潮气量对每搏输出量变异评价机械通气家猪血容量准确性的影响

Influence of Tidal Volume on Evaluation of Volume State by Stroke Volume Variation in Pigs with Ventilation

目的探讨每搏输出量变异(SVV)评价失血性休克家猪血容量状态的准确性,以及潮气量(VT)对其准确性的影响。方法将36只健康家猪充分镇静肌松,给予机械通气,随机分为失血性休克组、正常血容量组和高血容量组。逐步释放20%家猪血容量建立失血性休克家猪模型,输注相当于20%血容量的羟乙基淀粉建立高血容量模型。每组均按随机顺序调节VT=5 mL/kg(VT5)、VT=10 mL/kg(VT10)和VT=15 mL/kg(VT15),采用脉搏指示剂连续心排出量(PiCCO)监测中心静脉压(CVP)、平均动脉压(MAP)、心排指数(CI),每搏输出量指数(SVI)、胸腔内血容量指数(ITBVI)和SVV等血流动力学指标的变化。结果 VT10时,失血性休克组SVV较正常血容量组明显升高[(21±5)%比(11±2)%,P<0.05],高血容量组SVV较正常血容量组明显下降[(7±2)%比(11±2)%,P<0.05]。VT15时变化趋势与VT10时相同,但失血性休克组、正常血容量组及高血容量组SVV[(30±7)%、(19±3)%和(15±4)%]均>12%。VT5时,失血性休克组、正常血容量组及高血容量组SVV比较无显著差异[(8±6)%、(7±5)%和(7±4)%,P>0.05]。结论常规潮气量机械通气时SVV可准确反映血容量状态,小潮气量(5 mL/kg)时SVV准确性下降,较大潮气量(15 mL/kg)时SVV的临界值可能高于12%。

Objective To evaluate the influence of tidal volume on the accuracy of stroke volume variation（SVV） to predict volume state of pigs with v entilation.Methods Thirty-six healthy pigs were anesthetized after tracheal int ubation and ventilated.With the envelope method,they were randomized into a nor movolemia group,a hemaerrhagic shock group,and a hypervolemia group,with 12 pigs in each group.The pigs in the hemaerrhagic shock group were removed 20 perce nt of blood,and the pigs in the hypervolemia group received additional infusion of 20 percent 6% hydroxyethyl starch.In each group,ventilator settings were ch anged in a randomized order by changing VT [VT=5 mL/kg（VT5）,VT=10 mL/kg（VT10）,and VT=15 mL/kg（VT15）].Hemodynamic measurements [heart rat e（HR）,mea n arterial boold pressure（MAP）,systemic vascular resistance index（SVRI）, cardiac index（CI）,stroke volume index（SVI）,intrathoracic blood volume index（I TBVI）,and SVV] were obtained after 10 minutes of stabilization.Resu lts SVV was increased in the hemaerrhagic shock group comparing with the normovolemia grou p for VT10 [（21±5）% vs.（11±2）%,P0.05],but SVV was decr eased in the hype rvolemia group comparing with the normovolemia group [（7±2）% vs.（11±2）%,P0.05].The variation tendency for VT15 was the same with VT10,mo re over SVV wer e all above 12% for the hemaerrhagic shock group,the normovolemia group,and th e hypervolemia group [（30±7）%,（19±3）%,and（15±4）%].There were no sign ificant diffrences among the hemaerrhagic shock group,hypervolemia group and normovolemia group [（8±6）%,（7±5）%,and（7±4）%,P0.05] for VT5.Conclusions SVV was a precise indicator of cardiac prel oad,but SVV was less sensitive to the changes of volume during low tidal volume（5 mL/kg） ventilation.The thres hold of SVV for predicting fluid responsiveness maybe above 12% with a high tidal v olume（15 mL/kg） ventilation.