Management of canine CHF (Yr 3) Flashcards
what are the four main consequences of heart failures?
vasoconstriction
tachycardia
myocardial remodelling/fibrosis
oedema/effusions
what is the immediate life threatening issue associated with left sided CHF?
pulmonary oedema
what is the main immediate problem associated with CHF?
sodium and water retention
what effects does the sodium/water retention in right sided CHF?
ascites, hepatomegaly, pleural effusion
what is the first choice treatment for oedema and effusions?
diuretics (furosemide)
what is the first choice diuretic?
furosemide
how much furosemide should be given in chronic cases?
lowest dose possible to control the clinical signs
how do you titrate furosemide to effect?
owner monitors the sleeping/resting respiratory rate and then can reduce dose if there is no increase in respiratory rate (very sensitive way of monitoring how controlled CHF is)
what are the main two side effects of furosemide?
pre-renal azotaemia
hypokalaemia
(must monitor renal function)
what needs to be monitored when a patient is on diuretics such as furosemide?
renal function (urea, creatinine, electrolytes)
should furosemide be used on its own?
should be used as monotherpay long term as it activates RAAS (leading to more remodelling/fibrosis)
what should be done if furosemide is no longer working and you have reached the maximum dose?
ensure optimised use of ACE inhibitors
consider parenteral administration (GIT oedema in right sided CHF can inhibit absorption)
resistance can develop so consider other diuretics (sequential nephron blockade)
consider swapping for another loop diuretic (torasemide)
what diuretics can be added to furosemide for sequential nephron blockade?
spironolactone
amiloride/hydrochlorothiazide
(need to monitor renal function)
what type of drug is spironolactone?
aldosterone antagonist
potassium sparing diuretic
is thoracocentesis indicated with pleural effusions caused by CHF?
yes (don’t wait until diuretics take effect!!)
how do ACE inhibitors work?
counteract adverse effects of angiotensin II
what do ACE inhibitors do?
vasodilators
reduced aldosterone release (reduced sodium/water retention)
prevent angiotensin 2 mediated myocardial fibrosis/remodelling
anti-adrenergic effects
vasopressin release
endothelin release
increased bradykinin and vasodilatory prostaglandins
prevent glomerular capillary hypertension
what are some ACE inhibitors available?
enalapril
benazepril
ramipril
imidapril
when should ACE inhibitors be avoided?
if the animal is severely hypotensive as they may compromise renal function
what are the potential side effects of ACE inhibitors?
hypotension
renal impairment
hyperkalaemia
anorexia, diarrhoea, vomiting…
what needs to be monitored when a patient is on ACE inhibitors?
blood pressure
renal function and electrolytes
what angiotensin 2 receptor blocker is licensed?
telmisartan (in cats but not licensed for CHF)
when would venodilators be used for CHF?
rapid control of pulmonary oedema
what venodilators can be used for rapid control of pulmonary oedema?
IV furosemide
topical nitroglycerine ointment (apply to hairless well perfused area)
what is the use of arteriodilators in CHF cases?
reduced myocardial workload by reducing systemic blood pressure and hence afterload (reduces myocardial oxygen consumption)
what are some arteriodilator drugs?
pimobendan (balanced vasodilator)
amlodipine
hydralazine
ACE inhibitors
what is the mode of action of pimobendan?
positive inotrope (calcium sensitiser and phosphodiesterase inhibitor)
vasodilator (phosphodiesterase inhibitor)
how is pimobendan administered?
orally (inhibited by food so should be given on an empty stomach)
how can we counteract the high sympathetic drive in CHF?
mainly use drugs to improve haemodynamic status to indirectly reduce sympathetic drive
should beta blockers be used in CHF?
no never use them in uncontrolled CHF especially if there is poor contractility
what is a good treatment for high sympathetic drive in CHF cases?
digoxin (enhance vagal tone, reduce sympathetic drive)
what are the main functions of digoxin?
negative chronotrope
weak positive inotrope
favourable autonomic effects
when is digoxin use indicated?
atrial fibrillation - main indication
supraventricular tachyarrhythmias
if impaired systolic function
(vagomimetic)
what effects dose digoxin have as it is a vagomimetic?
stimulates vagal centres in CNS, sensitises baroreceptors to BP changes, enhance pacemaker response to acetylcholine
all of these result in slowed rate of discharge through SAN, slowed conduction through AVN and increased refractory period in AVN
what are some signs of digoxin toxicity?
excessive borborygmi
depression
anorexia
vomiting/diarrhoea
cardiac arrhythmias
what patients are more predisposed to digoxin toxicity?
thin, obese, ascites, hypoproteinaemia, hypothyroidism, impaired renal function, dobermans, hypoxia, hypokalaemia
what is the standard treatment therapy of CHF in dogs (for either MVD or DCM)?
furosemide
pimobendan
ACE inhibitor (benazepril)
spironolactone
can you start treatment for preclinical myxomatous mitral valve disease or DCM?
yes - at risk animals can be given pimobendan (can prolong their life before they go into CHF)
what drug can be used to delay the onset of CHF in potential DCM and MMVD?
pimobendan
