The gray zone of the qualitative assessment of respiratory changes in inferior vena cava diameter in ICU patients

Abstract

IntroductionTransthoracic echocardiography (TTE) is a useful tool for minimally invasive hemodynamic monitoring in the ICU. Dynamic indices (such as the inferior vena cava distensibility index (dIVC)) can be used to predict fluid responsiveness in mechanically ventilated patients. Although quantitative use of the dIVC has been validated, the routinely used qualitative (visual) approach had not been assessed before the present study.MethodsQualitative and quantitative assessments of the dIVC were compared in a prospective, observational study. After operators with differing levels in critical care echocardiography had derived a qualitative dIVC, the last (expert) operator performed a standard, numeric measurement of the dIVC (referred to as the quantitative dIVC). Two groups of patients were separated into two groups: group (dIVC < 18%) and group (dIVC ≥ 18%).ResultsIn total, 114 patients were assessed for inclusion, and 97 (63 men and 34 women) were included. The mean sensitivity and specificity values for qualitative assessment of the dIVC by an intensivist were 80.7% and 93.7%, respectively. A qualitative evaluation detected all quantitative dIVCs >40%. Most of the errors concerned quantitative dIVCs of between 15% and 30%. In the dIVC <18% group, two qualitative evaluation errors were noted for quantitative dIVCs of between 0 and 10%. The average of positive predictive values and negative predictive values for qualitative assessment of the dIVC by residents, intensivists and cardiologists were 83%, 83%, and 90%; and 92%, 94%, and 90%, respectively. The Fleiss kappa for all operators was estimated to be 0.68, corresponding to substantial agreement.ConclusionThe qualitative dIVC is a rather easy and reliable assessment for extreme numeric values. It has a gray zone between 15% and 30%. The highest and lowest limitations of the gray area are rather tedious to define.Despite reliability of the qualitative assessment when it comes to extreme to numerical values, the quantitative dIVC measurement must always be done within a hemodynamic assessment for intensive care patients. The qualitative approach can be easily integrated into a fast hemodynamic evaluation by using portable ultrasound scanner for out-of-hospital patients.

COUNTERPOINT: Should Acute Fluid Resuscitation Be Guided Primarily by Inferior Vena Cava Ultrasound for Patients in Shock? No

“…Translational artifact during inspiration may be incorrectly interpreted as IVC variation (12). Some of these well-known technical challenges were ignored in studies validating IVC ultrasound (13).…”

Carotid artery corrected flow time measurement via bedside ultrasonography in monitoring volume status

“…Among these techniques, ultrasound evaluation of inferior vena cava seems to predict volume responsiveness with acceptable accuracy. However, its usage is limited by a diversity of techniques, lack of evidence-based cutoff points, and difficulties encountered while assessing patients with high abdominal fat deposition and excessive intestinal gas [7][8][9]. Another method is the assessment of descending thoracic aorta blood flow velocity waveform using a non-imaging esophageal Doppler probe.…”

Inferior vena cava guided fluid resuscitation – Fact or fiction?

“…35,36 This is influenced by patient factors such as obesity, intra-abdominal pathology such as distended bowel, or hyper-inflated lungs.…”