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Electrical nerve stimulation using a stimulating catheter: what is the lower limit?
Merlin J Wehling1, Robert Koorn, Courtney Leddell
1Department of Anesthesiology, College of Nursing, University of Iowa, 200 Hawkins Drive, 6-JCP, Iowa City, IA 52242, USA.
Regional Anesthesia and Pain Medicine
|May 13, 2004
Summary
This case study shows a continuous cervical paravertebral catheter was successfully placed with a brisk motor response at 0.05 mA, demonstrating safety in nerve blocks. This technique minimizes intraneural injection risk.
Area of Science:
- Anesthesiology
- Regional Anesthesia
- Pain Management
Background:
- Nerve blocks are crucial for surgical anesthesia and analgesia.
- Minimizing intraneural injection risk is paramount during nerve block procedures.
- Current guidelines suggest caution with motor responses at low nerve stimulator outputs (≤0.3 mA).
Observation:
- A continuous cervical paravertebral catheter was placed in a patient undergoing rotator cuff repair.
- A brisk motor response was observed while stimulating the catheter at a very low output of 0.05 mA.
- Fluoroscopic imaging confirmed the catheter's relationship to the brachial plexus nerves (C5, C6).
Findings:
- The procedure resulted in no adverse sequelae, including neurological injury.
- The patient experienced excellent intraoperative and postoperative pain control without narcotics.
- Successful placement was achieved with a stimulating catheter at a low nerve stimulator output setting.
Implications:
- This case suggests that nerve blocks can be safely performed even with motor responses at very low nerve stimulator outputs.
- It challenges the conventional threshold of 0.3 mA for motor response during nerve block catheter placement.
- Further research may validate this approach for reducing intraneural injection risks in regional anesthesia.
