Low Versus Standard Urine Output Targets in Patients Undergoing Major Abdominal Surgery: A Randomized Noninferiority Trial
To determine whether a low perioperative minimum urine output target is safe and fluid sparing when compared with the standard target.Background:
A minimum hourly urine output of 0.5 mL/kg is a key target guiding perioperative fluid therapy. Few data support this standard practice, which may contribute to perioperative fluid overloading.Methods:
We randomized patients without significant risk factors for acute kidney injury undergoing elective colectomy to a minimum urine output target of 0.2 mL/kg/h (low group) or 0.5 mL/kg/h (standard group) from induction of anesthesia until 8 AM 2 days after surgery. Maintenance fluids were standardized and additional fluids administered to achieve the targets. Primary outcome was noninferiority for urine neutrophil gelatinase-associated lipocalin on the day after surgery.Results:
Between November 21, 2011 and July 11, 2013, 40 participants completed the study. The low group received 3170 mL (95% confidence interval 2380–3960) intravenous fluids versus 5490 mL (95% confidence interval 4570–6410) in the standard group (P = 0.0004), and was noninferior for neutrophil gelatinase-associated lipocalin [14.7 μg/L (interquartile range 7.60–28.9) vs 18.4 μg/L (interquartile range 8.30–21.2); Pnoninferiority = 0.0011], serum cystatin C (Pnoninferiority < 0.0001), serum creatinine (Pnoninferiority = 0.0004), and measured glomerular filtration (Pnoninferiority = 0.0003). Effective renal plasma flow increased in both groups after surgery, and more in the standard group (Pnoninferiority = 0.125).Conclusions:
A perioperative urine output target of 0.2 mL/kg/h is noninferior to the standard target of 0.5 mL/kg/h and results in a large intravenous fluid sparing. This target should be adopted in surgical patients without significant kidney injury risk factors.