应用经肺热稀释技术评价幼猪心输出量和容量负荷

Assessment of Cardiac Output and Volume Load by Transpulmonary Thermodilution Technique in Immature Pigs

目的 评价经肺热稀释法（TPTD）测量心输出量（CO）的准确性,以及该方法测量的胸内血容量指数（ITBVI）用于评价容量负荷的有效性.方法 研究10只幼猪,体重（20.6±1.9） kg.分别在基础血容量、高血容量和低血容量状态下进行同步的肺动脉热稀释法（PATD）测量CO （COPA）和TPTD测量CO（COTP）、ITBVI,每种状态下连续测量3次,同时记录中心静脉压（CVP）和心率.分析不同血容量状态下CVP、ITBVI与心指数（CI）、每搏输出量指数（SVI）的相关性.结果 共进行90次同步热稀释法测量CO.COTP与COPA相关系数为0.977 （P＜0.001）,平均偏差为（0.25 ±0.26） L/min（95％ CI：0.20～0.30 L/min,P＜0.001）.COTP变异系数为3.7％,COPA变异系数为5.4％.与基础血容量状态比较,高血容量状态下CVP和ITBVI均显著升高（P=0.002、0.019）,低血容量状态下ITBVI显著下降（P＜0.001）,但CVP的差异无统计学意义（P=0.050）.相关分析显示ITBVI与CI和SVI在基础血容量状态下呈高度正相关（r =0.741,P=0.014;r=0.885,P=0.001）,在高血容量和低血容量状态下均无显著相关性;CVP与CI和SVI在各种血容量状态下均无显著相关性.结论 TPTD在不同血容量状态下测量CO的准确度和精确度均理想,其测量的ITBVI与CVP比较可更有效地反映容量负荷.

Objective To assess the accuracy of cardiac output （CO） measured by transpulmonary thermodilution technique （TPTD） and explore the validity of intrathoracic blood volume index （ITBVI） for assessment of circulatory volume status.Methods Ten immature pigs with a mean weight of （20.6 ± 1.9） kg were studied during the conditions including normovolemia,hypervolemia,and hypovolemia.Simultaneous CO was measured in each condition using pulmonary artery thermodilution （PATD） method and TPTD.More specifically,CO （COPA） was determined with PATD,while CO （COTP） and ITBVI were determined with TPTD.All measurements were repeated 3 times.Central venous pressure （CVP） and heart rate were measured at the same time.The potential correlations of CVP and ITBVI with cardiac index （CI） and stroke volume index （SVI） in each blood volume status were analyzed.Results A total of 90 simultaneous measurements of COPA and COTP in 3 different blood volume conditions were made.The correlation coefficient between the two measurements was 0.977 （P ＜0.001） and the mean difference was （0.25 ±0.26） L/min （95％ CI：0.20-0.30 L/min,P ＜0.001）.The coefficient of variation of COTP was 3.7％,while COPA was 5.4％.Compared with those in normovolemia,CVP and ITBVI in hypervolemia significantly increased （P =0.002,0.019）,ITBVI in hypovolemia decreased significantly （P ＜ 0.001）,and CVP in hypovolemia decreased insignificantly （P =0.05）.Correlation analysis revealed a significant correlation between ITBVI with CI and SVI in normovolemia （r =0.741,P =0.014; r =0.885,P =0.001）.In contrast,correlations between CVP with CI and SVI were poor.Conclusions TPTD can accurately and precisely measure CO in different blood volume conditions.ITBVI measured by TPTD has better validity for the assessment of circulatory volume status than CVP.