Effects of Thoracic Epidural Administered Ropivacaine Versus Bupivacaine on Bladder Function

Acute urinary retention is one of the most common complications after surgery and anesthesia. Micturition depends on coordinated actions between the detrusor muscle and the external urethral sphincter. Under the influence of epidural analgesia, patients may not feel the sensation of bladder filling, which can result in urinary retention and bladder overdistension. Overfilling of the bladder can stretch and in some cases permanently damage the detrusor muscle. Because epidural anesthesia can be performed at various levels of the spinal cord, it is possible to block only a portion of the spinal cord (segmental blockade). Thoracic epidural analgesia with bupivacaine significantly inhibits the detrusor muscle during voiding, resulting in clinically relevant post void residuals which required monitoring or transurethral catheterisation. This bladder muscle inhibition is comparable to a motor blockade. The epidural administration of ropivacaine during labour results in a clinically relevant reduction of motor blocks. The hypothesis is that thoracic epidural analgesia with the local anesthetics ropivacaine leads to less significant changes in bladder function than bupivacaine as a control group, in patients undergoing lumbotomy incision for renal surgery.