title: No clinical or electrophysiologic evidence of nerve injury after intraneural injection during sciatic popliteal block.
abstract: BACKGROUND
  Intraneural injection during nerve-stimulator-guided sciatic block at the popliteal fossa may be a common occurrence. Although intraneural injections have not resulted in clinically detectable neurologic injury in small studies in human subjects, intraneural injections result in postinjection inflammation in animal models. This study used clinical, imaging, and electrophysiologic measures to evaluate the occurrence of any subclinical neurologic injury in patients with intraneural injection during sciatic popliteal block.
  
  
  METHODS
  Twenty patients undergoing popliteal block were enrolled; 17 patients completed the study protocol. After tibial nerve response was achieved by nerve stimulation (0.3-0.5 mA; 2 Hz; 0.1 ms), 20 ml mixture of mepivacaine (1.25%) and radiopaque contrast (2 ml) were injected. Location and spread of the injectant were assessed by ultrasound measurements of the sciatic nerve area before and after injection, and by computed tomography. In addition to clinical neurologic evaluations, serial electrophysiologic studies (nerve conduction and late response studies using predefined criteria) were performed at baseline and at 1 week and 3 weeks after the block for signs of subclinical neurologic dysfunction.
  
  
  RESULTS
  Sixteen injections (94%, 95% CI: 71-100%) met criteria for an intraneural injection. Postinjection nerve area on ultrasound increased by 45% (95% CI: 29-58%), P < 0.001. Computed tomography demonstrated fascicular separation in 70% (95% CI: 44-90%), air within the nerve in 29% (95% CI: 10-56%), contrast along bifurcations in 65% (95% CI: 38-86%), and concentric contrast layers in 100% (95% CI: 84-100%). Neither clinical nor electrophysiologic studies detected neurologic dysfunction indicating injury to the nerve.
  
  
  CONCLUSIONS
  Nerve-stimulator-guided sciatic block at the popliteal fossa often results in intraneural injection that may not lead to clinical or electrophysiologic nerve injury.
authors.affiliation: Department of Anesthesiology, Hospital Clinic, University of Barcelona, Barcelona, Spain. xsala@clinic.ub.es
authors.forename: Xavier
authors.initials: X
authors.lastname: Sala-Blanch
authors.forename: Ana M
authors.initials: AM
authors.lastname: López
authors.forename: Jaume
authors.initials: J
authors.lastname: Pomés
authors.forename: Josep
authors.initials: J
authors.lastname: Valls-Sole
authors.forename: Ana I
authors.initials: AI
authors.lastname: García
authors.forename: Admir
authors.initials: A
authors.lastname: Hadzic
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000842:Ankle / Q000601:surgery; D001182:Arthroscopy; D002908:Chronic Disease / Q000453:epidemiology; D004558:Electric Stimulation; D005260:Female; D005528:Foot / Q000601:surgery; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000009:adverse effects* / Q000379:methods*; D009422:Nervous System Diseases / Q000453:epidemiology*; D019637:Orthopedic Procedures; D010147:Pain Measurement; D011183:Postoperative Complications / Q000453:epidemiology*; D012584:Sciatic Nerve / Q000000981:diagnostic imaging; D013710:Tendons / Q000601:surgery; D017211:Treatment Failure; D016896:Treatment Outcome; D014463:Ultrasonography