A comparison of thermodilution and pulsed Doppler cardiac output measurement in critically ill children

To evaluate the pulsed Doppler cardiac output method as a noninvasive means for determining cardiac output in critically ill children, we performed paired pulsed Doppler and thermodilution cardiac output determinations in 17 critically ill children. Commercially available equipment, specifically designed for this purpose, was employed. Forty paired thermodilution and pulsed Doppler determinations were made. There was a significant correlation between the two measurements (pulsed Doppler = 0.84 thermodilution + 0.39; r = 0.79, p less than 0.01). The ranges of thermodilution measurements (1.02 to 6.26 L/min; median 2.77 L/min) and pulsed Doppler measurements (1.13 to 6.35 L/min; median 2.57 L/min) were not different (p = 0.25). However, differences between individual paired thermodilution and pulsed Doppler measurements were large (-3.13 to 2.03 L/min; median 0.12 L/min), and the percentage difference between individual paired thermodilution and pulsed Doppler measurements ranged from 0.41% to 102.5% (median 12.7%). A discrepancy of 15% or more between thermodilution and pulsed Doppler was encountered in 18 (45%) of 40 of paired measurements (95% confidence interval: 29% to 61%), and one fourth of the paired measurements differed by more than 25%. We conclude that, as employed in this study, pulsed Doppler cardiac output determination is not sufficiently representative of the thermodilution output to be employed for hemodynamic monitoring in critically ill children.     

Noninvasive Measurement of Cardiac Output in Critically Ill Children

This study was performed to evaluate the hemodynamic status of children admitted to the intensive care unit, using suprasternal and transesophageal Doppler ultrasound, and to establish a suitable noninvasive technique to monitor trends in cardiac output in critically ill children. Twenty children were studied over a period of 6 months. The median age was 32.5 months and weight 14.5 kg. Minute distance (MD), which is a linear cardiac output parameter, was assessed. Seven simultaneous pairs of measurements of MD were made using transesophageal Doppler (TED) and suprasternal Doppler (SSD) by the same operator. Following a fluid challenge, seven repeat pairs of measurements were made. The mean percentage changes for MD by TED and SSD were 21.84 (SD 9.97) and 5.75 (SD 7.32). The average coefficients of variation for measurements of MD by TED and SSD were 2.34% and 15.98%, respectively. The mean difference in percentage change between MD, measured by TED and SSD, was 27.59 with a 95% confidence interval and wide limits of agreement. The repeatability of TED measurements was good, but the measurements by SSD were wide and erratic with poor reproducibility. Our study shows that TED is easy to use, reliable, and very useful for monitoring hemodynamic changes in critically ill children.     

Clinicians' abilities to estimate cardiac index in ventilated children and infants

OBJECTIVES: To evaluate the ability of clinicians involved in the provision of paediatric intensive care to estimate cardiac index in ventilated children, based on physical examination and clinical and bedside laboratory data. METHODS: Clinicians were exposed to all available haemodynamic and laboratory data for each patient, allowed to make a physical examination, and asked to first categorize cardiac index as high, high to normal, low to normal, or low, and then to quantify this further with a numerical estimate. Cardiac index was measured simultaneously by femoral artery thermodilution (coefficient of variation 5.37%). One hundred and twelve estimates were made by 27 clinicians on 36 patients (median age 34.5 months). RESULTS: Measured cardiac index ranged from 1.39 to 6.84 1/min/m2. Overall, there was poor correlation categorically (kappa statistic 0.09, weighted kappa 0.169) and numerically (r = 0.24, 95% confidence interval 0.06 to 0.41), although some variation was seen among the various levels of seniority. CONCLUSION: Assuming that objective measurement, and hence manipulation, of haemodynamic variables may improve outcome, these findings support the need for a safe, accurate, and repeatable technique for measurement of cardiac index in children who are critically ill.     

A comparison of pulmonary and femoral artery thermodilution cardiac indices in paediatric intensive care patients

We have assessed the agreement between pulmonary artery and femoral artery (COLD) thermodilution measurements of the cardiac index (C1) in a group of paediatric intensive care patients. The COLD method gave consistently higher cardiac index values than the pulmonary artery catheter (PAC); however, the difference was small, with a mean value of 0.191/min⁻¹ m⁻² or 4.4% of the mean cardiac index. This difference is not clinically important and suggests that, under these circumstances. the COLD system provides an acceptable alternative to the pulmonary artery catheter for measurement of the cardiac index at the bedside.     

