Tetanus

Non-communicable infection of devitalised tissue by Clostridium tetani, which produces an exotoxin that causes life-threatening:

Epidemiology and Risk Factors

Significant public health problem of the developing world, due to a combination of:

  • High incidence
    Major risk factors include:
    • Unvaccinated
      • LMIC
      • Elderly
    • Rural
    • Poor
  • Requirement for prolonged ICU care

Pathophysiology

C. tetani is a Gram positive rod and obligate anaerobe that:

  • Exists in spore form in the environment
  • Is non-invasive
    Requires innoculation into a wound to produce infection - cannot grow in vitalised tissue.
  • Produces two exotoxins:
    • Tetanospasmin
      • LD50 0.01mg
      • Haematological spread
      • Uptake into motor nerve endings, and transport into nervous system
      • Diffuses into interstitium with, and acts on pre-synaptic terminals of nearby neurones
        Produces dysfunction of predominantly inhibitory interneurons:
        • Muscle spasms
        • Autonomic dysfunction
          Requires toxin to diffuse to lateral horns.
          • ↑ Sympathetic tone
        • Cognitive dysfunction
    • Tetanolysin
      Localised tissue destruction; clinically relatively unimportant.

Fun Fact:
~240g of tetanospasmin could kill the entire world population.

Aetiology

Mechanisms of C. tetani innoculation include:

  • Trauma
    • Puncture
    • Laceration
    • Dog bites
    • Piercings
  • Skin breakdown
    • Burns
    • Chronic ulcers
    • Dental infections
  • Other devitalised tissue
    • Abortion
    • Childbirth
    • Tetanus neonatorum
      Infection of umbilical stump.

Clinical Manifestations

Presentation:

  • Occurs following an incubation period
    A shorter incubation period indicates ↑ severity.
    • Usually >2 days
    • 90% <14 days
    • Up to 60 days
  • Pain
  • Musculoskeletal symptoms
    Progression:
    • Stiffness
    • Rigidity
    • Trismus
      Presentation typically at this point, which occurs due to masseter spasm.
    • Risus sardonicus
      Clenched-teeth expression relating to facial muscle spasm.
  • Autonomic dysfunction
    • Confined to severe cases
    • Begins after muscle spasms
    • Generally short-duration episodes of:
      • ↑↑ Sympathetic tone
      • ↑↑ Parasympathetic tone
        • Including sudden cardiac arrest
          Particularly in IVDU.

Tetanus neonatorum presents:

  • ~7th day of life
  • Short history of failure to feed

Diagnostic Approach and DDx

Include:

  • Local disease
    • Dental
    • TMJ disease
    • Infection
  • Neurological disease
    • Epilepsy
  • Toxidromes
    • TCA overdose
    • Strychnine poisoning

Investigations

No specific laboratory findings - diagnosis is clinical.

Bedside:

  • ABG
    Respiratory failure.

Laboratory:

  • Bloods
    • UEC
      Rhabdomyolysis.
    • CMP
  • Wound culture
    May grow C. tetani.

Imaging:

Other:

Management

  • Immunoglobulin to neutralise circulating toxin
  • Source control/wound care
  • Autonomic support

Resuscitation:

  • A
    • Intubation
      For control of muscle spasm.
  • B
    • Mechanical ventilation
      • If respiratory muscle involvement
      • Muscle relaxation if spasms prevent ventilation
        No particular agent is preferred.
  • C
    • Haemodynamic control
      Consider:
      • ↓ Catecholamine production
        • Sedation
          May require hefty doses, Oh’s quotes 3.4 grams of diazepam daily.
        • Opioids
          Heavy doses may also be required.
      • α/β Antagonists
        • Clonidine
        • Phentolamine, phenoxybenzamine
        • Esmolol
      • MgSO4
        Target 2.4-4mmol/L. May also assist in ↓ spasm.

Specific therapy:

  • Pharmacological
    • Human antitetanus immunoglobulin
      • 500 IU
      • Should be given to all patients who are not known to be immunised on presentation
      • Binds circulating toxin
    • Antibiotics
      Spores and bacteria are destroyed by:
      • Metronidazole 500mg IV Q6-8H for 10 days
        Preferred.
      • Penicillin G 1-3MU IV Q6H for 10 days
  • Procedural
    • Wound care
      Washout of contaminated wounds.
    • Source control
  • Physical

Supportive Care:

  • C
    • Haemodynamic control
      • Labetalol
      • Magnesium
      • Clonidine

Disposition:

  • ICU

Preventative:

  • Tetanus toxoid vaccine
    • Cheap
    • Three doses for full course
      2nd at 6-12 weeks, 3rd at 6-12 months.
    • Booster every 10 years
    • Occasionally results in local tetanus
      Spasm of limb or muscle.
    • Frequent doses may result in non-life threatening immune symptoms

Neonates have immunity via maternal antibodies until 3 months, and vaccination of pregnant women will protect children produced within 5 years.

Marginal and Ineffective Therapies

Complications

  • Death
  • B
    • Respiratory failure
  • C
    • Cardiac failure
      ↑ Catecholamines.
    • Hypertensive crises
  • D
    • Spasm
  • F
    • Rhabdomyolysis

Prognosis

  • Death
    • 80% without ICU care
    • 10% with mechanical ventilation
    • More common with:
      • Systemic tetanus
      • Cephalic tetanus
        Secondary to head and neck injuries with CN involvement.
      • Age
  • C
    • Arrhythmias
    • Cardiac failure
  • D
    • Spasm
      • Most resolve within 1-3 weeks
      • Residual stiffness may remain
    • Cognitive changes

Key Studies

References

  1. Bersten, A. D., & Handy, J. M. (2018). Oh’s Intensive Care Manual. Elsevier Gezondheidszorg.