颈动脉速度时间积分变异度预测小潮气量机械通气患者容量反应性的临床研究

Clinical research of velocity time integral variation of the carotid artery for predicting volume responsiveness in patients me⁃chanically ventilated at low tidal volumes

目的评价颈动脉速度时间积分变异度(△VTI)预测小潮气量机械通气患者容量反应性的准确性。方法择期全麻下行胃肠手术的患者50例,年龄50~70岁,美国麻醉医师协会(ASA)分级Ⅰ、Ⅱ级。所有患者全麻诱导气管插管后行小潮气量通气(潮气量7 ml/kg),待血流动力学平稳后[容量负荷试验(VE)前]于颈动脉中段使用脉冲多普勒测量颈动脉速度时间积分(VTI)及颈动脉峰值流速(Vpeak)。随后暂将潮气量改为9 ml/kg,并连接Vigileo系统后行VE,记录VE前和VE后每搏量(SV),并计算每搏量变异率(△SV)。依据△SV将患者分为两组:有反应组(R组,△SV≥15%,27例)和无反应组(N组,△SV<15%,23例)。随后再次行小潮气量通气(潮气量7 ml/kg),待血流动力学平稳后(VE后)测量颈动脉VTI及颈动脉Vpeak,计算颈动脉速度时间积分变异度(△VTI)和峰值流速变异度(△Vpeak),并记录VE前和VE后的平均动脉压(MAP)和心率。采用受试者操作特征(ROC)曲线对△VTI、△Vpeak进行分析,并计算最佳Youden指数时的诊断阈值、敏感度、特异度、曲线下面积(AUC)及95%置信区间(CI),评价△VTI、△Vpeak预测小潮气量机械通气患者容量反应性的准确性。结果与VE前比较,两组患者VE后MAP升高(P<0.05),心率、△VTI、△Vpeak均降低(均P<0.05)。与N组比较,R组VE前MAP降低(P<0.05),心率、△VTI、△Vpeak均升高(均P<0.05);VE后MAP降低(P<0.05),△VTI升高(P<0.05),心率、△Vpeak差异无统计学意义(均P>0.05)。ROC曲线分析结果显示:△VTI预测小潮气量机械通气患者容量反应性阳性的诊断阈值为12.35%,敏感度为74.1%,特异度为91.3%,AUC为0.902(95%CI 0.820~0.984,P<0.05)。△Vpeak预测小潮气量机械通气患者容量反应性阳性的诊断阈值为10.70%,敏感度为55.6%,特异度为95.7%,AUC为0.873(95%CI 0.730~0.943,P<0.05)。结论△VTI可准确预测小潮气量机械通气患者容量反应性。

Objective To evaluate the accuracy of velocity time integral variation(△VTI)of the carotid artery for predicting volume responsiveness in patients mechanically ventilated at a low tidal volume.Methods A total of 50 patients,aged 50 to 70 years,American Society of Anesthesiologists(ASA)gradeⅠorⅡ,who underwent elective gastrointestinal surgery under general anesthesia were selected.All the patients were ventilated at a low tidal volume(tidal volume 7 ml/kg)after induction of tracheal intubation under general anesthesia.When the hemodynamics became stable[before the volume loading test(VE)],the velocity time integral(VTI)and peak velocity(Vpeak)were measured by a pulsed Doppler in the middle of the carotid.The tidal volume was then temporarily changed to 9 ml/kg and VE was conducted after connecting the Vigileo system.The stroke volume(SV)was recorded before and after VE,and the stroke volume variation(△SV)was calculated.According to△SV,the patients were divided into two groups:a response group(group R,△SV≥15%,n=27)and a non-response group(group N,△SV<15%,n=23).Then,all the patients were ventilated at a low tidal volume(tidal volume 7 ml/kg),when the hemodynamics became stable(after VE),VTI and Vpeak were measured in the carotid.The△VTI and peak velocity variation(△Vpeak)were calculated.Furthermore,the mean arterial pressure(MAP),and heart rate were recorded before and after VE.A receiver operating characteristic(ROC)curve was plotted to analyze the△VTI and△Vpeak,while the cut-off value,sensitivity,specificity,area under the curve(AUC)and 95%confidence interval(CI)were calculated at the optimal Youden index.The accuracy of△VTI and△Vpeak in predicting volume responsiveness in patients mechanically ventilated at a low tidal volume was evaluated.Results Compared with those before VE,both groups showed increases in MAP(all P<0.05),but decreases in heart rate,△VTI and△Vpeak after VE(all P<0.05).Compared with group N,group R presented decreases in MPA(P<0.05)and increases in heart rate,△VTI and△Vpeak before VE(P<0.05);and showed decreases in MAP(P<0.05),and increases in△VTI after VE(P<0.05),without statistical differences in heart rate and△Vpeak(all P>0.05).According to ROC analysis,the cut-off value of△VTI in predicting volume responsiveness in patients mechanically ventilated at a low tidal volume was 12.35%,with a sensitivity of 74.1%and a specificity of 91.3%,and the AUC was 0.902[(95%CI 0.820~0.984),P<0.05].The cut-off value of△Vpeak in predicting volume responsiveness in patients mechanically ventilated at a low tidal volume was 10.70%,with a sensitivity of 55.6%and a specificity of 95.7%,and the AUC was 0.873[(95%CI 0.730,0.943),P<0.05].Conclusion△VTI can accurately predict volume responsiveness in patients mechanically ventilated at a low tidal volume.