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What is the short half life of dobutamine due to?
Rapid biotransformation of the drug by tissue catechol O-methyltransferase
What is the important clinical indication of dobutamine?
Management of hypotension during anesthesia in horses
What is the principle effect of aminophylline?
What drug is useful for treatment of acute pulmonary edema, and is not indicated for the management of CHF?
What are drugs that can relax and dilate smooth muscle of arterioles, thereby reducing systemic vascular resistance, mediated by baroreceptors and the sympathetic nervous system?
A reduction in afterload does what?
- Decreases myocardial oxygen demand
- Increases CO
Peripheral vasodilation diverts the blood from pulmonary to the systemic circulation, this elicits what?
- Antagonistic response to pulmonary edema
- Restricts venous return to heart (ventricular preload)
What is a common adverse effect associated with vasodilators?
Reflex tachycardia due to vasdilation increased myocardial oxygen demand
What is a most efficient vasodilator and can be administered with dobutamine, the positive inotropic action of dobutamine could compensate the marked hypotension produced by this vasodilator?
What are peripheral vasodilators, reduce peripheral vascular resistance and improve cardiac output, due to opening of potassium channels in arteriolar smooth muscle membranes.?
Hydralazine and minoxidil
The beneficial effects of hydrlazine are mainly manifested in what?
CHF that is secondary to mitral valve insufficiency/ aortic valvular insufficiency
Why would plasma hydralazine concentrations be higher in uraemic patients?
Uremic conditions affects biotransformation of hydralazine
What is a selective a1-adrenergic, effective in dogs with CHF that are refractory to digoxin, induces vasodilation with minimal reflex tachycardia in comparison to other vasodilators?
What vasodilator has rapid onset, oral bioavailability is <1% due to its first pass mech.?
What vasodilator is a nonselective B-adrenoceptor agonist, produces vasodilation of skeletal muscle vasculature and relaxation of uterine smooth muscle?
What are the clinical indications of isoxsuprine?
- Parturition complications
- Navicular Dz
What is the function of the macula densa?
Monitor changes Na+ & Cl- in the distal renal tubule
What is the release of renin stimulated by?
- Reduced renal arterial pressure
- Activation of the B1 adrenoceptors in the JG apparatus
- Decreased Na+
What is a potent vasoconstrictor agent and is a stimulant of aldosterone secretion?
What are commonly used drugs to treat heart failure and hypotension, produce vasodilation without significantly affecting the heart?
ACE inhibitors do not activate the sympathetic system, so it can be safely used in what?
Ischaemic heart disease
ACE inhibitors act by what?
- Inhibit ezyme peptidyl dipeptidase (hydrolyzes Angio I to Angio II)
- Inhibition of bradykinin degeneration
What can be used as an alternative to digoxin in the treatment of mild CHF in dogs and cats?
Fixed dose combination preparations containing an ACE inhibitor and a thiazide diuretic enhance what?
- Antihypertensive effect (ACE inhibitor)
- Inhibit K+ loss from the body
What are the 3 main aims in the treatment of acute lest ventricular failure, which is characterized by pulmonary edema?
- Improve gas exhange
- Enhance myocardial activity
- Reduce the workload of the left ventricle
The IV dose of what drug increases venous capacitance by redistributing venous blood from lungs toward the peripheral circulation thus alleviated pulmonary congestion, this extra-renal effect is usually attained first followed by diuretic effect?
The beneficial effect of this opiod agonist is due to hypotensive effect, and decreased responsiveness of medullary respiratory center to an increased partial pressure of CO2. Relieves dyspnea and anxiety that are associated with acute left ventricular failure?
Epinephrine, a mixed adrenoceptor agonist is contraindicated in what?
- Acute left ventricular failure
- (D/T peripheral vasoconstriction and arrhythmogenic activity)
In the heart cell, the cell membrane is selectively permeable to K+ ions during what stage?
When the cardiac cell is stimulated, the cell membrane becomes permeable to K+ ions, the resulting change in ion distribution is recorded as what?
What phase of action potential represents rapid influx of Na+ ions to the cell. This is a rapid upstroke phase (depolarization)?
What phase of action potential is the rapid repolarization phase, it is a short period where the Na+ ion concentrations inside and outside the cardiac cell are equal?
What phase of action potential is the plateau phase, is important since the slow inward Ca++ current facilitates membrane excitetation and activation of contractile process?
What phase of action potential is the delayed repolarization phase, Na+ gates are closed, and K+ ions flow out of cell?
What phase of action potential is where the cardiac cell Na+/K+ pump restores the cell membrane to its resting membrane potential? phase 4
Regarding cardiac rhythm, what is known as the pacemaker?
Dominance of the SA node
What class of antiarrhythmic drugs are membrane stabilizers and local anesthetics?
What are examples of class IA antiarrhythmic drugs(3)?
What are examples of class IB antiarrhythmic drugs (5)?
What are examples of class IC antiarrhythmic drugs(3)?
What class of antiarrhythmic drugs are classified as B-adrenergic antagonists?
What class of antiarrhythmic drugs are agents that prolong the refractory period?
What class of antiarrhythmic drugs are calcium channel blockers?
Since slow Ca++ current is involved in AV nodal conduction, calcium channel blockers slows AV conduction, thus helps in controlling what (2)?
- Supraventricular arrhythmias
- Prolong refractory period
What are examples of class III antiarrhythmic drugs (2)?