We report the case of a 68-yr-old obese male patient that was admitted in our university hospital for scheduled elective left carotid endarterectomy under regional anesthesia. Past medical history was significant, with controlled ischemic (four coronary artery bypass grafts at the age of 56 yr) and hypertensive cardiopathy and sleep apnea syndrome balanced with nocturnal ventilation support. Preoperative physical examination detected no abnormality. The patient received a deep cervical plexus block using a single-injection (15 ml 0.5% bupivacaine and 15 ml 2% lidocaine) nerve stimulator-assisted technique.1The patient developed respiratory distress associated with bilateral diaphragm paralysis symptoms 15 min after the block was placed. Facemask noninvasive titrated inspiratory pressure-support ventilation resulted in normal breathing pattern and oxygen parameters. After an uneventful surgical procedure the patient was transferred to the ward 2 h after postanesthesia care unit admission. Postoperative ambulatory arterial blood gas analysis and pulmonary functional tests were considered subnormal but phrenic conduction measurements confirmed severe right phrenic nerve conduction alteration.

In this report the patient experienced acute ventilatory failure probably attributable to bilateral diaphragm weakness. Epidural or subarachnoid injection might have promoted similar clinical features. However, the deep cervical plexus block we performed remained strictly ipsilateral to the puncture side. The block concerned left C2-C4 sensory dermatomes but preserved distal motor function of the arm. Then, we believe that the spread of deep cervical plexus block promoted a left phrenic block, resulting in ventilatory failure because of preexisting contralateral phrenic damage. Usually, extension of the block to the phrenic nerve is common during cervical blocks2but without significant clinical problems,3even in patients with preexisting lung disease.4In the present case, unrecognized coronary artery bypass graft-induced right phrenic nerve damage was revealed by the extension of left deep cervical plexus block.

Because up to 10% of cardiac surgery patients may suffer from postoperative electrophysiological abnormal phrenic nerve conduction,5we recommend anesthesiologists performing cervical blocks in postcardiac surgery patients remain vigilant attending the patient, with the capacity to supply ventilatory failure.

* University Hospital Henri Mondor, Creteil Cedex, France. gilles.dhonneur@jvr.ap-hop-paris.fr

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