Swärd-Nilsson A-M, Persson P-O, Johnson U, Lethagen S
Blood Centre, University Hospital Lund, Sweden.
Vox Sang. 2006 Jan;90(1):33-9. doi: 10.1111/j.1423-0410.2005.00715.x.
Fresh frozen human plasma is an important raw material in the production of coagulation factor concentrates used in patients with haemorrhagic disorders. The aim of the study was to determine how the handling of plasma influences the recovery of coagulation factor VIII activity (FVIII:C), i.e. the influence of time between donation and freezing, of the freezing time and of the ice front velocity. We also studied a tentative eutectic point in human plasma.
Aliquots of plasma from 12 different donors were kept at room temperature for 2, 4 and 6 h before start of freezing. We achieved fast freezing with a freezer that blows cooled air at a high velocity on the plasma containers. Freezing times were 0.5, 1, 4 and 24 h. Temperature was registered continuously during freezing. Plasma and NaCl solutions were frozen slowly to investigate the eutectic point.
Storage at room temperature for 6 h caused a small but statistically significant decrease in FVIII:C. Slow freezing with programmed freezing times of 4 and 24 h caused a more pronounced drop in FVIII:C as compared to that of 30 and 60 min. We found no eutectic point in plasma or in plasma with addition of 2 % (w/v) NaCl.
For an optimal yield of FVIII, freezing should start within 4 h after plasma donation. We propose the use of the term 'ice front velocity' instead of 'freezing speed', taking into consideration that the volume and shape of plasma containers may differ. We found only a marginal loss of FVIII:C when the ice front velocity was 26 mm/h or faster, but a significant loss when it was 9 mm/h or slower. We recommend freezing times of 60 min or shorter. We were not able to demonstrate any eutectic point in human plasma. We therefore recommend that the term eutectic point should not be used as a reference temperature in guidelines on plasma handling.
新鲜冷冻人血浆是生产用于出血性疾病患者的凝血因子浓缩物的重要原料。本研究的目的是确定血浆的处理方式如何影响凝血因子VIII活性（FVIII:C）的回收率，即献血与冷冻之间的时间、冷冻时间和冰前沿速度的影响。我们还研究了人血浆中的一个暂定共晶点。
来自12名不同献血者的血浆等分试样在开始冷冻前分别在室温下保存2、4和6小时。我们使用一台向血浆容器高速吹送冷空气的冷冻机实现快速冷冻。冷冻时间分别为0.5、1、4和24小时。冷冻过程中持续记录温度。将血浆和氯化钠溶液缓慢冷冻以研究共晶点。
在室温下保存6小时导致FVIII:C有轻微但具有统计学意义的下降。与30分钟和60分钟相比，程序冷冻时间为4小时和24小时的缓慢冷冻导致FVIII:C下降更为明显。我们在血浆或添加2%（w/v）氯化钠的血浆中未发现共晶点。
为了获得最佳的FVIII产量，应在血浆捐献后4小时内开始冷冻。考虑到血浆容器的体积和形状可能不同，我们建议使用“冰前沿速度”而非“冷冻速度”这一术语。当冰前沿速度为26毫米/小时或更快时，我们发现FVIII:C仅有少量损失，但当冰前沿速度为9毫米/小时或更慢时则有显著损失。我们建议冷冻时间为60分钟或更短。我们未能在人血浆中证明任何共晶点。因此，我们建议在血浆处理指南中不应将共晶点用作参考温度。
