EM@3AM: Tetanus

Authors: Christopher J. Nelson, MD (EM Resident Physician, UTSW, Dallas, TX); Elizabeth Morley, PA-C (UTSW, Dallas, TX); Prayag Mehta, MD (Assistant Professor of EM, UTSW, Dallas, TX); Joby Thoppil, MD, PhD (Assistant Professor of EM, UTSW, Dallas, TX) // Reviewed by: Alex Koyfman, MD (@EMHighAK); Brit Long, MD (@long_brit)

Welcome to EM@3AM, an emDOCs series designed to foster your working knowledge by providing an expedited review of clinical basics. We’ll keep it short, while you keep that EM brain sharp.

Answer: Tetanus

Background

• Rarely seen in developed countries secondary to high rates of immunization
• Mortality approaches 28% and is associated with respiratory compromise and severe autonomic instability¹
• Worldwide deaths decreasing – ~275,000 in 1997 down to 14,132 in 2011²
  • Higher proportion in low resource settings²
• At risk populations include injection drug users, unimmunized individuals, foreign born individuals, and the elderly^3,4,5
• Tetanus is caused by Clostridium tetani, a spore producing obligate anaerobic gram-positive rod¹
  • Spores allow the bacteria to survive environmental extremes

Pathophysiology

• Clostridium tetani produces a neurotoxin that binds GABA and glycinergic neurons¹
• The toxin blocks pre-synaptic release, leading to a loss of inhibitory action on motor and autonomic neurons^1,6
• Incubation period of 3-21 days¹
  • Shorter with decreased distance between the injury site and the central nervous system¹
  • Shorter incubation periods are associated with a higher chance of death¹
• Four clinical forms:^1,5,7,8
  • Generalized
    • Usually begins with trismus and gradual onset of spasm of muscle groups in the trunk and extremities
  • Localized
    • Muscle rigidity near area of injury
    • May progress to generalized
  • Cephalic
    • Almost always after an apparent head wound or otitis media
    • Cranial nerve involvement (especially facial nerve), dysphagia, trismus
  • Neonatal
    • Due to infection of the umbilical stump, mostly from lack of maternal immunization
    • Occurring in the first week of life, irritability, and poor feeding rapidly progress into generalized spasms
    • Developing world cultural practices like application of clarified butter (ghee), cow dung and ashes, wrapping newborn in inverted sheep skin

History and Exam:

• Evaluation history of immunization
  • Completion of primary series
  • Date of last booster
• Social history
  • Injection drug use
  • Black tar heroin originating from Mexico has been associated with tetanus when compared to powder heroin³
• Medication history
  • Dystonic/serotonin/neuroleptic malignant syndromes can mimic a tetanus presentation
• Physical exam
  • Risus Sardonicus (“sardonic smile”)
  • Trismus (“lock-jaw”) in 75-80 % of cases⁸
  • Abdominal rigidity
  • Tonic contraction of skeletal muscles
  • Painful intermittent intense muscular spasms
    • Opisthotonos – abnormal posturing from arching of the head, neck and spine with flexion of the arms and extension of the legs.
    • Often triggered by sensory stimuli
  • Autonomic instability and hyperactivity (hypertension, tachycardia, diaphoresis, hyperthermia)

Differential:

• Botulism
  • Descending symmetrical flaccid paralysis^1,9
• Conversion Disorder
• Dystonic reaction^1,7,8
  • Associated with antipsychotic, anti-emetics, and antidepressants
  • Lateral head turning
• Hypocalcemic tetany
  • Trismus is rare¹
• Neuroleptic malignant syndrome⁸
  • Associated with antipsychotics and antiemetics
  • Presents with altered mental status, “lead pipe” rigidity, autonomic instability, hyperthermia
• Rabies
• Serotonin syndrome
  • hyperpyrexia, clonus, seizures, dilated pupil, muscle twitching, ataxia, and loss of consciousness¹
• Strychnine poisoning^1,8
  • Associated with gopher poison
  • Onset within 20 minutes of exposure

ED Evaluation:

• Clinical Diagnosis
• CBC (may have ↑ WBC), CMP, CK, lactate, blood cultures
• Serum and urine strychnine levels can be ordered but will not return in the ED

Management:

• Close assessment of airway and breathing
• Source Control – early wound debridement/incision and drainage
• Tetanus Immune Globulin (TIG) 500 U IM
  • May be injected directed into wound as well
• Tetanus toxoid vaccine as appropriate
• Antimicrobial therapy
  • Metronidazole 500mg IV Q6 hours¹⁰
  • Penicillin G 2 to 4 million units IV Q4-6 hours¹⁰
• Control muscle spasm¹¹
  • Diazepam – 5mg increments⁸
  • Lorazepam – 2mg increments⁸
  • Midazolam – 5-15mg/hr infusion⁸
    • Does not contain propylene glycol that may lead to lactic acidosis with diazepam and lorazepam
  • Management of dysautonomia
    • Magnesium sulfate for autonomic dysfunction and as adjunctive treatment for controlling spasms
      • 40mg/kg over 30 minutes followed by 2 g per hours for patient over 45kg⁸
    • Admission

Pearls:

• Injection drug users and unimmunized at risk
• Vaccine status must be considered in all types of wounds
• Consider administering tetanus toxoid vaccine in the ED for at-risk populations with wound infections, particularly IVDU
• Found in developing countries, acute tetanus is uncommon in the US and early signs of tetanus may create diagnostic dilemmas
• Even with optimal treatment, the mortality of tetanus is still high
• Strychnine poisoning should be high on the differential
• Close airway monitoring needed