Introduction

Infection is a major cause of death in children with haematological malignancies following bone marrow or solid organ transplantation, iatrogenic immunosuppression, and chemotherapy. The major factor predisposing to infection in these patients is neutropenia, which is defined as decreased circulating neutrophils in the peripheral blood. The normal reference range for neutrophil counts varies with the age of the child, being highest in the neonatal period. In infants, the normal threshold is 1000 neutrophils per mL; the usual value is 1500 neutrophils per mL up to 10 years of age, with an adult threshold of 1800 neutrophils per mL applied thereafter.¹ Neutropenia is defined as ≤500 neutrophils per mL or an anticipated decline from 1000 to ≤500 neutrophils per mL. Infection risk increases when the neutrophil count is ≤500 neutrophils per mL and is highest when ≤100 neutrophils per mL. Febrile neutropenia requires an associated fever ≥38.3°C, or ≥38.0°C for at least 1 hour.² This chapter focuses on neutropenia associated with paediatric cancer or its treatment as this is the more frequent type encountered in the emergency department (ED).

Neutropenic children receiving chemotherapy for leukaemia or undergoing bone-marrow transplantation (BMT) are at significant risk from Gram-negative sepsis, including Pseudomonas aeruginosa and Escherichia coli. In BMT patients, half the infections are bacterial, evenly split between Gram-positives (such as Staphylococcus aureus) and Gram-negative organisms; 40% are due to viruses like cytomegalovirus; and 10% due to fungi, with up to a third of episodes due to systemic fungaemia being life threatening.¹ Vascular catheter-related infections are usually related to Gram-positive skin organisms. Although the overall mortality rate due to neutropenia-associated infection is 1%, children undergoing BMT with febrile neutropenia have a startling mortality up to 80%.¹

Management priorities are:

Presentation

Young children compensate for impending shock and remain normotensive in the early stages of systemic sepsis. The earliest reliable sign of vascular redistribution is delayed capillary return, because tachycardia and tachypnoea can be secondary to the fever. Neutropenic or immunosuppressed children may have attenuated or altered signs of infection. The absence of neutrophils to localise an infection makes it difficult to determine the source of infection by physical examination alone. Pay special attention to body regions vulnerable to bacterial infection, such as oropharynx, ears, skin, and perianal area. Evidence of respiratory, circulatory, renal, and metabolic derangement indicates severe sepsis.