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Hyperkalemia in Adults: Review of a Common Electrolyte Imbalance
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DIAGNOSIS
Tetanus is a clinical diagnosis, usually made based on the findings described. Confirmatory lab tests are not readily available. The organism is infrequently recovered in cultures of specimens from suspected wounds (30% of cases).10,11 Serologic testing on specimens drawn before administration of tetanus immunoglobulin (TIG) may indicate very low or undetectable antitetanus antibody levels, but tetanus can still occur when “protective” levels of antibodies are present.11 Detection of tetanus toxin in plasma or a wound with bioassays and polymerase chain reaction might be possible, but these tests are only available in a few settings.3
THE MULTIFACETED CARE PLAN
The primary care provider should refer a patient with suspected tetanus to an emergency department, preferably a tertiary care center with the necessary specialists. Patients are likely to require prolonged hospitalization. In a recent series of tetanus cases in California, the median length of hospitalization was 18 days.12 Treatment is multifaceted; interventions include immunization, wound care, administration of antibiotics and other pharmacologic agents, and supportive therapy (see Table 3).
Immunization
All patients with suspected tetanus should immediately receive both passive (with TIG) and active (tetanus toxoid–containing vaccines) immunization. Because of the extremely high potency of tetanus toxin, the very small amount of toxin that is required to cause tetanus is insufficient to prompt an immune response that would confer immunity. Therefore, treatment is the same regardless of whether the patient had prior disease.10
TIG binds to and neutralizes unbound tetanospasmin, preventing progression of the disease. As noted, TIG will not reverse the binding of the toxin to nerve structures.5 Due to a lack of prospective studies, there is disagreement regarding TIG dosage: Doses as high as 3,000-6,000 U have been recommended, but case studies indicate that the dosage recommended by the CDC (500 U) is likely effective.13 The full CDC recommendation is 500 U of human-derived TIG intramuscularly administered at locations near and away from the wound (but always away from the tetanus toxoid injection site).10,17 Outside the US, equine-based TIG may be the only option. Animal-derived TIG is less desirable because of increased allergy risk; when used, a small amount (0.1 mL) should be first administered as an intradermal test.17
Tetanus toxoid immunization produces active immunity. It is currently available in combination antigen forms (tetanus and diphtheria vaccine [Td], tetanus-diphtheria-acellular pertussis [Tdap] vaccine). The dose of either is 0.5 mL. Patients with tetanus should receive three doses given intramuscularly: immediately, at 4 weeks, and at 6 to 12 months.10
Wound care
Wound care should include incision and drainage, removal of foreign bodies, debridement, and irrigation. These steps are taken in order to ensure an aerobic environment in the wound, ultimately decreasing C tetani survival.1
Antibiotics
The preferred antimicrobial agent for treating tetanus infection is metronidazole 500 mg intravenously (IV) every 6 hours.1,3,17 Penicillin (2 to 4 million U IV every 4 to 6 hours) is effective against C tetani, but it is a GABA-receptor antagonist and may worsen tetanus by further inhibiting the release of GABA.1,14,18 GABA-receptor antagonism may also occur with cephalosporins; however, these broader-spectrum agents may be necessary to treat mixed infections.17 Alternatives include doxycycline, macrolides, and clindamycin.1
Other pharmacologic treatment
Benzodiazepines (eg, diazepam 10 to 30 mg IV) can help control rigidity and muscle spasms and are a mainstay of tetanus treatment.18 Benzodiazepines and propofol both act on GABA receptors, producing sedation in addition to controlling muscle spasms.19 Traditionally, more severe spasms, such as opisthotonus, have required induction of complete paralysis with nondepolarizing paralytics, such as pancuronium or vecuronium. However, paralysis is not optimal therapy since it necessitates sedation, intubation, and mechanical ventilation. Because tetanus does not resolve for 6 to 8 weeks, patients who require mechanical ventilation will also require tracheostomy to prevent laryngotracheal stenosis. Paralysis and mechanical ventilation can also lead to deep venous thrombosis, decubitus ulcers, and pneumonia.5 The ideal treatment would reduce the spasms and autonomic instability without the risks associated with deep sedation and paralysis.5
Other agents used in the treatment of tetanus include magnesium sulfate, which can decrease muscle spasm and ameliorate the effects of autonomic dysfunction, and intrathecal baclofen, which can decrease muscle spasm.19,20 Patients with persistent autonomic dysfunction may require combined α- and ß-adrenergic receptor blockade.1,17-20
Supportive care
It is important to implement supportive care, including limiting auditory and tactile stimulation, as well as providing adequate hydration and nutritional support. IV fluids, parenteral feeding, and enteral feeding are required. Measures should be taken to prevent complications of prolonged immobility, paralysis, and mechanical ventilation, including deep venous thrombosis, pulmonary embolism, and pressure ulcers. The quality of supportive care and the swiftness with which the diagnosis is made and appropriate treatment is initiated are key factors that determine an individual patient’s outcome.21
