Fluid Overload and ICU Mortality

November 10, 2020

Written by Clay Smith

Spoon Feed
Excess IV fluid was associated with increased mortality in critically ill patients.

Why does this matter?
We used to flood patients with fluid during my residency. The dogma was, “You gotta swell to get well.” But 95% of each liter leaks out of the vascular space after an hour in critically ill patients. Fluid overload may impair renal function, prolong ventilation, and increase mortality.

You gotta swell to get well? Ummm…nope.
This was a systematic review and meta-analysis of observational studies. They did not meta-analyze the three RCTs for some reason. They considered ICU mortality at 72h associated with either fluid overload (FO; >5% weight gain) or positive cumulative fluid balance (CFB; i.e. intake > output). For the primary outcome of FO, there was an aRR 8.83 (95%CI 4.30-19.22; only 1 study). That’s high. For positive CFB, the combined 4 studies which adjusted for confounders yielded an aRR of 1.44 (1.18-1.77). Eight studies were combined and found a 19% greater risk of mortality for every excess liter of fluid; RR 1.19 (1.11-1.28). As a secondary outcome, the risk of mortality at any time point (not just 72h) was much greater in patients with FO or positive CFB. Also, mortality was greater in several subgroups with positive CFB: acute kidney injury, sepsis, respiratory failure, and surgical patients. Most of the studies were retrospective, with risk of confounding by indication – sicker patients get more fluid. Still, I think there is probably something real and concerning here.

Source
Fluid Overload and Mortality in Adult Critical Care Patients-A Systematic Review and Meta-Analysis of Observational Studies. Crit Care Med. 2020 Oct 1. doi: 10.1097/CCM.0000000000004617. Online ahead of print.

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Thanks to Don Arnold for statistical advice on this post.