Out-of-hospital cardiopulmonary arrest patients who remain unconscious after resuscitation still have a poor prognosis[4]. The poor neurologic outcome is related to the ‘reperfusion injury’ of brain cells after the return of spontaneous circulation[5]. It has been reported that cardiopulmonary resuscitation (CPR) for patients with out-of-hospital cardiac arrest using CPB, coronary artery reperfusion therapy, and mild hypothermia has achieved good results[6–8]. In this case, we timely used various circulatory auxiliary devices such as VA-ECMO, and IABP for effective resuscitation and combined with CRRT for renal replacement therapy. At the same time, according to our experience, the protection of the nervous system in circulatory assistance and later rehabilitation treatment is extremely vital.
As a protective measure, the lower pacemaker will emit one or a series of excitations that excite the atria or ventricles when the higher pacemaker is diseased or inhibited, resulting in arrest or significantly reduced frequency. Ventricular escape rhythm and ventricular fibrillation are more common in patients with severe heart disease, such as acute myocardial infarction[9], myocarditis[10], electrolyte disturbance[11], and low-temperature anesthesia. Ventricular escape rhythm without atrial excitement is often an arrhythmia near the end of life, which can lead to rapid death if delayed in treatment or not treated. In this case, the hypothermia inhibited the function of the sinoatrial node, resulting in ventricular escape rhythm, repeated ventricular fibrillation, and hemodynamic collapse. For such patients, our center advocates the establishment of extracorporeal life support as soon as possible to replace the cardiopulmonary function, to maintain a relatively stable circulation to ensure the blood supply of organs throughout the body.
Hypothermia can be divided into four stages according to clinical symptoms and core temperature. Severe hypothermia will lead to functional failure of cardiovascular, respiratory, nervous, and other systems, and even lead to death. The treatment strategy is to restore body temperature and organ functions, and for rewarming, our center prefers slow rewarming to prevent left ventricular diastolic dysfunction and ischemia-reperfusion injury[12, 13]. In addition, ECLS has been recommended as the gold standard for the treatment of severe hypothermia[3].
ECMO is a development of extracorporeal circulation, which began to be used in the 1970s as temporary cardiopulmonary support for critically ill patients[14]. The generalized ECMO is often used to describe VV or VA ECMO. VV ECMO is indicated for patients who require only respiratory function support, such as severe acute respiratory distress syndrome (ARDS). VA ECMO is suitable for severe heart disease, refractory ventricular fibrillation, or fulminant myocarditis. The establishment of VA ECMO requires the implantation of two percutaneous vascular catheters, including an arterial catheter and an intravenous catheter with the tip of the venous catheter located at the inferior vena cava and atrial junction and the tip of the arterial catheter located at the common iliac artery. The blood flows into the extracorporeal oxygenator through the venous catheter and into the systemic circulation through the arterial catheter to supply blood and oxygen to the whole body. When the patient's heart resumes beating, IABP is used to reduce the patient's cardiac afterload and increase coronary blood flow to improve myocardial oxygen supply. IABP is the implantation of an inflatable balloon in the descending aorta. When the aortic valve opens during the systolic period, the balloon deflates to form negative pressure in the aorta, thus reducing systolic blood pressure and cardiac afterload. The balloon is inflated when the aortic valve closes during the diastolic period, thereby increasing diastolic blood pressure to increase coronary blood flow[15].
Hypothermia-induced ischemia and hypoxia can cause liver and kidney insufficiency, hence organ replacement therapy such as CRRT is particularly important[16]. At the same time, considering the protective effects of low temperatures on brain metabolism, for patients with cardiogenic shock receiving ECMO support, we routinely use ice caps for head cooling to protect brain function. Strict temperature control in therapeutic hypothermia is very helpful to the patient's nervous system [17]. In addition, nutritional support and rehabilitation therapy play an integral role in the whole treatment process. Therefore, it is recommended that such patients be managed by an experienced cardiac team that can evaluate the patient's condition in multiple aspects.