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19 Management of Heart Failure 197

Nitroprusside is a potent mixed vasodilator capable of to rapidly acting short‐term effects in acute CHF. The
VetBooks.ir both venous and arterial vasodilation. It acts by releasing rate‐limiting factors affecting ACEI use include azotemia
and systemic arterial hypotension. The authors occa-
nitric oxide, which induces vascular smooth muscle
relaxation. Nitroprusside is metabolized very rapidly and
lized with diuretics, positive inotropes, and other
is administered via CRI (1–10 μg/kg/min in dogs). Its sionally delay initiation of ACEI until acute CHF is stabi-
rate‐limiting factor is systemic arterial hypotension, and vasodilators, and are especially cautious in patients
blood pressure monitoring is highly recommended dur- already suffering from systemic hypotension or in those
ing use. Typically, the dosage is adjusted to achieve a sys- that required very high doses of diuretics to alleviate
tolic arterial blood pressure no lower than 90 mmHg. congestion and are significantly dehydrated. In these
The short half‐life of nitroprusside allows clinicians to cases, ACEI administration might be delayed until the
effectively make changes in infusion rates in response to patient’s hydration status and renal bloodwork are
blood pressure. Nitroprusside, while highly effective, is reevaluated. They are then prescribed as part of the
only occasionally used due to its need for CRI and sensi- chronic CHF therapy with close monitoring of renal
tivity to light that requires the administration set to be bloodwork and systemic blood pressure.
covered in light‐protective wrapping. Similar to dopa-
mine or dobutamine, nitroprusside infusions are given Additional Therapies for Acute CHF
short term, typically not longer than 48 hours. At very
high doses or for extended periods of administration, Oxygen supplementation is provided in cases of res-
accumulation of nitroprusside metabolites such as piratory compromise and hypoxemia. Inspired O 2 con-
cyanogen can result in toxicity. Nitroprusside is rarely centration is typically increased to 40% through the use
used in cats. At the time of writing, supply shortages of of oxygen cages or, in the case of large dogs, nasal insuf-
nitroprusside have severely curtailed its use and alterna- flation. Manual removal of pleural, pericardial, or
tive nitric oxide donors such as IV nitroglycerin (1–10 μg/ abdominal fluid should be performed if these effusions
kg/min) have been used. are a cause of respiratory compromise. In patients that
are extremely anxious, mild sedation with morphine
(0.1–1.0 mg/kg SC/IM in dogs), acepromazine (0.1–
ACE Inhibitors
0.2 mg/kg SC/IM in dogs) or butorphanol (0.1–0.3 mg/
ACE inhibitors form a cornerstone of therapy of chronic kg IM/IV in dogs or cats) can be considered. Care must
CHF. Their utility in acute life‐threatening CHF is less be taken to avoid oversedation as further compromise
evident. Compared to hydralazine or nitroprusside, the of respiratory function can result. Bronchodilators
arterial dilating effects of ACEI are modest. ACEI’s abil- such as aminophylline or theophylline or cough sup-
ity to decrease AT II and aldosterone production appears pressants such as hydrocodone are rarely needed in
more beneficial over longer periods of time as opposed cases of acute CHF.

Further Reading

Atkins C, Bonagura J, Ettinger S, et al. Guidelines for the Haggstrom J, Boswood A, O’Grady M, et al. Effect of
diagnosis and treatment of canine chronic valvular heart pimobendan or benazepril hydrochloride on survival
disease. J Vet Intern Med 2009; 23: 1142–50. times in dogs with congestive heart failure caused by
Boswood A, Haggstrom J, Gordon SG, et al. Effect of naturally occurring myxomatous mitral valve disease:
pimobendan in dogs with preclinical myxomatous mitral the QUEST study. J Vet Intern Med 2008; 22: 1124–35.
valve disease and cardiomegaly: the EPIC study – a Luis Fuentes V. Treatment of congestive heart failure. In:
randomized clinical trial. J Vet Intern Med 2016; 30: Luis Fuentes V, Johnson LR, Dennis S, eds. BSAVA
1765–79. Manual of Canine and Feline Cardiorespiratory
Ferasin L, Defrancesco T. Management of acute heart Medicine. Gloucester, UK: British Small Animal
failure in cats. J Vet Cardiol 2015; 17(Suppl 1): S173–89. Veterinary Association, 2010, pp. 153–9.