🧭 REBEL Rundown
📌 Key Points
- ⚖️Multicenter, noninferiority, randomized trial performed in France comparing management with noninvasive blood pressure (NIBP) monitoring versus invasive, arterial line catheter placement within 4 hours.
- 👥 Population of 1010 were randomized into the invasive arterial line group, and the noninvasive group, with a median age of 67, with primarily circulatory, septic shock.
- 🩸Notable side effects of arterial lines include hemorrhage and hematoma, while NIBP caused more significant pain complaints.
- 🟰 In ICU patients with circulatory shock, NIBP monitoring is noninferior to arterial line when comparing 28 day mortality rates.
- 🛟 The noninvasive strategy included an active rescue protocol
📝 Introduction
Previous research comparing outcomes between noninvasive blood pressure monitoring (NIBP) and invasive blood pressure monitoring (arterial line) has shown mixed results. A previously reviewed paper determined that arterial lines were not superior to NIBP (Haber et al., 2024). However, some perioperative literature (Wax et al., 2011) and ICU observational studies (e.g. Kaufmann et al., 2020; Alberta et al., 2025) suggest that NIBP may be inaccurate at extremes of blood pressure ranges, or in pediatric patients (Kaur et al., 2021).
The EVERDAC trial sought to determine if managing shock with noninvasive brachial cuff monitoring is noninferior to early (<4 hours) arterial catheter placement. While the study is set in the ICU, with the primary outcome being death at day 28, the 4 hour timeline could impact the management of hypotensive patients in the emergency department.
🧾 Paper
Muller G, 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. Nov 2025 PMID: 41159885
🔙Previously Covered On REBEL:
- Non-invasive Blood Pressure Monitoring in Critically Ill Adults?
- 2024 study performed by Haber, EN et. al, which asked the question whether NIBP was similar to arterial line monitoring in ICU patients, and found that the arterial line was not superior to NIBP.
- 2024 study performed by Haber, EN et. al, which asked the question whether NIBP was similar to arterial line monitoring in ICU patients, and found that the arterial line was not superior to NIBP.
- Size Matters: The Impact of Incorrect BP Cuff Size
- 2025 study performed by Ishigami J et al., on the effects of cuff size and accuracy, and found that the incorrectly-sized BP cuff can lead to inaccurate readings, suggesting potentially dangerous results.
- Non-invasive Blood Pressure Monitoring in Critically Ill Adults?
⚙️ What They Did
📈 Results:
💥 Critical Results
💪 Strengths
Study Design: This study was well-thought-out and well-executed, and used several facilities with standardized protocol. The randomization process and resulting comparison groups had similar patient characteristics demonstrating limited bias where a fully blinded study design was not possible.
Pragmatic approach: Study focus is on effectiveness in an actual applied, real-world setting.
Adherence to protocol: 12% in the non-invasive group had arterial lines placed prior to randomization. Of those, 6% had them removed within 24 hours, and 1 patient had it removed within 48 hours. Only 1 patient did not have the arterial line removed after randomization, showing an overall well-adherence to protocol.
Intention to Treat: The study additionally followed all patients to conclusion, whether they had to be excluded from the trial due to safety reasons or not, and included them in statistical analysis.
Appropriate population: These patients were critically ill, in circulatory shock and most patients (87% in NIBP, 90% in arterial line) required vasopressors. This substantiates claims made about NIBP, where prior research, as discussed above, used populations in the outpatient setting.
Well balanced groups: Measures of critical illness were comparable between the two groups, including vasopressor use and dose of vasopressors at time of randomization, SAPS II and SOFA scores, and various comorbidities e.g HTN, cirrhosis, cardiac insufficiency.
Advancement of the field: This study helps to fill a gap in the literature regarding noninferiority of NIBP following other trials, with the hopes to reduce invasive procedures in the critical, acute setting.
⚠️ Limitations
External Validity: A study that occurred in France is not necessarily generalizable to the rest of the world. Additionally, ICU patient management differs from the ED patient. Full demographic information was not included, such as ethnicity. Higher BMIs were excluded – which limits generalizability and may have played a role in reported success rates of arterial line placement. Also excluded were pediatric patients, where previous research has suggested a possible inferiority of NIBP to arterial lines. In addition, the authors do not include the number of patients requiring strict blood pressure monitoring like those with stroke or aortic dissection.Patients were admitted to the ICU from various locations, including directly from EMS, which may limit generalizability in regions with other protocols.
Study Population: The arterial line and NIBP group were similar in demographics that were presented. However there was a low number of dialysis patients who may be at higher risk of unreliable NIBP measurement collection. Additionally, the median age was 67 in both groups, but it is unclear how many patients were >75 years of age, which may be related to location, exclusion criteria, or palliation selection. The majority of the patients were medical patients, leading to a lack of data for trauma or surgical patients as well.
