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

The clinical success of limb replantation and tissue transfer is partly dependent on the duration of ischemia experienced by the amputated part. This study focused primarily on the damage that occurs during this ischemic period. An experimental system was implemented that allowed the observation of contractile function in totally isolated skeletal muscle after ischemia. Contractile function was selected as an indicator of ischemic damage because normal function is the ultimate goal of replantation. All experiments were performed on the rat extensor digitorum longus. The muscles were subjected to ischemic periods of 1.5, 3.0, and 5.0 hours and were stored in either a hypothermic (4 degrees C) or a room-temperature (23 degrees C) environment during the ischemic interval. After the ischemic period, all muscles were transferred to a tissue bath and were subjected to contractility testing, followed by fatigue testing. In both groups, muscle function decreased as the ischemic interval was increased. A significant difference in function between the normal control and the muscles of both ischemic groups implied that ischemic injury had occurred in the hypothermic and room-temperature muscles, even with the relatively short 1.5-hour ischemic interval. After each ischemic interval however, the hypothermic muscles produced significantly greater contractile force than the room-temperature muscles in both the contractility and the fatigue tests. After 1.5 hours of ischemia, the contractile force in the hypothermic group was about three times as great as that observed in the room-temperature group. These results indicated that muscle function after a period of totally isolated ischemia is protected by hypothermic preservation. They also support the advisability of storage of amputated parts and free muscle flaps in hypothermic environments before replantation even after relatively brief intervals of ischemia.
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PMID:Protective effect of hypothermia on contractile force in skeletal muscle. 867 51

The most attractive feature of nuclear magnetic resonance spectroscopy (MRS) is the noninvasive and nondestructive measurement of chemical compounds in intact tissues. MRS already has many applications in comparative physiology, usually based on observation of 31P, since levels of phosphorus compounds indicate tissue energy status and are changed during exercise, fatigue, recovery, hypometabolism, anesthesia, hypoxia, hypercapnia, and osmotic and acid stress. Nuclei other than 31P may also be monitored, such as 1H, 13C, 15N, 19F, or 23Na, and applied in biological research. Particularly, 13C-MRS is interesting because it allows the analysis of metabolic pathways in living systems. Applications of MRS in comparative physiology and biochemistry are comprehensively discussed in this review. The main focus is on anaerobic metabolism during hypoxia, ischemia, and exercise. Species as widely different as slime molds, nematodes, frogs, turtles, and ducks have been studied by 31P-MRS. It is not surprising that striking species differences do occur, but many similarities are also observed. Unique is the occurrence of six different phosphagens with different values of Gibbs free energy in polychete worms The presence of a particular phosphagen may be related to the average oxygen tension within the tissues. Phosphagens and their kinases are also discussed in relation to hypercapnia and acid stress. Other topics discussed in this paper are enzyme kinetics, anesthetics, development and growth, parasitism, and the detection of previously unknown compounds.
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PMID:Nuclear magnetic resonance spectroscopy of living systems: applications in comparative physiology. 875 89

The duration of tourniquet-induced ischemia during orthopedic and reconstructive surgery is limited by the risk of ischemia and reperfusion injury to skeletal muscle. This study evaluated the potential of ischemic preconditioning (short periods of ischemia with intermittent reperfusion) to improve skeletal muscle function after ischemia and reperfusion in a rodent model. Preconditioning was found to improve force, contractility, and performance and to decrease fatigue of skeletal muscle. In contrast, energy-rich phosphates, measured concurrently, were not affected by preconditioning, suggesting mechanisms other than energy preservation to be involved. In summary, preconditioning may enable prolongation of orthopedic and reconstructive procedures.
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PMID:Ischemic preconditioning--a new concept in orthopedic and reconstructive surgery. 876 33

