OBJECTIVES: Care of patients with acute respiratory distress syndrome (ARDS) is challenging and costly. Administering muscle relaxants may facilitate mechanical ventilation and improve oxygenation. After the relaxant is discontinued, some patients have delayed recovery of neuromuscular function, while other patients develop prolonged muscle weakness - acute quadriplegic myopathy syndrome (MYOPATHY). The objective of this study was to examine the incremental cost-effectiveness ratio (ICER) of cisatracurium versus using a traditional steroid based agent - vecuronium. METHODS: We designed a Markov ICER computer model. The base case involved a 55-year-old man admitted to the ICU for ARDS and then paralyzed for 3.5 days. Patients were modeled to be in one of the following health states: ICU-intubated, ICU-extubated, hospital ward, long-term care, home, or death. Patient progression was divided into 3.5 day cycles over six months. One trial found the average recovery after cisatracurium to be one hour versus 6 hours with vecuronium. Approximately 27% of ICU patients paralyzed for 3.5 days would be expected to develop MYOPATHY within 7 days. However, it is not evident that cisatracurium reduces this incidence. RESULTS: Our modeling predicted the total cost for an ARDS patient to be $58,629. At 6-months: mortality=43%, patients discharged home=32%, inhospital=8%, and long term care facility=17%. Using average wholesale prices, cisatracurium costs $599 for 3.5 days, versus $332 for vecuronium. The modeling suggests that cisatracurium is cost-effective (the ICER is < $35,000/QALY) if intubation time is reduced by 7%, or if ICU extubated time is reduced by 1.8%, or if the time the patient is in the ward is reduced by 2.3%. CONCLUSIONS: Incremental costs for cisatracurium are a very small portion of the total cost of care for ARDS patients. If cisatracurium use leads to very small reductions in ICU time, or ward length, it becomes a cost-effective intervention.