Experimental Models of Hemorrhagic Shock: A Review

Massive blood loss leading to hypovolemic shock is still a life-threatening situation. Recently, a great number of investigations have been conducted in order to understand the pathophysiological and immunological changes taking place during shock and to develop treatment strategies. These preclinical trials are based on animal studies. Although a wide spectrum of species and experimental models are available to researchers, it is rather difficult to create an ideal animal model to study hemorrhagic shock. A major challenge for investigators is the generation of a system which is simple, easily reproducible and standardized, while being an accurate replica of the clinical situation. The goal of this review is to summarize the current experimental models of hemorrhagic shock, highlighting their advantages and disadvantages to help researchers find the most appropriate model for their own experiments on hypovolemic shock

Postconditioning in major vascular surgery: prevention of renal failure

This study investigates teachers in the Swedish ten-year compulsory school who use ICT(Information and communication technology) in their classroom practice. It poses andgives answers to questions about what is contributing most to explain why they choose touse computers and information technology in their work with students/pupils and usesmultiple regression analysis in order to investigate the best pattern of predictive variables.A significant model emerged suggesting that teachers using ICT with students wereinterested in changing their classroom practice. They also felt self-efficacious in usingcomputers in education and they have positive attitudes toward using ICT in education.The present investigation differs from other studies in that it examines teachers whoalready are using technology in their classroom practice and it could be seen as a buildingblock in the development of knowledge about how teachers can become more competentand confident in using ICT in their pedagogical work in classroom practice

Távoli szervi kondicionálás: rövid távú hepatoprotectiv hatások patkánymodellben = Remote Ischemic Conditioning: Short-Term Effects on Rat Liver Ischemic-Reperfusion Injury

Bevezetés: Az ischaemiás-reperfúziós károsodások mérséklésére kipróbált módszerek között újszerű elképzelés a célszervi ischaemia alatt alkalmazott távoli szervi ischaemiás perkondicionálás. Célkitűzés: Patkánymáj ischaemiás-reperfúziós modellben alkalmazni ezen újszerű kondicionálási technikát. Módszer: Hím Wistar patkányok (n = 30, 10/csoport) 60 perc parciális ischaemiában, majd 60 perc reperfúzióban részesültek. Egy csoportban perkondicionálás került alkalmazásra a májischaemia utolsó 40 percében, az infarenalis aortán. A máj és az alsó végtag mikrokeringésének regisztrálása lézeres Doppler-áramlásmérővel történt. A reperfúziót követően a máj szövettani elváltozásainak analízise és a májszöveti hősokkfehérje-72-expresszió mérése mellett a szérumtranszamináz-aktivitások, továbbá a redox-homeosztázis állapotának meghatározása történt. Eredmények: A máj és az alsó végtag mikrocirkulációt jellemző paraméterei szignifikáns (p<0,05) javulást mutattak a perkondicionált csoportban a kontrollhoz képest. A szérum-alanin-transzamináz-aktivitás és a májszövettani vizsgálatok, továbbá a májszöveti redox-homeosztázis vonatkozásában egyaránt szignifikánsan enyhébb károsodás volt megfigyelhető a perkondicionált csoportban a kontrollhoz képest. Következtetés:A perkondicionálás alkalmas lehet a máj ischaemiás-reperfúziós károsodásának mérséklésére. Introduction: Several techniques have been developed to reduce ischemic-reperfusion injury. A novel method is the remote ischemic perconditioning, applied parallel with target organ ischemia. Aim: The aim of the study was to determine the extent of liver ischemic-reperfusion injury via the application of this novel method. Methods: Male Wistar rats (n = 30, 10/group) were subjected to 60-minute partial liver ischemia and 60-minute reperfusion. Rats in the perconditioned group received conditioning treatment during the last 40 minutes of liver ischemia by infrarenal aortic clamping. Hepatic and lower limb microcirculation was monitored by laser Doppler flowmeter during reperfusion. After reperfusion, liver samples were taken for routine histological examination and redox-state assessment. Serum transaminase activities and liver tissue heat-shock protein-72 expression were measured. Results: Parameters of microcirculation showed significant (p<0.05) improvement in the perconditioned group in comparison with the control. Besides the significant improvement observed in the serum alanine amino-transferase activities, significantly milder tissue injury was detected histologically in the liver sections of the perconditioned group. Moreover, significant improvement was found in the redox-state parameters. Conclusion: Perconditioning may be a reasonable possibility to reduce liver ischemic-reperfusion injury

Levosimendan Administration in Limb Ischemia: Multicomponent Signaling Serving Kidney Protection

