Comparison of superior vena cava and inferior vena cava diameter changes by echocardiography in predicting fluid responsiveness in mechanically ventilated patients

Resuscitation of critically ill patients requires an accurate assessment of the patient's intravascular volume status. Passive leg raise cause auto transfusion of fluid to the thoracic cavity.This study aims to assess and compare the efficacy of superior vena cava (SVC) and inferior vena cava (IVC) diameter changes in response to passive leg raise (PLR) in predicting fluid responsiveness in mechanically ventilated hemodynamically unstable critically ill patients.We enrolled 30 patients. Predictive indices were obtained by transesophageal and transthoracic echocardiography and were calculated as follows: (Dmax - Dmin)/Dmax for collapsibility index of SVC (cSVC) and (Dmax - Dmin)/Dmin for distensibility index of IVC (dIVC), where Dmax and Dmin are the maximal and minimal diameters of SVC and IVC. Measurements were performed at baseline and 1 min after PLR. Patients were divided into responders (increase in cardiac index (CI) ≥10%) and nonresponders (NR) (increase in CI <10% or no increase in CI).Among those included, 24 (80%) patients were R and six were NR. There was significant rise in mean arterial pressure, decrease in heart rate, and decrease in mean cSVC from baseline to 1 min after PLR among responders. The best threshold values for discriminating R from NR was 35% for cSVC, with sensitivity and specificity of being 100%, and 25% for dIVC, with 54% sensitivity and 86.7% specificity. The areas under the receiver operating characteristic curves for cSVC and dIVC regarding the assessment of fluid responsiveness were 1.00 and 0.66, respectively.cSVC had better sensitivity and specificity than dIVC in predicting fluid responsiveness.