# Osmotic Fragility in Leukodepleted Stored Red Blood Cells: Implications for Neurocritical Care Transfusion Strategies

## TL;DR

Stored red blood cells become more fragile and release more free hemoglobin over time, which could affect their effectiveness in treating anemia in brain injury patients.

## Contribution

This study shows that storage duration impacts red blood cell stability and hemolysis in a clinically relevant timeframe.

## Key findings

- Osmotic fragility increased significantly after 28 days of storage.
- Free hemoglobin levels rose progressively with longer storage duration.
- Hemolysis increased slightly but remained below the 0.8% threshold.

## Abstract

Background: Anemia is frequent in critically ill patients with traumatic brain injury (TBI) and worsens neurological outcomes. Red blood cell (RBC) transfusion is a cornerstone of management, but storage-related biochemical and structural changes may impair oxygen delivery. This study examined the effect of storage duration on osmotic fragility (OF) and free hemoglobin (fHb) in leukodepleted packed RBCs (pRBCs) as indicators of membrane stability and hemolysis. Methods: Twenty-four leukodepleted pRBC units in SAGM (saline, adenine, glucose, and mannitol) solution were analyzed from Day 3 to Day 42. OF was assessed by Beutler’s method with H50 values derived from logistic models, and fHb was quantified spectrophotometrically. Flow cytometry with phosphate-buffered saline (PBS)-induced osmotic stress provided complementary OF data. Results: OF increased significantly beyond 28 days, with Week 6 H50 values exceeding those at Weeks 2 and 4 (p < 0.0001). fHb rose progressively with storage: 7.3 ± 4.3 µmol/L (Week 2), 14.6 ± 7.9 (Week 4), and 25.7 ± 12.1 (Week 6) (p < 0.0001). Hemolysis remained below the 0.8% threshold but increased from 0.09% to 0.29% (p < 0.0001). Conclusions: pRBC storage beyond 28 days leads to greater OF and fHb release, reflecting reduced membrane stability. These changes may compromise transfusion efficacy and oxygen delivery in neurocritical care.