First, etiology
1Second, acute arterial obstruction
(1)Acute arterial embolism.
(2)Non-occlusive arterial obstruction. Including: ①Acute thrombosis of the abdominal aorta or abdominal aortic aneurysm; ②Femoral artery catheterization during extracorporeal circulation; ③Arterial trauma; ④Blood flow occlusion by clamping during aortic reconstruction.
2Second, ischemic muscle necrosis.
3Second, non-traumatic myopathy, long-term coma, drug toxicity, infection, burn, metal poisoning.
Second, pathogenesis
1h, ischemic changes can appear pale and swollen in the affected limb within a few hours after acute arterial obstruction, in24h, this change is more significant. At this time, cutting the muscle can present a fish-like appearance.24h later, the muscle becomes purple due to congestion, becomes hard, and when the fascia is incised, the still-viable muscle turns pink and herniates out from the incision in the fascia; if it cannot be relieved, after the blood supply is restored, edema will further increase, and at this time, the muscle may present varying degrees of necrosis.
2Under the microscope, in the early stage of the lesion, some muscle fibers can maintain an intact appearance, while some muscle fibers show nuclear deficiency and slight coagulation of the cytoplasm, showing granular changes, which are characteristic changes in the early stage of hypoxia.24h later, some muscle fibers swell and become glassy.48~72h), the damaged local area shows the disappearance of the cross-striations and nuclei of muscle fibers. The specimen after amputation shows: regenerating muscle fibers appear mild to moderate degeneration, even necrosis.
3The skeletal muscle accounts for a certain percentage of the body weight of humans.42About 30% of the muscle tissue contains a large amount of biochemical substances in its complex structure, making it extremely sensitive to hypoxia. Under hypoxic conditions, these biochemical substances are released into the blood, some of which are even fatal to the human body and are the main factors causing MMS. The cell membrane of muscle fiber cells plays an important role in the pathophysiological process of skeletal muscle. When ischemic, the intracellular adenosine triphosphate (ATP) in muscle cells significantly decreases, causing abnormal changes in the permeability of the membrane, resulting in serious destruction of the intracellular and extracellular space configuration of the sarcoplasmic reticulum, causing abnormal transmembrane exchange of various biochemical substances, leading to a series of metabolic syndromes. During the period of blood supply reconstruction and reperfusion, the affected limb produces a large amount of oxygen free radicals, mainly including superoxide anions, hydrogen peroxide, and hydroxyl radicals. Oxygen free radicals are unstable in nature and have strong reactivity, exhibiting cytotoxicity. Oxygen free radicals are very prone to react with thiol enzymes, proteins, lipids, and DNA, etc., destroying the chemical structure of tissue cells, and the polyunsaturated fatty acids in the cell membrane are the most susceptible to the influence of oxygen free radicals, causing changes in the integrity of the biomembrane, further causing biochemical substances in muscle cells to enter the blood, leading to MMS and the necrosis of muscle cells.
4Metabolic syndrome Metabolic syndrome can be transient or persistent, and this syndrome is particularly evident after the reconstruction of blood supply.
(1Metabolic acidosis: It almost occurs in all patients, but the degree is not the same. Metabolic acidosis originates from the accumulation of acidic metabolic products: ischemia and hypoxia of tissues lead to a decrease in aerobic metabolism and an increase in anaerobic glycolysis, producing a large amount of lactic acid and pyruvate. In the early stage,2Acid levels are consistent, and then, the level of lactic acid rises faster than that of pyruvate, blood pH and C02decreased, while the number of anions and cations increased significantly.
(2Electrolyte changes: Serum sodium ions are mostly within the normal range. Potassium ions are also within the normal range in the early stage, and after the reconstruction of blood supply, a large amount of potassium is released from muscle cells into the blood, resulting in a significant increase in blood potassium levels. Sudden removal of the vascular clip may lead to cardiac arrest. Hyperkalemia can cause arrhythmias and cardiac arrest. More than half of the patients have hypocalcemia, hyperphosphatemia, and oliguria. The changes in the calcium-phosphorus ratio during the oliguria period are due to changes in the permeability of the cell membrane of muscle cells. Normally, the concentration of calcium ions in the extracellular fluid is higher than that in the intracellular fluid3~4times. If the cell membrane of muscle cells is damaged, the concentration of calcium ions inside the cell increases until it is equal to the concentration of calcium ions outside the cell, the contractility of muscle cells is enhanced, causing stiffness in the ischemic limb and partial MMS patients to have muscle spasms during renal failure.
