Page 226 - Clinical Small Animal Internal Medicine

194 Section 3 Cardiovascular Disease

Echocardiography can help confirm the diagnosis. congestion, such as pulmonary edema, pleural effusion,
VetBooks.ir Phosphodiesterase V inhibitors, such as sildenafil or ascites, and improvement of forward cardiac output
and tissue perfusion. In general, more attention is given
(1–3 mg/kg PO TID) or tadalafil (1 mg/kg PO SID) are
variably effective. In the authors’ experience, sildenafil
neurohormonal systems, such as the RAAS or sympa-
seems to be more effective than tadalafil. Both drugs can to stabilization of hemodynamics versus interruption of
be very expensive, especially in large‐breed dogs. Both thetic nervous systems that are so critical to treatment of
agents are well tolerated in dogs. Rarely, inguinal flushing chronic heart failure.
and gastrointestinal upset are noted. Systemic hypoten-
sion is rare. Monitoring of the clinical symptoms as well Diuretics
as pulmonary and systemic pressures is recommended.
Diuretics are a mainstay of treatment of acute CHF.
Treatment induces potent and rapid diuresis. Parameters
Positive Inotropes
commonly monitored during diuresis include respira-
In cases of refractory heart failure due to DCM or tory rate and effort, body weight, urine production, elec-
MMVD, off‐label dosages of pimobendan are often uti- trolytes, renal function, and blood pressure. Furosemide
lized. The authors will increase frequency of dosing from is the most commonly used diuretic for the treatment of
0.25 mg/kg BID to TID followed by a slow titration to acute CHF. When given by IV, IM, or SC routes, diuresis
0.5 mg/kg TID as needed. Additional pimobendan can begins within 5–10 minutes and reaches a peak at 30–60
also be effective in cases of biventricular heart failure as minutes with duration of action between two and three
well as in patients with PHT. Cats with DCM or other hours. A typical initial dose is 2–4 mg/kg IV/IM/SC in
forms of systolic dysfunction also appear to tolerate dogs and 1–2 mg/kg IV/IM/SC in cats. Because of its
doses of pimobendan greater than 0.25 mg/kg BID. On relatively short duration of action, repeated bolus injec-
rare occasions, three days of dobutamine infusion in the tions of furosemide are needed if respiratory rate and
hospital at 2.5–10 μg/kg/min can be considered as there other clinical signs are not improved within 2–4 hours
might be some residual positive inotropic benefit for after initial dose. During administration, patients should
some time after the hospitalization. Oral digoxin can be produce large quantities of dilute urine, and failure to
added to the existing treatment regimen, especially if induce diuresis should alert clinicians to the possibility
tachyarrhythmias such as atrial fibrillation are present. of underlying renal dysfunction, poor forward cardiac
Care should be taken to monitor serum digoxin levels to output, and/or reduced renal perfusion. In patients with
avoid toxicity. left‐sided CHF such as pulmonary edema, the simplest
way to monitor response to diuretics is to monitor
Cough Suppression respiratory rate and effort. Most patients with severe
pulmonary edema will exhibit respiratory rates at pres-
Many canine patients with chronic heart failure develop a entation >45 breaths/min with increased abdominal
cough secondary to bronchial compression as a result of effort and orthopnea. As diuretics resolve pulmonary
bronchomalacia and severe atrial dilation. In the absence edema, the respiratory rate and effort should begin to
of CHF, a variable amount of cough suppression is decrease, signaling an ability to reduce frequency of diu-
achieved with hydrocodone (0.22–0.44 mg/kg PO B‐QID) retic injections to q6–8h. Continued improvement in
or butorphanol (0.55 mg/kg PO B‐QID). Bronchodilators, respiratory rate and effort over the subsequent 12–24
such as aminophylline or theophylline, are typically hours leads to replacement of parenteral furosemide
ineffective. with oral furosemide.
Diuretic therapy for treatment of acute CHF should be
personalized for individual patients depending on the
Therapy of Acute Life‐Threatening severity of clinical signs, current or previous therapy
Heart Failure with oral diuretics, co‐administration of other heart fail-
ure medications, hydration status, renal function, and
Therapy for acute‐life threatening heart failure is based blood pressure. In general, patients with extreme respir-
on many of the same principles that guide therapy for atory distress or those already receiving oral diuretics
chronic heart failure, namely diuresis to alleviate conges- will require higher initial starting doses and more fre-
tion, vasodilators to reduce preload and afterload, and quent repeated boluses, while those with preexisting
positive inotropes to improve myocardial contractility renal dysfunction, dehydration, or low blood pressure
(Table 19.2). In acute heart failure, hemodynamic abnor- will require more conservative dosing. Renal and elec-
malities such as congestion and low cardiac output pre- trolyte bloodwork as well as blood pressure measure-
dominate and therapy is targeted towards resolution of ment are typically performed as soon as practicable after