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No clear consensus exists on the threshold for performing bladder catheterization in patients who develop urinary retention postoperatively. In this randomized trial, Danish researchers compared 500-mL and 800-mL bladder volume thresholds for urinary catheterization following total hip or total knee replacement in 800 patients (median age, 69; 50% women). Bladder ultrasound scans were performed every 2 hours postoperatively. When bladder volume reached the randomized threshold (500 or 800 mL), patients were encouraged to void and were catheterized if they were unable to do so. General standards of care in these patients included spinal anesthesia (85%), avoidance of intraoperative urinary catheters, multimodal opioid-sparing postoperative analgesia, and early mobilization.
The proportion of patients who required urinary catheterization was significantly higher in the 500-mL group than in the 800-mL group (32% vs. 13% in a per-protocol analysis; 30% vs. 19% in an intent-to-treat analysis). At 30 days, no differences were found between groups in incidence of urinary infection (2% in each group) or in standardized urinary symptom scores.
Bjerregaard LS et al. Postoperative urinary catheterization thresholds of 500 versus 800 ml after fast-track total hip and knee arthroplasty: A randomized, open-label, controlled trial. Anesthesiology 2016 Jun; 124:1256. (http://anesthesiology.pubs.asahq.org/article.aspx?articleid=2513988)
Comment
In this study, waiting until bladder volume reached 800 mL (vs. 500 mL) was not harmful, and it resulted in catheterization of substantially fewer patients. The proportions of patients requiring bladder catheterization at these thresholds — and the proportions with urinary complications — might differ after other types of surgery and in settings with more liberal use of opioid analgesia postoperatively.