Activation of the complement system by different autologous transfusion devices: an in vitro study

Hemolytic reaction in the washed salvaged blood of a patient with paroxysmal nocturnal hemoglobinuria

Background

In patients with paroxysmal nocturnal hemoglobinuria (PNH), the membrane-attack complex (MAC) formed on red blood cells (RBCs) causes hemolysis due to the patient’s own activated complement system by an infection, inflammation, or surgical stress. The efficacy of transfusion therapy for patients with PNH has been documented, but no studies have focused on the perioperative use of salvaged autologous blood in patients with PNH.

Case presentation

A 71-year-old man underwent total hip replacement surgery. An autologous blood salvage device was put in place due to the large bleeding volume and the existence of an irregular antibody. The potassium concentration in the transfer bag of salvaged RBCs after the wash process was high at 6.2 mmol/L, although the washing generally removes > 90% of the potassium from the blood. This may have been caused by continued hemolysis even after the wash process. Once activated, the complement in patients with PNH forms the MAC on the RBCs, and the hemolytic reaction may not be stopped even with RBC washing.

Conclusions

Packed RBCs, instead of salvaged autologous RBCs, should be used for transfusions in patients with PNH. The use of salvaged autologous RBCs in patients with PNH should be limited to critical situations, such as massive bleeding. Physicians should note that the hemolytic reaction may be present inside the transfer bag even after the wash process.

Effect of Perfusion Fluids on Recovery of Inflammatory Mediators in Microdialysis

Microdialysis is an excellent tool to assess tissue inflammation in patients, but in vitro systems to evaluate recovery of inflammatory mediators have not been standardized. We aimed to develop a reference plasma preparation and evaluate different perfusion fluids with respect to recovery of metabolic and inflammatory markers. The reference preparation was produced by incubation of human blood with lipopolysaccharide and cobra venom factor to generate cytokines and activate complement, respectively. Microdialysis with 100 kDa catheters was performed using different colloid and crystalloid perfusion fluids (hydroxyethyl starch (HES) 130/0.4, HES 200/0.5, hyperosmolar HES 200/0.5, albumin 200 g/l, T1 perfusion fluid and Ringer's acetate) compared to today's recommended dextran 60 solution. Recovery of glucose, glycerol and pyruvate was not significantly different between the perfusion fluids, whereas lactate had lower recovery in HES 200/0.5 and albumin perfusion fluids. Recovery rates for the inflammatory proteins in comparison with the concentration in the reference preparation differed substantially: IL-6 = 9%, IL-1β = 18%, TNF = 0.3%, MCP-1 = 45%, IL-8 = 48%, MIG = 48%, IP-10 = 25%, C3a = 53% and C5a = 12%. IL-10 was not detectable in microdialysis dialysate. HES 130/0.4 and HES 200/0.5 yielded a recovery not significantly different from dextran 60. Hyperosmolar HES 200/0.5 and albumin showed significantly different pattern of recovery with increased concentration of MIG, IP-10, C3a and C5a and decreased concentration of IL-1β, TNF, MCP-1 and IL-8 in comparison with dextran 60. In conclusion, microdialysis perfusion fluid dextran 60 can be replaced by the commonly used HES 130/0.4, whereas albumin might be used if specific immunological variables are in focus. The present reference plasma preparation is suitable for in vitro evaluation of microdialysis systems.

Oxygen carrying capacity of salvaged blood in patients undergoing off-pump coronary artery bypass grafting surgery: a prospective observational study

BACKGROUND

Intraoperative cell salvage (ICS), hereby referred to 'mechanical red cell salvage', has been widely used and proven to be an effective way to reduce or avoid the need for allogeneic red blood cells (RBCs)transfusion and its associated complications in surgeries involving major blood loss. However, little is known about the influence of this technique on the functional state of salvaged RBCs. Furthermore, there are no articles that describe the change of free hemoglobin (fHb) in salvage blood during storage, which is a key index of the quality control of salvaged blood. Therefore, in this study, the influence of ICS on the function of salvaged RBCs and the changes of salvaged RBCs during storage were studied with respect to the presence of oxyhemoglobin affinity (recorded as a P50 value) and the level of 2, 3-diphosphoglycerate (2, 3-DPG) and fHb by comparing salvaged RBCs with self-venous RBCs and 2-week-old packed RBCs.

