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

Techniques for using the rat hind limb as a model of pure arterial ischemia at rest have not been well defined. Because the rat has no profunda femoral artery, numerous collateral pathways exist to the hind limb, and femoral artery ligation is not an effective method of inducing arterial ischemia. After several anatomic studies, a two stage operation to produce arterial ischemia in the left hind limb was devised. The first stage involved surgical interruption of collateral and re-entrant vessels, and the second stage involved femoral artery ligation. Using Xenon 133 clearance as an estimate of blood flow, reduction in flow to 14, 24, and 37% of the simultaneously measured value in the right hind limb was obtained at 2 hours, 2 days, and 5 days post ligation. Oxygen extraction in the left hind limb doubled both at 2 hours and at 2 days post ligation. Histological evaluation of the anterior compartment musculature after 5 days demonstrated loss of nuclei, degenerating contractile elements, edema, and inflammatory infiltrate. Evaluation of rats that had undergone isolated femoral artery ligation showed a 66% reduction in flow 2 hours after ligation, but no reduction in flow at 5 days, no increase in oxygen extraction, and only nuclear changes on histological exam at five days.
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PMID:An evaluation of resting arterial ischemia models in the rat hind limb. 403 Aug 84

Cutaneous blood flow (Xenon clearance) and transcutaneous pO2 were simultaneously measured on the foot of normal subjects and patients suffering from severe arterial insufficiency of the lower limbs. When the subject is sitting, cutaneous blood flow decreases, as well in normal subjects than in most patients with arterial insufficiency. However, tc pO2 increases in sitting position, probably because local vasoregulation is abolished by local heating. Increase in tc pO2 in sitting position is higher in patients in whom tc pO2 was very low in lying position. In normal subjects, there is a positive correlation between cutaneous blood flow and tc pO2. This correlation do not exist in patients suffering from severe ischemia; it is likely that Xenon clearance actually measures total cutaneous blood flow, while tc pO2 constitutes an index of nutritional circulation. It is also possible that Xenon clearance is modified by changes in partition coefficient in ischemia areas.
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PMID:[The venous-arteriolar reflex]. 403 84

Temporal muscle blood flow (TMBF) was measured by the local 133-Xenon washout technique in 61 patients suffering from common migraine. Nineteen were re-examined in the course of spontaneous attacks. Muscle tension was quantified by surface EMG. During the attacks, median TMBF increased insignificantly, 33% on the ipsilateral and 24% on the contralateral side. During 15 unilateral attacks, the ipsilateral-contralateral ratio of TMBF was 1.02. Isometric and dynamic work tests showed intact metabolic regulation of TMBF. These results speak against a general vasomotor disturbance of the extracranial tissues during attacks of common migraine. There was also no indication that ischemia of the temporal muscle might explain the pain.
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PMID:Temporal muscle blood flow in common migraine. 409 99

Significant delay in the washout of intraperitoneal xenon (133Xe) in rats and dogs with decreased splanchnic blood flow (bowel strangulation, superior mesenteric artery and vein occlusion) has been previously demonstrated as the basis for radionuclide imaging to detect early (prenecrotic) intestinal ischemia. In this study, the effect of ascites, adhesions, and misdirected injections on the validity of this technique is evaluated. Xenon-133 (0.6 mCi) in 3 ml saline was injected into the peritoneal cavity of anesthetized rats and the washout of gamma activity monitored externally for 90 min. Gamma camera images were obtained at 30-min intervals. After 60 min, only 12 +/- 2% of injected activity remained in the controls. Sham operation (13 +/- 1%) and simple obstruction (12 +/- 2%) had been previously shown not to significantly slow washout, but segmental strangulation had done so dramatically (32 +/- 2%, P less than 0.0001). In these experiments, ascitic fluid (Ringer's lactate) in volumes of 10 ml (13 +/- 1%), 20 ml (13 +/- 1%), and 40 ml (13 +/- 1%), did not significantly slow washout in nonischemic rats. Sixty and eighty milliliters produced very tense ascites and slight but significant delay in washout (14 +/- 1%, 17 +/- 1%, respectively, P less than 0.05). Moderate (11 +/- 1%) and severe (11 +/- 1%) adhesions produced by serosal scarification did not delay washout nor affect imaging. Injections of isotope intentionally misdirected into the abdominal wall (32 +/- 2%), bowel wall (18 +/- 1%), and bowel lumen (19 +/- 2%), each significantly (P less than 0.001) slowed washout. However, such misdirected injections were easily recognizable as such on the 1-min gamma camera images and could thereby be excluded as artifactual. Therefore, no false positive readings were obtained. It is concluded that the intraperitoneal xenon technique is not invalidated by mild to moderate ascites nor by moderate to severe adhesions. Misdirected injections produce invalid studies that are recognizable as such and thus are not misinterpreted. This approach should therefore be applicable to most patients with suspected intestinal ischemia.
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PMID:Intraperitoneal xenon for the detection of early intestinal ischemia: effect of ascites, adhesions, and misdirected injections. 622 20

