结果   共纳入32篇文献，共计1101例病人（试验组/对照组 550/551）。纳入文献的方法学质量普遍偏低。对纳入文献进行整体分析时显示：AHH可以减少手术患者术中的输血量，输血率和理论出血量，但对总出血量无影响。输血量、理论出血量和总出血量的加权均数差（Weighted mean difference, WMD）分别为-279.23ml[95%可信区间（Confidence interval，CI）为-350.51～207.95ml]、-207.39ml（95%CI为-227.29～-187.50ml）、-73.65ml（95%CI为-154.44～7.15ml），输血率的相对危险度（Relative risk, RR）为0.43（95%CI为0.35～0.53），其中输血量和总出血量各研究间存在异质性（P<0.00001），按手术种类、稀释程度、出血量大小进行亚组分析时与整体分析时结果基本一致。
       结论   AHH可以减少术中输血量、输血率和理论出血量，但此结论有待更多设计严谨的大样本随机对照试验加以验证。
       关键词： 急性高容量血液稀释；血液保护；Meta分析

       Blood Conservation of Acute Hypervolemic Hemodilution: a Meta-analysis
       Xu-ze LI, Zhen-ming DONG
       Department of Anesthesia, Second Hospital, Hebei Medical University, Shijiazhuang 050000, China.
       ABSTRACT
       Objective To assess the efficacy of blood conservation of acute hypervolemic hemodilution.
       Methods  

       Medline, Ovid Medline, Journals@Ovid Full Text , Cochrane Central Register of Controlled Trials, Cochrane Library, Chinese Biomedical Database, Chinese Conference data were searched up to February 2007, the studies as references of these articles were also searched. Randomized controlled trials comparing AHH with a control group, conducted during operation performed on adults were included. Two researcher collected data independentely, and then, methodological quality of trials was assessed in terms of generation of allocation sequence, blinding, and drop-outs. The data were quantified by Meta-analysis.
       Results  

       32 RCTs meet all eligibility criteria, a total of 1101 patients included (550 in the treatment group and 551 in the control group). The methodological quality was generally low. When all trials were pooled, AHH reduced the volume and rate of allogenic blood transfusion, and calculated volume of blood loss     

in the Perioperative period, but had no effect on total volume of blood loss. The weighted mean differences (WMD) of the volume of allogenic blood transfusion, calculated blood loss and total blood loss were -279.23ml[95%confidence interval(95%CI) was -350.51～207.95ml] , -207.39ml（95%CI was -227.29～-187.50ml）and -73.65ml（95%CI为-154.44～7.15ml）. The relative risk (RR) of the rate of allogenic blood transfusion was 0.43 ( 95% CI was 0.35~0.53). Among the studies of the volume of allogenic blood transfusion and total blood loss there was a significant heterogencity. Further subgroup analysis based on the type of surgical procedure, degree of hemodilution and volume blood loss showed that the results were almost the same.
       Conclusion

       AHH could reduce the calculated volume of blood loss, the volume and rate allogenic blood transfusion. But further studies which are well designed are needed.
       Key words: Acute hypervolemic hemodilution； Blood conservation； Meta-analysis 
   

       异体输血存在诸多方面的缺点和风险，如可导致输血相关疾病的传播、费用昂贵，以及血液制品长期保存困难等[1]。因此现代医学倡导在围术期节约用血并采用血液保护技术以减少异体输血。现在临床上最常用的血液保护技术分两大类：控制性降压和急性血液稀释(Acute hemodilution, AH)。AH又包括急性等容量血液稀释（Acute normovolemic hemodilution, ANH）和急性高容量血液稀释（AHH）。三者之中关于控制性降压的研究进行的最深入，方法学也最全面，其有效性已得到认可，并被普遍接受[2]。而作为美国卫生部（NIH）推荐的自体输血方法之一的ANH[3]，Segal和黎玉辉曾分别在2004年和2006年对其血液保护作用做过系统评价[4,5]，证实确实可以有效的减少术中的异体输血率与输血量，其有效性也已被广泛认可。只有AHH的有效性还未得到充分证明。
       ANH虽然有效，但其操作复杂费时，需预先抽血，可能导致污染，还涉及存放问题，费用相对比较昂贵，实施起来有一定的局限性。近几年来部分学者提出AHH在一定程度上可以替代ANH[6,7 ]，其实施过程简单，费用较低，且不存在血液污染的问题，因而得到了广泛的关注。
       AHH技术是在麻醉后通过深麻醉使血管容量得到一定的扩张，同时快速补充相当于20％自身血容量的胶体液或晶体液，使血液稀释，减少出血时红细胞的丢失量。AHH不同于麻醉前简单的补充血容量，它在术中也保持血液的高容状态，术中出血带走的红细胞减少，同时还可以增强病人对失血的耐受能力，达到减少异