Neurology
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A 60 year old farmer presents to ED following an incident where he sustained a dog bite to his face from his working sheepdog. He has a 2 cm laceration to his lower lip. It is determined that this is a tetanus-prone wound and that he requires tetanus immunoglobulin. He is unsure of his vaccination status. Which of the following reasons indicates a need for tetanus immunoglobulin in this patient?
Answer:
Guidelines for management of tetanus-prone wounds state:- Those who have not received an adequate priming course of tetanus vaccine (including people who have uncertain immunisation status and/ or people who were born before 1961) should receive an immediate reinforcing dose of vaccine & one dose of human tetanus immunoglobulin at a different site.
Tetanus is an acute disease caused by the action of the tetanus neurotoxin (tetanospasmin) produced by the bacterium Clostridium tetani, an anaerobic spore forming bacillus. Tetanus spores are widespread in the environment, including in soil and manure. They can survive hostile conditions for long periods of time. Transmission occurs when spores are introduced into the body, often through a puncture wound but also through trivial, unnoticed wounds, through injecting drug use, and occasionally through abdominal surgery. The bacteria grow anaerobically at the site of the injury and have an incubation period of between three and twenty one days.
Tetanus
- Clinical features:
- The most common presentation of tetanus is generalised tetanus, however two other forms, local and cephalic, are also described:
- Generalised tetanus is characterised by trismus (painful muscular contractions primarily of the masseter and neck muscles leading to facial spasms), tonic contractions and spasms. Tonic contractions and spasms may lead to dysphagia, opisthotonus and a rigid abdomen. In severe cases they may cause respiratory difficulties. Autonomic instability is typical. Consciousness is not affected.
- Localised tetanus is rigidity and spasms confined to the area around the site of the infection and may be more common in partially immunised individuals. Localised symptoms can continue for weeks or may develop into generalised tetanus.
- Cephalic tetanus is localised tetanus after a head or neck injury, involving primarily the musculature supplied by the cranial nerves.
- The most common presentation of tetanus is generalised tetanus, however two other forms, local and cephalic, are also described:
- Investigations:
- Tetanus is primarily a clinical diagnosis. The key clinical features of generalised tetanus include at least two of: 1) trismus, 2) painful muscular contractions of trunk muscles and 3) generalised spasms.
- Laboratory tests are available to support the clinical diagnosis. Although a serum sample should be taken before administering immunoglobulin, treatment of clinical case of tetanus should never be delayed to wait for the laboratory results. Laboratory investigations available to support a diagnosis of tetanus are:
- Detection of C.tetani in wound material or from a pure isolate (most sensitive test)
- Detection of toxin in serum
- Detection of IgG against tetanus toxin in serum
- Management:
- Wound debridement
- Antimicrobials including agents reliably active against anaerobes such as intravenous benzylpenicillin, metronidazole can be used, discuss with local Microbiology team about choice of antibiotics and doses
- Intravenous Immunoglobulin (IVIG) based on weight (5,000 IU if < 50 kg or 10,000 IU if > 50 kg)
- Vaccination with tetanus toxoid following recovery
- Supportive care (benzodiazepines for muscle spasms, treatment of autonomic dysfunction, maintenance of ventilation, nursing in a quiet room etc.)
Definition of tetanus-prone wounds
Clean wounds are defined as:
- wounds less than 6 hours old, non-penetrating with negligible tissue damage
Tetanus-prone wounds include:
- puncture-type injuries acquired in a contaminated environment and likely therefore to contain tetanus spores e.g. gardening injuries
- wounds containing foreign bodies
- compound fractures
- wounds or burns with systemic sepsis
- certain animal bites and scratches - although smaller bites from domestic pets are generally puncture injuries animal saliva should not contain tetanus spores unless the animal has been rooting in soil or lives in an agricultural setting
High risk tetanus-prone wounds are any of the above with either:
- heavy contamination with material likely to contain tetanus spores e.g. soil, manure
- wounds or burns that show extensive devitalised tissue
- wounds or burns that require surgical intervention that is delayed for more than six hours are high risk even if the contamination was not initially heavy
Management of tetanus-prone wounds
Thorough cleaning of wounds is essential and surgical debridement of devitalised tissue in high risk tetanus–prone wounds is crucial for prevention of tetanus. If the wound, burn or injury fulfils the above criteria, IM-TIG or HNIG should be given to neutralise toxin. A reinforcing dose of tetanus-containing vaccine should also be considered based on the immunisation status. Consider treating tetanus prone wounds with antibiotics (metronidazole, benzylpenicillin or co-amoxiclav) depending on clinical severity with a view to preventing tetanus.
Determination of vaccination status may not be possible at the time of assessment and therefore a number of Point of Care antibody (POC Ab) have been developed. There is currently a lack of evidence on use of point of care antibody testing in the clinical pathway, and this it is currently not recommended for use in assessment of tetanus-prone wounds or diagnosis of suspected tetanus by the WHO. Determination of vaccination status using vaccination records remains the preferred method.
| Immunisation Status | Clean Wound | Tetanus Prone Wound | High Risk Tetanus Prone Wound |
|---|---|---|---|
| Those aged ≥ 11, who have received an adequate priming course of tetanus vaccine with the last dose within 10 years
Children aged 5-10 years who have received priming course and preschool booster Children under 5 years who have received an adequate priming course |
None Required | None Required | None Required |
| Those who have received an adequate priming course of tetanus vaccine but the last dose was > 10 years ago
Children aged 5-10 years who have received an adequate priming course but no preschool booster |
None Required | Immediate reinforcing dose of vaccine | Immediate reinforcing dose of vaccine & one dose of human tetanus immunoglobulin at a different site |
| Those who have not received an adequate priming course of tetanus vaccine
Includes uncertain immunisation status and/or born before 1961 |
Immediate reinforcing dose of vaccine | Immediate reinforcing dose of vaccine & one dose of human tetanus immunoglobulin at a different site | Immediate reinforcing dose of vaccine & one dose of human tetanus immunoglobulin at a different site |
Important considerations:
- An adequate priming course is defined as at least 3 doses of tetanus vaccine at appropriate intervals. (N.B. This definition of “adequate course” is for the risk assessment of tetanus-prone wounds only. The full UK schedule is five doses of tetanus containing vaccine at appropriate intervals.)
- The dose of human tetanus immunoglobulin (IM-TIG) is normally 250 IU by intramuscular injection, or 500 IU if more than 24 hours have elapsed since injury or there is a risk of heavy contamination or following burns. The dose is the same for both adults and children.
- In the absence of IM-TIG, the human normal immunoglobulin (HNIG) product Subgam 16% can be used instead.
- Tetanus vaccine should be injected at a different site from immunoglobulin so that it is not 'neutralised' by the passive immunisation.
- Patients who are severely immunosuppressed may not be adequately protected against tetanus, despite having been fully immunised. In the event of an exposure they may require additional boosting and/or immunoglobulin.
- For those whose immunisation status is uncertain, and individuals born before 1961 who may not have been immunised in infancy, a full course of immunisation is likely to be required.
- For those who are incompletely immunised, further doses should be offered to complete the recommended schedule to protect against future exposures.
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
