The regional whole blood program in San Antonio, TX: A 3-year update on prehospital and in-hospital transfusion practices for traumatic and non-traumatic hemorrhage.

Low titer type O Rh-D + whole blood (LTO + WB) has become a first-line resuscitation medium for hemorrhagic shock in many centers around the World. Showing early effectiveness on the battlefield, LTO + WB is used in both the pre-hospital and in-hospital settings for traumatic and non-traumatic hemorrhage resuscitation. Starting in 2018, the San Antonio Whole Blood Collaborative has worked to provide LTO + WB across Southwest Texas, initially in the form of remote damage control resuscitation followed by in-hospital trauma resuscitation. This program has since expanded to include pediatric trauma resuscitation, obstetric hemorrhage, females of childbearing potential, and non-traumatic hemorrhage. The objective of this manuscript is to provide a three-year update on the successes and expansion of this system and outline resuscitation challenges in special populations.

Saving the brain after mild-to-moderate traumatic injury: A report on new insights of the physiology underlying adequate maintenance of cerebral perfusion.

ABSTRACT: Traumatic brain injury (TBI) is associated with increased morbidity and mortality in civilian trauma and battlefield settings. It has been classified across a continuum of dysfunctions, with as much as 80% to 90% of cases diagnosed as mild to moderate in combat casualties. In this report, a framework is presented that focuses on the potential benefits for acute noninvasive treatment of reduced cerebral perfusion associated with mild TBI by harnessing the natural transfer of negative intrathoracic pressure during inspiration. This process is known as intrathoracic pressure regulation (IPR) therapy, which can be applied by having a patient breath against a small inspiratory resistance created by an impedance threshold device. Intrathoracic pressure regulation therapy leverages two fundamental principles for improving blood flow to the brain: (1) greater negative intrathoracic pressure enhances venous return, cardiac output, and arterial blood pressure; and (2) lowering of intracranial pressure provides less resistance to cerebral blood flow. These two effects work together to produce a greater pressure gradient that results in an improvement in cerebral perfusion pressure. In this way, IPR therapy has the potential to counter hypotension and hypoxia, potentially significant contributing factors to secondary brain injury, particularly in conditions of multiple injuries that include severe hemorrhage. By implementing IPR therapy in patients with mild-to-moderate TBI, a potential exists to provide early neuroprotection at the point of injury and a bridge to more definitive care, particularly in settings of prolonged delays in evacuation such as those anticipated in future multidomain operations. LEVEL OF EVIDENCE: Report.

The research agenda for trauma critical care.

In this research agenda on the acute and critical care management of trauma patients, we concentrate on the major factors leading to death, namely haemorrhage and traumatic brain injury (TBI). In haemostasis biology, the results of randomised controlled trials have led to the therapeutic focus moving away from the augmentation of coagulation factors (such as recombinant factor VIIa) and towards fibrinogen supplementation and administration of antifibrinolytics such as tranexamic acid. Novel diagnostic techniques need to be evaluated to determine whether an individualised precision approach is superior to current empirical practice. The timing and efficacy of platelet transfusions remain in question, while new blood products need to be developed and evaluated, including whole blood variants, lyophilised products and novel red cell storage modalities. The current cornerstones of TBI management are intracranial pressure control, maintenance of cerebral perfusion pressure and avoidance of secondary insults (such as hypotension, hypoxaemia, hyperglycaemia and pyrexia). Therapeutic hypothermia and decompressive craniectomy are controversial therapies. Further research into these strategies should focus on identifying which subgroups of patients may benefit from these interventions. Prediction of the long-term outcome early after TBI remains challenging. Early magnetic resonance imaging has recently been evaluated for predicting the long-term outcome in mild and severe TBI. Novel biomarkers may also help in outcome prediction and may predict chronic neurological symptoms. For trauma in general, rehabilitation is complex and multidimensional, and the optimal timing for commencement of rehabilitation needs investigation. We propose priority areas for clinical trials in the next 10 years.

