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Ultrasound-guided Sciatic Nerve Block in Overweight and Obese Patients: A Randomized Comparison of Performance Time Between the Infragluteal and Subgluteal Space Techniques
  1. Faraj W. Abdallah, MD*,,
  2. Vincent W. Chan, MD, FRCPC,
  3. Arkadiy Koshkin, MD,
  4. Sherif Abbas, MD and
  5. Richard Brull, MD, FRCPC
  1. * Department of Anesthesia, St Michael’s Hospital; and Department of Anesthesia, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada.
  1. Address correspondence to: Richard Brull, MD, FRCPC, Department of Anesthesia, Toronto Western Hospital, 399 Bathurst St, Toronto, Ontario, Canada M5T 2S8 (e-mail: richard.brull{at}


Background and Objectives 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 − 2) 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.

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  • Dr Vincent W. Chan received equipment support from BK Medical, Philips Medical Systems, SonoSite, and Ultrasonix. The other authors declare no conflict of interest.

    Dr Richard Brull is supported by the Merit Award Program, Department of Anesthesia, University of Toronto.

    This work was presented in part at the 38th Annual Spring Meeting and Workshops of the American Society of Regional Anesthesia and Pain Medicine (ASRA), Boston, MA, May 2–5, 2013.

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