AIMS AND OBJECTIVES: Acute renal failure is a severe complication of lower extremity major arterial reconstructions, which could even be fatal. Levosimendan is a dual-acting positive inotropic and vasodilatory agent, which is suspected to have protective effects against cardiac ischemia. However, there is no data available on lower limb or remote organ ischemic injuries therefore the aim of the study was to investigate the effect of levosimendan on lower limb ischemia-reperfusion injury and the corollary renal dysfunction. METHODS: Male Wistar rats underwent 180 min bilateral lower limb ischemia followed by 4 or 24 hours of reperfusion. Intravenous Levosimendan was administered continuously (0.2mug/bwkg/min) throughout the whole course of ischemia and the first 3h of reperfusion. Results were compared with sham-operated and ischemia-reperfusion groups. Hemodynamic monitoring was performed by invasive arterial blood pressure measurement. Kidney and lower limb muscle microcirculation was registered by a laser Doppler flowmeter. After 4h and 24h of reperfusion, serum, urine and histological samples were collected. RESULTS: Systemic hemodynamic parameters and microcirculation of kidney and the lower limb significantly improved in the Levosimendan treated group. Muscle viability was significantly preserved 4 and 24 hours after reperfusion. At the same time, renal functional laboratory tests and kidney histology demonstrated significantly less expressive kidney injury in Levosimendan groups. TNF-alpha levels were significantly less elevated in the Levosimendan group 4 hours after reperfusion. CONCLUSION: The results claim a protective role for Levosimendan administration during major vascular surgeries to prevent renal complications

Muscle Fiber Viability, a Novel Method for the Fast Detection of Ischemic Muscle Injury in Rats

Acute lower extremity ischemia is a limb- and life-threatening clinical problem. Rapid detection of the degree of injury is crucial, however at present there are no exact diagnostic tests available to achieve this purpose. Our goal was to examine a novel technique - which has the potential to accurately assess the degree of ischemic muscle injury within a short period of time - in a clinically relevant rodent model. Male Wistar rats were exposed to 4, 6, 8 and 9 hours of bilateral lower limb ischemia induced by the occlusion of the infrarenal aorta. Additional animals underwent 8 and 9 hours of ischemia followed by 2 hours of reperfusion to examine the effects of revascularization. Muscle samples were collected from the left anterior tibial muscle for viability assessment. The degree of muscle damage (muscle fiber viability) was assessed by morphometric evaluation of NADH-tetrazolium reductase reaction on frozen sections. Right hind limbs were perfusion-fixed with paraformaldehyde and glutaraldehyde for light and electron microscopic examinations. Muscle fiber viability decreased progressively over the time of ischemia, with significant differences found between the consecutive times. High correlation was detected between the length of ischemia and the values of muscle fiber viability. After reperfusion, viability showed significant reduction in the 8-hour-ischemia and 2-hour-reperfusion group compared to the 8-hour-ischemia-only group, and decreased further after 9 hours of ischemia and 2 hours of reperfusion. Light- and electron microscopic findings correlated strongly with the values of muscle fiber viability: lesser viability values represented higher degree of ultrastructural injury while similar viability results corresponded to similar morphological injury. Muscle fiber viability was capable of accurately determining the degree of muscle injury in our rat model. Our method might therefore be useful in clinical settings in the diagnostics of acute ischemic muscle injury

Remote ischemic perconditioning-a simple, low-risk method to decrease ischemic reperfusion injury: Models, protocols and mechanistic background. A review

Interruption of blood flow can cause ischemic reperfusion injury, which sometimes has a fatal outcome. Recognition of the phenomenon known as reperfusion injury has led to initial interventional approaches to lessen the degree of damage. A number of efficient pharmacologic agents and surgical techniques (e.g., local ischemic preconditioning and postconditioning) are available. A novel, alternative approach to target organ protection is remote ischemic conditioning triggered by brief repetitive ischemia and reperfusion periods in distant organs. Among the different surgical techniques is so-called remote ischemic perconditioning, a method that applies short periods of ischemic reperfusion to a distant organ delivered during target organ ischemia. Although ischemic reperfusion injury is reduced by this technique, the explanation for this phenomenon is still unclear, and approximately only a dozen reports on the topic have appeared in the literature. In our study, therefore, we investigated the connective mechanisms, signal transduction, and effector mechanisms behind remote perconditioning, with a review on molecular background and favorable effects. In addition, we summarize the various treatment protocols and models to promote future experimental and clinical research

Akut kritikus ischaemia az alsó végtagon [Acute and critical ischemia of the lower limb]

Acute limb arterial occlusion has great clinical significance due to its high mortality and complication rates. Its diagnosis is easy; however staging after long-term occlusions can be very difficult with lack of exact criteria. It is crucial, since reversible stage should undergo revascularization, while with irreversible stage only amputation is curative. Due to occlusion, long-term ischemia occurs, resulting in injury of the muscle fibers and endothelial cells. In case of revascularization the reperfusion causes more damage, than ischemia alone locally and initiates a remote organ injury. The aim of the review is to summarize the knowledge and fact and focus on some exact methods or parameters which can determine the degree of injury. One of these methods is a new approach which is the use of enzyme-histochemical reactions, and could give rapid, precise results even preoperatively regarding tissue viability. Routine clinical application of it is predictable after proper standardization