Page 163 - Feline Cardiology

162 Section D: Cardiomyopathies

functional azotemia is usually temporary and resolves dioxide) to exit, and use of high oxygen flow rates and
after discontinuation of the ACE inhibitor along with cooling measures with cool packs. Placement of Saran
supportive care (see Chapter 19). Wrap over the front of an e-collar also may serve to
administer oxygen to a cat that won’t allow placement
Treatment of Acute Congestive Heart Failure of a face mask.
in Cats with HCM (Inpatients) Furosemide is rapidly life-saving in a dyspneic cat
In cats with severe dyspnea, aggressive diuretic therapy with pulmonary edema and can be given parenterally at
with high furosemide doses repeatedly is needed for doses ranging from 2–4 mg/kg every 1–8 hours depend-
immediate stabilization. These cases are best suited for ing on the severity of heart failure. The intravenous
referral to a cardiologist, criticalist, or 24-hour care facil- route is preferable over other routes because it achieves
Cardiomyopathies workup is aimed at establishing whether the dyspnea is possible in the severely dyspneic cat that will not tolerate
a rapid onset of action in 5 minutes, but it may not be
ity. However, the cat needs to be stabilized first. Initial
from heart failure or other causes. An in-depth diagnosis
restraint. Intramuscular (IM) furosemide injection has
of the specific cardiac disease is not necessary in the
a relatively fast onset of action of 30 minutes, although
skeletal perfusion may be dramatically reduced in ful-
emergency setting, and often patients are referred to a
cardiologist or specialist adept at performing echocar-
efficacy. If there is no improvement in the dyspnea after
diograms later once stabilized. The first step of triage is minant congestive heart failure, which would limit the
to determine whether there is significant pleural effu- 1 hour of intravenous injection or 2 hours of IM injec-
sion that can be rapidly removed to immediately stabi- tion of furosemide, another dose (3–4 mg/kg) should be
lize the cat. With minimal manipulation and the cat in given. Ideally an intravenous catheter is carefully placed
sternal recumbency, a thoracic ultrasound can be quickly if the cat can withstand the procedure. Water should be
done to scan for significant pleural effusion, and the left always available or offered every hour, since withholding
atrial size can also be assessed for significant dilation. water will exacerbate profound dehydration during the
Thoracocentesis can be done with the cat in sternal aggressive diuretic stage of treatment. Once the respira-
recumbency, please refer to chronic heart failure section tory rate decreases to 50 breaths/minute or less and the
and Chapter 3. If there is no significant pleural effusion effort improves, the dose and frequency of administra-
and depending on the stability of the patient, a thoracic tion of furosemide can be promptly decreased to minimize
radiograph can be quickly obtained without over- overzealous diuretic therapy and severe dehydration.
restraining and manipulating the cat (i.e., no aggressive Transdermal nitroglycerin is a venodilator that effec-
positioning techniques or placing weights that could tively reduces pulmonary capillary wedge pressure and
interfere with the cat’s ability to breathe) to assess for pulmonary edema accumulation in people with heart
significant pulmonary edema and cardiomegaly. For failure. Although no studies have evaluated the effect of
example, a dorsoventral radiograph (cat in sternal nitroglycerin in cats, it appears safe and well tolerated.
recumbency) is optimal for identifying pleural effusion One-eighth to one-quarter inch (2–5 mm) of 2% nitro-
in the least distressing manner with the least manipula- glycerin paste may be applied to the inside of the pinna
tion and restraint when ultrasound is unavailable. Initial every 4–6 hours for 1–2 days in cats. Nitrate tolerance
workup of a dyspneic cat should be cautiously done as develops rapidly within 2 days, so its use is during the first
they are extremely fragile. If the cat is too unstable for a 2 days of hospital treatment, and it should not be dis-
radiograph, oxygen administration and a parenteral pensed for chronic home therapy. An alternative protocol
dose of furosemide (3–4 mg/kg) can be given. is administration of the paste as described on the pinna,
Emergency oxygen support using 60–70% FiO 2 may removal of the paste 12 hours later, and repeat the 12
be necessary and the need is determined based on sever- hours on/12 hours off cycle for 3 days. The main draw-
ity of dyspnea. The optimal method of oxygen support back of transdermal nitroglycerin is the lack of efficacy,
is with a specialized oxygen cage that controls inspired rather than adverse effects, although precautions are
oxygen concentration, carbon dioxide, temperature, and needed for people handling the cat to minimize their own
humidity. If one is not available, an incubator tank can transdermal absorption (i.e., gloves should be worn).
be used with ice packs to cool the environment and high In cats that are not responding to aggressive diuretic
oxygen flow rates to help flush out excess carbon dioxide. treatments, nitroprusside may be a last-ditch attempt to
An oxygen mask may give temporary assistance, but also reduce pulmonary venous pressures and left ventricular
may further stress the cat and exacerbate dyspnea. A filling pressures. Nitroprusside is a rapidly acting mixed
makeshift option for oxygen administration in a crisis vasodilator (arteriolar and venous), so careful and fre-
without an oxygen cage is to wrap the cage door with quent monitoring of the blood pressure with a Doppler
cellophane wrap, allowing a space for air (carbon blood pressure machine is needed. Initial dose of