Heterozygous cellular glutathione peroxidase deficiency in the mouse: abnormalities in vascular and cardiac function and structure.

BACKGROUND: Oxidant stress has been implicated in the pathogenesis of atherothrombosis and other vascular disorders accompanied by endothelial dysfunction. Glutathione peroxidases (GPx) play an important role in the cellular defense against oxidant stress by utilizing glutathione (GSH) to reduce lipid hydroperoxides and hydrogen peroxide to their corresponding alcohols. Cellular GPx (GPx-1) is the principal intracellular isoform of GPx. We hypothesized that GPx-1 deficiency per se induces endothelial dysfunction and structural vascular abnormalities through increased oxidant stress. METHODS AND RESULTS: A murine model of heterozygous deficiency of GPx-1 (GPx(+/-)) was investigated to examine this hypothesis. Mesenteric arterioles in GPx-1(+/-) mice demonstrated vasoconstriction to acetylcholine compared with vasodilation in wild-type mice (maximal change in vessel diameter, -13.0+/-2.8% versus 13.2+/-2.8%, P<0.0001). We also noted an increase in the plasma and aortic levels of the isoprostane iPF(2alpha)-III, a marker of oxidant stress, in GPx-1(+/-) mice compared with wild-type mice (170.4+/-23 pg/mL plasma versus 98.7+/-7.1 pg/mL plasma, P<0.03; 11.7+/-0.87 pg/mg aortic tissue versus 8.2+/-0.55 pg/mg aortic tissue, P<0.01). Histological sections from the coronary vasculature of GPx-1(+/-) mice show increased perivascular matrix deposition, an increase in the number of adventitial fibroblasts, and intimal thickening. These structural abnormalities in the myocardial vasculature were accompanied by diastolic dysfunction after ischemia-reperfusion. CONCLUSIONS: These findings demonstrate that heterozygous deficiency of GPx-1 leads to endothelial dysfunction, possibly associated with increased oxidant stress, and to significant structural vascular and cardiac abnormalities. These data illustrate the importance of this key antioxidant enzyme in functional and structural responses of the mammalian cardiovascular system.

Cellular redox state and endothelial dysfunction in mildly hyperhomocysteinemic cystathionine beta-synthase-deficient mice.

Previous in vitro experiments have shown that hyperhomocysteinemia leads to oxidative inactivation of nitric oxide, in part by inhibiting the expression of cellular glutathione peroxidase (GPx-1). To elucidate the role of intracellular redox status on homocysteine-induced endothelial dysfunction and oxidant stress, heterozygous cystathionine beta-synthase-deficient (CBS(-/+)) and wild-type (CBS(+/+)) mice were treated with the cysteine donor L-2-oxothiazolidine-4-carboxylic acid (OTC). CBS(-/+) mice had significantly lower GPx-1 activity compared with their CBS(+/+) littermates, and OTC treatment led to a modest increase in tissue GPx-1 activity and significant increases in total thiols and in reduced glutathione levels in both CBS(+/+) and CBS(-/+) mice. Superfusion of the mesentery with beta-methacholine or bradykinin produced dose-dependent vasodilation of mesenteric arterioles in CBS(+/+) mice and in CBS(+/+) mice treated with OTC. In contrast, mesenteric arterioles from CBS(-/+) mice manifested dose-dependent vasoconstriction in response to both agonists. OTC treatment of CBS(-/+) mice restored normal microvascular vasodilator reactivity to beta-methacholine and bradykinin. These findings demonstrate that mild hyperhomocysteinemia leads to endothelial dysfunction in association with decreased bioavailable nitric oxide. Increasing the cellular thiol and reduced glutathione pools and increasing GPx-1 activity restores endothelial function. These findings emphasize the importance of intracellular redox balance for nitric oxide bioactivity and endothelial function.

L-Homocysteine and L-homocystine stereospecifically induce endothelial nitric oxide synthase-dependent lipid peroxidation in endothelial cells.

