Microvascular transport and endothelial cell alterations preceding skeletal muscle damage in ischemia and reperfusion injury

We determined the leakage of macromolecules using FITC-dextran-150 as a tracer and measured the extent of no-reflow phenomenon by video field analysis. The cremaster muscle of anesthetized rats was fashioned as a single layer, splayed on a lucite chamber and suffused with bicarbonate solution at 35 degrees C. After a 1 hour period of baseline data collection, ischemia was produced by cross-clamping the cremasteric vascular pedicle for periods of 30 minutes and 2 hours in separate experiments. Macromolecular leakage was visualized after reinstitution of perfusion. Leakage occurred at postcapillary venules 15 to 50 micron in diameter and quickly spread to the interstitium. The magnitude of leakage decreased as a function of time with continuous buffer suffusion, but remained higher than in the control period. No reflow occurred in approximately 30 percent of the muscle microvasculature upon reperfusion. The no-reflow values at 30 minute and 2 hour periods of ischemia were significantly different from the control values but were not from each other. Electron micrographs demonstrated endothelial cell swelling and migration of leukocytes and normal myocytes after 1 hour of reperfusion following 2 hours of ischemia. Our results demonstrate that permeability changes, occurrence of no reflow, and leukocyte migration precede the onset of damage to skeletal muscle in ischemia and reperfusion injury.     

Coronary artery endothelial cell and smooth muscle dysfunction after global myocardial ischemia.

We hypothesized that coronary artery endothelial cell function and smooth muscle function are modified by global myocardial ischemia and used bradykinin-induced secretion of endothelium-derived relaxing factor as a marker of endothelial cell function. Bradykinin and sodium nitroprusside together determined maximum smooth muscle relaxation. Potassium chloride-induced contraction determined smooth muscle contractility. Endothelium-mediated smooth muscle relaxation expressed as a ratio of total coronary smooth muscle relaxation before and after ischemia quantified endothelial cell function. The effect of global normothermic ischemia on in situ coronary arteries from 7 swine hearts was studied. Coronary arterial rings taken from 0 to 220 minutes of ischemia at 20-minute intervals were studied in vitro. The data revealed unexpected tolerance of endothelium-mediated relaxation to ischemia. Endothelium-derived relaxing factor function was maintained to 160 minutes and smooth muscle function, to 120 minutes of ischemia. Coronary artery dysfunction seen in other studies after less ischemia may be the result of injury introduced during reperfusion, may be the consequence of myocardial injury, or may be due to events operative at the level of small arterioles.     

Iloprost attenuates the increased permeability in skeletal muscle after ischemia and reperfusion.

Increased vascular permeability is an early and sensitive indicator of ischemic muscle injury, occurring before significant histologic or radionuclide changes are evident. We investigated the effect of iloprost, a stable prostacyclin analog, on microvascular permeability in a rat striated muscle model. In six control and six experimental animals the cremaster muscle was dissected, placed in a closed-flow acrylic chamber, and suffused with a bicarbonate buffer solution. Dextran labeled with fluorescein was injected intravenously as a macromolecular tracer, and microvascular permeability was determined on the basis of clearance of the fluorescent tracer. Two hours of ischemia were followed by 2 hours of reperfusion. In the experimental group iloprost (0.5 microgram/kg/min) was given in a continuous intravenous infusion. Microvascular permeability increased significantly during reperfusion in both control and experimental animals (p less than 0.0001). Treatment with iloprost, however, significantly attenuated this response compared to the control group, 4.8 +/- 0.3 versus 7.3 +/- 0.5 microliters/gm/min, respectively (p less than 0.0001). Iloprost decreases the rise in vascular permeability after ischemia and reperfusion. Experimental clinical use of iloprost under controlled conditions in the treatment of patients with acute skeletal muscle ischemia appears justified.     

Metabolic alterations of skeletal muscle tissue after prolonged acute ischemia and reperfusion.

