BACKGROUND: In a previous observational study, thoracic epidural analgesia (TEA) after open renal surgery resulted in clinically relevant postvoid residuals (PVRs). This study aimed to investigate the individual contribution of epidurally administrated drugs and surgery in bladder dysfunction.
METHODS: In this single-center, parallel-group, randomized (computer-generated list), double-blind superiority trial, 40 patients undergoing open renal surgery were equally allocated to receive epidural bupivacaine (0.125%) alone or with fentanyl (2 µg/ml). Patients underwent urodynamic investigations before TEA and during TEA preoperatively and postoperatively. Primary outcome was the difference (Δ) in PVR between before TEA and postoperatively during TEA. Secondary outcomes were changes in detrusor pressure at maximum flow rate, bladder compliance, and ΔPVR between different time points.
RESULTS: Median ΔPVR (ml) from baseline to postoperatively was 180 (range, -85 to 645; P = 0.001) in the bupivacaine group and 235 (range, 0-580; P value less than 0.001) in the bupivacaine/fentanyl group, with no difference between groups (95% confidence interval, -167 to 103; P = 0.634). Detrusor pressure at maximum flow rate (cm H(2)O) from baseline was more pronounced in the bupivacaine/fentanyl than that in the bupivacaine group preoperatively (-10; range, -64 to -2; P value less than 0.001 vs. -3; range, -35 to 13; P = 0.397) (P = 0.045) and postoperatively (-18; range, -64 to 0; P value less than 0.001 vs. -12; range, -34 to 22; P = 0.006) (P = 0.135). Surgery did not affect PVRs, but a decreased bladder compliance was observed in both groups. No adverse events occurred.
CONCLUSIONS: Thoracic epidurally administrated bupivacaine resulted in clinically relevant PVRs based on impaired detrusor function. The addition of fentanyl enhanced this effect without generating greater PVRs. After surgery, the voiding phase was not further impaired; however, bladder compliance was decreased.