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Observational Study
. 2018 Sep 24;22(1):223.
doi: 10.1186/s13054-018-2163-1.

Net ultrafiltration intensity and mortality in critically ill patients with fluid overload

Raghavan Murugan  1   2   3 , Vikram Balakumar  4   5 , Samantha J Kerti  5 , Priyanka Priyanka  4   5 , Chung-Chou H Chang  4   5   6   7 , Gilles Clermont  5 , Rinaldo Bellomo  8 , Paul M Palevsky  4   6   9 , John A Kellum  4   5
Affiliations
Observational Study

Net ultrafiltration intensity and mortality in critically ill patients with fluid overload

Raghavan Murugan et al. Crit Care. .

Abstract

Background: Although net ultrafiltration (UFNET) is frequently used for treatment of fluid overload in critically ill patients with acute kidney injury, the optimal intensity of UFNET is unclear. Among critically ill patients with fluid overload receiving renal replacement therapy (RRT), we examined the association between UFNET intensity and risk-adjusted 1-year mortality.

Methods: We selected patients with fluid overload ≥ 5% of body weight prior to initiation of RRT from a large academic medical center ICU dataset. UFNET intensity was calculated as the net volume of fluid ultrafiltered per day from initiation of either continuous or intermittent RRT until the end of ICU stay adjusted for patient hospital admission body weight. We stratified UFNET as low (≤ 20 ml/kg/day), moderate (> 20 to ≤ 25 ml/kg/day) or high (> 25 ml/kg/day) intensity. We adjusted for age, sex, body mass index, race, surgery, baseline estimated glomerular filtration rate, oliguria, first RRT modality, pre-RRT fluid balance, duration of RRT, time to RRT initiation from ICU admission, APACHE III score, mechanical ventilation use, suspected sepsis, mean arterial pressure on day 1 of RRT, cumulative fluid balance during RRT and cumulative vasopressor dose during RRT. We fitted logistic regression for 1-year mortality, Gray's survival model and propensity matching to account for indication bias.

Results: Of 1075 patients, the distribution of high, moderate and low-intensity UFNET groups was 40.4%, 15.2% and 44.2% and 1-year mortality was 59.4% vs 60.2% vs 69.7%, respectively (p = 0.003). Using logistic regression, high-intensity compared with low-intensity UFNET was associated with lower mortality (adjusted odds ratio 0.61, 95% CI 0.41-0.93, p = 0.02). Using Gray's model, high UFNET was associated with decreased mortality up to 39 days after ICU admission (adjusted hazard ratio range 0.50-0.73). After combining low and moderate-intensity UFNET groups (n = 258) and propensity matching with the high-intensity group (n = 258), UFNET intensity > 25 ml/kg/day compared with ≤ 25 ml/kg/day was associated with lower mortality (57% vs 67.8%, p = 0.01). Findings were robust to several sensitivity analyses.

Conclusions: Among critically ill patients with ≥ 5% fluid overload and receiving RRT, UFNET intensity > 25 ml/kg/day compared with ≤ 20 ml/kg/day was associated with lower 1-year risk-adjusted mortality. Whether tolerating intensive UFNET is just a marker for recovery or a mediator requires further research.

Keywords: Dialysis; Fluid overload; Intensity; Mortality; Net ultrafiltration; Renal replacement therapy.

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Conflict of interest statement

Ethics approval and consent to participate

This project was approved by the University of Pittsburgh Institutional Review Board.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
a. Association between net ultrafiltration intensity and time to mortality. Kaplan–Meier failure plots by UFNET intensity for probability of death over 1 year from ICU admission in overall cohort (n = 1075). Red line, low-intensity UFNET (≤ 20 ml/kg/day); blue line, moderate-intensity UFNET (> 20 to ≤ 25 ml/kg/day); green line, high-intensity UFNET (> 25 ml/kg/day). Probability of death highest in low-intensity compared with moderate and high-intensity UFNET groups (log-rank p < 0.001). b. Association between net ultrafiltration intensity and risk-adjusted 1-year mortality. Shown are adjusted odds ratio with 95% CI for association between UFNET intensity and mortality. Increasing UFNET intensity associated with trend toward lower mortality. Odds ratios adjusted for differences in age, sex, race, BMI, history of liver disease and sequela from liver disease, admission for liver transplantation, admission for surgery, baseline glomerular filtration rate, Acute Physiology and Chronic Health Evaluation III score, presence of sepsis, use of mechanical ventilation, percentage of cumulative fluid overload before initiation of RRT, oliguria before initiation of RRT, time to initiation of RRT from ICU admission, MAP on first day of RRT initiation, cumulative vasopressor dose and cumulative fluid balance during RRT, first RRT modality and duration of RRT. ICU intensive care unit
Fig. 2
Fig. 2
Association between net ultrafiltration intensity and time to mortality in propensity-matched cohort. Kaplan–Meier failure plots by UFNET for probability of death over 1 year from ICU admission among patients with UFNET ≤ 25 ml/kg/day (n = 258) compared with propensity-matched patients with UFNET > 25 ml/kg/day (n = 258). Red line, UFNET ≤ 25 ml/kg/day; green line, UFNET > 25 ml/kg/day. Probability of death lower among patients who received UFNET > 25 ml/kg/day compared with UFNET ≤ 25 ml/kg/day (log-rank p < 0.001). ICU intensive care unit
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References

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