Continuous haemodynamic monitoring in children: use of transoesophageal Doppler

Cardiac Output Assessments in Anesthetized Children: Dynamic Capnography Versus Esophageal Doppler

BACKGROUND

The objective of this study was to compare esophageal Doppler cardiac output (COEDM) against the reference method effective pulmonary blood flow cardiac output (COEPBF), for agreement of absolute values and ability to detect change in cardiac output (CO) in pediatric surgical patients. Furthermore, the relationship between these 2 methods and noninvasive blood pressure (NIBP) parameters was evaluated.

METHODS

Fifteen children American Society of Anesthesiology (ASA) I and II (median age, 8 months; median weight, 9 kg) scheduled for surgery were investigated in this prospective observational cohort study. Baseline COEPBF/COEDM/NIBP measurements were made at positive end-expiratory pressure (PEEP) 3 cm H2O. PEEP was increased to 10 cm H2O and COEPBF/COEDM/NIBP was recorded after 1 and 3 minutes. PEEP was then lowered to 3 cm H2O, and all measurements were repeated after 3 minutes. Finally, 20-µg kg-1 intravenous atropine was given with the intent to increase CO, and all measurements were recorded again after 5 minutes. Paired recordings of COEDM and COEPBF were examined for agreement and trending ability, and all parameters were analyzed for their responses to the hemodynamic challenges.

RESULTS

Bias between COEDM and COEPBF (COEDM - COEPBF) was -17 mL kg-1 min-1 (limits of agreement, -67 to +33 mL kg-1 min-1) with a mean percentage error of 32% (95% confidence interval [CI], 25-37) and a concordance rate of 71% (95% CI, 63-80). The hemodynamic interventions caused by PEEP manipulations resulted in significant decrease in COEPBF absolute numbers (155 mL kg-1 min-1 [95% CI, 151-159] to 127 mL kg-1 min-1 [95% CI, 113-141]) and a corresponding relative decrease of 18% (95% CI, 14-22) 3 minutes after application of PEEP 10. No corresponding decreases were detected by COEDM. Mean arterial pressure showed a relative decrease with 5 (95% CI, 2-8) and 6% (95% CI, 2-10) 1 and 3 minutes after the application of PEEP 10, respectively. Systolic arterial pressure showed a relative decrease of 5% (95% CI, 2-10) 3 minutes after application of PEEP 10. None of the recorded parameters responded to atropine administration except for heart rate that showed a 4% relative increase (95% CI, 1-7, P = .02) 5 minutes after atropine.

CONCLUSIONS

COEDM was unable to detect the reduction of CO cause by increased PEEP, whereas COEPBF and to a minimal extent NIBP detected these changes in CO. The ability of COEPBF to react to minor reductions in CO, before noticeable changes in NIBP are seen, suggests that COEPBF may be a potentially useful tool for hemodynamic monitoring in mechanically ventilated children.

Comparison of three non-invasive hemodynamic monitoring methods in critically ill children

Introduction

Hemodynamic parameters measurements were widely conducted using pulmonary artery catheter (PAC) with thermodilution as a reference standard. Due to its technical difficulties in children, transthoracic echocardiography (TTE) has been widely employed instead. Nonetheless, TTE requires expertise and is time-consuming. Noninvasive cardiac output monitoring such as ultrasonic cardiac output monitor (USCOM) and electrical velocimetry (EV) can be performed rapidly with less expertise requirement. Presently, there are inconsistent evidences, variable precision, and reproducibility of EV, USCOM and TTE measurements. Our objective was to compare USCOM, EV and TTE in hemodynamic measurements in critically ill children.

Materials and methods

This was a single center, prospective observational study in critically ill children. Children with congenital heart diseases and unstable hemodynamics were excluded. Simultaneous measurements of hemodynamic parameters were conducted using USCOM, EV, and TTE. Inter-rater reliability was determined. Bland-Altman plots were used to analyse agreement of assessed parameters.

