Change in stroke volume in response to fluid challenge: assessment using esophageal Doppler

Objective: To compare two methods of assessing a change in stroke volume in response to fluid challenge: esophageal Doppler and thermodilution with the pulmonary artery catheter. Design: Prospective study. Setting: Department of Intensive Care of a university medical center. Patients: 19 adult patients, intubated and sedated, with a pulmonary catheter and a clinical indication for a fluid challenge. Interventions: Two examiners independently assessed the effect of a fluid challenge on stroke volume and cardiac output with esophageal Doppler. Thermodilution performed by an independent clinician was used as the reference. Between-method variation and interobserver variability of the Doppler method were assessed. Measurements and results: There were no differences in stroke volume and cardiac output before volume challenge when measured with either of the two methods or by the two examiners using the esophageal Doppler. Despite a small bias between the methods and the two examiners using the esophageal Doppler (overall bias for cardiac output 0.3 l/min), the precision was poor (1.8 l/min). Conclusions: The esophageal Doppler method is a non-invasive alternative to the pulmonary artery catheter for the assessment of stroke volume in critically ill patients. Measurement of stroke volume response to fluid challenge using esophageal Doppler shows substantial interobserver variability. Despite the poor precision between methods and investigators, similar directional changes in stroke volume can be measured.