Page 985 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

960 CHAPTER 7

VetBooks.ir or congestive heart failure, mannitol cannot move Sodium bicarbonate
Sodium bicarbonate has been successfully used in
into cells and is retained within the extracellular
fluid. Water moves out of cells into the extracellular
of urine diminishes renal retention of myoglobin.
fluid, causing hyponatraemia and tissue congestion. myoglobin-induced toxic nephropathy. Alkalisation
Volume overload may result in systemic and pulmo- This is probably achieved with better solubility
nary oedema. of myoglobin in the alkaline medium. Therefore,
Mannitol has been used for prophylaxis against horses affected by rhabdomyolysis benefit from
renal dysfunction; however, the benefit of its admin- bicarbonate administration.
istration is questionable. Mannitol is contraindicated
in patients with anuria secondary to renal disease, Other drugs
severe dehydration, pulmonary congestion and con- Cisplatin, a chemotherapy medication for vari-
gestive heart failure. Numerous studies confirmed ous solid tumours, has dose-dependent side-effects
the nephrotoxic potential of high-dose mannitol. on the kidney. Oxidative stress, DNA damage and
This has not been reported or investigated in horses. inflammation induce renal damage. In human medi-
cine one-third of patients who have undergone
Furosemide cisplatin therapy develop nephrotoxicity despite
Furosemide is a loop diuretic that blocks the neph- adequate pre-hydration. This has not yet been
ron site responsible for urinary concentration and reported in horses.
increases urinary water, sodium, potassium, calcium Proton pump inhibitors are widely used in equine
and magnesium excretion. Loop diuretics may cause medicine. In humans they have been linked to acute
electrolyte disturbances such as hypokalaemia, hypo- interstitial nephritis and CKD. Renal toxicity may
calcaemia, hypomagnesaemia, metabolic alkalosis be through a cell-mediated idiosyncratic immune
and volume contraction. Furosemide can be useful response with diffuse interstitial leucocyte infil-
in patients with renal insufficiency. However, fac- trate (interstitial nephritis). Impaired renal func-
tors that limit proximal tubule secretory activity (e.g. tion was also reported in horses based on serum
decreased renal blood flow or renal failure) reduce urea and creatinine levels. Proton pump inhibitors
the effectiveness of furosemide and other diuretics. (omeprazole) should therefore be used with cau-
NSAIDs diminish the response to loop and thia- tion in horses with pre-existing kidney disease.
zide diuretics because they increase electrolyte and Regular urine and blood analyses should be carried
water resorption at the thick ascending limb of the out in horses treated chronically with proton pump
loop of Henle. Concomitant use of furosemide and inhibitors.
aminoglycosides may produce severe ototoxicity, Ammonium chloride (60–520 mg/kg p/o q24 h),
especially in young animals. ammonium sulphate (175 mg/kg p/o q24 h), and
Furosemide should be used cautiously in sep- ascorbic acid (1–2 g/kg p/o q24 h) are used for urine
tic patients, because it can trigger a pronounced acidification. Horses do not find ammonium salts
decrease in medullary blood flow and consequent palatable and will rarely voluntarily ingest the vol-
medullar ischaemia. These alterations in blood flow ume required to acidify urine.
were not evident in non-septic cases. Phenoxybenzamine (0.7 mg/kg p/o q6 h), an
alpha-adrenergic blocker, can be used to diminish
Dopamine urethral resistance in UMN bladder dysfunction.
The use of dopamine may improve renal blood flow Bethanecol chloride (0.025–0.075 mg/kg s/c q8 h)
in horses with AKI. Dopamine dilates renal arte- exerts stimulatory effects on the smooth muscle of
rioles and increases renal blood flow and the GFR. the bladder. It is a drug of choice in cases of detrusor
Cardiac dysrhythmias are the most common adverse atony. Side-effects include abdominal discomfort,
effects recognised in horses. excessive salivation and lacrimation.