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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Peripheral obstructive arterial disease (POAD) of the lower limbs is the third main complication of atherosclerosis, after coronary artery disease and cerebrovascular disease. In 15-20% of cases POAD have an unfavourable evolution toward critical leg ischemia (CLI). This clinical condition is characterized by the onset of rest pain and/or trophic cutaneous lesions until gangrene appears. In some cases amputation is needed. The pathophysiological, clinical and therapeutic aspects of CLI were recently discussed in two Consensus Conferences held in Berlin in 1989 and in Rudesheim in 1991, with the elaboration of a final draft published on circulation. CLI appears when peripheral perfusion critically decreases due to macro and microcirculatory alterations. Atherosclerotic plaque is the primum movens, but often there are more plaques in sequence along the ilio-femoro-popliteal axis. The pathophysiological and clinical consequences are more severe if the stenosis is haemodynamically important, after a rapid progression of plaque growth or when thrombotic complications develop. The reduction in distal perfusion induces troubles in the microcirculation and an embalancement between the microvascular defense system (MDS) and the microvascular flow regulating system (MFRS) with endothelial dysfunction, platelet and leucocytes activation, worsening of blood viscosity due to the increase in fibrinogen levels and to the red cells deformability changes, activation of coagulation and impairment of fibrinolysis. So, a vicious circle appears with further worsening of distal perfusion and onset of trophic lesions. A further worsening of CLI can derive from local recurrent infections particularly frequent in diabetic patients.
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PMID:[The physiopathology of critical ischemia of the lower limbs]. 811 25

Coronary heart disease, stroke and peripheral arterial disease are the major causes for death and disability in industrialized countries. These diseases have a common cause: Their development is based on atherosclerotic changes of blood vessels, induced by risk factors such as elevated values of lipoproteins and fibrinogen. There is no doubt that the risk factors mentioned above are even related to a dramatically deterioration of the hemorheologic pattern, thus reducing perfusion. Due to this massage there are attempts to treat ischemia via hemorheological intervention. Although a number of different methods is available--hemodilution, defibrinogenation or oral medication--it was not possible to improve the hemorheologic pattern fast, safe, and efficient to date. A new treatment modality, utilizing the heparin-induced extracorporeal LDL precipitation (HELP), now offers the possibility to obtain therapeutical success not only in cases of severe hypercholesterolemia but even in the field of hemorheology: Using HELP a safe and rapid reduction of lipid fractions and fibrinogen has become feasible, thus providing an acute improvement of red cell aggregation and filterability of blood cells, whole blood and plasma viscosity and thereby of microcirculation. As it is known that cerebrovascular diseases are related to disturbances of the hemorheological situation, the HELP system is used at the Department of Neurology, Karl-Franzens University of Graz, for the treatment of acute stroke, cerebral multi-infarct disease but even in cases of peripheral arterial disease.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Heparin-induced extracorporeal LDL precipitation (HELP): a new therapeutic intervention in cerebrovascular diseases and peripheral arterial occlusive disease]. 815 30

Hematologic and rheologic variables were examined in a group of 13 horses with intestinal colic and a control group of 6 horses. All horses had been recently transported to the veterinary teaching hospital, and blood samples were obtained during initial examination. There were no significant differences in blood neutrophil count or plasma fibrinogen concentration between the groups, and PCV was significantly increased in horses with intestinal colic. Cell filterability was measured by passing uniform concentrations of blood, erythrocytes, and neutrophils through micropore filters. There were no significant differences between the control and intestinal colic groups in filterability of erythrocytes. Significant (P < 0.05) prolongation in filterability of blood and neutrophils was observed in the group of horses with intestinal colic, compared with the control group. This neutrophil change, indicative of decreased neutrophil deformability, corresponded with severity of the illness. Horses that failed to survive the intestinal colic episode had significantly (P < 0.05) prolonged blood and neutrophil filterability, compared with horses that survived intestinal colic. These findings indicate that deformability of neutrophils decreases in horses with intestinal colic, possibly a result of endotoxin-induced activation. This change can further impede microvascular blood flow that is altered in association with intestinal ischemia.
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PMID:Blood cell deformability in horses with intestinal colic. 819 52