Cardiac output and blood volume parameters using femoral arterial thermodilution

Background:  The pulse-induced continuous cardiac output (PiCCO) system is a less invasive method than pulmonary thermodilution for the measurement of cardiac output and estimating blood volume parameters. The normal values in children have not been defined. The purpose of the present paper was therefore to evaluate cardiac output and parameters of blood volume using femoral arterial thermodilution in critically ill children.
Methods:  A prospective study was performed in 17 critically ill children aged between 2 months and 14 years. Two measurements were taken for each determination of cardiac output, global end diastolic volume (GEDVI), intrathoracic blood volume index (ITBI), extravascular lung water index (ELWI), systolic volume index (SVI), stroke volume variation (SVV), cardiac function index (CFI), left ventricular contractility (dp/dt max), and the systemic vascular resistance index (SVRI).
Results:  One hundred and seventeen measurements were performed. The mean cardiac index (CI) was 3.5 ± 1.3 L/min per m². The GEDVI (399.7 ± 349.1 mL/m²), ITBI (574.5 ± 212.2 mL/m²) and dp/dt max (804.6 ± 372.1 mmHg/s) were lower than reported in adults, whereas ELWI (18.9 ± 9.3 mL/m2) and CFI (8 ± 2.5 L/min) where higher. The GEDVI, SVI, dp/dt max and CI increased with the weight of the patients whereas the ELWI values decreased.
Conclusions:  Femoral arterial thermodilution is a suitable technique for the measurement of cardiac output in critically ill children. The intrathoracic and intracardiac volumes are lower than in adults, whereas extrapulmonary water is higher; these values are related to the weight of the patient.     

Clinicians' abilities to estimate cardiac index in ventilated children and infants

OBJECTIVES—To evaluate the ability of clinicians involved in the provision of paediatric intensive care to estimate cardiac index in ventilated children, based on physical examination and clinical and bedside laboratory data.METHODS—Clinicians were exposed to all available haemodynamic and laboratory data for each patient, allowed to make a physical examination, and asked to first categorise cardiac index as high, high to normal, low to normal, or low, and then to quantify this further with a numerical estimate. Cardiac index was measured simultaneously by femoral artery thermodilution (coefficient of variation 5.37%). One hundred and twelve estimates were made by 27 clinicians on 36 patients (median age 34.5months).RESULTS—Measured cardiac index ranged from 1.39 to 6.84 l/min/m². Overall, there was poor correlation categorically (κ statistic 0.09,weighted κ 0.169) and numerically (r = 0.24, 95% confidence interval 0.06 to 0.41 ), although some variation was seen among the various levels of seniority. CONCLUSION—Assuming that objective measurement, and hence manipulation, of haemodynamic variables may improve outcome, these findings support the need for a safe, accurate, and repeatable technique for measurement of cardiac index in children who are critically ill.     

Intraobserver variation in Doppler ultrasound assessment of pulmonary artery pressure.

Intraobserver variation associated with the non-invasive assessment of pulmonary artery pressure (PAP), using measurement of pulmonary artery Doppler derived systolic time intervals, was investigated. Forty pairs of independent ultrasound examinations of the pulmonary artery were performed by a single observer in 20 preterm infants, median gestation 27 weeks (range 24-31 weeks). Median age at study was 17 days (range 1-47 days). paired measurements of acceleration time (AT), ratio between acceleration time and right ventricular ejection time (AT:RVET), corrected AT, and corrected AT:RVET were compared to assess intraobserver agreement. For the corrected AT:RVET ratio, the mean percentage difference between observations was -0.9% (95% confidence intervals -5.0 to 3.1%). The limits of agreement for the two measurements were -26.3 to 24.5%. The coefficient of repeatability was 25.4%. Variation for other indices was similar. Non-invasive assessment of PAP using Doppler derived systolic time intervals is associated with considerable intraobserver variation.     

