Prolonged Period Of Ischemia Research Articles

Successful reversal of acute kidney failure by ultrasound-accelerated thrombolysis of an occluded renal artery.

Purpose. To describe the treatment of renal artery thrombosis with ultrasound-accelerated thrombolysis and discuss the management of prolonged renal ischemia. Case. A 76-year-old patient with a single functional kidney, mild chronic renal impairment, and a recent history of endovascular repair of a thoracoabdominal aneurysm with an aortic branch graft presented with acute flank pain, anuria, and renal failure. The side branch from the aortic stent graft to his single, right, functional kidney appeared to be completely thrombosed. Symptoms had started after cessation of oral anticoagulants because of a planned mastectomy for breast cancer. After identification of the occlusion, ultrasound-accelerated thrombolysis was started 19 hours after the onset of anuria. Angiography, 4 hours after beginning of therapy, already showed partial dissolution of the thrombus and angiographic control after 18 hours showed complete patency of the renal artery side branch. Despite a long period of ischemia, renal function was completely recovered. Conclusion. In patients with acute renal ischemia due to thrombosis of the renal artery, complete recovery of function can be achieved with ultrasound-accelerated thrombolysis, even after prolonged periods of ischemia.

Bedside Diagnosis of Mitochondrial Dysfunction After Malignant Middle Cerebral Artery Infarction

The study explores whether the cerebral biochemical pattern in patients treated with hemicraniectomy after large middle cerebral artery infarcts reflects ongoing ischemia or non-ischemic mitochondrial dysfunction. The study includes 44 patients treated with decompressive hemicraniectomy (DCH) due to malignant middle cerebral artery infarctions. Chemical variables related to energy metabolism obtained by microdialysis were analyzed in the infarcted tissue and in the contralateral hemisphere from the time of DCH until 96 h after DCH. Reperfusion of the infarcted tissue was documented in a previous report. Cerebral lactate/pyruvate ratio (L/P) and lactate were significantly elevated in the infarcted tissue compared to the non-infarcted hemisphere (p < 0.05). From 12 to 96 h after DCH the pyruvate level was significantly higher in the infarcted tissue than in the non-infarcted hemisphere (p < 0.05). After a prolonged period of ischemia and subsequent reperfusion, cerebral tissue shows signs of protracted mitochondrial dysfunction, characterized by a marked increase in cerebral lactate level with a normal or increased cerebral pyruvate level resulting in an increased LP-ratio. This biochemical pattern contrasts to cerebral ischemia, which is characterized by a marked decrease in cerebral pyruvate. The study supports the hypothesis that it is possible to diagnose cerebral mitochondrial dysfunction and to separate it from cerebral ischemia by microdialysis and bed-side biochemical analysis.

Fast Track Extubation Post Coronary Artery Bypass Graft: A Retrospective Review of Predictors of Clinical Outcomes*

Introduction: Fast track (FT) cardiac surgery and early extubation (EE) are aimed at safe and effective rapid post-operative progression to discharge, and have been practiced for more than two decades. Their goal is to optimize patient care perioperatively in order to decrease costs without negatively affecting morbidity and mortality. However, the factors that predict successful EE are poorly understood, and patients with significant co-morbidities are frequently excluded from protocols. We hypothesize that independent of disease severity, early extubation leads to shorter hospital stays and can be performed safely without negatively affecting outcomes. Materials and Methods: We performed a retrospective review of 919 patients who underwent coronary artery bypass grafting (CABG) at the Southern Arizona Veteran’s Affairs Health Care System medical center over 7 years. We collected pre-operative data regarding patients’ NYHA classification, presence and severity of cerebral vascular disease, peripheral vascular disease, pulmonary disease, diabetes and hypertension. Intra-operative variables were also recorded including ASA scores, ischemic times, and time to extubation. Finally, post-operative variables such as rates of reintubation and tracheotomy, and both length of ICU and total hospital stay were also compared. Results: Prolonged periods of ischemia were found to predict a delayed extubation (HR = 0.992; CI = 0.988 - 0.997, p = 0.0015) while small body surface area (HR = 1.57; CI = 1.13, 2.17, p = 0.007) and higher pre-operative functional status of the patient, such as independent versus dependent status (HR =1.68; CI = 1.30 - 2.16, p = 1.33; CI = 1.03 - 1.70, p = 0.03) were found to be associated with earlier extubation. The early extubation (EE) group (those extubated in less than the median 7.3 hours) had an average hospital stay of 5.1 ± 4.0 days, versus 7.8 ± 8.1 days in the delayed group (>4 hours), p Conclusions: In our study population, pre-operative functional class and total body surface area predicted those patients able to tolerate early extubation after cardiac surgery. Prolonged ischemia resulted in delayed extubation. Patients that were extubated in less than 4 hours had shorter ICU and hospitalization stays, while there was no significant difference between the two groups in rate of reintubation or tracheotomy.

