(P07-037-23) Measuring Plasma Volume in Women of Reproductive Age – A Comparison Study of Hydroxyethyl Starch to Other Methods of Plasma Volume Measurements

Objectives: Current methods for measuring plasma volume (PV) have clear limitations and are not acceptable for use in certain populations, like pregnancy, when PV expansion is important for healthy pregnancy outcomes. We aimed to develop and evaluate a method to measure PV using hydroxyethyl starch (HES) in healthy women of reproductive age.

Methods: A convenience sample of healthy women (n = 12) of reproductive age were recruited for a comparison study using two PV indicator dilution methods – HES and indocyanine green (ICG). PV was also calculated using the Kaplan, Hurley, and Nadler equations. Baseline blood samples were collected, followed by an injection of ICG (0.25 mg/kg body weight) followed by 5 serial blood samples over 5 minutes. A bolus injection of HES followed and one blood sample was collected at 10 minutes post injection. Plasma ICG was determined via absorbance (wavelength) to construct a dye dilution curve. Plasma HES samples were acid hydrolyzed to measure glucose via glucometer. HES PV was compared to each of the other methods using Bland-Altman analysis.

Results: Participants had a mean age of 25.8 ± 7.5 years with a mean BMI of 21.7 ± 1.7 kg/m². They were predominantly nulliparous, non-Hispanic White, and college-educated. PV estimations for HES, ICG, Kaplan, Hurley, and Nadler methods were 2,046 ± 392 mL, 2,765 ± 820 mL, 2,443 ± 464 mL, 2,407 ± 301mL, and 2,373 ± 406 mL, respectively. The mean differences (and limits of agreement) from the Bland-Altman analyses between HES and the other methods were -718 mL (-2,185 mL, 748 mL) (ICG), -397 mL (-1,201 mL, 407 mL) (Kaplan), -361 mL (-1,106 mL, 383 mL) (Hurley), and -327 mL (-1,046 mL, 392 mL) (Nadler). In each analysis, differences for 11 participants were within the limits of agreement.

Conclusions: In a small pilot of healthy women of reproductive age, our comparison study showed that PV measured by HES was >300 mL different from other PV estimates, but had a narrow distribution within the expected range. Additional research is needed to investigate PV in healthy individuals and develop sound methods for measurement across populations, including pregnancy.

Funding Sources: Bill & Melinda Gates Foundation