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

Net ultrafiltration in peritoneal dialysis results from a complex set of forces within the tissue space surrounding the peritoneal cavity. Hydrostatic pressure due to the large volume of fluid drives water and solute into the surrounding tissue, and therefore a high osmotic pressure must be maintained in the cavity to draw fluid from blood capillaries distributed in the tissue adjacent to the peritoneum. The osmotic pressure in the interstitium decreases from that of the cavity to equilibration with the plasma in the first millimeter of tissue below the peritoneum. Osmotic pressure differences at the blood capillary produce a solute free ultrafiltrate via aquaporin 1 that is approximately 50% of the total filtration. The remainder of the fluid is filtered via interendothelial gaps lined with negatively charged glycocalyx, which alters the traditional Starling forces and is easily damaged by inflammation or ischemia. Ultrafiltration failure occurs when intraperitoneal pressure is too high, the inflamed peritoneum dissipates the osmotic agent rapidly because of hyperpermeable angiogenic vessels, or peritoneal scarring lowers the osmotic pressure near the blood supply and there is no force for fluid transport through the scar to the cavity. To remedy problems in net ultrafiltration, lowering the volume lowers the intraperitoneal pressure and often solves the problem of excessive pressure. Preventative measures to decrease inflammation and peritonitis are important for preservation of the barrier. Experimental measures such as peritoneal stem-cell transplants may someday permit reclamation of damaged barrier systems and allow patients to continue the dialytic technique.
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PMID:Peritoneal ultrafiltration: physiology and failure. 1949 89

In experimentally induced myocardial ischemia, mild hypothermia (33-35 degrees C) has a robust cardioprotective effect. Tissue plasminogen activator (t-PA) is a profibrinolytic enzyme that is released from the vascular endothelial cells in response to ischemia and other injurious stimuli. t-PA has also been found to have proinflammatory properties that could contribute to reperfusion injury. We postulated that hypothermia could attenuate t-PA release in the setting of myocardial ischemia. Sixteen 25-30 kg pigs were anesthetized and a temperature of 37 degrees C was established using an intravascular cooling/warming catheter. The pigs were then randomized to hypothermia (34 degrees C) or control (37 degrees C). A doppler flow wire was placed distal to a percutaneous coronary intervention balloon positioned immediately distal to the first diagonal branch of the left anterior descending artery (LAD). The LAD was then occluded for 10 min in all pigs. Coronary blood flow and t-PA was measured before, during and after ischemia/reperfusion. t-PA was measured in peripheral arterial blood and locally in the venous blood from the coronary sinus. Net t-PA release over the coronary bed was calculated by subtraction of arterial values from coronary sinus values. An estimate of differences in total t-PA release was calculated by multiplying net t-PA release with the relative increase in flow compared to baseline, measured in relative units consisting of ((ng/ml - ng/ml) x (cm/s/cm/s)). There was no observed difference in t-PA levels in peripheral arterial samples. As shown previously, net t-PA release increased during reperfusion. Hypothermia significantly inhibited the increase in t-PA release during reperfusion (peak value 9.44 +/- 4.34 ng/ml vs. 0.79 +/- 0.45 ng/ml, P = 0.02). The effect was even more prominent when an estimation of total t-PA release was performed with mean peak value in the control group 26-fold higher than in the hypothermia group (69.74 +/- 33.86 units vs. 2.62 +/- 1.10 units, P = 0.01). Mild hypothermia markedly reduces ischemia related coronary tissue plasminogen activator release. The reduction of t-PA release may contribute to the cardioprotective effect of hypothermia.
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PMID:Mild hypothermia markedly reduces ischemia related coronary t-PA release. 1949 90

Clinical outcomes in patients with acute coronary syndromes randomized in the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial who underwent percutaneous coronary intervention (PCI) of saphenous vein grafts (SVGs) were examined. The ACUITY trial assessed the safety and efficacy of bivalirudin alone versus bivalirudin plus a glycoprotein (GP) IIb/IIIa inhibitor versus heparin plus a GP IIb/IIIa inhibitor in 13,819 patients with moderate- and high-risk acute coronary syndromes, 7,789 of whom underwent PCI. A total of 329 patients (4.2%) underwent PCI of SVGs in ACUITY. The primary end points at 30 days were composite ischemia or major adverse cardiac events (death, myocardial infarction, or unplanned target vessel revascularization), major bleeding (unrelated to coronary artery bypass grafting), and net adverse clinical events (composite ischemia or major bleeding). The rates of ischemic, bleeding, and net clinical end points were similar with bivalirudin monotherapy, bivalirudin plus a GP IIb/IIIa inhibitor, and heparin plus a GP IIb/IIIa inhibitor. Net adverse clinical outcome rates at 30 days were 22%, 26%, and 22% (p = 0.67), respectively, for the 3 groups. Major adverse cardiac event rates at 1 year were 37%, 37%, and 43% (p = 0.95), respectively. Minor bleeding unrelated to coronary artery bypass grafting at 30 days was significantly lower with bivalirudin alone compared with heparin plus a GP IIb/IIIa inhibitor (26% vs 38%, p = 0.05). In conclusion, bivalirudin is an effective anticoagulant in PCI of SVGs in acute coronary syndromes, with similar rates of major adverse cardiac events and net adverse cardiac events and lower minor bleeding complications in comparison with heparin plus a GP IIb/IIIa inhibitor or bivalirudin plus a GP IIb/IIIa inhibitor.
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PMID:Comparison of Bivalirudin versus Bivalirudin plus glycoprotein IIb/IIIa inhibitor versus heparin plus glycoprotein IIb/IIIa inhibitor in patients with acute coronary syndromes having percutaneous intervention for narrowed saphenous vein aorto-coronary grafts (the ACUITY trial investigators). 2085 54

