Clinical validation of cardiac output measurements using femoral artery thermodilution with direct Fick in ventilated children and infants

Differences in Direct Fick and Thermodilution Measurements of Cardiac Output: Impact on Pulmonary Hypertension Classification

Direct Fick (DF) and bolus thermodilution (TD) are endorsed by pulmonary hypertension (PH) guidelines to measure cardiac output. In contemporary practice, agreement between methods is unknown, as are the diagnostic consequences of disagreement. We sought to evaluate the frequency and degree of disagreements between cardiac output measurement techniques and assess their impact on the hemodynamic assessment of PH. This was a single-center study that included 182 patients who had cardiac output concurrently measured by DF and TD. Oxygen consumption was measured by indirect calorimetry. Agreement between DF and bolus TD cardiac output was assessed using Bland-Altman analysis. The median DF and TD cardiac outputs were 5.42 L/min (interquartile range [IQR] 3.90-7.41) and 4.10 L/min (IQR 3.47-5.10), respectively. Significant disagreement was observed with DF yielding higher cardiac output results than TD. Mean error was proportional to cardiac output (-3.75% at 3 L/min to +44.5% at 7 L/min), and limits of agreement were wide. Disagreement was increased by 19.2% in the presence of least moderate tricuspid regurgitation and by 16.0% in patients with atrial fibrillation. Among 152 patients with PH, hemodynamic classification discordance occurred in 18 (11.8%) patients. Disagreement between DF and TD was observed, which resulted in a discrepant hemodynamic classification in approximately 12% of patients. These techniques should, therefore, not be used interchangeably for serial surveillance, and without a clinical gold standard, a rationale exists for utilizing both methods concurrently in certain clinical situations.

[Hemodynamic monitoring in pediatric anesthesia]

Perioperative mortality and morbidity in childhood essentially depend on the quality of the anesthesia. The Safe Anesthesia for every Tot (SafeTots) initiative takes this into account and has defined normotension, normovolemia and normal heart rate as quality criteria in pediatric anesthesia. Appropriate monitoring of pediatric hemodynamics is necessary to fulfil these criteria. This article provides an overview of currently used methods and techniques for instrumental and non-instrumental cardiovascular monitoring in children. The current study situation, recommendations and guidelines on the application as well as practical aspects of the measurement methods are explained as far as possible. For a better understanding, procedures not routinely used in clinical practice are described in more detail.

Impact of continuous vs. interval training on oxygen extraction and cardiac function during exercise in type 2 diabetes mellitus

PURPOSE

Exercise training improves exercise capacity in type 2 diabetes mellitus (T2DM). It remains to be elucidated whether such improvements result from cardiac or peripheral muscular adaptations, and whether these are intensity dependent.

METHODS

27 patients with T2DM [without known cardiovascular disease (CVD)] were randomized to high-intensity interval training (HIIT, n = 15) or moderate-intensity endurance training (MIT, n = 12) for 24 weeks (3 sessions/week). Exercise echocardiography was applied to investigate cardiac output (CO) and oxygen (O₂) extraction during exercise, while exercise capacity [([Formula: see text] (mL/kg/min)] was examined via cardiopulmonary exercise testing at baseline and after 12 and 24 weeks of exercise training, respectively. Changes in glycaemic control (HbA1c and glucose tolerance), lipid profile and body composition were also evaluated.

RESULTS

19 patients completed 24 weeks of HIIT (n = 10, 66 ± 11 years) or MIT (n = 9, 61 ± 5 years). HIIT and MIT similarly improved glucose tolerance (p_Time = 0.001, p_Interaction > 0.05), [Formula: see text] (mL/kg/min) (p_Time = 0.001, p_Interaction > 0.05), and exercise performance (W_peak) (p_Time < 0.001, p_Interaction > 0.05). O₂ extraction increased to a greater extent after 24 weeks of MIT (56.5%, p₁ = 0.009, p_Time = 0.001, p_Interaction = 0.007). CO and left ventricular longitudinal strain (LS) during exercise remained unchanged (p_Time > 0.05). A reduction in HbA1c was correlated with absolute changes in LS after 12 weeks of MIT (r = - 0.792, p = 0.019, LS at rest) or HIIT (r = - 0.782, p = 0.038, LS at peak exercise).

