| Cardiac arrest(CA) is a very dangerous but common illness in clinic. With thedevelopment and popularization of cardiopulmonary resuscitation(CPR) after cardiac arrest,the rate of restoration of spontaneous circulation(ROSC) has been significantly improved,but unfortunately, the mortality after the successful recovery remains high, which may havea direct relationship with post–cardiac arrest syndrome(PCAS). Therefore, in recent years,studies on PCAS formation mechanism and the related control measures have become oneof hotspots in clinical research, yet also a difficult problem for cardiopulmonary cerebralresuscitation field. For now, the exact pathogenesis of PCAS is still not very clear, it maybe associated with ischemia reperfusion injury, inflammatory reaction and apoptosis.Because of the particularity of cardiac arrest clinical process, most of the research stillfocused on the stage of animal model, and because of the difficulty of PCAS model, thereis lack of good molding method to promote. If we can find the way to establish PCASanimal model with practical application value simply and effectively, it will be very helpfulfor the researches on cardiac arrest syndrome prevention and cure. In this study, we usedtwo different ways, clipping trachea or transthoracic electrical stimulation, to cause cardiacarrest, by comparing ROSC rate, survival rate at different time, MODS rate, and so on,tried to explore the appropriate solution for PCAS model, and to provide the experimentalmodel for the further research on the PCAS.Objective: By comparing the advantages and disadvantages between clipping tracheaand transthoracic electrical stimulation in the construction of PCAS model, to provide theexperimental basis for the further researches of the PCAS pathogenesis, prevention andcontrol measures. Methods: In this study, we chose rabbits as experimental animal, and they wererandomly divided into control group (sham operation group), asphyxia group, and electricalstimulation group. The control group rabbits had5rabbits, and asphyxia group, electricalstimulation group with14cases in each, and then the asphyxia group and electricalstimulation group was divided into24h subgroup and48h subgroup depending on thedifferent execution time. Rabbits in24h subgroup were only for making organ specimensafter ROSC24h, did not participate in taking blood specimens or statistics count correlatedwith the experiment.All rabbits were fasted before operation, but the water, and all werelabeled and weighed after into the operation room. First, we used3%sodium pentobarbitalsolution for anesthesia by slowly injecting through rabbit ear vein, where we placed a venousindwelling needle for setting up the transfusion channel. And then, the anesthetized rabbitswere fixed on the operation table, connecting with the ECG monitor to recordelectrocardiogram. Exposing the trachea, carried out tracheotomy and intubated the rabbits.Separating the common carotid artery, intubated the artery, and connected it with thepressure transducer in order to record of arterial blood pressure and mean arterial pressure.The incandescent lamp as a heat source was used to maintain the body temperature of theanimal.15minutes after the operation, body temperature, pulse, mean arterial pressure,respiratory rate and ECG status were recorded as parameters to determine physiologicalbaseline of animal.Second step is to cause cardiac arrest. Asphyxia group rabbits wereclipped the trachea tube at the end of expiratory, to induce cardiac arrest. Recorded the timefrom the beginning of clamping tracheal tube to the moment when indexes meeting thecriterion of cardiac arrest. In electrical stimulation group, the rabbit`s thorax was stick intotwo pieces of acupuncture needle as the stimulating electrode. The right needle was put atthe right side of manubrial, the other one was at the left side of ensisternum. We usedalternating current(5s,30V,50Hz) to stimulate the animal, and gradually adjusted the voltage of current until causing cardiac arrest, also recorded the time from the beginning ofelectrical stimulation to CA. Except cardiac arrest and cardiopulmonary resuscitation, thedisposal in control group was same to the asphyxia group and the electrical stimulationgroup.3min after CA, We began CPR. During this time, removed of light source, fixed themachine of external chest compression, connected the ventilator. And if during this time,animal ECG recovered to sinus rhythm or supraventricular rhythm, then the failure ofinducing CA