Cardivascular Stimulants Flashcards
Which drugs are affected by pre-treatment with Reserpine?
Reduced (mixed acting) -ephedrine Abolished (indirect acting) -Tyramine -Amphetamine
How does the administration of Epinephrine affect diastolic pressure?
It barely affects it and may lower it due to the Beta-2 vasodilatory effect
What are the effects of IV epi?
Cardio stimulatory, increase in heart rate and force of contraction, vaso constriction
What is the effect of small dose epi
Small dose epi may decrease blood pressure
How does Epi affect the heart rate?
- Shortened systole which increases CO and O2 consumption
- Increased relaxation rate of ventricular muscle
- Accelerating SA node slow depolarization rate
- Amplitude of AP and maximal rate of depolarization (phase 0) also are increased
- Activates latent pace maker cells in SA node
- Directly shortens AV node refractory period; opposed by reflex vagal discharge
What is one of the consequences of epi administration?
Premature ventricular contractions may occur
-ventricular extrasystoles, tachcardia or even fibrillation may be precipitated
How does Ephedrine Administration affect the renal system?
- Decreases renal Blood flow
- Decreses excretion of Na+, K+, and Cl-
- Increases renin secretion (B1 receptors of JGA)
How does Ephedrine administration affect the pulmonary system?
- Increases pulmonary (arterial and venous) pressures
- Redistribution of blood from other constricted areas
- Pulmonary edema precipitated by high conc
What are the side effects of Epinephrine administration?
- Cerebral hemorrhage especially with non-specific b-blockers
- Ventricular arrhythmias
- Angina
What opposes the effects of Norepi on the heart?
Vagal stimulation
What is a complication of IV administration of Norepi?
Necrosis at infusion site
What drug will oppose the effect of Norepi?
Phentolamine
What effect does dopamine have on the kidney at low conc?
Increases renal perfusion
What are the Low dose effects of Dopamine .2-2 mcg/kg/min?
Predominantly D1 action
- Vasodilation in renal mesenteric coronary and intracerebral vasculature
- inproves GFR
What are moderate dose (2-10 mcg/kg/min) effects
D1 and B1 activity
- increase CO (contractility»»>HR) and the D1-induced vasodilation
- Moderate dose also causes the release of NE from nerve terminals which contributes to its effects in the heart
What are the effects of High dose (10 mcg/kg/min)?
Alpha agonism predominates
-increase peripheral vascular resistance and renal vasoconstriction
Where does Dobutamine have its effect?
Beta-1 agonist that increases CO and in so doing increases urinary output
What is the major use of Dobutamine
For short term treatment of cardiac decompensation
What is interesting about Dobutamine?
Ultrashort halflife
Where does Isoproterenol have its effects?
Beta receptors, it decreases diastolic blood pressure
May cause Palpitations, sinus Tachycardia; and even serious arrhythmias
Where does Isoproterenol decrease resistance?
In vasculature of skeletal muscle but also in renal and mesenteric vascular beds
How is isoproterenol given?
Parenteral or by aerosol
What is the major use of isoproterenol?
Used in emergencies to stimulate HR in patients with bradycardia or heart block particularly in anticipation of inserting an artificial cardiac pacemaker or in patients with ventricular arrhythmia torsades de pointes
What is Phenylephrine?
Direct acting alpha-adrenergic agonist with virtually no B-adrenergic activity
What are the effects of Phenylephrine administration?
Systemic Arterial vasoconstriction and reflex decrease in HR and CO
What are the indication of Phenylephrine?
Control of hypotension associated with regional or spinal anesthesia
What are the adverse effects of Phenylephrine?
Angina, anxiety, hallucinations or psychosis, hypertension, excitability dizziness insomnia pallor
What are the effects of Ephedrine?
Mixed acting smpathomimetic
- direct action on both a and b receptors
- Enhances release of NE from sympathetic neurons
What are the uses of Ephedrine?
Used for hypotension and hypotension of analgesia
What are some of the side effects of Ephedrine administration?
- Increased cardia workload leads to Angina
- s-TACH
- Fatal Arrhythmias including ventricular fibrilation