CONCLUSION

In patients with well-controlled T2DM, MIT and HIIT improved exercise capacity, mainly resulting from increments in O₂ extraction capacity, rather than changes in cardiac output. In particular, MIT seemed highly effective to generate these peripheral adaptations.

TRIAL REGISTRATION

NCT03299790, initially released 09/12/2017.

Increased FIO2 influences SvO2 interpretation and accuracy of Fick-based cardiac output assessment in cardiac surgery patients: A prospective randomized study

INTRODUCTION

The study aimed to reveal how the fraction of inspired oxygen (FIO2) affected the value of mixed venous oxygen saturation (SvO2) and the accuracy of Fick-equation-based cardiac output (Fick-CO).

METHODS

Forty two adult patients who underwent elective cardiac surgery were enrolled and randomly divided into 2 groups: FIO2 < 0.7 or >0.85. Under stable general anesthesia, thermodilution-derived cardiac output (TD-CO), SvO2, venous partial pressure of oxygen, hemoglobin, arterial oxygen saturation, arterial partial pressure of oxygen, and blood pH levels were recorded before surgical incision.

RESULTS

Significant differences in FIO2 values were observed between the 2 groups (0.56 ± 0.08 in the <70% group and 0.92 ± 0.03 in the >0.85 group; P < .001). The increasing FIO2 values lead to increases in SvO2, venous partial pressure of oxygen, and arterial partial pressure of oxygen, with little effects on cardiac output and hemoglobin levels. When comparing to TD-CO, the calculated Fick-CO in both groups had moderate Pearson correlations and similar linear regression results. Although the FIO2 <0.7 group presented a less mean bias and a smaller limits of agreement, neither group met the percentage error criteria of <30% in Bland-Altman analysis.

CONCLUSION

Increased FIO2 may influence the interpretation of SvO2 and the exacerbation of Fick-CO estimation, which could affect clinical management.

TRIAL REGISTRATION

ClinicalTrials.gov ID number: NCT04265924, retrospectively registered (Date of registration: February 9, 2020).

To Swan or Not to Swan: Indications, Alternatives, and Future Directions

The pulmonary artery catheter (PAC) has revolutionized bedside assessment of preload, afterload, and contractility using measured pulmonary capillary wedge pressure, calculated systemic vascular resistance, and estimated cardiac output. It is placed percutaneously by a flow-directed balloon-tipped technique through the venous system and the right heart to the pulmonary artery. Interest in the hemodynamic variables obtained from PACs paved the way for the development of numerous less-invasive hemodynamic monitors over the past 3 decades. These devices estimate cardiac output using concepts such as pulse contour and pressure analysis, transpulmonary thermodilution, carbon dioxide rebreathing, impedance plethysmography, Doppler ultrasonography, and echocardiography. Herein, the authors review the conception, technologic advancements, and modern use of PACs, as well as the criticisms regarding the clinical utility, reliability, and safety of PACs. The authors comment on the current understanding of the benefits and limitations of alternative hemodynamic monitors, which is important for providers caring for critically ill patients. The authors also briefly discuss the use of hemodynamic monitoring in goal-directed fluid therapy algorithms in Enhanced Recovery After Surgery programs.

Cardiac output monitoring: Technology and choice

The accurate quantification of cardiac output (CO) is given vital importance in modern medical practice, especially in high-risk surgical and critically ill patients. CO monitoring together with perioperative protocols to guide intravenous fluid therapy and inotropic support with the aim of improving CO and oxygen delivery has shown to improve perioperative outcomes in high-risk surgical patients. Understanding of the underlying principles of CO measuring devices helps in knowing the limitations of their use and allows more effective and safer utilization. At present, no single CO monitoring device can meet all the clinical requirements considering the limitations of diverse CO monitoring techniques. The evidence for the minimally invasive CO monitoring is conflicting; however, different CO monitoring devices may be used during the clinical course of patients as an integrated approach based on their invasiveness and the need for additional hemodynamic data. These devices add numerical trend information for anesthesiologists and intensivists to use in determining the most appropriate management of their patients and at present, do not completely prohibit but do increasingly limit the use of the pulmonary artery catheter.

