This study aims to evaluate the clinical course of critical pertussis illness to the pediatric intensive care unit in Istanbul. The study was conducted as a multicenter, retrospective study between January 1, 2023, and December 31, 2023. Cases with positive polymerase chain reaction testing for Bordetella pertussis of nasopharyngeal swab samples within the first 24 h of pediatric intensive care unit admission were recorded. We divided the patients into exchange blood transfusion group and non-exchange blood transfusion group, comparing related factors and clinical characteristics among each group. A total of 50 children with severe pertussis were enrolled in the study, including 29 males (58%), with a median age of 9.14 weeks (range, 7.29–15.3 weeks). The mortality rate for severe pertussis was 8%. Exchange blood transfusion was performed in eight patients (16%). There were no significant differences between patients who received exchange blood transfusion and those who did not in terms of age, male gender, gestational age, birth weight, comorbidities, presenting symptoms, duration of cough, prior antibiotic use, vaccination status, coinfections, PICU length of stay, or mortality (p > 0.05). Children who underwent exchange blood transfusion had significantly higher white blood cell (WBC) counts, lymphocyte counts, neutrophil counts, and C-reactive protein (CRP) levels compared to those who did not receive the procedure (p < 0.05). Pulmonary hypertension was observed in 50% of the children who received exchange blood transfusion, while it was present in only 11.8% of those who did not undergo the procedure (p < 0.05). Additionally, patients who received exchange blood transfusion had higher incidences of respiratory failure, cardiac failure or arrest, inotrope requirement, and mechanical ventilation compared to those who did not receive the transfusion (p < 0.05). Conclusions: Pertussis can lead to severe complications and mortality in critically ill infants. Most severe pertussis occurred in young, unimmunized infants. Children admitted with pertussis with high CRP level, high WBC and lymphocyte, and cardiac and respiratory failure can need exchange blood transfusion.

What is Known:

• Pertussis is a highly contagious respiratory infection caused by Bordetella pertussis, which primarily affects infants. Despite vaccination efforts, pertussis remains a significant cause of morbidity and mortality in infants, particularly those too young to be fully vaccinated.

What is New:

• In pertussis, exchange blood transfusion may be considered in cases of severe pulmonary hypertension or cardiogenic shock, as indicated by echocardiographic findings, in conjunction with leukocytosis observed on laboratory tests.