Toxicology Flashcards
Name of toxic metabolite from acetaminophen
NAPQI (N-acetyl-p-benzoquinoneimine), overdose causes depletion of GSH and accumulation of NAPQI
Clinical effects/stages of acetaminophen overdose
- 0-24 hours - nausea, vomiting, malaise, pallor - normal AST/ALT and INR
- 12-72 hours - hepatotoxicity, RUQ pain - rising AST/ALT and normal or rising INR
- 72-96 hours - fulminant hepatic failure, encephalopathy, coma - AST/ALT > 10,000, elevated INR, elevated Cr, acidosis, lactemia
- > 96 hours - recovery with normalization of labs
Diagnosis of acetaminophen overdose
- Obtain serum APAP level 4 hours after ingestion
- Most important predictor of outcome is level taken at 4-10 hours post ingestion
- “Overdose” is taking 140 mg/kg or more
Clinical effects of aspirin (salicylate) overdose
- Vomiting, tinnitus, tachypnea, tachycardia, hypoxia, pulmonary edema, fever
- “Wintergreen” odor on breath
Diagnosis/management of salicylate overdose
- Labs: mixed respiratory alkalosis and metabolic acidosis
- Treatment with activated charcoal
- Aspirin level > 30 requires treatment with urinary alkalinzation (sodium bicarb), > 90 requires hemodialysis
Drugs that prolong QRS
- Bupivacaine, bupropion, carbamazepine, cocaine, diphenhydramine, lamotrigine, quinidine, TCAs
- Prolonged is > 100
- Tx with sodium bicarbonate
Drugs that prolong QTc
- Antipsychotics, fluoroquinolones, macrolides, methadone, ondansetron, SSRIs and SNRIs
- Prolonged is > 500 (but age specific)
- Tx with electrolyte correction (and mag)
Drugs that cause hypoglycemia
HOBBIES:
- Hypoglycemics (sulfonylureas, meglitinides)
- Other (unripened fruit, IV quinine)
- B-Blockers
- Insulin
- Ethanol
- Salicylates
Activated charcoal uses
- Dose is 0.5-1 g/kg
- If ingestion can cause respiratory depression, need to intubate before giving activated charcoal
- Don’t give charcoal with antidotes (interferes with absorption of the antidote), only acception is NAC
Toxins that don’t require activated charcoal
CALM
- Cyanide
- Alcohol/alkaline ingestion
- Lithium
- heavy Metals
Treatment of acetaminophen overdose
- Often asymptomatic initially so immediate ER discharge is never the right answer
- If < 4 hours since ingestion, give activated charcoal
- Treat with NAC if level is above nomogram (wait until 8 hours after ingestion to begin treatment)
- NAC works by protecting liver and body from oxidative stress of NAPQI and regnerates GSH
Anion gap equation
Sodium - (Chloride + bicarb)
Ibuprofen ingestion signs/symptoms and treatment
- Nausea and vomiting (on boards), asx in real life
- Treatment is supportive
- Should check for other drug ingestions though
Alcohol toxicity symptoms/levels
- Mild: BL 100 - euphoria, lowered inhibitions
- Moderate: BL 200 - slurred speech, ataxia, impaired judgement
- Severe: BL 300 - confusion and stupor, seizures
- Electrolyte disturbances: hypogylcemia
- Alcohol is also present in mouthwash, cough/cold meds, cologne, perfume
What is methanol found in
Windshield washer fluid, cooking fuel, perfumes, antifreeze
Clinical presentation/labs of methanol toxicity
Abdominal pain, vomiting, inebriation, severe metabolic acidosis, increased anion gap, CNS depression
- Gets broken down into formic acid and formaldehyde and can cause huge issues with the liver and optic nerve
Methanol toxicity treatment
- Administration of ethanol - alcohol dehydrogenase antagonist (slowing conversion of methanol to formaldehyde)
- Also can use 4-methypyrazole
- Soduium bicarb - counters formic acid
Ethylene glycol toxicity (3 phases)
- Phase 1: drunken appearance with no alcohol odor, large anion gap metabolic acidosis, hypocalcemia d/t crystals in the urine, hypertension, N/V
- Phase 2: coma and cardiorespiratory failure
- Phase 3: 1-3 days, renal failure due to ATN
Organophosphate toxicity
- SLUDGE: salivaiton/sweating, lacrimation, urination, defecation/diarrhea, gastrointestinal, emeesis
- Can be lethargic and have respiratory distress
- Insecticide ingestion, unwashed fruits and veggies
- Mechanism of action: inhibiting acetylcholinesterase (cholinergic effects)
Muscarinic cholinergic effects and treatment