Advances in Anesthesia Monitoring

During surgery, one of the primary functions of the anesthesiologist is to monitor the patient and ensure safe and effective conduct of anesthesia to provide the optimum operating conditions. Standard guidelines for perioperative monitoring have been firmly established by the American Society of Anesthesiologists. However, in recent years, new advances in technology has led to the development of many new monitoring modalities, especially involving the neurologic and cardiovascular systems. This article presents a targeted review to discuss the functions and limitations of these new monitors and how they are applied in the modern operating room setting.

Doppler echocardiography for assessment of systemic vascular resistances in cardiogenic shock patients

OBJECTIVE

Impaired vascular tone plays an important role in cardiogenic shock. Doppler echocardiography provides a non-invasive estimation of systemic vascular resistance. The aim of the present study was to compare Doppler echocardiography with the transpulmonary thermodilution method for the assessment of systemic vascular resistance in patients with cardiogenic shock.

METHODS

This prospective monocentric comparison study was conducted in a single cardiology intensive care unit (Hopital Nord, Marseille, France). We assessed the systemic vascular resistance index by both echocardiography and transpulmonary thermodilution in 28 patients admitted for cardiogenic shock, on admission and after the introduction of an inotrope or vasopressor treatment.

RESULTS

A total of 35 paired echocardiographic and transpulmonary thermodilution estimations of the systemic vascular resistance index were compared. Echocardiography values ranged from 1309 to 3526 dynes.s.m²/cm⁵ and transpulmonary thermodilution values ranged from 1320 to 3901 dynes.s.m²/cm⁵. A statistically significant correlation was found between echocardiography and transpulmonary thermodilution (r=0.86, 95% confidence interval (CI) 0.74, 0.93; P<0.0001). The intraclass correlation coefficient was 0.84 (95% CI 0.72, 0.92). The mean bias was -111.95 dynes.s.m²/cm⁵ (95% CI -230.06, 6.16). Limits of agreement were -785.86, 561.96.

CONCLUSIONS

Doppler echocardiography constitutes an accurate non-invasive alternative to transpulmonary thermodilution to provide an estimation of systemic vascular resistance in patients with cardiogenic shock.

The Correlation between the Change in Thoracic Fluid Content and the Change in Patient Body Weight in Fontan Procedure

Background

The thoracic fluid content (TFC) and its percent change compared to the baseline (TFCd0%) derived from a bioreactance technique using a noninvasive cardiac output monitoring (NICOM) device correlate well with the amount of fluid removal in patients undergoing hemodialysis and with intraoperative fluid balance in pediatric patients undergoing cardiac surgery. We hypothesized that TFC or TFCd0% would also be a useful indicator allowing fluid management in pediatric patients undergoing a Fontan procedure.

Methods

The medical records of patients who underwent an elective Fontan procedure were reviewed retrospectively. The intraoperative variables recorded at two time points were used in the analysis: when the NICOM data obtained just after anesthesia induction (T0) and just before transfer of the patient from the operating room to the ICU (T1). The analyzed variables were hemodynamic parameters, TFC, TFCd0%, stroke volume variation, body weight gain, change in the central venous pressure, and difference in the TFC (ΔTFC).

Results

The correlation coefficient between TFCd0% and body weight gain was 0.546 (p = 0.01); between TFCd0% and body weight gain% 0.572 (p = 0.007); and between TFCd0% and intraoperative fluid balance 0.554 (p = 0.009). The coefficient of determination derived from a linear regression analysis of TFCd0% versus body weight gain was 0.30 (p = 0.01); between TFCd0% and body weight gain% 0.33 (p = 0.007); and between TFCd0% and intraoperative fluid balance 0.31 (p = 0.009).

Conclusions

TFCd0% correlated well with body weight gain, body weight gain%, and intraoperative fluid balance. It is a useful indicator in the intraoperative fluid management of pediatric patients undergoing a Fontan procedure.

Trial Registration

This trial is registered with Clinical Research Information Service KCT0002062.

