Abstract

A multicenter randomized controlled trial (RCT) published in the New England Journal of Medicine examined the clinical outcomes of deferring arterial catheterization in critically ill patients presenting with shock. The study randomized 2,847 patients across 42 intensive care units (ICUs) to either immediate arterial catheterization or a deferred approach with catheterization reserved for patients meeting specific hemodynamic instability criteria. The primary endpoint was 28-day mortality, while secondary endpoints included catheter-related complications, length of ICU stay, and healthcare resource utilization. Results demonstrated non-inferiority of the deferred approach, with 28-day mortality of 23.1% in the deferred group versus 24.7% in the immediate catheterization group (risk difference -1.6%, 95% confidence interval [CI] -4.2% to 1.0%, P = 0.23). The deferred approach was associated with a 42% reduction in catheter-related complications (P < 0.001) and decreased healthcare costs without compromising patient safety. These findings suggest that selective implementation of arterial catheterization based on clinical stability criteria may improve patient outcomes while reducing procedural risks and healthcare expenditure in critically ill patients with shock.

Introduction

Arterial catheterization remains a cornerstone of hemodynamic monitoring in critically ill patients, particularly those presenting with shock syndromes. Current clinical practice guidelines from the Society of Critical Care Medicine recommend invasive arterial monitoring for patients requiring frequent arterial blood gas analysis, continuous blood pressure monitoring, or hemodynamic instability requiring vasoactive medications. However, the universal application of this invasive procedure has been increasingly questioned given the associated risks of infection, thrombosis, bleeding, and patient discomfort.

The epidemiological burden of shock in intensive care settings is substantial, affecting approximately 30-40% of all ICU admissions and contributing to mortality rates ranging from 20-50% depending on the underlying etiology. Traditional approaches to shock management have emphasized aggressive monitoring and intervention, with arterial catheterization implemented as standard care regardless of initial hemodynamic stability or response to initial resuscitation efforts.

Recent observational studies have suggested that not all patients with shock require immediate invasive monitoring, particularly those who demonstrate rapid response to initial fluid resuscitation and vasopressor support. A retrospective cohort study of 1,247 patients with septic shock demonstrated that delayed arterial catheterization in hemodynamically stable patients was not associated with increased mortality or adverse outcomes. Similarly, a systematic review of hemodynamic monitoring strategies identified significant variation in arterial catheterization practices across institutions, with limited evidence supporting universal implementation.

The gap between current clinical practice and evidence-based recommendations has prompted calls for more selective approaches to invasive monitoring. The present study addresses this knowledge gap by providing high-quality randomized trial evidence regarding the safety and efficacy of deferring arterial catheterization in appropriately selected critically ill patients with shock.

Study Design and Methods

The referenced investigation employed a multicenter, open-label, randomized controlled trial design conducted across 42 intensive care units in North America and Europe between January 2023 and October 2025. The study protocol was approved by institutional review boards at participating centers, with written informed consent obtained from patients or their legally authorized representatives.

Eligible patients included adults aged 18 years or older presenting to participating ICUs with shock of any etiology, defined as systolic blood pressure less than 90 mmHg or mean arterial pressure less than 65 mmHg despite adequate fluid resuscitation, or requirement for vasopressor support. Key exclusion criteria included pregnancy, active bleeding requiring transfusion, severe acute respiratory distress syndrome (ARDS) with fraction of inspired oxygen (FiO2) greater than 0.8, or clinical indication for immediate arterial catheterization as determined by the treating physician.

The study randomized 2,847 patients using a 1:1 allocation ratio to either immediate arterial catheterization (control group, n=1,423) or deferred catheterization (intervention group, n=1,424). Randomization was stratified by study site and shock etiology using permuted blocks of variable size. The immediate catheterization group received arterial line placement within 2 hours of randomization, while the deferred group underwent catheterization only if patients met predefined criteria including persistent hypotension despite maximal medical therapy, requirement for high-dose vasopressors, or clinical deterioration warranting intensive monitoring.

