Tetanus

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- Is a potentially lethal condition characterised by muscular rigidity and spasms, caused by the tetanospasmin toxin produced by Clostridium tetani

Types:

  • cephalic
  • local
  • generalised
  • neonatal (50% of tetanus deaths worldwide)

Tetanospasmin

  • taken up by motor nerves or haematogenous spread to CNS
  • preferentially prevents discharge from GABA inhibitory interneurons in spinal cord and brainstem -> unrestricted motor nerve activity and autonomic instability

Clinical features:

Clinical triad of rigidity, muscle spasms and, autonomic dysfunction

  • contaminated wound or umbilical stump in neonates
  • incubation period: 3-14d = time to first symptom
  • rigidity (persists > 2 weeks) — trismus, dysphagia, increased tone in trunk muscles – greater on side of injury initially
  • spasms (reduce after 2 weeks) — spontaneous or provoked by physical or emotional stimuli, laryngospasm, risus sardonicus, opisthotonos (severe spasm in which the back arches and the head bends back and heels flex toward the back)

  • autonomic disturbance (onset after spasms, lasts 1-2 weeks) — tachycardia and hypertension may alternate with bradycardia and hypotension, dysrhythmia, cardiac arrest — salivation, bronchial secretions — gastric stasis, ileus, diarrhoea
  • respiratory compromise — chest wall rigidity — laryngospasm — aspiration — retained secretions

Td Prophylaxis:

  • Past vaccination unknown or <3 total
    • Clean wound → Td
    • Dirty wound → Td & TIG
  • Past vaccination 3 or more total
    • Clean wound → Td Q10yrs
    • Dirty wound → Td Q5yrs

Management:

A – intubate because management requires large doses of sedatives to control muscle spasm and to overcome laryngospasm B – at risk of aspiration and have copious bronchial secretions requiring frequent suctioning, often ventilated for 2-3 weeks until spasms subside C – autonomic dysfunction requires monitoring in a critical care environment D – benzodiazepines in large doses (up to 100mg/h diazepam)

Specific Therapy:

  • metronidazole (first choice); penicillin is used throughout most of the world but is a GABA antagonist
  • anti-tetanus immunoglobulin: 100-300IU/kg of human Ig IM
  • benzodiazepines; adjuncts include barbiturates, propofol, chlorpromazine
  • Mg to 2-4mmol/L as useful in spasm treatment and limits autonomic instability
  • consider dantrolene (unproven)
  • clean and debride wounds (source control)
  • immunize (infection does not confer immunity) – Q10 yearly

Prognosis:

Mortality >50% if untreated (usually due to respiratory failure)

Sources: Life in the fastlane, WikiEM

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