Local anesthesia has certain risks, but local anesthesia is already a mature medical technology, the probability of risk is very low, patients do not need to worry too much. There are some patients who belong to extreme allergic body, allergy to anesthetics may happen, usually doctors will ask the patients and do the corresponding test before performing surgical anesthesia, this situation can be avoided. During local anesthesia, the anesthetic drugs may enter the blood vessels, leading to a sudden rise in the concentration of anesthetic drugs in the blood, resulting in anesthetic poisoning of the patient. Light manifestations of dizziness and nausea, serious may appear coma, respiratory difficulties, etc., as long as the timely rescue, generally does not cause life-threatening. In the injection of local anesthetic before the puncture, puncture process may appear hematoma, infection, etc., serious will lead to limb paralysis. There are risks associated with any medical technique, and local anesthesia is a relatively mature and well-established technique. Doctors will conduct a variety of pre-operative tests to assess whether a patient is suitable for local anesthesia. Local anesthetics usually take about one to four hours to take effect, and the drug will be metabolized, and will not cause any harm to human health.