(P-TA-21) To Prime or Not to Prime? Decreasing Blood Exposure to Pediatric Patients During Therapeutic Plasma Exchange

Background/Case Studies: Therapeutic Plasma Exchange (TPE) is frequently used in pediatric patients with autoimmune or inflammatory diseases. However, low patient weight or hematocrit poses challenges due to the extracorporeal volume (ECV) required, increasing the risk of hypovolemia. Manufacturer guidelines suggest red blood cell (RBC) priming if the ECV exceeds 10–15% of the patient’s total blood volume (TBV). While RBC priming mitigates volume shifts, it introduces additional risks—transfusion reactions, infection, and increased cost. This study explores whether partial prime or no prime could serve as a safe and effective alternative to a full prime for pediatric patients with an ECV of 10–15% of TBV.

Study

Design/Methods: We retrospectively reviewed TPE procedures at Children’s Hospital Los Angeles between 2023–2025. Patient demographics (age, weight, height), number of TPE sessions, prime volume (if any), and adverse event data were collected. TBV was calculated using Nadler’s Equation. A standard procedure was considered as ECV < 10%, or where a full prime was used. We focused on patients whose ECV constituted 10–15% of their TBV. A full prime was defined as 225 mL of RBCs (standard circuit volume); partial prime was ≤150 mL. Safety was defined as: 1) stable vital signs without intervention, and 2) absence of hypovolemia symptoms (e.g., dizziness, pallor, fatigue).

Results/Findings: Among 385 TPE procedures performed in 54 patients, 58 procedures (15%) involved 10 patients with ECVs in the 10–15% range and received either no prime (n=39) or partial prime (n=19) (Figure A). All 10 patients in this group tolerated TPE well. Only one event of mild hypotension was recorded, requiring reduced flow rate but no additional intervention. No other vital sign instability or hypovolemic symptoms were observed in any case.

Conclusions: Our data suggest that in selected pediatric patients with ECV between 10–15% of TBV, omitting or reducing the RBC prime volume can be safe and effective under close monitoring and physician discretion. A single, self-limited hypotensive episode supports the feasibility of this practice. While this study supports the principle of blood product minimization in pediatric TPE, it was limited by lack of consistent post-procedural labs to draw further conclusions. Future prospective studies should explore clinical outcomes, post-procedural labs, and long-term effects of modified priming strategies.