(P-TS-93) Pertussis-Associated Hyperleukocytosis Treated Successfully with Whole Blood Exchange Transfusion in Two Neonates: A New Use for an Old Procedure?

Background/Case Studies: Pertussis, or whooping cough, is a highly contagious respiratory infection caused by the bacterium Bordatella pertussis. In 2022, the WHO reported over 64,000 cases globally. Although it is a vaccine-preventable disease, there has been increasing incidence in the US over the past two decades. Pertussis in neonates and young infants can be associated with elevated WBC counts, pulmonary hypertension, and hypoxemia. WBC counts over 100,000, may increase adverse outcomes and mortality. Leukodepletion utilizing apheresis is categorized by the American Society for Apheresis (ASFA) as a category III indication when associated with acute leukemia but for infants weighing < 10 kg a manual whole blood exchange (MWBE) is recommended. Using the same thought process, MWBE was utilized in two neonatal cases of symptomatic hyperleukocytosis associated with pertussis at our large, tertiary pediatric hospital.

Study

Design/Methods: Patient #1: a 2 month full-term, previously healthy female admitted for acute hypoxic respiratory failure (AHRF) with desaturations to 78% started on high flow nasal cannula at 10L 30% FiO2. CBC showed leukocytosis of 49.9 x10³/µL. On hospital day 3, respiratory array PCR was positive for RSV and B. pertussis. Azithromycin was started but due to uptrending leukocytosis and clinical deterioration, patient was transferred to PICU. On hospital day 6 WBC count was 107.7 x10³/µL. Apheresis service was consulted for leukodepletion following clinical decision to intubate. Decision to proceed with MWBE was made due to patient’s size (< 10kg).

Patient #2: a 22 day old full-term, previously healthy female admitted to PICU with AHRF, positive for B. pertussis, adenovirus, and rhino/enterovirus. Upon admission WBC count was 53.6 x 10³/µL. The patient was started on azithromycin but required intubation on day 1 of hospitalization. Due to escalating respiratory needs and uptrending WBC count, MWBE was performed due to patient size of < 5 kg.

Results/Findings: Both patients had a clinically significant and sustained reduction in WBC counts following a single volume exchange transfusion with reconstituted WB. Patient #1 had a 71% decrease in WBC count (107.7 x 10³/µL to 30.8). Patient #2 had a 37% reduction (51.1 x10³/µL to 32.3). Patient #1 had an increase in hematocrit to 45.0% from 28.8% during MWBE thus the procedure was stopped following a single blood volume.

Conclusions: MWBE is a safe and effective procedure for lowering WBC count in patients with severe pertussis infections. MWBEs are typically performed in NICUs for patients with hyperbilirubinemia or concern for GALD (gestational alloimmune liver disease), however can be utilized outside the NICU for patients weighing less than 10 kg and symptomatic hyperleukocytosis. In our experience a single volume exchange is sufficient and tailoring the reconstituted WB hematocrit on a case-by-case basis is important to minimize polycythemia.