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34 Cards in this Set
- Front
- Back
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Explain difference between pre and post ganglionic Horner's syndrome and how the response to hydroxyamphetamine will differ.
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Pre - lesion is in preganglionic nerve
Post - lesion is in postganglionic nerve Hydroxyamphetamine (HA) causes NE leakage at sympathetic postganglionic synapse of the radial muscle of eye. Therefore if patient responds to HA with mydriasis, lesion is preganglionic (postganglionic intact), if not, the lesion is postganglionic |
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What is denervation supersensitivity and how does it manifest in Horner's syndome?
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DS is an increased sensitivity to NT due to upregulation of receptors in the absence of stimulation. Therefore a smaller NT dose will produce a larger or equal effect. In Horner's, a 1% phenylephrine dose will cause mydriasis in Horner's eye but not in normal eyes.
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Where does aqueous humor come from and where does it exit?
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Secreted by posterior chamber (between iris and lens) by specialized epithelial cells covering the ciliary body.
Exits through the anterior chamber via 2 routes: (1) canal of Schlemm, which is a venous sinus and (2) reabsorption by into ciliary muscle (uveoscleral flow). |
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What is acute angle closure glaucoma?
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It may be caused by the administration of a topical mydriatic medication to facilitate fundoscopic examination of the eye. As the radial muscle of the iris contracts to increase the diameter of the pupil, the iris may acutely obstruct the flow of aqueous humor from the posterior to the anterior chamber. The eye becomes painful and red. Emergency and temporizing treatment is with an osmotic diuretic (intravenous mannitol or oral glycerol). Thedefinitive treatment is to perform a surgical iridectomy.
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What is open angle glaucoma?
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Poor flow from the canal of Schlemm leads to increased intraocular pressure. Can be primary (idiopathic) or secondary (to trauma or inflammation). Untreated chronic OAG can cause loss of visual fields and later to blindness. Early on it is usually asymptomatic and painless.
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How is primary open-angle glaucoma treated?
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medications that decrease synthesis of aqueous humor or increase the outflow of aqueous humor (either by increasing flow in the canal of Schlemm or by increasing uveoscleral flow). These can include many drug classes, such as muscarinic agonists, AChE inhibitors, CA inhibitors, adrenergic agonists, beta-antagonists, PGF antagonists, alpha aonists. In the past pilocarpine (muscarinic agonist) was used often to cause miosis and increased flow of AH (side effects, such as poor night vision, myopia (nearsightedness). Carbachol is alternative.
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What history is extremely important in a suspected poisoning?
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If the patient is conscious and cooperative, obtaining the exposure
history is of paramount importance. The identity of the poison, the time and route of exposure, and the amount of the exposure are the critical facts to obtain in order toguide therapy. |
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What is syrup of ipecac?
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Induces vomiting. Given in response to toxin ingestion. Contraindicated in persons with diminished consciousness (aspiration risk), volatile substance ingestion (avoid pulmonary ingestion), rapidly-acting poison (to save time).
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What is gastric lavage?
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Large tube is inserted into stomach via mouth and alternatively irrigated and aspirated. Risks are aspiration and esophageal perforation. contraindicated in persons who have ingested caustic, volatile, or rapidly acting substances.
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What is activated charcoal?
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Adsorbs organic compounds and thus prevents GI absorption. Given PO or via nasogastric tube. Does not adsorb ionized compounds or strong acids/bases. Recommended after gastric lavage.
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How can you increase rate of excretion of a drug?
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Give diuretic and also make urine more acidic or basic to increase ionized form of drug so it is trapped in urine.
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What makes a drug a good candidate for dialysis?
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water-soluble, minimally bound to plasma proteins, have a low molecular weight (< 500), and have a long terminal kinetic phase. Examples of poisons that may be removed by dialysis include alcohols, ethylene glycol, lithium, and salicylates.
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Pilocarpine
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Muscarinic agonist. ALKALOID, as opposed to the catecholamines (acetylcholine, bethanechol, methacholine, carbachol). has some M1 specificity. Increases BP. Used clinically in xerostomia, glaucoma, and diagnosing Adie's disease (parasym postganglionic lesion)
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Name the muscarinic antagonists.
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Atropine
Scopolamine (CNS depressant, Parkinson) Dicyclomine (intestinal hypermobility, IBS) Ipratroprium (Asthma, COPD) Mydriasis agents: Tropicamide Cyclopentolate M3 specific that reduce urinary urgency: Tolterodine Oxybutynin Darlifinacin BOTOX prevents ACh release |
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What are the non-depolarizing NMJ blockers?