Atherothrombotic cardiovascular disease associated with hyperhomocysteinemia has been proposed to result, at least in part, from increased vascular oxidative stress. Here we characterize one mechanism by which homocyteine may induce a vascular cell type-specific oxidative stress. Our results show that L-homocysteine at micromolar levels stereospecifically increases lipid peroxidation in cultured endothelial cells, but not in vascular smooth muscle cells or when medium is incubated in the absence of cells. Consistent with these observations, homocysteine also increases the formation of intracellular reactive oxygen species. The pro-oxidant effect of homocysteine can be fully replicated by an equivalent concentration of homocystine (i.e., an oxidized form of homocysteine), but not with cysteine or glutathione. Homocyst(e)ine-dependent lipid peroxidation is independent of H(2)O(2) and alterations in glutathione peroxidase activity, but dependent on superoxide. Mechanistically, the pro-oxidant effect of homocysteine appears to involve endothelial nitric oxide synthase (eNOS), as it is blocked by the eNOS inhibitor L-N(G)-nitroarginine methyl ester. Thus, homocyst(e)ine actively promotes oxidative stress in endothelial cells via an eNOS-dependent mechanism.

Mitochondrial damage-associated molecular patterns activate γδ T-cells.

Gamma delta T-cells have been shown to be important in the early immunoinflammatory response to injury, which can be independent of infection. This sterile inflammatory response is believed to be, in part, associated with danger-associated molecular patterns (DAMPs). Mitochondrial DAMPs (MTDs) have been shown to be important in trauma-induced neutrophil activation, but it is unknown whether MTDs activate other innate immune cells, such as γδ T-cells. To study this, splenic CD3(+) γδ T-cells were isolated from αß T-cell-deficient C57BL/6 mice and mitochondria isolated from wild type mouse livers. MTDs were isolated from mitochondria by sonication and centrifugation. Gamma delta T-cells were incubated with various concentrations of MTDs (0-500 µg/ml) for 24 h. T-cells were phenotyped for TLR expression by flow cytometry and the supernatants assayed for cytokine and growth factor content. MTDs caused a dose-dependent increase in TLR2 and TLR4 expression by γδ T-cells. Both the percentage of cells positive for TLRs and the degree of expression increased. MTDs also induced the production of IL-1ß, IL-6, IL-10, RANTES, fibroblast growth factor-basic and vascular endothelial growth factor by γδ T-cells. These findings support the concept that the MTDs released after tissue/cellular injury are capable of activating γδ T-cells, thus initiating sterile inflammation, as well as subsequent healing processes.

Cellular glutathione peroxidase deficiency and endothelial dysfunction.

Cellular glutathione peroxidase (GPx-1) is the most abundant intracellular isoform of the GPx antioxidant enzyme family. In this study, we hypothesized that GPx-1 deficiency directly induces an increase in vascular oxidant stress, with resulting endothelial dysfunction. We studied vascular function in a murine model of homozygous deficiency of GPx-1 (GPx-1(-/-)). Mesenteric arterioles of GPx-1(-/-) mice demonstrated paradoxical vasoconstriction to beta-methacholine and bradykinin, whereas wild-type (WT) mice showed dose-dependent vasodilation in response to both agonists. One week of treatment of GPx-1(-/-) mice with L-2-oxothiazolidine-4-carboxylic acid (OTC), which increases intracellular thiol pools, resulted in restoration of normal vascular reactivity in the mesenteric bed of GPx-1(-/-) mice. We observed an increase of the isoprostane iPF(2alpha)-III, a marker of oxidant stress, in the plasma and aortas of GPx-1(-/-) mice compared with WT mice, which returned toward normal after OTC treatment. Aortic sections from GPx-1(-/-) mice showed increased binding of an anti-3-nitrotyrosine antibody in the absence of frank vascular lesions. These findings demonstrate that homozygous deficiency of GPx-1 leads to impaired endothelium-dependent vasodilator function presumably due to a decrease in bioavailable nitric oxide and to increased vascular oxidant stress. These vascular abnormalities can be attenuated by increasing bioavailable intracellular thiol pools.