➤CDC(美国疾病控制与预防中心)推荐,在注射疫苗或药物之前,“回血操作”是不必要的,因为在推荐的注射部位没有大的血管,而且“回血操作”的过程对小儿可能更加痛苦。(1) ➤Over a 4-year period 36,000 allergy injections were administered using aspiration for blood return before administration with no blo...