METHODS

Fifteen patients undergoing off-pump coronary artery bypass grafting (OPCAB) surgery were enrolled. Blood was collected and processed using a Dideco Electa device. The level of P50, 2, 3-DPG and fHB from salvaged RBCs, venous RBCs and 2-week-old packed RBCs was measured. We also measured the changes of these indicators among salvaged RBCs at 4 h (storage at 21-24 °C) and at 24 h (storage at 1-6 °C).

RESULTS

The P50 value of salvaged RBCs at 0 h (28.77 ± 0.27 mmHg) was significantly higher than the value of venous RBCs (27.07 ± 0.23 mmHg, p=0.000) and the value of the 2-week-old packed RBCs (16.26 ± 0.62 mmHg, p=0.000). P50 value did not change obviously at 4 h (p=0.121) and 24 h (p=0.384) compared with the value at 0 h. The 2, 3-DPG value of salvaged RBCs at 0 h (17.94 ± 6.91 μmol/g Hb) was significantly higher than the value of venous RBCs (12.73 ± 6.52 mmHg, p = 0.007) and the value of the 2-week-old packed RBCs (2.62 ± 3.13 mmHg, p=0.000). The level of 2, 3-DPG slightly decreased at 4 h (p=0.380) and 24 h (p=0.425) compared with the value at 0 h. Percentage of hemolysis of the salvaged blood at 0 h(0.51 ± 0.27 %) was significantly higher than the level of venous blood (0.07 ± 0.05 %, p=0.000) and the value of 2-week-old packed RBCs (0.07 ± 0.05 %, p=0.000), and reached 1.11 ± 0.42 % at 4 h (p=0.002) and 1.83 ± 0.77 % at 24 h (p=0.000).

CONCLUSIONS

The oxygen transport function of salvaged RBCs at 0 h was not influenced by the cell salvage process and was better than that of the venous RBCs and 2-week-old packed RBCs. At the end of storage, the oxygen transport function of salvaged RBCs did not change obviously, but percentage of hemolysis significantly increased.

Cell culture model that mimics drusen formation and triggers complement activation associated with age-related macular degeneration

We introduce a human retinal pigmented epithelial (RPE) cell-culture model that mimics several key aspects of early stage age-related macular degeneration (AMD). These include accumulation of sub-RPE deposits that contain molecular constituents of human drusen, and activation of complement leading to formation of deposit-associated terminal complement complexes. Abundant sub-RPE deposits that are rich in apolipoprotein E (APOE), a prominent drusen constituent, are formed by RPE cells grown on porous supports. Exposure to human serum results in selective, deposit-associated accumulation of additional known drusen components, including vitronectin, clusterin, and serum amyloid P, thus suggesting that specific protein-protein interactions contribute to the accretion of plasma proteins during drusen formation. Serum exposure also leads to complement activation, as evidenced by the generation of C5b-9 immunoreactive terminal complement complexes in association with APOE-containing deposits. Ultrastructural analyses reveal two morphologically distinct forms of deposits: One consisting of membrane-bounded multivesicular material, and the other of nonmembrane-bounded particle conglomerates. Collectively, these results suggest that drusen formation involves the accumulation of sub-RPE material rich in APOE, a prominent biosynthetic product of the RPE, which interacts with a select group of drusen-associated plasma proteins. Activation of the complement cascade appears to be mediated via the classical pathway by the binding of C1q to ligands in APOE-rich deposits, triggering direct activation of complement by C1q, deposition of terminal complement complexes and inflammatory sequelae. This model system will facilitate the analysis of molecular and cellular aspects of AMD pathogenesis, and the testing of new therapeutic agents for its treatment.

