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Toxicology [advanced]

Include in assessment

  • History – what taken, how much, when, why, co-ingestion (e.g. alcohol)
  • Examination – GCS, pupils, localising signs, track marks, burns/blistering, skin colour/sweating
  • 12 lead ECG
  • Bloods: usual bloods (FBC, U&Es, LFTs, INR, CRP, glucose) plus venous blood gas, urine tox screen if available, paracetamol level, and salicylate level if salicylism/↓GCS/↑anion gap
  • Osmolar gap (true measured serum osmolality – calculated serum osmolality (Na+x2 + urea + glucose)): if >10, something else is in system causing difference e.g. alcohols/glycols
  • Anion gap ((Na+ + K+) – (Cl- + HCO3-)): normal is 3-12, increases when a new acid has been added to body (e.g. a toxin which has been converted to an acid; lactate; ketoacids)

Common toxidromes

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Common syndromes

  • Serotonin syndrome (e.g. SSRIs, TCAs, ecstasy, linezolid, tramadol): altered mental state, hyperthermia, autonomic dysfunction, rhabdomyolysis; PLUS neuromuscular hyperactivity (tremor, clonus, hyperreflexia), sweating, mydriasis  
  • Neuroleptic malignant syndrome (e.g. antipsychotics, when stopping dopaminergic drugs): altered mental state, hyperthermia, autonomic dysfunction, rhabdomyolysis; PLUS muscular rigidity, hyporeflexia, stupor

Management

General management

  • Activated charcoal (50g drink)
    • Can be given in overdoses <1 hour of ingestion (<4 hours if tricyclic) to reduce absorption of many orally ingested toxins
    • Only if patient can swallow properly (must have GCS 15)
    • NOT FOR: acids&alkalis, alcohols, metals, organic solvents 
  • Supportive ABCDE-style management
    • The major part of management for most overdoses is continuous, supportive ABCDE-style management
      • A:   recovery position, airway adjuncts
      • B:   oxygen, treat hypoventilation
      • C:   cardiac monitor, IV fluids to maintain BP, treat brady/tachycardias (bicarbonate for acidosis)
      • D:   diazepam for seizures, treat hypo/hyperthermia
  • Control adverse effects e.g. seizures
  • Haemofiltration may be required (lithium, salicylate, ethanol, ethylene glycol, methanol)

Specific management

  • A database (e.g. Toxbase) should be used to guide specific management (but examples for common overdoses are below)
  • Specific antidotes
    • Paracetamol → N-acetylcysteine
    • Morphine → Naloxone
    • Beta-blocker → Atropine, glucagon
    • Benzodiazepam → Flumazenil (NOT given for overdoses – risk of seizures)
    • Digoxin → Digibind
    • Warfarin → Vitamin K, prothrombin complex concentrate
    • Heparin → Protamine sulphate
    • Carbon monoxide → Hyperbaric/100% oxygen
    • Volatile solvents → Methylene blue for slate-grey cyanosis
    • Iron → Desferrioxamine
    • Sulfonylurea → Octreotide
    • Lead → Sodium calcium edetate
    • Cyanide → Vitamin B12
    • Copper → Penicillamine
    • Methotrexate → Folinic acid (Leucovorin), glucarpidase
    • Ethylene glycol or methanol (e.g. antifreeze) → Fomepizole (or, if unavailable, ethanol)
    • Organophosphate (e.g. pesticide) → Atropine, pralidoxime

Psychological management (in deliberate overdose)

  • Assess risk
  • Assess capacity if tries to abscond or refuses treatment
  • Psychiatric referral

Common overdoses

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