Cardiac Output Monitoring in Preterm Infants

Maintaining optimal circulatory status is a key component of preterm neonatal care. Low-cardiac output (CO) in the preterm neonate leads to inadequate perfusion of vital organs and has been linked to a variety of adverse outcomes with heightened acute morbidity and mortality and adverse neurodevelopmental outcomes. Having technology available to monitor CO allows us to detect low-output states and potentially intervene to mitigate the unwanted effects of reduced organ perfusion. There are many technologies available for the monitoring of CO in the preterm neonatal population and while many act as useful adjuncts to aid clinical decision-making no technique is perfect. In this review, we discuss the relative merits and limitations of various common methodologies available for monitoring CO in the preterm neonatal population. We will discuss the ongoing challenges in monitoring CO in the preterm neonate along with current gaps in our knowledge. We conclude by discussing emerging technologies and areas that warrant further study.

Liver and systemic hemodynamics in children with cirrhosis: Impact on the surgical management in pediatric living donor liver transplantation

Cirrhosis in adults is associated with modifications of systemic and liver hemodynamics, whereas little is known about the pediatric population. The aim of this work was to investigate whether alterations of hepatic and systemic hemodynamics were correlated with cirrhosis severity in children. The impact of hemodynamic findings on surgical management in pediatric living donor liver transplantation (LT) was evaluated. Liver and systemic hemodynamics were studied prospectively in 52 children (median age, 1 year; 33 with biliary atresia [BA]). The hemodynamics of native liver were studied preoperatively by Doppler ultrasound and intraoperatively using invasive flowmetry. Portosystemic gradient was invasively measured. Systemic hemodynamics were studied preoperatively by Doppler transthoracic echocardiography and intraoperatively by using transpulmonary thermodilution. Hemodynamic parameters were correlated with Pediatric End-Stage Liver Disease (PELD) score and the histological degree of fibrosis (collagen proportionate area [CPA]). Cirrhosis was associated with a 60% reduction of pretransplant total liver flow (n = 46; median, 36 mL/minute/100 g of liver) compared with noncirrhotic livers (n = 6; median, 86 mL/minute/100 g; P = 0.002). Total blood flow into the native liver was negatively correlated with PELD (P < 0.001) and liver CPA (P = 0.005). Median portosystemic gradient was 14.5 mm Hg in children with cirrhosis and positively correlated with PELD (P < 0.001). Portal vein (PV) hypoplasia was observed mainly in children with BA (P = 0.02). Systemic hemodynamics were not altered in our children with cirrhosis. Twenty-one children met the intraoperative criteria for PV reconstruction using a portoplasty technique during the LT procedure and had a smaller PV diameter at pretransplant Doppler ultrasound (median = 3.4 mm; P < 0.001). Cirrhosis in children appears also as a hemodynamic disease of the liver, correlated with cirrhosis severity. Surgical technique for PV reconstruction during LT was adapted accordingly. Liver Transplantation 23 1440-1450 2017 AASLD.

American College of Critical Care Medicine Clinical Practice Parameters for Hemodynamic Support of Pediatric and Neonatal Septic Shock

OBJECTIVES

The American College of Critical Care Medicine provided 2002 and 2007 guidelines for hemodynamic support of newborn and pediatric septic shock. Provide the 2014 update of the 2007 American College of Critical Care Medicine "Clinical Guidelines for Hemodynamic Support of Neonates and Children with Septic Shock."

DESIGN

Society of Critical Care Medicine members were identified from general solicitation at Society of Critical Care Medicine Educational and Scientific Symposia (2006-2014). The PubMed/Medline/Embase literature (2006-14) was searched by the Society of Critical Care Medicine librarian using the keywords: sepsis, septicemia, septic shock, endotoxemia, persistent pulmonary hypertension, nitric oxide, extracorporeal membrane oxygenation, and American College of Critical Care Medicine guidelines in the newborn and pediatric age groups.

MEASUREMENTS AND MAIN RESULTS

The 2002 and 2007 guidelines were widely disseminated, translated into Spanish and Portuguese, and incorporated into Society of Critical Care Medicine and American Heart Association/Pediatric Advanced Life Support sanctioned recommendations. The review of new literature highlights two tertiary pediatric centers that implemented quality improvement initiatives to improve early septic shock recognition and first-hour compliance to these guidelines. Improved compliance reduced hospital mortality from 4% to 2%. Analysis of Global Sepsis Initiative data in resource rich developed and developing nations further showed improved hospital mortality with compliance to first-hour and stabilization guideline recommendations.

