How often do symptoms persist after a nerve block used for shoulder surgery?

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The incidence, causes, and course of complications after interscalene brachial plexus block (ISB) were not well understood. Researchers prospectively monitored 521 patients for complications during the first 9 months after ISB.

This prospective study included 521 adults scheduled for elective shoulder surgery with ISB. The ISB procedure was standardized for all patients, and acute complications were recorded. Patients were observed daily for 10 days for paresthesias (tingling or other abnormal sensations), dysesthesias (unpleasant abnormal sensations), pain unrelated to surgery, and muscular weakness, then evaluated at 1, 3, 6, and 9 months after surgery. Persistent symptoms in these categories were investigated at 1 or 3 months using electroneuromyography. The final evaluation took place at 9 months.

A total of 520 patients completed the study; one was excluded after surgical damage to the axillary nerve. An interscalene catheter was used in 234 patients. Acute complications were one pneumothorax (0.2%) and one episode of central nervous system toxicity, involving incoherent speech (0.2%).

At 10 days, 74 patients (14%) had symptoms, and none had muscular weakness. At 1 month, 41 patients (7.9%) had symptoms, and none had muscular weakness. Thirty patients underwent electroneuromyography; diagnoses included sulcus ulnaris syndrome (n = 8), carpal tunnel syndrome (n = 2), and complex regional pain syndrome (n = 1).

At 3 months, 20 patients (3.9%) had symptoms, and none had muscular weakness. All underwent electroneuromyography; diagnoses included carpal tunnel syndrome (n = 2), complex regional pain syndrome (n = 4), plexus neuropathy (n = 1), and plexus damage (n = 1). At 6 months, 5 patients (0.9%) had symptoms. At 9 months, one patient (0.2%) had persistent dysesthesia.

The authors concluded that ISB performed with a standardized technical approach, material, and drugs was associated with a 0.4% incidence of short-term and severe long-term complications. They advised ruling out sulcus ulnaris syndrome, carpal tunnel syndrome, or complex regional pain syndrome when paresthesias, dysesthesias, or pain unrelated to surgery persist after ISB, because specific treatment may be required.