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Tubocurarine, vecuronium, pancuronium.
Used as skeletal muscle relaxants |
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What is given for an overdose of skeletal muscle relaxants / NMJ blockers?
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AChE inhibitors, increase competition for nicotinic receptors by ACh.
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What is edrophonium useful for?
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Short lasting AChE inhibition.
Useful to distinguish between myasthenia gravis and a cholinergic crisis. |
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Pralidoxime
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AChE regenerating drug, dephosphorylates AChE in case of AChE poisoning. Must be given quickly after poisoning before AChE enter the "aged" state
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Dipivefrin
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Epinephrine prodrug. Used to treat glaucoma because it decreases IOP.
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How does epinephrine treat glaucoma? What are effects on eye?
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ALPHA2 AGONISM: Decrease aqueous humor production AND increase uveoscleral flow.
BETA2 AGONISM: Increase outflow through canal of Schlemm. |
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Name all the sympathomimetics and any important features
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Amphetamine (long lasting, no MAO or COMT metabolism)
Dextroamphetamine (potent CNS, fewer peripheral effects, given to soldiers to stay awake) Methamphetamine (more potent, can cause CV events such as MI, arrhythmias, stroke, incr CO, etc) Methylphenidate (Ritalin) Hydroxyamphetamine (used to determine location of Horner's lesion) Ephedrine (2 stereocenters, mild stimulant and decongestant) Pseudoephedrine (1 enantiomer of eph) Tyramine (not clinically used, vasopressor) |
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What is dapiprazole used for?
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alpha antagonist, used to reverse mydriasis induced by phenylephrine
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Phentolamine?
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alpha 1-2 adrenergic antagonist. used for pheochromocytoma (rare adrenal tumor), cocaine induced hypertension, is a dirty drug.
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Carbonic anhydrase inhibitors and what they are useful for...
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Dorzolamide (topical) and Acetazolamide (systemic). Decrease aqueous humor production/secretion from the ciliary body. Treatment for glaucoma. Acetazolamide alkalates urine and can lead to kidney stones and paresthesias.
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Prostaglandin analogue and what they are useful for...
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Latanoprost (Xalantan). Is a prodrug that when metabolized is a prostaglandin (PGF) agonist. Increases uveoscleral flow to treat POAG. Causes brown pigmentation of iris and eyelids, proliferation of eyelashes.
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How do you treat acetominophen poisoning?
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N-acetylcysteine (Mucomyst), which can react with NAPQ reactive intermediate like glutathione would. Must be given within 36 hours of exposure. Tastes vile.
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Treatment for cyanide (CN-) poisoning?
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Sodium nitrite to convert hemoglobin to methemoglobin, since CN- binds preferentially to met-Hb (Fe3+ state), decreasing availability to block oxidative phosphorylation.Sodium thiosulfate given as substrate for rhodanase enzyme (detoxifies CN-). 100% O2. Tandem gastric lavage if time permissible.
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What is Calcium Disodium versenate (EDTA)?
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Chelating agent given for exposure to heavy metals. Given IV every few weeks to allow tubules to heal. Also chelates calcium. Not to be given to those with kidney failure.
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What is dimercaprol?
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Originally an Arsenic antidote. Now used to treat As, Hg, and Pb (in conjunction with EDTA) poisonings. Urine must be alkalated during therapy to ensure excretion via kidney. Given as a solution in peanut oil in deep IM injection.
Many side effects (incr BP, HR, headache, nausea, vomiting, pain and burning feeling, ) |
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Pencillamine?
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Given orally, a chelating agent used for Pb, Hb, As, poisoning. Causes cutaneous lesions, systemic lupus, bone marrow suppression, proteinuria, hematuria.
Can be isolated from urine of patients taking penicillin, was originally used to treat Wilson disease. |
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Naloxone?
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Opioid antagonist
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Indications for using dialysis?
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Poison is water soluble, low MW, not protein bound
Examples: ALCOHOLS (ethanol, methanol, isoproanol) |
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What diseases can cause generalized peripheral neuropathy?
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Diabetes, amyloid, immune mediated, hereditary, toxic (chemo, alcohol, solvents), HIV
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What diseases can cause pure autonomic peripheral neuropathy or gangliopathy?
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Post infectious immune mediated autonomic neuropathy
•Idiopathic pure autonomic failure (Bradbury-Eggleston Syndrome) •Iatrogenic: surgical thoraco-lumbar sympathectomy 27 |
