Sympathomimetic agents Flashcards
Epinephrine receptors
Alpha-1 higher doses- associated with widening pulse pressure (DBP unchanged)
Beta-1 -increase chronotropy, inotropy, lusitropy and dromotropy
and Beta-2- low dose vasodilation helpful in acute RHF, 0.01-0.05 mcg/kg/min
Epinephrine Indications
Anaphylaxis
ACLS
Hypotension w/bradycardia- or unresponsive to indirect acting
Refractory asthma
Epinephrine Adverse
Hypokalemia- beta 2 stimulation causes uptake of K in skeletal muscle
Hyperglycemia- liver glycogenolysis- and inhibition of insulin secretion
Lactic acidosis
Myocardia ischemia- increases O2 utilization
Tachyarrhythmias
Severe hypertension with coadministration of B blocker
Isoproterenol
Pure Beta (1&2)
Don’t forget about B-2 vasodilation!
Indication: high degree AV block prior to pacemaker
Norepinephrine
Alpha-1 and Beta-1
-increased SVR can lead to lower CO despite B1- HR unchanged due to baroreceptor
-PVR increase- alpha-1
-Renal and splanchnic blood flow decrease
Norepinephrine indication and adverse effects
Septic shock- lower incidence of arrhythmias than dopamine
Advers: myocardial ischemia (high afterload), organ hypoperfusion due to intense vasoconstriction- other impacts of high SVR
Dopamine
Alpha-1 -high dosing
Beta-1 -moderate dosing
and
Dopamine-1=vasodilation with increased GFR and decreased SVR at low dose- no impact on AKI
We have better agents for septic and cardiogenic shock
Arrhythmias!!
Dobutamine
Beta 1»»Beta 2- no alpha
Indications:
Low CO after CPB
RHF with elevated PVR- comparable to milrinone
Adverse: tachycardia, arrhythmias, myocardial ischemia
LVOT (O)
Left Ventricular Outflow Tract Obstruction
Essentially obstruction of forward flow from a variety of causes placing strain on the ventricle and leading to hypertrophy from increased afterload
Levosimendan
Calcium sensitizer
Increased inotropy and vasodilation- decreased preload and decreased afterload
Support of acutely decompensated CHF
Adverse: myocardial ischemia, hypokalemia
Phenylephrine
Non-catecholamine!!
Pure alpha with reflex bradycardia
Treatment of mild hypotension during general surgery
Adverse:
LV dysfunction with increased afterload
RV dysfunction in setting of pulmonary hypertension
Severe hypertension
Ephedrine
Long duration?
Causes release of endogenous catecholamines- which stimulate Alpha-1 Beta-1 and Beta-2
“Mild epinephrine”
Adverse: hypertension and tachycardia
Crosses BBB!! Insomnia and agitation
Urinary retention in patients with BPH
Milrinone and other Inodilators
PDE 3 inhibitor
increased CO with decreased SVR and PVR
Indications: weaning CPB
RHF dependent on MAP- combined with vasopressin for decreased MAP
Many advantages over catecholamines after CPB
Can treat cerebral vasospasm
Adverse: increased O2 consumption, interferes with platelet aggregation
React in IV tubing with lasix
Vasopressin
Antidiuretic hormone
V-1 receptors to stimulate vasoconstriction
Constricts renal efferent arterioles=increase in GFR
Indications:
Intraop hypotension for patients on ACE inhibitors or ARBs
Non-hemodynamic uses for vasopressin & adverse
Anti-diuresis via V-2 in renal collecting duct: treatment of diabetes insipidus
Improved platelet function- von willebrand or antiplatelet agents
Control esophageal variceal bleeding
Adverse:
Mesenteric ischemia
Bradycardia, afib
Hyponatremia
Digoxin
Cardiac Glycoside
Inhibits Na/K pump via ATPase
-Causing rise in intracellular Na- which is then exchanged for Ca
Ca is mainly pumped into SR during diastole- however this just leads to increased release during systole
Increases Vagal tone=bradycardia!!
Digoxin adverse
Narrow therapeutic index: AV conduction block, Brady, ventricular arrhythmias, N/V, visual changes
Electrolyte imbalances:
Hypokalemia=increased dig toxicity
Hypercalcemia= increased dig toxicity
Multiple drug interactions: all increase risk of toxicity
Amiodarone
Verapamil
Itraconazole
Macrolide antibiotics
Quinidine
Which receptor stimulation of Epi causes stabilization of mast cells and why is it important?
Beta
Decreases the release of histamine, and other inflammatory mediators that perpetuate the pathophysiology of anaphylaxis
Impact of giving epinephrine with Beta blockers
Alpha stimulation in the absence of Beta mediated vasodilation leads to severe hypertension and heart failure
Why is vasopressin favored to counteract milrinone induced hypotension over norepinephrine
It decreases PVR
Norepi increases PVR!! Although it also increases right ventricular perfusion pressure…. Making it useful in RHF
Treatment of phenylephrine induced hypertension
Alpha-1 antagonist (phentolamine)
Or
Direct vasodilator- hydralazine
NOT beta blockers or calcium channel blockers- cardiac depressants can result in acute HF
What is vasopressin
Nonapeptide hormone synthesized in neurons of the hypothalamus
It is released by posterior pituitary
Does of ephedrine
5-10mg
Tachyphylaxis with repeat dosing
Neuro complications of ephedrine
Crosses the BBB causing agitation and insomnia