Results

Analysis was performed in 121 patients with mean age of 4.9 years old and 56.2% of male population. Interrater reliability showed acceptable agreement in all measured parameters (stroke volume (SV), cardiac output (CO), velocity time integral (VTI), inotropy (INO), flow time corrected (FTC), aortic valve diameter (AV), systemic vascular resistance (SVR), and stroke volume variation (SVV); (Cronbach’s alpha 0.76–0.98). Percentages of error in all parameters were acceptable by Bland-Altman analysis (9.2–28.8%) except SVR (30.8%) and SVV (257.1%).

Conclusion

Three noninvasive methods might be used interchangeably in pediatric critical care settings with stable hemodynamics. Interpretation of SVV and SVR measurements must be done with prudence.

Accuracy and precision of minimally-invasive cardiac output monitoring in children: a systematic review and meta-analysis

Several minimally-invasive technologies are available for cardiac output (CO) measurement in children, but the accuracy and precision of these devices have not yet been evaluated in a systematic review and meta-analysis. We conducted a comprehensive search of the medical literature in PubMed, Cochrane Library of Clinical Trials, Scopus, and Web of Science from its inception to June 2014 assessing the accuracy and precision of all minimally-invasive CO monitoring systems used in children when compared with CO monitoring reference methods. Pooled mean bias, standard deviation, and mean percentage error of included studies were calculated using a random-effects model. The inter-study heterogeneity was also assessed using an I(2) statistic. A total of 20 studies (624 patients) were included. The overall random-effects pooled bias, and mean percentage error were 0.13 ± 0.44 l min(-1) and 29.1 %, respectively. Significant inter-study heterogeneity was detected (P < 0.0001, I(2) = 98.3 %). In the sub-analysis regarding the device, electrical cardiometry showed the smallest bias (-0.03 l min(-1)) and lowest percentage error (23.6 %). Significant residual heterogeneity remained after conducting sensitivity and subgroup analyses based on the various study characteristics. By meta-regression analysis, we found no independent effects of study characteristics on weighted mean difference between reference and tested methods. Although the pooled bias was small, the mean pooled percentage error was in the gray zone of clinical applicability. In the sub-group analysis, electrical cardiometry was the device that provided the most accurate measurement. However, a high heterogeneity between studies was found, likely due to a wide range of study characteristics.

Perioperative hemodynamic monitoring with transesophageal Doppler technology

Invasive cardiac output (CO) monitoring, traditionally performed with transpulmonary thermodilution techniques, is usually reserved for high-risk patients because of the inherent risks of these methods. In contrast, transesophageal Doppler (TED) technology offers a safe, quick, and less invasive method for routine measurements of CO. After esophageal insertion and focusing of the probe, the Doppler beam interrogates the descending aortic blood flow. On the basis of the measured frequency shift between the emitted and received ultrasound frequency, blood flow velocity is determined. From this velocity, combined with the simultaneously measured systolic ejection time, CO and other advanced hemodynamic variables can be calculated, including estimations of preload, afterload, and contractility. Numerous studies have validated TED-derived CO against reference methods. Although the agreement of CO values between TED and the reference methods is limited (95% limits of agreement: median 4.2 L/min, interquartile range 3.3-5.0 L/min), TED has been shown to accurately follow changes of CO over time, making it a useful device for trend monitoring. TED can be used to guide perioperative intravascular volume substitution and therapy, with vasoactive or inotropic drugs. Various studies have demonstrated a reduced postoperative morbidity and shorter length of hospital stay in patients managed with TED compared with conventional clinical management, suggesting that it may be a valuable supplement to standard perioperative monitoring. We review not only the technical basis of this method and its clinical application but also its limitations, risks, and contraindications.

Continuous, non-invasive techniques to determine cardiac output in children after cardiac surgery: evaluation of transesophageal Doppler and electric velocimetry

BACKGROUND

Continuous and non-invasive measurement of cardiac output (CO) may contribute helpful information to the care and treatment of the critically ill pediatric patient. Different methods are available but their clinical verification is still a major problem.

