Tetanus

Definition

• Acute disease characterised by general rigidity & convulsions caused by exotoxins produced in Clostridia tetani infections

Epidemiology

• Annual world mortality now is 1 million
  • Britain 15/ year
  • USA 100/ year
  • Especially Rural areas

Aetiology & Pathology

• Clostridium tetani
  • Gram positive Bacillus
  • Anaerobic
  • Spore-forming
• Spores
  • Drumstick appearance (spores form at one end of the rod)
  • In faeces/ manure, dust & soil
  • Especially hot damp climates
  • Resistant to antiseptics & heat
  • » Autoclave for 10 minutes
• Infection
  • Clostridium tetani is non-invasive
  • Occurs when spores enter tissues & produce vegetative forms
    • Entry through defect in epidermis
      • Puncture/ laceration
      • Surgery
      • Burns
      • Dental infection
      • Abortion
      • Childbirth
    • No history of wound in 20%
  • Germination in O2 poor media
    • Oxygen poor wounds
    • Foreign bodies
    • Infection
  • Infection remains localised » exotoxin spreads & produces effect
  • Spores may enter tissue & lie dormant with later activation
• Tetanospasmin
  • Exotoxin released when vegetative bacteria lysed in wound
  • Potent Neurotoxin
    • 0.1mg lethal in Man
    • Spreads to CNS via PNS/ BV/ lymphatics
    • Blocks inhibitory pathways in cord
    • Muscle rigidity with paroxysmal spasms or convulsions result
    • Self-limiting
  • No residual effects
• Tetanolysin
  • Haemolysin

Clinical Features

• Mean incubation 1/52
  • 90% in < 15/7
  • Varies 2-60/7
• Severity relates to rapidity of onset
• Tetanus-prone wound
  • Open fracture
  • Puncture
  • Foreign body
  • Contamination
  • Tissue damage +++
  • > 6/52
  • Septic wound
  • Bite

Presenting symptoms

• Pain & stiffness in
  • Jaw
  • Risus sardonicus
    • Clenched teeth expression
  • Abdomen
  • Back
  • Difficulty swallowing
• Generalized rigidity
  • Trismus or lockjaw
  • Spinal extension & neck retraction
  • Upper limb flexed & lower limb extended
• Reflex spasms
  • Follows at 24-72 hours
  • Due to external stimuli (eg. Noise)
  • May see laryngeal spasm » arrest
• Sympathetic dysfunction
  • Seen only in severe cases
  • Hypertension, Tachycardia, Sweating
  • Arrhythmias, Ileus
• Can last 3-6 weeks
• Complications include
  • Hypoxia
  • Aspiration
  • Pneumonia
  • CV problems
  • Electrolyte abnormalities
  • Wedge fractures of vertebrae
  • Secondary infections
  • Hyperpyrexia
  • Bleeding problems – DIC & PUD
• 20% no obvious cause of death

Complications

• 60% die in 2/52
• Spasms disappear by 1-3/52
• If survive, recover by 6/52
• Respiratory complications are major cause of death

Investigations

• No specific tests
• Clostridium tetani cultured from wound in 1/3

Prophylaxis

Active Primary Immunization

• Tetanus toxin rendered non-toxic by formalin to produce tetanus vaccine
  • Tetanus toxoid (TT)
    • 0.5ml adsorbed toxoid
  • Triple antigen (CDT or ADT)
    • Diphtheria-Tetanus-Pertussis (previously called DPT)
• Antibody production takes several weeks & protection lasts ~10 years

Primary Immunization in Children

• Triple Antigen at 2, 4 & 6/12
• CDT at 18/12 & 5 years
• (EMST says 3 injections DPT then booster every 15 years)

Primary Immunization in Adult

• Only for those never immunized
• 3 courses of tetanus toxoid
  • 6/52 between 1st & 2nd
  • 6/12 between 2nd & 3rd
  • Should not repeat the full course
• Booster
  • TT/ ADT booster every 10 years
  • If more than 20 years since booster then
    • 2 boosters of TT/ ADT with 4-6/52 interval between doses
• Reactions include
  • Urticaria
  • Angiooedema
  • Diffuse indurated swelling at site of swelling

Passive Immunization

• Tetanus Immunoglobulin (TIG)
• 16% solution of gamma globulin fraction of donated plasma
• Give in tetanus-prone wounds
  • If not immune
  • Never if immune
• Dose is
  • 250 units IM
  • 500 units IM if wound grossly contaminated, result of burns, delay > 24 hrs
• Into different limb from TT when giving both

Secondary Prophylaxis after Injury

• If immunized » TT or ADT will produce protective antibodies in 1/7
• If patient not immune » need full tetanus toxoid course
• The following is EMST protocol

Patient previously fully immunised

• Wound not Tetanus-prone
  • If < 10 years since TT » nothing
  • If > 10 years since TT » single TT
• Wound Tetanus-prone
  • If < 5 years since TT » nothing
  • If > 5 years since TT » single TT

Patient not adequately immunised or unknown

• Wound not Tetanus-prone
  • Give 0.5ml TT
• Wound Tetanus-prone
  • Give 250-500 units TIG
  • + 0.5ml TT in other arm
  • ± penicillin

Treatment

• Wound care
  • Debride necrotic & contaminated tissue
• Antibiotics
  • Vegetative form sensitive to antibiotics
  • Tetanus spores destroyed by antibiotics at high doses
  • Use Penicillin G
    • 2 Million Units (1.2g) q4h for 10/7
  • If allergic to penicillin use
    • Erythromycin
    • Tetracycline
• Antitoxin
  • Intravenous TIG is more concentrated TIG for treating clinical tetanus
    • 400-10 000 IU diluted with saline & given by infusion over 15 minutes
  • Neutralises the circulating toxin
  • Does not affect the toxins already fixed in CNS
  • Side effects include
    • Fever
    • Shivering
    • Chest or back pains
• Other
  • Spasms control
    • Quiet dark room
    • Diazepam
    • Consider Thiopental infusion
  • Care of airway
    • Ventilation if
      • Severe spasms
      • Respiratory failure
      • ± Tracheostomy
  • Hydration & electrolytes monitored
  • Nutrition monitored
  • Sympathetic overactivity controlled by alpha & beta blockers

Contraindications

• Only CI to TT is previous severe allergic reaction
• Differentiate from allergy to hypersensitivity to tetanus antitoxin in horse serum
  • Passive immunisation
  • Withdrawn 30 years ago
  • Replaced by TIG
• Differentiate TT allergy to TIG allergy
  • Give TIG if allergic to TT & tetanus-prone wound present

Prognosis

• Related to severity of attack & assessed by
  • Incubation period
  • Onset time
  • Occurrence of spasms
  • Complications
  • Age of patient
• Now mortality rate is 25% (vs 50% in past)