Ultrasound Assessment of Fluid Tolerance in Critically Ill Patients: Epidemiology of Systemic and Pulmonary Congestion

Abstract

Objective: By using lung ultrasound and Venous Excess Ultrasound Grading System (VExUS) to assess fluid tolerance, four congestion types can be identified: fluid tolerant (no congestion), pulmonary congestion, systemic congestion and both pulmonary and systemic congestion. The primary aim is to describe the epidemiology of these congestions types.

Methods: This is a pre-planned secondary analysis of a prospective observational cohort study. Fluid tolerance was defined as absence of congestion on ultrasound. Pulmonary congestion was defined as a bilateral B-profile. Systemic congestion was defined as VExUS ≥ 2, and pulmonary and systemic congestion were used when both were present. Primary outcome was the prevalence of congestion types. Secondary outcomes were associations between congestion types, associations with left (LVF) and right ventricular function (RVF) and cumulative fluid balance.

Results: A total of 87 (63%) of 138 patients were fluid tolerant, 36 (27%) had pulmonary congestion, 8 (6%) systemic congestion and 7 (5%) both pulmonary and systemic congestion. Between the first and second measurement 16 out of 87 (18%, 95% CI: 11%-28%) fluid tolerant patients developed pulmonary congestion and 8 out of 36 (22%, 95% CI: 11%-40%) patients with pulmonary congestion switched to fluid tolerance. No association was found between pulmonary and systemic congestion. A positive association was found for reduced LVF and pulmonary congestion (OR 2.1 [95% CI: 1.03-4.6]), and reduced RVF and systemic congestion OR 4.3 (95% CI: 1.5-15.6). No association between cumulative fluid balance and any type of congestion was found.

Conclusion: Most critically ill patients are fluid tolerant at admission. Pulmonary congestion is the most prevalent congestion type. Pulmonary and systemic congestion seldom occur simultaneously; therefore, both need to be assessed.

Keywords: Fluid tolerance; Lung ultrasound; Point-of-care ultrasound; VExUS.