CONCLUSIONS

The major new recommendation in the 2014 update is consideration of institution-specific use of 1) a "recognition bundle" containing a trigger tool for rapid identification of patients with septic shock, 2) a "resuscitation and stabilization bundle" to help adherence to best practice principles, and 3) a "performance bundle" to identify and overcome perceived barriers to the pursuit of best practice principles.

Hemodynamic Monitoring in the Acute Management of Pediatric Heart Failure

One of the basic tenets of cardiac critical care is to ensure adequate tissue oxygenation. As with other critical illness such as trauma and acute myocardial infarction studies have demonstrated that making the right diagnosis at the right time improves outcomes. The same is true for the management of patients at risk for or in a state of shock. In order to optimize outcomes an accurate and timely assessment of cardiac function, cardiac output and tissue oxygenation must be made. This review discusses the limitations of the standard assessment of cardiovascular function, and adjunctive monitoring modalities that may be used to enhance the accuracy and timely implementation of therapeutic strategies to improve tissue oxygenation.

Comparison of PulsioFlex® uncalibrated pulse contour method and a modified Fick principle with transpulmonary thermodilution measurements in critically ill patients

Monitoring of cardiac index (CI) by uncalibrated pulse contour (PC) methods has been shown to be inaccurate in critically ill patients. We tested accuracy and trending of a new pulse contour method and a modified Fick method using central venous oxygen saturation. We studied 21 critically ill and mechanically ventilated patients (age 20-86 years) monitored by PC (PulsioFlex®) and transpulmonary thermodilution (TPTD, PiCCO2®) as reference. At baseline, reference and PC-derived CI (CIPC) were recorded and CI obtained by Fick's method (FM, CIFICK). After four hours, measurements were performed analogously for trending analysis. CI are given in l/min/m2 as mean±standard deviation. At baseline CITPTD was 3.7±0.7, CIPC 3.8±0.7 and CIFICK 5.2±1.8. After 4 hours, CITPTD was 3.5±0.6, CIPC 3.8±1.2 and CIFICK 4.8±1.7. Mean bias for PC at baseline was -0.1 (limits of agreement [LOA] -1.4 to 1.2) and -0.4 (LOA -2.6 to 1.9) after four hours. Percentage errors (PE) were 34% and 60% respectively. FM revealed a bias of -1.5 (LOA -4.8 to 1.8, PE 74%) at baseline and -1.5 (LOA -4.5 to 1.4, PE 68%) at four hours. With an exclusion window of 10% of mean cardiac index, trending analysis by polar plots showed an angular bias of 5° (radial LOA±57°) for PC and 16° (radial LOA±51°) for FM. Although PC values at baseline were marginally acceptable, both methods fail to yield clinically acceptable absolute values. Likewise, trending ability is not adequate for both methods to be used in critically ill patients.

Hemodynamic Monitoring

OBJECTIVES

In this review, we discuss hemodynamic monitoring modalities, including their application, the interpretation of data, limitations, and impact on outcomes.

DATA SOURCE

MEDLINE, PubMed.

CONCLUSIONS

One of the tenets of critical care medicine is to ensure adequate tissue oxygenation. This assessment must be timely and accurate to optimize outcomes. The clinical assessment of cardiac function, cardiac output, and tissue oxygenation based on the physical examination and standard hemodynamic variables, although an indispensable part of this exercise, has significant limitations. The use of adjunctive hemodynamic monitoring modalities provides a much more objective, accurate, and timely assessment of the patient's hemodynamic profile and is invaluable for assessing the patient's clinical status, clinical trajectory, and response to interventions.

