AT WSA 2016

CORONADO, CALIF. – Patients who develop a venous thromboembolism (VTE) following severe hemorrhage are more susceptible to complications, compared with their counterparts who do not; they also exhibit hypercoagulability and enhanced platelet function at admission, and have delayed recovery of coagulation and platelet function following injury.

Those are the key findings from a secondary analysis of data from the Pragmatic Randomized Optimal Platelet and Plasma Ratio (PROPPR) trial, which randomized 680 severely injured trauma patients from 12 level I trauma centers to receive 1:1:1 or 1:1:2 ratios of plasma to platelets to red blood cells ( JAMA 2015;313[5]:471-82 ). “The prevention of VTE following traumatic injury is an ongoing challenge,” Belinda H. McCully, PhD, said at the annual meeting of the Western Surgical Association. “Despite prophylaxis, about 25% of patients present with VTE, which is associated with higher complications and an increased risk for mortality. Common risk factors for mortality include age, body mass index, extremity injury, and immobility, but the precise mechanisms that contribute to VTE development are not well understood. We do know that the three main factors contributing to thrombosis include static flow, endothelial injury, and hypercoagulability. Clinically, coagulation is the most feasible factor to assess, mainly through the use of conventional coagulation tests, thromboelastography, platelet levels, and platelet function assays.” However, she continued, severe hemorrhage can lead to a hypocoagulable state that is further exacerbated by hemodilution, acidosis, and hypothermia, creating traumatic-induced coagulopathy. “Despite this hypocoagulable state, VTEs are still present in this patient population.”

Dr. McCully of the division of trauma, critical care, and acute care surgery in the department of surgery at Oregon Health & Science University, Portland, and her associates hypothesized that enhanced, earlier recovery of coagulation function is associated with increased VTE risk in severely injured trauma patients. To test this hypothesis, they conducted a secondary analysis of the PROPPR database, excluding patients who received anticoagulants, to rule out any bias against VTE development, as well as patients who died within 24 hours, to reduce the survival bias. This left 558 patients: 475 who did not develop a VTE, and 83 who did (defined as those who developed deep vein thrombosis or pulmonary embolism). Patient characteristics of interest included age, sex, BMI, mechanism of injury, and injury severity, as well as the transfusion group, the type of blood products given, and the percentage of patients given procoagulants. The investigators also assessed length of stay and complication incidence previously defined by the trial. During the trial, blood samples were taken from admission up to 72 hours and were used to asses both whole blood coagulation using thromboelastography and platelet function using the Multiplate assay.

Dr. McCully reported that VTE patients and non-VTE patients demonstrated similar admission platelet function activity and inhibition of all platelet function parameters at 24 hours (P less than .05). The onset of platelet function recovery was delayed in VTE patients, specifically for arachidonic acid, adenosine-5’-diphosphate, and collagen. Changes in thromboelastography, clot time to initiation, formation, rate of formation, and strength and index of platelet function from admission to 2 hours indicated increasing hypocoagulability (P less than .05) but suppressed clot lysis in both groups. Compared with patients in the non-VTE group, the VTE group had lower mortality (4% vs. 13%) but increased total hospital days (a mean of 30 vs. 16; P less than .05).

Adverse outcomes were also more prevalent in the VTE group, compared with the non-VTE group, and included systemic inflammatory response syndrome (82% vs. 72%), acute kidney injury (36% vs. 26%), infection (61% vs. 31%), sepsis (60% vs. 28%), and pneumonia (34% vs. 19%; P less than 0.05 for all associations). Conversely, regression analysis showed that VTE was associated only with total hospital days (odds ratio, 1.12), while adverse events were similar between the two groups. “From this we can conclude that VTE development following trauma may be attributed to hypercoagulable thromboelastography parameters and enhanced platelet function at admission, and compensatory mechanisms in response to a delayed recovery of coagulation and platelet function,” Dr. McCully said.

She acknowledged certain limitations of the study, including the fact that it was a secondary analysis of prospectively collected data. “We also plan to assess plasma markers of clot strength and fibrinolysis, which is an ongoing process,” she said. “Despite excluding patients that died within 24 hours, there was still a survival bias in the VTE group.”

The PROPPR study was supported by the National Heart, Lung, and Blood Institute and by the Department of Defense. Dr. McCully reported having no relevant financial disclosures.