Management of temporary urinary retention after arthroscopic knee surgery in low-dose spinal anesthesia:: development of a simple algorithm

Introduction In practice, trauma and orthopedic surgery during spinal anesthesia are often performed with routine urethral catheterization of the bladder to prevent an overdistention of the bladder. However, use of a catheter has inherent risks. Ultrasound examination of the bladder (Bladderscan (R)) can precisely determine the bladder volume. Thus, the aim of this study was to identify parameters indicative of urinary retention after low-dose spinal anesthesia and to develop a simple algorithm for patient care. Materials and methods This prospective pilot study approved by the Ethics Committee enrolled 45 patients after obtaining their written informed consent. Patients who underwent arthroscopic knee surgery received low-dose spinal anesthesia with 1.4 ml 0.5% bupivacaine at level L3/L4. Bladder volume was measured by urinary bladder scanning at baseline, at the end of surgery and up to 4 h later. The incidence of spontaneous urination versus catheterization was assessed and the relative risk for catheterization was calculated. Mann-Whitney test, chi(2) test with Fischer Exact test and the relative odds ratio were performed as appropriate. *P < 0.05. Results Seventy percent of the patients were able to void spontaneously; in 30%, a Foley catheter had to be inserted because bladder volume exceeded 500 ml and/or urination was insufficient (P < 0.01). Bladder volume differed independently of the fluid infused. Additionally, patients with a bladder volume > 300 ml postoperatively had a 6.5-fold greater likelihood for urinary retention. Conclusion In the management of patients with short-lasting spinal anesthesia for arthroscopic knee surgery we recommend monitoring bladder volume by Bladderscan (R) instead of routine catheterization. Anesthesiologists or nurses under protocol should assess bladder volume preoperatively and at the end of surgery. If bladder volume is > 300 ml, catheterization should be performed in the OR. Patients with a bladder volume of < 300 ml at the end of surgery may be transferred to the ward or recovery room. In these patients, bladder volume must be checked at least every 60 min for a maximum of 3 h or until spontaneous voiding is possible or bladder volume is > 500 ml.