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

Double tourniquets linked to separate Freon cannisters and two mercury manometers have been effective in maintaining ischemia in over 1,000 consecutive hand surgery operations. The mercury manometers permit constant accurate monitoring of the tourniquet pressure. The cuffs are used alternately. Each is inflated for up to 1 hour in order to limit the duration of nerve compression deep to the cuff. If there is malfunction of either cuff, the other cuff may be inflated at once. This system has permitted sustained ischemia in the upper extremity for up to 3 1/2 hours at a constant tourniquet pressure with no permanent clinically apparent sequellae. There has been no permanent nerve injury, although patients with more than 2 hours of tourniquet time often note hypoesthesia or paresthesia for 1 or 2 days. The alternating double tourniquet linked to a mercury manometer permits up to 3 1/2 hours of continuous ischemia of the upper limb with little risk of nerve damage.
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PMID:Double tourniquet with linked mercury manometers for hand surgery. 664 76

Thromboxane A2 is thought to be an important mediator of cardiopulmonary dysfunction, hence stimuli that effect synthesis of this prostanoid are of major interest. In this study, the thesis that ischemia of the limb is a significant stimulus to thromboxane A2 synthesis and the generation of a circulating negative inotrope is tested. Twelve healthy volunteers, taking no medications and ranging in age from 21 to 29 years, underwent inflation of an arm cuff to either 70 or 220 millimeters of mercury for ten minutes. Immediately after deflation of the cuff from 220 millimeters of mercury, the stable degradation product of thromboxane A2, thromboxane B2, rose from a base line plasma level of 34 +/- 6 picograms per milliliter (mean +/- SEM) to 70 +/- 18 picograms per milliliter. In contrast, deflation from a cuff pressure of 70 millimeters of mercury resulted in a lower thromboxane B2 level of 26 +/- 9 picograms per milliliter (p less than 0.05). Plasma obtained before and after inflation of the cuff to 220 millimeters of mercury was used to bathe a rat papillary muscle. Developed tension fell from a base line of 2.80 +/- 0.19 to 2.44 +/- 0.17 grams (p less than 0.01). There was no significant change in developed tension induced by plasma harvested after the cuff was inflated to 70 millimeters of mercury. The base line plasma level of 6-keto-prostaglandin F1 alpha, the hydrolysis product of prostacyclin, was 46 picograms per milliliter; the plasma serotonin, 51 nanograms per milliliter; the platelet serotonin, 1.02 micrograms per 10(9) platelets; platelet count, 220,000 per cubic millimeter, and white blood count, 6,094 per cubic millimeter. These values did not change significantly with cuff inflation to either 220 or 70 millimeters of mercury. The results show that ischemia of the limb leads to thromboxane A2 production. Possible adverse cardiac effects related to this event are suggested by the bioassay demonstrating that circulating plasma with high levels of thromboxane B2 is associated with the depression of tension of an isolated rat papillary muscle.
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PMID:Ischemia of the limb stimulates thromboxane production and myocardial depression. 664 69

Ischemic change of cerebral energy metabolism and catecholamine have already been discussed largely using biochemical quantitative assay. However, regional change and their correlation are not well understood. In the present study, the ischemic regional change of cerebral energy metabolism and catecholamine were investigated in gerbils and histochemical method. Adult either sex mongolian gerbils, weighing 50-100 g, were anesthetized with ether and the left carotid artery was ligated. After observation of clinical symptoms, the brain was frozen in situ by pouring liquid N2 after 30 min and 60 min of ischemic insult. The frozen brain was sectioned with precooled saw in the coronal plane. The brain section were placed in liquid N2 bath and illuminated with 366 nm light (UV) from a 200 watt mercury lamp and Corning filter 5840. NADH fluorescence was recorded photographically through Corning filter 3387 and 5562. Also UV reflectance was recorded through Corning filter 5840 to observe quenching effect of hemoglobin. Regional change of catecholamine was observed in the same frozen brain processed with Falck-Hillarp method. According to neurological abnormalities following left carotid ligation, animals were divided into three groups; symptomatic, borderline and asymptomatic. The intensity and distribution of tissue NADH fluorescence were closely correlated to the clinical symptoms. In the symptomatic group, both in 30 min and 60 min of ischemia, homogeneously and markedly increased fluorescence was observed in the ipsilateral temporal cortex, caudate nucleus, hypothalamus and dorsolateral thalamus. Columnar mild increase of NADH fluorescence was seen in the ipsilateral parietal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Regional change of brain energy metabolism and catecholamine in the early stage of experimental cerebral ischemia--histochemical study]. 673 86

