Too Small for Apheresis: When Technology Meets Physiology in Neonatal Patients

The patient was a premature infant, six weeks old and just 2.5 kilograms, already on ECMO for primary cardiopulmonary failure. Sepsis developed secondarily, and the critical-care team requested plasmapheresis for a presumed cytokine storm — a Category III indication under the current ASFA guidelines.

On paper, the rationale made sense. But when I calculated the total blood volume — only 250 mL (≈ 100 mL/kg for a premature infant) — it was immediately clear this baby was too small for the machine. The Terumo technical support representative confirmed the following minimum specifications for therapeutic plasma exchange:

• 30 cm: Minimum height the system can accept

• 2 kg: Minimum weight the system can accept

• 300 mL: Minimum total blood volume (manual entry)

• 10 %: Minimum hematocrit

• 0.5 L: Minimum plasma volume (machine default = 1.0 L)

• 25 kg: Minimum weight for automatic TBV calculation

  
  

Despite meeting the weight requirement, the patient’s total blood volume was below the system’s operational threshold. The procedure was simply not possible.

After discussing options with the ICU team, we recommended whole blood exchange instead — a technically feasible alternative that allowed for cytokine and toxin removal within the constraints of neonatal physiology.

This case underscored an important reality: sometimes the limits we face are not physiologic but mechanical. Even when a treatment is conceptually justified, our instruments may not yet be scaled to our smallest and most fragile patients. Until apheresis technology evolves to meet neonatal demands, these moments will remain a quiet reminder that innovation in transfusion medicine isn’t only about what we can do — it’s also about who we can safely do it for.