ABSTRACT
REASONS FOR PERFORMING STUDY: Frusemide (Lasix) is commonly used diuretic in horse racing and equine clinical practice. While pharmacology, pharmacodynamics, renal and haematological effects of frusemide have been studied in horses, its effects on the distribution of fluid within the horse remain unknown. OBJECTIVE: To quantify the effects of frusemide on extracellular and intracellular fluid shifts. METHODS: Horses were infused with 1 mg/kg body mass (n = 7) or 2 mg/kg (n = 9) i.v. frusemide. Total body water (TBW), extracellular fluid volume (ECFV) and plasma volume (PV) were measured using D2O, NaSCN and Evans blue dilution. Change in ECFV was assessed from the change in plasma [protein] and from repeated infusion/dilution of NaSCN. RESULTS: Frusemide resulted in a 0.020 +/- 0.002 l/kg decrease in TBW within 120 min. At 120 min after frusemide infusion the ECFV losses were nearly double the TBW losses, therefore ECFV loss in excess of TBW loss is seen as an increase in ICFV. CONCLUSIONS: Frusemide resulted in a net shift of fluid (electrolytes and water) from the extracellular to intracellular fluid compartment. POTENTIAL RELEVANCE: The fluid shifts that occur within horses administered frusemide has not previously been characterised. The intracellular shift of fluid is of performance and clinical significance.
Subject(s)
Diuretics/pharmacology , Extracellular Fluid/drug effects , Furosemide/pharmacology , Horses/metabolism , Intracellular Fluid/drug effects , Animals , Body Fluid Compartments/drug effects , Body Fluid Compartments/physiology , Body Water/metabolism , Body Weight/drug effects , Body Weight/physiology , Dose-Response Relationship, Drug , Female , Indicator Dilution Techniques/veterinary , Infusions, Intravenous/veterinary , Male , Physical Conditioning, Animal/physiology , Plasma Volume/drug effects , Plasma Volume/physiology , Plasma Volume/veterinaryABSTRACT
The purposes of this study were 1) to determine the compartmentation of body water in horses by using indicator dilution techniques and 2) to simultaneously measure bioelectrical impedance to current flow at impulse current frequencies of 5 and 200 kHz to formulate predictive equations that could be used to estimate total body water (TBW), extracellular fluid volume (ECFV), and intracellular fluid volume (ICFV). Eight horses and ponies weighing from 214 to 636 kg had catheters placed into the left and right jugular veins. Deuterium oxide, sodium thiocyanate, and Evans blue were infused for the measurement of TBW, ECFV, and plasma volume (PV), respectively. Bioelectrical impedance was measured by using a tetrapolar electrode configuration, with electrode pairs secured above the knee and hock. Measured TBW, ECFV, and PV were 0.677 +/- 0.022, 0.253 +/- 0.006, and 0.040 +/- 0.002 l/kg body mass, respectively. Strong linear correlations were determined among measured variables that allowed for the prediction of TBW, ECFV, ICFV, and PV from measures of horse length or height and impedance. It is concluded that bioelectrical impedance analysis (BIA) can be used to improve the predictive accuracy of noninvasive estimates of ECFV and PV in euhydrated horses at rest.
