title: Lateralizing epidural catheter placement as evidenced by electrical stimulation.
abstract: BACKGROUND
  Epidural steroids are more effective if administered in the anterolateral epidural space. It follows that the ability to administer local anesthetics in the ipsilateral anterolateral epidural space should likewise improve their efficacy for postoperative epidural analgesia.
  
  
  OBJECTIVE
  We determined whether epidural catheters can be reliably placed in the ipsilateral anterolateral epidural space using the paramedian approach. Motor responses elicited by electrical stimulation were used to identify lateralization. We further assessed what angle of needle insertion resulted in successful catheter placement.
  
  
  METHODS
  Epidural anesthesia was performed in 68 patients undergoing total joint arthroplasty using the paramedian approach. FDA-approved electrical stimulating catheters were utilized, and the muscle response elicited was recorded with each centimeter of advancement of the catheter. Digital photographs were taken to determine the angle of needle entry.
  
  
  RESULTS
  Using the paramedian approach, an ipsilateral twitch was noted in 66 of the 68 patients (two had no response). With advancement of the catheter (2-5 cm), the twitch remained ipsilateral in 56 but disappeared in 12. The mean angle of the epidural needle was 40° to the midline. All patients had successful epidural anesthesia as evidenced by no response to surgical incision.
  
  
  CONCLUSIONS
  Epidural catheters can be reliably placed onto the side of surgery using the paramedian approach. This provides the opportunity to more selectively administer epidural local anesthetics.
  
  
  METHODS
  Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Anesthesiology, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA, sharrockn@hss.edu.
authors.forename: Nigel E
authors.initials: NE
authors.lastname: Sharrock
authors.forename: George
authors.initials: G
authors.lastname: Go
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015360:Analgesia, Epidural / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D000767:Anesthesia, Epidural / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects; D019643:Arthroplasty, Replacement; D002404:Catheterization / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D002408:Catheters, Indwelling; D004558:Electric Stimulation; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000294:innervation*; D009339:Needles; D017288:Pain Threshold; D010149:Postoperative Pain / Q000209:etiology / Q000517:prevention & control*; D011446:Prospective Studies; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000779:Anesthetics, Local