AIM

Comparison of reliability and safety of two continuous non-invasive methods with transthoracic echocardiography (TTE) for CO measurement: electric velocimetry technique (EV, Aesculon) and transesophageal Doppler (TED, CardioQP). METHODS/MATERIAL: In 26 infants and children who had undergone corrective cardiac surgery at a median age of 3.5 (1-17) years CO and stroke volume (SV) were obtained by EV, TED and TTE. Each patient had five measurements on the first day after surgery, during mechanical ventilation and sedation.

RESULTS

Values for CO and SV from TED and EV correlated well with those of TTE (r = 0.85 and r = 0.88), but mean values were significantly lower than the values of TTE for TED (P = 0.02) and EV (P = 0.001). According to Bland-Altman analysis, bias was 0.36 l/min with a precision of 1.67 l/min for TED vs. TTE and 0.87 l/min (bias) with a precision of 3.26 l/min for EV vs. TTE. No severe adverse events were observed and the handling of both systems was easy in the sedated child.

CONCLUSIONS

In pediatric patients non-invasive measurement of CO and SV with TED and EV is useful for continuous monitoring after heart surgery. Both new methods seem to underestimate cardiac output in terms of absolute values. However, TED shows tolerable bias and precision and may be helpful for continuous CO monitoring in a deeply sedated and ventilated pediatric patient, e.g. in the operating room or intensive care unit.

Cardiac output measurement in children: comparison of the Ultrasound Cardiac Output Monitor with thermodilution cardiac output measurement

OBJECTIVE

To compare the assessment of cardiac output (CO) in children using the noninvasive Ultrasound Cardiac Output Monitor (USCOM) with the invasive pulmonary artery catheter (PAC) thermodilution cardiac output measurement.

DESIGN AND SETTING

Prospective observational study in a tertiary center for pediatric cardiology of a university children's hospital.

PATIENTS

Twenty-four pediatric patients with congenital heart disease without shunt undergoing cardiac catheterization under general anesthesia.

MEASUREMENTS AND RESULTS

CO was measured by USCOM using a suprasternal CO Doppler probe in children undergoing cardiac catheterization. USCOM data were compared to CO simultaneously measured by PAC thermodilution technique. Measurements were repeated three times within 5 min in each patient. A mean percentage error not exceeding 30% was defined as indicating clinical useful reliability of the USCOM. CO values measured by PAC ranged from 1.3 to 5.3 l/min (median 3.6 l/min). Bias and precision were -0.13 and 1.34 l/min, respectively. The mean percentage error of CO measurement by the USCOM compared to PAC thermodilution technique was 36.4% for USCOM.

CONCLUSIONS

Our preliminary data demonstrate that cardiac output measurement in children using the USCOM does not reliably represent absolute CO values as compared to PAC thermodilution. Further studies must evaluate the impact of incorporating effective aortic valve diameters on CO measurement using the USCOM.

Cardiac output measurement using a modified carbon dioxide Fick method: a validation study in ventilated lambs

Cardiac output can be measured using a modified carbon dioxide Fick (mCO2F) method. A validation study was performed comparing mCO2F method-derived cardiac output (Q(mCO2F)) with invasively measured pulmonary blood flow. In seven randomly bred ventilated newborn lambs, cardiac output was manipulated by creating hemorrhagic hypotension. When steady state was reached, Q(mCO2F) was measured. Gas analysis was performed in simultaneously obtained arterial and venous blood samples (right atrium [RA], superior vena cava [SVC], and inferior vena cava [IVC]). Carbon dioxide exchange and pulmonary blood flow was measured continuously using a CO2SMO Plus monitor and a pulmonary ultrasonic flow probe (Q), respectively. Mean bias, defined as Q(mCO2F) - Q(ufp), was small (respectively, -0.082 L.min, -0.085 Lx min(-1) and -0.183 Lxmin(-1) for venous sampling from RA, SVC, and IVC). The limits of agreement were -0.328 to 0.164 Lxmin(-1) (RA), -0.335 to 0.165 Lxmin(-1) (SVC), and 0.415 to 0.049 Lxmin(-1) (IVC). In conclusion, measurement of cardiac output with the mCO2F method is reliable and easily applicable in ventilated newborn lambs. For clinical use, the site of venous blood sampling is of minor importance.

