title: Ultrasound-guided sciatic nerve block in overweight and obese patients: a randomized comparison of performance time between the infragluteal and subgluteal space techniques.
abstract: OBJECTIVE
  Despite ultrasound (US) guidance, sciatic nerve block (SNB) remains among the least performed peripheral blocks. By targeting the tissue plane between the gluteus maximus and quadratus femoris muscles, the US-guided subgluteal space technique may facilitate the performance of US-guided SNB. We aimed to evaluate whether the subgluteal space technique shortens SNB performance time in overweight and obese patients compared with the conventional infragluteal technique.
  
  
  METHODS
  Overweight and obese patients (body mass index, > 25 kg m ) undergoing US-guided SNB for knee arthroplasty received 30 mL admixture (1:2 lidocaine 2%; bupivacaine 0.5% with 1:200,000 epinephrine) in the tissue plane between the gluteus maximus and quadratus femoris (subgluteal space group) or around the sciatic nerve at the infragluteal level (infragluteal group). All patients received spinal anesthesia, continuous femoral nerve block, and postoperative multimodal analgesia. The primary outcome was SNB performance time defined as the time interval between placement of the US transducer on skin, and needle withdrawal after injection. Number of needle passes, procedural pain, SNB-related complications, SNB success, postoperative pain, and opioid consumption were also assessed.
  
  
  RESULTS
  Twenty-seven patients were assessed (subgluteal space, 14; infragluteal, 13). Mean SNB performance time was 4.4 minutes (95% confidence interval, 3.7-5.0) for the subgluteal space group and 9.0 minutes (95% confidence interval, 7.7-10.3) for the infragluteal group (P < 0.0001). Number of needle passes and procedural pain scores were lower in the subgluteal space group. There were no differences in SNB success or analgesic outcomes.
  
  
  CONCLUSIONS
  The subgluteal space technique may be performed 50% faster, with no detectable differences in block success and analgesic efficacy, compared with the infragluteal technique for US-guided SNB in overweight and obese patients receiving multimodal analgesia. Injection of local anesthetics along tissue planes may produce similar block characteristics to perineural injection for US-guided SNB.
authors.affiliation: From the * Department of Anesthesia, St Michael's Hospital; and † Department of Anesthesia, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Faraj W
authors.initials: FW
authors.lastname: Abdallah
authors.forename: Vincent W
authors.initials: VW
authors.lastname: Chan
authors.forename: Arkadiy
authors.initials: A
authors.lastname: Koshkin
authors.forename: Sherif
authors.initials: S
authors.lastname: Abbas
authors.forename: Richard
authors.initials: R
authors.lastname: Brull
mesh_terms: D000701:Analgesics, Opioid / Q000627:therapeutic use; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects; D015992:Body Mass Index; D006801:Humans; D009407:Nerve Block / Q000009:adverse effects / Q000379:methods*; D009765:Obesity / Q000150:complications* / Q000175:diagnosis; D009864:Ontario; D050177:Overweight / Q000150:complications* / Q000175:diagnosis; D010149:Postoperative Pain / Q000209:etiology / Q000517:prevention & control; D012584:Sciatic Nerve / Q000000981:diagnostic imaging* / Q000187:drug effects*; D013997:Time Factors; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional
chemical_list: D000701:Analgesics, Opioid