Introduction Bordetella pertussis infection in non-immune (NI) infants is known to provoke three different syndromes requiring intensive care unit (ICU) admission: (1) severe apnoeic/bradycardic pertussis (SAP); (2) pneumo-pertussis (PNP) and (3) malignant pertussis (MP) that associates acute respiratory distress syndrome (ARDS), pulmonary hypertension, heart failure and multiple organ failure. Although mortality is known to be higher in patients with MP, little is known on the clinical and biochemical characteristics of the three forms, and ICU outcomes.

Methods Retrospective analysis of all NI infants admitted in a tertiary paediatric ICU for severe B pertussis confirmed infection during a 10-year period.

Results 48 patients were admitted. 29 patients had SAP. Among the 19 patients who developed ARDS, eight subsequently developed MP. PRISM II and PELOD scores, as well as on admission, paediatric heart failure score, total blood leucocytes and thrombocytes were significantly higher in patients with PNP and MP than in SAP. Glasgow coma scale score and serum natraemia were significantly lowered in the two most severe forms. Both respiratory distress syndrome and hypoxaemia on admission were more frequently encountered in PNP and MP than in SAP patients. On admission, hypoxaemia was the only clinical characteristic differentiating MP from PNP. Median ICU length of stay was 8 days in SAP and 12 days in PNP. No death occurred in SAP and PNP patients; whereas mortality was 62.5% in PM. Death occurs in a median 3 days delay.

Conclusion The three clinical forms are fairly distinguishable. The occurrence of hypoxaemia on admission is related to the most severe form.