Extracorporeal cardiopulmonary resuscitation (ECPR) constitutes a pivotal emergency intervention for cardiac arrest (CA) patients. However, current eligibility criteria and prognostic assessment metrics remain substantially limited, relying predominantly on clinical symptoms and physical signs while lacking objective biomarker data. Integrating reproducible, highly sensitive, and specific proteinaceous and metabolic indicators with ultrastructural platelet alterations may hold significant implications for both ECPR administration and prognostication in CA. Therefore, the purpose of this study is to identify the plasma proteomic and metabolomic characteristics of patients with refractory cardiac arrest before and after ECPR treatment, as well as the characteristics of platelet morphological and structural changes, to search for potential specific markers that can predict CA patients who may benefit from ECPR so as to optimize treatment selection.

Inclusion Criteria:

1. Age between 18 and 70 years old (the age limit can be relaxed if the patient has good organ function and a good neurological prognosis after evaluation).
2. The cardiac arrest is witnessed, and bystanders perform traditional cardiopulmonary resuscitation (CPR), and the time interval from the occurrence of cardiac arrest to the start of traditional CPR is no more than 5 minutes.
3. The causes of cardiac arrest are reversible, such as cardiogenic, pulmonary embolism, severe hypothermia, drug poisoning, trauma, acute respiratory distress syndrome, etc.
4. After 20 minutes of traditional CPR, there is no restoration of spontaneous circulation or hemodynamic instability, or the restoration of spontaneous circulation occurs, but the spontaneous heart rhythm cannot be maintained.
5. The informed consent has been signed.

Exclusion Criteria:

1. Infectious diseases, such as hepatitis B, hepatitis C, AIDS, syphilis, etc.
2. Hematological diseases, such as hematological malignancies, aplastic anemia, idiopathic thrombocytopenic purpura (ITP), etc.
3. Malignant tumors in other systems except the hematological system.
4. Patients who have received massive plasma or platelet transfusions during hospitalization or recently.

All adult patients receiving ECPR will be included. The decision to perform an ECPR is made by the local protocol and clinical judgment of the attending physician.