U.S. Army Institute of Surgical Research JBSA-FT Sam Houston, Texas, United States
Background/Case Studies: While cryopreservation of blood products extends the shelf life, there are associated requirements for frozen cold chain management and thawing before use. ZipThaw (FreMon Scientific, La Jolla, CA) is designed to precisely and uniformly thaw frozen plasma to near body temperatures in a dry environment. This study sought to measure relevant clinically significant changes when using the plasma thawer on cryopreserved red cells, specifically if hemolysis was increased due to acute exposure to the thawing device.
Study
Design/Methods: Testing was conducted in 31 packed frozen RBC (fRBC) units, glycerolized and frozen by ACP 215 method (Haemonetics, Boston, MA), with a minimum volume of 300 mL. Prior to each unit’s evaluation, segments from the collection line were isolated and removed to use as matched controls for thawing in standard blood bank water bath. The fRBC units were loaded into the dry plasma thawer and exposed to the “Thaw” setting, incubated between cushions at 37 ºC with massaging agitation until device registers a temperature of 31 ºC. Post thaw-cycle, the units were left inside the device until the onboard temperature monitor indicated that the unit had reached 33 ºC. Complete blood counts were run on both main unit and segments with a DxH 520 (Beckman Coulter, Brea, CA) to analyze hematocrit (%HCT) and total hemoglobin (tHGB). Remaining sample was centrifuged (Thermo Scientific, Waltham, MA, Legend Micro 21 model) at 2500 × g for 15 minutes to produce cell free plasma, which was then tested on a Plasma/Low Hb System (HemoCue, Angelholm, Sweden) for plasma free hemoglobin (fHGB). Percent hemolysis was calculated with the equation: ((100−%𝐻𝐶𝑇)∗𝑓𝐻𝐺𝐵)/𝑡𝐻𝐺𝐵.
Results/Findings: Using the dry thawer, fHBG was lower in 23 of 31 samples, and hemolysis was lower in 19 of 31 samples. Pairwise comparisons showed median fHBG was 750 mg/dL in the dry thawer vs. 880 mg/dL in water bath (p = .0065), and median hemolysis was 1.39% in the dry thawer vs. 2.02% (p = .0016). Conclusions: The results of the study demonstrate that the dry plasma thawing method used for fRBCs does not cause additional hemolysis versus traditional water bath. The matched sample comparison showed that free hemoglobin and the calculated hemolysis levels were at least equivalent in this 31-sample cohort. Additionally, in all cases, hemolysis was low enough for routine clearance by standard de-glycerolization / washing protocols to achieve an expected post-processing hemolysis of less than 1% in the final product.
