Inferior vena cava assessment in term pregnant women using ultrasound: A comparison of the subcostal and right upper quadrant views.

Abstract

Point-of-care ultrasound can be used at the bedside to assess the haemodynamic status and fluid responsiveness of a pregnant woman. Previous studies demonstrated that views from the apical and parasternal windows are readily obtainable in labouring women. However, using the subcostal window to assess the inferior vena cava can be challenging because of the gravid uterus. A potential alternative is the right upper quadrant transhepatic window. We sought to compare visualisation of the inferior vena cava via the subcostal and right upper quadrant windows, in full-term pregnant women. This was a prospective pilot study carried out in a tertiary academic obstetric centre. Thirty pregnant non-labouring women at full term were recruited. In each patient, the inferior vena cava was visualised through both the subcostal and the right upper quadrant windows. Time to acquire each image, acquisition success rates and ease of obtaining images were compared for both approaches. Image quality was then reviewed and rated by two independent expert reviewers. There was a significant difference in the time required to obtain each view; subcostal median (interquartile range): 52 (35-59) seconds, right upper quadrant median (interquartile range): 23 (11-55) seconds (P=0.0045). Operator-defined successful image acquisition was 100% for the right upper quadrant window compared to 80% for the subcostal window. Ease of obtaining the view, as rated by the operator, was significantly easier in the right upper quadrant window compared to the subcostal window (P <0.0001). Both reviewers independently rated image adequacy to be significantly greater in the right upper quadrant window (73% and 57%) compared to the subcostal window (40% and 10%) (P=0.0213 and P=0.0005, respectively). Inter-rater agreement ranged between good (Cohen's kappa coefficient 0.64) for right upper quadrant windows to fair (Cohen's kappa coefficient 0.29) for subcostal windows. Inferior vena cava visualisation in term pregnant patients may take less time, be easier and provide better quality images when the right upper quadrant window is used compared to the subcostal window.