Therapeutics - approach to treatment Flashcards
Why administer drugs?
Cure underlying disease Prevent or slow progression of disease Increase life expectancy Improve quality if not length of life
Outline steps to appropriate management - 4
Correct ID of underlying disease Stage severity Apply EBVM In absence of ‘best evidence’, make an informed and rational decision
Define EBVM
the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients
What is the best evidence?
Well-designed, blinded, prospective studies. The next-best evidence comes from lower quality sources such as case-control studies, retrospective uncontrolled studies, case series, individual case reports and expert opinion.
What is the best evidenced tx for MVD (dogs)?
Pimobendan ACEI Spironolactone
Best evidenced Tx for DCM
Pimobendan and ACEI
Best evidenced Tx for feline HCM
ACEI
How can CSs of cardiac disease be divided up in terms of thinking about therapy?
Is the patient showing congestive signs (wet) or outpt signs (i.e. ‘cold’) or both?
Define lusitropy
the ability of the heart to relax
What are the different signs that could underlie the the signs present in a patient?
Increased preload Increased afterload Impaired inotropy Impaired lusitropy Abnormalities of cardiac rate and rhythm
Main sign of excessive preload
Congestion - detectable on PE or radiographs. Oedema, ascites, peripheral oedema, pleural oedema, pleural effusion and venous congestion
Tx - preload reduction
DIURETICS AND VENODILATORS
Providing the underlying disease is readily rectifiable, diuresis with or without venodilation will be required.
When to treat for afterload reduction? How?
Patients are likely to appear pale or cold. Treatment for this will help when the patient has mitral regurgitation. HOW: arteriodilators (if no fixed obstruction)
When might you want to improve systolic function?
DCM and later stages of MVD. Use inotropic agents may improve output and signs.
When might diastolic function need to be improved? What drugs should be used?
when the heart muscle is excessively hypertrophied or where there is excessive fibrosis. DRUGS TO USE: hasten relaxation (calcium channel blockers), slow HR (beta-blockers) or reduce fibrosis (ACEI).
How can you optimise heart rate and rhythm?
Changing SV and HR and therefore CO.
List classes of diuretic
- DIURETICS - Frusemide and Torasemide - THIAZIDES - chlorothiazide, hydrochlorothiazide - POTASSIUM SPARING DIURETICS: spironolactone, amiloride
How can diuretics be used initially and when they become refractory to this?
- USUALLY START DIURESIS WITH A SINGLE AGENT: fursemide at 1-2mg/kg orally 2-3 times, administer at higher doses and IV where animal is in more severe HF. WHEN PATIENT BECOMES REFRACTORY TO FRUSEMIDE: can increase dose, increase freqency, introduce second diuretic - sequential blockade (spironolactone), swap to torasemide
Risks of diuresis
Hypovolaemia Hypotension Electrolyte disturbances Stimulation of RAAS
Outline venodilation
VENODILATORS - glyceryl trinitrate - percutaneously administered ointment or cutaneous patches BALANCED VASODILATORS - act on arteries and veins - ACEI, pimobendan and nitroprusside
Define afterload
the peak ventricular wall tension during systole
What are the benefits of afterload reduction?
Increased SV Increased CO Decreased MR Reduced systolic wall tension reduces cardiac work - decreased myocardial oxygen demand, improved oxygenation of the myocardium
Risks of afterload reduction
Hypotension Reduction in SVR may result Decreased BP may compromise perfusion of essential vascular beds
List agents for afterload reduction
BALANCED VASODILATORS: ACEI, pimobendan, others (calcium channel blockers - amlodipine, xanthnes, alpha-blocers), ARTERIODILATORS - hydralazine
