This study is a single-center, prospective, observational study. According to the sample size formula, an estimated 40 cases should be collected, all of whom are from the emergency intensive care unit. After successful cardiopulmonary resuscitation, the enrolled patients will be transferred to the emergency intensive care unit for further standardized target temperature management (TTM). They will be divided into 33 ° C hypothermia group and 36 ° C hypothermia group according to the patient's core body temperature. The baseline data of the patients will be collected at the beginning. After admission to the hospital, they were fasted within 24 hours to reach the target temperature, and then 20kcal/kg/d parenteral nutrition will be given. At selected time points (T0: the initial time point before TTM; T1: the core temperature was reduced to 33 ° C or 36 ° C; T2-T4: 33 ° C or 36 ° C was maintained for 24h, 48h, 72h; T5: the end of rewarming; Tend: the last REE measurement before discharge or death) , various observation indicators will be collected, including resting energy expenditure (REE), glucose oxidation rate, fat oxidation rate, protein oxidation rate, and metabolism of three major nutrients Proportion. Neurological outcomes were followed up 28 days after onset according to the Cerebral Performance Categories (CPC) score.