Continuous vs Bolus Neuromuscular Blockade Regimens in Moderate to Severe Hypoxemic Respiratory Failure and ARDS (COBRA)

The Effect of Continuous vs Bolus Neuromuscular Blockade Regimens for Patients With Moderate to Severe Hypoxemic Respiratory Failure and ARDS (COBRA): A Pilot Randomized Controlled Trial

Current clinical guidelines, such as those from the Surviving Sepsis Campaign and ARDSNet, recommend short-term NMBA use for patients with moderate to severe ARDS who exhibit persistent ventilator dyssynchrony or high plateau pressures despite deep sedation . However, they do not provide clear recommendations regarding the mode of administration. As a result, clinicians are left to extrapolate from limited or indirect evidence, which may lead to practice variation, uncertainty, and suboptimal care.

This pilot randomized controlled trial is designed to directly address this critical gap by comparing intermittent bolus administration versus continuous infusion of NMBAs in a pragmatic, real-world ICU setting. The study will assess feasibility metrics necessary to plan a definitive trial and generate preliminary clinical data on safety and effectiveness. By clarifying the comparative benefits and risks of each approach, the results may influence practice guidelines, reduce variation in care, and improve patient outcomes and reduce practice variation.patient outcomes, optimize resource use, and inform future guidelines on the management of moderate to severe ARDS.

Study Title: The Effect of Continuous vs Bolus Neuromuscular Blockade for Patients with Moderate to Severe HRF and ARDS: A Pilot Randomized Controlled Trial

Background:

Acute Respiratory Distress Syndrome (ARDS) affects ~10% of ICU patients and carries high morbidity and mortality. Neuromuscular blockade agents (NMBAs), especially cisatracurium, have historically been administered via continuous infusion to improve oxygenation and reduce ventilator-induced lung injury. However, recent evidence (e.g., ROSE trial) questions this approach, and emerging guidelines suggest intermittent bolus dosing may offer similar benefits with fewer adverse effects. There is a lack of direct comparative data, creating uncertainty in clinical practice.

Hypothesis & Objectives:

The study hypothesizes that a multicenter RCT comparing intermittent bolus vs continuous NMBA infusion in ARDS is feasible and that bolus dosing may show trends toward improved outcomes (e.g., ventilator-free days, fewer adverse events).

Primary objective: Assess feasibility of a definitive trial. Feasibility aims: 1. Recruitment rate (target ≥75%) 2. Protocol adherence (≥85%) 3. Data completeness (≥95%) 4. Safety monitoring of adverse events.

Secondary (exploratory) objectives: Compare 28-day ventilator-free days (VFDs), mortality, ICU/hospital length of stay, and ICU-acquired weakness.

Methods: This is a multicenter, prospective, pilot RCT in Alberta ICUs. 100 adult patients with moderate to severe ARDS will be randomized within 24 hours of diagnosis to either: 1. Intermittent bolus NMBA dosing OR 2. Continuous NMBA infusion (up to 48 hours). Both arms will receive lung-protective ventilation and guideline-based sedation.

Analysis: Feasibility outcomes will be described with 95% confidence intervals. Exploratory clinical outcomes will follow intention-to-treat principles using regression models. Results will inform design and sample size for a full-scale trial.

Risks & Mitigation: Risks such as protocol non-adherence, ICU-acquired weakness, and data loss will be managed via clinician education, adherence monitoring, and real-time data checks. Safety protocols, including allowance for rescue boluses and adherence to sedation best practices, will be enforced.

Team: Led by Drs. Parhar and Doig with a multidisciplinary team of critical care and clinical trial experts, the group has a strong track record in ICU research and implementation.

Significance & Knowledge Translation: This study addresses a critical evidence gap in ARDS care. Findings will inform future guidelines and practice by establishing whether bolus NMBA administration is a feasible, effective, and safer alternative to continuous infusion. Results will be disseminated through academic and clinical networks and will lay the groundwork for a large-scale, definitive RCT.

Inclusion Criteria:

Age ≥18 years

• Mechanically ventilated and on a controlled ventilation mode
• Diagnosis of moderate to severe ARDS (PaO₂/FiO₂ ≤150 mmHg on PEEP ≥5 cm H₂O)
• Bilateral pulmonary infiltrates consistent with ARDS
• Randomized within 24 hours of meeting ARDS criteria

Exclusion Criteria:

• Pregnancy
• Known allergy or contraindication to rocuronium
• Neuromuscular disorders (e.g., myasthenia gravis, Guillain-Barré syndrome)
• Brain death or decision for withdrawal of life-sustaining therapy
• Enrollment in a conflicting interventional trial