Comparison Between Cardiac Output Measured by the Pulmonary Arterial Thermodilution Technique and that Measured by the Femoral Arterial Thermodilution Technique in a Pediatric Animal Model

This study compares the correlation between two methods for the determination of cardiac output—the pulmonary arterial thermodilution technique using the Swan–Ganz catheter and the femoral arterial thermodilution technique using a pulse contour analysis computer (PiCCO) catheter. We performed a prospective animal study using 16 immature Maryland pigs weighing 9 to 16 kg. A 5.5- or 7.5-Fr Swan–Ganz catheter was introduced into the femoral or jugular vein, and a 4- or 5-Fr arterial PiCCO catheter was introduced into the femoral artery. In each animal, we made measurements of cardiac output at 30-minute intervals, simultaneously by pulmonary arterial thermodilution and femoral arterial thermodilution, before, during, and after hemodiafiltration carried out via different venous catheters, recording a total of 78 measurements. The mean Swan–Ganz cardiac output was 2.22 ± 0.94 L/min, and mean PiCCO cardiac output was 1.94 ± 0.80 L/min (no significant difference). The mean difference (bias) of differences (limits of agreement) was 0.2812. The differences between the methods increased with higher cardiac output, but the percentage differences in relation to cardiac output remained stable. Good correlation was found between the two methods: single-measure intraclass correlation was 0.8892 (95% confidence interval, 0.54–0.95). There were no differences between the 5.5- and 7.5-FR Swan–Ganz catheters or between the 4- and 5-Fr PiCCO catheters. Femoral arterial thermodilution cardiac output measurements correlated well with pulmonary arterial thermodilution cardiac output measurements in a pediatric animal model.     

Cardiac output measured by thermodilution in infants and children

To determine the accuracy and reproducibility of cardiac output determination by thermodilution (COT) in children, simultaneous outputs were measured by the Fick technique (COF) (using measured oxygen consumption) and thermodilution in 26 children, ranging in age from 8 to 86 months, who were undergoing cardiac catheterization. There was excellent correlation between mean output by thermodilution and by the Fick technique: COT = 1.10 COF -- 0.2 l/minute, R = 0.91. In three-quarters of the patients with COT differed by 15% or less and in none differed by more than 25%. Serial values of thermodilution outputs were reproducible in each patient with a SD of 5.5%. Our observations indicate that COT is accurate, reproducible, and valuable in the care of critically ill infants and children.     

Monitoring cardiac function in intensive care.

Systolic cardiac function results from the interaction of four interdependent factors: heart rate, preload, contractility, and afterload. Heart rate can be quantified easily at the bedside, while preload estimation has traditionally relied on invasive pressure measurements, both central venous and pulmonary artery wedge. These have significant clinical limitations; however, adult literature has highlighted the superiority of several novel preload measures. Measurement of contractility and afterload is difficult; thus in clinical practice the bedside assessment of cardiac function is represented by cardiac output. A variety of techniques are now available for cardiac output measurement in the paediatric patient. This review summarises cardiac function and cardiac output measurement in terms of methodology, interpretation, and their contribution to the concepts of oxygen delivery and consumption in the critically ill child.     

Monitoring cardiac function in intensive care

Systolic cardiac function results from the interaction of four interdependent factors: heart rate, preload, contractility, and afterload. Heart rate can be quantified easily at the bedside, while preload estimation has traditionally relied on invasive pressure measurements, both central venous and pulmonary artery wedge. These have significant clinical limitations; however, adult literature has highlighted the superiority of several novel preload measures. Measurement of contractility and afterload is difficult; thus in clinical practice the bedside assessment of cardiac function is represented by cardiac output. A variety of techniques are now available for cardiac output measurement in the paediatric patient. This review summarises cardiac function and cardiac output measurement in terms of methodology, interpretation, and their contribution to the concepts of oxygen delivery and consumption in the critically ill child.     

Comparison of temporal artery thermometer to standard temperature measurements in pediatric intensive care unit patients.