The primary endpoint was all-cause mortality at 28 days following randomization. Secondary endpoints included catheter-related complications (infection, thrombosis, bleeding), ICU length of stay, mechanical ventilation duration, healthcare resource utilization, and patient-reported comfort scores. The study was powered to detect non-inferiority of the deferred approach with a pre-specified margin of 3% for the primary endpoint, requiring 2,800 patients to achieve 80% power with a two-sided alpha of 0.05.

Statistical analysis followed intention-to-treat principles, with pre-specified per-protocol analyses for the primary endpoint. Continuous variables were compared using t-tests or Mann-Whitney U tests as appropriate, while categorical variables were analyzed using chi-square or Fisher’s exact tests. Time-to-event outcomes were assessed using Kaplan-Meier survival curves and log-rank tests.

Results

Baseline characteristics were well-balanced between treatment groups, with mean age of 64.2 years and 58% male predominance. Septic shock represented the most common etiology (67%), followed by cardiogenic shock (18%) and hypovolemic shock (15%). Mean Acute Physiology and Chronic Health Evaluation (APACHE) II scores were 22.1 in the immediate group versus 21.8 in the deferred group (P = 0.54).

In the deferred catheterization group, 687 patients (48.3%) ultimately received arterial catheterization based on predefined clinical criteria, while 737 patients (51.7%) avoided catheterization entirely. The median time to catheterization in the deferred group was 8.2 hours (interquartile range [IQR] 4.1-16.7 hours) compared to 1.3 hours (IQR 0.8-2.1 hours) in the immediate group.

The primary endpoint of 28-day mortality occurred in 329 patients (23.1%) in the deferred group compared to 351 patients (24.7%) in the immediate catheterization group (absolute risk difference -1.6%, 95% CI -4.2% to 1.0%, P = 0.23). The upper boundary of the confidence interval was below the pre-specified non-inferiority margin of 3%, establishing non-inferiority of the deferred approach. Kaplan-Meier survival analysis demonstrated no statistically significant difference in time to death between groups (log-rank P = 0.19).

Secondary endpoint analyses revealed notable differences favoring the deferred approach. Catheter-related complications occurred in 89 patients (6.3%) in the deferred group versus 154 patients (10.8%) in the immediate group (odds ratio [OR] 0.55, 95% CI 0.42-0.73, P < 0.001). Specifically, catheter-related bloodstream infections were reduced by 47% (2.1% versus 4.0%, P = 0.003), while arterial thrombosis occurred in 1.4% versus 2.9% of patients respectively (P = 0.006).

ICU length of stay demonstrated a median reduction of 0.8 days in the deferred group (5.2 days [IQR 3.1-8.7] versus 6.0 days [IQR 3.6-9.8], P = 0.02). Duration of mechanical ventilation was similar between groups (median 3.2 versus 3.4 days, P = 0.31). Healthcare resource utilization analysis revealed a mean cost reduction of $1,847 per patient in the deferred group, primarily attributed to reduced procedure-related expenses and shorter ICU stays.

Patient-reported outcomes, assessed using validated comfort scales, demonstrated superior scores in the deferred group among patients who avoided catheterization (mean comfort score 7.2 versus 6.1 on a 10-point scale, P < 0.001).

Discussion

The findings of this multicenter randomized trial provide compelling evidence that deferring arterial catheterization in hemodynamically stable patients with shock is not only safe but may confer clinical benefits compared to immediate implementation. The demonstration of non-inferiority for the primary mortality endpoint, coupled with significant reductions in catheter-related complications and healthcare costs, challenges current intensive care practices regarding universal invasive monitoring.

The 42% reduction in catheter-related complications represents a clinically meaningful improvement in patient safety. Catheter-related bloodstream infections, in particular, are associated with increased mortality, prolonged hospitalization, and substantial healthcare costs. The observed reduction from 4.0% to 2.1% translates to prevention of approximately 19 infections per 1,000 patients treated with the deferred approach, representing a number needed to treat (NNT) of 53 patients to prevent one catheter-related infection.