Acute tissue ischemia is usually followed by considerable disturbances of cellular metabolism that often lead to cell death. Reperfusion improves cellular function by withdrawing the toxic products of ischemia and providing energy sources, although sometimes it worsens it. The purpose of this experimental work is to study the metabolic disturbances in skeletal muscle tissue of canines after prolonged acute ischemia in relation to the values of certain substances (ATP, lactate, pyruvate, the ratio of lactate to pyruvate [L/P], and glucose) and whether the alterations in the values of these substances could be used as prognostic indices of the magnitude of tissue damage and the possibility of inverting it. We used 15 mongrel dogs. Complete acute ischemia was induced in the right lower limb lasting 12 h. Reperfusion also lasted for 12 h. The left lower limb was used as reference value. Before the beginning of ischemia, at (1/2), 1, 6, and 12 h after the induction of ischemia, and at (1/2), 1, 6, and 12 h after the restoration of circulation, blood samples, and tissue biopsies were obtained from the healthy and the experimental limb for the measurement of ATP, lactate, pyruvate, the ratio of L/P, and glucose. From the statistical analysis of the values of the controlled parameters the following were concluded: The changes in ATP, lactate, pyruvate, and the L/P ratio in the venous blood of the experimental limb and in the intracellular space of the suffering skeletal muscle could be used as indices to evaluate ischemic injury to the skeletal muscles, the course of its development, and the possibility of reversal after reperfusion.     

Interleukin-1 and thromboxane release after skeletal muscle ischemia and reperfusion

Interleukin-1 and thromboxane are known to mediate the host response to sepsis, trauma, and myocardial ischemia. A well-established model of canine isolated gracilis muscle was used to evaluate whether cytokine (interleukin-1) played a role in skeletal muscle ischemia-reperfusion injury. Six adult mongrel dogs (25–30 kg) were subjected to six hours of muscle ischemia followed by reperfusion. Gracilis venous samples were collected pre-ischemia and at one hour of reperfusion. Systemic (arterial) blood samples were taken at one hour of reperfusion. Sera were analyzed for interleukin-1 by bioassay and thromboxane (B₂) by radio-immunoassay. The gracilis muscle of the operated limb was harvested in all the animals for assessment of the percentage of muscle necrosis. This was found to be 56.2±14.8% by serial transections, nitroblue tetrazolium staining, and computerized planimetry. Interleukin-1 levels in the gracilis venous effluent increased from 21.88±7.13 units/ml during pre-ischemic baseline to 50.42±9.12 units/ml after six hours of ischemia followed by one hour of reperfusion (p<0.04). Thromboxane B₂ levels were 2983±1083 pg/ml and 9483±2218 pg/ml at pre-ischemia and at one hour of reperfusion respectively (p<0.04). Systemic levels of both interleukin-1 and thromboxane B₂ at one hour of reperfusion were 0 units/ml and 1584±520 pg/ml respectively, which were significantly lower than the one hour reperfusion gracilis venous effluent levels (p<0.04). This is the first report in which cytokines have been implicated in skeletal muscle ischemia-reperfusion injury. Modulation of interleukin-1 may impact positively on muscle necrosis and systemic manifestations of reperfusion injury.Presented at the 16th Annual Meeting of the Peripheral Vascular Surgery Society, June 2, 1991, Boston, Massachusetts.     

Free radical injury in skeletal muscle ischemia and reperfusion.

This study was made in a canine isolated gracilis muscle model to measure directly the free radicals, to predict the severity of ischemia and reperfusion injury of the skeletal muscle by measuring its surface pH (mspH), and to determine the effect of Coenzyme Q10 (CoQ10) in reducing the extent of muscle injury. Animals were divided into three groups: group A (control, n = 10), group B (untreated, n = 10), and group C (CoQ10 treated, n = 10). In both groups B and C, 5 hr ischemia followed by 40 min of reperfusion was made. Free radicals were measured directly by electron spin resonance spectrometer (ESR) and mspH was measured using a pH microprobe. Serum creatine phosphokinase (CPK) was estimated before ischemia, 5 and 30 min after reperfusion. The extent of muscle injury was evaluated morphologically by Evan's blue dye exclusion test. ESR intensity in group B was 0.55 +/- 0.19 and decreased to 0.30 +/- 0.04 in group C (P less than 0.01). Rate of recovery of mspH was higher in group C (7.16 +/- 0.06) compared to group B (6.88 +/- 0.11, P less than 0.01) and CPK in group C was less (847 +/- 381 IU/liter) than in group B (1356 +/- 519 IU/liter, P less than 0.05) after 30 min of reperfusion. In group C the morphological muscle injury was less (37.8 +/- 5%) compared to group B (56.7 +/- 3.6%, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of ischemia reperfusion injury on skeletal muscle

