动物模型 z-bo 2020-08-10 544

　　Blood loss is one of the most common causes of anemia in the body, which can be divided into acute and chronic clinically. Chronic blood loss often causes iron deficiency anemia. Anemia caused by blood vessel rupture or hemostatic mechanism defects caused by trauma or disease process, a large amount of blood loss in a short time is called acute hemorrhagic anemia. The main causes of acute blood loss are: various traumas and bleeding during surgical operations, gastrointestinal hemorrhage, various obstetrics and gynecology hemorrhages, bleeding when internal organs rupture, massive lung or bronchial hemoptysis, inflammation, tumors, etc. caused by invasion of the blood vessel wall Sudden bleeding and bleeding caused by various diseases with defective hemostasis mechanisms. Acute blood loss can directly cause a decrease in the body's circulating blood volume and lower arterial blood pressure. Due to the stimulation of chemoreceptors and adrenaline, the pressor reflex is deepened, and the body redistributes the circulating blood under the action of neurohumoral. Except for the brain and heart, the blood vessels of other organs in the body, especially the abdominal internal organs, skin and muscles are all contracted, so the peripheral resistance increases and the heart rate increases to keep the blood supply to the vital organs in the body as much as possible. In addition, because of the strong response of the contraction of the capillary resistance, the blood pressure of the capillary is reduced, and the tissue fluid enters the capillary. At the same time, due to the decrease in renal blood flow, the patient's urine excretion decreases. Through these compensatory effects, blood volume is gradually replenished. Blood loss also loses blood cells. With the supplement of blood volume, blood dilution, red blood cell and hemoglobin concentration decreases, tissue hypoxia occurs, the compensatory secretion of erythropoietin in the body increases, which promotes bone marrow hematopoietic function and releases more red blood cells. If the blood loss is too much and the blood volume is reduced by 1/3, the cardiac output and arterial pressure drop drastically, and the blood volume cannot be supplemented in time, which will eventually lead to shock. In the process of shock, disseminated intravascular coagulation (DIC) can be caused due to metabolic disorders of organs and tissues, acidosis, and capillary wall damage. As a result, shock becomes irreversible and leads to death. Compensation after blood loss takes a certain amount of time, so the clinical manifestations are determined by the amount and speed of blood loss, whether there are complications, and the patient's psychological status, body position, age, nutritional status, cardiovascular function, etc., in addition to individual status. When the bleeding volume increases to 1500-2000ml (about 40% of the total blood volume), even if the patient is healthy before bleeding and rests in bed after bleeding, he still suffers from thirst, nausea, shortness of breath, extreme dizziness and even temporary loss of will. Due to the redistribution of blood circulation, the patient has cold hands and feet, pale complexion, and decreased urine output. Blood pressure, cardiac output, and central venous pressure are all decreased, pulse is fast and weak, and the patient complains of headaches, and gradually develops shock symptoms such as restlessness, dyspnea, poor pulse, clammy skin, nausea and vomiting, and finally coma. Commonly used experimental animals in animal models of hemorrhagic anemia are mice, rats, rabbits and dogs.

　　(1) Copy method

　　1) Mouse hemorrhagic anemia model

　　The commonly used methods of mouse modeling mainly include the posterior orbital venous plexus bleeding method and the tail tip or tail artery incision method.

