of ICU admission, randomized to NIBP (n=506) or arterial line placement within 4h of enrollment (n=504)
- 15% of NIBP group received art line during study period as deemed necessary by predefined safety criteria (unable to get NIBP or SpO2, for ex)
- 50% septic shock, >90% medical patients, 90% on pressors at randomization
Notable exclusions: BMI >40, high-dose vasopressors (total norepi tartrate* + epi infusion rate >2.5 mcg/kg/min)
Findings:
- No difference in primary outcome of 28-day mortality (34.3% NIBP vs. 36.9% art line)
- No difference in 90 day mortality, 28-day ventilator, vasopressor, or RRT-free days
- More arterial puncture attempts in the NIBP group (742 vs. 269 per 1000 ICU days)
- No increase in arterial line-associated infections or ischemia
- More (8 vs 1%) hematoma or hemorrhage at art line site in arterial line group
- More patients in NIBP group reported serious pain/discomfort related to device (13 vs 9%)

Bottom Line: This trial indicates that in appropriately-selected patients with shock, such as those not on high doses of vasopressors, with BMI < 40 and an ability to consistently obtain NIBP measurements, early arterial line placement in the ED for vasopressor titration is unlikely to improve outcomes. It is important to note other potential indications for arterial line placement (severe hypoxia, inability to obtain reliable SpO2 with need for ABG monitoring, cardiac arrest, pain related to NIBP cuff monitoring, intracranial hemorrhage, etcetera) may still make arterial line placement in the ED prudent and better for overall patient care.

*France refers to norepi by the tartrate formulation dose, US refers to the base norepi dose (ratio is 2:1 tartrate: base).

References

Muller G, Contou D, Ehrmann S, et al.; CRICS-TRIGGERSEP F-CRIN Network and the EVERDAC Trial Group. Deferring Arterial Catheterization in Critically Ill Patients with Shock. N Engl J Med. 2025;393(19):1875-1888. doi: 10.1056/NEJMoa2502136.