Minimally invasive or noninvasive cardiac output measurement: an update

Although cardiac output (CO) by pulmonary artery catheterization (PAC) has been an important guideline in clinical management for more than four decades, some studies have questioned the clinical efficacy of CO in certain patient populations. Further, the use of CO by PAC has been linked to numerous complications including dysrhythmia, infection, rupture of pulmonary artery, injury to adjacent arteries, embolization, pulmonary infarction, cardiac valvular damage, pericardial effusion, and intracardiac catheter knotting. The use of PAC has been steadily declining over the past two decades. Minimally invasive and noninvasive CO monitoring have been studied in the past two decades with some evidence of efficacy. Several different devices based on pulse contour analysis are available currently, including the uncalibrated FloTrac/Vigileo system and the calibrated PiCCO and LiDCO systems. The pressure-recording analytical method (PRAM) system requires only an arterial line and is commercially available as the MostCare system. Transesophageal echocardiography (TEE) can measure CO by non-Doppler- or Doppler-based methods. The partial CO2 rebreathing technique, another method to measure CO, is marketed by Novametrix Medical Systems as the NICO system. Thoracic electrical bioimpedance (TEB) and electric bioreactance (EB) are totally noninvasive CO monitoring. Nexfin HD and the newer ClearSight systems are examples of noninvasive CO monitoring devices currently being marketed by Edwards Lifesciences. The developing focus in CO monitoring devices appears to be shifting to tissue perfusion and microcirculatory flow and aimed more at markers that indicate the effectiveness of circulatory and microcirculatory resuscitations.

Comparison of stroke volumes assessed by three-dimensional echocardiography and transpulmonary thermodilution in a pediatric animal model

To compare stroke volumes (SV) in small hearts assessed by real-time three-dimensional echocardiography (3DE) with SV measured by transpulmonary thermodilution (TPTD) and continuous pulse contour analysis (PC) under various hemodynamic conditions. In thirteen anesthetized piglets (range 3.6-7.1 kg) SV were measured by 3DE, TPTD and PC at baseline and during phenylephrine and esmolol administration. 3DE and TPTD measurements were done successively while SV calculated by PC was documented at the time of 3DE. 3DE and TPTD showed a good correlation (r² = 0.74) and a bias of -1.3 ml (limits of agreement -4.1 to 1.5 ml). While TPTD measured higher SV than 3DE, both methods tracked SV changes with a concordance rate of 91 %. PC and 3DE showed a lower correlation coefficient of r² = 0.57 and a bias of -2.1 ml (limits of agreement -5.9 to 1.8 ml). Inter- and intra-observer variability of SV measured by 3DE was good with a mean bias <5 %. SV_3DE showed a small variance and tracked acute small changes in SV in acceptable concordance with TPTD. PC measured SV with a higher variance and mean difference compared to 3DE. In an experimental setting 3DE has the possibility to offer non-invasive assessments of ventricular volumes volume changes. To determine whether 3DE could be used for SV assessment in a clinical routine our results need confirmation in a clinical setting.

Experts' recommendations for the management of cardiogenic shock in children

Cardiogenic shock which corresponds to an acute state of circulatory failure due to impairment of myocardial contractility is a very rare disease in children, even more than in adults. To date, no international recommendations regarding its management in critically ill children are available. An experts’ recommendations in adult population have recently been made (Levy et al. Ann Intensive Care 5(1):52, 2015; Levy et al. Ann Intensive Care 5(1):26, 2015). We present herein recommendations for the management of cardiogenic shock in children, developed with the grading of recommendations’ assessment, development, and evaluation system by an expert group of the Groupe Francophone de Réanimation et Urgences Pédiatriques (French Group for Pediatric Intensive Care and Emergencies). The recommendations cover four major fields of application such as: recognition of early signs of shock and the patient pathway, management principles and therapeutic goals, monitoring hemodynamic and biological variables, and circulatory support (indications, techniques, organization, and transfer criteria). Major principle care for children with cardiogenic shock is primarily based on clinical and echocardiographic assessment. There are few drugs reported as effective in childhood in the medical literature. The use of circulatory support should be facilitated in terms of organization and reflected in the centers that support these children. Children with cardiogenic shock are vulnerable and should be followed regularly by intensivist cardiologists and pediatricians. The experts emphasize the multidisciplinary nature of management of children with cardiogenic shock and the importance of effective communication between emergency medical assistance teams (SAMU), mobile pediatric emergency units (SMUR), pediatric emergency departments, pediatric cardiology and cardiac surgery departments, and pediatric intensive care units.

Comparison of cardiac output measurements using transpulmonary thermodilution and conventional thermodilution techniques in anaesthetized dogs with fluid overload

OBJECTIVE

To evaluate the agreement between cardiac output (CO) values obtained using a transpulmonary thermodilution technique (TPTDCO) and conventional thermodilution technique (TDCO) in anaesthetized dogs with fluid overload.