Protective Effects of Reducing Renal Ischemia-reperfusion Injury During Renal Hilar Clamping: Use of Allopurinol as a Nephroprotective Agent

To investigate the relationship between renal ischemia injury and concentrations of 8-isoprostane in a rat kidney model during renal hilar clamping and their correlation with the administration of allopurinol before clamping. Reperfusion injury occurs after the reintroduction of blood flow after a prolonged period of ischemia. Thought to be due to oxygen free radicals released by the endothelial, mitochondrial, and parenchymal cells, this process leads to a cascade of events whereby infiltrative leukocytes generate cytokines and reactive oxygen species. The present study was performed in 2 parts. Our primary objective was to first develop a method of quantitating the renal damage using a prostaglandin compound formed invivo, specifically isoprostane. After the development of this animal model of quantitating renal injury, our second objective was to apply this model and investigate allopurinol's nephroprotective abilities. A microdialysis probe was inserted into the renal parenchyma of rats to allow continuous dialysis and collection of the effluent for isoprostane levels. After clamping of the renal vessels to induce ischemia, the interstitial effluent from the probe was collected and subsequently analyzed for 8-isoprostane levels with and without allopurinol pretreatment. Clamping of the renal hilum in this rat model significantly increased 8-isoprostane levels. After 60 minutes of clamp time, the largest absolute increase in 8-isoprostane levels resulted, representing a 3.2-fold increase from baseline. However, the rats that had been pretreated with allopurinol demonstrated significantly less isoprostane levels, to baseline levels. Allopurinol has demonstrated significant benefits by reducing reperfusion injury in rat kidneys, as demonstrated by the use of 8-isoprostane as a tool for the real-time measurement of ischemic injury.

Remote ischaemic preconditioning versus no remote ischaemic preconditioning for vascular and endovascular surgical procedures.

Despite advances in perioperative care, elective major vascular surgical procedures carry a significant risk of morbidity and mortality. Remote ischaemic preconditioning is initiated by brief, non-lethal periods of ischaemia in a vascular bed different from the one which will be subjected to ischaemic insult during surgery. It has the potential to provide local tissue protection from further prolonged periods of ischaemia. The aim of this review was to compare the outcomes from vascular and endovascular surgical procedures with and without the use of remote ischaemic preconditioning. The Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (June 2011) and CENTRAL (2011, Issue 2). The authors searched MEDLINE via PubMed (July 2011), EMBASE (June 2011), and Science Citation Index Expanded (July 2011). We considered for inclusion all randomised controlled trials that evaluated the role of remote ischaemic preconditioning in reducing mortality and systemic injury in patients undergoing open vascular or endovascular surgery. We collected the data on characteristics of the trial, methodological quality, the remote ischaemic preconditioning stimulus used, mortality, morbidity, operating time and hospital stay from each trial. We analysed the data with both the fixed-effect and the random-effects models using RevMan analysis. For each outcome we calculated the risk ratio (RR) or mean difference with 95% confidence interval (CI) based on an intention-to-treat analysis. We included four studies with a total of 115 patients randomised to undergo a vascular procedure with remote ischaemic preconditioning and 117 patients randomised to have the procedure without remote ischaemic preconditioning. None of the trials were of low risk of bias. There was no significant difference in mortality between the two groups (RR 1.70, 95% CI 0.51 to 5.72). Similarly, there was no statistically significant difference between the two groups for all other outcomes except reduced risk of myocardial infarction in the remote ischaemic preconditioning group, which was significant by the fixed-effect model (RR 0.31, 95% CI 0.10 to 0.90) but not by the random-effects model (RR 0.34, 95% CI 0.11 to 1.08). This positive effect was from the results of only one trial and was not consistently observed. Furthermore, it was noted that there was an observed trend of high incidence of unplanned critical care admission in the remote ischaemic preconditioning group, although this was not statistically significant (RR 2.15, 95% CI 0.87 to 5.33). Based on current evidence from small pilot trials, there are too few data to be able to say whether remote ischaemic preconditioning has any beneficial or harmful effects. The safety of this technique needs to be confirmed in adequately powered trials. Therefore, further randomised trials on this technique are required.