Confounding: The study selected all-cause mortality as the primary, critical outcome to demonstrate noninferiority. However, being “all-cause” at 28 days also allows for confounders, resulting in an inability to reliably estimate the effect of arterial line vs NIBP in the complicated, critical patient.
Blood Pressures not presented: While they included the standard guidelines for shock and vasopressor use, no data was included regarding the range of blood pressures acquired. Some previous research has suggested that NIBP is not a substitute for arterial lines–particularly at extremes–as the numbers acquired differ, which could impact generalizability. Although the outcomes were similar, it may have changed course of treatment depending on SBP/MAP goals.
Exclusion Criteria: Patients meeting “safety criteria”, on high dose vasopressors, or BMI>40 were excluded, which may limit generalizability.
Open-label style: Appropriate given the implementation of the study, but with the potential to introduce bias.
Not all protocols or suggestions made by the author followed. The NIBP group demonstrated slightly more arterial punctures (215 vs 180) despite the CVC recommendation.
Pain evaluation: While an important component regarding the full impact of invasive vs noninvasive interventions, the full pain scale was not elucidated, and not able to be collected from a typical intubated and sedated ICU patient, potentially leading to sedation being a confounder for lower pain scores. Pain scores were also not collected from venous punctures/interventions, potentially skewing results towards lower pain scores in patients without arterial or central lines. Combined this could have resulted in the presence of critical illness being a confounder in measurement of pain scores.
Practicality and Implementation: The authors did note that the burden on ICU patients was not addressed. It is possible that NIBP would be more labor-intensive for staff, or arterial lines more costly. As such, this may not be generalizable to the community setting.
Additionally, it was not clear where arterial lines were placed. A recent meta-analysis suggests that more centrally placed arterial lines give higher systolic and MAP readings than more peripheral lines (6), potentially introducing unknown confounders into the results. (Of note, many of the current blood pressure guidelines do not specify the location of blood pressure measurement when setting goal blood pressure parameters in critical illness.)
Furthermore, it is unclear the extent of the training of staff, or the utility of the plethysmography or other benefits of the arterial line that factored into bedside decision-making of the clinicians in the study. The study was not designed to assess how much arterial pressures, or benefits like a more exact cardiac output measurement or fluid responsiveness led to changes in patient care. Pressor requirements were used as a possible surrogate to the above.
Addressing Arrhythmias: Authors discussed implications of NIBP being able to detect accurate blood pressures even in the presence of arrhythmias, but only included data regarding atrial fibrillation. They did not address other tachy- or bradyarrhythmias, including atrial fibrillation with RVR or bradycardia, for example, and the study is lacking duration or incidence of these other arrhythmias which may impact BP readings depending on device.
🗣️ Discussion
- Generalizability: Both of the groups were of similar demographics from hospitals in France, although suffered from minor selection bias as discussed above, by primarily including medical, septic shock patients, with an average age of 67. It is possible that the open label design introduced bias such as treatment effect estimates and skewed reporting (e.g. pain scores in this case). Approximately a quarter of the patients were direct ICU admissions from an ambulance, in addition to the transfer patients, which adds a barrier to external generalizability to some emergency departments.
- Results: Significant critical results were comparable, including death in ICU, death at day 28, day 90, ICU length of stay, and RRT use at day 28.
- Limitation: selecting all-cause mortality at day 28 as a primary outcome. This allows for potential confounding in the critical, circulatory shock patient. They did address that potentially inaccurate readings could have led to increased vasopressor dosages, though this was not supported by the data.
- Patient Comfort vs. Procedure Risks: Arterial punctures occurred more frequently in the noninvasive group (742 vs 269 total attempts), as expected. More pain was reported in the noninvasive group, likely due to cuff inflation, but this data did not fully capture the pain of repeated sticks in intubated patients or the increased workload for the ICU staff as well as possible bias due to open label design, and potential confounding of pain scores by presence of critical illness. The invasive group had more arterial catheters placed as planned, but also had more CVCs placed, more blood cultures collected, more PRBCs administered, and significantly more hematomas (8.2% vs 1.0%).
