title: Dosing of remifentanil to prevent movement during craniotomy in the absence of neuromuscular blockade.
abstract: BACKGROUND
  In neuroanesthesia practice, muscle relaxants may at times need to be avoided to facilitate intraoperative motor pathway monitoring. Our study's objective was to determine the optimal dose of remifentanil required to prevent movement after neurosurgical stimulation.
  
  
  METHODS
  After Institutional Review Board approval and written informed consent, 132 patients undergoing elective craniotomy randomly received one of 12 remifentanil dose regimens (0.10 to 0.21 microg/kg/min). Remifentanil was started before induction with propofol and succinylcholine. Anesthesia was maintained with isoflurane (0.6% end-tidal) in air/oxygen. During the study, movement was assessed on predetermined criteria by the anesthesiology, nursing, and neurosurgical teams. Heart rate and blood pressure were recorded every 5 minutes. We assessed the relationship between movement, hypotension, bradycardia, and dose using probit analysis and logistic regression.
  
  
  RESULTS
  Sixty-five percent of the patients moved in response to surgical stimuli [95% confidence interval (CI): 49%-79%] at a remifentanil infusion rate of 0.10 microg/kg/min, and movement decreased to 21% (95% CI: 11-35) at 0.21 microg/kg/min. The probability of movement was 50% at an infusion rate (95% CI) of 0.13 (0.10 to 0.15) microg/kg/min remifentanil and decreased to 25% at an infusion rate of 0.19 (0.17 to 0.29) microg/kg/min. The probability of hypotension and bradycardia was 50% at 0.13 (0.10 to 0.15) microg/kg/min and 0.17 (0.15 to 0.21) microg/kg/min, respectively.
  
  
  CONCLUSIONS
  Higher doses of remifentanil lessen the risk of movement in the absence of muscle relaxants with surgical stimulation for elective craniotomy. Hypotension and bradycardia were common at higher doses. Even at the maximum dose (0.21 mcg/kg/min) there was a 20% chance of movement. Adjunctive therapy is needed to ablate movement reliably, and to counteract the hypotensive effect of remifentanil. These findings may be helpful for clinicians administering remifentanil and isoflurane during procedures, where muscle relaxants may not be desirable.
authors.affiliation: Department of General Anesthesiology, Case Western Reserve University, Cleveland, OH, USA. maurtum@ccf.org
authors.forename: Marco A
authors.initials: MA
authors.lastname: Maurtua
authors.forename: Anupa
authors.initials: A
authors.lastname: Deogaonkar
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Bakri
authors.forename: Edward
authors.initials: E
authors.lastname: Mascha
authors.forename: Jie
authors.initials: J
authors.lastname: Na
authors.forename: Joseph
authors.initials: J
authors.lastname: Foss
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Sessler
authors.forename: Michelle
authors.initials: M
authors.lastname: Lotto
authors.forename: Zeyd
authors.initials: Z
authors.lastname: Ebrahim
authors.forename: Armin
authors.initials: A
authors.lastname: Schubert
mesh_terms: D000328:Adult; D000768:Anesthesia, General; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous / Q000008:administration & dosage* / Q000009:adverse effects; D001794:Blood Pressure / Q000187:drug effects; D001919:Bradycardia / Q000139:chemically induced / Q000453:epidemiology / Q000503:physiopathology; D001932:Brain Neoplasms / Q000601:surgery; D003399:Craniotomy / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007022:Hypotension / Q000139:chemically induced / Q000453:epidemiology / Q000503:physiopathology; D007431:Intraoperative Complications / Q000139:chemically induced / Q000453:epidemiology; D007432:Intraoperative Period; D007442:Intubation, Intratracheal; D007530:Isoflurane; D008297:Male; D008875:Middle Aged; D009068:Movement / Q000187:drug effects*; D019148:Neuromuscular Blockade; D019635:Neurosurgical Procedures; D010880:Piperidines / Q000008:administration & dosage* / Q000009:adverse effects; D011446:Prospective Studies; D000077208:Remifentanil
chemical_list: D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D010880:Piperidines; D007530:Isoflurane; D000077208:Remifentanil