would be judged.When3min was up, we began CRP immediately, and startmechanical ventilation at the same time, and also injected adrenaline, atropine, dopamine,dobutamine, lidocaine,5%sodium bicarbonate and other emergency medicine. If the ECGwas ventricular fibrillation defibrillation, we would give cardioversion(20J, Single-phaseDC), and if it did not work, we would continue to resuscitation, and after2min, trycardioversion again. Recorded the time since the start of the recovery to the restoration ofspontaneous circulation(ROSC). If the animal failed to ROSC through15minutes rescue, itwas considered as recovery failure. If it was back to spontaneous circulation, continue tomonitor ECG and blood pressure, try to make the animal, as much as possible, survived formore than48hours. For the rabbits with a relatively stable blood pressure and respirationcan be gradually stopped ventilation, and extubation. Rabbits after ROSC not eatting oreatting poor can be given5%glucose in normal saline. And depending on the condition offeeding or watering, we adjusted intravenous transfusion. Observed the rabbits in48hsubgroup after resuscitation, and recorded survival time and survival rate. The end ofobservation is48hours, at that time, if the animal was still alive, it would be executed byoverdose of anesthesia. Observing the changes of vital signs and comparing them before andafter CA, to determine whether they meet the criteria for the diagnosis of SIRS. Observedand compared the changes of body temperature, heart rate, mean arterial pressure,respiratory rate and other basic vital signs, before and after rabbits recovery, compared ECG type and composition ratio with CA occuring, calculated the success rate of induced CA, theincidence of SIRS and the incidence of PCAS. Rabbits from two48h subgroups, not24hsubgroups, were detected arterial blood oxygen partial pressure, lactic acid, white blood cellcount, blood glucose, creatinine, alanine aminotransferase, creatine kinase isoenzyme,respectively at the time of before resuscitation and12hours,24hours,48hours afterresuscitation. The control group was detected the same indicators before anesthesia and afterrecovery. Took the heart, lung, liver, kidney and intestine specimens from rabbits in both24hsubgroup and48h subgroup, if they were still alive at ROSC24h or ROSC48h, andobserved the pathological changes of the organs under light microscope.Results:1. During the process of making experimental model, the time of inducing CAwas with significant difference comparing with electrical stimulation group (P＜0.01). But,the success rate of inducing CA, in both asphyxia group and electrical stimulation group hadno significant difference(P＞0.05).2. Although there was significant difference between twogroups on ECG distribution recorded during CA, we found the time of ROSC betweenasphyxia group and electrical stimulation group had no significant difference(P＞0.05), andalso, the rates of ROSC in two group were both100%. And at each time period, there isslight difference in survival rate between two groups, but no statistical difference.3. In spiteof before or after resuscitation, vital signs and the biochemical indexes has no obviousdifference between two groups. But a great significant difference was observed whencomparing the indexes after ROSC with before CA in each group(P＜0.05). By surveyingthe organs from the rabbits living more than24h and48h after ROSC, all of them showedthe pathologic changes, but electrical stimulation group was slighter than asphyxia group.4.Rabbits from both asphyxia group and electrical stimulation group had SIRS(the rate ofSIRS in two group100%), but not the ones from control group. And, there were5rabbitsalive more than48hours after ROSC in asphyxia group, and6rabbits in electrical stimulation group. All of them met the criteria of PCAS, so the rate of making PCAS rabbitmodel successfully was71.43%,85.71%respectively in two groups, and no statisticaldifferences between two groups(P＞0.05).Conclusion: Either asphyxia or electric stimulation method to make the animal model ofPCAS has its own characteristics, but the pathological injury of organs in electric stimulationgroup was slighter than asphyxia group.But there was no significant difference between twomethods in the success rate of modeling PCAS. And both method only required simpleequipment, the operation was alos easy to master. Either aspyxia or electric stimulationmethod has certain feasibility. |
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