A novel in vitro model for preclinical testing of the hemocompatibility of intravascular stents according to ISO 10993-4

Subacute stent thrombosis, caused by undesired interactions between blood and the stent surface, is a major concern in the first few weeks following coronary artery stent implantation. The aim of this study was to establish a novel in vitro model for hemocompatibility testing of coronary artery stents according to ISO 10993-4. The model consists of a modified Chandler-Loop design with closed heparin-coated PVC Loops and a thermostated water bath. The tests were performed with anticoagulated human whole blood. After incubation in the loop, blood was analyzed for coagulation and inflammatory activation markers (TAT, β-TG, sP-selectin, SC5b-9 and PMN-elastase). Three different stent types with varying thrombogenicity were tested; statistically significant differences were found between the three stent types in measures of coagulation and platelet activation. The new Chandler-Loop model can be used as an alternative to animal and current in vitro models, especially for the determination of early events after stent implantation.

Is cell salvage safe in liver resection? A pilot study

STUDY OBJECTIVE

To investigate the quality of cell salvaged (CS) blood in patients undergoing hemihepatectomy (study group) and compare it with CS-blood from aortic surgery (control group).

DESIGN

Observational study.

SETTING

Operating room in a university hospital.

MEASUREMENTS

6 patients undergoing hemihepatectomy or aortobifemoral bypass with intraoperative blood loss of more than 800 mL. Samples were drawn from the central venous catheter, from the reservoir of a CS recovery system, and from the processed blood in each patient to determine interleukin (IL)-6, IL-8, IL-10, tumor necrosis factor (TNF), complement C3a, and the terminal complement complex C5b-9. Microbiological analysis included colony count after cultivation in aerobic and anaerobic medium as well as enrichment culture for 6 days.

MAIN RESULTS

In the hemihepatectomy group, levels of IL-6, C3a, and C5b-9 were significantly higher in the reservoir than in samples obtained from the central venous catheter. After the washing procedure, levels of IL-6, C3a, and C5b-9 were lower in the liver resection group than in each patient's own plasma levels. In all patients undergoing aortobifemoral bypass and in 5 patients undergoing hemihepatectomy, blood samples were sterile or showed growth of commensal skin microflora in low numbers (coagulase-negative staphylococci or propionibacteria). In one patient in the liver resection group, we could not exclude contamination with intestinal flora.

CONCLUSION

Cell salvaged blood in liver resection seems to be safe for retransfusion with respect to cytokine release and complement activation, but requires further investigation in regard to bacterial contamination.

Impact of heart valve decellularization on 3-D ultrastructure, immunogenicity and thrombogenicity

Decellularized xenogeneic tissue represents an interesting material for heart valve tissue engineering. The prospect objective is removal of all viable cells while preserving extracellular matrix (ECM) integrity. The major concerns of all decellularization protocols remain ECM disruption, immunogenicity and thrombogenicity. Accordingly the aim of this study was visualization of ultrastructural ECM disruption and human immune response and thrombogenicity using different decellularization protocols of porcine heart valves. Porcine pulmonary leaflets were decellularized with four different protocols: sodium deoxycholate, sodium dedecylsulfate, trypsin/EDTA, and trypsin-detergent-nuclease. Then the tissues were processed for histology and two-photon laser scanning microscopy (LSM). For thrombogenicity and immunogenicity testing tissues were incubated with human blood. The histological examination revealed no remaining cells and no significant differences in the ECM histoarchitecture in any group. LSM detected significant ECM alterations in all groups except sodium deoxycholate group with an almost completely preserved ECM. There was no increased immunogenicity between fresh and decellularized tissue. Compared to GA-fixed tissue however significantly increased immune responses and thrombogenicity was observed in all protocols. From our experiment, sodium deoxycholate enables cell removal with almost complete preservation of ECM structures. And all of these four decellularization protocols affected human immunological response and increased thrombogenicity.