The effect of hetastarch (670/0.75) on urine specific gravity and osmolality in the dog.
BACKGROUND
Urine specific gravity (USG) is used clinically to estimate urine osmolality (UOsm). Although USG has been shown to have a linear correlation with UOsm in dogs, the relationship is altered when there are significant numbers of high molecular weight (MW) molecules in the urine.


OBJECTIVE
USG would no longer predict UOsm in dogs given intravenous hetastarch (670/0.75)(HES).


METHODS
Eight healthy employee-owned adult dogs.


METHODS
Prospective, controlled experimental study. USG and UOsm were measured every 30 minutes from t=0 minutes to t=360 minutes. Dogs were administered 20 mL/kg of either NaCl 0.9% (control group, n=4) or HES (treatment group, n=8) IV over 1 hour starting at t=90 minutes.


RESULTS
There was a decrease in UOsm in both groups starting at t=120 minutes and continuing for the study duration, and there was no significant difference in UOsm between treatment and control groups across all time points. There was an appropriate decrease in USG from t=120 minutes for the control group. In the treatment group, USG increased significantly at t=120 minutes (P= .0006), t=150 minutes (P= .0002), and t=180 minutes (P= .0044). The largest increase in USG occurred at t=150 minutes with a mean USG of 1.070 +/- 0.021 (range 1.038-1.104).


CONCLUSIONS
Urine specific gravity should not be used to estimate urine solute concentration in dogs following the administration of 20 mL/kg of HES. In a clinical setting, the evaluation of USG following this dose of HES may lead to an overestimation of urine concentration.
Smart
L
L
William R. Pritchard Veterinary Medical Teaching Hospital, University of California, Davis, CA 95616, USA. lsmart@ucdavis.edu
Hopper
K
K
Aldrich
J
J
George
J
J
Kass
P
P
Haskins
S
S
D000818:Animals; D004285:Dogs / Q000652:urine*; D005260:Female; D006895:Hydroxyethyl Starch Derivatives / Q000494:pharmacology*; D016014:Linear Models; D008297:Male; D009994:Osmolar Concentration; D010952:Plasma Substitutes / Q000494:pharmacology*; D011446:Prospective Studies; D013046:Specific Gravity / Q000187:drug effects; D014556:Urine / Q000737:chemistry
D006895:Hydroxyethyl Starch Derivatives; D010952:Plasma Substitutes