STUDY DESIGN

Prospective experimental study.

ANIMALS

Six healthy Beagle dogs aged 7-8 years.

METHODS

Dogs were anaesthetized with sevoflurane in oxygen, and catheters were inserted for TPTDCO and TDCO measurement. After instrumentation, baseline CO was measured using each technique at a central venous pressure (CVP) of 3-7 mmHg. Dogs were subsequently administered lactated Ringer's solution and 6% hydroxyethyl starch to induce fluid overload. CO measurements were obtained using each technique at CVP values of 8-12 mmHg, 13-17 mmHg, 18-22 mmHg and 23-27 mmHg. Agreements between CO measurements obtained with the respective techniques were analysed using Dunnett's test, Pearson's correlation coefficient and Bland-Altman analysis.

RESULTS

Thirty pairs of CO values were obtained, ranging from 1.45 L minute(-1) to 4.69 L minute(-1) for TPTDCO and from 1.30 L minute(-1) to 4.61 L minute(-1) for TDCO. TPTDCO and TDCO values correlated strongly (r(2)  = 0.915, p < 0.001). The bias and mean relative bias between TPTDCO and TDCO were 0.26 ± 0.30 L minute(-1) (limits of agreement - 0.29 to 0.81 L minute(-1) ) and 9.7%, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

TPTDCO and TDCO measurements obtained in anaesthetized dogs during fluid overload exhibited good agreement. Accordingly, transpulmonary thermodilution provides an accurate measurement of CO in dogs with fluid overload.

Hemodynamic volumetry using transpulmonary ultrasound dilution (TPUD) technology in a neonatal animal model

To analyze changes in cardiac output and hemodynamic volumes using transpulmonary ultrasound dilution (TPUD) in a neonatal animal model under different hemodynamic conditions. 7 lambs (3.5-8.3 kg) under general anesthesia received arterial and central venous catheters. A Gore-Tex(®) shunt was surgically inserted between the descending aorta and the left pulmonary artery to mimic a patent ductus arteriosus. After shunt opening and closure, induced hemorrhagic hypotension (by repetitive blood withdrawals) and repetitive volume challenges, the following parameters were assessed using TPUD: cardiac output, active circulating volume index (ACVI), central blood volume index (CBVI) and total end-diastolic volume index (TEDVI). 27 measurement sessions were analyzed. After shunt opening, there was a significant increase in TEDVI and a significant decrease in cardiac output with minimal change in CBVI and ACVI. With shunt closure, these results reversed. After progressive hemorrhage, cardiac output and all volumes decreased significantly, except for ACVI. Following repetitive volume resuscitation, cardiac output increased and all hemodynamic volumes increased significantly. Correlations between changes in COufp and changes in hemodynamic volumes (ACVI 0.83; CBVI 0.84 and TEDVI 0.78 respectively) were (slightly) better than between changes in COufp and changes in heart rate (0.44) and central venous pressure (0.7). Changes in hemodynamic volumes using TPUD were as expected under different conditions. Hemodynamic volumetry using TPUD might be a promising technique that has the potential to improve the assessment and interpretation of the hemodynamic status in critically ill newborns and children.

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.

Combined Cerebral and Renal Near-Infrared Spectroscopy After Congenital Heart Surgery

The maintenance of an adequate oxygen supply to tissues after congenital heart surgery is essential for good outcomes. The objective of this study was to assess the usefulness of near-infrared spectroscopy (NIRS) for estimating central venous oxygen saturation (ScvO2) using both cerebral and renal measurements, explore its relation with cardiac output measurements and check its ability to detect low cardiac output. A prospective observational pilot study was conducted in patients weighing <10 kg undergoing cardiopulmonary bypass surgery. Spectroscopy probes were placed on the forehead and renal area, and serial cardiac output measurements were obtained by femoral transpulmonary thermodilution over the first 24 h after surgery. In the 15 patients studied, ScvO2 was correlated with cerebral (r = 0.58), renal (r = 0.60) and combined (r = 0.71) measurements. Likewise, the systolic index was correlated with the NIRS signals: cerebral (r = 0.60), renal (r = 0.50) and combined (r = 0.66). Statistically significant differences were found in the NIRS measures registered in the 29 low cardiac output events detected by thermodilution: cerebral: 62 % (59-65) versus 69 % (63-76); renal: 83 % (70-89) versus 89 % (83-95); and combined 64 % (60-69) versus 72 % (67-76). In our series, combined cerebral and renal monitoring was correlated with central venous oxygen saturation and cardiac output; low cardiac output detection associated a different spectroscopy pattern.