The diagnosis of arteriosclerosis obliterans of the lower extremities can be made by the history alone or by the physical examination alone in the most patients. It is very important to evaluate the hemodynamic study in determination of indication for operation and operative procedures. The two major symptoms, each of which diagnostic, are intermittent claudication and ischemic rest pain. Intermittent claudication is pain or fatigue that occurs in a muscle or muscle group on repititive use. The anatomical level of claudication is significant. When aorto-iliac artery is obstructed, pain may occur first in the hip or thighs. Pain occurs in the calf in the occlusion of the femoral artery and foot pain indicates the occlusion of distal popliteal artery. Ischemic rest pain indicates an advanced stage of the disease. Fontaine classification is usually used as the stage of ischemia on the extremity. There are many laboratory evaluations of circulatory insufficiency in the diagnosis of arteriosclerotic obliterans. Measurement of segmental blood pressure is most valuable and useful among various measurements. We can get critical informations of circulatory insufficiency in the leg using segmental blood pressure. In order to differentiate from arteriosclerotic obliterans there are thromboanyitis obliterans aortitis syndrome, popliteal arterial entrapment syndrome, spinal canal stenosis, and diabetic arterial occlusive disease.
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PMID:[Clinical diagnosis of arteriosclerosis obliterans]. 880 11

Verapamil (VRP) improves ischemic tolerance of different organs including brain, kidney, liver and heart. We report here on the effects of preischemic VRP treatment on skeletal muscle function following 3 h of tourniquet ischemia and 2 h of reperfusion using a rodent model. Postischemic and contralateral limbs were evaluated. Fast (musculi peronei)- and slow-twitch muscles (musculus soleus) of both limbs were excised and electrically stimulated in vitro. VRP pretreatment was found to significantly decrease tetanic peak tension of both contralateral nonischemic m. soleus and mm. peronei. Furthermore, VRP improved fatigability of slow-twitch muscles of both ischemic and contralateral limbs [increase of fatigue index from 0.04 +/- 0.009 (0 mg/kg) to 0.10 +/- 0.019 (4 mg/kg)], but not of fast-twitch muscles. These data indicate that the effects of VRP on postischemic skeletal muscle function depend on fiber composition.
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PMID:Effects of verapamil on skeletal muscle function following ischemia and reperfusion. 883 64

A 62-year-old woman with exertional angina underwent an exercise thallium-201 stress test. She exercised for 4 minutes on the treadmill using a modified Bruce protocol, reaching 94% of her predicted maximal heart rate, and stopped because of chest pain and fatigue. No ST-segment depression was detected at peak exercise or in the recovery period. In contrast, the thallium-201 myocardial single-photon emission computed tomography images in the short-axis, vertical long-axis, and horizontal long-axis views revealed severe myocardial ischemia involving the anterior, septal, posteroinferior, and posterolateral planes of the heart. Coronary arteriography showed severe stenosis of the left anterior descending and right coronary arteries. The information from the exercise electrocardiogram (ECG), thallium-201 myocardial scintigraphy, and a coronary angiogram suggested that the false negative ECG response was due to ischemic ST-segment counterpoise (i.e., cancellation of ischemic ST-segment vectors, generated by equally extensive and severe ischemia involving myocardial planes opposite each other.
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PMID:The paradox of negative exercise stress ECG/positive thallium scintigram. Ischemic ST-segment counterpoise as the underlying mechanism. 885 35

Hypothermia is a frequent event in trauma patients and appears to be related to posttraumatic organ dysfunction, although in elective surgery hypothermia is known to prevent ischemia reperfusion injury. Retrospectively, we analyzed data of 641 trauma patients treated in our institution between 1988 and 1993. At hospital admission the core temperature (cT) was > 34 degrees C in the majority (64%) of all patients, < 34 degrees C in 23.6% and < 32 degrees C in 12.4%. At 24 99% had cT of > 34 degrees C. Lethality was twice as high (53%) in patients with cT < 32 degrees C as in patients with cT > 34 degrees C (28%). Analysis of correlation revealed that hypothermia was paralleled by a longer rescue time, greater severity of limb injury, and hypoxia. It also appeared that hypothermia is not an independent prognostic factor for posttraumatic lethality. The different effects of hypothermia in trauma and elective surgery may be due to a lack of energy-storing phosphates such as adenosine triphosphate (ATP). Ongoing investigations will identify the role of ATP in trauma-related hypothermia.
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PMID:[The significance of hypothermia in polytrauma patients]. 888 Dec 24