Isolated liver perfusion systems have been used to characterize intrinsic metabolic changes in liver as a result of various perturbations, including systemic injury, hepatotoxin exposure, and warm ischemia. Most of these studies were done using hyperoxic conditions (95% O(2)) but without the use of oxygen carriers in the perfusate. Prior literature data do not clearly establish the impact of oxygenation, and in particular that of adding oxygen carriers to the perfusate, on the metabolic functions of the liver. Therefore, herein the effects of oxygen delivery in the perfusion system on liver metabolism were investigated by comparing three modes of oxygenation. Rat livers were perfused via the portal and hepatic veins at a constant flow rate of 3 mL/min/g liver in a recirculating perfusion system. In the first group, the perfusate was equilibrated in a membrane oxygenator with room air (21% O(2)) before entering the liver. In the second group, the perfusate was equilibrated with a 95% O(2)/5% CO(2) gas mixture. In the third group, the perfusate was supplemented with washed bovine red blood cells (RBCs) at 10% hematocrit and also equilibrated with the 95% O(2)/5% CO(2) gas mixture. Oxygen and CO(2) gradients across the liver were measured periodically with a blood gas analyzer. The rate of change in the concentration of major metabolites in the perfusate was measured over time. Net extracellular fluxes were calculated from these measurements and applied to a stoichiometric-based optimization problem to determine the intracellular fluxes and active pathways in the perfused livers. Livers perfused with RBCs consumed oxygen at twice the rate observed using hyperoxic (95% O(2)) perfusate without RBCs, and also produced more urea and ketone bodies. At the flow rate used, the oxygen supply in perfusate without RBCs was just sufficient to meet the average oxygen demand of the liver but would be insufficient if it increased above baseline, as is often the case in response to environmental perturbations. Metabolic pathway analysis suggests that significant anaerobic glycolysis occurred in the absence of RBCs even using hyperoxic perfusate. Conversely, when RBCs were used, glucose production from lactate and glutamate, as well as pathways related to energy metabolism were upregulated. RBCs also reversed an increase in PPP fluxes induced by the use of hyperoxic perfusate alone. In conclusion, the use of oxygen carriers is required to investigate the effect of various perturbations on liver metabolism.
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PMID:Metabolic response of perfused livers to various oxygenation conditions. 2175 98

The aim of this study was to investigate the association between major adverse cardiovascular events (MACEs) and inducible ischemia on regadenoson cardiac magnetic resonance (CMR) myocardial perfusion imaging (MPI) performed at 3.0 T. Regadenoson stress CMR MPI is increasingly used to assess patients with suspected ischemia; however, its value in patient prognostication and risk reclassification is only emerging. A total of 346 patients with suspected ischemia who were referred for regadenoson CMR were studied. The prognostic association of presence of inducible ischemia by CMR with MACEs was determined. In addition, we assessed the extent of net reclassification improvement by CMR beyond a clinical risk model. There were 52 MACEs during a median follow-up period of 1.9 years. Patients with inducible ischemia were fourfold more likely to experience MACEs (hazard ratio, 4.14, 95% confidence interval 2.37 to 7.24, p <0.0001). In the best overall model, presence of inducible ischemia conferred a 2.6-fold increased hazard for MACEs adjusted to known clinical risk markers (adjusted hazard ratio 2.59, 95% confidence interval 1.30 to 5.18, p = 0.0069). Patients with no inducible ischemia experienced a low rate of cardiac death and myocardial infarction (0.6% per patient-year), whereas those with inducible ischemia had an annual event rate of 3.2%. Net reclassification improvement across risk categories (low <5%, intermediate 5% to 10%, and high >10%) by CMR was 0.29 (95% confidence interval 0.15 to 0.44), and continuous net reclassification improvement was 0.58. In conclusion, in patients with clinical suspicion of myocardial ischemia, regadenoson stress CMR MPI provides robust risk stratification. CMR MPI negative for ischemia was associated with a very low annual rate of hard cardiac events. In addition, CMR MPI provides effective risk reclassification in a substantial proportion of patients.
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PMID:Risk stratification by regadenoson stress magnetic resonance imaging in patients with known or suspected coronary artery disease. 2517 44


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