Change in End-Tidal Co₂ After Mini-Fluid Challenge to Determine Fluid Responsiveness

Distributive shock is a major cause of morbidity and mortality in the ICU. IV fluid resuscitation is a vital intervention to improve cardiac output and end-organ perfusion during the initial resuscitation and for those who remain fluid responsive. Noninvasive measures of fluid responsiveness are lacking. The aim of this study is to assess whether changes in end-tidal co₂ after mini-fluid challenge, or 250 mL bolus, can predict fluid responsiveness in mechanically ventilated patients with distributive shock.

Single-center prospective study.

Patients were enrolled from 2019 to 2021 from the medical ICU within a single academic hospital.

Thirty-eight patients with paired measurements of fluid responsiveness as determined by bioreactance who were admitted to the ICU with a diagnosis of distributive shock and on mechanical ventilation.

Stroke volume index (SVI), cardiac index, heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, and ETco₂ were measured before and after completion of a mini-fluid challenge. Test characteristics of change in ETco₂ (ΔETco₂) greater than or equal to 2 after mini-fluid challenge to determine fluid responsiveness were calculated with percentage change in SVI greater than or equal to 10% used as the reference standard.

The sensitivity and specificity of a ΔETco₂ greater than or equal to 2 mm Hg as a predictor of a change in SVI greater than or equal to 10% following a mini-fluid challenge were 20.0% and 91.3%, respectively. The area under the receiver operating characteristic curve was 0.62.

A ΔETco₂ greater than or equal to 2 mm Hg after mini-fluid challenge has limited test performance for determining fluid responsiveness in intubated patients with distributive shock.