Clopidogrel (Plavix) is a thienopyridine drug that prevents platelet aggregation by inhibiting ADP receptor-mediated platelet activation. This results in irreversible blockade that extends for the life of the platelet (which is typically 7–9 days). In the setting of elective surgery, the discontinuation of clopidogrel for 7 days prior to the day of surgery is generally recommended because the degree of inhibition can only be overcome by platelet transfusion or by the generation of new platelets. If surgery is performed without holding medication, bleeding risk is increased and the potential for higher transfusion requirements should be discussed and prepared for. Neuraxial anesthesia in a patient on clopidogrel carries the risk of epidural hematoma. Therefore, if a spinal injection is to be performed on a patient prior to 7 days of discontinuation of the drug.

氯吡格雷（波立维）是一种噻吩吡啶类药物，通过抑制ADP受体介导的血小板活化来抑制血小板聚集，将导致贯穿整个血小板生命周期内（大约7~9天）不可逆的阻断。对择期手术而言，目前的专家共识推荐，氯吡格雷在术前至少需停用7天，因为此类药物对血小板的抑制作用只能通过输入新鲜血小板或等待新生血小板才能逆转拮抗。如果术前未停药，术中出血风险将增大，可能导致围术期输血量增加，需提前做出准备。对使用氯吡格雷的患者进行椎管内麻醉可能增加其硬膜外血肿的风险。因此，对拟行腰麻的患者一定要确保其在麻醉操作前已停药至少7天。

Therefore, if a spinal injection is to be performed on a patient prior to 7 days of discontinuation of the drug.

因此，对拟行腰麻的患者一定要确保其在麻醉操作前已停药至少7天。

这句话的主句在哪里？谢谢