Experimentally, we produced obstruction of the intestine in dogs, and the intraluminal pressure of the small intestine was measured without inducing anesthesia and with the abdominal wall closed. The maximum active intraluminal pressure reached 44.1 +/- 3.3 milligrams of mercury three days after the obstruction was produced. The pressure rose further to 95 millimeters of mercury, or higher, after an intravenous injection of physostigmine or during vomiting. When the intraluminal pressure is artificially increased and the vascular structure is observed by the resin-casting method, impairment of the villous circulation of the mucosa is already seen when the pressure reaches 20 millimeters of mercury. When the pressure was further increased, the circulation impairment spread toward the outer layer of the intestine. Mesenteric blood flow, peripheral vascular resistance and submucosal blood flow did not show significantly lower values than did the control group, unless the intraluminal pressure was 100 millimeters of mercury, or higher, but the oxygen consumption of the intestinal tissues was significantly lower than that for the control group when the intraluminal pressure was 40 millimeters of mercury, or higher. The resin-casting method showed that, at this pressure, a finding believed to indicate an arteriovenous shunt was already present at the mucosal villous base. The aforementioned results indicate that selective mucosal ischemia may occur when the intraluminal pressure increases to a range that is clinically possible when obstruction of the intestine occurs.
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PMID:Experimental studies on the hemodynamics of the small intestine following increased intraluminal pressure. 682 51

To evaluate the role of distal perfusion pressure in predicting the healing of 31 digit and forefoot amputations preoperative digital, transmetatarsal and ankle systolic pressures were retrospectively compared with the eventual results of amputation. A photoplethysmography transducer placed distal to an occluding cuff was used to measure digital and transmetatarsal level systolic blood pressure. Ankle pressures were measured with Doppler ultrasound. Twenty-six amputations healed initially, whereas, four required reamputation proximal to the ankle. There was no difference in mean ankle Doppler pressure between the healed and failed groups. Mean photoplethysmography derived transmetatarsal pressure was significantly higher in the healed group, 116 +/- 47 millimeters of mercury as compared with the failed group, 44 +/- 88 millimeters of mercury. The difference in mean photoplethysmography digital pressure in the healed and failed groups--75 +/- 36 and 4 +/- 9 millimeters of mercury, respectively--was highly significant, p less than 0.001. Failure of digit or forefoot amputation occurred in all limbs with photoplethysmography derived pressures of less than 20 millimeters of mercury. A transmetatarsal or digital photoplethysmography pressure of greater than 20 millimeters of mercury was associated with amputation healing in all instances. These data suggest that photoplethysmography distal perfusion pressures may be valid predictors of the healing potential of minor foot amputations for end stage ischemia.
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PMID:Predictive value of distal perfusion pressure in the healing of amputation of the digits and the forefoot. 707 30

Mechanical function remains depressed for hours and days after even brief periods of ischemia. To determine whether the depressed function of the reperfused myocardium could be improved y inotropic stimulation, we studied segmental function during ischemia and after reperfusion using mercury-in-Silastic length gauges in 15 dogs. During coronary artery occlusion, segmental function could not be improved by inotropic stimulation with dopamine. Release of occlusion after 30 minutes of ischemia resulted in only slight improvement in segmental function (systolic shortening at 20% of control). After reperfusion, segmental function could be markedly enhanced by inotropic stimulation. The response to inotropic stimulation was similar after reperfusion after 3 hours of ischemia if the myocardium remained viable (nine dogs). When the myocardium was necrotic (five dogs), there was no improvement after reperfusion, either spontaneously or in response to inotropic stimulation. If applicable to humans, these results suggest that intractable pump failure caused by extensive but reversible ischemia could be effectively treated by reperfusion and inotropic stimulation.
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PMID:Divergent effects of inotropic stimulation on the ischemic and severely depressed reperfused myocardium. 709 46

1. Step torque perturbations were applied to flex or extend the wrists of normal human subjects who were instructed to restore the joint to its initial position as quickly as possible. The resulting electromyographic (EMG) activity was recorded from the flexor carpi radialis, flexor carpi ulnaris, and extensor carpi radialis. Experiments were performed under control and three altered conditions of the limb: 1) ischemia, 2) vibration, and 3) local ulnar nerve anesthesia. The effects of the procedures on the EMG responses in four poststimulus intervals--the myotatic (30-60 ms), late myotatic (60-120 ms), postmyotatic (120-200 ms), and stabilizing (200-400 ms)--were studied. 2. Ischemia was induced in the forearm by means of a sphygmomanometer cuff inflated to 150 mm of mercury around the upper arm. After about 20 min of ischemia the stretch-evoked EMG activity over the 30-60-ms and 60-120-ms intervals were abolished, while the longer latency responses persisted. 3. Vibration at frequencies between 50 and 120 Hz was applied to the tendon of the stretched muscle. Vibration consistently reduced the EMG activity only in the 30-60-ms interval. 4. The ulnar nerve was blocked near the elbow joint by local anesthetic. Varying degrees of block were obtained, from a mild sensory impairment to a complete block. At intermediate degrees of block, EMG activity in the 30-60-ms and 60-120-ms intervals were attenuated with little alteration in later responses. 5. The data are used to differentiate functionally the myoelectric responses evoked in four poststimulus time segments in the stretched muscle by step torque perturbations.
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PMID:Afferent contributions to stretch-evoked myoelectric responses. 711 56