Ischemia reperfusion (IR) injury occurs when tissue is reperfused following a period of ischemia, and results from acute inflammation involving various mechanisms. IR injury can occur following a range of circumstances, ranging from a seemingly minor condition to major trauma. The intense inflammatory response has local as well as systemic effects because of the physiological, biochemical and immunological changes that occur during the ischemic and reperfusion periods. The sequellae of the cellular injury of IR may lead to the loss of organ or limb function, or even death. There are many factors which influence the outcome of these injuries, and it is important for clinicians to understand IR injury in order to minimize patient morbidity and mortality. In this paper, we review the pathophysiology, the effects of IR injury in skeletal muscle, and the associated clinical conditions; compartment syndrome, crush syndrome, and vascular injuries.     

常温肝缺血再灌注肝血窦内皮细胞损伤

目的 探讨肝脏常温 因再灌注稆肝血窦内皮细胞的结构变化及其在再灌注损伤中的作用。方法 将４４只大鼠在常温下分别阻断人肝血流２０、４０、６０和９０ｍｉｎ,然后再开放血流２ｈ,制备成缺血再灌注模型,对肝血窦内皮细胞进行扫描和透射电镜观察,正常对照组大鼠５只。结果 肝血流阻断２０、４０ｍｉｎ时内皮细胞受损;血流开放后２ｈ内皮变化可恢复。肝血流肝断６０、９０ｍｉｎ后内皮细胞出现损伤,使部分内皮缺损,上直接     

Tourniquet-induced ischemia and reperfusion in human skeletal muscle

Microdialysis conceivably enables longitudinal and simultaneous investigation of several metabolites by repeated measurements in skeletal muscle. We used and evaluated microdialysis as an in vivo method to characterize the time-course and relative kinetics of pyruvate, glucose, lactate, glycerol, hypoxanthine, uric acid, and urea, in skeletal muscles, exposed to ischemia and reperfusion, in eight patients having arthroscopic-assisted anterior cruciate ligament reconstruction. A dialysis probe was implanted before surgery in the rectus femoris muscle. Dialysate samples were collected at 10-minute intervals at a flow rate of 1 microL/minute until 2 hours after tourniquet deflation. Ninety minutes of ischemia resulted in accumulation of lactate (234% +/- 38%), hypoxanthine (582% +/- 166%), and glycerol (146% +/- 46%), consumption of glucose (54% +/- 9%) and pyruvate (16% +/- 44%), and a slight decrease of urea (78% +/- 11%) compared with baseline (100%). Uric acid was unchanged (95% +/- 12%). Within 90 minutes after tourniquet deflation the concentrations were virtually normalized for all measured metabolites, suggesting that the duration of ischemia was well tolerated by the patients. The results indicate that the use of microdialysis for monitoring energy metabolic events during orthopaedic surgery that requires ischemia and reperfusion is feasible and safe.     

Differential recovery of skeletal muscle and peripheral nerve function after ischemia and reperfusion

