title: Electrical stimulation of the epidural space using a catheter with a removable stylet.
abstract: OBJECTIVE
  Electrical stimulation can be used to verify the location of epidural catheters. With the traditional technique, the latter must be primed with saline to allow for electrical conduction: any air lock will, thus, hinder the flow of current. Therefore, we set out to explore an alternative mode of stimulation by use of a catheter containing a removable stylet. This study examines the reliability of this new technique.
  
  
  METHODS
  In 71 patients undergoing surgery, a thoracic epidural catheter was inserted preoperatively. Loss of resistance was used to identify the epidural space. The TheraCath was introduced 5 cm into the space and connected to a neurostimulator via a 2-headed alligator clip. The intensity, pulse width, and level of myotomal contractions were recorded upon stimulation of the epidural space. A bolus of lidocaine was then injected and the patient assessed for sensory block to ice.
  
  
  RESULTS
  The failure rate in proper epidural catheter placement was 8.5%. Epidural stimulation yielded a mean threshold of 1.90 +/- 1.80 nanocoulombs. A total of 37 catheters produced a unilateral muscular response; however, block to ice was bilateral. When compared with the ice test, the sensitivity, specificity, positive predictive value, and negative predictive value of epidural stimulation with the TheraCath were 92%, 83%, 98%, and 50%, respectively.
  
  
  CONCLUSIONS
  We conclude that the TheraCath, because of the removable stylet, provides effective electrostimulation of the epidural space. Its use was simple and devoid of complications. Nonetheless, further studies are required before implementing its routine use in clinical settings.
authors.affiliation: Jewish General Hospital, Department of Anesthesia, Montreal, Quebec, Canada.
authors.forename: Roshanak
authors.initials: R
authors.lastname: Charghi
authors.forename: Sher Yi
authors.initials: SY
authors.lastname: Chan
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Kardash
authors.forename: Roderick J
authors.initials: RJ
authors.lastname: Finlayson
authors.forename: De Q H
authors.initials: DQ
authors.lastname: Tran
mesh_terms: D000328:Adult; D015360:Analgesia, Epidural / Q000295:instrumentation* / Q000379:methods; D002404:Catheterization; D004558:Electric Stimulation / Q000295:instrumentation* / Q000379:methods; D004824:Epidural Space; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D010149:Postoperative Pain / Q000628:therapy; D012680:Sensitivity and Specificity