Regional function parameters under myocardial ischemia are frequently clearly changed when the parameters as the stroke volume, cardiac output, ejection fraction and the like are still unchanged by a compensation mechanism. Length changes can be measured regionally and phasically by means of a mercury wire strain gauge. The active shortening during the ejection time in relation to the total length change in this region is a possibility for the registration of the relative systolic shortening (delta LS%). Changes will be quantified still clearer and earlier if in the x-y display a vector representation of the regional displacements with the pressure in the left ventricle takes place. The plane of this vector decreased already a few seconds after the coronary occlusion. This is therefore a special early change in ischemia. The important for the estimation of therapeutic measures and other indirect measuring methods is accentuated.
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PMID:[Evaluation of regional heart function by means of local changes in pressure and direction in the vector cardiogram]. 721 Jul 62

While sudden death after acute myocardial infarction or ischemia most commonly occurs in the first few minutes, usually from tachyarrhythmias, little is known of associated hemodynamics. We monitored hemodynamics for 15 minutes following coronary embolization with mercury in 31 awake dogs. In 17 nonsurvivors, mean arterial pressure (MAP) fell 7 mm Hg at 15 seconds, 15 mm Hg by 45 seconds, 27 mm Hg at 120 seconds, and continued falling until ventricular fibrillation (VF) occurred. In contrast, in 14 survivors, MAP was unchanged at 15 seconds, fell 8 mm Hg at 45 seconds, 15 mm Hg at 120 seconds, and than returned toward control. The decline in MAP was significantly greater and earlier in nonsurvivors. Heart rate increased at 15 seconds in nonsurvivors (21 bpm) but not until 75 seconds in survivors (33 bpm). Cardiac output fell significantly only in nonsurvivors. Ventricular ectopics (greater than 5 beats/15 sec) first appeared after hemodynamic changes in both groups; at 68 seconds in survivors and at 45 seconds in non survivors. While such ectopy persisted at the same frequency thereafter in both groups, VF occurred only in the more hypotensive dogs at 177 seconds. In a second series of 26 dogs, hypotension was randomly treated by intra-aortic balloon. All nine nonhypotensive dogs survived, whereas five of six untreated hypotensive dogs died compared to 2 of 11 treated ones (p less than 0.02). We conclude that significant hemodynamic changes precede ectopy, and VF and sudden coronary death occurs usually after persistence of hypotension.
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PMID:Significance of hypotension preceding fatal ventricular tachyarrhythmias in post-coronary obstruction sudden death. 721 70

A large number of experimental studies suggests that oxygen free radicals play a major role in the pathogenesis of the myocardial lesions observed during the sequence ischemia-reperfusion. The purpose of this study was to determine whether oxygen free radicals can induce thrombosis. In so doing we have developed a new experimental thrombosis model. Reproducible focal thrombosis has been achieved by irradiating mesenteric arterioles of rat for variable time with green filtered light issuing from a mercury lamp after systemic injection of different rose bengal doses. The number of emboli that remove in the blood (N), the duration of total occlusion (T) and the number of emboli per minute were then measured. As control, no rose bengal administration was done and the vessels were exposed to the filtered light. In comparison with this control, results clearly showed that free radicals always induced thrombosis and the induced thrombus was mainly composed of platelets. In this new thrombosis model induced by free radicals antithrombotic drugs (aspirin, 200 mg/Kg, heparin, 2 mg/Kg) and antioxidants (vitamin C, 10 and 20 mg/Kg, allopurinol, 200 and 300 mg/Kg, vitamin E, 500 and 1000 mg/Kg) have been tested. Results have shown that only heparin and vitamin E had an antithrombotic effect on thrombus formation induced by free radicals. This model should be useful in studying the effects of different drugs and could lead to new treatment modalities for ischemic accident and other cardiovascular diseases.
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PMID:Experimental thrombosis model induced by free radicals. Application to aspirin and other different substances. 749 98


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