Page 157 - Small Animal Internal Medicine, 6th Edition

CHAPTER 6 Acquired Valvular and Endocardial Disease 129

making the diagnosis is unclear. The presence of pulmonary may help support respiratory muscle function. Bronchodila-
lobar venous distension suggests that CHF is imminent, tors can potentially increase the risk for tachyarrhythmias,
VetBooks.ir however this is not always seen. When it is unclear if respira- though. In dogs with moderate- to large-volume pleural effu-
sion, thoracocentesis should be done as expeditiously as pos-
tory signs are caused by heart failure or a noncardiac cause,
an initial furosemide trial (e.g., 1-2 mg/kg PO q8-12h) for 2
to impede respiration also should be drained. Close moni-
to 3 days can be helpful. Plasma NT-proBNP measurement sible to improve pulmonary function; ascites severe enough
also can be useful. Some clinicians add an ACEI during the toring for the patient’s response to therapy and any adverse
therapeutic trial for suspected CHF. Cardiogenic pulmonary effects (e.g., hypotension, azotemia, electrolyte abnormali-
edema usually responds rapidly, so if CHF was the cause, the ties, arrhythmias, drug toxicity, and so on) is important for
owner should see rapid improvement in RR and effort as well optimizing care (see Chapter 3, p. 65 for additional informa-
as reduced (cardiogenic) cough. In these cases, triple therapy tion). Mild to moderate azotemia is common after aggressive
is instituted along with recommendation for moderate diuretic therapy. Slow oral “self-rehydration” is effective for
dietary salt restriction. Depending on the individual case, it most patients. Because it can exacerbate congestive signs,
may be possible to reduce the dose of furosemide somewhat, parenteral fluid therapy is avoided whenever possible (see
using RRR monitoring as a guide. On the other hand, cough- Chapter 3, p. 65, section of monitoring and follow-up after
ing or other respiratory signs that persist despite furosemide acute CHF treatment).
trial makes a diagnosis of CHF unlikely. Nevertheless, confu-
sion is still possible in some cases because a cough from TRANSITION TO HOME CARE
airway irritation may resolve spontaneously, or furosemide After the patient is stabilized, medications are adjusted over
may have a mild antiinflammatory or antitussive effect. the next several days to weeks to determine the best regimen
for long-term treatment. Furosemide is titrated to the lowest
MODERATE TO SEVERE SIGNS OF CHF dose and longest interval that controls signs of congestion.
Fulminant pulmonary edema with shortness of breath at rest RRR monitoring over time helps guide this (see p. 74). An
is a true emergency. Aggressive therapy, but with gentle han- ACEI is recommended for chronic therapy if another vaso-
dling, is crucial in these fragile patients. Cage rest, supple- dilator was used initially. The ACEI can be dosed once daily
mental oxygen, high-dose (e.g., 2-4 mg/kg q1-4h initially) to start as the patient is weaned off the other (arteriolar)
parenteral furosemide, and vasodilator therapy are indicated vasodilator over a couple days. The ACEI can be increased
(see Box 3.1, p. 62). Intravenous (IV) nitroprusside or to q12h dosing over the next several days to a week. Client
hydralazine (PO or IV) can be used for acute therapy for education about the purpose and potential adverse effects
rapid arteriolar vasodilating effect. BP must be closely moni- of prescribed medications, RRR monitoring, diet, activity
tored. A low dose is used in animals already receiving an restrictions, follow-up schedule, and other recommenda-
ACEI. Amlodipine is another alternative, although onset of tions is important.
action is slower. Amlodipine can significantly decrease LA
pressure and MR regurgitant jet severity compared to ACEI, MONITORING HEART FAILURE THERAPY
however up to four days are needed for full effect. Topical Continued monitoring is important, especially for renal
nitroglycerin can be used in combination with an arteriolar function, serum electrolyte concentrations, BP, and recur-
dilator in an attempt to reduce pulmonary venous pressure rent congestive signs. Intermittent arrhythmias can trigger
by direct venodilation. Pimobendan dosing is begun (or con- decompensated congestive failure, as well as episodes of
tinued) as soon as possible. transient weakness or syncope. Cough-induced syncope,
Heart rate and rhythm should be monitored. For the atrial rupture, or other causes of reduced cardiac output also
control of supraventricular tachyarrhythmias, diltiazem or a can occur. Despite periodic recurrence of CHF signs, with
β-blocker (see Table 4.2, p. 90) can be used instead of or in proper management many dogs with CMVD enjoy a good
addition to digoxin. Although several days are needed to quality of life for several months to years after signs of failure
achieve therapeutic digoxin serum concentration with oral first appear. Dogs with recently diagnosed or decompensated
maintenance doses, IV digoxin is not recommended. Therapy CHF should be rechecked more frequently (every few days
for ventricular tachyarrhythmias is warranted in occasional to every week or so) until their condition is stable; those with
cases. For dogs with CMVD that require BP support or when chronic heart failure that is well controlled can be reevalu-
myocardial function is poor, other more potent inotropic ated less often but usually at least three to four times per year.
agents (e.g., dobutamine or dopamine) can be given IV (see
Box 3.1, p. 62).
Mild sedation is used to reduce anxiety (e.g., butorphanol; COMMON COMPLICATIONS
see Box 3.1, p. 62). Patient handling should be minimized,
and radiographs and other diagnostic procedures postponed END-STAGE/REFRACTORY (STAGE D)
until the respiratory status is more stable. A bronchodilator HEART FAILURE
(e.g., theophylline, aminophylline) sometimes is used when Recurrent acute CHF should be treated in-hospital as
bronchospasm induced by severe pulmonary edema is sus- described previously (see Box 3.1, p. 62). Pleural and abdom-
pected; although the efficacy of this is unclear, these agents inal effusions are drained as needed to maintain patient