Thromboelastography After Murine TBI and Implications of Beta-Adrenergic Receptor Knockout

Time Course of Coagulo-Fibrinolytic Derangements During Acclimatization to High Altitude in Rabbits and a Preliminary Study on the Possible Mechanisms

Zhong, Xin, Zhao Ye, Xiaolin Zhou, Renqing Jiang, Yijun Jia, Wenqiong Du, Haoyang Yang, Lin Zhang, Bai Lu, and Zhaowen Zong. Time course of coagulo-fibrinolytic derangements during acclimatization to high altitude in rabbits and a preliminary study on the possible mechanisms. High Alt Med Biol. 00:000-000, 2022. Background: Conflicting data exist regarding changes in the coagulation system during acclimatization to high altitude (HA), which makes the prevention of thromboembolic events difficult. The present study aimed at observing the dynamic changes in the coagulo-fibrinolysis system during acclimatization to HA and at exploring the possible mechanisms. Materials and Methods: Twenty rabbits of both sexes were randomly divided into two groups, including group A rabbits (healthy plain controls) and group B rabbits (acutely exposed to HA). A traditional coagulation test, thromboelastography analysis, and full blood cell count were used to assess the coagulo-fibrinolytic changes at different time points. Plasma was collected to examine the levels of relevant biomarkers. Results: Six hours and 1 day after acute exposure to HA, the coagulo-fibrinolytic system demonstrated a hypercoagulable state. Further, 3 days after exposure to HA, group B rabbits showed hypocoagulability, increased fibrinolysis, and lower clot firmness and 7 days after exposure to HA, delayed coagulation, decreased fibrinolysis, and increased clot firmness were observed. Subsequently, 14, 21, and 28 days after exposure to HA, we found increased clot firmness. Increased platelet counts and concentrations of fibrinogen and plasminogen activator inhibitor-1 contributed to this change. Conclusion: The coagulo-fibrinolytic derangements during acclimatization to HA in rabbits demonstrated a dynamic pattern.

Early Propranolol Is Associated With Lower Risk of Venous Thromboembolism After Traumatic Brain Injury

BACKGROUND

Traumatic brain injury (TBI) results in an elaborate systemic cascade of secondary injury elicited in part by an intrinsic catecholamine response, which ultimately leads to changes in inflammation and coagulopathy. Attenuation of this catecholamine response with agents such as propranolol confers a survival advantage. The related impact of propranolol on venous thromboembolism (VTE) after TBI is largely unknown.

STUDY DESIGN

A single institution retrospective review was conducted of all TBI patients requiring intensive care unit (ICU) admission with an injury severity scale (ISS) ≥ 25 from January 2013 to May 2015. Patients who received at least one dose of propranolol within 24 hours of admission (PROP) were compared to patients who did not receive any doses of propranolol (NPROP) during their hospitalization.

RESULTS

Of the 131 patients analyzed, 31 (23.7%) patients received propranolol. The PROP cohort was more severely injured overall (ISS 29 vs 26.5, P = .02). While unadjusted VTE rates were similar (16.1% vs 19.0%, P = .72), the adjusted VTE rate was lower in the PROP cohort (AOR 0.20 (95% CI 0.04-0.97), adjusted P-value < .05).

CONCLUSION

Propranolol use in TBI patients who have sustained critical injuries may mitigate the risk of VTE. The mechanism by which this outcome is achieved requires further investigation.

Genetic Modulators of Traumatic Brain Injury in Animal Models and the Impact of Sex-Dependent Effects

Traumatic brain injury (TBI) is a major health problem causing disability and death worldwide. There is no effective treatment, due in part to the complexity of the injury pathology and factors affecting its outcome. The extent of brain injury depends on the type of insult, age, sex, lifestyle, genetic risk factors, socioeconomic status, other co-injuries, and underlying health problems. This review discusses the genes that have been directly tested in TBI models, and whether their effects are known to be sex-dependent. Sex differences can affect the incidence, symptom onset, pathology, and clinical outcomes following injury. Adult males are more susceptible at the acute phase and females show greater injury in the chronic phase. TBI is not restricted to a single sex; despite variations in the degree of symptom onset and severity, it is important to consider both female and male animals in TBI pre-clinical research studies.

Resuscitation Strategies for Traumatic Brain Injury

PURPOSE OF REVIEW

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality; however, little definitive evidence exists about most clinical management strategies. Here, we highlight important differences between two major guidelines, the 2016 Brain Trauma Foundation guidelines and the Lund Concept, along with recent pre-clinical and clinical data.

