Intramuscular Tranexamic Acid in Tactical and Combat Settings.

BACKGROUND: Uncontrolled hemorrhage remains a leading cause of preventable death in tactical and combat settings. Alternate routes of delivery of tranexamic acid (TXA), an adjunct in the management of hemorrhagic shock, are being studied. A working group for the Committee for Tactical Emergency Casualty Care reviewed the available evidence on the potential role for intramuscular (IM) administration of TXA in nonhospital settings as soon as possible from the point of injury. METHODS: EMBASE and MEDLINE/PubMed databases were sequentially searched by medical librarians for evidence of TXA use in the following contexts and/or using the following keywords: prehospital, trauma, hemorrhagic shock, optimal timing, optimal dose, safe volume, incidence of venous thromboembolism (VTE), IM bioavailability. RESULTS: A total of 183 studies were reviewed. The strength of the available data was variable, generally weak in quality, and included laboratory research, case reports, retrospective observational reviews, and few prospective studies. Current volume and concentrations of available formulations of TXA make it, in theory, amenable to IM injection. Current bestpractice guidelines for large-volume injection (i.e., 5mL) support IM administration in four locations in the adult human body. One case series suggests complete bioavailability of IM TXA in healthy patients. Data are lacking on the efficacy and safety of IM TXA in hemorrhagic shock. CONCLUSION: There is currently insufficient evidence to support a strong recommendation for or against IM administration of TXA in the combat setting; however, there is an abundance of literature demonstrating efficacy and safety of TXA use in a broad range of patient populations. Balancing the available data and risk- benefit ratio, IM TXA should be considered a viable treatment option for tactical and combat applications. Additional studies should focus on the optimal dose and bioavailability of IM dosing of patients in hemorrhagic shock, with assessment of potential downstream sequelae.

The effect of a bolus dose of etomidate on cortisol levels, mortality, and health services utilization: a systematic review.

STUDY OBJECTIVE: To synthesize the evidence on the effect of a bolus dose of etomidate on adrenal function, mortality, and health services utilization compared with other induction agents used for rapid sequence intubation. METHODS: We developed a systematic search strategy and applied it to 10 electronic bibliographic databases. We hand searched journals; reviewed conference proceedings, gray literature, and bibliographies of relevant literature; and contacted content experts for studies comparing a bolus dose of etomidate with other induction agents. Retrieved articles were reviewed and data were abstracted with standardized forms. Data were pooled with the random-effects model if at least 4 clinically homogenous studies of the same design reported the same outcome measure. All other data were reported qualitatively. RESULTS: From 3,083 titles reviewed, 20 met our inclusion criteria. Pooled mean cortisol levels were lower in elective surgical patients induced with etomidate compared with those induced with other agents between 1 and 4 hours postinduction. The differences varied from 6.1 microg/dL (95% confidence interval [CI] 2.4 to 9.9 microg/dL; P=.001) to 16.4 microg/dL (95% CI 9.7 to 23.1 microg/dL; P<.001). Two studies in critically ill patients reported significantly different cortisol levels up to 7 hours postinduction. None of the studies reviewed, nor our pooled estimate (odds ratio 1.14; 95% CI 0.81 to 1.60), showed a statistically significant effect on mortality. Only one study reported longer ventilator, ICU, and hospital lengths of stay in patients intubated with etomidate. CONCLUSION: The available evidence suggests that etomidate suppresses adrenal function transiently without demonstrating a significant effect on mortality. However, no studies to date have been powered to detect a difference in hospital, ventilator, or ICU length of stay or in mortality.

Phosphorylation of TIMAP by glycogen synthase kinase-3beta activates its associated protein phosphatase 1.

TIMAP (TGF-beta1 inhibited, membrane-associated protein) is a prenylated, endothelial cell-predominant protein phosphatase 1 (PP1c) regulatory subunit that localizes to the plasma membrane of filopodia. Here, we determined whether phosphorylation regulates TIMAP-associated PP1c function. Phosphorylation of TIMAP was observed in cells metabolically labeled with [32P]orthophosphate and was reduced by inhibitors of protein kinase A (PKA) and glycogen synthase kinase-3 (GSK-3). In cell-free assays, immunopurified TIMAP was phosphorylated by PKA and, after PKA priming, by GSK-3beta. Site-specific Ser to Ala substitution identified amino acid residues Ser333/Ser337 as the likely PKA/GSK-3beta phosphorylation site. Substitution of Ala for Val and Phe in the KVSF motif of TIMAP (TIMAPV64A/F66A) abolished PP1c binding and TIMAP-associated PP1c activity. TIMAPV64A/F66A was hyper-phosphorylated in cells, indicating that TIMAP-associated PP1c auto-dephosphorylates TIMAP. Constitutively active GSK-3beta stimulated phosphorylation of TIMAPV64A/F66A, but not wild-type TIMAP, suggesting that the PKA/GSK-3beta site may be subject to dephosphorylation by TIMAP-associated PP1c. Substitution of Asp or Glu for Ser at amino acid residues 333 and 337 to mimic phosphorylation reduced the PP1c association with TIMAP. Conversely, GSK-3 inhibitors augmented PP1c association with TIMAP-PP1c in cells. The 333/337 phosphomimic mutations also increased TIMAP-associated PP1c activity in vitro and against the non-integrin laminin receptor 1 in cells. Finally, TIMAP mutants with reduced PP1c activity strongly stimulated endothelial cell filopodia formation, an effect mimicked by the GSK-3 inhibitor LiCl. We conclude that TIMAP is a target for PKA-primed GSK-3beta-mediated phosphorylation. This phosphorylation controls TIMAP association and activity of PP1c, in turn regulating extension of filopodia in endothelial cells.