Update on Ischemia-Reperfusion Injury for the Plastic Surgeon

Ischemia-reperfusion injury occurs when tissue is reperfused following a prolonged period of ischemia. It is a subject of interest to plastic surgeons involved in replantation, free tissue transfer, and composite tissue allotransplantation, as it can have a significant impact on the overall success of these procedures. The purpose of this article is to review the recent progress in the investigation of ischemia-reperfusion injury in skeletal muscle and skin and to highlight the potential clinical implications of therapeutic interventions aimed at reducing ischemia-reperfusion injury.

Cardioprotection from ischaemia–reperfusion injury by a novel flavonol that reduces activation of p38 MAPK

Oxidative stress, activation of intracellular protein kinases and cardiomyocyte apoptosis are known mediators of cardiac ischaemia/reperfusion injury. The sites at which NP202, a novel water soluble pro-drug of 3′,4′-dihydroxyflavonol (DiOHF), acts in this cascade to cause cardioprotection are unknown. In this study we examined the ability of NP202 to reduce infarct size after a prolonged period of ischaemia and reperfusion. In addition, we tested whether NP202 inhibits pro-apoptotic signalling, apoptosis and inflammation following myocardial ischaemia and reperfusion. Sheep were anaesthetised, the heart exposed and the 2nd branch of the left anterior descending coronary artery isolated. The artery was occluded for 3 h and, five minutes before 3 h of reperfusion was commenced, sheep were treated with intravenous vehicle or NP202. At the end of reperfusion infarct size was measured and normal left ventricle, non-infarcted area-at-risk and infarcted myocardium were collected to identify polymorphonuclear leukocytes (PMN) or apoptotic cells (TUNEL-positive), or assessed for activation of mitogen-activated protein kinase (MAPK) pathways by Western blot analysis. Compared with vehicle treatment, NP202 reduced infarct size (− 20 ± 4%, P < 0.05) and decreased the number of PMNs and TUNEL-positive cells in the area-at-risk (− 35 ± 16% and − 52 ± 19%, respectively) and infarcted tissue (− 57 ± 9 and − 81 ± 5%, respectively, P < 0.05). Furthermore, NP202 significantly reduced I/R-induced elevated p38 MAPK phosphorylation (by 67 ± 4%, P < 0.05) in the area-at-risk zone. In conclusion, the novel aqueous flavonol NP202 provided significant cardioprotection from clinically relevant prolonged myocardial ischaemia when administered just before reperfusion. Efficacy of NP202 was also associated with reduced p38 MAPK activation, inflammation and apoptotic cell death.

Postconditioning reduces infarct size and cardiac myocyte apoptosis via the opioid receptor and JAK-STAT signaling pathway

Brief intermittent episodes of ischemia and reperfusion could reduce infarct size, a phenomenon called "postconditioning" at the onset of reperfusion after a prolonged period of ischemia. To investigate whether the opioid receptors and signaling factor JAK-STAT might be responsible for the cardioprotection in ischemic postconditioning, and the possible molecular machinery of cardioprotection. Hundred and twenty healthy New Zealand rabbits were divided into six groups. The myocardial infarct size, cardiac myocyte apoptosis, BCL-2 and P-Stat3 protein expression were tested in the current study. The results suggested that ischemic postconditioning might increase BCL-2 protein expression by activating the opioid receptors and JAK-STAT signaling pathway, and also to reduce ischemia-reperfusion-induced cardiomyocyte apoptosis and to play a key role in myocardial protection. However, further research still needs to be done to unravel the underlying mechanisms.

