Background: Thoracic epidural analgesia with bupivacaine resulted in clinically relevant postvoid residuals due to detrusor underactivity. This study aimed to compare the risk of bladder dysfunction with ropivacaine versus bupivacaine using postvoid residuals and maximum flow rates. Our hypothesis was that ropivacaine would result in lower postvoid residuals, because ropivacaine has been shown to have less effect on motor blockade.
Methods: In this single-center, parallel-group, randomized, double-blind superiority trial, 42 patients undergoing open renal surgery were equally allocated to receive epidural bupivacaine 0.125% or ropivacaine 0.2%, and 36 were finally included. Inclusion criterion was normal bladder function. Patients underwent urodynamic investigations preoperatively and during thoracic epidural analgesia. Primary outcome was the difference in postvoid residual preoperatively and during thoracic epidural analgesia postoperatively. Secondary outcomes were changes in maximum flow rate between and within the groups.
Results: Median difference in postvoid residual (ml) from baseline to postoperatively was 300 (range, 30 to 510; P < 0.001) for bupivacaine and 125 (range, -30 to 350; P = 0.011) for ropivacaine, with a significant mean difference between groups (-175; 95% CI, -295 to -40; P = 0.012). Median difference in maximum flow rate (ml/s) was more pronounced with bupivacaine (-12; range, -28 to 3; P < 0.001) than with ropivacaine (-4; range, -16 to 7; P = 0.025) with a significant mean difference between groups (7; 95% CI, 0 to 12; P = 0.028). Pain scores were similar. No adverse events occurred.
Conclusions: Postvoid residuals were significantly lower using ropivacaine compared to bupivacaine for thoracic epidural analgesia reflecting less impairment of detrusor function with ropivacaine.