Measuring plasma volume in women of reproductive age – a comparison study of hydroxyethyl starch to other methods of plasma volume measurements
Open Access
- Author:
- Martin, Leigh
- Graduate Program:
- Nutritional Sciences (MS)
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- February 27, 2023
- Committee Members:
- Alison D Gernand, Thesis Advisor/Co-Advisor
Lacy Marie Alexander, Committee Member
Meg Bruening, Program Head/Chair
Maria Rita Castro, Committee Member - Keywords:
- plasma volume
women's health
nutrition
biomarkers
hydroxyethyl starch
indocyanine green - Abstract:
- Background: Plasma volume (PV) is rarely measured, and further research is needed to understand if PV could be an important biomarker and how it may relate to other commonly measured clinical markers of nutritional status and health. Hydroxyethyl starch (HES) has previously been used to measure blood volume in pregnancy, but additional work and validation is needed for this method when measuring PV. Objectives: To 1) develop and evaluate a method to measure PV using HES; and to 2) examine relationships between PV measured by HES and key biomarkers of health (blood pressure, body mass index (BMI), body surface area (BSA), body fat percentage, and urine specific gravity) in healthy women of reproductive age. Research Design and Methods: We recruited a convenience sample of 12 healthy women of reproductive age for a cross-sectional comparison study. At enrollment, we collected data on demographics and key health biomarkers (blood pressure, BMI, body fat percentage, and urine specific gravity). For Aim 1, baseline blood samples were collected, followed by an injection of indocyanine green (ICG) and 5 serial blood samples collected over 5 minutes. An injection of HES followed, with 3 serial blood samples collected over 15 minutes. We constructed a dye dilution curve using the post-ICG injection samples to back-extrapolate and estimate PV at the time of injection. HES in plasma was assayed using a handheld glucometer to estimate PV at 5, 10, and 15 minutes post-injection. PV was then estimated using the Kaplan, Hurley, and Nadler equations. The HES PV at 10 minutes post-injection was compared to each of the other methods using the Bland-Altman method. For Aim 2, we used Spearman’s rank-order correlation to assess the correlation between PV measured by HES and each biomarker (blood pressure, BMI, BSA, body fat percentage, urine specific gravity). Results: A total of 12 participants had complete visit data and were included in the final analysis. Participants were 25.8 ± 7.5 years old with mean BMI of 21.7 kg/m2. They were predominantly white, non-Hispanic, college-educated, and never married. Almost all participants were nulliparous, and 58% reported using contraceptives. For Aim 1, the mean (SD) PV estimations were 2,046 (392) mL, 2,765 (820) mL, 2,443 (464) mL, 2,407 (301) mL, and 2,373 (406) mL, respectively. The mean differences between methods were -718 mL (HES versus ICG), -397 mL (HES versus Kaplan), -361 mL (HES versus Hurley), and -327 mL (HES versus Nadler). For Aim 2, we found that BSA and body fat percentage had Spearman’s rho of close to 0.3, but they were not statistically significant. The other correlations were close to 0.1 and not statistically significant. Conclusions: In a sample of healthy women of reproductive age, our comparison study showed that PV measured by HES was on average >300 mL different from other PV estimates (ICG and estimation equations). We also found no statistically significant correlations between PV and key biomarkers of health (blood pressure, BMI, BSA, and urine specific gravity). Additional research is needed to investigate PV in healthy individuals and develop sound methods for measurement.