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A4028
October 27, 2015
9:45:00 AM - 11:15:00 AM
Room Upper 10
Observational Study on Variation in Neuromuscular Blockade Reversal
Timur Dubovoy, M.D., Michelle Housey, M.P.H., Scott Devine, Ph.D., Sachin Kheterpal, M.D.
University of Michigan Health System, Ann Arbor, Michigan, United States
Disclosures: T. Dubovoy: F. Funded Research; Self; Merck, Sharp, and Dohme, Inc. provided research funding for this project to the Dept. of Anesthesiology at the University of Michigan. There was no personal funding, or support for lectures/travel.. M. Housey: None. S. Devine: A. Salary; Self; Scott Devine is employed by Merck, Sharp, and Dohme, Inc. S. Kheterpal: F. Funded Research; Self; Merck, Sharp, and Dohme, Inc. provided research funding for this project to the Dept. of Anesthesiology at the University of Michigan. There was no personal funding, or support for lectures/travel..
Background

Although the need to balance risk of residual neuromuscular blockade (NMB) against side effects of neostigmine (NEO) is well described, variability exists between experts’ recommendations and current clinical practice of NMB monitoring and antagonism. We used electronic health record data to examine the relationship between subjective train-of-four (TOF) monitoring and administration of neostigmine. We hypothesized that larger reversal doses are used for patients with deeper levels of NMB, as evidenced by the last recorded TOF measurement. We also examined if dosing regimens reflect current guidelines of using ideal body weight (IBW) for NMB agents and total body weight (TBW) for NEO.

Methods

This is a retrospective observational study of adult, ASA 1-4 patients who underwent general anesthesia and received non-depolarizing NMB agents at the University of Michigan between 01/01/2004 and 12/31/2013. We excluded patients intubated prior to OR arrival, transported to ICU postoperatively, cardiac surgery, lung or liver transplantation, and cases where NEO was given to facilitate intraoperative neurologic monitoring. The primary outcome was defined as the ratio of mean total NEO dose in mg/kg to a standardized weight-based dose of 0.035 mg/kg as it relates to the last subjective TOF value prior to reversal. We would expect to see ratios of <1 for last TOF of 4/4, ratios close to 1 for TOF 2-3/4, and ratios >1 for TOF of 1/4. In addition, the mean total doses of NMB agents and NEO were compared across BMI categories. Statistical analysis included univariate comparisons and Kruskal-Wallis H test to determine statistically significant difference in distribution.

Results

Table 1 shows baseline patient and case characteristics for a total of 135,812 cases that met inclusion criteria. Although there was a statistically significant (p=0.000) decrease in NEO ratios with higher values of TOF (Table 2), all ratios were above 1 and did not reflect clinically significant change: 1.11±0.32 for TOF of 0/4 to 1.05±0.25 for TOF of 4/4 (38.9±11.2 vs 36.8±8.8 mcg/kg). Mean total doses of vecuronium and rocuronium indexed to IBW were 35% and 37% higher respectively for patients with BMI>40 vs normal weight, while the mean total dose of NEO indexed to TBW was 25% lower for BMI>40 vs normal weight (Figure 1).

Discussion

There was a weak correlation between TOF monitoring and dosing of NEO, refuting our hypothesis. Future prospective studies should evaluate appropriate doses of NEO for varying levels of NMB as demonstrated by TOF counts. Our data shows that patients with higher BMIs tend to receive relatively higher NMB doses per kg of IBW, while also receiving lower reversal doses per kg of TBW when compared to normal weight patients. This may put obese patients at an increased risk of residual NMB and warrants further investigation.
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