The effect of adding fentanyl to spinal anesthesia on the incidence of postoperative urinary retention

The prevalence of postoperative urinary retention is between 5% and 70%, depending on the type of surgery, the type and combination of anesthetics, and the patient's underlying conditions. Studies have shown that reducing the dose of local anesthetics in spinal anesthesia and the use of the drug combination reduces the incidence of urinary retention and the need for postoperative catheterization. This study was designed to evaluate the effect of adding fentanyl to spinal anesthesia on the incidence of postoperative urinary retention.

In a randomized clinical trial, patients who were candidates for lower limb orthopedic surgery or lower abdominal surgery under spinal anesthesia were enrolled. Patients with a history of urinary problems were not included. participants were excluded if a change in the method of anesthesia was intended, urinary catheterization required or urinary tract trauma occurred. Patients were randomly allocated to either spinal anesthesia with Bupivacaine 2-2.5 ml or spinal anesthesia with Bupivacaine 1.5-2 ml plus fentanyl 25 µg. Postoperative urinary retention was assessed based on the need for catheterization or a complaint of difficult or incomplete urination.

There was a significant borderline association between the complaints of incomplete (20 vs. 12 patients) or difficult urination (16 vs. 8 patients) after surgery and the addition of fentanyl to the spinal anesthesia. (P=0.05) There was no statistically significant relationship between the need for postoperative catheterization and the addition of fentanyl to the spinal anesthesia (20 vs. 13 patients; p=0.11). Logistic regression analysis showed that age and amount of fluid intake during surgery were independent predictors of difficult urination.

Adding fentanyl 25µg to local anesthetics in spinal anesthesia will increase the incidence of postoperative urinary retention. The use of lower doses of fentanyl in combination with various local anesthetic drugs in spinal anesthesia is recommended in future studies.