Pertussis

Overview

  • Critical pertussis (pertussis infection requiring intensive care) typically most commonly seen in young infants. In those <4 months, pertussis is often most severe and can be fatal
  • Infants can present with bronchopneumonia or apnea, with paroxysmal coughing and post-tussive emesis less commonly seen

Figure 1: Typical Timeline of Pertussis Infection (from cdc.gov)

  • Fulminant pertussis often involves leukocytosis and pulmonary hypertension
  • ELSO registry review from 1992-2009 of 169 cases demonstrates a mortality rate of 69.8% for those with pertussis requiring ECMO. This increases to 83.6% mortality for those younger than 6 weeks requiring ECMO
  • WBC >100K associated with 100% mortality via conventional treatment

Pathophysiology

  • Leukocytosis is theorized to produce hyperviscosity and pulmonary arteriolar thrombosis, leading to pulmonary hypertension
Figure 2: Pathogenesis of Pertussis


Treatment

  • Isolation: Droplet precautions until 5 days of effective therapy (or three weeks after onset of symptoms in untreated patients)
  • Antibiotics: Macrolides are treatment of choice:
    • >6 months of age: Azithromycin or Clarithromycin for a 5  and 7 day course, respectively. TMP-SMX 14 day course as an alternative for those who cannot tolerate macrolide therapy
    • <6 months of age: Azithromycin is the recommended agent (although can be associated with hypertrophic pyloric stenosis in infants <2 weeks of age). TMP-SMX as an alternative for those >2 months and cannot tolerate macrolides (do not use in <2 months due to risk of kernicterus secondary to bilirubin displacement)
    • Postexposure prophyalxis for all contacts (full dosing treatment course): within 21 days of onset of cough for index case, prophylaxis can prevent development of symptoms. The American Academy of Pediatrics (AAP) recommends antimicrobial prophylaxis for all close contacts, such as child care workers or household members, regardless of their immunization status (RedBook, 2012 Report of the Committee on Infectious Diseases, 29th, Pickering LK. (Ed), American Academy of Pediatrics)
  • Echocardiography to evaluate for pulmonary hypertension
  • No clear evidence supporting use of bronchodilators, corticosteroids, Pertussis immunoglobulin
  • ECMO: mortality for young infants requiring ECMO is high (69.8% overall and 83.6% for infants <6 weeks) but VV ECMO may be required for refractory hypoxemia and pulmonary hypertension
  • Leukodepletion: via exchange transfusion or a leukofilter on an ECMO circuit, can reduce the WBC burden and presumably, the pulmonary arteriole aggregates. When compared to historical controls, leukodepletion for patients on ECMO seems to confer a survival benefit. (Rowlands, Pediatrics 2010). No clear cutoff although WBC of 50K and 30K (for patients on ECMO) has been described in infants <90 days of age. See figure below. 
Figure 3: Proposed Algorithm for Leukeodepletion in Pertussis, from: Rowlands et al, Pediatrics 2010



References

1) Rowlands HE, Goldman AP, Harrington K, Karimova A, Brierley J, Cross N,Skellett S, Peters MJ. Impact of rapid leukodepletion on the outcome of severeclinical pertussis in young infants. Pediatrics. 2010 Oct;126(4):e816-27. doi:10.1542/peds.2009-2860. Epub 2010 Sep 6. PubMed PMID: 20819895.