Standardizing a resuscitation model in animals with a comparable cardiopulmonary physiology to humans helps in the study and understanding of novel therapy options to ultimately improve patient outcomes. For proper application of the model and adequate interpretations of the results, expertise in emergency medicine and the intensive care of critically ill patients is highly recommended. The main advantage of this procedure is the improved sensational applicability of positive results and in an otherwise extra challenging experimental setting.
Initial demonstrating the experimental setup can help significantly since the electrode and compression pad placement are crucial for successful execution and are often described solely through text alone. This protocol provides deeper insights into resuscitation mechanism for critical and intensive care providers in pre-hospital and clinical settings. After placement of the trans-pulmonal thermodilution catheter into the sedated, experimental pig, place one defibrillator patch electrode anterior on the torso and one posterior electrode on the central left hemithorax.
Connect the electrodes to a defibrillator to establish ECG and immobilize the pig inside a vacuum mattress. Deflate the mattress to prevent unwanted movement during CPR and secure the limbs. Place a chest compression device around the chest and under the vacuum mattress according to the manufacturer's recommendations and adjust the pressure pad to the lower third of the sternum in median position.
For optimal positioning of the chest compression device, the animal may have to be shifted sideway within the deflated mattress. When the device is in place, power on the device and lower the pressure pad to the skin. Press pause to prepare the device for chest compressions and insert a fibrillation-pacing catheter inside the left femoral vein through the IV sheath.
Inflate the catheter cuff with one to two milliliters of air and slowly push the inflated cuff about 50 centimeters until it is positioned next to the right atrium. Connect the catheter electrodes to an adequate oscilloscope function generator and adjust the fibrillation parameters to the appropriate experimental values. Next turn on the generator while monitoring the ECG changes, moving the catheter slowly forward until arrhythmias can be detected in the ECG.
Carefully vary the catheter position until ventricular fibrillation can be detected. Once ventricular fibrillation has been confirmed, turn off the generator and deflate and remove the fibrillation catheter. Then press play on the compression device to start mechanical chest compressions.
To interrupt the chest compressions, press the pause button on the compression device. Analyze the ECG patterns. If ventricular fibrillation persists, enter the manual mode in the defibrillator menu and adjust the energy to 200 joules by phasic.
Press the load button and wait until acoustic signal turns on to indicate a prepared shock value before initiating the electric shock. In the case of the return of spontaneous circulation, stop the chest compressions, continue ventilation, and apply monitoring as extensively and for as long as needed. Pacing catheter induced cardiac arrest can be assumed if the ECG readings show ventricular fibrillation and no cardiac output or pressure variations are measured by the arterial line.
Once the chest compressions have been started, sufficient cardiac output generation is indicated by a mean arterial pressure of 30 to 50 milliliters of mercury and, if adhering to resuscitation guidelines, the administration of one milligram of adrenaline result in a substantial rise in blood pressure within one minute. The return of spontaneous circulation is confirmed by a dramatic increase in the expiratory carbon dioxide measurements and an organized heart rhythm in the ECG in the respective cardiac output as observed by arterial measurement. Hypercapnia and a decreased Horovitz index are commonly observed after the return of spontaneous circulation and a reestablishment of controlled mechanical ventilation leads to recompensation and stable respiratory conditions.
Misplacing or dislodging the chest compression device during the experiment jeopardizes the results. Therefore care should be taken to avoid repositioning. With this procedure, a standardized evaluation of the cardiac output and the ventilation-perfusion ratio during resuscitation can be performed to characterize extensively cardiopulmonary effects.
Standardized resuscitation models have to identify novel ventilation techniques during CPR, potentially helping to improve patient outcome. When attempting protocols that use defibrillation and oscilloscopes, adequate expertise and caution are paramount to preventing life threatening situations and injury.