Current protective strategies in liver surgery

During liver resection surgery for cancer or liver transplantation, the liver is subject to ischaemia (reduction in blood flow) followed by reperfusion (restoration of blood flow), which results in liver injury [ischemia-reperfusion (IR) or IR injury]. Modulation of IR injury can be achieved in various ways. These include hypothermia, ischaemic preconditioning (IPC) (brief cycles of ischaemia followed by reperfusion of the organ before the prolonged period of ischaemia i.e. a conditioning response), ischaemic postconditioning (conditioning after the prolonged period of ischaemia but before the reperfusion), pharmacological agents to decrease IR injury, genetic modulation of IR injury, and machine perfusion (pulsatile perfusion). Hypothermia decreases the metabolic functions and the oxygen consumption of organs. Static cold storage in University of Wisconsin solution reduces IR injury and has prolonged organ storage and improved the function of transplanted grafts. There is currently no evidence for any clinical advantage in the use of alternate solutions for static cold storage. Although experimental data from animal models suggest that IPC, ischaemic postconditioning, various pharmacological agents, gene therapy, and machine perfusion decrease IR injury, none of these interventions can be recommended in clinical practice. This is because of the lack of randomized controlled trials assessing the safety and efficacy of ischaemic postconditioning, gene therapy, and machine perfusion. Randomized controlled trials and systematic reviews of randomized controlled trials assessing the safety and efficacy of IPC and various pharmacological agents have demonstrated biochemical or histological improvements but this has not translated to clinical benefit. Further well designed randomized controlled trials are necessary to assess the various new protective strategies in liver resection.

Effect of preischemic β-adrenoceptor stimulation on postischemic contractile dysfunction

Aims Short periods of preischemic β-adrenoceptor stimulation protect hearts against postischemic left ventricular dysfunction. It was the aim of this study to decide whether this procedure mimics ischemic preconditioning by the generation of preischemic hemodynamic and energetic stress or whether it represents an endogenous phenomenon and to investigate the influence of age and hypertension. Main methods Isolated rat hearts were investigated ex vivo by Langendorff perfusion and exposed to an established ischemia/reperfusion protocol (45 min no-flow ischemia and 90 min reperfusion). Left ventricular developed pressure (LVDP), rate pressure product, and ± d P/d t were analyzed. Key findings Isoprenaline concentration dependently increased LVDP up to 40 ± 15 mm Hg (approximately EC 50 of 9.9 ± 0.5 nM). Isoprenaline given prior to ischemia attenuated the subsequent postischemic ventricular dysfunction (approximately EC 50 of 1.4 ± 0.2 pM). However, concentrations high enough to improve LVDP in normoxic hearts did not improve postischemic recovery albeit a significant reduction of hypercontraction-induced cell damage. The effect on functional recovery was attenuated by atenolol, H89, and wortmannin suggesting that β-adrenoceptor stimulation, protein kinase A, and PI 3-kinase activation are involved. The effect was conserved in hearts from 13 month old rats but lost in age-matched spontaneously hypertensive rats. Significance The study identifies preischemic β-adrenoceptor stimulation as a pharmacological preconditioning protocol that does not simply mimic classical ischemic preconditioning by induction of hemodynamic or energetic stress prior to a prolonged ischemic period. The observed loss of effectiveness in hypertensives may contribute to the reduced ischemic tolerance of hypertensives.

Abstract 1900: Preconditioning in Cynomolgus Monkey Heart Protects Against Both Ischemic and Reperfusion Injury

Ischemic preconditioning (IPC) and postconditioning (IPoC) are equally cardioprotective in some species tested but IPoC has been less protective in others. Although IPoC decreases infarct size in humans, no comparable data exist for IPC making a comparison impossible. We therefore compared IPoC and IPC in sub-human primate hearts which would be expected to most closely mimic that of humans. Cynomolgus monkeys underwent a 90-min occlusion of a coronary artery and 4h of reperfusion. In IPC 2 cycles of 10-min coronary occlusion/10-min reperfusion preceded the 90-min occlusion, and in IPoC 6 cycles of 30-sec reperfusion/30-sec coronary reocclusion were performed immediately after the 90-min occlusion. The regression line for the infarct-risk zone plot was very linear (r=0.99) and intersected the risk zone axis at 0.82 cm 3 . Collateral flow averaged only 6.6% of preocclusion flow and did not influence infarction. In control monkeys 44% of the risk zone infarcted indicating cynomolgus myocardium is much more resistant to infarction than that of rabbits or rats. While IPC reduced infarct size to near zero (2.4±0.9% infarction of risk zone), IPoC was much less protective (27.5±4.8% infarction of risk zone). Increasing the number of IPoC cycles to 10 did not increase salvage. When wortmannin was administered at the end of the ischemic period to block any protection that IPC might elicit during reperfusion, infarct size increased to only 28%. These findings suggest that only half of IPC’s protection in monkey heart derives from prevention of cell death during reperfusion. The other half of IPC’s salvage would have derived from suppression of cell death during the prolonged ischemic period. If human heart is similar to cynomolgus heart, then interventions applied at reperfusion such as IPoC may be much less effective than would be predicted from the non-primate animal studies. Effective clinical salvage may require cardioprotective interventions that target both the ischemic phase as well as reperfusion injury.

