title: A randomized clinical trial comparing the effectiveness of ultrasound guidance versus nerve stimulation for lateral popliteal-sciatic nerve blocks in obese patients.
abstract: OBJECTIVE
  Ultrasound guidance may decrease the procedural time for many peripheral nerve blocks compared to nerve stimulation, but these studies have generally excluded obese patients. This single-blinded randomized clinical trial was designed to compare procedural times and related outcomes for ultrasound- versus nerve stimulation-guided lateral popliteal-sciatic nerve blockade specifically in obese patients.
  
  
  METHODS
  With Institutional Review Board approval and informed consent, patients with a body mass index greater than 30 kg/m(2) who were scheduled for foot/ankle surgery and desiring a peripheral nerve block were offered enrollment. Study patients were randomly assigned to receive a lateral popliteal-sciatic nerve block under either ultrasound or nerve stimulation guidance. The patient and assessor were blinded to group assignment. The primary outcome was procedural time in seconds. Secondary outcomes included number of needle redirections, procedure-related pain, patient satisfaction with the block, success rate, sensory and motor onset times, block duration, and complication rates.
  
  
  RESULTS
  Twenty-four patients were enrolled and completed the study. All patients had successful nerve blocks. The mean procedural times (SD) were 577 (57) seconds under nerve stimulation and 206 (40) seconds with ultrasound guidance (P< .001; 95% confidence interval for difference, 329-412 seconds). Patients in the ultrasound group had fewer needle redirections and less procedure-related pain, required less opioids, and were more satisfied with their block procedures. There were no statistically significant differences in other outcomes.
  
  
  CONCLUSIONS
  The results of this study show that, for obese patients undergoing lateral popliteal-sciatic nerve blocks, ultrasound guidance reduces the procedural time and procedure-related pain and increases patient satisfaction compared to nerve stimulation while providing similar block characteristics.
authors.affiliation: Departments of Anesthesiology and Critical Care Medicine (N.C.K.L., T.R.P., N.S.G., T.Y., B.S.) and Anthropology (T.R.P.), University of New Mexico, Albuquerque, New Mexico USA; Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, California USA (E.R.M.); and Anesthesiology and Perioperative Care Service, VA Palo Alto Health Care System, Palo Alto, California USA (E.R.M.).
authors.forename: Nicholas C K
authors.initials: NC
authors.lastname: Lam
authors.affiliation: Departments of Anesthesiology and Critical Care Medicine (N.C.K.L., T.R.P., N.S.G., T.Y., B.S.) and Anthropology (T.R.P.), University of New Mexico, Albuquerque, New Mexico USA; Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, California USA (E.R.M.); and Anesthesiology and Perioperative Care Service, VA Palo Alto Health Care System, Palo Alto, California USA (E.R.M.).
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Petersen
authors.affiliation: Departments of Anesthesiology and Critical Care Medicine (N.C.K.L., T.R.P., N.S.G., T.Y., B.S.) and Anthropology (T.R.P.), University of New Mexico, Albuquerque, New Mexico USA; Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, California USA (E.R.M.); and Anesthesiology and Perioperative Care Service, VA Palo Alto Health Care System, Palo Alto, California USA (E.R.M.).
authors.forename: Neal S
authors.initials: NS
authors.lastname: Gerstein
authors.affiliation: Departments of Anesthesiology and Critical Care Medicine (N.C.K.L., T.R.P., N.S.G., T.Y., B.S.) and Anthropology (T.R.P.), University of New Mexico, Albuquerque, New Mexico USA; Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, California USA (E.R.M.); and Anesthesiology and Perioperative Care Service, VA Palo Alto Health Care System, Palo Alto, California USA (E.R.M.).
authors.forename: Tony
authors.initials: T
authors.lastname: Yen
authors.affiliation: Departments of Anesthesiology and Critical Care Medicine (N.C.K.L., T.R.P., N.S.G., T.Y., B.S.) and Anthropology (T.R.P.), University of New Mexico, Albuquerque, New Mexico USA; Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, California USA (E.R.M.); and Anesthesiology and Perioperative Care Service, VA Palo Alto Health Care System, Palo Alto, California USA (E.R.M.).
authors.forename: Brian
authors.initials: B
authors.lastname: Starr
authors.affiliation: Departments of Anesthesiology and Critical Care Medicine (N.C.K.L., T.R.P., N.S.G., T.Y., B.S.) and Anthropology (T.R.P.), University of New Mexico, Albuquerque, New Mexico USA; Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University School of Medicine, Stanford, California USA (E.R.M.); and Anesthesiology and Perioperative Care Service, VA Palo Alto Health Care System, Palo Alto, California USA (E.R.M.). emariano@stanford.edu.
authors.forename: Edward R
authors.initials: ER
authors.lastname: Mariano
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D009765:Obesity / Q000150:complications* / Q000000981:diagnostic imaging; D010147:Pain Measurement; D010149:Postoperative Pain / Q000175:diagnosis / Q000209:etiology / Q000517:prevention & control*; D012584:Sciatic Nerve / Q000000981:diagnostic imaging*; D012585:Sciatica / Q000150:complications / Q000628:therapy*; D016037:Single-Blind Method; D004561:Transcutaneous Electric Nerve Stimulation / Q000379:methods*; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional / Q000379:methods
keywords: musculoskeletal ultrasound; nerve stimulation; obesity; outpatient surgery; regional anesthesia; sciatic nerve block; ultrasound