OBJECTIVES: To determine the accuracy of noninvasive infrared temporal artery thermometry compared with rectal, axillary, and pulmonary artery catheter measurements in pediatric intensive care patients, and to determine whether temporal artery temperatures are affected by circulatory shock or by vasopressor use. We hypothesized that temporal artery temperatures do not differ from axillary and rectal temperatures in critically ill children, but temporal artery accuracy is decreased by shock or vasopressor use. DESIGN: Observational study, unblinded. SETTING: Pediatric intensive care unit of a quarternary referral children's hospital. PATIENTS: Seventy-five temperature comparison pairs were obtained in 44 pediatric intensive care unit patients. INTERVENTIONS: Temperature measurements were made using a temporal artery thermometer with simultaneously obtained rectal, axillary, and, when available, pulmonary artery catheter measurements. MEASUREMENTS AND MAIN RESULTS: Mean bias was calculated between comparison pairs using each temperature method. Bland-Altman analysis demonstrated wide variability between methods. No significant differences in mean bias were seen between method pairs for all temperatures, but bias was significantly less in pulmonary artery catheter-rectal pairs compared with other method pairs. In febrile (> 38 degrees C) patients, bias in rectal-temporal artery and rectal-axillary was significantly greater than in temporal artery-axillary pairs (p < .001). Mean bias in pulmonary artery catheter-rectal pairs was also significantly smaller than in other pairs for all patients (p = .008) and febrile patients (p = .049). Presence of shock or vasopressor use did not significantly increase bias in any comparison pair. Sensitivity and specificity of both temporal artery and axillary for diagnosing fever were similar and improved with fever definition at temperatures > 38.5 degrees C. CONCLUSIONS: Temporal artery and axillary temperature measurements showed variability to rectal temperatures but had marked variability in febrile children. Neither was sufficiently accurate to recommend replacing rectal or other invasive methods. As temporal artery and axillary provide similar accuracy, temporal artery thermometers may serve as a suitable alternative for patients in whom invasive thermometry is contraindicated.     

Can near infrared spectroscopy of the liver monitor tissue oxygenation?

Measurement of the hepatic oxygenation index by near infrared spectroscopy is a suitable method to estimate the oxygenation and can be a non-invasive means to continuously monitor tissue perfusion and to detect early haemodynamic disturbances in critically ill children.     

Continuous wave doppler cardiac output: Use in pediatric patients receiving inotropic support

Summary Doppler estimates of cardiac output have been shown to correlate closely with invasive measurement of cardiac output in hemodynamically stable adults and children. However, this method has not been validated in hemodynamically unstable pediatric patients. To assess the accuracy of continuous wave Doppler echocardiography in pediatric patients with unstable hemodynamics, we performed 27 simultaneous Doppler and thermodilution comparisons in 12 pediatric patients receiving inotropic support and afterload-reducing agents. Doppler cardiac output was calculated using aortic diameter measured from long-axis two-dimensional echocardiograms at three different sites: the aortic valve anulus, the aortic root at the sinuses of Valsalva, and the ascending aorta. For all measurements, there was a close correlation between Doppler and thermodilution techniques. However the site of measurement of aortic diameter had a significant impact on the strength on the correlation and the variability between Doppler and thermodilution. The best correlation and least variability were obtained using the aortic valve anulus diameter (r=0.94). On serial determinations, percent change in Doppler stroke volume correlated well with thermodilution stroke volume (r=0.87) and was useful in detecting both direction and magnitude of change in thermodilution stroke volume. Despite the administration of positive inotropic and afterload-reducing agents, Doppler cardiac output is a useful method for estimating cardiac output in hemodynamically unstable pediatric patients.     

无创血流动力学监测在急危重症患儿中的临床应用

血流动力学监测是急危重症患儿病情评估及抢救治疗中重要的监测手段,对掌握病情、早期发现循环功能异常、指导针对性用药有重要意义.目前监测血流动力学的方法很多,但各自的缺陷限制了其在儿科中的广泛应用.近年来彩色多普勒技术的广泛应用得以推出新型无创血流动力学监测仪,其具有无创性、可连续动态监测性、适合床边使用等优点,为危重症小...     