Role of hypothermia in hemorrhagic shock

Hemorrhagic shock that leads to cardiovascular collapse does not respond well to conventional methods of cardiopulmonary resuscitation. Even when the source of bleeding can be controlled and the circulation restored, cerebral ischemia lasting for >5 min invariably results in severe brain damage. Often the underlying injuries are reparable but the patient dies of irreversible shock. In this setting, strategies to maintain cerebral and cardiac viability long enough to gain control of hemorrhage and restore intravascular volume could be life-saving. This requires an entirely new approach to the problem, with emphasis on rapid total body preservation, repair of injuries during metabolic arrest, and controlled resuscitation, so-called emergency preservation and resuscitation. Currently, hypothermia is the most effective method for preserving cellular viability during prolonged periods of ischemia. Herein, the authors describe the rationale behind the development of this strategy, its impact on various cellular...

Novel Pharmacologic Strategies to Protect the Liver from Ischemia- Reperfusion Injury

Ischemia and reperfusion (I/R) injury develops when blood flow is interrupted for a long period of time and then restarted. In the liver, this type of damage occurs in clinical settings such as liver transplantation and hepatic resection. Given the shortage of donor organs it is essential to maximize the use of sub-optimal organs, those previously rejected due to elevated risk of malfunction, and to increase split-liver transplantation interventions. Therefore, the development of strategies that preserve organ viability and promote liver regeneration is urgently needed. As observed for other organs, a brief period of ischemia followed by short reperfusion before the surgical procedure significantly increases liver resistance towards prolonged periods of ischemia. This phenomenon is known as ischemic preconditioning, and is the only protective strategy that has reached clinical practice. Recently, intensive research has improved our understanding of the mechanisms involved in I/R liver injury, and the biologic bases of ischemic preconditioning. This knowledge has generated relevant patented advances in the field, including the targeted inhibition of pro-apoptotic pathways, the interference with neutrophil activation, and the identification of cytoprotective cytokines. Here, we briefly review the mechanisms of hepatic ischemic damage, and present the most promising pharmacologic approaches against I/R injury. This article also includes recent patents on this topic.

Ischemic postconditioning and myocardial preservation

随着心脏外科手术和介入治疗的增加,人们越来越重视其中的主要病理生理过程--心肌缺血再灌注损伤(myocardium ischemic-reperfusion inury,MIRI).MIRI是指心肌缺血一定时间后即使恢复血液灌注,仍将引起心肌功能障碍和结构损害,表现为致死性再灌注损伤、心肌顿抑、心律失常和能量代谢改变.其发病机制仍未完全阐明,通常认为与氧自由基、钙超载、中性粒细胞、微血管损伤和能量代谢障碍等有关.近年来对其发生机制和防治方法的研究越来越深入,发现缺血后处理(ischemic postconditioning,IPO)[1]有很好的心肌保护作用.现就IPO对心肌缺血和再灌注损伤的保护作用、可能机制及其意义作一综述。

