Qualitative Assessment of the Inferior Vena Cava: Useful Tool for the Evaluation of Fluid Status in Critically Ill Patients

Abstract

Inferior vena cava (IVC) diameter change on limited transthoracic echocardiogram (LTTE) can provide a useful guide of fluid status evaluation in critically ill patients. Institutional review board approval was obtained. Prospective evaluation of hemodynamic status was performed in hypotensive patients via LTTE. Images were obtained using an ultrasound machine without M-mode capability. Qualitative assessment of the IVC was obtained via subxyphoid window. FLAT IVC was defined as diameter less than 2 cm and FAT IVC when the vein was equal or larger than 2 cm. Collapsibility was assessed by observing respiratory variation of the vessel. Lactate was measured before and after therapy was initiated. A follow-up LTTE was obtained after fluid challenge. A total of 108 LTTE were performed. Patients’ age ranged from 18 to 89 years with an average of 53. Admission diagnosis was blunt trauma in 66 patients, penetrating trauma in 17, whereas 25 had nontraumatic intra-abdominal emergency. Sixty-nine patients were receiving mechanical ventilation at time of LTTE. Seventy-three patients had a FLAT IVC, and received fluid challenge as therapy. All patients had a change in IVC volume from “FLAT” to “FAT” after the fluid challenge. Seventy-one patients (97%) had resolution of hypotension after the first fluid challenge. Two patients had persistent hypotension and received a second fluid challenge. Follow-up LTTE demonstrated a FAT IVC and lack of collapsibility. Lactate decreased in all 73 patients after therapy guided by LTTE ( P < 0.00001) Evaluation of the IVC diameter via LTTE offers a rapid, non invasive way to evaluate fluid status in critically ill patients.