Toxicology Flashcards
Assessment of poisoned patient- Physical exam
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.
Assessment of poisoned patient- pupil size
Mydriasis (dialated)- adrenergic agonists and anticholinergics
Miosis (constricted)- sympatholytics and cholinergics
Assessment of poisoned patient- history
substance ingested, time since ingestion, sx, prior therapies, and prior medical conditions
Labs for poisoned patient
If it does not change what you will do for the patient do not order it.
Chem 7
Quantitative labs
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.
Qualitative labs
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.
Steps for managing poisoning
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
Supportive care
Stabilize the patient- monitor ABCs
Monitor for complications as they arise
Assess and treat for shock
Hypovolemic shock
Loss of fluid, decreased CO due to decreased preload.
Fluids, inotropes/vasopressors
Cardiogenic shock
Decreased CO due to decreased stroke volume (typically due to a decreased in myocardial contractility; iron, CCB, BB, cyclic anitdepressants)
Distributive shock
Redistribution of blood from central compartment to peripheral vasculature.
Prevent further absoprtion
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.
GI decontamination- general indications
Substantial risk of serious toxicity
Recent ingestion
Can be performed safely and will work
No alternative is available
GI decontamination- general contraindications
Rapid onset of seizures
Rapid onset of CNS depression
Alkaline corrosives (acid controversial)
Loss of gag reflex
Emesis
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
Syrup of Ipecac
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.
Lavage
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
Lavage ADRS
Aspiration, esophageal/gastric bruising, fluid/electrolyte imbalance, EKG, changes, hypoaxia, and esophageal rupture.
Activated Charcol
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
Activated charcol- cathartics
Promote movement of AC bound drug through GI tract, may cause hypovolemia and electrolyte imbalance
Activated charcol ADR
Vomiting, constipation, aspiration, GI obstruction, charcoal empyema, GI perforation.
Whole bowel irrigation
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
Enhancing elimination- indications
Impaired normal route of elimination
severe presentation
progressive deterioration despite full supportive care
significant toxicity expected
Enhancing elimination- Methods
Multiple dose activated charcoal Ion trapping Hemodialysis Forced diuresis Exchange trasfusions
Multiple dose activated charcoal
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
Iron trapping
Change pH of urine to ionize poison preventing reabsoprtion. Weak acids (salicylate, pehnobarbital) admin sodium bicarb to achieve a urine pH of >7
Antidotes
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
Chelators
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
Antivenins/biologics
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
Pharmacologic Antagonists
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.
