RESUMO
Background: Valproic acid (VPA), a histone deacetylase inhibitor, has shown improved outcomes when used as a pharmaceutical intervention in animal studies of hemorrhage, septic shock, and combined injuries. This study was designed to investigate the ability of VPA to mitigate ischemia-reperfusion injury produced by prolonged tourniquet application to an extremity. Methods: The ischemia-reperfusion model in anesthetized rats was established using hemorrhage and a 3-hour tourniquet application. VPA was administered intravenously prior to tourniquet wear and removal. Ischemia-reperfusion injury was evaluated by investigating pathway signaling, immune modulation of cytokine release, remote organ injury, and skeletal muscle function during convalescence. Results: We found that VPA sustained Protein kinase B (Akt) phosphorylation and Insulin-like growth factor signaling and modulated the systemic release of interleukin (IL)-1ß, tumor necrosis factor alpha, and IL-6 after 2 hours of limb reperfusion. Additionally, VPA attenuated a loss in glomerular filtration rate at 3 days after injury. Histological and functional evaluation of extremity skeletal muscle at 3, 7, and 21 days after injury, however, demonstrated no significant differences in myocytic degeneration, necrotic formation, and maximal isometric tetanic torque. Conclusions: Our results demonstrate that VPA sustains early prosurvival cell signaling, reduces the inflammatory response, and improves renal function in a hemorrhage with prolonged ischemia and reperfusion model. However, these do not translate into meaningful preservation in limb function when applied as a pharmaceutical augmentation to tourniquet wear. Level of evidence: IV.
RESUMO
BACKGROUND: Viscoelastic measurements of coagulation provide much needed information, including guidance for triage and insight into bleeding disorders. The current clinical standards for these devices are the thromboelastogram (TEG) 5000 and the rotational thromboelastometer (ROTEM) delta, but a new product, the TEG 6s, has recently come to market, designed to simplify the user experience, reduce the required blood volume, and conduct multiple assays simultaneously. This study compares the performance of these three devices and examines the resiliency of the TEG 6s under various stresses. METHODS: The variances of coagulation metrics obtained by the TEG 6s (prototype and production models), TEG 5000, and ROTEM delta were compared using manufacturers' reagents and citrate-collected blood from healthy donors. Variability between devices was examined, and their performances under various motion and temperature stresses were compared by placing one unit on a linear or orbital shaker, in the cold, or in the heat while a counterpart remained stationary at room temperature. RESULTS: Although most comparable parameters had low degrees of variance, there were small but significantly increased variances found in some ROTEM delta and TEG 5000 parameters versus comparable TEG 6s parameters. Orbital rotation of the TEG 6s had no effect on means of any parameter but resulted in increased variance of 2 parameters, but linear motion with sudden striking had no observed impact on results. Similarly, 7-day exposure to heat (45°C) or cold (4°C) only resulted in minor deviations within normal ranges of the TEG 6s. DISCUSSION: The TEG 6s provides several improvements over other coagulation analyzers: it is easier to use and robustly resilient against motion and temperature stresses. These features suggest that it may be capable of deployment not only in the clinical laboratory but also to a variety of austere settings. LEVEL OF EVIDENCE: Diagnostic test, level III.