The effects of cryopreserved red blood cell transfusion on tissue oxygenation in obese trauma patients

The effect of perturbations of the glycocalyx on microvascular perfusion in the obese trauma population: an in vitro study

Objectives

Patients with morbid obesity have impaired responses to resuscitation following severe injury, which may contribute to adverse outcomes. Obesity is associated with microvascular dysfunction and metabolic changes associated with altered hemorheological profiles. These include decreased red blood cell (RBC) deformity associated with increased aggregation and adhesion. These RBC changes may be impacted by the glycocalyx layer of the endothelial cell (EC) and RBC. Degradation of either or both glycocalyx layers may impair microvascular perfusion. This was studied from blood obtained from patients with obesity and in an in vitro microfluidic device to mimic the microvascular environment.

Methods

RBCs were obtained from fresh whole blood from normal controls and patients with obesity (body mass index 37.6–60.0). RBC glycocalyx was indexed by fluorescent intensity and shedding of EC glycocalyx components into the serum was determined by measurement of syndecan-1 and hyaluronic acid. In a second set of experiments, human umbilical vein endothelial cell monolayers (HUVEC) were perfused with RBC suspensions from control and patients with obesity using a microfluidic device and RBC adherence under normoxic or shock conditions (hypoxia+epinephrine) was determined using confocal microscopy. HUVEC glycocalyx thickness and shedding were also measured.

Results

Microfluidic studies demonstrated that RBC obtained from subjects with obesity had increased adhesion to the endothelial layer, which was more profound under shock conditions versus normal subjects. This appeared to be related to increased shedding of the endothelial glycocalyx following shock as well as a diminished RBC glycocalyx layer in the obese population.

Conclusion

Blood from patients with obesity have decreased RBC glycocalyx thickness accompanied by evidence of increased EC glycocalyx shedding. In vitro adhesion to the endothelium was more pronounced with RBC from patients with obesity and was significantly greater under ‘shock conditions’. Hemorheological properties of RBC from patients with obesity may account for failure of standard resuscitation procedures in the trauma patient.

Level of evidence

Frozen Blood Reserves

Frozen blood reserves are an important component in meeting blood needs. The idea behind a frozen blood reserve is twofold: to freeze units of rare blood types for later use by patients with special transfusion needs and for managing special transfusion circumstances. The permeating additive glycerol is used as a cryoprotectant to protect red blood cells (RBCs) from freezing damage. The use of thawed RBCs has been hampered by a 24-h outdating period due to the potential bacterial contamination when a functionally open system is used for addition and removal of the glycerol. The introduction of an automated, functionally closed system for glycerolization and deglycerolization of RBCs improved the operational practice. More importantly, the closed process allowed for extended shelf life of the thawed RBCs. In the current chapter, a cryopreservation procedure for RBCs using a functionally closed processing system is described.