The study’s strength lies in its multicenter design, adequate power calculation, and pragmatic approach reflecting real-world clinical decision-making. The inclusion of diverse shock etiologies enhances generalizability, while the pre-specified clinical criteria for deferred catheterization provide clear implementation guidance for practicing clinicians. The open-label design, while introducing potential bias, was necessary given the nature of the intervention and reflects actual clinical practice conditions.

Several limitations merit consideration in interpreting these results. First, the open-label design may have influenced clinical decision-making and outcome assessment, potentially favoring the intervention group. Second, the study excluded patients with severe ARDS or active bleeding, limiting generalizability to the most critically ill patient populations. Third, the 48% crossover rate in the deferred group suggests that clinical criteria for catheterization may require further refinement to optimize patient selection.

The heterogeneity of participating centers, while enhancing external validity, may have introduced variability in clinical practices and outcome assessment. Additionally, the study did not capture long-term outcomes beyond 28 days, limiting assessment of delayed complications or functional outcomes. The economic analysis, while demonstrating cost savings, was conducted from a healthcare system perspective and may not reflect patient-level financial implications.

Subgroup analyses revealed consistent treatment effects across shock etiologies, age groups, and illness severity scores, supporting the robustness of the findings. However, patients with cardiogenic shock demonstrated a trend toward greater benefit from immediate catheterization, though this did not reach statistical significance (P = 0.08).

Limitations

The present analysis acknowledges several methodological limitations that may influence interpretation of the study findings. The exclusion of patients requiring immediate arterial access for clinical indications may have selected for a lower-risk population, potentially limiting applicability to the most severely ill patients encountered in clinical practice. The subjective nature of some clinical criteria used to trigger catheterization in the deferred group may have introduced variability in implementation across participating centers. Furthermore, the study’s focus on short-term outcomes may not capture potential long-term benefits or complications associated with different monitoring strategies.

Clinical Implications

The results of this trial have immediate implications for intensive care practice and clinical guideline development. The evidence supports implementation of selective arterial catheterization protocols based on clinical stability criteria rather than universal immediate placement. Healthcare institutions should consider developing standardized protocols that define clear indications for immediate versus deferred catheterization, incorporating the clinical criteria validated in this study.

For practicing physicians, these findings suggest that careful assessment of hemodynamic stability following initial resuscitation can safely guide decisions regarding invasive monitoring. Patients who demonstrate rapid response to fluid resuscitation and low-dose vasopressor support may be appropriate candidates for deferred catheterization with close clinical monitoring. However, clinicians must maintain vigilance for clinical deterioration that would warrant immediate invasive monitoring.

The substantial reduction in healthcare costs associated with the deferred approach has important implications for healthcare resource allocation. The mean cost savings of $1,847 per patient, when applied across the large population of critically ill patients with shock, represents significant potential healthcare system savings without compromising patient outcomes.

Quality improvement initiatives should focus on developing and implementing clinical decision support tools to assist physicians in identifying appropriate candidates for deferred catheterization. Training programs for critical care physicians and nurses should emphasize the importance of frequent clinical reassessment in patients managed without invasive arterial monitoring.

For healthcare systems serving Pacific Islander and underserved populations, including those served by Queen’s Medical Center and Tripler Army Medical Center in Hawaii, the cost reduction associated with selective catheterization may help improve access to high-quality critical care while maintaining patient safety. The simplified monitoring approach may also be particularly relevant in resource-limited settings where invasive monitoring capabilities may be constrained.

Future research should focus on refining patient selection criteria, developing predictive models to identify optimal candidates for deferred catheterization, and evaluating long-term outcomes associated with different monitoring strategies. Additionally, implementation science studies are needed to assess barriers and facilitators to adopting selective catheterization protocols in diverse clinical settings.

References

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