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Flashcards in Toxicology Deck (52)
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1

Initial eval of pt presenting w/ overdose?

- ABCs
- ABGs
- IV access
- tx coma promptly:
glucose,narcan, if ETOHism suspected: thiamine
- maintain circ: crystalloid, if that doesnt work: swan to check PCWP (worry about over hydration and pulm edema)
- tx seizures: diazepam, if fails: phenobarbital
- cardiac monitoring and pulse Ox

2

Triad of opioid overdose?

- CNS depression
- miosis
- respiratory depression

3

When should emesis be induced?

- only in pts w/ intact gag reflex
- may have limited efficacy if more than 1 hr since ingestion
- most useful if initiated at home w/in few minutes of ingestion
- not indicated in ED for drugs not absorbed by charcoal (iron, lithium)
- don't induce emesis if caustics or low viscosity hydrocarbons have been ingested
- don't induce if rapid acting convulsants have been ingested (amphetamine, cocaine, TCAs, strychnine)
- ipecac syrup 30 ml for adults, 15 ml for kids followed by 1-2 liters of water until they vomit

4

When is a gastric lavage done?

- suspected serious ingestions when emesis has failed
- pt is lethargic or otherwise uncooperative
- when gag reflexed is markedly depressed
- pts have ingested rapid acting convulsants
- place pt in L lateral decubitus position w/ head down (protect airway)
- use large bore NG or OG tube at least 36Fr
- use tap water or saline at body temp in 250ml increments and continue until fluid returns clear and free of pil fragments

5

Use of activated charcoal in decontamination?

- following emesis or lavage give 50-100g charcoal as slurry by mixing w/ equal amts of water
- can give b/f or after lavage/emesis: however need residual charcoal left in gut
- mix charcoal w/ sorbitol to improve taste and cathartic action
- charcoal has great adsorptive properties and binds most poisions (EXCEPT: potassium, alcohols, iron, lithium - PAIL)
- if ingested dose of poison known- give at least 10x that wt in activated charcoal

6

When is whole bowel irrigation useful?

- w/ sustained release and enteric coated tabs
- golytely 1-2 L/hr until rectal effluent is clear

7

Lab studies for toxicology?

- ABGs
- draw blood for chem 7 and calc anion and osmolar gap
- obtain EKG and monitor for wide QRS or prolonged QT
- CXR looking for pulmonary edema
- flat plate of abdomen looking for radiopaque pills (high false neg)
- urine for tox screen
- draw and hold serum tox screens

8

1st order kinetics?

- fixed percentage of toxin is removed per unit time (barbs)

9

zero order kinetics?

- fixed amt of toxin removed per unit time (alcohol)
- many times in OD situations - elimination pathways are saturated and drug which normally has 1st order kinetics develops zero order

10

toxins w/ large volumes of distribution (tissue bound not plasma bound) are not efficiently removed by?

- dialysis or diuresis

11

Use of hemodialysis?

- toxin must be relatively water soluble and not protein bound
- toxin is removed from blood into dialysate soln across semipermeable membrane
- drugs need to have small vol of distribution and slow rate of intrinsic clearance
- indicated for: MELS - methanol, ethylene glycol, lithium, and salicylate

12

When is hemoperfusion preferred?

- advantage over hemodialysis: drug or toxin is in direct contact w/ adsorbent material - quick, can be used w/ activated charcoal
- drugs need to have small vol of distribution and slow rate of intrinsic clearance
- high MW, poor water solubility, plasma binding proteins not limited factors
- commonly assoc w/ thrombocytopenia and won't correct lyte imbalances, or adjust pH

13

Hemoperfusion is useful for what drugs?

TRI PEP-TD
-Tricyc antidepressants
- paraquat
- ethchlorvynol
- phenobarbital
- theophylline
- digitoxin

14

Antidotes for common ODs?

- APAP: acetylcysteine
- anticholinergics: physostigmine (also tx myasthenia gravis)
- benzos: Flumazenil (danger - can cause seizures, is a GABA antagonist)
- cyanide: Na nitrate and Na thiosulfate
- methanol/polyeth glycol (antifreeze): ethanol
- narcotics: naloxone

15

Most common cause of change in osmolar gap?

- ethanol

16

What occurs in APAP overdose?

- active ingredient in many OTC preps
- tylenol w/ mixed ODs (lortab, vicodin, darvocet)
- one of metabolites are very hepatotoxic:
saturates glutathione detoxification system, accum in liver and causes delayed hepatotoxicity 24-72 hrs post ingestion
- toxic dose is over 140 mg/kg (lower in pt w/ chronic liver disease, or alcoholism)
- draw up an APAP level

17

Tx of APAP overdose?

