Clinical Applications Of Transpulmonary Thermodilution Technique In Children With Congenital Heart Disease

Background Assessment of hemodynamics and cardiac function has a significant role in the diagnosis and management of congenital heart disease (CHD). As a clinical standard for hemodynamic monitoring during the last 30 years, the pulmonary artery thermodilution (PATD) method was infrequently applied in pediatrics and patients with CHD due to its relatively high degree of invasiveness and technical difficulties. A recently developed method, transpulmonary thermodilution technique (TPTD), offers an alternative to PATD for hemodynamic measurement. TPTD enables measurements of cardiac output (CO) and circulatory blood volumes in a less-invasive manner, and allows continuous CO (CCO) monitoring when combined with pulse contour (PC) analysis. There are still few studies of applications of this technique in children with congenital heart disease at present, and none in patients with intracardiac shunt so far.Objective1. To assess the accuracy and validity of CO and volume variables measured by TPTD.2. To determine the effect of intracardiac shunt on TPTD measurements.3. To explore the probable value of pulmonary blood volume (PBV) measured by TPTD in predicting early results after primary repair of tetralogy of Fallot (TOF).4. To evaluate the effectiveness of PiCCO system, which combines TPTD and PC analysis to measure CCO, in children after CHD surgery, and the factors influencing the accuracy.Methods and resultsI Ten immature pigs, mean weight 20.6 + 1.9 Kg, were studied during conditions of normovolemia, hypovolemia, and hypervolemia. Simultaneous CO measurements in each condition using TPTD and PATD were made. COpA wasdetermined with PATD, while C0Tp and intrathoracic blood volume (ITBV) were determined with TPTD. Central venous pressure (CVP) and heart rate (HR) were taken at the same time.A total of 90 simultaneous measurements of C0PA and C0TP in 3 different blood volume conditions were made. The mean C0TP was 3. 43 + 1. 19 L/min and COp,, was 3.18 + 1.18 L/min. The correlation coefficient between the two measurements was 0. 977 (P<0. 001) and the mean difference was 0. 25 + 0. 26 L/min. The mean difference between repeated measures of TPTD was -0.003 + 0.24 L/min and coefficient of variation 7.0%, while the mean difference of TPTD was 0. 017 + 0. 23 L/min and coefficient of variation 7. 2 %. Correlation analysis revealed a significant correlation both between ITBVI and CI and SVI, and between changes in ITBVI and changes in CI and SVI (r=0.812, 0.884; 0.938, 0.898). For comparison, correlations both between CVP and CI and SVI, and between changes in CVP and changes in CI and SVI were poor (r=0. 376, 0.452; 0.592, 0.551).II 52 children with CHD, aged 3 months to 16 years (median age 4. 2±3. 2 years), were studied during cardiac catheterisation or interventional therapy or intensive care after corrective CHD operation. The heart anomalies included 6 cases of ventricular septal defect (VSD), 11 cases of patent ductus arteriosus (PDA), 1 case of VSD combined with PDA, 26 cases of TOF, 2 cases of pulmonary atresia (PA), 1 case of interruption of the aortic arch (IAA), and 1 case of correction of VSD, ASD, coarctation of the aorta (CoA), double outlet right ventricle (DORV) and TOF each. 10 cases of PDA and 3 cases of VSD received interventional therapy. 3 groups were set according to intracardiac shunt: left-right shunt group (n=20), right-left shunt group (n=23) and no shunt group (n=18). C0Tp and ITBV were measured by TPTD, systemic blood flow (Qs), pulmonary blood flow (Qp) and effective pulmonary blood flow (eQp) by Fick method, C0Siraand COdoP by echocardiographic biplane Simpson' s and Doppler methods respectively.Good correlations were found between COTp and Qs in all 3 groups (r=0. 804, 0.789, 0.755), while between C0TP and C0Simonly in no shunt group (r=0. 884), and between C0TP and CO^p in right-left shunt group and no shunt group (r=0. 865, 0. 892). Mean ITBVI of the three groups were 507. 5+139. 0, 307.0+118.0 and 692.2 + 296.1 ml/m2 respectively. Correlation analysisrevealed a good correlation between ITBVI and Cl in no shunt group, while poor correlations in left-right shunt group and right-left shunt group. HI 152 patients, aged 3. 