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Pre‐Race Administration of Furosemide Induces a Linear Dose‐Dependent Increase in Plasma Total CO 2 Concentration in Thoroughbred Racehorses
Author(s) -
Demaree A,
Couetil L,
Constable P
Publication year - 2014
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/evj.12267_6
Subject(s) - furosemide , jugular vein , medicine , metabolic alkalosis , horse , chemistry , anesthesia , biology , paleontology
Furosemide is widely administered in North America for the prophylactic treatment of exercise‐induced pulmonary hemorrhage. Plasma total CO 2 concentration (ct CO 2 ) provides a clinically useful screening test for the presence of metabolic acid‐base disturbances, including the pre‐race administration of alkalinizing agents to racehorses. Some racing jurisdictions account for the metabolic alkalosis and increased plasma ct CO 2 induced by furosemide administration. The purpose of this study was to determine the relationship between pre‐race furosemide dose and pre‐race plasma ct CO 2 in Thoroughbred racehorses. Methods Jugular venous blood was collected anaerobically into 3 mL partially evacuated plastic tubes containing lithium heparin from 226 Thoroughbred horses administered a variable dose of furosemide (150–500 mg IV , n = 217) 3–4 hours previously or not administered furosemide (n = 9). Plasma ct CO 2 was calculated from the measured values for pH and p CO 2 using a blood gas and pH analyzer [Radiometer ABL 700] and the Henderson‐Hasselbalch equation. Data was analyzed using multivariable linear regression and P<0.05 was significant. Plasma ct CO 2 in mmol/L increased linearly (P = 0.0006) with furosemide dose in milligrams adjusted for sex (female, stallion, gelding), such that ct CO 2 = 33.38 − 0.71(if female) − 0.63(if stallion) + 0.0040 × (furosemide dose). Conclusions Intravenous administration of furosemide (150–500 mg) produces a linear dose‐dependent increase in ct CO 2 in plasma. High intravenous doses of furosemide (500 mg) have the potential to increase plasma ct CO 2 to near the threshold value used to identify the pre‐race administration of alkalinizing agents. This finding supports an allowance of 2.0 mmol/L for furosemide administration used by some racing jurisdictions in North America. Ethical Animal Research Samples and data were collected during race day procedures currently in place. Explicit owner informed consent for participation in this study is not stated. Sources of funding: Indiana Horse Racing Commission. Competing interests: none.