| Background and objective Cardiac arrest(cardiac arrest, CA),as the most common cause of death in most parts of the world, refers to the heart suddenly failing to eject blood and the effective blood flow falling sharply.Ischemic hypoxemia occurs in the vital organs such as the heart and the brain of the CA patients. Every year,thousands of people die from CA, and CA incidence rate in some developed countries is about (36 to 128)/100,000;every year sudden cardiac death can lead to 54.4 million people's deaths in domestic area, and the CA incidence rate is about 41.84/100,000. The success rate of recovery is still low. The most recent literature demonstrated that the rate of defibrillation succession within our country's hospital is about 25.5%,and hospital discharge rate only 6.5%.Although 20 to 50% of 500,000 CA patients were able to recover spontaneous circulation in North America when receiving CPR (cardiopulmonary resuscitation, CPR), only 2% to 15% survive and discharge from the hospital. The evidence above suggests that there is a high incidence rate and case fatality rate in CA patients. We describe the common causes of CA as follows:?sudden accidents:such as suffocation and severe trauma. ?structural heart disease:ischemic heart disease and acute myocarditis can lead to CA commonly.?poisoning or allergies resulting from digitalis, procaine,penicillin, streptomycin and some serum products.?the accident in process of surgery and anesthesia:such as coronary arteriography and abdominocentesis.?severe electrolyte imbalance:such as hyperkalemia and hypokalemia. ?Other reasons:all kinds of shock and airway obstruction. BLS is the most basic way to rescue patients with CA, and early CPR which is being internationally recognized as the current standard treatment for CA patients is the most important content of BLS.No matter whatever the cause of CA is, its success rate of recovery is still low,and the survival rate in patients is not ideal. Therefor,in order to improve the survival rate of patients with CA, CPR emergency physicians and researchers have been on a mission of exploring the new technology and new methods of the CPR.Successful CPR is dependent on the re-establishment of myocardial blood flow. The coronary perfusion pressure (CPP),the most reliable predictor of restoration of spontaneous circulation(ROSC),is a hot spot of research. However,hemodynamic mechanism based on heart pump theory and breast pump theory is widely used in the update of CPR guidelines and the design of resuscitative instrument. Nevertheless,because of the influence of various objective factors and decreasing chest compression rate and depth due to the increasing fatigue of rescuer, the CPP raised by CPR is not enough.At present, although resuscitative methods such as epinephrine and abdominal compression and so on are used for raising the CPP during CPR,there are lots of shortcomings in these methods.Epinephrine, which has been routinely administered during CPR,can transiently increase both CPP and cerebral perfusion pressure and thereby facilitate restoration of spontaneous circulation. However, epinephrine is like a double-edged sword, which can increase oxygen consumption and the myocardial Ischemia Reperfusion Injury and cause hypertension.Because of the wide range of abdominal compression in CPR, the result is not ideal. In addition,abdominal compression can lead to potential viscera injury.In our previous study, we independently developed a device of distal abdominal aorta blocking in vitro (successfully applied for the national patent), which can block the blood flow of the distal abdominal aorta and alleviate pelvic fracture bleeding. This suggest that the device can reduce the distribution of effective circulating blood volume in the peripheral retion of the body, and protect cardio-cerebral blood supply. It may be beneficial to the recovery of CA patients. We believe that the means of distal abdominal aorta blocking in vitro could optimize hemodynamic mechanism without increasing ischemia-reperfusion injury and eventually elevate the CPP and the success rate of CPR.Based on previous research, this study was designed to study the effects of distal abdominal aorta blocking in vitro on hemodynamic parameters of normal rabbit and the role of cardiopulmonary cerebral recovery of this method on CA rabbits. In addition, in order to use the device of distal abdominal aorta blocking in vitro for CA patients in future,we conducted an imaging anatomical study to provide an accurate anatomical site for the usage of device.Methods (1)6 New-Zealand rabbits of both genders (2.43±0.26 kg) were used in this study. Anaesthesia was induced by ear vein injection of pentobarbital (1 ml/kg). A endotracheal tube was advanced into the trachea. A 22-gauge polyethylene catheter was advanced from the right carotid artery into the thoracic aorta for the measurement of aortic pressure with the high-sensitivity pressure transducer. Through the left external jugular vein, another 22-gauge polyethylene catheter was advanced into the superior vena cava to measured CVP. After receiving distal abdominal aorta blocking in vitro,the readings of aorta systolic pressure(SBP),aorta diastolic pressure(DBP),mean aorta pressure (MAP) and central venous pressure(CVP) were recorded. (2) rabbits were equally divided into the standrd STD-CPR group or DAAB-CPR group,with 12 rabbits in each group. Cardiac arrest model was made in New-Zealand Rabbits through clamping airtube;CA was maintained for 3 minutes before cardiopulmonary resuscitation. STD-CPR was performed with chest compression,while DAAB-CPR was performed with the chest compressions and distal abdominal aorta blocking. The hemodynamic index were observed during CPR. Time of return of spontaneous circulation(ROSC),the rate of defibrillation succession, and 6-hour survival rates were recorded. The apoptosis in myocardiac cells of resuscitated rabbits were assayed by TUNEL,and the neuron specific enolization enzyme (NSE) levels of serum in different time points was assayed.(3)CT images of 75 patients,41 males and 34 females, were collected. Taking the bellybutton as the the basic point,indexes as follows were measured:1.Location of projection for bellybutton midposition on inferior border of L4;2.The relationship between abdominal aorta termination and bellybutton midposition;3.The relationship among the vertic tracks of abdominal artery,lumbar vertebrae,and inferior vena cava.Results (1)Time for single blockage of distal abdominal aorta in vitro was 15 minutes. The hemodynamic parameters of SBP?DBP?MAP and CVP all tended to increase at instantly,5,10 and 15min after blood flow blockage. Compared with base value, the significant differences were found in SBP after blocking among all time points (P<0.05).DBP and MAP showed significant differences at 5min and 10min time points,compared with pre-block. Compared with baseline,no significant difference in CVP was observed at other sampling time except for the 15min samples. However, when restoring the blood flow, hemodynamic signs of SBP,DBP, MAP, CVP gradually returned to the level of pre-blockage and remained stable. (2)MAP in both STD-CPR and DAAB-CPR group increased gradually during the whole period. MAP of DAAB-CPR group were significantly higher than that of STD-CPR group At 30,60,90,120 and 150 seconds after CPR. The general trend of CPP between the two groups is also gradually recovered after CPR. Compared to STD-CPR group, CPP in DAAB-CPR group were significantly higher at 60,120 and 150 seconds (P<0.05);whereas no significant difference was found at 30 and 90seconds. Compared with STD-CPR group,the time necessary for ROSC in DAAB-CPR group was obviously shortened(P<0.05). Compared with STD-CPR group,the successful recovery rate and 6-hour survival rate in DAAB-CPR group were increased, but no significant difference were found. The apoptosis in myocardiae cells of DAAB-CPR group was lower than those of STD-CPR group. At 3 hours and 6 hours after successful resuscitatin,the NSE levels in DAAB-CPR group were lower than STD-CPR group.(3)The marker for abominal artery terminal blocking in vitro,according to the relationship among the body surface projection of abdominal artery terminal,lumbar vertebrae and navel,roughly overlapped the human median line:1.The abdominal artery terminal located between 40.31 mm above and 32.82 mm below the inferior border of L4;2.The abdominal artery terminal located between 35 mm above and 35 mm below the bellybutton midposition;3.The abdominal artery terminal located in front of spine centrum slightly to the left,and inferior caval vein in front of spine centrum to the right.Conclusions (1)distal abdominal aorta blocking in vitro can elevate MAP, which suggests it is beneficial CPR. (2) In the early recovery of CA in rabbit, distal abdominal aorta blocking in vitro in CPR can elevate MAP,CPP,and it can shorten the time necessary for ROSC and alleviate the apoptosis in myocardiae cells and the cerebral injury.(3)According to imaging applied anatomy basis,navel can be regarded as the marker for abdominal aorta terminal blocking in vitro assisting in standard cardiopulmonary resuscitation. It could improve the hemodynamics indexes,ensure blood supply of the critical organs such as brain and heart,and improve coronary perfusion pressure with high success rate. |
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