动物实验,延迟复苏 z-bo 2020-09-03 421

　　Background: Delayed resuscitation is a new method of resuscitation for trauma patients, which provides more time for surgical hemostasis and further treatment. False death is a process that causes the life process to be delayed or terminated by internal or external means without termination. Hypothermia has been used to complete brain protection in heart surgery, complicated congenital heart disease and aortic arch surgery. SADR uses hypothermia during cardiopulmonary bypass, which saves transportation time, controls surgical injuries and delays resuscitation. In the past three years, various conclusions have been drawn based on preclinical studies of SADR in different animal models. At low temperatures (10°C), the cleaning solution uses glucose and oxygen, and it can completely recover after 180 minutes of stopping the circulation (CA). A short CA time interval can achieve good recovery. 90 minutes of low flow or 60 minutes of no flow, and then delayed recovery can restore the pig model. After resuscitation in the rat model, high mortality and multiple organ failure, including renal failure and liver necrosis, were observed. Since the heart, lung and immunophysiology of pigs are very similar to humans, studying cold damage in pig models is the most valuable for understanding human treatment. In addition, compared with other primates, the pig model's physiological response to bleeding is closer to that of humans. After the heartbeat was completely stopped, the organ preservation solution (ΔOPS) and SADR in the blood were evaluated at 15°C, and the survival and nervous system of the animal model were evaluated at about 90 minutes and 120 minutes. Method: 16 male Parmani pigs weighing 41-76 kg were randomly divided into two groups: ca90 group (n = 8), total cardiac arrest for 90 minutes, ca120 group (n = 7), 120 minutes Complete cardiac arrest (a pig died at the end of CPB due to blunt aortic injury to the femoral artery catheter). In the evening, ketamine (10 mg/kg) was injected intramuscularly on an empty stomach for sedation. After placing the tracheal tube, anesthetize the animal with a breathing anesthesia machine (isoflurane 0.5-1.0%). Right femoral artery and venous cannula are used for 22G catheter and 5F double lumen central venous catheter. Monitoring arterial pressure and central venous pressure by puncture. After the animals were heparinized (300 U/Kg), a 16F femoral artery catheter and 18F femoral vein cannula were inserted into the right common carotid artery and internal jugular vein. Establish cardiopulmonary bypass. Anesthetize the animal and switch to full ventilation support. Maintain PaCO2 at 35-40 mmHg and maintain minimal ventilation. Keep the oxygen concentration (FiO2) as low as possible to keep the pulse oximetry reading above 95%.

　　Bleeding: Animal bleeding from the femoral vein, as well as bleeding (mean arterial pressure (MAP) rapidly drops to 30 mmHg) and simulated laceration. The blood is collected in the bag and injected automatically. All animals maintained low perfusion levels within 30 minutes and lost 1000-1500 ml of blood.

　　Extracorporeal Circulation (CPB), inducing deep body temperature circulation: Centrifugal pump, heat exchanger, ECMO packaging form a portable cardiopulmonary support system (PCSS) to protect the entire body. The entire system provides 600 ml of organ preservation solution (OPS). Two types of OPS (normal potassium and high potassium) are used. The use of femoral artery catheters and 1.4 L high potassium OPS, 3-4 L/min for complete cardiopulmonary bypass surgery can lead to transient cardiac arrest. The temperature of the heat exchanger can be reduced as quickly as possible. When the core body temperature reaches 20°C, replace 2L of normal OPS with 2L of blood. When the core temperature reaches 15°C, the flow will stop and the animation will pause. The blood is discharged from the venous catheter by gravity and collected in an automatic blood transfusion bag. After about 90 or 120 minutes, increase the flow rate to 3-4 liters/minute, and adjust the arterial return temperature to achieve the desired reheating rate (0.5°C/minute). As the core temperature increases, all collected blood gradually recovers to accommodate the increased oxygen demand. You can also correct electrolyte and acid-base abnormalities as needed. The spontaneous activity of cardiomyocytes can usually be restored by reversing hyperkalemia and hypothermia. After a short stabilization period, the animal gradually leaves the cardiopulmonary bypass and reverses heparin with protamine sulfate. When the animal is breathing normally, all incisions are sutured and the cannula is removed. Flurbiprofen axetil was injected intravenously to relieve pain, and antibiotic cefuroxime sodium was given perioperatively for 24 hours. Except for the difference in CA time, all animals are treated the same. Before the experiment, 3 animals were used to develop the details of the experimental method.

　　Laboratory measurement and neurological function test: blood is drawn to measure liver enzymes (ALT, AST), renal function (creatinine) and markers of myocardial damage. The overall performance category (OPC index) is used to assess the neurological condition (1=normal, 2=mild disability, 3=moderate disability, 4=severe disability) at 7 days postoperatively, 5=death or brain death). Hemodynamic and physiological parameters: Femoral venous catheter bleeding can cause a rapid decline in animal MAP. The animals are still deeply shocked. Injection of refrigerant into the right carotid artery may cause the autonomous heart to stop, but there is no approximate intrinsic cardiac output. At the end of the experiment, the cardiac output of the two groups of animals returned to the baseline level. The reversal of hyperkalemia and hypothermia restored spontaneous activity. There was no difference between the two groups receiving cardioversion or antihypertensive drugs. Low-dose epinephrine (0.5 mg intravenously, maximum dose 2 mg) can be used for hypotension and bradycardia. The lactic acid and blood glucose levels of the ca90C group were lower than the ca120 off-pump bypass point. This may be due to the longer CA. The cooling and heating rates of the two groups are the same. Survival and nervous system: In the ca90 group, all experimental animals survived 72 hours after surgery. Only one showed paralysis of the right leg, possibly due to ligation of the right femoral artery. In the ca120 group, only two survivors showed hind limb paraplegia. 48 hours after the operation, three about 120 pigs died of respiratory failure. Two pigs died during the operation without spontaneous neural activity or reflexes. All animals in the ca90 group had an OPC score of 1, OPC score of 2, and in the ca120 group, only 2 animals recovered to OPC4, and the other 5 animals were classified as OPC5 (P\u003c0.05). Postoperative examination: In the ca90 group, postoperative biochemical abnormalities (ALT, AST, Cr, LDH, TNT) were transient. Abnormalities include elevated liver transaminase, creatinine levels, lactate dehydrogenase, and TNT on the first postoperative day. After 7 days, these levels dropped to normal or close to normal. There was no significant difference in the ca120 group. On the first day after surgery, the biochemical indexes of the ca120 group were higher than those of the ca90 group.

　　Conclusion: 90 minutes of CA induction (15°C) is safer than 120 minutes. The results show that 120 minutes of CA at 15°C is dangerous and may cause high mortality and serious neurological complications. Further experiments are needed to determine whether the 120-minute CA can be safely recovered at temperatures below 15°C.