Capnography as an aid in localizing the phrenic nerve in brachial plexus surgery. Technical note.

Hemant Bhagat,Anil Agarwal,Manish Sharma

doi:10.1186/1749-7221-3-14

Hemant Bhagat, Anil Agarwal + Show 1 more

Open Access

https://doi.org/10.1186/1749-7221-3-14

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Abstract

BackgroundTo determine whether monitoring end- tidal Carbon Dioxide (capnography) can be used to reliably identify the phrenic nerve during the supraclavicular exploration for brachial plexus injury.MethodsThree consecutive patients with traction pan-brachial plexus injuries scheduled for neurotization were evaluated under an anesthetic protocol to allow intraoperative electrophysiology. Muscle relaxants were avoided, anaesthesia was induced with propofol and fentanyl and the airway was secured with an appropriate sized laryngeal mask airway. Routine monitoring included heart rate, noninvasive blood pressure, pulse oximetry and time capnography. The phrenic nerve was identified after blind bipolar electrical stimulation using a handheld bipolar nerve stimulator set at 2–4 mA. The capnographic wave form was observed by the neuroanesthetist and simultaneous diaphragmatic contraction was assessed by the surgical assistant. Both observers were blinded as to when the bipolar stimulating electrode was actually in use.ResultsIn all patients, the capnographic wave form revealed a notch at a stimulating amplitude of about 2–4 mA. This became progressively jagged with increasing current till diaphragmatic contraction could be palpated by the blinded surgical assistant at about 6–7 mA.ConclusionCapnography is a sensitive intraoperative test for localizing the phrenic nerve during the supraclavicular approach to the brachial plexus.

Highlights

To determine whether monitoring end- tidal Carbon Dioxide can be used to reliably identify the phrenic nerve during the supraclavicular exploration for brachial plexus injury
Surgical intervention after brachial plexus injury is the best predictor of a favourable functional outcome after a trial of conservative management
Phrenic nerve identification is a key step during the supraclavicular approach for brachial plexus surgery

Summary

Introduction

To determine whether monitoring end- tidal Carbon Dioxide (capnography) can be used to reliably identify the phrenic nerve during the supraclavicular exploration for brachial plexus injury. Surgical intervention after brachial plexus injury is the best predictor of a favourable functional outcome after a trial of conservative management. Electrodiagnostic studies like sensory evoked potentials (SEP), electromyography (EMG) and nerve compound action potentials (NCAPs) are performed intraoperatively to aid in monitoring, guiding, identifying and localizing nerve function.[1] Though these diagnostic modalities have contributed immensely to the improved surgical outcomes following brachial plexus repair, their use may prove cumbersome and prone to errors of interpretation. Journal of Brachial Plexus and Peripheral Nerve Injury 2008, 3:14 http://www.jbppni.com/content/3/1/14 stimulation remains the gold standard to detect intact neuronal function. The authors describe the use of capnography as an aid in the intraoperative localization of the phrenic nerve

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