Anesth Analg 2006;102:1586
© 2006 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000215191.08824.D2
LETTER TO THE EDITOR
Is It Time to Perform All Thoracic Epidural Placements Under Fluoroscopy?
Ban C. H. Tsui, MD, MSc, FRCP
University of Alberta Hospital, Edmonton, Alberta, Canada, btsui{at}ualberta.ca
In Response:
Although I agree with Dr. Narouze's opinion (1) that real-time fluoroscopy can be a useful tool for thoracic epidural catheter placement, I doubt it would it be safer to inject contrast material instead of local anesthetic. The injection of any agent has the potential to injure the spinal cord. Damage may occur as a result of the pressure generated by the injection itself or as a result of toxic effects of the chemical injected. Because direct needle trauma to the spinal cord occurring during epidural insertion is a rare occurrence resulting in devastating complications (2), there is clearly a need to implement additional measures to ensure needle placement before the injection of any fluid.
Electrophysiological monitoring has become common practice in spinal surgery (3), and using electrical stimulation during epidural needle advancement has been recently introduced (4–10). Correct placement of the epidural catheter tip (1–2 cm from the nerve roots) is indicated by a motor response elicited with a current between 1–10 mA (4,11). Any motor response observed with a significantly lower threshold current (<1 mA) suggests that the catheter is in the subarachnoid or subdural space or is in proximity to a nerve root (12,13). In a recent study, we demonstrated that monitoring an insulated needle with continuous electrical stimulation at 6 mA may prevent unintentional placement of insulated needles into the intrathecal space (14). Electrical stimulation relies on the physiological responses of the nerve root to electrical current to locate the epidural space, whereas the conventional loss-of-resistance technique relies on the anatomical characteristics of the epidural space. Individually, electrical stimulation and loss-of-resistance have their limitations. Used together, both techniques may compensate for each other's weaknesses to assist with optimal needle placement. As it does not seem that the electrical stimulation technique results in any complication or patient discomfort (2–8), the potential benefit of epidural stimulation testing should not be overlooked.
References
- Narouze SN. Is it time to perform all thoracic epidural placements under fluoroscopy? Anesth Analg 2006;102:1585.[Free Full Text]
- Tsui BCH, Armstrong K. Can direct spinal cord injury occur without paresthesia? A report of delayed spinal cord injury after epidural placement in an awake patient. Anesth Analg 2005;101:1212–4.[Abstract/Free Full Text]
- Raynor BL, Lenke LG, Kim Y, et al. Can triggered electromyograph thresholds predict safe thoracic pedicle screw placement? Spine 2002;27:2030–5.[Web of Science][Medline]
- Tsui BC, Gupta S, Finucane B. Confirmation of epidural catheter placement using nerve stimulation. Can J Anaesth 1998;45:640–4.[Web of Science][Medline]
- Tsui BC, Wagner A, Cave D, Kearney R. Thoracic and lumbar epidural analgesia via the caudal approach using electrical stimulation guidance in pediatric patients: a review of 289 patients. Anesthesiology 2004;100:683–9.[Web of Science][Medline]
- Tsui BC, Wagner A, Cave D, Seal R. Threshold current for an insulated epidural needle in pediatric patients. Anesth Analg 2004;99:694–6.[Abstract/Free Full Text]
- Tsui BC, Wagner A, Finucane B. The threshold current in the intrathecal space to elicit motor response is lower and does not overlap that in the epidural space: a porcine model. Can J Anaesth 2004;51:690–5.[Web of Science][Medline]
- Tsui BC, Gupta S, Finucane B. Determination of epidural catheter placement using nerve stimulation in obstetric patients. Reg Anesth Pain Med 1999;24:17–23.[Web of Science][Medline]
- Tsui BC, Emery D, Uwiera RR, Finucane B. The use of electrical stimulation to monitor epidural needle advancement in a porcine model. Anesth Analg 2005;100:1611–3.[Abstract/Free Full Text]
- Tsui BC, Wagner AM, Cunningham K, et al. Threshold current of an insulated needle in the intrathecal space in pediatric patients. Anesth Analg 2005;100:662–5.[Abstract/Free Full Text]
- Tsui BC, Guenther C, Emery D, Finucane B. Determining epidural catheter location using nerve stimulation with radiological confirmation. Reg Anesth Pain Med 2000;25:306–9.[Web of Science][Medline]
- Tsui BC, Gupta S, Finucane B. Detection of subarachnoid and intravascular epidural catheter placement. Can J Anaesth 1999;46:675–8.[Web of Science][Medline]
- Tsui BC, Gupta S, Emery D, Finucane B. Detection of subdural placement of epidural catheter using nerve stimulation. Can J Anaesth 2000;47:471–3.[Web of Science][Medline]
- Tsui BC, Wagner AM, Cunningham K, et al. Can continuous low current electrical stimulation distinguish insulated needle position in the epidural and intrathecal spaces in pediatric patients? Paediatr Anaesth 2005;15:959–63.[Medline]
