Ipsilateral shoulder pain after thoracotomy with epidural analgesia: The influence of phrenic nerve infiltration with lidocaine

Patients receiving effective thoracic epidural analgesia for postthoracotom y pain may still complain of severe ipsilateral shoulder pain. The etiology of this pain is unclear. In this randomized, double-blinded, placebo-contr olled study, we investigated the effect of phrenic nerve infiltration with lidocaine or saline on postoperative shoulder pain in 48 patients. After co mpletion of a lung resection, patients received either 10 mL of 1% lidocain e or 10 mL of 0.9% saline infiltrated into the periphrenic fat pad at the l evel of the diaphragm. Shoulder pain was experienced by 33% of patients rec eiving lidocaine, compared with 85% of patients receiving saline (P < 0.008 ). Overall pain scores were lower with lidocaine (P < 0.05). Paco(2) values were not significantly higher with lidocaine in the first 2 h. We conclude that pain transmitted via the phrenic nerve and referred to the shoulder i s the most likely explanation for the ipsilateral shoulder pain experienced by patients receiving epidural analgesia for postthoracotomy pain.