Does thoracic epidural analgesia increase urinary retention post thoracotomy?

Introduction: Urinary retention is a common side effect of both opioids and local anesthetics when delivered epidurally, although this is most often described when delivered at the lumbar levels. The effects of a thoracic epidural infusion tend to be limited to the thoracic dermatomes and patients usually maintain normal sensation and motor function of their lower limbs. As parasympathetic innervation of the bladder originates at the sacral level, a higher block should spare any resulting bladder dysfunction. The aim of this study is to determine if urinary retention is a significant side effect requiring intervention when a thoracic epidural infusion of local anesthetic and opioid is used for post-thoracotomy pain control. Methods: After approval by our institution's ethics review board, a prospective study was initiated to answer this question. All patients undergoing thoracotomy were recruited for participation and, after informed patient consent, an epidural catheter was placed pre-operatively at the thoracic dermatomal level of the proposed surgery. All patients routinely have an indwelling urinary catheter placed during surgery. Post-operatively a solution of bupivacaine 0.05-0.1% and hydromorphone 10mcg/cc was infused at 8-12 cc/hr and continued for up to 5 days. The morning after surgery the urinary catheter was removed. Clean intermittent catheterizations (CIC) were performed if the patient could not void and an indwelling catheter would be placed if this persisted for 48 hours. The primary outcome recorded was the number of catheterizations required postoperatively. Prognostic value of pre-operative urinary symptomatology was also evaluated using the American Urologie Association Symptom Index (AUASI, 1). Results: In the first two months of the trial period we have accrued 10 patients, 2 of whom were eliminated for protocol violations. Of the remaining 8 patients, 4 (50%) had no difficulty voiding and did not require catheterization. Three patients (38%) required either 1 or 2 CIC prior to spontaneous voiding. One patient requested that an indwelling catheter be left in place after requiring 2 CIC. The AUASI has not been shown to be prognostic in this preliminary analysis. Discussion: Although these results are only preliminary, they suggest that many patients do not experience significant bladder dysfunction requiring prolonged catheterization with a thoracic epidural infusion of bupivacaine 0.05-0.1% and hydromorphone 10mcg/cc for post-thoracotomy analgesia.