Anticholinergics and Vasoconstrictors Flashcards
What do anticholinergics do at the muscarinic and nicotinic receptors?
Antagonize the effects of ACh at the muscarinic receptors
Exert little or no effect at the nicotinic receptors
What are the types of anticholinergic drugs?
Naturally occurring tertiary amines Semisynthetic congeners (quaternary amines)
What are the naturally occurring tertiary amines for anticholinergics?
Atropine and Scopalamine
What are the quaternary amines for anticholinergics?
Glycopyrrolate
Are anticholinergics agonists or antagonists?
Primarily competitive antagonists
How do anticholinergics work?
Reversibly bind with muscarinic receptor preventing ACh from binding
Increasing ACh overcomes the effect of the drug
Do anticholinergics drug/receptor combo alter the membrane?
No
T/F: Anticholinergics prevent the release of ACh and react with it
False, does not prevent the release of ACh or react with it
What are the 5 subtypes of anticholinergics?
M1: CNS and stomach M2: Lungs and heart M3: CNS, airway, smooth muscle, glandular tissue M4: CNS M5: CNS
Which muscarinic receptors are the most sensitive?
M3>M2>M1
Smallest doses decrease salivation
Dose to decrease H secretion will also affect M2 and M3 receptors
What are the doses of anticholinergics to work as an antisialagogue?
Atropine 10-20 mcg/kg
Scopalamine 5 mcg/kg
Glycopyrrolate 5-8 mcg/kg
T/F: At small doses all 3 drugs can produce heart rate slowing due to direct agonist effects
True
What are the other effects of anticholinergics?
Agonist at low doses
Indirect (interfere with the normal inhibition of release of endogenous NE)
Block the ACh inhibited release of NE
Presynaptic effects
Drugs have an effect like a sympathomimetic
What is the onset time for IV Atropine and Glycopyrrolate?
Atropine: 1 min
Glyco: 2-3 mins
What is the duration for Atropine and glycol?
30-60 mins
What are the uses of Anticholinergics>
Preop medication: sedation, antisaialagogue, and prevent vagal reflexes Treat reflex-mediated bradycardia Combined with anticholinesterase drugs Bronchodilation Prevent motion-induced nausea
Does atropine or glycol have increased incidence of memory deficits?
Atropine
What are some of the unwanted effects of anticholinergics when used as preop sedation?
Can be associated with restlessness to somnolence
Delay awakening particularly in elderly patients
Inhaled anesthetics can potentiate the CNS effects
Reverse with physostigimine
Use anticholinergics with caution in which type of patients?
Glaucoma and parturients
Mydriatic effect could increase IOP
Atropine and scope cross the placenta
Which aticholinergic is the most potent antisialagogue?
Scopalamine 3x more potent than atropine
Glyco 2x more potent than atropine with a longer DOA
Which drug is used frequently to blunt the vagal reflex associated with laryngoscopy for peds patients?
Atropine
What is the drug of choice for treatment of intraop bradycardia (laryngoscopy, carotid sinus, insufflation)
Atropine 15-70 mcg/kg IV
How do anticholinergics work when treating reflex-mediated bradycardia?
Act by blocking the effects of ACh on the SA node. Effect most evident on young adulats
What do anticholinergics do when combined with anticholinesterases?
Prevent the parasympathomimetic effects of anticholinesterases
How do anticholingerics work for bronchodilitation?
Due to antagonism of ACh effects of airway smooth muscle
Predominantly effect large and medium sized airways
Decrease airway resistance and increase dead space in bronchial asthma and chronic bronchitis
What are some less common uses that anticholinergics are used for?
Biliary and ureteral smooth muscle relaxant
Mydriasis and cycloplegia
Antagonize gastric H secretion
Non-prescription cold remedy
What is central anticholinergic syndrome?
Scope and atropine enter the CNS
What are the symptoms of anticholinergic syndrome?
Restlessness and hallucinations to somnolence and unconsciousness
How do you treat central anticholinergic syndrome?
Physostigmine 15-60 mcg/kg IV
What are the symptoms is you overdose on anticholinergics?
Dry mouth, blurred vision, photophobia, tachycardia
Dry and flushed skin
Increased tempt due to inhibition of sweating
Skeletal muscle weakness
Orthostatic hypotension
Can lead to fatal events (seizure, coma, medullary ventilator center paralysis)
What is the treatment for overdose of anticholinergics?
Physostigmine 15-60 mcg/kg IV
May need to repeat dose since it is metabolized rapidly
What are the direct and indirect effects of vasoactive drugs?
Direct effects on the heart and vasculature
Indirect effects mediated by the nervous system
What is the site of action for vasoconstrictors?
Arterial and venous smooth muscle
Systemic and pulmonary circulation
What are the 2 mechanisms of action for vasoconstrictors?
Receptor activation: Alpha1 agonists initiate a cascade of reactions through an intermediary G protein. The terminal products, protein kinase C and inositol triphosphate trigger the release of intracellular calcium resulting in smooth muscle contraction
Direct action: on smooth muscle (angiotensin)
What are the hemodynamic effects of vasoconstrictors?
Increase arterial resistance and afterload: Increase SVR and usually MAP
Increase venous return: increase preload and CO
In a failing heart, decreased SV may occur
What are the reflex changes for vasoconstrictors?
Decreased HR
Decreased conduction
Occasionally, decreased contractility
What are the indication for vasoconstrictors?
Decreased arterial resistance (hypotension)
-Could be iatrogenic (SAB, general anesthesia, vasodilator overdose) or physiologic (endotoxic or septic shock, hemorrhage)
Myocardial ischemia
CPR
Anaphylactic shock
Intracardiac right to left shunts
Hypovolemia
How do vasoconstrictors work for myocardial ischemia?
Maintain coronary perfusion
Used with coronary venodilators
Could worsen ischemia by increasing preload and wall tension
How do vasoconstrictors work for CPR?
Restore perfusion pressure to vital organs
Used in conjunction with other appropriate cardiac drugs
What are the contraindications/complications to vasoconstrictors?
Can worsen LV failure
Can exacerbate RV failure
Can decrease renal blood flow
Can mask hypovolemia
What are the types of vasoconstrictors?
Pure Alpha1 agonists
Mixed alpha1 and beta adrenergic compounds