Fluid Bolus in Asthma - Helpful or Harmful?

Spoon Feed
Too much fluid in pediatric asthma is a bad thing, leading to worse clinical outcomes and increased interstitial lung water. For each 1% fluid overload, patients spent 7 additional hours in the hospital.
Fluid overload % = (Fluid in (L) - Fluid out (L))/admission weight (kg)

Why does this matter?
Asthma causes an increase in work to exhale, but less well known is that it also causes an even more dramatic swing in negative intrapleural pressure during inspiration.  This favors movement of water from the vascular space to the interstitium, which may worsen lung function and oxygenation.  Adding more water may make things worse, so these authors sought to find out if this was true.  Often, we give boluses of IV fluid to children with severe asthma exacerbation.  Is this helpful or harmful?

Soggy lungs - sad lungs
This was both a retrospective and prospective study.  In the large retrospective arm with 1175 patients, they found that children with a positive fluid balance (more in than out), had poorer outcomes, namely longer stay and more supplemental oxygen use.  In the prospective validation arm with 123 rhinovirus-related asthma exacerbations, they found the same and also found evidence of increased interstitial (extravascular) lung water on ultrasound.  The key finding was that for each 1% fluid overload*, patients spent 7 additional hours in the hospital and 2 additional hours on supplemental oxygen. While it is OK to replace a fluid deficit in acute pediatric asthma exacerbation, this study suggests that excess fluid does harm.
*Fluid overload % = (Fluid in (L) - Fluid out (L))/admission weight (kg)

Source
Fluid Balance is Associated with Clinical Outcomes and Extravascular Lung Water in Children with Acute Asthma Exacerbation. Am J Respir Crit Care Med. 2018 Jan 9. doi: 10.1164/rccm.201709-1860OC. [Epub ahead of print]

Peer reviewed by Thomas Davis, MD.

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