- Infections: The magnitude of infections was small compared to the size of the group as a whole, but was statistically significant. The magnitude of complications may be expected to be larger in places where arterial line placement is not as common. The impact these infections made on the outcomes of the patients is unclear. It would be expected that those receiving more interventions would have more complications associated with said interventions, but this suggests the possibility that NIBP is not only noninferior, but potentially less harmful regarding procedural complications
- The Safety Backup Plan: It is critical to interpret “non-inferiority” in the context of the study’s active rescue protocol. This was not a passive “wait and see” approach; 14.7% of the noninvasive group eventually required an arterial line due to specific safety triggers like acidosis, failed puncture attempts, or unreliable cuff readings. Additionally, the exclusion of “high-dose” vasopressors used a large threshold: >2.5 μg/kg/min of norepinephrine equivalents. This is a wider range than the standard clinical definition of high dose (0.5 – 1.0 μg/kg/min), meaning the safety margin for NIBP demonstrated here is quite wide. The authors note that while arterial lines provide advanced data (e.g., stroke volume variation), they claim that these are seldom used in real-world practice. If clinicians treat numbers from an A-line the same as numbers from a cuff, the invasive risk yields no benefit. It is unclear how much this approach would translate to intensivists in various settings, and how much of an impact other benefits of arterial lines, like plethysmography, had on the care of the patients in the study.
- Overall: The study showed no difference in most patient-centered outcomes in ICU patients with circulatory shock between those monitored with NIBP vs arterial lines in a real-life scenario. It could offer some support for not urgently and immediately placing an arterial line in the emergency department, provided the patient does not meet the exclusion criteria (such as BMI > 40). However, there is no substantive data regarding impact on ICU efficiency, workload, cost, and patient quality of life. The study was performed in academic medical centers in France, thus it is unclear how this study’s findings would translate to other sites, particularly community ED’s in the US already facing operational pressures to defer procedures whether to Interventional Radiology or to the Intensivist. Further research is also needed to determine utility of arterial lines in patients with truly extreme vasopressor requirements, as well as the effect of arterial lines on bedside decision-making
📘 Author's Conclusion
“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.”
💬 Our Conclusion
Early NIBP monitoring showed non-inferior 28 day mortality compared to arterial line monitoring in patients with circulatory shock. NIBP is potentially associated with more patient discomfort; while arterial line placement with more procedural complications. More research is needed in other settings including trauma, and in broader patient populations including those with elevated BMI and ESRD. Based on this data, it seems reasonable to monitor blood pressure non-invasively in most critical patients with circulatory shock, particularly early in the resuscitation. However, clinician discretion should be used to weigh the benefits of arterial line placement, such as wave plethysmography, other resuscitation priorities for the patient, and operational priorities for the emergency department and ICU
🚨 Clinical Bottom Line
In non-obese patients (BMI <40) with shock, deferring arterial line placement in favor of reliable NIPB readings was non-inferior for mortality and reduced procedural complications. However, clinicians should consider rescue with an arterial line if cuff readings fail or vasopressor requirements exceed extreme limits (>2.5 μg/kg/min).
📚 References
- Alberta A, Haase D
Noninvasive BP Measurements, Regardless of Position, are not a Substitute for Intraarterial BP Monitoring in the Hemodynamically Unstable.
CHEST Journal. 2025
PMID 40348505 - Kaufmann T, Cox EGM, et al
Non-invasive oscillometric versus invasive arterial blood pressure measurements in critically ill patients: A post hoc analysis of a prospective observational study.
J Crit Care. 2020 Jun;57:118-123. Epub 2020 Feb 22.
PMID: 32109843 - Kaur J, Bhargava S, et al
Comparison of Noninvasive Oscillometric and Intra-Arterial Blood Pressure Measurements in Children Admitted to the Pediatric Intensive Care Unit.
J Pediatr Intensive Care. 2021 Nov 16;13(2):155-161.
PMID: 38919689 - Tran QK, Gelmann D, et al
Discrepancy Between Invasive and Noninvasive Blood Pressure Measurements in Patients with Sepsis by Vasopressor Status.
West J Emerg Med. 2022 May 5;23(3):358-367.
PMID: 35679499 - Wax DB, Lin HM, Leibowitz AB.
Invasive and concomitant noninvasive intraoperative blood pressure monitoring: observed differences in measurements and associated therapeutic interventions. Anesthesiology. 2011 Nov; 115(5): 973-8.
PMID: 21952254 - Hasegawa D, et al.
Comparison of Central and Peripheral Arterial Blood Pressure Gradients in Critically Ill Patients: A Systematic Review and Meta-Analysis. Crit Care Explor. May 2024
PMID: 38787296 - Haber, EN et al.
Accuracy of Noninvasive Blood Pressure Monitoring in Critically Ill Adults. J Intensive Care Med 2024.
PMID: 38215002
Post Peer Reviewed By: Mark Ramzy, DO (X/IG: @MRamzyDO), Marco Propersi, DO (X: @Marco_Propersi) and Anand Swaminathan, MD (X/IG: @EMSwami)
👤 Meet the Authors
Jessica Sieminski MD
Anatoliy Golster MD
Dorian Alexander, MD
🔎 Your Deep-Dive Starts Here
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