In five healthy males sustained isometric torques during elbow flexion, knee extension, and plantar flexion correlated positively with intramuscular tissue pressure (MTP) in the range 0-80% of the maximal voluntary contraction (MVC). During passive compression of the muscle at rest 133-Xenon muscle clearance stopped when MTP reached diastolic arterial pressure (DAP) indicating that the muscle vascular bed was occluded. However, during sustained contraction this relation between DAP, flow and MTP was not seen. In two cases 133-Xenon clearance from M. soleus did not stop in spite of an 80% maximal contraction and MTP stayed below DAP. In other cases MTP would reach as high as 240 mm Hg before clearance was zero. In the deeper parts of the muscles MTP during contraction was increased in relation to the more superficial parts. The means values for the % MVC that would stop MBF varied between 50 and 64% MVC for the investigated muscles. Mean rectified EMG (MEMG) showed a high correlation to MTP during sustained exhaustive contractions: When MEMG was kept constant MTP also remained constant while the exerted force decreased; when force was kept constant both MEMG and MTP increased in parallel. This demonstrated that muscle tissue compliance is decreasing during fatigue. Muscle ischemia occurring during sustained isometric contractions is partly due to the developed MTP, where especially the MTP around the veins in the deeper parts of the muscle can be considered of importance. However, ischemia is also affected by muscle fiber texture and anatomical distorsion of tissues.
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PMID:Skeletal muscle tension, flow, pressure, and EMG during sustained isometric contractions in humans. 668 38

A survey of the Xenon-133 techniques for measurement of regional cerebral blood flow, rCBF, in man is presented. The intra-arterial Xe-133 injection method is very sensitive for detecting even small hyperemic areas, but cannot "see" smaller ischemic areas. The Xe-133 inhalation (or i.v. inj.) technique is insensitive both to hyperemia and ischemia yielding essentially only a mean flow value. A new rapidly moving single photon tomograph following D. Kuhl's principle is presented applicable to Xe-133. Preliminary clinical data show that this technique is able to detect ischemic areas both with Xe-133 intra-arterial injection and with Xe-133 inhalation. The practical and economic advantages of Xe-133 or Xe-127 tomography over positron tomography for rCBF are discussed.
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PMID:Regional cerebral blod flow studied by xenon-133. Intra-arterial injection studies and inhalation studies using emission tomography. 696 6

Decreasing progressive dermal ischemia after burning could theoretically limit the amount of skin necrosis to the zone of coagulation. Methylprednisolone, aspirin, indomethacin, imidazole, dipyridamole, and methimazole have been shown to prevent dermal ischemia, suggesting that prostaglandins and/or thromboxanes may play a role in its pathogenesis. Specific antiprostaglandin antibodies (anti-PgE2, PgF2 alpha, PgI2, and TxA2) were reacted with tissue biopsies of burned guinea pig skin at various time intervals postburn. An immunoperoxidase technique with goat anti-rabbit immunoglobulin and horseradish peroxidase demonstrated the presence of the specific arachidonic acid metabolites. The burned tissue showed high levels of PgE2 and TxA2. The effects of three thromboxane inhibitors, imidazole, methimazole, and dipyridamole, on dermal ischemia were studied. Xenon133 washout studies were performed in burned and unburned areas. Tissue half-life of Xenon was prolonged in burned, untreated areas but this rapidly decreased in antithromboxane-treated burns. Repeated antiprostaglandin and antithromboxane antibody-immunoperoxidase studies on tissue from the thromboxane inhibitor-treated animals showed that PgE2, PgF2 alpha, and PgI2 were at the same levels as in untreated animals, but thromboxane (TxA2) was essentially absent, suggesting that thromboxane may be responsible for the progressive dermal ischemia after burning and that decreasing its production can increase dermal perfusion.
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PMID:Increasing dermal perfusion after burning by decreasing thromboxane production. 699 4