Accuracy and repeatability of pediatric cardiac output measurement using Doppler: 20-year review of the literature

OBJECTIVE

Review of the accuracy and repeatability of Doppler cardiac output (CO) measurements in children.

DESIGN

Publications in the scientific literature retrieved using a computerized Medline search from 1982-2002 and a manual review of article bibliographies. Studies comparing Doppler flow measurements with thermodilution, Fick, or dye dilution methods in the pediatric critical care setting were identified to assess the bias, precision, and intra- and interobserver repeatability of Doppler CO measurement. Where results were not suitable for comparison and the original measurements available, data were re-analyzed using appropriate statistical methods and presented in comparative tables.

RESULTS

The precision of pediatric Doppler CO measurements compared to thermodilution, dye dilution, or Fick methods is around 30% and repeatability varies from less than 1% to 22%. Bias is generally less than 10% but varies considerably.

CONCLUSIONS

The bias, precision, and repeatability from study to study indicate that Doppler CO measurements are acceptably reproducible in children, with best results when used to track changes rather than absolute values, and using the transesophageal approach.

Assessment of cardiac output, intravascular volume status, and extravascular lung water by transpulmonary indicator dilution in critically ill neonates and infants

OBJECTIVE

To assess cardiac output, intrathoracic blood volume, global end-diastolic volume, and extravascular lung water in critically ill neonates and small infants using transpulmonary indicator dilution.

DESIGN

Prospective, observational, clinical study.

SETTING

Pediatric intensive care unit in a university hospital.

PARTICIPANTS

Critically ill neonates and small infants suffering from severe heart failure, respiratory failure, or sepsis (n = 10).

INTERVENTIONS

A total of 194 transpulmonary indicator dilution measurements were done. Global end-diastolic volume, intrathoracic blood volume, and stroke volume were measured and compared with standard hemodynamic parameters during the clinical course and before and after volume loading (16 +/- 3.7 mL/kg of 10% albumin solution) in 8 of 10 patients.

MEASUREMENTS AND MAIN RESULTS

A positive correlation was found for stroke volume index versus global end-diastolic volume (r = 0.76, p < 0.001) and intrathoracic blood volume (r = 0.56, p < 0.001). In contrast, no correlation was observed for stroke volume index versus central venous pressure. Volume loading resulted in significant increases in stroke volume index (p < 0.01), global end-diastolic volume (p < 0.01), and intrathoracic blood volume (p < 0.01); whereas central venous pressure, heart rate, mean arterial pressure, and extravascular lung water remained unchanged.

CONCLUSION

Transpulmonary indicator dilution enables measurement of cardiac output and intravascular volume status in critically ill neonates and infants at the bedside. The effects of volume loading on cardiac preload and effective change in stroke volume can be monitored by this technique, whereas central venous pressure was not indicative of changes in intravascular volume status.

Measurement of cardiac output and tissue perfusion

Recent technologic innovations have allowed a greater scope for cardiac output measurement in critically ill children. There is a move toward both less invasive and continuous methods, several of which also offer novel measures of preload. Many of the new methods are still undergoing preliminary evaluation in the pediatric population and will be summarized in this article.

