Catecholamines Flashcards
Epinephrine
1) Indications
2) Onset, DOA, Half life, VD
3) Metabolism
1) “Bronchospasm, anaphylactic shock/hypersensitivity reaction, cardiac resuscitation, hemostasis, glaucoma, nasal congestions.
Added to LA to decrease systemic absorption and to use as a cardiac marker for intra-arterial injection.”
2) “Onset 1-2 mins IV
DOA 5-10 mins
E 1/2t = 30 secs
Small Vd = poor lipid solubility”
3) Catechol-o-methyltransferase (COMT) and monoamine oxidase enzymes biotransform Epi in blood, liver and kidneys. Metabolites excreted in the urine
Epinephrine. Class and Mechanism of action.
“Endogenous Catecholamine Nonselective adrenergic receptor agonist, A1, a2, b1, b2 “
“Binding of epinephrine to adrenergic receptors, stimulating G-coupled proteins, adenylate cyclase, and cAMP. cAMP at beta1 receptors stimulates influx of Ca+ = increased intensity of actin and myosin and therefore myocardial contractility.
Low doses = stimulation of beta2 = decreased SVR and redistribution of blood to skeletal muscles.
Higher doses = stimulation of alpha1 = peripheral, renal, splanchnic vasoconstriction. And decrease in bronchial secretions.
Beta 2 stimulation = bronchodilation, vasodilation, stabilization of mast cells and decreased histamine release”
Epinephrine: Adverse effects?
Tachycardia and severe HTN
Life threatening arrhythmias – vfib, palpitations
Cerebral hemorrhage, Headache, nervousness, tremor
Hyperglycemia - beta 2 stim prevents release of insulin
Hypokalemia
Mydriasis, Increased IOP
Periph vascular insufficiency (intense vasoconstriction)”
Epinephrine: Contraindications?
Shock (other than anaphylaxis) Cardiac arrhythmias Severe hypertension, Pheochromocytoma Active labor Cerebral artherosclerosis or CAD Glaucoma Renal insufficiency"
Epinephrine: Dosage?
“2-8mcg IV for hypotension
10mcg/kg for resuscitation
Continuous infusion (1-20mcg/min)
1-2mcg/min beta2, 4-5mcg/min beta 1, 10-20mcg/min A1,beta
Nebulizer 8-15drops into nebulizer 1-3 inhalations 4-6x/day”
NorEpinephrine
1) Class
2) Action
1) “Endogenous Catecholamine
Direct acting nonselective adrenergic agonist
Alpha and B1»»>B2”
2) “Binds to alpha and beta1 adrenergic receptors, stimulating C-coupled proteins, adenylate cyclase, and camp. cAMP at beta1 receptors stimulates influx of Ca+ = increased intensity of acting and myosin and therefore myocardial contractility.
Low doses = increased CO (inotrophy and chronotrophy) and increased blood pressure.
High doses = potent alpha1 effects outweighs beta = arterial constriction = decreased vital organ blood flow. Increased diastolic pressure may help perfuse coronaries.”
NorEpinephrine
1) Indications
2) Onset, DOA, and Half life
3) Metabolism
1) “Hypotension with adequate CO
Hypotensive emergencies
Used during separation from Cardiopulmonary bypass.”
2) “Rapid onset
Limited DOA
E1/2t = 2.5 mins”
3) “Catechol-omethyltransferase (COMT)and monamine oxidase in blood liver, and kidneys. Metabolites are excreted in the kidneys”
NorEpinephrine: Adverse Effects.
Usually a result of intense vasoconstriction
HTN
Severe bradycardia – baroreceptor reflex – despite beta stim.
End organ ischemia
Hemorrhagic stroke or ischemia of cerebral vessels
Anxiety and Headache
Renal vasoconstriction = oliguria”
NorEpinephrine
1) Contraindications
2) Dosage
1) HTN, Extreme hypovolemia, Mesenteric or PVD.
2) “4mg/250mL (16mcg/mL) = standard concentration
0. 01-0.1mcg/kg/min or 4-16mcg/min IV”
Dobutamine:
1) Class
2) Action
1) “Synthetic Catecholamine – derived from beta-phenylethyamine (analog of isoproterenol)
Direct acting selective beta1 adrenergic receptor agonist.
Some beta 2 activity at clinical doses.”
2) Dobutamine binds with beta1 adrenergic receptors, stimulating G-coupled proteins, adenylate cyclase, and cAMP within the cell causing influx of Ca+ and promoting cardiac muscle contractility. Beta2 stimulation causes peripheral arterial vasodilation and decreased afterload.
Dobutamine
1) Indications
2) Onset and Peak
3) Metabolism
1) Improve CO in heart disease
Recovery from cardiac surgery or MI
Pulmonary vasodilation for right heart failure or cor pulmonale
Increase CO and decrease SVR in mitral valve replacement.
Combo with DOPAMINE to ↑ renal perfusion
Comb with vasodilators to ↓CO by ↓afterload.
2) “Onset 1-2mins Peak effect in 10 mins”
3) MAO and COMT in blood, liver, and kidneys, GI tract. Conjugated to be excreted in the urine.
Dobutamine: Adverse Effect?
Fever
Headache
Paresthesia
Dyspnea
Tachycardia with high rates (increases conduction through AV node),SVT
Nausea
Thrombocytopenia and plt inhibition
Phlebitis, cutaneous necrosis
Down regulation of beta receptors after 3 days of tx = tolerance
TOXICITY = anorexia, NV, tremor, head, SOB, angina, chest pain, anxiety”
Dobutamine
1) Contraindications
2) Dosage
1) hypersensitivity
hypovolemia
CAD without CHF
Caution in pregnancy.
2) “0.5-1mcg/kg/min titrate every few mins to parameters
2-20mcg/kg/min with max dose 40mcg/kg/min”
Dopamine ( Inotropin)
1) Class
2) Action
1) “Endogenous catecholamine
Alpha, beta adrenergic, and dopaminergic receptor agonist”
2) “Low doses – agonize dopaminergic1 receptors in coronary, renal, and mesenteric vascular smooth muscle cells to stimulate G-CP, AC, cAMP
Medium doses – agonize beta1 adrenergic receptors in cardiac myocytes to increase contractility = +inotrope = ↑CO and HR
High doses – agonize alpha1»_space; beta1 in GU, GI, heart, liver smooth muscle and vascular smooth muscle = stim G-CP, AC, cAMP and inclux of Ca+ = ↑ smooth muscle contraction, vasoconstriction, and ↓renal perfusion”
Dopamine (Inotropin)
1) Indications
2) Onset
3) Metabolism
1) “Low doses = renal and mesenteric vascular dilation = ↑renal blood flow. Inhibit secretion of aldosterone = diuresis.
Medium doses - ↑CO to manage CHF and resp failure
Large doses = ↑BP and CO = for shock, septic shock, cardiogenic shock with dobutamine”
2) Rapid onset
3) MAO and COMT, beta hydroxylated to norepinephrine by dopamine bet-hydroxylase DBH. And then methylated to epinephrine in liver and plasma. Eliminated in the urine.