Low-volume peritoneal dialysis in 116 neonatal and paediatric critical care patients

Acute renal insufficiency accounts for high mortality in paediatric intensive care patients, particularly in infants. Peritoneal dialysis, usually carried out with dialysate volumes of >20 ml/kg body weight, increases pulmonary artery pressure, which may compromise myocardial function in critical illness. In this paper we report our experiences with the use of lower dialysate volumes in the treatment of critically ill children with renal impairments. We suggest that low-volume peritoneal dialysis is able to achieve adequate ultrafiltration, which relieves overhydration in ventilated and haemodynamically compromised children. A total of 116 paediatric intensive care patients treated between 1992 and 2000 was the subject of this investigation. Diagnosis, indication for dialysis, arterial and central venous pressure, blood gases, creatinine, blood urea nitrogen, urinary output at installation, ultrafiltration, fluid balance, duration and complications during dialysis as well as survival were investigated. The overall mortality was 53%. The respective diagnoses and mortality rates were as follows: 65% of the patients suffered from cardiac diseases (54% mortality), 7% from renal diseases (13%) and 28% from multi-organ system failure (62%). Low-volume peritoneal dialysis was started at evidence of total body fluid overload with inadequate urinary output and resulted in a mean ultrafiltration of 2.8 ml/kg body weight per h. A negative fluid balance was achieved in 53% of patients, mainly in those suffering from hypervolaemia and minor oliguria. None of the complications resulted in death. CONCLUSION: early installation of low-volume peritoneal dialysis offers a safe and adequate ultrafiltration procedure for paediatric critical care patients suffering from minor oliguria and fluid overload.     

Comparison of Transpulmonary Thermodilution and Ultrasound Dilution Technique: Novel Insights into Volumetric Parameters from an Animal Model

Especially in critically ill children with cardiac diseases, fluid management and monitoring of cardiovascular function are essential. Ultrasound dilution technique (UDT) was recently introduced to measure cardiac output (CO) and volumetric parameters, such as intrathoracic and end-diastolic blood volume. We compared UDT with the well-established transpulmonary thermodilution (TPTD) method (PiCCO) for determining CO measurements and derived volumes in a juvenile animal model. Experiments were performed in 18 ventilated, anesthetized piglets during normovolemia and after isovolemic hemodilution. At baseline and 20 min after each step of isovolemic hemodilution, 3 independent measurements of CO and volumetric parameters were conducted with TPTD and UDT, consecutively, under hemodynamically stable conditions. We observed comparable results for CO measurements with both methods (mean 1.98 l/min; range 1.12–2.87) with a percentage error of 17.3% (r = 0.92, mean bias = 0.28 l/min). Global end-diastolic volume (GEDV) and intrathoracic blood volume (ITBV) by TPTD were almost two times greater than analogous volumes [central blood volume (CBV); total end-diastolic volume (TEDV)] quantified by UDT (CBV = 0.58 × ITBV + 27.1 ml; TEDV = 0.48 × GEDV + 23.1 ml). CO measurements by UDT were found to be equivalent and hence interchangeable with TPTD. Discrepancies in volumetric parameters could either be due to the underlying algorithm or different types of indicators (diffusible vs. nondiffusible). Compared with the anatomically defined heart volume, TPTD seems to overestimate end-diastolic volumes. Future studies will be necessary to assign these results to critically ill children and to validate volumetric parameters with reference techniques.     

Right ventricular performance and pulmonary haemodynamics in adolescent and adult patients with cystic fibrosis

