Variant-derived SARS-CoV-2 spike protein does not directly cause platelet activation or hypercoagulability.

Thrombosis has been associated with severity and mortality in COVID-19. SARS-CoV-2 infects the host via its spike protein. However, direct effects of spike proteins from SARS-CoV-2 variants on platelet activity and coagulability have not been examined. An ethically approved ex vivo study was performed under a preplanned power analysis. Venous blood was collected from 6 healthy subjects who gave prior written consent. The samples were divided into 5 groups: without spike proteins (group N) and with spike proteins derived from alpha, beta, gamma, and delta SARS-CoV-2 variants (groups A, B, C, and D, respectively). Platelet aggregability, P-selectin expression, platelet-associated complement-1 (PAC-1) binding, platelet count, and mean platelet volume (MPV) were measured in all 5 groups, and thromboelastography (TEG) parameters were measured in groups N and D. The % change in each parameter in groups A to D was calculated relative to the value in group N. Data were analyzed by Friedman test, except for TEG parameters, which were evaluated by Wilcoxon matched pairs test. P < 0.05 was considered significant. This study included 6 participants based on a power analysis. There were no significant differences in platelet aggregability under stimulation with adenosine diphosphate 5 µg/ml, collagen 0.2 or 0.5 µg/ml, and Ser-Phe-Leu-Leu-Arg-Asn-amide trifluoroacetate salt (SFLLRN) 0.5 or 1 µM in groups A-D compared to group N. There were also no significant differences in P-selectin expression and PAC-1 binding under basal conditions or SFLLRN stimulation, and no significant differences in platelet count, MPV and TEG parameters. Platelet hyperactivity and blood hypercoagulability have been reported in COVID-19 patients, but spike proteins at 5 µg/ml from SARS-CoV-2 variants (alpha, beta, gamma, delta) did not directly cause these effects in an ex vivo study. This study was approved by the Ethics Committee of Kyoto University Hospital (R0978-1) on March 06, 2020.

Platelet function of whole blood after short-term cold storage: A prospective in vitro observational study.

BACKGROUND: There is no standardized storage temperature of whole blood for acute normovolemic hemodilution (ANH). STUDY DESIGN AND METHODS: We conducted a prospective observational study to examine the difference in platelet function between short-term whole blood storage at 4 and 22°C. Venous blood (40 ml) was collected from seven healthy subjects who gave prior written consent. The samples were divided into three groups: before storage (group Pre), cold (4°C) storage (group C), and room temperature (22°C) storage (group R). Groups C and R were tested after 6 h of blood storage. Platelet aggregability, platelet factor 4 (PF4), ß-thromboglobulin (ß-TG), P-selectin expression, pH, PO2 , PCO2 , glucose, lactate, blood count, and thromboelastography (TEG) parameters were measured. The percentage change in each parameter in groups C and R was calculated using the value in group Pre as a reference. These data were then compared between groups C and R using a Wilcoxon matched pairs test. p < 0.05 was considered to be statistically significant. RESULTS: Compared with group R, group C showed significantly higher platelet aggregability with adenosine diphosphate (ADP) 2, 4, and 6 µM (all p = 0.016) and collagen 1 µg/ml (p = 0.047) stimulation, and significantly lower PF4 and ß-TG elevation (both p = 0.031), glucose consumption (p = 0.031), and lactate production (p = 0.016). The ADP channel in TEG showed a significant increase in platelet aggregation rate in group C compared to group R. DISCUSSION: Cold storage of whole blood in ANH may provide improved storage conditions for platelets and contribute to improved hemostasis compared to room temperature storage.

Effects of whole blood storage in a polyolefin blood bag on platelets for acute normovolemic hemodilution.

Acute normovolemic hemodilution (ANH) is a potential transfusion method for platelets, as well as for red blood cells. However, previous studies have shown that whole blood storage in ANH decreases platelet aggregability by 14.7-76.3% and that this decrease is not recovered by reinfusion. We investigated whether a new whole blood storage method for 6 h using a polyolefin bag, based on the platelet concentrates storage method, would maintain platelet function better than the conventional method using a polyvinyl chloride bag. We demonstrated that storage of whole blood in a polyolefin bag maintained ADP-induced aggregation rates at more than twofold higher than those in a polyvinyl chloride bag, and also significantly suppressed P-selectin expression, a platelet activation marker (ADP-induced aggregation rates: 24.6 ± 5.1% vs. 51.7 ± 11.5%, p = 0.002; P-selectin expression; 50.3 ± 8.4MFI vs. 31.6 ± 9.3MFI, p = 0.018). These results could be attributed to the high gas permeability of polyolefin, which lowered PCO2 and maintained a high pH with or without agitation. There were no significant changes in platelet count and red blood cell parameters due to the storage methods. Our results suggest that ANH using polyolefin bags is advantageous in improving hemostatic function compared to the conventional method.

Use of argatroban in combination with nafamostat mesilate in open-heart surgery for a pediatric patient with heparin-induced thrombocytopenia type II: a case report.

BACKGROUND: Heparin-induced thrombocytopenia type II (HIT II) is a rare, immune-mediated complication of heparin therapy and can cause life-threatening thromboembolism. However, perioperative anticoagulation therapy for patients with a complication of HIT II has not been established. CASE PRESENTATION: A 6-year-old boy with tetralogy of Fallot underwent radical intracardiac repair with administration of argatroban at 1 year old due to positive HIT antibody. Reoperation was scheduled for pulmonary valve insufficiency, using argatroban and nafamostat mesilate as anticoagulants. Argatroban has a long onset time and the activated coagulation time (ACT) requires 7-26 h to return to the preadministration level, making hemorrhage control difficult, while half-life of nafamostat mesilate is shorter than that of argatroban. Celite ACT reflects the effects of both argatroban and nafamostat mesilate, but kaolin ACT reflects only the effect of argatroban. Due to the early termination of argatroban administration based on Celite and kaolin ACTs, ACT recovered to ≤ 200 s at 5 h after the end of argatroban administration. CONCLUSION: Celite and kaolin ACTs can be used as markers to obtain close control of the required dose of argatroban in combination with nafamostat mesilate for the management of HIT II patients.

Successful perioperative management of living-donor liver transplantation for a patient with severe methylmalonic acidemia: a case report.

BACKGROUND: Methylmalonic acidemia (MMAemia) is a rare hereditary disease affecting organic acid metabolism. It causes recurrent metabolic acidosis and secondary mitochondrial dysfunction, resulting in a poor prognosis. Liver transplantation (LT) has been performed to facilitate the metabolism of organic acids and improve the prognosis of MMAemia. However, there have been few reports on perioperative management of LT. CASE PRESENTATION: A 22-month-old female with severe MMAemia was scheduled to receive LT to relieve recurrent metabolic acidosis despite dietary and pharmacological treatment. General anesthesia was maintained without propofol or nitrous oxide, which can worsen MMAemia-induced metabolic acidosis during anesthesia for LT. Strict metabolic and respiratory management enabled the operation to be successfully performed without metabolic acidosis. CONCLUSION: Perioperative management of LT for MMAemia is challenging for anesthesiologists because of the possibility of serious metabolic acidosis. We succeeded in preventing metabolic decompensation by avoiding the use of propofol and nitrous oxide.