Effect of torsemide on serum and urine electrolyte levels in dogs with congestive heart failure

TORSEMIDE is a loop diuretic of the pyridine-sulfonylurea class. It is one of the most powerful loop diuretics, and clinical trials in human beings have proven its efficacy due to the greater elimination of sodium and water in urine than that provided by furosemide, with a much lower loss of potassium (Dunn and others 1995). Although there are several trials providing evidence of ion excretion by torsemide in human medicine (Goebel 1993, Patterson and others 1994, Stringer and others 1994, Blose and others 1995, Dunn and others 1995, Fowler and Murray 1995, Vargo and others 1995) there have been no reports in the veterinary literature. This short communication describes a study to assess the effect of 28 days’ treatment with torsemide on serum and urine electrolytes in dogs with moderate to severe congestive heart failure (CHF) due to chronic valve disease. Eighteen dogs with CHF secondary to chronic volume overload caused by chronic valve disease, classified as phase 2 to 3 according to the Scandinavian modified New York Heart Association classification (Kvuart and others 2002), were studied by the Cardiology Service of the Faculty of Veterinary Medicine, Complutense University, Madrid; consent was obtained from all the owners. The diagnosis of chronic valvular disease was made based on the dog’s clinical history, complete physical examination, six-lead electro cardiographic study, radiological study and echocardiographic study. Peripheral blood pressure was measured using a non-invasive indirect oscillometric method (Dinamap), and blood and urine analyses, including specific gravity, were performed in order to rule out dogs with disease other than CHF. The dogs had not received any other treatment for heart failure within two months before entering the trial. Patients with signs of other systemic disease were excluded. The dogs were randomly assigned to a treatment group or a control group, and all dogs were also treated with 0·2 mg/kg angiotensin converting enzyme (ACE) inhibitor, perindopril (Coversyl; Sevier) orally once a day, for the duration of the study. In the treatment group (10 dogs), 0·2 mg/kg torsemide (Sutril; Ferrer grupo) was administered orally, in one daily morning dose. The control group comprised eight dogs that received perindopril alone. Only one of the investigators was aware of which animals were in which group. All the dogs were fed three times a day with a commercial low-sodium diet (k/d; Hill’s) according to the manufacturer’s instructions, taking into account the bodyweight of each dog; water was given ad libitum. Blood samples and urine samples for ion measurement were taken from all the dogs on day 0 and on day 28 at the end of the study period. The blood samples were taken from the jugular vein and the urine samples were obtained using a bladder catheter. The last blood and urine samples were collected between two and four hours after oral ingestion of the medicines. The levels of sodium, potassium and chloride ions were determined using an ion analyser (Krone Microlyte), the level of calcium was determined by a cresolftaleina-complexona method using a kit (Calcio-Boehringer Mannheim), the level of phosphorus was determined using the molibdato test for ultraviolet (Boehringer Mannheim) and the level of magnesium was determined by colorimetric assessment without deproteinisation using a kit (bioMerieux). The excretion fraction was calculated to determine the concentration of ions in the urine. All the dogs were reviewed weekly, and a record was kept of possible secondary effects or intolerance to treatment, especially hypotension, anorexia or an increase in cardiac clinical signs. Statistical analysis was carried out using the program SPSS v 12.0 (Statistical Software). Mean values were compared using the parametric Student’s t test. The results were expressed as the mean (sd) values; in all cases, the results were considered statistically significant if P<0·05. The distributions of age, gender and bodyweight of the dogs included in the study were similar in both groups. The initial levels of the serum and urine ion levels in both groups were not significantly different. There was also no change in the serum and urine levels of the measured ions in the control group after treatment. There was no statistically significant change in the serum levels of the measured ions in dogs treated with torsemide after treatment with respect to their initial values, except for a slight decrease in the level of chloride ions. There was no difference in the serum levels of the measured ions between the groups after four weeks of treatment (Table 1). However, there was an increase in the urinary fractional excretion of potassium and magnesium in the dogs treated with torsemide compared with pretreatment values and with respect to the control dogs (Table 2). There were no statistically significant differences in the urinary fractional excretion of phosphorus, calcium and sodium compared with either the pretreatment values, or the control group (Table 2). It has been reported that torsemide can significantly increase the urinary excretion of sodium in dogs (Uechi and others 2003), but this differs from the results of the present study, in which no changes in urinary excretion of sodium in dogs treated for 28 days with torsemide were found. However, Patterson and others (1994) reported an increase in the urinary excretion of sodium in human beings treated with ACE inhibitors only when administered a high dose of torsemide, but not with low doses similar to the dose used in the Veterinary Record (2007) 160, 847-848