(675) Understanding Fluid Shifts in Hypertension: Postpartum Point-of-Care Ultrasound of the Inferior Vena Cava and Aorta

Assessment of the inferior vena cava (IVC) and aorta using point-of-care ultrasound to estimate central venous pressure (CVP) is a commonly used practice across medical specialties. Our objective is to study postpartum fluid dynamics using IVC collapsibility and aorto-caval (IVC:Ao) indices measured on postpartum days (PPD) 1-3; and to compare changes in IVC collapsibility and IVC:Ao indices between postpartum patients with and without hypertensive disorders of pregnancy (HDP). Our hypothesis is postpartum patients with HDP will have lower IVC collapsibility and higher IVC:Ao indices than controls, signifying hypervolemia.


Study Design: Prospective cohort study of postpartum singleton pregnancies delivered 24 to 41+6 weeks gestation with and without HDP conducted from 2020-23. Standardized ultrasound measurements of the IVC and aorta were performed daily starting PPD1 through PPD3. The primary outcomes were IVC collapsibility and IVC:Ao index. Individual IVC and aorta measurements were secondarily evaluated.

Results: 123 (62 control and 61 HDP) postpartum participants were included in our analysis. HDP patients received more IV fluids than controls. IVC collapsibility was similar between groups across PPD 1-3. IVC:Ao index was significantly lower in hypertensive patients on PPD 1 (1.25 + 0.3 vs 1.1 + 0.3; p=0.003). HDP patients had significantly smaller IVC maximum diameter on PPD 1 (2.0 + 0.4 cm vs 1.78 + 0.5 cm; p=0.004). Indices between the two groups did not differ on PPD 2 and 3. Secondary analysis showed patients with preeclampsia with severe features had lower IVC:Ao indices compared to controls (1.25 + 0.3 vs 1.03 + 0.4; p=0.006).

Conclusion:

Postpartum patients with HDP showed a lower IVC:Ao index and smaller IVC diameters on PPD 1, correlating with a lower CVP compared to controls despite receiving more IV fluids. The indices increased on PPD 2 and 3, which may signify fluid mobilizing to the intravascular space. Bedside point-of-care evaluation of the IVC and aorta can help providers understand postpartum fluid dynamics and may help identify candidates for diuresis.