Letter to the Editor Regarding "Viscoelastic Hemostatic Assays and Outcomes in Traumatic Brain Injury: A Systematic Literature Review".

Letter:

The world is currently facing a critical shortage of blood products. The coronavirus disease 2019 (COVID-19) pandemic has led to supply chain disruptions, staffing shortages at donation centers, and shrinking donor populations, especially as traditional settings for blood drives (including workplaces and schools) have become less and less feasible. Despite social distancing and shelter-in-place mandates, health care utilization and blood product requirements remain high during the pandemic, which may be due to disproportionately elevated rates of trauma and violence, at least in the United States. , The shortage has also been compounded by hospitals seeking to restore surgical services to prepandemic levels, rescheduling procedures that were deferred during recent surges of coronavirus variants. The American Red Cross, which supplies 40% of the U.S. blood supply, reports that it has drastically limited its distribution, with some hospitals receiving only 1 in 4 of the blood products required. Furthermore, it is unclear at this time how the dire humanitarian crisis unfolding in Ukraine will impact the global need for blood products in the future.

In the midst of this shortage, neurosurgeons are uniquely positioned to serve as stewards of blood products, by advocating for evidence-based resuscitation and transfusion strategies and by leveraging their role in the health system to support sustainable policies for blood utilization, especially in the care of trauma patients. Early evidence during the pandemic highlighted the continued demand for emergent neurosurgery, despite lockdowns, with a growing proportion of resources dedicated to acute neurosurgical pathology, including neurotrauma. , It is well known that injured patients, especially patients with traumatic brain injury (TBI), often present with coagulopathy.11, 12, 13 However, despite long-standing research efforts, the pathophysiology of TBI-induced coagulopathy is not fully understood, and as a result there is significant variability across centers in the management of coagulopathy after head injury, , with many institutions still maintaining liberal transfusion strategies.

The evidence is becoming increasingly clear that transfusion should not be a one-size-fits-all approach, and broader use of viscoelastic hemostatic assays (VHAs) may pave the way for more tailored treatment paradigms for coagulopathy in neurosurgery. The conventional coagulation assays (CCAs) commonly used to guide blood product usage monitor only clot initiation, failing to assess complex hemostatic pathways, and often appear normal even in the presence of coagulopathy. In contrast, VHAs, including thromboelastography (TEG; Haemonetics SA, Signy, Switzerland) and rotational thromboelastometry (ROTEM; Werfen, Bedford, MA), offer more detailed information about hemostatic potential, measuring the initiation, amplification, propagation, and termination of clot formation. The addition of platelet mapping to these assays also isolates the contribution of platelets to clot strength. As a result, some centers have used VHAs to detect functional differences in coagulation among patients with hemorrhagic stroke, which were not identifiable on CCAs but appeared responsible for hematoma expansion in their respective series. , 22, 23, 24

In their recent systematic review, Shammassian et al. summarize the available literature on VHAs and clinical outcomes in TBI, which they argue remains inconclusive to date. As the authors explain, the heterogeneity of published studies limits comparison of VHAs and CCAs beyond the scope of each individual analysis. Moreover, because the complexity of coagulation is often reduced in binary fashion to either presence or absence of coagulopathy, there is likely residual confounding that the studies included were not powered to overcome. Nevertheless, this review aligns with prior ones highlighting early associations between abnormal VHA profiles and poor outcomes after TBI. TEG parameters suggesting hypocoagulability have been associated with increased risk of requiring a neurosurgical procedure, greater length of stay in the hospital and intensive care unit, and greater risk of mortality.27, 28, 29 Multiple centers have also used point-of-care VHAs to predict clinically significant progression of intracranial hemorrhage after TBI.30, 31, 32, 33

Although the existing outcomes data for VHA use in TBI are not perfect, there is ample evidence that these assays still have significant potential for curbing wasteful utilization of blood products. In non-neurosurgical populations, VHAs have shown efficacy in diagnosing early coagulopathy and predicting transfusion requirements in trauma patients , ; minimizing both perioperative blood loss and blood product consumption in lung transplantation; and reducing transfusion requirements in cardiac surgery, generating substantial cost savings without compromising clinical outcomes.37, 38, 39 Recent literature has shown similar promise for goal-directed transfusion among neurosurgical populations as well. In adult spinal deformity surgery, ROTEM-guided therapy has enabled early identification of hypofibrinogenemia and reduced transfusion volumes (and transfusion-related costs). , In patients with TBI, goal-directed transfusion strategies using TEG have been shown to reduce platelet transfusion requirements, without worsening intracranial bleeding, need for neurosurgical re-intervention, length of stay, or mortality.43, 44, 45, 46 Our institutional experience has reaffirmed these findings: in a pragmatic interventional trial, a TEG-based protocol significantly reduced platelet transfusions without risking expansion of intracranial hemorrhage among elderly patients with TBI.

Although more high-quality, prospective studies required to fully demonstrate the effect of VHAs on mortality and other clinical outcomes, the evidence to date is encouraging that these assays can be used to identify coagulopathic states earlier and more precisely than CCAs , for the purposes of guiding transfusion. We encourage our colleagues to explore implementation of viscoelastic testing into standardized clinical pathways, not only for its cost-saving benefits, but also to fulfill our collective responsibility to support judicious transfusion practices during this difficult period. With no end in sight to this shortage, such scarce resources should not be used in vain.