A Novel Platelet Function Assay for Trauma

VASCULAR-PLATELET HEMOSTASIS OF INJURED PATIENTS: PROSPECTIVE OBSERVATIONAL STUDY

OBJECTIVE

The aim: We study vascular-platelet hemostasis peculiarities in patients with severe trauma.

PATIENTS AND METHODS

Materials and methods: We included 50 patients, who were divided into control (n=15) and study (n=35) groups. The control group included patients without traumatic injuries, study group - patients with severe trauma. The study group was divided into the I subgroup (patients received 1 g tranexamic acid IV at the prehospital stage), and the II subgroup (1 g tranexamic acid IV after hospital admission).

RESULTS

Results: The main changes in the I subgroup started on the 3rd day, while in the II subgroup - on the 1st day. Patients of both subgroups on the 1st and 3rd days had a normal number of platelets in venous blood, however, on the 3rd day, there was a decreasing level of discocytes whereas the level of discoechinocytes, spherocytes, spheroechinocytes, and the sum of active forms of platelets were increased in comparison with the control group (p<0.05).

CONCLUSION

Conclusions: The changes in vascular-platelet hemostasis in patients appeared in the I subgroup on the 3rd day, while in the II subgroup - on the 1st day. For the I subgroup was the decreasing level of discocytes, whereas the level of discoechinocytes, spherocytes, spheroechinocytes, and the sum of active forms of platelets were increased. For the II subgroup on the 1st day, there was an increasing sum of active forms of platelets, on the 3rd day - the level of discocytes was decreased, and levels of discoechinocytes, spherocytes, spheroechinocytes, and the sum of active forms of platelets were increased.

DYNAMICS OF INDICATORS IN PLATELET HEMOSTASIS IN POLYTRAUMA AND ENLARGED BODY MASS INDEX

OBJECTIVE

The aim: Analyze the dynamics of indicators in platelet hemostasis in polytrauma and enlarged body mass index.

PATIENTS AND METHODS

Materials and methods: A comprehensive study of hemostasis was performed in 224 sick with polytrauma and high body mass index within a month and on the 360th day.

RESULTS

Results: In Group I, the aggregation time was shortened during stimulation of ristomycin by 25% from day 1 to day 3. In patients in the II group, with the addition of ADP, the presence of hyperaggregation of platelets was determined from the 1st to the 3rd day and from the 30th to the 360th (a 36% reduction in time compared to the control was determined). In patients in the III group, ADP-aggregation was reduced on the 1st day (by 34%), after which hypoaggregation was noted (from the 3rd to the 14th and on the 360th day) with an increase in the rate of approximately 33% compared to the control group, after which there was a persistent hyperaggregation from 30 to 360 day with a 25% reduction in aggregation time.

CONCLUSION

Conclusions: An individual response of platelets to damage was established depending on the severity of polytrauma and increased body mass index.

PLATELET FUNCTION IN TRAUMA: IS CURRENT TECHNOLOGY IN FUNCTION TESTING MISSING THE MARK IN INJURED PATIENTS?

ABSTRACT

Platelets are subcellular anucleate components of blood primarily responsible for initiating and maintaining hemostasis. After injury to a blood vessel, platelets can be activated via several pathways, resulting in changed shape, adherence to the injury site, aggregation to form a plug, degranulation to initiate activation in other nearby platelets, and acceleration of thrombin formation to convert fibrinogen to fibrin before contracting to strengthen the clot. Platelet function assays use agonists to induce and measure one or more of these processes to identify alterations in platelet function that increase the likelihood of bleeding or thrombotic events. In severe trauma, these assays have revealed that platelet dysfunction is strongly associated with poor clinical outcomes. However, to date, the mechanism(s) causing clinically significant platelet dysfunction remain poorly understood. We review the pros, cons, and evidence for use of many of the popular assays in trauma, discuss limitations of their use in this patient population, and present approaches that can be taken to develop improved functional assays capable of elucidating mechanisms of trauma-induced platelet dysfunction. Platelet dysfunction in trauma has been associated with need for transfusions and mortality; however, most of the current platelet function assays were not designed for evaluating trauma patients, and there are limited data regarding their use in this population. New or improved functional assays will help define the mechanisms by which platelet dysfunction occurs, as well as help optimize future treatment.

Microelectromechanical System Measurement of Platelet Contraction: Direct Interrogation of Myosin Light Chain Phosphorylation

Myosin Light Chain (MLC) regulates platelet contraction through its phosphorylation by Myosin Light Chain Kinase (MLCK) or dephosphorylation by Myosin Light Chain Phosphatase (MLCP). The correlation between platelet contraction force and levels of MLC phosphorylation is unknown. We investigate the relationship between platelet contraction force and MLC phosphorylation using a novel microelectromechanical (MEMS) based clot contraction sensor (CCS). The MLCK and MLCP pair were interrogated by inhibitors and activators of platelet function. The CCS was fabricated from silicon using photolithography techniques and force was validated over a range of deflection for different chip spring constants. The force of platelet contraction measured by the clot contraction sensor (CCS) was compared to the degree of MLC phosphorylation by Western Blotting (WB) and ELISA. Stimulators of MLC phosphorylation produced higher contraction force, higher phosphorylated MLC signal in ELISA and higher intensity bands in WB. Inhibitors of MLC phosphorylation produced the opposite. Contraction force is linearly related to levels of phosphorylated MLC. Direct measurements of clot contractile force are possible using a MEMS sensor platform and correlate linearly with the degree of MLC phosphorylation during coagulation. Measured force represents the mechanical output of the actin/myosin motor in platelets regulated by myosin light chain phosphorylation.