Effects of acute hypervolemic hemodilution on extravascular lung water during one-lung ventilation:evaluation of accuracy of the transthoracic theermodilution system(PiCCO)<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

郑　晖　苏　跃
司建洛　王金珠

Zheng Hui, Su Yue
SI Jian-luo,et al.

Department of Anesthesiology,Beijing Tuberculosis & Thoracic Tumor Research Institute, Beijing 101149, China

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ABSTRACT

　　Objective To evaluate the effects of different degrees of acute hypervolemic hemodilution (AHHD)on extravascular lung water(EVLW) during one-lung ventilation(OLV)using PiCCO and compare the results with those obtained by gravimetric method. Methods Sixteen healthy adult mongrel dogs weighing12-21kg were randomly divided into 2 groups: OLV group(A, n=8) and two-lung ventilation(TLV)group(B, n=8).The animals were premedicated with intramuscular ketamine 8 mg／kg and anesthetized with thiopental and vecuronium and were mechanically ventilated with 100% O₂ after tracheal intubation. A CVP line was established via external jugular vein and a 4F thermodilution catheter was inserted via femoral artery and connected to atranshoracic thermodilution system (PiCCO, Pulsion). Cold normal saline(＜8℃)5ml was injected rapidly through CVP line 3 times and the mean value was obrained. In OLV group the endotracheal tube was first inserted into the right main bronchus. The left lung was deflated after thoracotomy, then the left main bronchus was clamped and the endobronchial tube was withdrown back to trachea. 15 min after instrumentation, 6% HES was infused at a rate of 80ml／kg／h and Hct was reduced step by step to 25%(H₁), 20%(H₂)and 15%(H₃). MAP, HR, CVP, cardiac output (CO) intrathoracic blood volume (ITBV), global end-diastolic volume(GEDV) and EVLW were measured and recorded after induction of andesthesia(C₁) after OLV was established(C₂), when the chest was closed (C₃)and at H₁,H₂ and H₃. The wet lung weight and dry lung weight were measured and EVLW was calculated.Results CVP increased significantly after OLV was started at C₂ and C₃ and increased further during AHHD at H₁, H₂ and H₃. The wet lung weight and dry lung weight were measured and EVLW was calculated.Results cvp increased significantly after OLV was started at c₂and C₃ and increased further during AHHD at H₁,H₂and H₃. in both groups (p＜0.01). CO, GEDV and ITBV increased significantly at all levels of AHHD(H₁,H₂,H₃)while in TLV group only at H₂andH₃. compared with the baseline value at C1(P＜0.05 or 0.01). Three animals in OLV group showed clinical signs of pulmonary edema at H₂andH₃compared with the baseline The EVLW measured by PiCCO was significantly greater in OLV group than that in TLV group at H₂ and H₃.The EVLW measured by PiCCO was significantly greater than that by gravimetric method but they were closely correlated. Conclusion EVLW is overestimated by PiCCO compared with the calcutated by gravimetric method, but they are closely correlated. ITBV can reflect the changes in preload during OLV, The increase in EVLW induced by AHHD with 6%HES is significantly larger during OLV than that during TLV. Pulmonary edema should be avoided.
　　KEY word: Hemodilution; Respiration, artificial; Extravascular lung water

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　　急性高容量血液稀释（AHHD）技术，操作简便易行且有利于术血液动力学的稳定，同时可以避免异体输血的各种并发症，但在单肺通气（OLV）条件下实施AHHD是否可行尚无定论。本研究拟采用温度稀释法（PICCO系统）观察OLV下AHHD犬血管外肺水（EVLW）的变化，并应用重量分析法验证其结果的标准性，为临床应用提供依据。

一、材料和方法
　　16只康健成年杂种犬，雌雄各半，体重12～21kg，平均身长92cm，实验前禁食12 h。随机分为双肺通道（DLV）组（n=8）及OLV组（n=8），肌肉注射氯胺酮8mg／kg基础麻醉，称重后开放犬外周静脉，注入硫喷妥钠15mg／kg、维库溴铵0.12mg／kg快速诱导，将自制的气管导管（Portex单腔气管导管两根，ID为9mm和8mm，分别截断1/3后对接拈合）插入气管内。间歇正压通气（FiO₂=100%），潮气量（V_T）为12～15ml／kg,频率为6～10次。Min，维持呼气末二氧化碳分压（P_ETCO₂）Z  4.00～5.33kPa(1kPa =7.5mm Hg)。必要时，给予硫喷妥钠和维库溴胺维持麻醉。经颈外静脉置入中心静脉导管15cm，经股动脉置入4F热稀释导管，与PICCO检测仪（Pulsion Medical Systems,的德国）连接。用低于8℃的生理盐水5ml快速推入颈外静脉导管，待得出检测数值后重复以上操作3次，取平均值为检测数据。
　　OLV犬模型的建立　将自制的气管从气管内继续插入并深入右侧支气管，给套囊充气后取右侧卧位，左侧第6、7肋间剖胸，肺萎陷后，游离左侧总支气管后镊夹（操作时间小于5min，以挤压肺）将气管导管退至主气管右顶叶开口之上，套囊充气后右肺通气。用闭胸器将胸腔闭合。
　　草走完成后稳定15min，经犬外周静脉以80ml／kg／h的速率输入6%中分子羟乙基淀粉（贺斯，费森尤斯卡比有限公司，德国），分别将红细胞压积（Hct）降至25%（H₁）、20%（H₂）、15%（H₃）时评。达到H₃水平后立即静脉注射大剂量硫喷妥钠将犬处死，摘取左右侧肺。
　　观察指标　分别在麻醉后即刻（C₁）、开胸OLV后（C₂）、用闭胸器闭合（C₃）、Hct稀释至H_1、H₂、H₃时检测中心静脉压（CVP），应用PICCO检测仪检测心率（HR）、平均动脉压（MAP），心输出量（CO）、胸内血容量（ITBV）、全心舒张末容量（GEDV）、血管外肺水（EVLWG_T）；按文献^[1,2]所示的重量分析法检测血管外肺水含量（EVLW_G）。并观察两组犬肺水肿发生情况。
　　统计学分析　计量资料以均数=标准差（±s）表示，采用SPSS11.0统计软件进行分析，组内比较才哟暖和感双因素方差分析；两种方法所测EVLW结果行回归分析，P<0.05为差异有显著性。

二、结　果
　　二组犬一般情况无显著行差异（P>0.05）。二组在H_1-3时低于基础值，二组间补液量差异无显著性（P<0.01）见表1。
　　与C₁比较，DLV组CVP、CO 、GEDV、ITBV在H_1-3、EVLW在H_2-3时升高（P<0.05或0.01）OLV组各时点差异无显著性（P>0.05）。与C₂比较OLV组在C₃、H_1-3时CVP、在H_1-3时CO、GEDV、ITBV、EVLW升高（p<0.05或0.01）；DLV组各时点差异无显著性（P>0.05）。OLV组在H_2-3时EVLW高于DLV组（P<0.05）。见表2
　　相关分析显示两种方法所得结果显著相关，回归方程为：DLV组EVLW_G=0.74EVLW_T+23.69（r²=0.60,P<0.05）；OLV组：EVLW_G=0.68 EVLW_T+28.53（r²=0.53,P<0.05）。
　　当血液稀释至H₂时两组都未发生肺水肿，H₃时OLV组有3只犬出现临床肺水肿表现，主要表现为气道压增加，大量粉红色泡沫谈由气管导管涌出。而DLV组未出现上述症状。

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