The mechanisms regulating vascular tone in the myocardium were studied in open-chest anesthetized dogs by occlusions of the left anterior descending coronary artery (LAD) for 3 to 600 s. Cumulative excess blood flow (flow in excess of control flow), and repayment of flow debt (cumulative excess blood flow divided by blood flow deficity) were calculated using local injections of Xenon-133 for blood flow measurements. Release of vascular occlusion following 3 s of ischemia was not associated with any measurable hyperemia. Cumulative excess blood flow increased with increasing duration of ischemia from 5 to 600 s, but the increment in excess flow per unit extention of the occlusion time showed a considerable decline. Blood flow in excess exceeded blood flow diet incurred during the occlusion of 10 s duration of 161%; with prolongation of ischemia to 600 s repayment of flow debt declined markedly to about 10%. Oxygen lack in the tissue elicited by perfusion of LAD-for 10 s with constant perfusion rate-with deoxygenated blood produced a fall in peripheral coronary resistance of about 40% which closely corresponds to the fall in resistance observed after a period of LAD occlusion of similar duration. The results lead to the conclusion that 'vasodilator' metabolites formed in the tissue during periods of arterial occlusion are of prime importance for the fall in the tone on the vascular smooth muscle cell occurring in the post-occlusion period. The findings argue against a myogenic component in this response.
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PMID:Regional blood flow during reactive hyperemia in canine myocardium as determined by local washout of xenon-133. 701 Sep 20

In a consecutive group of 56 stroke patients the regional cerebral blood flow was measured within 84 hours after stroke. A 254 multidetector scintillation camera and the intracarotid Xenon-133 injection method was used to study rCBF. Typical rCBF-patterns are described and compared to the findings on CT-scan. According to these studies focal brain areas exposed to ischemia appeared in 3 different forms; 1) As an ischemic area surrounded by a hyperemic borderzone, seen in areas with arterial occlusion and infarction on CT-scan. 2) As a pronounced hyperemic area without associated ischemia located in areas of infarction (seen on CT-scan) without arterial occlusion. This form is presumably due to arterial recanalization and reperfusion in an established infarct. 3) As a pronounced focal hyperemia also without ischemia, located in normal CT-areas without arterial occlusion. This form is probably due to recanalization of an occluded artery shortly after occlusion without development of infarction.
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PMID:Patterns of regional cerebral blood flow in acute stroke. 734 67

To evaluate the course of cerebral tissue perfusion in patients with acute focal cerebral ischemia of the supratentorial compartment regional cerebral blood flow (rCBF) was measured on day 0, 7, 14, 21, and 28 in 132 patients using the 133 Xenon stationary inhalation technique. Ischemic events of the brainstem and hemorrhagic complications were excluded. The clinical status was evaluated using a modified Mathew score. In 34 patients no hemodilution, anti-edema therapy, or Ca(++)-antagonists were used but otherwise best medical therapy was applied. These patients represented the so called "natural course" of cerebral ischemia. In 30/34 patients on day 0 (within 16 hours after onset of symptoms) focal flow abnormalities were found in the involved side. In 9 of these 30 patients and in 1 of the remaining ischemia was observed in the contralateral side. rCBF above normal (relative luxury perfusion) despite pathologic neurologic findings was observed in 8/34 patients on day 3-7. Eight patients presented on day 3-7 with normal flow which later became ischemic again without evidence of another symptomatic episode. Correlation between severity of clinical findings and actual rCBF was low from day 3 to 7 but close on day 0. From day 14-21 hemispheric CBF correlated well with the total neurologic score but focal clinical findings had a lower correlation with focal flow as compared to day 0 and day 28. Contralateral ischemia was never found after day 14. In 5 other cases with "natural course" described above, a transitory decrease of rCBF below the initial ischemia level was found between day 3 and 14.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Blood flow and clinical course in patients with ischemic stroke without cerebrospecific therapy. 767 77


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