Anemia-induced increase in the bleeding time: implications for treatment of nonsurgical blood loss

BACKGROUND: Preoperative bleeding time (BT) does not correlate with postoperative bleeding in patients subjected to surgical procedures. A significant positive correlation has been reported between the BT 2 hours after cardiopulmonary bypass surgery and the nonsurgical blood loss during the first 4 hours after bypass surgery. This study was done to investigate the effect of Hct and platelet count on the BT measurement in normal, healthy men and women. STUDY DESIGN AND METHODS: To assess the relative effect of RBCs and platelets on the BT, 22 healthy male and 7 healthy female volunteers were subjected to the removal of 2 units of RBCs (360 mL), followed by the return of the platelet-rich plasma (PRP) from both units and the infusion of 1000 mL of 0.9-percent NaCl. Four of the men and all seven women received their RBCs 1 hour after their removal. Shed blood levels of thromboxane B(2) (TXB(2)), 6-keto prostaglandin F(1 alpha), and peripheral venous Hct were measured. BTs were measured in 15 men and 13 women before and after a plateletpheresis procedure to collect 3.6 x 10(11) platelets per unit. RESULTS: The 2-unit RBC apheresis procedure produced a 60-percent increase in the BT associated with a 15-percent reduction in the peripheral venous Hct and a 9-percent reduction in the platelet count. The plateletpheresis procedure produced a 32-percent decrease in the platelet count, no change in peripheral venous Hct, and no change in the BT. After the removal of 2 units of RBCs, the shed blood TXB(2) level decreased significantly. Reinfusion of 2 units of RBCs restored the BT and restored the TXB(2) level to the baseline levels. CONCLUSION: The acute reduction in Hct produced a reversible platelet dysfunction manifested by an increase in BT and a decrease in the shed blood TXB(2) level at the template BT site. Return of the RBCs restored both the BT and the shed blood TXB(2) level to normal. The platelet dysfunction observed with the reduction in Hct was due in part to a reduction in shed blood TXB(2) and other, unknown mechanisms.     

10kg以下婴幼儿先天性心脏病合并肺动脉高压的外科治疗

目的探讨低体重婴幼儿先天性心脏病合并肺动脉高压的手术前准备、手术方法、体外循环管理和术后处理的注意事项,以减少婴幼儿先心病术后并发症的发生。方法回顾性分析22例10kg以下先心病合并肺动脉高压（pH）婴幼儿在体外循环（CPB）下行心内直视手术的围手术期处理临床资料。结果22例患儿年龄11～26月,平均（19.4±8.5）月;体重5.5～10.0kg,平均（7.6±2.3）kg;室间隔缺损（VSD）20例,其中合并房间隔缺损（ASD）2例,ASD合并动脉导管未闭（PDA）2例;肺动脉高压轻度8例,中度11例,重度3例。所有患儿均手术一期矫治,彻底纠正心内畸形,CPB转流时间32～110min,平均58min;主动脉阻断时间11～30min,平均22min;心脏全部自动复跳,均顺利脱机;l例因术后低心排综合征死亡,病死率4.5%,余均康复出院,无并发症发生。结论婴幼儿先心病合并肺动脉高压者应充分做好手术前准备工作,手术操作熟练,重视体外循环管理、围手术期处理,尤其是新技术、新药的合理应用,都有助于提高婴幼儿心脏手术的成功率,减少术后并发症的发生。     

小儿体外循环心脏手术对甲状腺激素代谢的影响

目的观察低体重婴幼儿体外循环心脏手术前后甲状腺激素的变化,探讨其对甲状腺激素代谢的影响。方法选择21例10kg以下婴幼儿行体外循环心脏手术。分别于体外循环前、体外循环结束时、术后第一天、第二天和第四天采取其静脉血样,观察其血清的三碘甲状腺原氨酸（T3）、甲状腺素（T4）和促甲状腺激素（TsH）浓度变化。结果T3浓度在体外循环后明显下降（P〈0．05）,术后第二天降至最低,至术后第四天仍未恢复至体外循环前水平;T4在体外循环结束时及术后第一天轻度下降,第二天明显下降（P〈0．05）,第四天恢复至体外循环前水平;TSH于体外循环时轻度升高。术后第一天和第二天明显下降（P〈0．05）,第四天升高超过体外循环前水平。结论10kg以下婴幼儿在体外循环心脏手术囤术期不同时期可以发生甲状腺功能正常的病态综合征,表现为T3、T4和TSH的下降,这表明体外循环心脏手术对低体重婴幼儿甲状腺激素代谢有重要影响,因此加强围术期患儿甲状腺激素的监测及术后尽早补充甲状腺激素对患儿恢复有重要作用。