The risks after thrombolysis of cerebral infarction are mainly the following 3 points: 1. Intracranial hemorrhage transformation, about 10% of patients with cerebral infarction will have intracranial hemorrhage transformation after thrombolysis, which is divided into symptomatic hemorrhage transformation and asymptomatic hemorrhage transformation. Among them, symptomatic hemorrhage transformation accounts for the majority of patients, who may show impairment of consciousness, headache, nausea, vomiting, aggravation of hemiplegia, seizures and so on. Therefore, for some elderly patients with higher risk of bleeding, the dose of thrombolytic drugs can be reduced appropriately to reduce the risk of hemorrhagic transformation.2. Early neurological deterioration is defined as an increase in NIHSS score >= 4 points from baseline 24 h after thrombolysis. The causes of early neurological deterioration are mainly related to malignant cerebral edema, early stroke recurrence, epilepsy, and hemorrhagic transformation.3. Angiogenic edema, a rare complication after thrombolysis with alteplase, patients may present with hemiangial edema, which then spreads to the contralateral side and even causes acute upper airway obstruction, usually resolving within 24 h. Severe patients may be treated with hormone or tracheotomy.