Evaluating the Normal Urine Output in the Postpartum Period: Have We Been Underestimating What Is Adequate? [24O]

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Abstract

INTRODUCTION:

During the postpartum period physiologic changes occur simultaneously with potentially life threatening conditions including postpartum hemorrhage and preeclampsia. We do not have well studied values for normal urine output in this period. The primary goal of this study was to determine the normal urine output in the immediate postpartum period.

METHODS:

We selected women scheduled for cesarean delivery with singleton, full term gestations and excluded patients with gestational hypertensive disorder, cardiovascular disease, pregestational diabetes, or evidence of postpartum hemorrhage. We recorded demographic data and urinary output for the first 24 hours postpartum.

RESULTS:

The geometric mean of urine output (UOP) at hour 1 (n=300) 118.7 cc/hr, 2 (n=267) 89.0 cc/hr, 3 (n=176) 85.1 cc/hr, 4 (n=90) 90.1 cc/hr with 95% CIs, (27.9–504.4), (26.8–295.7), (22.8–317.0), (19.9–407.1), respectively. We found that the average weight based at hour 1 (n=288) 1.4 cc/kg/hr, 2 (n=257) 1.06 cc/kg/hr, 3 (n=170) 1.03 cc/kg/hr, 4 (n=86) 1.09 cc/kg/hr with 95% CIs (0.3–6.5), (0.29–3.8), (0.25–4.1), (0.23–4.7), respectively. Averaging urine output over time and adjusted for weight the average at hour 4 (n=105) 1.2 cc/kg/hr, 8 (n=87) 1.07 cc/kg/hr, 12 (n=81) 1.3 cc/kg/hr, 24 (n=64) 2.03 cc/kg/hr with 95% CIs (0.38–3.9), (0.32–3.5), (0.42–4.0), (1.04–3.9).

CONCLUSION:

The average UOP in the immediate postpartum period ranges 1.03 to 1.40 cc/kg/hr which is higher than the value currently understood as acceptable. With the average urine output higher than the currently used minimum at each time interval, it is possible that a rate below 1.03 cc/kg/hr may be an indication of abnormal clinical status.

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