Background: Low urine output (LUO) for six hours is defined as the stage that is at risk of acute renal failure. Major surgeries with a bloodless field, such as total knee arthroplasty (TKA), may be associated with LUO; however, there has been no study addressing this point. The present study evaluated the incidence of LUO and the effect of fluid balance on LUO in TKA patients during the first 24 hours after surgery.
Material and Method: The authors retrospectively evaluated 257 uncomplicated patients undergoing unilateral TKA during
the first 24 hours after surgery. Patients’ demographic data, intra-operative intravenous (IV) fluid replacement, postoperative
IV fluid replacement, oral fluid intake, total fluid intake, postoperative urine output, blood collected from the drain, and the total visible fluid output during the first 24 hours after surgery were collected and evaluated.
Results: The incidence of LUO was 19.1% (49/257) in the studied group. There were no significant differences in patients’ demographic data between the LUO and normal urine output (NUO) groups. Comparing the LUO and NUO groups, the
LUO group had a lower volume of intra-operative fluid replacement, with statistical significance. There were no differences in postoperative IV fluid replacement and postoperative oral fluid intake between groups. Although 80.5% of the studied group had IV fluid replacement at a less than ideal level, at discharge there was no patient suffering from renal complications related to LUO.
Discussion and Conclusion: Urine output is one of the common monitoring parameters of fluid balance in the perioperative period; it should be >0.5 mL/kg/h. Prolonged low urine output for six hours and for 12 hours are categorized as causing risk and injury to the kidney, respectively. The incidence of LUO at our institution during the first 24 hours after TKA is not uncommon and is significantly related to intra-operative fluid replacement. Fortunately, all LUO patients had further fluid replacement, resulting in no renal complications at discharge. As eighty percent of patients had less than ideal fluid replacement, and patients having LUO during the first 24 hours had a significantly lower volume of intra-operative fluid replacement, the authors propose reconsidering perioperative fluid replacement in TKA patients, especially intra-operative IV fluid to avoid LUO.

Keywords: Urine, Total knee arthroplasty, TKA, Fluid, Intravenous, Intake, Output