Toxicology

Question 1

Assessment of poisoned patient- Physical exam

Answer 1

PE- blood pressure (90-140/90-55 mmHg), Pulse (60-100bpm), respiratory rate (8-14 breaths/min), temp (98-100.4 F)
Age and weight are important for initiation of therapy and to know how the patient will handle to poisoning.

Question 2

Assessment of poisoned patient- pupil size

Answer 2

Mydriasis (dialated)- adrenergic agonists and anticholinergics
Miosis (constricted)- sympatholytics and cholinergics

Question 3

Assessment of poisoned patient- history

Answer 3

substance ingested, time since ingestion, sx, prior therapies, and prior medical conditions

Question 4

Labs for poisoned patient

Answer 4

If it does not change what you will do for the patient do not order it.
Chem 7

Question 5

Quantitative labs

Answer 5

Assessment of poison concentration in tissues.
Useful for poisons with antidotes.
APAP, carboxyhemoglobin, methemoglobin, digoxin, heavy metals, iron
Useful for dialysis- ethylene glycol, methanol, lithium, salucylates, theophylline.

Question 6

Qualitative labs

Answer 6

Tell you if its present or not
Urinary toxicology screen tests for the presence of the toxin in the urine. Expressed as present of absent. Many false positives
Radiograph for radiopaque compounds.

Question 7

Steps for managing poisoning

Answer 7

1) supportive care
2) prevent further absorption (keeping the poison from systemic absorption)
3) Enhance elimination ( use of things like dialysis to pull the drug out of the body)
4) Provide antidote

Question 8

Supportive care

Answer 8

Stabilize the patient- monitor ABCs
Monitor for complications as they arise
Assess and treat for shock

Question 9

Hypovolemic shock

Answer 9

Loss of fluid, decreased CO due to decreased preload.

Fluids, inotropes/vasopressors

Question 10

Cardiogenic shock

Answer 10

Decreased CO due to decreased stroke volume (typically due to a decreased in myocardial contractility; iron, CCB, BB, cyclic anitdepressants)

Question 11

Distributive shock

Answer 11

Redistribution of blood from central compartment to peripheral vasculature.

Question 12

Prevent further absoprtion

Answer 12

Depends on route of exposure- inhalation: fresh air, oxygen, dermal: irrigation with water, removal of contaminated clothing, Ocular: eye irrigation, ingestion: emetic, lavage, activated charcoal, WBI.
Benefit of gastrointestinal decontamination- reduces poison bioavailability.
Shows no evidence of improvement in morbidity or mortality.
Patients at greatest risk will receive the most benefit.

Question 13

GI decontamination- general indications

Answer 13

Substantial risk of serious toxicity
Recent ingestion
Can be performed safely and will work
No alternative is available

Question 14

GI decontamination- general contraindications

Answer 14

Rapid onset of seizures
Rapid onset of CNS depression
Alkaline corrosives (acid controversial)
Loss of gag reflex

Question 15

Emesis

Answer 15

Same general indications and contraindications as GI decontamination adding patients that ingest sharp objects or with hemorrhagic dx to contraindications.
Typically used in rural areas with a delay of >1 hour before patient arrives to ED
Ipecac

Question 16

Syrup of Ipecac

Answer 16

Onset 15-20 minutes
95% vomit in 20 mins, 30% reduction in bioavailability at 1 hour
Side effects- acute- diarrhea, drowsiness, chronic- cardiac arrhythmia’s, neuropathy, muscle weakness.

Question 17

Lavage

Answer 17

Orogastric retrieval of substance.
30% reduction in bioavailability at 1 hr.
Lavage fluid-saline
End point- clear returns
Indications- same as general
Contraindications- same except can lavage pts with CNS depression if intubated and cuffed w/ endotracheal tray. If seizures are controlled and patient is intubated.
DO NOT LAVAGE patient with underlying pathology of esophagus or stomach

Question 18

Lavage ADRS

Answer 18

Aspiration, esophageal/gastric bruising, fluid/electrolyte imbalance, EKG, changes, hypoaxia, and esophageal rupture.

Question 19

Activated Charcol

Answer 19

Absorbant 1gm/kg
Will NOT bind- low molecular weight, charge compounds; cyanide, bromide, potassium, ethanol, methanol, iron, lithium, alkaline corrosives, mineral acids, highly concentrated solutions such as gasoline, kerosene, and ETOH
Efficacy 40% reduced bioavailability at 1 hour

Question 20

Activated charcol- cathartics

Answer 20

Promote movement of AC bound drug through GI tract, may cause hypovolemia and electrolyte imbalance

Question 21

Activated charcol ADR

Answer 21

Vomiting, constipation, aspiration, GI obstruction, charcoal empyema, GI perforation.

Question 22

Whole bowel irrigation

Answer 22

Reserved fro substances not absorbed to AC, very large ingestions, significant GI hemorrhage, intestinal obstruction, unprotected airway, hemodynamic instability
Endpoint- clearing of rectal effluent
Solutions used- golytely used primarily prior to colonoscopy

Question 23

Enhancing elimination- indications

Answer 23

Impaired normal route of elimination
severe presentation
progressive deterioration despite full supportive care
significant toxicity expected

Question 24

Enhancing elimination- Methods

Answer 24

Multiple dose activated charcoal
Ion trapping
Hemodialysis
Forced diuresis
Exchange trasfusions

Question 25

Multiple dose activated charcoal

Answer 25

Interrupts entero-enteric and entero-hepatic recirculation of poison and or poison metabolite
Indications- theophylline, carbamazepine, phenobarbital overdose
Contraindications- ileus, intestinal obstruction, unprotected airway
ADR- pulmonary aspiration, constipation, fluid and electrolyte imbalance

Question 26

Iron trapping

Answer 26

Change pH of urine to ionize poison preventing reabsoprtion.
Weak acids (salicylate, pehnobarbital) admin sodium bicarb to achieve a urine pH of >7

Question 27

Antidotes

Answer 27

Properties of a good antidote-
Completely reverses or neutralizes the effects of the poison
No action of its own
Easy to adminster
No unpleasant side effects

Question 28

Chelators

Answer 28

Used for metal poisonings because they bind to metal
Dimercaprol (BAL)- uses for As, Hg, Pb, Cd and toxicities include HTN and tachycardia
Penicillamine- uses for Cu, Pb, Hg, As, toxicities include allergic rxns
DMSA (succimer)- used for Pb, As, Hg, toxicities include Gas and ABD pain
Edetate calcium disodium (EDTA) used for Pb and toxicities include nephrotoxicity
Deferoxamine- used for Fe, toxicities include hypotension, anaphyactoid rxn and ARDS

Question 29

Antivenins/biologics

Answer 29

Crotalidae Antivenin- rattle snake envenomation
Lactrodectus Antivenin- black widow spider envenomation
Elapidae Antivenin- eastern and texas coral snake envenomation
Trivalent botulinum- botulisms type A, B, and E
Digoxin immune fab- digoxin and digitoxin

Question 30

Pharmacologic Antagonists

Answer 30

N-acetylcysteine- poisoning is acetaminophen and mechanism is prevents NAPQI binding at hepatocyte.
Naloxone- poisoning is opioids and mechanisms is opioid receptor antagonist
Flumazenil- poisoning is benzodiazepines and mechanism is benzodiazepine receptor antagonist
Atropine- poisoning is organophosphates and pesticides and mechanism is muscarinic receptor antagonist
Fomepizole- poisoning is methanol and ethylene glycol and mechanism is blocks metabolite formation.