Toxicology

Question 1

Discuss the ABCDDEFG of toxicology

Answer 1

Airway
- ensure patent airway
Breathing
- Provide oxygen if hypoxic
Circulation
- cardiac monitoring or ECG
- IV fluids for all
DONT (universal antidotes)
- Dextrose IV for hypoglycemia
     - most toxins lead to hypoglycemia so require bedside blood glucose
- O2
- Naloxone 0.4mg IM for suspected opioid or respiratory depression
- Thiamine for alcoholic
Decontamination
- water irrigation for toxins on skin
- GI decontamination can do activate charcoal if within 1-2hrs of ingestion
- whole bowel irrigation
Elimination
- dialysis for aspirin, digoxin and toxic alcohol
Focused Therapy
- specific antidote
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Question 2

Discuss the anion gap and osmal gap calculations

Answer 2

Anion Gap
- Na - (Cl + HCO3) = 12 (normal)
Osmol Gap
- Expected osmolality: 2xNa + Blood glucose + BUN
- osmol gap <10 normal, >10 abnormal
- Raised due to alcohol, ethylene glycol, methanol, mannitol, DKA

Question 3

Discuss the investigations for toxicology

Answer 3

• Electrolytes
• Creatinine, BUN
• blood glucose
• serum osmolality
• Serum specific drugs (acetaminophen, aspirin, digoxin, anti-epileptics, toxic alcohol)
• Blood gas for metabolic acidosis (low pH, pCO2 and compensatory low HCO3
• ECG
• Tox screen

Question 4

Discuss the differential for metabolic acidosis

Answer 4

MUDPULESCT
- Methanol, metformin
- Uremia
- Diabetic Ketoacidosis
- Paraldehyde
- Iron, isoniazid
- Lactate
- Ethylene glycol
- Salicylates
- CO, cyanide
- Toluene
Increased Ion Gap (>12) and Increased Osmol Gap (>10)
- toxic alcohol

Question 5

Discuss the toxidrome for Opioids

Answer 5

Vitals
- Bradycardia
- Hypotension
- Respiratory depression and hypoxia
Presentation
- Decreased LOC
- miosis (constricted pupils)
Management
- Naloxone 0.4mg IM
- IV fluids

Question 6

Discuss the toxidrome for Anticholinergics

Answer 6

- TCA, antihistamines (benadryl, Gravol)
Vitals
- tachycardia
- Hypertension
- Hyperthermia
Presentation
- Confusion, agitated
- mydriasis
- dry mouth
- dry skin
- urinary retention
- constipation
Management
- supportive with cooling, IV fluids, benzodiazepine
- antidote for TCA
- NaHCO3 IV for prolonged QTc

Question 7

Discuss the toxic dose and diagnosis of acetaminophen overdose

Answer 7

Dose
- 150mg/kg
Diagnosis
- based on the Rumack-Matthew nomogram and acetaminophen level at least 4hrs post-ingestion
- if above can proceed to treatment as risk of hepatic toxicity

Question 8

Discuss the presentation of acetaminophen overdose

Answer 8

Stage 1 - Day 1
- Non-specific nausea and vomiting
Stage 2 - Day 1-3
- Hepatitis (RUQ pain, elevated AST/ALT)
- pancreatitis
- acute renal failure
Stage 3 - Day 4-5
- Liver failure (jaundice, coagulopathy, hypoglycemia, encephalopathy)
- renal failure
- multi-organ failure
Stage 4 - Day 5-10
- eventual recovery in liver function

Question 9

Discuss the treatment of acetaminophen overdose

Answer 9

• If within 1hr then charcoal for GI decontamination
• if taken above toxic dose then automatic treatment with N-acetylcysteine
  
  • Cannot give after 8hrs
  • replenish store of glutathione which continues to detoxify NAPQI

Question 10

Discuss the toxidrome for aspirin

Answer 10

Dose
- >300mg/kg
Presentation
- Neurologic: tinnitus, confusion, seizure
- GI: n/v leading to hypovolemia
- Resp: hyperventilation due to metabolic acidosis
Investigation
- serum ASA
- blood gas
Management
- IV fluids
- urine alkinalization by IV NaHCO3 to get urine to pH >7.5 to facilitate clearance
- hemodialysis

Question 11

Discuss the toxidrome for toxic alcohol

Answer 11

Pathophysiology
- methanol form formic acid and ethylene glycol form oxalic acid which lead to metabolic acidosis
Presentation
- Formic acid: altered mental status, ataxia, seizure, decreased visual acuity
- Oxalic acid: renal failure
Investigation
- serum osmalality raised by methanol and ethylene glycol
- blood gas
- serum toxic alcohol level
Management
- antidote: ethanol IV or fomepizole
- block alcohol dehydrogenase to prevent conversion into toxic metabolites
- hemodialysis

Question 12

Discuss the patholophysiology of cocaine intoxication

Answer 12

Blockade of pre-synaptic biogenic amines which increases level of biogenic amine
- increase dopamine
- increase catelcholamine which increases SNS activity
- increase heart rate, BP, heart contractility leading to increase oxygen demand by the heart
- coronary artery vasoconstriction and increased thrombus formation
Up-regulation of Glutamate and Aspartate in Brain
- lead to euphoria
Blockage of Na Channel
- slow or block nerve conduction leading to analgesia
- delay electrical cardiac conduction causing QRS prolongation and arrhythmia

Question 13

Discuss the presentation and management of cocaine intoxication

Answer 13

Vitals
- tachycardia
- hypertension
- hyperthermia
Presentation
- agitated
- mydriasis
- chest pain, palpitation
Investigation
- CK, creatinine as can lead to rhabdomyolysis
- ECG
Management
- Benzodiazepine for agitation/hypertension
- If severe hypertension or symptomatic alpha 1 adrenergic antagonist phentolamine 1-5mg IV Q5-15 min
- aspirin and nitro if CP as well
- NaHCO3 1-2mEq/kg IV if QRS prolongation
- hypoglycemia then dextrose and thiamine
- rhabdomyolysis IV fluids to maintain urine output 1-3mL/kg/hr

Question 14

Discuss medications that are contraindicated in cocaine intoxication

Answer 14

Succinylcholine
- may worsen hyperthermia and rhabdomyolysis causing hyperkalemia
Beta Blocker
- lead to unopposed alpha-adrenergic stimulation and further coronary vasoconstriction and ischemia