Recovery of skeletal muscle function is of prime importance in revascularization of acutely ischemic extremities. In order to study the effect of ischemia and reperfusion on peripheral nerve and skeletal muscle function, temporary unilateral hindlimb ischemia (1 or 3 hr) was induced in 12 rabbits by temporary arterial occlusion of common iliac and femoral arteries and collateral ligation. The control limb was similarly prepared without interruption of blood flow. Both anterior tibialis muscles were attached to force transducers, and the twitch and tetanic tensions were measured at the end of the ischemic interval and during reperfusion (2 hr) by either direct muscle stimulation or stimulation of the deep peroneal nerve. The ischemic limb was reperfused by removal of arterial clamps and reperfusion documented by Doppler flow over the vascular pedicle. The recovery of muscle function of the ischemic/reperfused limb relative to that of the contralateral control limb was used as the index of recovery. By the end of the ischemic interval, no contractile activity was elicited with nerve stimulation for either the 1- or the 3-hr group. After 2 hr of reperfusion, the 1-hr group regained 0.558 +/- 0.116 (mean +/- SEM) of control function with nerve stimulation, while the 3-hr group regained only 0.016 +/- 0.005 of control function (P less than 0.01). In contrast, with direct muscle stimulation, the 1-hr group produced 0.580 +/- 0.015 compared to 0.286 +/- 0.042 (P less than 0.001) after 3 hr of ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of arachidonic acid metabolites on leukocyte activation and skeletal muscle injury after ischemia and reperfusion.

Derivatives of arachidonic acid have been found to play a role in the reperfusion injury of various tissues. These compounds have a broad spectrum of activity, including modulation of white blood cell response to injured tissue. This study was designed to determine the effect of thromboxane and lipoxygenase derivatives on the local and systemic response to ischemia and reperfusion of skeletal muscle. Fifteen dogs were separated into three groups and subjected to gracilis muscle ischemia followed by 2 hours of reperfusion. One group served as controls, one group was treated with OKY-046 (a thromboxane synthetase inhibitor), and one group was treated with diethylcarbamazine (a lipoxygenase inhibitor). White blood cell activation as measured by superoxide anion production, and eicosanoid levels were measured both in the gracilis venous effluent and central venous circulation. These results were compared to infarct size in the gracilis muscle. OKY-046 significantly reduced thromboxane production in both the central venous (102 +/- 30 to 31 +/- 9 pg/ml, p less than 0.05) and gracilis samples (107 +/- 22 to 25 +/- 6 pg/ml, p less than 0.005). This was accompanied by a reduced white cell activation in the central venous blood (15 +/- 1 to 10 +/- 1 nmol O2-, p less than 0.05), but did not affect infarct size or white cell activation in the gracilis. Conversely, diethylcarbamazine significantly reduced both white cell activation (16 +/- 1 to 10 +/- 1 nmol O2-, p less than 0.005) and infarct size in the gracilis muscles (61.6% +/- 4.5% to 28.5% +/- 8.6%, p less than 0.01), as well as reduced systemic white blood cell activation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pravastatin attenuates tourniquet-induced skeletal muscle ischemia reperfusion injury

Background Revascularization of a limb following prolonged ischemia results in substantial skeletal muscle injury. Statins play a well-understood role in the treatment of hypercholesterolemia but are also known to have anti-inflammatory properties. The purpose of this study was to examine the effects of pravastatin pre-treatment in the setting of skeletal muscle ischemia reperfusion injury (IRI).

Methods Adult male Sprague Dawley rats (n = 27) were randomized into 3 groups: control group, I/R group, IR group pre-treated with pravastatin. Bilateral hind-limb ischemia was induced by rubber band application proximal to the level of the greater trochanters for 2.5 h. Treatment groups received normal saline in equal volumes prior to tourniquet release. Following 12 h reperfusion, the tibialis anterior muscle was dissected and muscle function assessed electrophysiologically by electrical field stimulation. The animals were then killed and skeletal muscle harvested for evaluation.

Results We found that pre-treatment with pravastatin reduces the tissue oxidative damage and edema associated with skeletal muscle reperfusion injury. Skeletal muscle injury, measured by edema, leucose-questration and electrical properties were significantly lower with pravastatin pre-treatment compared to the non-treated group.

Interpretation We feel that pravastatin pre-treatment may be a potential therapeutic intervention for skeletal muscle ischemia reperfusion injury in the clinical setting. ▪     

Pravastatin attenuates tourniquet-induced skeletal muscle ischemia reperfusion injury

Background?Revascularization of a limb following prolonged ischemia results in substantial skeletal muscle injury. Statins play a well-understood role in the treatment of hypercholesterolemia but are also known to have anti-inflammatory properties. The purpose of this study was to examine the effects of pravastatin pre-treatment in the setting of skeletal muscle ischemia reperfusion injury (IRI).

