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, O2, 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

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