Toxicology

Toxidromes:

Anticholinergic
Sympathomimetic /Stimulant
Sedative-Hypnotic (EtOH)
Opiate
Cholinergic
Organophosphates
Specific toxins: Salicylates, Acetaminophen

Anticholinergic

Features:         – Blind as a bat (mydriasis, cycloplegia)

– Mad as a hatter (hallucination, confusion, agitation)

– Red as a beet (flushed)

– Hot as a pot (fever)

– Dry as a bone (dry mucous membranes and dry skin)

– Bowel and bladder lose their tone (ileus, urinary retention)

– Heart runs alone (tachycardia)

Toxins: anticholinergics, antihistamines, antispasmotics (i.e. Ditropan/ oxybutynin), Jimson weed, tricyclic antidepressants, phenothiazines, atropine and antipsychotics

Antidote: Physostigmine (1-2mg IV over 5 minutes)

Treatment: supportive

 

TCAs

• • Death due to cardiac effects: tachycardia and EKG changes
  • Charcoal, alkalinize the urine, supportive (fluids for hTN), benzos for seizure control

Sympathomimetic/Stimulant

Features:

– Agitation
– Diaphoresis*
– Hypertension
– Mydriasis
– Tachycardia

Toxins: amphetamines, cocaine, MAO inhibitors

Treatment: supportive and benzodiazepines

Sedative-Hypnotic

Features:

– CNS depression
– Respiratory depression
– Hypotension
– Bradycardia
– Hypothermia

Toxins: EtOH, barbiturates, benzodiazepines and GHB (i.e. date rape drug)

Antidote: For benzodiazepines use flumazenil

TOXIC ALCOHOLS

Ethylene glycol

• Antifreeze, solvents
• Antidote is fomepizole or EtOH IV, but must give thiamine 100mg and pyridoxine 100mg (minimalize oxalic acid)

            Methanol

• May cause blindness or death
• Antifreeze, varnish, paint remover
• Urine may look fluorescent
• Antidote is fomepizole or EtOH IV, but must give folate 50mg first (minimalize formic acid)

Isopropyl alcohol (not really a toxic alcohol)

• Rubbing alcohol

Narcotic

Features:

– Coma/↓LOC
– Respiratory depression
– Miosis

Toxins: opioids, narcotics

Antidote: Naloxone (0.2-0.4mg IV)

Cholinergic (muscarinic)

Features:         DUMBELS (or SLUDGE)

– Defecation
– Urination
– Miosis
– Bradycardia and bronchorrhea
– Emesis
– Lacrimation
– Salivation
– May be diaphoretic and tachycardic

Toxins: organophosphates

Antidote: For organophosphates use Atropine (0.5mg IV at a time to end point of dry secretions)

Cholinergic (nicotinic)

Features:         MTWtHFS

– Muscle cramps
– Tachycardia
– Weakness
– Hypertension
– Fasciculations and paralysis
– Sugar (hyperglycemia)

Toxins: tobacco, black widow spider venom

Salicylates

Features:

– Acid-base (respiratory alkalosis → AG metabolic acidosis)
– CNS (confusion → coma)
– Electrolytes (pyrexia, ↑RR, and vomiting → fluid loss, dehydration and ↓K)
– GI (N/V, pain)
– Ototoxicity (tinnitus)
– Pulmonary edema
– Anticoagulation (inhibit vit K dependent synthesis – factors 2,7, 9, 10)

Notes: Minimum acute toxicity 150mg/kg.  Affects CNS, Kreb’s cycle enzymes, and decouples oxidative phosphorylation.  NaHCO₃ is used to alkinalize urine (diuresis).

Acetaminophen

Features:

– Four phases of clinical presentations (children present early, adults present late)

– Stage 1: GI (mild)

– Stage 2: 24-48hr, may feel well but liver enzymes rise

– Stage 3: 3-4d, jaundice, coagulopathy, hepatic encephalopathy

– Stage 4: 5+d, recovery, LFT’s start to normalize

Notes: 140mg/kg or 7.5g over 24hr; mostly metabolized in the liver; NAPQI is the toxic metabolite (glutathione depletion) causing oxidative liver injury

Antidote: N-acetylcysteine based on acetaminophen levels 4 hr post ingestion (or initial presentation) = consult nomogram

Delirium Tremens

Features

– Occurs hours after heavy drinking
– Tremors
– Irritability
– Nausea/Vomiting
– Altered mental status (hallucinations, confusion, agitation)
– Seizures

Treatment: monitors, IV access, O₂, C/S with dextrose if needed, benzodiazepines (Diazepam 5-10mg IV, or Librium 50-100mg IV, or Lorazepam 2-4mg SL/IV), labs (CBCD, electrolytes, Mg, LFTs, amylase, EtOH, CK if suspect rhabdomyolysis), IV fluids with multivits, thiamine 100 mg IV, referral for EtOH counselling (i.e. AADAC)

History

• Who? -coingesters (rave drugs)
• What?
• When? -peak effects, decontamination
• Where? -other exposures (CO)
• Why? -psych, peds
• How? -site, route, IV>inhaled>IM/SC>oral>dermal
• How much? Toxicity

Physical exam

• Rule out other injuries
• Look for toxidromes

Overdose approach

• As always start with ABCs and vitals (reassess frequently)
• Large bore IV with crystalloid
• Monitors
• Depending on LOC consider thiamine, dextrose, O_2, naloxone
• Look for toxidromes… always consider that patient may have taken more than one drug
• Investigations:
  • Basic bloodwork, serum osmolarity, serum betaHCG
  • Tox screens: ASA, acetaminophen, EtOH, toxic alcohols
  • EKG
  • Xray
    • Radiopaque toxins:
      • Chloral hydrate
      • Heavy metals
      • Iodides
      • Phenothiazines
      • Enteric-coated pills (bezoar of pills)
      • Solvents
    • Body packers may have obvious findings on plain films
  • ABG
• Management
  • Supportive and monitoring
  • Antidotes
  • Decontaminate
    • Ipecac – contraindicated depending on airway and in bowel perforation/obstruction
    • Charcoal (1g/kg) – if w/i 30 minutes; ineffective for Li, Fe, Fluoride, alcohols, caustic acids/bases
    • Osmotic lavage – OG, w/i 30 minutes, patent airway, contraindicated if <8yr
    • Cathartics – magnesium citrate
    • Whole bowel irrigation – Go Lytely, cocaine OD
  • Enhanced elimination
    • Dialysis – lithium, salicylates, ethylene glycol, methanol, Br, isopropyl alcohol
    • Hemofiltration
    • Digoxin poisoning – may use digibind
    • Change pH of blood or urine

Osmolar gap

• Calculate the difference between the serum osmolarity and [2Na⁺ + BUN + Glucose]
• Normal = ~10

Anion Gap Metabolic Acidosis

• Methanol
• Uremia
• DKA
• Paraldehyde
• Isoniazide
• Lactic acid
• Ethylene glycol (and EtOH via ketoacidosis due to starvation)
• Salicylates
• Cyanide
• Arsenic
• Toluene

Calculation of Anion Gap

•  Na – (Cl + HCO₃)
• Normally 12 +/- 2 meq/L