(3Enzymatic changes: Before the reconstruction of blood supply, the plasma content of creatine phosphokinase (Creatine Phosphokinase, CPK) is slightly elevated, while the content in the venous blood of the affected limb is very high. After the reconstruction of blood supply, CPK is elevated again. CPK, especially its isoenzyme CPK-MM increased is a direct evidence of muscle damage, and a high level of CPK usually reflects progressive muscle necrosis. At this time, if the skin color is normal, it often leads to erroneous judgments, and intact skin does not reflect the normal muscle tissue underneath. In mild cases, CPK can rise a few hours or1~2days, in more severe cases, CPK can rise within a few days to1000 to2000U,10~12days to return to normal. In severe cases, CPK can rise to2above 10,000 units. In severe and fatal cases, CPK progressively increases to-OxaloaceticTransaminase, SGOT) levels are all elevated. The level of elevation of SGOT is proportional to the degree of ischemia, and the continuous and unrelenting increase of SGOT indicates irreversible pathological damage to the muscle.
(4)Myoglobinurie: Innerhalb weniger Stunden nach der Vasokoklusion nimmt die Harnmenge oft ab, da der Harn Myoglobin enthält, das durch die Spaltung der Skelettmuskulatur freigesetzt wird und eine Kirsche ähnliche Farbe zeigt. Myoglobinurie48h erreicht den Gipfel und hält mehrere Tage an, der Anstieg ist mit dem Umfang und der Schwere der Muskelspaltung verbunden. Das im Harn vorkommende Myoglobin ist ein positiv auf Resorcinphthalein, oder Anilin, oder positiv auf Normalkohol reagierendes Korn, und es gibt keine roten Blutkörperchen im Harn, gleichzeitig ist das Plasma klar. Myoglobinurie wird oft als Hämoglobinurie diagnostiziert. Berman schlägt folgende Differenzialdiagnose vor: rote Plasma+Rote Harnfarbe → Hämoglobinurie; klare Plasma+Rote Harnfarbe → Myoglobinurie. Spezifische qualitativ Bestimmungsmethoden für Myoglobin umfassen: chemische Methode, Spektralphotometrie und Immunologie. Markowiz berichtete über eine quantitative Bestimmungsmethode für Myoglobin im Harn, was die frühe und genaue Bestimmung von Myoglobin im Blut und Harn ermöglicht.
(5)Myoglobinämie: Die Ausscheidung von Myoglobin durch die Nieren kann verzögert sein, in der frühen Phase wird nur eine geringe Menge ausgeschieden, was die Bestätigung der Myoglobinurie schwer macht und zu Fehldiagnosen führt. Daher sollten wir bei Patienten mit hohem Verdacht auf Rhabdomyolyse den Myoglobin im Blut untersuchen, wenn keine Myoglobinämie im Harn nachgewiesen wird.
(6)akute Niereninsuffizienz: Der Schweregrad der Nierenschädigung variiert je nach Ausmaß der Muskelsuffizienz, Azidose und Myoglobinurie. Bei leichten bis mittelschweren Fällen ist die Nierenschädigung nur vorübergehend und reversibel, es gibt eine Reduktion der Harnmenge und die meisten Patienten haben Oligurie oder Anurie. Daraufhin steigt der Bluturinstein und Creatinin schnell an. Bei schweren Fällen tritt eine schwere Azidose mit chronischer Myoglobinurie auf, wenn nicht sofort Dialyse durchgeführt wird, kann es zu irreversiblen Nierenschäden und sogar zum Tod kommen. Histologische Untersuchungen zeigen, dass in den Nierenkanälchen Myoglobin-Kanälchen vorliegen, die eine geringe Anzahl von Epithelzellen enthalten. Der Schweregrad der akuten Tubulärnekrose hängt von dem Ausmaß der Myoglobinblockade der Nierenkanälchen ab, diese pathologische Veränderung wird oft als Myoglobinose der Nieren bezeichnet. Manchmal wirken diese Nierenerkrankungen synergistisch mit renalen Glomerulopathien, was die Prognose erheblich verschlechtert. Nach Daten aus Tierversuchen und Autopsien wird eine mechanische Obstruktion der Nierenkanälle durch Myoglobin mit der akuten Niereninsuffizienz in Verbindung gebracht, ob Myoglobin jedoch direkte toxische Wirkungen auf die Nierenkanälle hat, ist umstritten, da Experimente zeigen, dass die Injektion von Myoglobin keine akute Niereninsuffizienz verursacht.