　　①Retroorbital venous plexus bleeding method: Fix the mouse with the left hand and gently apply pressure on the neck to make the head vein congestion, distinguish the posterior orbital vein beside the prominent eyeball, and then instill a small amount of 10% cocaine into the animal's eye , To make the eyes local anesthetized; the right hand holds the sterilized capillary pipette from the inner corner of the eye from the nasal orbit parallel to the larynx to the posterior orbital venous plexus, the blood is naturally sucked into the tube, and 6-8 drops (about 0.5ml) of blood are let out. The capillary pipette has an inner diameter of 0.5-1.0mm and can be made of polyvinyl chloride tube or glass capillary tube. The capillary tube forms a 45° angle with the mouse surface during blood collection. In the lacrimal region, the inner corner of the eye penetrates between the eyelid and the eyeball toward the throat. If it is a needle, the inclined surface is first toward the eyeball, and then rotated at an angle of 180° to make the inclined surface face the posterior orbital boundary. The penetration depth is 2 to 3 mm. When it reaches the sphenoid bone and feels resistance, it is later retracted by 0.1 to 0.5 mm. Draw while retreating. Keep the blood vessel in a horizontal position, rotate it slightly and back to attract. Due to blood pressure, blood will automatically flow into the suction tube. After the required blood vessel is obtained, the pressure on the neck will be removed, and the blood collection tube will be pulled out to prevent bleeding from the puncture hole after the operation. And use sterile gauze or cotton ball to compress the eyeball to stop bleeding 30s. Generally, 0.5ml of blood is drawn from the orbital venous plexus for each mouse weighing about 20g. Such as bleeding once every other day, 5 consecutive times can form a chronic hemorrhagic anemia model. An acute hemorrhagic anemia model was formed 24h after blood loss.

　　② Tail tip or cut tail artery method: mouse tail cut and bleeding: rub the tail with hands or warm the tail with warm water (45～50℃) to make it fully congested, then cut the tail tip about 2mm with scissors. Gently squeeze from the root of the tail to the tip of the tail with your hands, so that the blood loss reaches about 0.5ml.

　　2) Rat hemorrhagic anemia model

　　The general rat model includes the heart bleeding method and the vein multiple bleeding method.

　　① Rat heart bloodletting: blood is drawn from the heart, the blood volume is about 1/4 of the total blood volume. Blood collection method from rat heart: Place the animal on its back on a fixed board, cut off the coat on the chest area, and disinfect the skin with iodine tincture and ethanol. In the 3rd and 4th intercostal space on the left, use the index finger of your left hand to touch the heartbeat, and hold the syringe with the 4 to 5 gauge needle in your right hand, and choose the strongest point of the heartbeat. When the needle pierces the human heart, blood automatically enters the syringe due to the force of the heartbeat. Heart blood collection is about 1/4 of the total blood volume (total blood volume is calculated as 6% of body weight).

　　② Rat tail vein multiple bloodletting method: Rats weighing 180-200g, bloodletting 1.5-2ml per rat from the tail, once every other day for 5 consecutive times, can be made into a chronic hemorrhagic anemia model.

　　3) Rabbit or dog hemorrhagic anemia model

　　The animal is fixed on the operating table in the supine position after conventional anesthesia, the femoral artery or carotid artery is separated by aseptic operation, intubated, and the amount of bleeding is counted one or more times according to the animal's weight. One-time bloodletting of rabbits accounts for 30% of the total blood volume, and bloodletting of dogs at 40ml/kg body weight can be repeated several times to cause hemorrhagic anemia.

　　(2) Model characteristics The above several modeling methods have simple blood loss methods, clear indicators, no special equipment, but the blood loss is difficult to be completely consistent. It can be used for pharmacodynamic screening of new drugs for general iron deficiency anemia, and the iron deficiency (hemorrhagic) anemia model is more reasonable. The indicators of successful modeling are the decline of RBC and Hb, which are significantly different from those before bloodletting. It is worth noting that the tail of the mouse should be fully congested when bleeding from the tail artery of the mouse, otherwise it is difficult to achieve the required amount of bleeding. When a sufficient amount of blood is collected from the orbit, a sterile cotton ball should be used to compress the eyeball to stop bleeding.

　　(3) Comparative medicine Common laboratory animals such as rodents, rabbits, dogs, etc. can replicate hemorrhagic anemia models, and the modeling methods are simple and reliable. However, the use of different animals to make models differs greatly in terms of operation methods and production costs, and model animals should be selected according to the purpose of the experiment.