How does that differ in cats?
Pressler: Cats with acute renal failure do not differ from dogs in their need for aggressive fluid support, although mild fluid overload
is much more likely to result in heart failure and pulmonary edema than in dogs. This may be because cats are more likely
to have occult heart disease than dogs.
Do you have specific recommendations for handling the secondary GI signs seen with renal failure (e.g., inappetence, GI ulceration)?
Pressler: When a patient with intrinsic renal disease is displaying signs referable to the GI tract — in other words, vomiting — I
always treat for presumptive GI ulceration. Oral H2-blockers such as famotidine are available without a prescription, are well-tolerated and are not costly. If this class of
drugs fails to resolve the observed clinical signs, then I usually re-examine the patient for other possible causes before
attempting another drug. If further gastroprotection is required, I typically opt for a proton-pump inhibitor such as omeprazole
and reserve sucralfate for patients with obvious GI bleeding as exhibited by hematemesis or melena.
Is mirtazapine useful in this area?
Pressler: Inappetence secondary to nausea in uremic patients is presumptively due to both stimulation of the medullary chemoreceptor
trigger zone by uremic toxins and peripheral GI ulceration and enteritis. The precise mechanism whereby mirtazapine prevents
nausea is unknown. One effect in people appears to be inhibition of 5-HT3 serotonin receptors within the chemoreceptor trigger zone, so I do believe that mirtazapine could, in theory, be beneficial
for treating renal failure-associated nausea. That being said, I have had mixed success in dogs with chronic kidney disease
but still believe a trial course is appropriate if other treatments have been unsuccessful. I do worry, however, about the
lack of studies on this drug in dogs and cats, as we know very little about possible side effects or drug interactions. For
example, mirtazapine is eliminated primarily in the urine in people, and dose reductions are recommended in patients with
Would you describe how you address hypertension in patients with acute renal failure? Does the presence of hypertension change
your treatment progression?
Pressler: To begin with, it needs to be emphasized that hypertension is a common consequence of renal failure, so measurement of blood
pressure should be a routine part of the initial evaluation and all recheck examinations in patients with kidney disease.
Persistent hypertension is associated with shortened time until uremic crisis and reduced survival in patients with chronic
kidney disease. Treatment is thus recommended with the hope that normalization of blood pressure will delay progressive nephron
In dogs, angiotensin-converting enzyme (ACE) inhibitors lower blood pressure, reduce proteinuria and may provide additional
anti-inflammatory and antifibrotic benefits. If hypertension persists despite a maximal dose of ACE inhibitors, then I add
amlodipine. I always start this second drug at the lowest recommended dose because there is a synergistic effect, and hypotension
In cats, amlodipine is highly effective in treating hypertension in patients with kidney disease. ACE inhibitors are rarely
effective at lowering blood pressure in cats, proteinuria is much less common and there is less evidence for dysregulation
of the renin-angiotensin-aldosterone system that would presumptively benefit from ACE inhibitors.
Does the use of telmisartin seem promising for treating hypertension?
Pressler: Angiotensin II receptor antagonists such as telmisartin or losartan are commonly used antihypertensives in people. These
drugs directly inhibit the action of angiotensin II, a potent vasoconstrictor, and may provide superior blockade of the renin-angiotensin-aldosterone
system than ACE inhibitors do. These drugs also prevent the phenomenon of aldosterone escape seen with chronic ACE inhibitor
therapy, which refers to the increases in aldosterone to pretreatment concentrations. Unfortunately, these drugs are relatively
costly, doses in veterinary patients have not been established, and it is unknown how or if these drugs alter prognosis in
dogs with glomerular or chronic kidney disease. I believe these drugs will eventually become a routine part of our antiproteinuria
therapy, but I am wary of using them as first-line anti-hypertensives until further efficacy and safety studies are performed.