A combined haemodynamic and radionuclide approach was used to evaluate right ventricular performance in 16 adolescent and adult patients with cystic fibrosis (CF). There were nine patients with mild arterial hypoxaemia (PaO₂>80% of predicted) and normal resting pulmonary artery pressure and seven patients with severe arterial hypoxaemia (PaO₂<70% of predicted) and resting pulmonary arterial hypertension (PH). The right ventricular ejection fraction (RVEF) by equilibrium angiocardiography using krypton 81^m as a tracer and stroke volume index (SVI) by thermodilution techniques were measured simultaneously and right ventricular end-diastolic and end-systolic volumes were derived. RVEF was normal in CF patients without PH (58.9±7.2%) but was reduced in those with PH (45.4±2.6%). There was a statistically significant inverse linear correlation between RVEF and afterload as assessed by mean pulmonary artery pressure and pulmonary vascular resistance (PVR: r=–0.78), indicating that RVEF ist afterload-dependent. Right ventricular function, however, as assessed by right ventricular end-systolic pressure-volume relations was even higher in CF patients with PH, indicating preserved or even increased right ventricular function in the face of an increased afterload stress.Abbreviations CF cystic fibrosis - PaO₂ arterial oxygen tension - PH pulmonary arterial hypertension - RVEF right ventricular ejection fraction - SVI stroke volume index - Pap pulmonary artery pressure - PVR pulmonary vascular resistance - COPD chronic obstructive pulmonary disease - VC vital capacity - FEV₁ forced expiratory volume in 1 s - RV resisdual volume - TLC total lung capicity - RVEDP right ventricular end-diastolic pressure - Pap_s systolic pulmonary artery pressure - Pap_d diastolic pulmonary artery pressure - PCWP pulmonary capillary wedge pressure - CO cardiac output - ED end-diastolic background-corrected counts - ES end-systolic background-corrected counts - CI cardiac index - RVEDVI right ventricular end-diastolic volume index - RVESVI right ventricular end-systolic volume index - P/V relation right ventricular end-systolic pressure/right ventricular end-systolic volume index - S-K score Shwachmann-Kulczycki score     

Haemodynamic features at presentation in persistent pulmonary hypertension of the newborn and outcome.

Thirty four newborns presenting with persistent hypoxaemia in the first three days of life underwent detailed haemodynamic assessment using Doppler echocardiography, including measurements of pulmonary arterial pressure (PAP), left ventricular (LV) function, and left ventricular output (LVO). Results were compared with values from 51 healthy babies, and those of survivors were compared with non-survivors. Four of the 34 babies were excluded from this analysis because one was found to have transposed great arteries, one had a large left-to-right shunt with no evidence of persistent pulmonary hypertension, and two had diffuse skeletal myopathy. Tricuspid regurgitation was present in 70%, permitting systolic PAP estimation. The pulmonary:systemic arterial pressure ratio range was 0.7:1 to 1.83:1 (mean 1.02:1). A patent duct was present in 83%, and flow patterns indicated PAP approaching, or above, systemic pressure in all. Systolic time interval ratio TPV/RVET (time to peak velocity at the pulmonary valve/right ventricular ejection time) was mostly (65%) in the normal range, and did not correlate with other PAP measurements. LV function was below the 10th centile in only 11%, but values for LVO lay below the 10th centile in 41%, and for left ventricular stroke volume index (LSVI) in 66%. Results of 18 survivors were compared with 10 non-survivors (excluding two premature babies who died early with pulmonary interstitial emphysema). There were no significant differences for any parameter of PAP or LV function, but LVO and LSVI were significantly lower in non-survivors: LVO survivors (mean (SD)), 205 (57), non-survivors 138 (63) ml/kg/minute (P < 0.01); LSVI survivors, 1.29 (0.51), non-survivors 0.86 (0.31) ml/kg (P < 0.05). All four babies with LVO < 100 ml/kg/minute died, and 6/7 babies with LSVI < 1 ml/kg died. Detailed echocardiographic evaluation shows that the haemodynamic features of persistent pulmonary hypertension are diverse and that clinical diagnosis can be incorrect. Low LV output and stroke volume, usually with normal LV function, were the only Doppler echocardiographic parameters to predict subsequent death. This correlation with outcome requires further prospective evaluation.     

Doppler determination of cardiac output in infants and children: Comparison with simultaneous thermodilution

Summary Ten children, aged six weeks to 13 years, without intracardiac shunts or lesions that could cause turbulent flow in the ascending aorta or aortic regurgitation, underwent cardiac catheterization, including cardiac output measurements by thermodilution. Simultaneously with each of six consecutive thermodilution injections, mean and maximal blood velocities in the ascending aorta were measured by pulsed Doppler echocardiography from the suprasternal notch. Aortic root and aortic orifice diameters were measured with M-mode and cross-sectional echocardiography. One patient had to be excluded from the analysis because of inadequate Doppler recordings. The best agreement with the results of the thermodilution was observed when internal systolic aortic root diameter was combined with mean velocity (r=0.97,y=0.90x+0.28, SEE=0.31 liters/min). When cardiac output was normalized for body size, there was still a good correlation between the results of these two methods.