ABSTRACT
BACKGROUND: The duration of rocuronium in patients with BMI more than 30âkgâm is prolonged. Whether the reverse is true when BMI is less than 18.5âkgâm is unclear. OBJECTIVE: The objective of this study was to investigate whether a BMI less than 25âkgâm affects the duration of rocuronium in doses adjusted for actual body weight. DESIGN: A prospective, observational, single-centre study. SETTING: The operating room of a teaching hospital from 1 June 2008 to 30 June 2015. PATIENTS: Thirty patients with American Society of Anesthesiologists physical status I or II who were scheduled to undergo elective surgery (BMIâ<â25âkgâm, aged 23 to 74 years) maintained by 0.7 minimum alveolar concentration sevoflurane and remifentanil. MAIN OUTCOME MEASURES: Repetitive train-of-four stimulation was applied and contractions of the adductor pollicis muscle were recorded. Duration of the initial dose of rocuronium (D1) was defined as the time from injection of rocuronium 0.6âmgâkg to return of first twitch height to 25% of the control. Duration of additional doses (D2) was the time from a supplement of 0.15âmgâkg rocuronium to return of first twitch height to 25% of the control. The relationship between D1 or D2 and BMI was examined using linear regression analysis. RESULTS: Linear regression analysis revealed a significant correlation between duration of initial dose and BMI (Râ=â0.246; Pâ=â0.00531). A significant correlation between the duration of the additional dose and BMI was also found (Râ=â0.316; Pâ=â0.00122). CONCLUSION: The lower the BMI, the shorter the duration of rocuronium at initial and additional doses determined by the actual body weight in adult patients with a BMI less than 25âkgâm. TRIAL REGISTRATION: www.umin.ac.jp/ctr/index/htm with registry number UMIN 00009337 and UMIN 000015407.