Abstract: Objective: To explore the therapeutic effect of ulinastatin(UTI) in patients with acute severe carbon monoxide poisoning(ASCOP) complicated with myocardial injury requiring ventilator assisted respiration.Methods: Prospective research method was adopted, the 96 patients with ASCOP were randomly divided into UTI group and control group.Patients in the control group were routinely given basic treatments such as oxygen inhalation, intermittent ventilator pure oxygen inhalation, cranial pressure reduction by dehydration, free radical scavenging and cardiac brain cell nutrition.The UTI group was given ulinastatin intravenous infusion(100, 000 U intravenous infusion,q8 h) on the basis of the control group.Patients in both groups received continuous treatment for 7 days.The coma time at admission and after treatment, ICU stay, blood pressure, smoking and other data were collected.Calculate the Glasgow score(GCS score).Blood routine was collected before and after treatment, and the ratio of neutrophils to lymphocytes, namely NLRwas calculated. IL-6, troponin I(cTnI), creatine phosphocreatine isoenzyme(CK-MB), and ischemia modified albumin(IMA) were collected, as well. ECG examination was performed and the incidence of ECG abnormalities was calculated. Changes in cardiac function(left ventricular ejection fraction, left ventricular end-diastolic diameter, left ventricular short-axis shortening) were compared between the two groups before and after treatment. T-test and chi-square test were used for statistical analysis.Results: Before treatment, there was no significant difference in WBC count, NLR value and IL-6 between the two groups(P> 0.05).After ulinastatin treatment for one week, the levels of inflammatory indexes in the UTI group were significantly lower than those in the control group(P< 0.05).Before treatment, there was no significant difference in the levels of serum myocardial ischemia markers, IMA and CK-MB, between the two groups(P>0.05); after 1 week of ulinastatin treatment, the level of UTI group was significantly lower than that of control group(P<0.05).Before treatment, the incidence of abnormal ECG in both groups was 68.75%, and after treatment, the incidence of abnormal ECG in UTI group was significantly reduced(P<0.05). After treatment, the duration of coma and ICU stay in ulinastatin group was significantly shortened(P<0.05). After treatment, cardiac function was improved in both groups, but was significantly improved in UTI group(P<0.05).Conclusion: When ASCOP complicated with myocardial injury, especially when hyperbaric oxygen therapy cannot be performed, on the basis of intermittent pure oxygen inhalation, the application of UTI can antagonize the inflammatory response, improve myocardial tissue damage, and have a certain protective effect on myocardial injury after ASCOP.