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Low molecular weight synthetic colloid fluids, 6% hydroxyethyl starch 130/0.4 and 4% succinylated gelatine, interfere with refractometric tests of total protein concentration and urine specific gravity

Yam, Elodie (2018) Low molecular weight synthetic colloid fluids, 6% hydroxyethyl starch 130/0.4 and 4% succinylated gelatine, interfere with refractometric tests of total protein concentration and urine specific gravity. Masters by Research thesis, Murdoch University.

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Abstract

Synthetic colloids used to treat shock, including 6% hydroxyethyl starch 130/0.4 (HES) and 4% succinylated gelatine (GELO), may interfere with refractometry due to large colloid molecules within the solution. This study aimed to assess the effects of these fluids on refractometric total plasma protein concentration (TPPr) and urine specific gravity (USG), using an in vitro (TPPr only) and an in vivo dog model. In the in vitro study, plasma samples from 10 greyhounds were diluted with 0.9% sodium chloride (NaCl), HES and GELO in ratios of plasma: fluid, 9:1, 8:2, 7:3, 6:4, 5:5. TPPr was compared to total plasma protein measured by the biuret assay (TPPb) at these dilutions. As the volume of colloid fluid increased, magnitude of over-estimation of TPPb (NaCl) by TPPr (HES and GELO), and TPPb (GELO) also increased. In the in vivo model, 18 anaesthetised greyhounds were subjected to haemorrhagic shock for 60 minutes, followed by either 80 mL/kg of Plasmalyte-148 (CRYST), or 20 mL/kg of HES or GELO (n=6 per group) given IV over 20 minutes. TPPr and TPPb were measured before haemorrhage (Baseline), at end of shock (Shock), after completion of fluid (T20), then 40 minutes (T60), 100 minutes (T120) and 160 minutes (T180) later. USG and urine osmolality (UOsm) were measured at all time points except T20. Bias and 95% limits of agreement (LOA) for TPPr vs TPPb, measured UOsm (mUOsm) vs estimated UOsm (eUOsm) from USG were calculated. Peak bias (TPP) for HES (T20) was 1.622 g/dL (95% LOA 1.291−1.953 g/dL) and for GELO (T180) was 0.577 g/dL (95% LOA 0.207−0.947 g/dL). Peak bias (UOsm) for HES (T60) was 2995 mOsm/L (95% LOA 2032−3958 mOsm/L) and for GELO (T120) was 2465 mOsm/L (95% LOA 940−3990 mOsm/L). Our research shows that HES and GELO interfere with refractometric tests and refractometry should not be used within 3 hours of bolus synthetic colloid administration.

Item Type: Thesis (Masters by Research)
Murdoch Affiliation: School of Veterinary and Life Sciences
Supervisor(s): Smart, Lisa, Sharp, Claire and Hosgood, Giselle
URI: http://researchrepository.murdoch.edu.au/id/eprint/46176
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