Airway oximetry improves monitoring of dopamine effects in pediatric cardiac patients

OBJECTIVE

Simple, preferably noninvasive measurements of cardiac output are useful in pediatric patients receiving inotropic support. Oxygen saturation in pulmonary artery (Svo(2)) gives information about oxygen delivery and demand. Many inotropic drugs influence oxygen consumption. When effects on Svo(2) are studied, after a change in inotropic drug dosage, a change in oxygen consumption needs to be considered to accurately estimate the change in cardiac output. The aim of this investigation was to study whether information on inspired to end-tidal oxygen concentration difference (Fi-eto(2)) in addition to Svo(2) would improve estimation of changes in cardiac output.

DESIGN

Prospective observational study of Fi-eto(2), Svo(2), and oxygen saturation from central vein (Scvco(2)) for measurements of circulatory and metabolic effects of changes in dopamine dosage.

SETTING

Intensive care unit in a children's hospital.

PATIENTS

Twenty patients (age 4 days to 98 months) were studied after cardiac surgery.

INTERVENTIONS

Dopamine was administered in doses of 5, 10, 0, and 5 microg x kg(-1) x min(-1), 20 mins on each level.

MEASUREMENTS AND MAIN RESULTS

Cardiac output, measured with thermodilution, oxygen saturation from systemic artery (Sao(2)), Svo(2), and Scvco(2) were measured at 15 mins on each dopamine dose. Oxygen consumption was calculated by using the Fick equation. Fi-eto(2) was measured continuously with a paramagnetic oxygen analyzer. Both cardiac output and oxygen consumption were affected by changes in dopamine dosage. Relative changes in cardiac output were poorly correlated to the change in 1/Sa-vo(2) (r(2) =.54). Using Fi-eto(2) improved correlation between changes in cardiac output and changes in Fi-eto(2)/Sa-vo(2) (r(2) =.72). When Svo(2) was replaced by Scvco(2), the correlation between changes in cardiac output and changes in Fi-eto(2)/Sa-cvco(2) was only slightly altered (r(2) =.69).

CONCLUSIONS

Dopamine affects oxygen consumption as well as cardiac output. The accuracy of Svo(2)-based estimations of changes in cardiac output after dopamine is enhanced if changes in Fi-eto(2) are also considered. The more easily achievable Scvco(2) gave equivalent information as Svo(2).

Accuracy and limitations of continuous oesophageal aortic blood flow measurement during general anaesthesia for children: comparison with transcutaneous echography-Doppler

BACKGROUND

Because it is noninvasive and easy to use, oesophageal Doppler ultrasonography appears to be a worthwhile alternative for continuous assessment of cardiac output measurement during anaesthesia. A new oesophageal Doppler-echography device (Dynemo 3000, Sometec, Paris, France) can simultaneously determine aortic diameter and aortic blood flow at the same anatomical level (DEeso). The purpose of this study was to assess the accuracy and the potential limitations of this device during general anaesthesia among 20 children, using transcutaneous Doppler-echocardiography for comparison (DEtra).

METHODS

The reproducibility of paired measurements of mean aortic blood flow velocity (MAFV), aortic diameter (ØAo) and aortic blood flow (ABF) was analysed with both methods. Second, haemodynamic values were measured simultaneously in a blinded manner by both methods before and after surgery.

RESULTS

The percent change (%Delta) in MAFV and ABF was calculated with both methods for each child. The age and weight of children included in this study was 8.3 +/- 2.5 years and 27 +/- 8 kg, respectively. Intraoperator reproducibility of MAFVtra, ABFtra, MAFVeso and ABFeso, was 5.0 +/- 4.1%, 7.0 +/- 5.6%, 20.1 +/- 17.5% and 22.0 +/- 16.6%, respectively. ABFtra was significantly linked to ABFeso (R=0.55, P < 0.01). Bias +/- SD of ABF measurements between both methods was 2.2 +/- 1.1 l. min-1. %DeltaABFtra was significantly linked to %DeltaABFeso (R=0.62, P < 0.01). The bias +/- SD inherent to %DeltaABF measurements with both methods was -0.02 +/- 18%.

CONCLUSION

These results suggest that this new oesophageal Doppler method is unsuitable to measure accurately absolute CO values and relative CO changes in children during anaesthesia.

