急性等容血液稀释对犬单肺通气期间肺分流与氧合的影响

目的 观察犬单肺通气期间,不同程度急性等容血液稀释对肺分流和氧供、氧耗等的影响。方法 12只健康杂种犬,基础麻醉后插入双腔气管导管,股动、静脉置管。稳定30分钟（HD0）后,以血定安等速置换全血,分别达到轻度（HD1）、中度（HD2）、重度（HD3）和极重度（HD4）血液稀释四个阶段。每阶段均分为双肺通气（TLV）和单肺通气（ OLV）,分别于各阶段TLV、OLV15分钟后测量分流（Qs/Qt)及氧供（DO2）、氧耗（VO2）等各指标变化。结果 随着HD程度的加深,平均动脉压、心输出量、肺血管阻力（PVR）、平均肺动脉压（MPAP）、氧分压、DO2等趋于降低,氧摄取率（EPO2）、血乳酸、Qs/Qt趋于增加,到HD3、HD4时已出现DO2－VO2依赖性降低及无氧酵解征象。与TLV时相比,OLV期间HD0、HD1及HD2组PVR、MPAP增高明显（P＜0．01）。而HD3、H4D4组变化不大（P＞0．05） ;OLV时QS／Qt增加更为明显,HD2、HD3及HD4组分别较基值增加74％、164％及177％（P＜0．01） 。结论 缺氧、ANHD均为影响Qs/Qt与氧合的重要因素,OLV时ANHD应以不低于中度为准。

Effects of acute normovolemic hemodilution on intrapulmonary shunting and oxygenation during one-lung ventilation in dogs

Objective To evaluate the effects of different degrees of acute normovolemic hemodilution (ANH) on intrapulmonary shunting, oxygen delivery and consumption during one-lung ventilation(OLV) in dogs. Methods Twelve healthy mongrel dogs weighing 18-22 kg were anesthetized with Ⅳ pentobarbital sodium 20mg.kg-1, scopolamine 0.3 mg and pancuronium 0.2 mg. kg-1 and intubated with a left-sided Carlen' s tube. Correct positioning of the tube was verified by auscultation and by visual inspection after thoracotomy at the end of the experiment. The dogs were mechanically ventilated with 100% oxygen. PET CO2 was maintained between 4.67-6.00 kPa. ECG and rectal temperature were continuously monitored. An intravenous line was established for infusion of Lacted Ringer solution. SwanGanz catheter was inserted via femoral vein on one side for sampling of mixed venous blood and measurement of cardiac output (CO) by hemodilution technique and pulmonary artery pressure (PAP).Femoral artery on the other side was cannulated for measurement of mean arterial pressure(MAP) and arterial blood sampling. The body temperature was maintained between 35℃-39℃ during the experiment.Four degrees of ANH were achieved by blood withdrawal and replacement with an equal volume of gelofusin step by step: HD1 (Hct 35%), HD2 (Hct 25%), HD3 (15%) and HD4(7%-8%). The volume of blood to be removed was based upon the patients' estimated blood volume [EBV = body weight (kg) ×7% ], the beginning Hct(Hct0) and the target Hct (Hctt) V = EBV × (Hct0-Hctt)/Hctav. During each degree of hemodilution(HD) two lungs were ventilated(TLV) first followed by one-lung ventilation(OLV)Each ventilation condition was maintained for at least 15 min, then hemodynamics was measured and blood gas analysis including blood concentration of lactate of both arterial blood and mixed venous blood was performed, then Qs/Qt, oxygen delivery (DO2) and oxygen consumption(VO2) were calculated. Results With increasing hemodilution, MAP, pulmonary vaseular resistance(PVR), mean pulmonary arterialpressure(MPAP), PO2 and DO2 had a tendency to decrease, While oxygen extraction ratio(ERO2 ), blood lactate and Qs/Qt tended to increase. There were DO2-dependent VO2 and anaerobic metabolism during HD3 and HD4. PVR and MPAP increased significantly when one lung was being ventilated before HD and during HD1 and HD2 . During HD3 and HD4 there was little difference in PVR and MPAP between OLV and TLV. Qs/Qt increased by 74% (HD2), 164% (HD3) and 177% (HD4) during OLV. Conclusions The results show that both ANH and OLV can affect Qs/Qt and oxygenation. The degree of ANH should be limited to Hct 25 % during OLV.consumpation