Pharmacodynamics of cisatracurium in the intensive care unit: an observational study

BACKGROUND Data from previous studies indicate that optimal conditions for intubation are met 120 seconds after administration of 0.15 mg.kg-1 cisatracurium (ED95 × 3) following the induction of anesthesia. The aim of this study was to compare the doses required for complete paralysis after induction of anesthesia in ICU patients with the dose used in patients undergoing elective surgery. METHODS Seventeen ICU patients undergoing percutaneous tracheostomy and 17 patients undergoing an elective surgical procedure under muscle relaxation were included. In both groups, an initial intravenous bolus of cisatracurium besylate was given at a dose of 0.15 mg.kg-1 followed by repeated boluses of 0.03 mg.kg-1 every four minutes. The objective was to obtain no response to the train-of-four (TOF). The contractile response of the corrugator supercilii muscle was monitored every minute by observing the TOF in response to a peripheral nerve stimulator with a constant current set to 60 mA. RESULTS After the initial dose of cisatracurium, none of ICU patients (0/17) versus 15/17 of the elective surgery patients were completely paralyzed (P < 0.0001). There was a delay in the onset of neuromuscular blockade among the ICU patients. The cumulative doses of cisatracurium were significantly higher in the ICU group with 38 ± 14 mg (that is, 10 ± 4.7 ED95) versus 11 ± 2 mg (that is, 3 ± 0.3 ED95) in the elective surgery group (P < 0.0001). CONCLUSION The dosing of cisatracrurium for ICU patients, which is based on the dose recommended for elective anesthesia, is unsuitable because the onset is too slow. This phenomenon is probably caused by changes in the pharmacodynamics and pharmacokinetics. These data suggest that neuromuscular monitoring should be used in the ICU.