Pediatric cardiac output measurement using surface integration of velocity vectors: an in vivo validation study

OBJECTIVE

To test the accuracy and reproducibility of systemic cardiac output (CO) measurements using surface integration of velocity vectors (SIVV) in a pediatric animal model with hemodynamic instability and to compare SIVV with traditional pulsed-wave Doppler measurements.

DESIGN

Prospective, comparative study.

SETTING

Animal research laboratory at a university medical center.

SUBJECTS

Eight piglets weighing 10-15 kg.

INTERVENTIONS

Hemodynamic instability was induced by using inhalation of isoflurane and infusions of colloid and dobutamine.

MEASUREMENTS

SIVV CO was measured at the left ventricular outflow tract, the aortic valve, and ascending aorta. Transit time CO was used as the reference standard.

RESULTS

There was good agreement between SIVV and transit time CO. At high frame rates, the mean difference +/- 2 SD between the two methods was 0.01+/-0.27 L/min for measurements at the left ventricular outflow tract, 0.08+/-0.26 L/min for the ascending aorta, and 0.06+/-0.25 L/min for the aortic valve. At low frame rates, measurements were 0.06+/-0.25, 0.19+/-0.32, and 0.14+/-0.30 L/min for the left ventricular outflow tract, ascending aorta, and aortic valve, respectively. There were no differences between the three sites at high frame rates. Agreement between pulsed-wave Doppler and transit time CO was poorer, with a mean difference +/- 2 SD of 0.09+/-0.93 L/min. Repeated SIVV measurements taken at a period of relative hemodynamic stability differed by a mean difference +/-2 SD of 0.01+/-0.22 L/min, with a coefficient of variation = 7.6%. Intraobserver coefficients of variation were 5.7%, 4.9%, and 4.1% at the left ventricular outflow tract, ascending aorta, and aortic valve, respectively. Interobserver variability was also small, with a coefficient of variation = 8.5%.

CONCLUSIONS

SIVV is an accurate and reproducible flow measurement technique. It is a considerable improvement over currently used methods and is applicable to pediatric critical care.

Use of transesophageal Doppler ultrasonography in ventilated pediatric patients: derivation of cardiac output

OBJECTIVE

To ascertain if cardiac output (CO) could be derived from blood flow velocity measured in the descending aorta of ventilated children by transesophageal Doppler ultrasonography (TED) without the need for direct aortic cross sectional area measurement, and to evaluate the ability of TED to follow changes in CO when compared with femoral artery thermodilution.

DESIGN

Prospective, comparison study.

SETTING

A 16-bed pediatric intensive care unit of a university hospital.

PATIENTS

A total of 100 ventilated infants and children aged 4 days to 18 yrs (median age, 27 months). Diagnoses included postcardiac surgery (n = 58), sepsis/multiple organ failure (n = 32), respiratory disease (n = 5), and other (n = 5). A total of 55 patients were receiving inotropes or vasodilators.

INTERVENTIONS

When patients were hemodynamically stable, a TED probe was placed into the distal esophagus to obtain optimal signal, and minute distance (MD) was recorded. Five consecutive MD measurements were made concurrently with five femoral artery thermodilution measurements, and the concurrent measurements were averaged. CO was then manipulated by fluid administration or inotrope adjustment, and the readings were repeated.

MEASUREMENTS AND MAIN RESULTS

Femoral artery thermodilution CO ranged from 0.32 to 9.19 L/min, (median, 2.46 L/min), and encompassed a wide range of high and low flow states. Theoretical consideration revealed the optimal TED estimate for CO to be (MD x patient height2 x 10(-7)). Linear regression analysis yielded a power function model such that: estimated CO = 1.158 x (MD x height2 x 10(-7))(0.785), r2 = 0.879, standard error of the estimate = 0.266. Inclusion of a correction factor for potential changes in aortic cross-sectional area with hypo- and hypertension did not appreciably improve the predictive value of the model. MD was able to follow percentage changes in CO, giving a mean bias of 0.87% (95% confidence interval -0.85% to 2.59%), and limits of agreement of +/- 16.82%. The median coefficient of variation for MD was 3.3%.