Signaling Mechanisms in Ischemic Preconditioning

See related article, pages 878–883 The cardiac “warm up” phenomenon, described more than 50 years ago in patients with coronary artery disease, refers to improvement in cardiac symptoms and physical performance following exposure to short periods of ischemia.1 Several mechanisms, such as adaptive reduction in oxygen consumption by the ischemic myocardial region, improved oxygen supply via collateral recruitment or dilation of the stenotic vessel, and activation of an intrinsic phenomenon called ischemic preconditioning (IPC) have been proposed to account for this phenomenon. IPC refers to a process in which brief periods of ischemia improves the ability of the heart to tolerate subsequent prolonged ischemic periods.3 It was first identified in the heart in 1986 by Murry et al,2 and has since been demonstrated in various experimental and animal models.3 Several triggers have been proposed for IPC, including adenosine, bradykinin, protaglandins, opiod receptors, nitric oxide, and Ca2+.4 These triggers lead to the activation of several intracellular pathways that ultimately protect myocardial cells against injury. Although the details of these pathways have not been totally characterized, mitochondria have been shown to be key mediators of IPC. Specifically, the opening of a mitochondrial channel, called the mitochondrial ATP-sensitive potassium channel or mitoKATP is believed to be critical for the induction of IPC; drugs that activate this channel protect against ischemia and inhibitors of mitoKATP reverse these protective effects.5 The signaling pathways that lead to the activation of mitoKATP are still under investigation.5 In a recent article, Oldenburg et al demonstrated that in isolated rabbit adult cardiomyocytes, bradykinin increased the levels of reactive oxygen species (ROS) and this effect was reversed by inhibitors of both mitoK …

Preconditioning Enters the Era of “Physiological Proteomics”

See related article, pages 706–714 Cardiac ischemic preconditioning was first described in 1986 by Murry et al,1 who reported that brief periods of ischemia dramatically reduced myocardial infarct size caused by a subsequent, more prolonged period of ischemia. Since the initial report, the phenomenon has been shown to occur in many cell types, including human cardiomyocytes,2 raising hopes that ischemic injury to human myocardium might be prevented. The discovery that pretreatment with several pharmacological agents including adenosine, diazoxide, bradykinin, and insulin could also precondition the heart and prevent subsequent ischemic damage, provided an as yet unfulfilled promise that drugs could be developed which limit cardiac cell death caused by myocardial infarction in patients.3 As is always true of complex physiological problems, it is likely that understanding the fundamental molecular mechanism of preconditioning will be necessary to develop effective medical therapies. In recent years the mitochondrion has become the subject of intense scrutiny for the key to preconditioning. The formation of the mitochondrial permeability transition pore (mPTP) is an essential step in ischemia-induced cardiomyocyte death because its formation accounts for collapse of the mitochondrial membrane potential and failure of oxidative phosphorylation to produce ATP which leads to cardiomyocyte death. Furthermore, inhibitors and activators of the mPTP inhibit or favor preconditioning, respectively, suggesting both the mPTP and the mitochondrion are key participants.3,4 Further evidence that the mitochondrion is key to the initial physiological response to preconditioning is provided by Arrell et al in this issue of Circulation Research , who used a proteomic approach to measure changes in the amount of cardiomyocytes undergoing preconditioning.5 Relatively few of the proteins they identified changed at all. Of the 19 that did, about half were classified as mitochondrial proteins. The purpose of this editorial is not to review the …

MCP-1 Parallels Inflammatory and Regenerative Responses in Ischemic Muscle

Monocyte chemotactic protein-1 (MCP-1) is important in macrophage recruitment and activation. However, the magnitude and temporal sequence of MCP-1 expression in relation to tissue injury and regeneration following ischemic injury remains unknown. Hind limb ischemia was induced by femoral artery excision (FAE) in C57Bl/6J mice; a sham surgery was performed on the contralateral leg. Muscle lysates were used to measure MCP-1 and activities of creatine kinase, lactate dehydrogenase, and myeloperoxidase. Histology and immunohistochemistry were used to localize inflammation and MCP-1. FAE resulted in a prolonged period of ischemia and the administration of MCP-1 did not alter the restoration of perfusion. One day after femoral artery excision, extensive muscle necrosis and neutrophils were prevalent throughout the musculature of the lower leg. By 3 days, a mononuclear cell infiltrate predominated in association with robust muscle regeneration as indicated by myoD expression. Concomitantly, myeloperoxidase was maximally increased. Muscle enzymes (creatine kinase and lactate dehydrogenase) were maximally decreased within 3 days and returned to baseline levels by day 14, a time course consistent with injury and regeneration observed by histology. In parallel with these inflammatory and regenerative events, MCP-1 in muscle was maximally increased at day 3. By immunohistochemistry, MCP-1 was within vascular endothelial cells and infiltrating macrophages in areas of ischemic injury. The transient increases and selective tissue distribution of MCP-1 during early inflammation and muscle regeneration support the hypothesis that this cytokine participates in the early reparative events preceding the restoration of vascular perfusion following ischemic injury.

