Jacob Hummel M.D. Tulane University Anesthesiology Anticholinergics
Feb 23, 2016
Jacob Hummel M.D.Tulane University Anesthesiology
Anticholinergics
*Objectives
*Know the different mechanisms of action for atropine, scopolamine and glycopyrrolate
*Clinical use of each of these drugs
*Effects on the cardiovascular, respiratory, cerebral, G.I. and other organ systems
*Disclosures
*This is a really short lecture but its brevity does not reflect the value of its content
*Antimuscarinics
*This term is more indicative of what these drugs accomplish as they are primarily blocking the effects of acetylcholine at the muscarinic receptors
*Antimuscarinics
*Primary use is prior or concomitant administration with anticholinesterases
*Crucial in the treatment of bradycardia
*Beneficial in the prevention of PONV
*Antisialogogues
*The Antimuscarinics
*
*Structure and Binding
*Ester linkage essential for effective binding to the acetylcholine receptors, competitively inhibiting the binding of acetylcholine
*Different types of muscarinic receptors: neuronal (M1), cardiac (M2), and glandular (M3)
*Systemic Effects
*CARDIOVASCULAR*Blockade of the muscarinic receptors in the
sinoatrial node results in tachycardia
*Useful for reversing vagal reflexes
*Systemic Effects
*RESPIRATORY*Inhibit secretions along the respiratory tract
*Relaxes bronchial smooth muscle -> decreased airway resistance but increased dead space
*Systemic Effects
*CEREBRAL*Range of effects, stimulation to depression*Physostigmine reverses these occurrences
*Systemic Effects
*G.I.*Decreased secretions and salivation*Decreased peristalsis*Lower esophageal sphincter pressure
reduced
…better view, but more at risk for aspiration
*Systemic Effects
*Other Effects*Mydriasis*Urinary retention*Reduced sweating, rise in body temp
*Atropine
*Potent effects on the heart and lungs*Most efficacious for
treating bradycardia*Tertiary amine allows it
to cross blood-brain barrier*Derivative is ipratropium
bromide and used to treat bronchospasm*Use cautiously with heart
disease, narrow angle glaucoma, BPH and bladder-neck obstruction
Give me the atropine, NOW!
*Scopolamine
*Similar dosing to atropine, 0.01-0.02 mg/kg with adult dose around 0.4 - 0.6 mg*More potent
antisialogogue than atropine*Greater CNS effects*Lipid solubility allows for
the transdermal patch*Don’t touch your eyes
after you put a patch on someone!
*Glycopyrrolate
*Contains mandelic acid in place of the tropic acid seen in atropine*Dosing is usually half of the atropine dosing and used
for similar effects (bradycardia, antisialogogue, etc.)*Quaternary structure prevents crossing of the blood-
brain barrier*No ophthalmic activity*Potent antisialogogue*Longer duration of action than atropine (2-4 hrs. vs
30 minutes)
*Case Discussion
*An elderly patient is scheduled for enucleation of a blind, painful eye. Scopolamine, 0.4 mg intramuscularly, is administered as premedication. In the preoperative holding area, the patient becomes agitated and disoriented
The only other medication the patient has received is 1% atropine eye drops
*…how do you treat and would you proceed with the case?
*Anticholinergic Poisoning
*Signs and Symptoms*Agitation, delirium, unconsciousness*dry mouth, tachycardia, atropine flush,
atropine fever, and impaired vision
…antidote is physostigmine as it is the only anticholinesterase to cross the blood-brain barrier
*Proceed with the case?
*Elective Procedure*Is patient optimally medically managed?*Do symptoms resolve with intervention?
*Thanks for your attention
*GENERAL HUMMEL FROM ALCATRAZ….OUT!
*References