Methods?Adult male Sprague Dawley rats (n = 27) were randomized into 3 groups: control group, I/R group, IR group pre-treated with pravastatin. Bilateral hind-limb ischemia was induced by rubber band application proximal to the level of the greater trochanters for 2.5 h. Treatment groups received normal saline in equal volumes prior to tourniquet release. Following 12 h reperfusion, the tibialis anterior muscle was dissected and muscle function assessed electrophysiologically by electrical field stimulation. The animals were then killed and skeletal muscle harvested for evaluation.

Results?We found that pre-treatment with pravastatin reduces the tissue oxidative damage and edema associated with skeletal muscle reperfusion injury. Skeletal muscle injury, measured by edema, leucose-questration and electrical properties were significantly lower with pravastatin pre-treatment compared to the non-treated group.

Interpretation?We feel that pravastatin pre-treatment may be a potential therapeutic intervention for skeletal muscle ischemia reperfusion injury in the clinical setting.??     

Isovolemic hemodilution and skeletal muscle function during ischemia and reperfusion

Hemodilution has previously been shown to improve microcirculation in skeletal muscle after ischemia. We have studied the effects of isovolemic hemodilution with dextran on the function of anterior tibial muscle in the rabbit. Hemodiluted (hematocrit 28%) and nonhemodiluted animals were compared. Hemodilution led to an immediate increase in femoral blood flow. Flow normalized within 1–2 h, possibly due to flow redistribution. Hemodilution increased muscle force by 10%, which can reflect alterations in blood chemical composition or an improved microcirculation. Unilateral hindlimb ischemia induced by arterial occlusion inhibited muscle force to less than 15% in 150 min. Force and blood flow recovered almost completely after ischemia. After longer ischemia (170–300 min) when force was <5%, muscles did not recover. Hemodilution did not alter the muscle force or the extent or rate of force recovery after ischemia, which shows that the increased blood flow and improved microcirculation are not directly associated with changes in the sensitivity of muscle function to ischemia. © 1998 Wiley-Liss, Inc. MICROSURGERY 18:79-85 1998     

Quantitative histochemical evaluation of skeletal muscle ischemia and reperfusion injury

Acute arterial obstruction to the extremities is associated with significant morbidity and mortality. The evaluation of accompanying skeletal muscle injury has thus far been indirect and imprecise. Triphenyltetrazolium chloride (TTC) is an oxidation-reduction indicator which allows for the histochemical quantitation of skeletal muscle injury. In 21 anesthetized nonheparinized adult mongrel dogs, the isolated in vivo gracilis muscle underwent 4, 6, or 8 hr of ischemia with and without reperfusion. The muscles were excised and cut into 1-cm segments, representative muscle biopsies for electron microscopy were taken, each segment was stained in 1% TTC, and the total area of staining was measured with computerized planimetry. All control muscles stained completely with a dark red color. After 4, 6, or 8 hr of ischemia, quantitative measurements of muscle staining indicative of normal tissue were present in 98 +/- 1%, 59 +/- 5%, and 23 +/- 9% of the total muscle areas, respectively. Six hours of ischemia followed by reperfusion was associated with only 36 +/- 9% of the muscle being stained. Segmental TTC staining demonstrated that reperfusion was associated with greater injury, and less TTC staining, in the proximal portion of the gracilis muscle at the site of entry of the major arterial pedicle. The distal muscle did not demonstrate increased damage with reperfusion. It is hypothesized that protection of the distal muscle from reperfusion injury may be due to an absence of reflow farther away from the artery.     