The loss of distal tissue perfusion sufficient for limb salvage following restoration of inflow to an acutely ischemic extremity has been referred to as the "no-reflow" phenomenon. We hypothesized that patients with no reflow and limb-threat ischemia might benefit from prolonged postoperative intra-arterial infusion of the thrombolytic agent urokinase (UK). Twelve patients with arteriographic and clinical evidence of no reflow following a lower extremity arterial thrombectomy and/or bypass procedure were treated with a continuous intra-arterial UK infusion in the immediate postoperative period. The mean duration of UK infusion was 47 hours (range 15 to 112 hours). The mean rate of infusion was 58,000 units/hr (range 30,000 to 100,000 units/hr). Seven patients required transfusion for bleeding from the treated extremity (mean 3.4 units packed cells) and one required reoperation for a groin hematoma. Plasma fibrinogen levels remained within the normal range in all patients, and no systemic bleeding complications were encountered. The intra-arterial UK infusion resulted in limb salvage in 7 of 12 patients. Six patients have viable, functional extremities at a mean follow-up interval of 24.9 months (range 6.4 to 49.7 months). One patient required below-knee amputation 6 months after treatment for progressive ischemia. The other five patients required below-knee amputation during the same hospitalization after UK failed to restore distal perfusion. The postoperative period is widely considered to be a contraindication to thrombolytic therapy. Our experience indicates that while UK may cause bleeding from the treated extremity, which in some cases requires transfusion, there is no evidence of systemic fibrinolysis or systemic hemorrhage.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Continuous postoperative intra-arterial urokinase infusion in the treatment of no reflow following revascularization of the acutely ischemic limb. 819 3

Blood platelets play a fundamental role in hemostasis and thrombosis. The physiological role of platelets is to preserve the integrity of the cardiovascular system such that upon injury platelets are activated and serve to interrupt a potentially deleterious situation (i.e., hemorrhage). However, platelets are also involved in the pathophysiology of thrombosis in which the normal repair process is grossly exacerbated, resulting in interruption of blood flow to vital tissues. Thus, a critical balance exists between the normal function of blood platelets to preserve tissue function and a pathophysiological function in which tissue is damaged due to thrombosis and subsequent ischemia. Numerous anti-platelet agents have been developed in an attempt to interrupt the thrombotic process without severely compromising the hemostatic state of patients. This article will be devoted to a discussion of a commonly utilized anti-thrombotic agent, aspirin, as well as a class of newer, possibly more effective anti-thrombotic agents referred to collectively as fibrinogen receptor antagonists.
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PMID:Interruption of thrombosis and hemostasis by anti-platelet agents. 821 Sep 40

The etiology of venous ulceration is far more complex than Homans' theory of stagnation and hypo-oxygenation. Indeed, studies have shown that flow in lipodermatosclerotic limbs is actually faster than normal. We suggest, therefore, that the terms "stasis dermatitis" and "stasis ulcer" be dropped from medical parlance. The term "lipodermatosclerosis with ulceration" as used by the British, or simply "venous ulcer," would seem more appropriate. Venous hypertension, produced by incompetence of deep and communicating vein valves and thrombosis of segments of the deep system, is closely correlated with the development of venous ulcers. Precisely how this venous hypertension translates into ulceration is unclear. Burnand et al showed that fibrin cuffs are deposited around the capillaries in lipodermatosclerotic limbs. These cuffs may serve as barriers to the diffusion of oxygen, leading to local ischemia and epidermal necrosis. Others suggest that trapped leukocytes in the microcirculation alter capillary permeability by releasing various inflammatory mediators that hasten the flow of fibrinogen across the capillary membrane and promote the formation of fibrin cuffs. Proof of this hypothesis is still lacking, but may eventually come from using radioactive WBC tagging procedures. A synthesis of these two theories may in fact explain the etiology of venous ulceration.
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PMID:Etiology of venous ulceration. 821 32

