Mahuang Fuzi Xixin Decoction recorded in Treatise on Febrile Diseases by Zhang Zhongjing in the Han Dynasty have been widely used in treating Yang deficiency and exogenous wind-cold syndrome by traditional Chinese medicine physicians for thousands of years. The indications of Mahuang Fuzi Xixin Decoction include bradyarrhythmia,sinus bradycardia,sick sinus node syndrome,senile exogenous,asthmatic cold,rhinitis,bronchial asthma,optic neuritis,optic atrophy,sudden blindness,sudden onset of cough,laryngeal obstruction,migraine,joint pain,low back pain,insomnia,shock,heart failure,renal failure,accompanied by fever or nosocomial infection,and hyperpyrexia after tracheotomy; dark complexion,chills,cold limbs,listlessness,fatigue,insomnia,lack of thirst,liking hot drinks,slightly swollen limbs or whole body,pale fat tongue,greasy fur,and deep pulse. Mahuang Fuzi Xixin Decoction is a potential drug for Shaoyin disease complicated with fever and pain. Tracheal intubation is an artificial ephedrine syndrome. It is necessary to distinguish Yin and Yang syndrome in treating hyperpyrexia after tracheotomy. However,it belongs to Yin syndrome,which could be treated by Mahuang Fuzi Xixin Decoction. Mahuang Fuzi Xixin Decoction is effective in the treatment of sick sinus syndrome,second degree atrioventricular block and third degree atrioventricular block. It can significantly alleviate symptoms,improve heart rate,and heart rhythm in a short period of time. However,after one year of drug withdrawal,the diseases may recur,indicating that Mahuang Fuzi Xixin Decoction may not improve the long-term prognosis of slow arrhythmia. Mahuang Fuzi Xixin Decoction is often used for fever or nosocomial infection in critical care medicine. In the treatment of critical care medicine complicated with high fever,Mahuang Fuzi Xixin Decoction is often taken continuously by stomach tube.