CONCLUSIONS

TED provides a clinically accurate estimate of CO across the entire pediatric age range and is able to follow changes in CO.

Doppler flow measurement using surface integration of velocity vectors (SIVV): in vitro validation

Blood flow measurement using an improved surface integration of velocity vectors (SIVV) technique was tested in in vitro phantoms. SIVV was compared with true flow (12-116 mL/s) in a steady-state model using two angles of insonation (45 degrees and 60 degrees ) and two vessel sizes (internal diameter = 11 and 19 mm). Repeatability of the method was tested at various flow rates for each angle of insonation and vessel. In a univentricular pulsatile model, SIVV flow measured at the mitral inlet was compared to true flow (29-61 mL/s). Correlation was excellent for the 19-mm vessel (r(2)= 0.99). There was a systematic bias but close limits of agreement (mean +/- 2 SD = -24.1% +/- 7.6% at 45 degrees; +16.4% +/- 11.0% at 60 degrees ). Using the 11-mm vessel, a quadratic relationship was demonstrated between between SIVV and true flow (r(2) = 0.98-0.99), regardless of the angle of insonation. In the pulsatile system, good agreement and correlation were shown (r(2) = 0.94, mean +/- 2 SD = -4.7 +/- 10.1%). The coefficients of variation for repeated SIVV measurements ranged from 0.9% to 10.3%. This method demonstrates precision and repeatability, and is potentially useful for clinical measurements.

Development of a system to record cardiac output continuously in the newborn

Intermittent recordings of Doppler flow velocity and cardiac output are of value during intensive care of the sick newborn infant but result in repeated disturbance of the child. We describe a new device for making continuous precordial recordings of Doppler flow velocity from the pulmonary artery in healthy resting newborn infants. Optimal probe siting was evaluated in six babies, and signals were found to be best when the pulmonary artery was insonated from the mid left parasternum. Continuous recordings were made in 13 other babies. Pulmonary artery velocities and, by calculation, cardiac output were measured continuously over periods ranging from 24 to 60 min. Median right ventricular output ranged widely from 148 to 246 mL x kg(-1) x min(-1). In contrast, for individual babies, the values were remarkably stable: the interquartile ranges varied from 13.2 to 29.9 mL x kg(-1) x min(-1). The simultaneous display of signal power allowed independent assessment of artifactual changes in cardiac output. This technique is feasible in healthy term infants and now requires evaluation in the intensive care setting where it may provide useful information concerning trends and short-term variability in right ventricular output.

Pediatric echocardiography: applications and limitations

Echocardiography is an extraordinarily useful imaging technique in fetuses, infants, children, and adolescents. Recent technologic innovations have expanded its versatility in the pediatric population. However, limited societal resources, limitations inherent to ultrasound imaging, and numerous imaging options even within the field of pediatric echocardiography necessitate the discriminate and thoughtful use of echocardiography in children. The clinical assessment remains a critical prelude to echocardiographic examination of the pediatric cardiovascular system.

Advances in echocardiographic diagnostic modalities for the pediatrician

Two-dimensional Doppler echocardiography has become the primary diagnostic tool in the assessment of infants and children with congenital and acquired heart disease. Over the past 10 years, specialized echocardiographic techniques have also become critical components in the evaluation and treatment of these patients. Using fetal echocardiography enables us to image the heart early in gestation and have begun to understand those lesions that can develop and progress in utero. Transesophageal echocardiography has allowed you to image the patient with congenital heart disease during repair in the operating room and in the cardiac catheterization laboratory so that adequacy of the repair can be assess and any residual lesions addressed immediately. Both of these specialized techniques are discussed in detail, with a brief overview at the three-dimensional future of echocardiography in the pediatric 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 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.