Capnography as an aid in localizing the phrenic nerve in brachial plexus surgery. Technical note^[*]

Abstract

Background 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.

Methods Three 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.

Results In 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.

Conclusion Capnography is a sensitive intraoperative test for localizing the phrenic nerve during the supraclavicular approach to the brachial plexus.

^*This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

• References

• 1 Slimp J. Intraoperative monitoring of nerve repairs. Hand Clin 2000; 16: 25-36 10696574
• 2 Moran SL, Steinmann SP, Shin AY. Adult brachial plexus injuries: mechanism, patterns of injury and physical diagnosis. Hand Clin 2005; 21: 13-24 10.1016/j.hcl.2004.09.004 15668062
• 3 Spinner RJ, Kline DG. Surgery for peripheral nerve and brachial plexus injuries or other nerve lesions. Muscle Nerve 2000; 23: 680-695 10.1002/(SICI)1097-4598(200005)23:5<680::AID-MUS4>3.0.CO;2-H 10797390
• 4 Al-Qattan MM. Identification of the phrenic nerve in surgical exploration of the brachial plexus in obstetrical palsy. J Hand Surg [Am] 2004; 29: 391-392 10.1016/j.jhsa.2003.12.018 15140478
• 5 Luo YM, Polkey MI, Lyall RA, Moxham J. Effect of brachial plexus co-activation on phrenic nerve conduction time. Thorax 1999; 54: 765-770 1745563 10456968
• 6 American Thoracic Society; European Respiratory Society. ATS/ERS statement on respiratory muscle testing. Am J Respir Crit Care Med 2002; 166: 528-547
• 7 Harper CM. Preoperative and intraoperative electrophysiologic assessment of brachial plexus injuries. Hand Clin 2005; 21: 39-46 10.1016/j.hcl.2004.09.003 15668064
• 8 Hemmerling TM, Schmidt J, Hanusa C, Wolf T, Jacobi KE. The lumbar paravertebral region provides a novel site to assess neuromuscular block at the diaphragm. Can J Anaesth 2001; 48: 356-360 11339777
• 9 Luedemann W, Hamm M, Blömer U, Samii M, Tatagiba M. Brachial plexus neurotization with donor phrenic nerves and its effect on pulmonary function. J Neurosurg 2002; 96: 523-526 11883837