Ultrasound measurement of the inferior vena cava diameter to evaluate volume status in patients requiring fluid resuscitation at emergency department, Muhimbili National Hospital.

Abstract

Background: Hypotension in the emergency department is an independent predictor of in-hospital mortality. Monitoring fluid responsiveness is key for better prognosis of critically ill patients with hypotension and/or shock. Central venous pressure (CVP) is currently used as a standard measure of volume status, but monitoring of CVP is expensive, invasive, has complications and there is evidence in recent literature that CVP is ureliable predictor of volume status. Beside ultrasound of the inferior vena cava (IVC) has been proposed as a safe, non-invasive, and potentially more reliable, measure of volume status. It is not known whether bedside ultrasound measurement of volume status will predict fluid responsiveness with more clinically relevant parameters.

Aim of the study: To determine if ultrasound measurement of IVC diameter can predict fluid responsiveness in patients requiring fluid resuscitation at Emergency Medicine Department, MNH.

Methods: Prospective observational study of adult patients presenting at EMD-MNH with hypovolemia and requiring fluid resuscitation. A structured physician data sheet was used to record serial vital signs, measured IVC during initial fluid bolus, and the treating clinician’s impression of patient volume status and suspected cause of hypotension. Subjects were stratified by presenting Caval Index (CI) and clinical estimation of volume status. A T-test was used to compare the mean change in mean arterial pressure (MAP) per unit volume.

Results: A total of 364 patients were enrolled, 52.2% male and 48.8% female, the average age of (36.8 ±10.7) years and (35.9 ±14.0 )years respectively. 48.6% patients had a CI <50% and 51.4% patients had a CI ≥ 50%. Patients in a group with CI ≥ 50% had a 2.8 (p<0.0001) fold greater fluid responsiveness than patients with CI<50%. Caval Index (CI) was lower and volume responsiveness higher in patients who clinicians rated as moderate and severely dehydrated as compared with those rated mild, though there was a substantial overlap of CI and fluid responsiveness values in these clinical categories.

Conclusion and recommendation: Ultrasound measurement of the inferior vena cava diameter can predict fluid responsiveness in patients requiring intravenous fluids and may be useful to identify patients who will benefit from early and aggressive volume resuscitation. Ultrasound of the IVC is more effective for this purpose than clinical estimation of volume status. We recommend a feasibility study to assess if bedside ultrasound can be used consistently by a range of clinical providers as an adjunct tool to guide fluid resuscitation.