Complete occlusion of blood flow to rat hind limb by tourniquet was used to study the effects of total ischemia for 1, 2, and 3 h on contractile function and metabolic behaviour of two muscles composed predominantly of either fast-twitch (extensor digitorum longus, EDL) or slow-twitch (soleus, SOL) fibres. Percent loss in twitch force (Pt) was greater (p < 0.05) in SOL than EDL during the first 45 min of ischemia. Following 1 h of ischemia, ATP concentration was lower (p < 0.05) than in the contralateral control (20.8 +/- 2.0 vs. 26.4 +/- 1.5 mmol/kg dry weight). Thereafter, the decline in ATP was greater, with approximately 95% depleted by 3 h of ischemia (1.46 +/- 0.46 mmol/kg dry weight). The effect of ischemia on ATP levels in the SOL was similar to ATP levels in the EDL, 1 h of ischemia also resulted in a large decrement in PCr, from 50.1 +/- 2.9 to 11.7 +/- 2.4 mmol/kg dry weight, and a large increase in lactate, from 25.0 +/- 3.0 to 114 +/- 10 mmol/kg dry weight. As ischemia was prolonged, only lactate was increased (p < 0.05) both at 2 h (171 +/- 12 mmol/kg dry weight) and 3 h (208 +/- 5.4 mmol/kg dry weight). Similar trends were found for SOL. By 3 h of ischemia, glycogen was depleted (p < 0.05) by 88% in EDL and 92% in SOL, respectively. These results support the hypothesis that both high energy phosphate transfer and anerobic glycolysis are of major importance in defending ATP hemostasis, particularly during the 1st h of ischemia, and that the resulting metabolic disturbances are responsible for the large fatigability observed. The mechanisms underlying the greater resistance to fatigue observed for the SOL compared with the EDL during the earlier period of ischemia remain uncertain.
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PMID:Metabolic and contractile responses of fast- and slow-twitch rat skeletal muscles to ischemia. 904 44

Ischemia of the distal portion of the latissimus dorsi muscle occurs in muscle transfer for cardiomyoplasty and reduces distal muscle contractility and thus the mechanical effectiveness of cardiomyoplasty. We hypothesized that muscle function would be improved by a vascular delay procedure that increases distal muscle perfusion of the latissimus dorsi muscle. The latissimus dorsi muscles of 10 adult mongrel dogs were subjected to a vascular delay procedure on one side and a sham procedure on the other. Following 10 days of vascular delay, muscle perfusion was measured with a laser-Doppler perfusion imager before and after elevation of the muscles as flaps based only on their thoracodorsal neurovascular pedicles. The muscles were wrapped and sutured around silicone chambers (simulating cardiomyoplasty), a stimulating electrode was placed around each thoracodorsal nerve, and the muscles were stimulated to contract in both rhythmic and tetanic fashion. Circumferential (distal and middle latissimus dorsi muscle function) force generation and fatigue rates were measured independently. Circumferential muscle force, circumferential and longitudinal fatigue rate, and distal, middle, and overall perfusion were significantly (p < 0.05) improved in delayed muscle compared with nondelayed muscle. We found that a vascular delay procedure and a 10-day delay adaptation period significantly improve latissimus dorsi muscle flap perfusion and function, particularly in the distal and middle portions of the muscle. Delay should be considered as a means of improving the clinical outcome in cardiomyoplasty.
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PMID:Vascular delay improves latissimus dorsi muscle perfusion and muscle function for use in cardiomyoplasty. 910 60

Medical issues in sport diving include illnesses that are caused by diving, and medical disorders that compromise safety. Cerebral air embolism and decompression sickness of the brain and spinal cord can result from diving. Sport divers may manifest a spectrum of symptoms from air embolism, which can range from unconsciousness to minimal symptoms, which include fatigue, personality change, poor concentration, irritability, and changes in vision. The physician must search for these minor symptoms in divers who are suspected of pulmonary barotrauma. Medical disorders of concern in diving include diseases of the lungs, the heart, the brain, and the endocrine system, particularly diabetes. Other factors involved in diving safety are exercise capacity and training. Clinical practice standards usually prohibit diving by individuals who have a seizure disorder that requires continuous medication. In the United States, we will not approve diving for individuals who have insulin-dependent diabetes or severe asthma. Some divers can return to diving after myocardial infarction or bypass surgery if they demonstrate good exercise tolerance and no ischemia on a graded exercise test, which simulates the physical activity needed for safe diving.
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PMID:Medical aspects of sport diving. 914 89


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