To the Editor:
We enjoyed reading Dr Guirguis's case report regarding a suspected iatrogenic phrenic nerve palsy following supraclavicular brachial plexus block (The Ochsner Journal, Volume 12, Number 2). The case accurately highlights a well-known risk of brachial plexus blockade and reinforces the need to consider excluding patients with poor pulmonary reserve. Traditional high-volume injections of local anesthetic (>30 mL) are reported to result in near-universal involvement of the phrenic nerve and subsequent paralysis of the ipsilateral hemidiaphragm.1 Direct needle visualization with ultrasound guidance allows for directed lower volume anesthetic injections that significantly reduce, but do not nullify, the risk of diaphragmatic paralysis.2 In our practice, we have found that ultrasonographic evaluation of the ipsilateral diaphragm with B-mode ultrasound after low-volume brachial plexus block is both rapid and easy to learn. By placing a low-frequency curvilinear transducer in the posterior axillary line, the clinician can rapidly evaluate the diaphragm for normal movement during the respiratory cycle.3 In patients who become acutely dyspneic, tachypnic, or hypoxic after brachial plexus block, the ultrasound of the ipsilateral diaphragm is a prudent evaluation that should occur in conjunction with other diagnostic and resuscitative measures.
REFERENCES
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