Although endothelial cell injury and microcirculatory intravascular clotting have been implicated in the pathophysiology of skin-flap failure and various hematologically active drugs have been used to improve flap survival, the basic underlying pathophysiology has not been documented previously. In this study of venous ischemia in pig flaps, we focus on the accumulation and distribution of platelets and fibrinogen in the flap, on the morphologic changes in the flap microcirculation, and on changes in various coagulation factors in the venous effluent from the flap. Bilateral buttock skin flaps and latissimus dorsi myocutaneous flaps were designed and elevated on 12 pigs. All flaps had a primary ischemic insult (clamp application to the vascular pedicle) of 2 hours, followed by 2 hours of reperfusion, and then one side was subjected to a 6-hour period of secondary venous ischemia (clamp application to the dominant flap vein). In six animals, radioactively labeled autologous platelets and human fibrinogen were injected intravenously half an hour before termination of secondary venous ischemia. Flaps were weighed and counted for radioactivity. Flap biopsies and the buffy coat of venous effluent were processed for electron microscopy. In the other six animals, venous effluent was collected before secondary ischemia, upon immediate reperfusion, and at 4 and 8 hours after termination of secondary ischemia. Venous plasma levels of fibrinogen, von Willebrand factor, and antithrombin III were measured. Platelet and fibrinogen accumulation was increased in flaps with venous stasis when compared with control flaps at both time intervals studied; a twofold increase was seen prior to reperfusion, and a threefold increase was seen following 4 hours of reperfusion. Venous effluent could not be collected from buttock skin flaps because of slow reflow and clotting in the collecting system. In comparing the venous effluent of control flaps with that of venous ischemic latissimus dorsi flaps, hematocrit was significantly elevated. Blood samples collected for analysis of fibrinogen, antithrombin III, and von Willebrand factor could not be analyzed because of postcollection clotting. Electron microscopy showed extravasation of red blood cells and activated platelets, fibrin, and red blood cells in distended and partly disrupted capillaries. The venous ischemia reperfusion injury is associated with thrombosis in the microcirculation and alterations in consumption of coagulation factors. This study gives physiologic support for potential beneficial effects of treatment modalities that aim at counteracting the different components of thrombus formation.
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PMID:Venous ischemia in skin flaps: microcirculatory intravascular thrombosis. 831 29

Although endothelial cell injury and microcirculatory intravascular thrombosis have been implicated in the pathophysiology of skin-flap failure, the basic underlying pathophysiology has not been documented previously. This study focuses on the morphologic changes and the alteration in platelet, fibrinogen, antithrombin III, and von Willebrand factor levels in flaps injured by arterial ischemia and reperfusion. A thrombogenic arterial anastomosis model is compared with simple arterial clamping as methods to achieve flap ischemia. Bilateral buttock skin flaps and latissimus dorsi island flaps were elevated in 12 pigs. All flaps had a primary ischemic insult of 2 hours' duration by simple clamp application. During this interval, a thrombus-generating, microvascular anastomosis was prepared, and during a 2-hour period of reperfusion, laser Doppler and transiluminator monitoring of the vascular pedicle allowed documentation of embolic events from the thrombus-generating anastomosis. In group 1 (n = 6), the flaps were then subjected to 7 (buttock skin) and 5 (latissimus dorsi) hours of complete arterial ischemia by clamping. During the secondary ischemic period, the poor microanastomosis was resected and repaired. Radioactively labeled autologous platelets (111In) and human fibrinogen (125I) were injected intravenously half an hour before secondary reperfusion. After 4 hours of reperfusion, flap biopsies and venous effluent were collected and prepared for electron microscopic analysis. The flaps and control tissue were harvested and the radioactivity was counted. In group 2 (n = 6), flaps were subjected to 6 hours of secondary ischemia by using the same technique as in group 1. Central venous and flap venous blood was sampled at baseline as well as upon immediate secondary reperfusion and after 4 and 8 hours of reperfusion. The hematocrit, platelet count, fibrinogen, antithrombin III, and von Willebrand factor levels were determined for these intervals. Platelets and fibrinogen accumulated significantly in buttock skin flaps and in the latissimus dorsi skin and muscle components as compared with similar control tissue (p < 0.05). There was no significant difference in platelet or fibrinogen accumulation after comparing the two ischemic models. Electron microscopic studies showed occluded capillaries with activated platelets in the flaps. Control tissue showed very little capillary occlusion. Platelet count was significantly decreased both in central venous (p < 0.05) and in adventitial infolding flap venous blood (p < 0.025) during immediate reperfusion as compared with baseline. These findings confirm that microcirculatory intravascular thrombosis is implicated in skin-flap ischemia-reperfusion injury. This study provides physiologic support for treatment modalities aimed at counteracting the various components in the coagulation pathways responsible for thrombus formation.
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PMID:Arterial ischemia in skin flaps: microcirculatory intravascular thrombosis. 831 30

