Prognosis
The case fatality rate is 12% to 53%.[81] In settings with facilities for mechanical ventilation, the most common causes of death are autonomic dysfunction and hospital-acquired pneumonia. Where facilities do not allow for mechanical ventilation, the most common cause of death is asphyxia, resulting from laryngeal spasm, respiratory muscle spasm, or extreme fatigue.[12]
Prompt diagnosis and prediction of severity are vital in order to determine timely management, including transfer to an intensive care unit and early airway protection. This pre-empts the life-threatening complications of severe disease.
Predictors of severe disease and therefore worse outcome are as follows:
Incubation period (time from injury to first symptom) is inversely related to disease severity. An incubation period of less than 7 days is said to predict grade 3b disease.[45]
Onset period (time from first symptom to first spasm) is also inversely related to disease severity.
Site of infection: umbilical, uterine, head, and neck predict more severe disease.
Intramuscular quinine injections are reported to carry a mortality of 96%.[24] Heroin is often 'cut' or diluted with quinine, and this may contribute to the high mortality described in drug addicts with tetanus.[52]
Co-morbidity.
Extremes of age.[2]
Autonomic dysfunction.
Lack of immunity. Previous immunisation, even if incomplete, is associated with milder disease.[2]
Various groups have devised scoring systems to determine prognosis in tetanus. The Phillips score provides a severity index based on the incubation period, site of infection, state of immunity, and complicating factors.[82] The Dakar score assesses incubation period, onset period, site of injury, and presence of spasms, fever, and tachycardia on admission.[83] In a study of 500 consecutive patients (non-neonates) admitted to the Tetanus Unit at the Hospital for Tropical Diseases (HTD) in Ho Chi Minh City, Vietnam, between May 1997 and February 1999, a Dakar score of 3 or greater was associated with a 59% mortality compared with 14% mortality for patients with a Dakar score less than 3. Those with a Phillips score of 17 or greater had a mortality of 34% compared with 11% in the group with a Phillips score less than 17.
A tetanus severity score has been devised using prospectively acquired data from consecutive patients admitted to the HTD with multivariate logistic regression.[81] The authors compared their new score with the Phillips and Dakar scores, which were published in the 1960s/1970s without validation data. Their tetanus severity score had a sensitivity of 77% and a specificity of 82% for a fatal outcome when tested with re-substituted data and showed significantly better discrimination between survivors and non-survivors than the Dakar or Phillips scores.
In neonatal tetanus - age less than 10 days - an incubation period of 6 days or less, the presence of risus sardonicus, opisthotonus, fever, and weight less than 2.5 kg, indicate a poor prognosis and high risk of death.[84][85][86][Figure caption and citation for the preceding image starts]: Tetanus severity score. The final score is calculated from the sum of the scores for each section. A total of 8 or greater indicates predicted death; less than 8 indicates predicted survivalFrom Thwaites CL, Yen LM, Glover C, et al. Predicting the clinical outcome of tetanus: the tetanus severity score. Trop Med Int Health. 2006;11:279-287 [Citation ends].
One study of 107 cases of neonatal tetanus in Vietnam confirmed the association of young age and lower weight with a poor outcome, and that a delay in hospital admission and presence of leukocytosis are significant additional factors.[87]
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