# The Urine Output Response to Low-Dose Diuretic Challenge Predicts Tolerance to Negative Fluid Balance in Mechanically Ventilated, Critically Ill Patients

## TL;DR

This study shows that urine output after a low-dose diuretic can predict whether critically ill, ventilated patients can safely handle fluid removal.

## Contribution

The study introduces a new method to predict tolerance to negative fluid balance using early urine output after diuretic use in ventilated patients.

## Key findings

- 80% of ventilated patients were tolerant to negative fluid balance.
- Cumulative urine output over four hours after diuretic use best predicted NFB tolerance with an AUC of 0.83.
- Each 100-mL increase in four-hour urine output was associated with a 1.53-fold higher odds of NFB tolerance.

## Abstract

Background and objective

Although early diuretic use and negative fluid balance (NFB) have been associated with lower mortality in mechanically ventilated patients, some patients are not tolerant to NFB. Little is known about whether urine output response after the diuretic administration predicts NFB tolerance in mechanically ventilated patients. Hence, we conducted this study to look into this.

Methods

This was a single-center, prospective, observational study. We included mechanically ventilated patients who were hemodynamically stable with bilateral pulmonary opacities on chest radiography and planned to be diuresed per our fluid removal protocol. In the protocol, a low dose of furosemide adjusted to each patient’s estimated glomerular filtration rate (eGFR) was administered, and then we started to measure urine outputs hourly for four hours. Tolerance to NFB was defined as “absence of hypotension, fluid resuscitation and vasopressors use, and acute kidney injury during fluid removal”. We investigated whether the urine output predicts the tolerance to NFB during fluid removal treatment.

Results

A total of 60 mechanically ventilated patients were included. Notably, 80% (48/60) of the patients were tolerant to NFB. All hourly and cumulative urine output measurements during the first four hours after the first diuretic administration were significantly higher in the NFB-tolerant group than in the non-tolerant group. Among all hourly and cumulative urine output measurements, the first four-hour cumulative urine output showed the highest area under the receiver operating characteristic curve (AUC) of 0.83 for predicting the tolerance to NFB. Multivariate logistic regression analysis adjusted for the urine output two hours before the diuretic use showed that each 100-mL increase in the first four-hour cumulative urine output was significantly associated with an increased odds ratio (OR) of the tolerance to NFB [adjusted odds ratio (aOR): 1.53; 95% CI: 1.11-2.15].

Conclusions

Based on our findings, the first four-hour cumulative urine output after the first low dose of diuretic administration might help predict tolerance to NFB during fluid removal treatment in mechanically ventilated, critically ill patients.