- Salivation, lacrimation, diarrhea, wheezing, bradycardia
- Tx: atropine
Nicotinic cholinergic effects
- Neuromuscular, weakness, paralysis, muscle fasciculations
Tx: pralidoxime
Tricyclic antidepressants toxic ingestion
- Anticholinergic effects: Blind as a bat (mydriasis, dilated pupils), Red as a beet, Hot as a hare, Dry as a bone, Mad as a hatter, Bowel and bladder lose their tone, Heart runs alone
- Need to monitor EKG for widening QRS complex (treat iwth sodium bicarb until QRS is < 100)
- Tx: activated charcoal
Beta blocker ingestion side effects
- Bradycardia, hypotension, sweating
- Monitoring is all thats needed
Hydrocarbon ingestion
- Gasoline, kerosene, lighter fluid
- Gastric irritation, nause, vomiting, choking/gagging, cough, wheezing
- Labs with hypoxemia and CXR with diffuse bilateral infiltrates –> can lead to ARDS
- Tx is symptomatic
Carbon monoxide toxicity symptoms
- Sudden flu like illness in an afebrile patient (headache, vomiting, weakness, fatigue)
- Symptoms in other family members or recent death of a small family pet
Carbon monoxide toxicity workup/treatment
- Carboxyhemoglobin levels
- Oxygen saturations are unreliable
- Give high flow 100% oxygen
Cyanide poisoning
- Presents like carbon monoxide poisoning but failure to respond to oxygen therapy
- Smell of almonds
- Tx: hydroxocobalamin
Treatment for ingestion of caustic substance
- Endoscopy within 24 hours to determine extent of esophageal injury
- No gastric lavage with caustic ingestion
Alkaline ingestion
- Alkali substances tend to injure the esophagus and can lead to esophageal perforation
- Ingestion of dishwasher detergent or drain cleaner
- Also watch for signs of burns on the face/hands/chest
Lead screening and levels
- > 27% of housing built before 1950
- Level 5-14: report, venous sample in 3 months, do environmental history/screening
- Level 15-44: report, venous sample in 4 weeks, consider xray if pica
- Level 45-70: report, venous sample in 48 hours
- Level > 70: report, venous sample immediately
Lead toxicity treatments
- Level as low as 10 can lead to cognitive deficit
- Level 45-70 give outpatient chelation if symptomatic (oral succimer)
- Level > 70 need hospitalization and IV chelation (edetate)
- Need a venous sample to base treatment (not capillary)
Lead sources
- Lead based paint in older homes
- Household dust, soil
- Glazed ceramics, storage battery casings, bullets, cosmetics, leaded glass, jewelry, farm equipment
Toxic iron ingestion amount and phases
- 40 mg/kg of elemental iron is “toxic”
- Phase 1: within 6 hours - vomiting, diarrhea, abd pain
- Phase 2: slight improvement for 6-24 hours
- Phase 3: metabolic acidosis, coagulopathy, cardiovascular collapse
- Phase 4: GI obstruction due to scarring and strictures
Management and treatment of iron toxicity
- Lead level 4 hours post ingestion
- Labs/imaging: abdominal film, electrolytes, liver function, CBC, coagulation
- Tx: indications for chelation with deferoxamine are anion gap acidosis, serum iron > 500, significant iron on abdominal film
- Deferoxamine turns the urine pink/red when serum iron level exceeds serum iron binding capacity - can stop when urine is no longer pink
PCB exposure in utero
Low birthweight, dark pigmentation, early eruption of teeth, acneiform rash –> can be fatal
Anthrax
- Cutaneous form, incubation period is less than 2 weeks
- Lesions are pruritic papules –> central bullous lesion –> necrosis –> central black painless eschar
Coin ingestion treatment
- Proximal esophagus should be removed by endoscopy immediately
- Middle to lower esophagus can be observed for 12-24 hours if asymptomatic, if in stomach it can just be observed for passage
- Coins in the esophagus usually face forward on the PA film and from the side on the lateral film (opposite if in trachea)
Three ingested objects that can’t be ignored
- Button batteries, sharp/pointed objects, magnets –> all high risk for perforation so need immediate endoscopy
Discoloration of blood, normal PaO2, clinical evidence of cyanosis
Methemoglobinemia
- Exposure to exogenous oxidizing drugs: amyl nitrite, butyl nitrite, isobutyl nitrite