5 months to 15 years (median age 4. 2 + 3. 3 years), who underwent primary repair of TOF between April 1995 and March 2004 at the Cardiovascular Center of Children' s Hospital of Fudan University were reviewed. 27 preoperative and intraoperative variables potentially predictive of early postoperative death were analyzed in a univariate and multivariate manner respectively to identify risk factors.Early death occurred in 17 patients, 15 of which died of low cardiac output syndrome (LCOS). Univariate analysis demonstrated a significant association between early postoperative death and the following variables: weight at the time of surgery, age for cyanosis to be present, SaO2, AO/MPA, McGoon ratio, Nakata index, Qp/Qs, (Qs-eQp)/Qs, multiple aortopulmonary collateral arteries and transannular patching. In the multivariate model only AO/MPA and McGoon ratio were associated with early postoperative death.26 patients with TOF, aged 3. 2 months to 16 years (median age 4. 4 + 4. 2 years), who were hospitalized at the Cardiovascular Center of Children' s Hospital of Fudan University between March 2004 and February 2005 were investigated. The variables of risk factors determined in the retrospective research were obtained. ITBV index (ITBVI) and global end diastolic volume index (GEDVI) were measured by TPTD and PBV index (PBVI) was calculated.Of all the risk factors, only Qp/Qs show a significant correlation to PBVI (r=0.404). When analyzing the relationship between early postoperative outcomes and the risk factor variables in the 22 patients undergoing primary repair of TOF, only PBVI revealed significant associations with a prolonged mechanical ventilation time (>48 h) and the occurrence of LCOS. No significant association between other variables and early postoperative outcomes was found.IV Ten children aged 3.2 to 10 years (median age 5.9 + 1.9 years), who admitted to the intensive care unit (ICU) after corrective CHD operation were included in this study. The heart defects before correction included VSD (5 cases), ASD (2 cases), TOF (1 case), DORV (1 case) and CoA combinedwith PDA (1 case). Data points including CITP (cardiac index) measured by TPTD, CIpc measured by PC analysis immediately before and after the TPTD measurements (calibration) were obtained upon ICU admission and at 1, 3, 6, and 12 h thereafter.A total of 50 data points were obtained in the first 12 h after intensive care unit admission. Mean CITi> was 3.56 + 0.84 L/min/m2, CIPC immediately before calibration was 3.49 + 0.82 L/min/m2 and CIPC immediately after calibration was 3.54 + 0.85 L/min/m2. The correlation coefficient between CIPC immediately before calibration and CITP was 0. 791 (P<0. 001) and the mean difference was -0.21 + 0.53 L/min/m2. The correlation coefficient between CIPCimmediately after calibration and CITP was 0. 995 (/k0. 001) and the mean difference was -0. 02 + 0. 08 L/min/m2. The correlation coefficient between changes in CIPcand changes in CITPbetween 2 close data points was 0.855 (P<0.001) and mean difference was -0.19 + 0.51 L/min/m2. Correlation analysis revealed significant correlations between deviations of CIPC and changes in hemodynamic variables including CITP(r = -0. 589), SVITP(r=-0. 756) and SVRI (r = 0. 453).Conclusion1. TPTD for CO measurements is as accurate and precise as PATD.2. Volume variable (ITBVI) measured by TPTD has greater validity for assessment of circulatory volume status than filling pressure (CVP).3. For the patients with left-right or right-left intracardiac shunt, CO determined with TPTD is almost equal to Qs.4. The reliability of volume variables measured by TPTD could be affected by intracardiac shunt.5. LCOS is the main cause of early postoperative death after primary repair of TOF.6. pulmonary artery hypoplasia is the most important risk factor for early postoperative death after primary repair of TOF.7. Multiple risk factors should be considered when the choice of patients for primary repair of TOF is made.8. PBV measured by TPTD has probable value in predicting early outcomes after primary repair of TOF.