RECENT FINDINGS

While intracranial pressure (ICP) monitoring has been questioned, the majority of literature demonstrates benefit in severe TBI. The optimal cerebral perfusion pressure (CPP) and ICP are yet unknown, but likely as important is the concept of ICP burden. The evidence for anti-hypertensive therapy is strengthening. Decompressive craniectomy improves mortality, but at the cost of increased morbidity. Plasma-based resuscitation has demonstrated benefit in multiple pre-clinical TBI studies.

SUMMARY

The management of hemodynamics and intravascular volume are crucial in TBI. Based on recent evidence, ICP monitoring, anti-hypertensive therapy, minimal use of vasopressors/inotropes, and plasma resuscitation may improve outcomes.

Nonoperative Management of Blunt Splenic Trauma in Patients with Traumatic Brain Injury: Feasibility and Outcomes

INTRODUCTION

Preventing secondary insult to the brain is imperative following traumatic brain injury (TBI). Although TBI does not preclude nonoperative management (NOM) of splenic injuries, development of hypotension in this setting may be detrimental and could therefore lead trauma surgeons to a lower threshold for operative intervention and a potentially higher risk of failure of NOM (FNOM). We hypothesized that the presence of a TBI in patients with blunt splenic injury would lead to a higher risk of FNOM.

METHODS

Patients with blunt splenic injury were selected from the National Trauma Data Bank research datasets from 2007 to 2011. TBI was defined as AIS head ≥ 3 and FNOM as patients who underwent a spleen-related operation after 2 h from admission. TBI patients were compared to those without head injury. The primary outcome was FNOM.

RESULTS

Of 47,713 patients identified, 41,436 (86.8%) underwent a trial of NOM. FNOM was identical (10.6 vs. 10.8%, p = 0.601) among patients with and without TBI. TBI patients had lower adjusted odds for FNOM (AOR 0.66, p < 0.001), even among those with a high-grade splenic injury (AOR 0.68, p < 0.001). No difference in adjusted mortality was noted when comparing TBI patients with and without FNOM (AOR 1.01, p = 0.95).

CONCLUSIONS

NOM of blunt splenic trauma in TBI patients has higher adjusted odds for success. This could be related to interventions targeting prevention of secondary brain injury. Further studies are required to identify those specific practices that lead to a higher success rate of NOM of splenic trauma in TBI patients.

Impact of tranexamic acid on coagulation and inflammation in murine models of traumatic brain injury and hemorrhage

BACKGROUND

Posttraumatic coagulopathy and inflammation can exacerbate secondary cerebral damage after traumatic brain injury (TBI). Tranexamic acid (TXA) has been shown clinically to reduce mortality in hemorrhaging and head-injured trauma patients and has the potential to mitigate secondary brain injury with its reported antifibrinolytic and antiinflammatory properties. We hypothesized that TXA would improve posttraumatic coagulation and inflammation in a murine model of TBI alone and in a combined injury model of TBI and hemorrhage (TBI/H).

METHODS

An established murine weight drop model was used to induce a moderate TBI. Mice were administered intraperitoneal injections of 10 mg/kg TXA or equivalent volume of saline 10 min after injury. An additional group of mice was subjected to TBI followed by hemorrhagic shock using a pressure-controlled model. TBI/H mice were given intraperitoneal injections of TXA or saline during resuscitation. Blood was collected at intervals after injury to assess coagulation by rotational thromboelastometry (ROTEM) and inflammation by Multiplex cytokine analysis. Soluble P-selectin, a biomarker of platelet activation, and serum neuron-specific enolase, a biomarker of cerebral injury, were measured at intervals. Brain homogenates were analyzed for inflammatory changes by Multiplex enzyme-linked immunosorbent assay, and splenic tissue was collected for splenic cell population assessment by flow cytometry.

RESULTS

There were no coagulation, serum or cerebral cytokine, P-selectin, or neuron-specific enolase differences between mice treated with TXA or saline after TBI. After the addition of hemorrhagic shock and resuscitation to TBI, TXA administration still did not affect coagulation parameters, systemic or cerebral inflammation, or platelet activation, as compared with saline alone. At 24 hours after TBI, mice given TXA demonstrated lower splenic total cell counts central memory CD8, effector CD8, B cell, and increased naive CD4 cell populations. By contrast, TXA did not affect splenic leukocyte populations after combined TBI/H.

CONCLUSIONS

Despite clinical data suggesting a mortality benefit, TXA did not modulate coagulation, inflammation, or biomarker generation in either the TBI or TBI/H murine models. Administration of TXA after TBI altered splenic leukocyte populations, which may contribute to a change in posttraumatic immune status. Future studies should be done to investigate the role of TXA in the development of posttraumatic immunosuppression and risk of nosocomial infections.