Successful Revascularization Following Near-Complete Amputation of the Tongue

Successful salvage of the tongue following near or complete traumatic amputation is a rare event. We now report only the second reported successful case of a revascularization of a near or complete amputation of the tongue while in the setting of massive facial trauma. Microscopic revascularization was performed utilizing the left lingual artery and right lingual vein, and despite a prolonged ischemic period, a functional tongue was salvaged. Our patient demonstrated that the tongue can survive up to 16 hours of ischemia. The successful replantation also suggests that arterial blood flow through a single lingual artery and a contralateral single vein may be adequate to perfuse the entire mobile tongue, despite the previously thought avascular median fibrous septum. Tongue revascularization can be performed in the setting of massive facial trauma and large-volume fluid resuscitation.

Trafficking of the Membrane Type-1 Matrix Metalloproteinase in Ischemia and Reperfusion

The matrix metalloproteinases (MMPs) contribute to regional remodeling after prolonged periods of ischemia and reperfusion (I/R), but specific MMP types activated during this process remain poorly understood. A novel class, the membrane-type MMPs (MT-MMPs), has been identified in the myocardium, but activity of these MMP types has not been assessed in vivo, particularly during I/R. Pigs (30 kg, n=8) were instrumented with microdialysis catheters to measure MT1-MMP activity in both ischemic and nonischemic (remote) myocardium. A validated MT1-MMP fluorogenic substrate was infused through the microdialysis system, and changes in fluorescence were reflective of MT1-MMP activity at steady state, during ischemia (90 minutes), and during reperfusion (120 minutes). At peak ischemia, MT1-MMP activity was increased by >40% in the ischemic region, with no change in the remote region, which persisted with reperfusion (P<0.05). After I/R, MT1-MMP abundance was increased by >50% (P<0.05). Differential centrifugation revealed that the endosomal fraction (which contains subcellular organelles) within the ischemic myocardium was associated with a >135% increase in MT1-MMP (P<0.05). Furthermore, in an isolated left ventricular myocyte model of I/R, hypoxia (simulated ischemia) induced a >70% increase in MT1-MMP abundance in myocytes, and confocal microscopy revealed MT1-MMP internalization during this time period and reemergence to the membrane with reperfusion. These unique results demonstrate that a specific MMP type, MT1-MMP, is increased in abundance and activity with I/R and is likely attributed, at least in part, to changes in intracellular trafficking.

General session V Moderated by Yashihiko Maehara: Reduction of Ischemia‐Reperfusion Injury to Skin Flaps by Monoclonal Antibody to Leukocyte Endothelial Adhesion Molecule‐1

Aim: Ischemia‐reperfusion (I‐R) injury continues to be a problem for successful free tissue transfer and replantation after prolonged periods of ischemia. It has been shown that leukocytes and vascular endothelial cells release a variety of inflammatory mediators during reperfusion after ischemia. The leukocyte endothelial adhesion molecule‐1 (LECAM‐1) is a ligand on the endothelium for some of the adhesion receptors on leukocytes. The purpose of this study was to evaluate the blockage of leukocyte‐endothelial adhesion by a monoclonal antibody (MAb) to LECAM‐1 in skin flaps to prevent I‐R injury in rats.Methods: Male SD rats (225–250 g) were used. A skin flap (45 × 30 mm) supplied by the superficial epigastric A&amp;V including the femoral vessels was isolated unilaterally. The femoral vessels were cross‐clamped the epigastric vessels for 9 hours of ischemia. Animals in treated group received MAb to LECAM −1 i.v. 15 minutes prior to reperfusion; those in the control group received normal saline. Skin flap viability was assessed by tracing the outline of viable and nonviable areas. Data were collected for the following 7 days. These data were corroborated with histological evidence on comparable areas of the flap.Results: Tracing analysis revealed average flap survival area of about 90% in treated group and about 20% in control group (p &lt; 0.05). Histopathologically, few inflammatory changes could be observed in treated group, while marked damage was observed in control group.Conclusions: From this study, we concluded that treating skin flaps with Mab to LECAM ‐1 was effective for I‐R injury after 9 hours of warm ischemia.