试述剩余碱（BE）的概念及其变化的临床意义。
既能治肺胃出血，又能消散痈肿、生肌敛疮的药物是（） ["藕节","棕榈炭","仙鹤草","白及","血余炭"]
生用能活血化瘀止血、炒用能凉血止血的药物是（） ["三七","蒲黄","花蕊石","茜草","降香"]
既能凉血止血，又能散瘀消痈，善治尿血的药物是（） ["槐花","小蓟","侧柏叶","大蓟","苎麻根"]
既能凉血止血，又能散瘀消痈，还可利胆退黄的药物是（） ["槐花","地榆","侧柏叶","大蓟","白茅根"]
试述缓冲碱（BB）的概念及其变化的临床意义。