Endothelin-1 is upregulated during skeletal muscle ischemia and reperfusion

The aim of the present study was to test the hypothesis that the vasoconstrictive peptide endothelin-l is upregulated in ischemia and reperfusion in skeletal muscle. Sixty-eight Wistar rats were included in the series: 12 served as controls that did not undergo the procedure, 16 underwent sham operations, and 40 were subjected to a modified tourniquet ischemia for 3 hours and 20 minutes. Of the 40 rats, 16 were killed at the end of the ischemic period, 16 underwent reperfusion for 2 hours, and eight underwent reperfusion for 72 hours. Areas of necrosis were measured by morphometry in hematoxylin and eosin-stained cross sections of the anterior tibial muscles that had been reperfused for 72 hours. Sections from the controls, the muscles that had not been reperfused and the reperfused muscles were immunostained for endothelin-1. Serum endothelin-1 levels in blood samples from the aorta were determined with a commercial enzyme immunoassay kit. The anterior tibial muscle was harvested for preproendothelin-1 mRNA analysis with RNase protection assay. The hematoxylin and eosin-stained sections showed extensive necrosis with an acellular core of no reperfusion. The muscular core demonstrated weak immunostaining for endothelin-1 in all sections, a subfascial narrow brim of fibers showed enhanced immunoreactivity at the end of ischemia, and all fibers outside the core stained by 2 hours after the start of reperfusion. After 72 hours of reperfusion. the fibers outside the core stained positive in a checkerboard-like pattern. There were no differences in serum endothelin-1 levels between the groups. Preproendothelin-1 mRNA analysis with RNase protection assay showed 2-fold upregulation at the end of ischemia and 4-fold upregulalion'after 2 hours of reperfusion (p = 0.001). This study supports the hypothesis that both ischemia and reperfusion upregulate endothelin-1 in skeletal muscle.     

缺血预处理减轻骨骼肌缺血再灌注损伤

目的 观察缺血预处理对骨骼肌缺血再灌注损伤的保护作用。方法 选择２４只健康兔,随机等分为实验组和对照组。实验组先进行缺血预处理,再持续阻断后肢血流４ｈ;对照组直接阻断后肢血流４ｈ,制作骨骼肌缺血再灌注损伤模型。测定再灌注期血清中肌酸磷酸激酶（ＣＰＫ）和天门冬氨酸氨基转移酶（ＡＳＴ）,镜下观察骨骼肌变化。结果 实验组血清中ＣＰＫ和ＡＳＴ的含量均明显低于对照组（Ｐ〈０．０５）。实验组骨骼肌线粒体空泡变     

The pathophysiology of skeletal muscle ischemia and the reperfusion syndrome: a review

There are two components to the reperfusion syndrome, which follows extremity ischemia. The local response, which follows reperfusion, consists of limb swelling with its potential for aggravating tissue injury and the systemic response, which results in multiple organ failure and death. It is apparent that skeletal muscle is the predominant tissue in the limb but also the tissue that is most vulnerable to ischemia. Physiological and anatomical studies show that irreversible muscle cell damage starts after 3 h of ischemia and is nearly complete at 6 h.These muscle changes are paralleled by progressive microvascular damage. Microvascular changes appear to follow rather than precede skeletal muscle damage as the tolerance of capillaries to ischemia vary with the tissue being reperfused. The more severe the cellular damage the greater the microvascular changes and with death of tissue microvascular flow ceases within a few hours-the no reflow phenomenon. At this point tissue swelling ceases.The inflammatory responses following reperfusion varies greatly. When muscle tissue death is uniform, as would follow tourniquet ischemia or limb replantation, little inflammatory response results. In most instances of reperfusion, which follows thrombotic or embolic occlusion, there will be a variable degree of ischemic damage in the zone where collateral blood flow is possible. The extent of this region will determine the magnitude of the inflammatory response, whether local or systemic. Only in this region will therapy be of any benefit, whether fasciotomy to prevent pressure occlusion of the microcirculation, or anticoagulation to prevent further microvascular thrombosis. Since many of the inflammatory mediators are generated by the act of clotting, anticoagulation will have additional benefit by decreasing the inflammatory response. In instances in which the process involves the bulk of the lower extremity, amputation rather than attempts at revascularization may be the most prudent course to prevent the toxic product in the ischemic limb from entering the systemic circulation.