Activated neutrophils appear to be directly involved in potentiating central nervous system ischemic injury. After initial endothelial adherence, neutrophils can potentiate ischemia by causing capillary plugging and infiltrating ischemic tissue to release toxic metabolites. We used an endothelial component adherence assay to characterize neutrophil adhesion following reversible central nervous system ischemia. Rabbit spinal cord ischemia was produced by 40 min of reversible arterial occlusion. Neutrophils were isolated using density gradient centrifugation and adherence to laminin or fibronectin was determined using a myeloperoxidase assay. The baseline (N = 26) percentage of adherent neutrophils was 3.8 +/- 0.3/5.6 +/- 0.6 (laminin/fibronectin), sham-operated controls (2 h post) (N = 6) 3.3 +/- 0.5/3.9 +/- 0.4, 30 min post ischemia (N = 6) 2.5 +/- 1.1/4.1 +/-1.9, 2 h (N = 6) 7.6 +/- 1.4/9.9 +/- 2.6 (p < .05 to baseline and sham), 18 h (N = 8) 4.9 +/- 1.5/7.1 +/- 3.1, and 42 h (N = 6) 3.4 +/- 0.4/6.6 +/- 2.1. Concurrent serum fibrinogen values were baseline 142 +/- 12, sham (18 h) 141 +/- 14, 2 h 166 +/- 21, 18 h 512 +/- 43 (p < .01), and 42 h 580 +/- 86 (p < .01). These results suggest that neutrophil adherence is increased after acute central nervous system ischemia. There appears to be a limited period of increased adherence that occurs earlier than other acute phase reactants.
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PMID:Neutrophil adhesion in central nervous system ischemia in rabbits. 838 32

Eight tests of hemostasis were measured in 233 horses with colic. Blood samples were obtained at admission and for 4 consecutive days of hospitalization. Data were analyzed retrospectively by outcome, by broad-category diagnosis group, by small intestinal disorder, and by smaller categories for comparing specific diseases. Nonsurviving horses and horses with the most severe forms of intestinal ischemia had changes interpreted as hypercoagulative, the intensity of which was increased on the first and second mornings (sample times 2 and 3) after admission, when most significant differences for results of specific tests were detected. Nonsurvivors had decreased antithrombin III activity and prolonged prothrombin and activated partial thromboplastin times; those with strangulating obstructions also had decreased protein C and plasminogen activities. During hospitalization and with survival, these changes tended to reverse. In most horses, regardless of diagnosis or outcome, concentration of fibrin degradation products and fibrinogen, and alpha 2-antiplasmin activity increased over time. Whether these changes reflected specific effects of colic or of the acute-phase response was not determined. In comparisons of small intestinal disorders (proximal enteritis, strangulations, and impactions), diagnostically distinguishing features were not found. Likewise, in comparisons of specific diseases (small vs large intestinal impaction, proximal enteritis vs colitis, small vs large intestinal obstruction), diagnostically distinguishing features were not found.
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PMID:Analysis of hemostasis in horses with colic. 840 38


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