Unilateral Anesthesia Does Not Affect the Incidence of Urinary Retention After Low-Dose Spinal Anesthesia for Knee Surgery

We evaluated whether unilateral low-dose spinal anesthesia may reduce the likelihood of postoperative urinary retention. Forty patients scheduled for knee arthroscopy randomly received bilateral (n = 20) or unilateral (n = 20) spinal anesthesia with 6-mg hyperbaric bupivacaine 0.5%. The incidence of urinary retention (>500 mL) assessed with an ultrasound device (Bladderscan) and subsequent temporary catherization was 7/20 patients in the bilateral versus 6/20 in the unilateral group (not significant). We concluded that unilateral low-dose spinal anesthesia does not further decrease the likelihood of urinary retention. Our results demonstrate the value and necessity of monitoring bladder volume postoperatively.