- decontaminate and give activated charcoal
- est severity:
amt ingested, best level is 4 hrs post ingestion
- ***acetylcysteine therapy:
subs for glutathione and binds to metabolite
- 140 mg/kg orally of 10-20% soln and follow up w/ 70 mg/kg dose q 4-8 hrs or until tylenol level is 0
- key: must be given EARLY - don't wait for initialy level, must be given w/in 12-16 but preferably w/in 8-10 hrs

18

Effects of cocaine/amphetamines?

- all are CNS stim and cause sympathetic hyperactivity
- some may produce sig vasoconstriction and cause HTN and bradycardia
- HTN may be accompanied by ventricular arrhythmias
- seizure and hyperthermia may produce rhabdo and myoglobinuria

19

Sxs of cocaine overdoses?

- euphoria
- excitement
- restlessness
- toxic psychosis
- seizures
- HTN
- tachycardia
- hyperthermia
- possible MI (prinzmental angina)

20

Dx and Tx of cocaine/amphetamine overdose?

- dx: sig toxicity will always have sxs, short half lives and peak effects occur w/in 12 hrs
-tx:
GI decontamination as indicated, severe agitation or psychosis: diazepam - tx seizures, if DBP over 120 or HTN encephalopathy: nitroprusside
- if tachycardia/vent arrhythmias: BBs
- monitor temp and EKG - may need CT of head
- don't acidify urine: myogloburia and ARF (rhabdo)

21

Anticholinergics that are used? Sxs?

- atropine, scopolomine, belladona, many antihistamines, TCAs
- seen in plants: jumsonweed, nightshade, amanita muscaria mushrooms
- block cholinergic receptors both centrally and peripherally
- sig poisoning always has some

-sxs:
delerium, blurred vision, mydriasis, hallucinations, coma, dry mucous membranes, inhibition of sweating, hyperthermia, tachycardia
- hot as a hare, red as a beet, dry as a bone, blind as a bat and as mad as a hatter

22

Tx of OD of anticholinergics?

- supportive care
- GI decontamination
- physostigmine slowly IV (only reserved for severe sxs):
must have atropine ready, pt must be on cardiac monitor, ***never use w/ tricyclic overdose, asthma, or mechanical bowel or bladder obstruction
- peak effects may be delayed due to sig delayed gastric emptying and slowed peristalsis through GI

23

MOA of anticoags and OD?

- warfarin MC used
- super warfarins (brodifacoum and indanediones) commony rodenticides
- inhibit blood clotting by blocking vit K dependent clotting factors
- only synthesis of new clotting factors affected - may be seen 8-12 hrs after ingestion
- peak effects are not seen for 1-2 days due to long half life of other clotting factors (24-60 hrs)
- warfarin highly bound to albumin w/ half life of 35 hrs/metabolized by the liver
- super anticoag may produce severe bleeding disturbances for several weeks to months following single overdose

24

S/S of anticoag toxicity?

- ecchymosis
- hematuria
- uterine bleeding
- melena
- epistaxis
- gingival bleeding
- hemoptysis
- hematemesis

25

Tx of anticoag toxicity?

- supportive therapy/GI decontamination
- obtain baseline PT and repeat in 24-48 hrs, vita K 1-2 mg can restore clotting factors in 6-8 hrs, in emergency give FFP!

26

Where is arsenic found?

- insecticides, rodenticides, wood preservatives contain trivalent arsenic
- shellfish may contain pentavalent arsenic (less toxic) which can cause + urine arsenic level but not assoc w/ clinical toxicity
- highly toxic arsine gas is produced by burning arsenic containing ores and is used in electronic industry
- arsenic is well absorbed from resp and GI tract and avidly binds w/ tissue proteins and accum in tissues
- lethal doses of trivalent arsenic is about 100-200 mg in an adult

27

S/S of acute arsenic ingestion?

- crampy abd pain, vomiting, profuse watery diarrhea, burning mucosa, conjunctivitis, tremor and seizurse
- garlic odor may be on pts breath
- periorbital edema after 1-2 days

28

S/S of chronic arsenic ingestion?

- peripheral and sensory neuropathy, malaise, anorexia, alopecia, anemia, stomatitis

29

S/S of arsine gas inhalation?

- highly toxic and causes rapid intravascular hemolysis and renal failure
- other sxs: usually not seen due to speed of onset of acute sxs

30

Tx of arsenic toxicity?

- 24 hr urine aresnic levels most useful for monitoring response to chelation therapy, false + levels are possible from eating shellfish
- tx:
*acute ingestion: GI decontamination w/ lavage and charcoal, admin dimercaperaol (BAL) for 5 days
* chronic ingestion: penicillamine
* arsine gas inhalation: transfusion may be necessary and adequate hydration to prevent renal hemaglobin deposition
- chelation therapy is of no value in acute exposure to arsine gas