Determination of cardiac output by ultrasound dilution technique in infants and children: a validation study against direct Fick principle

BACKGROUND

In critically ill children, monitoring of cardiac output (CO) is essential to guide haemodynamic management and facilitate cardiovascular therapy. The ultrasound dilution technique (UDT), a novel minimally invasive indicator method, was recently introduced to determine CO. We validated UDT against the 'gold standard' reference technique, the direct Fick principle, in infants and children.

METHODS

Twenty-six children (median age: 6 yr 2 months; median weight: 19.2 kg) underwent diagnostic heart catheterization. In each child, CO was determined by the Fick principle using direct measurement of oxygen consumption and invasive oximetry. Consecutively, haemodynamically stable conditions provided; three independent measurements of CO were conducted with UDT. CO values were compared using bias and limits of agreement calculated using the Bland-Altman approach and linear regression analysis for the complete study group and for a subgroup with body weight <20 kg (n=14).

RESULTS

The mean (standard deviation) CO values were 3.76 (1.73) litre min(-1) (range 1.38-6.97) for the direct Fick principle and 3.49 (1.72) litre min(-1) (range 1.31-7.00) for UDT. An excellent correlation (r=0.96) was found between both methods (P<0.0001). The Bland-Altman analysis demonstrated good clinical agreement with a mean bias of 0.26 litre min(-1), limits of agreement of -0.66 and 1.19 litre min(-1), and percentage error of 25.9%. Comparable results were obtained for patients <20 kg (mean bias=0.19 litre min(-1), percentage error=25.5%).

CONCLUSIONS

CO measurements by UDT agree favourably with Fick-derived CO data and both techniques were found to be equivalent and interchangeable. UDT represents a valid and applicable method for repetitive CO determinations in infants and children.

Advances in monitoring and management of shock

Early recognition and treatment of pediatric shock, regardless of cause, decreases mortality and improves outcome. In addition to the conventional parameters (eg, heart rate, systolic blood pressure, urine output, and central venous pressure), biomarkers and noninvasive methods of measuring cardiac output are available to monitor and treat shock. This article emphasizes how fluid resuscitation is the cornerstone of shock resuscitation, although the choice and amount of fluid may vary based on the cause of shock. Other emerging treatments for shock (ie, temperature control, extracorporeal membrane oxygenation/ventricular assist devices) are also discussed.

Changes in cardiac index and blood pressure on positioning children prone for scoliosis surgery

In this prospective observational study we investigated the changes in cardiac index and mean arterial pressure in children when positioned prone for scoliosis correction surgery. Thirty children (ASA 1-2, aged 13-18 years) undergoing primary, idiopathic scoliosis repair were recruited. The cardiac index and mean arterial blood pressure (median (IQR [range])) were 2.7 (2.3-3.1 [1.4-3.7]) l.min(-1).m(-2) and 73 (66-80 [54-91]) mmHg, respectively, at baseline; 2.9 (2.5-3.2 [1.7-4.4]) l.min(-1).m(-2) and 73 (63-81 [51-96]) mmHg following a 5-ml.kg(-1) fluid bolus; and 2.5 (2.2-2.7 [1.4-4.8]) l.min(-1).m(-2) and 69 (62-73 [46-85]) mmHg immediately after turning prone. Turning prone resulted in a median reduction in cardiac index of 0.5 l.min(-1).m(-2) (95% CI 0.3-0.7 l.min(-1).m(-2), p=0.001), or 18.5%, with a large degree of inter-subject variability (+10.3% to -40.9%). The changes in mean arterial blood pressure were not significant. Strategies to predict, prevent and treat decreases in cardiac index need to be developed.

Noninvasive Cardiac Output Monitoring in Paediatric Cardiac Surgery: Correlation between Change in Thoracic Fluid Content and Change in Patient Body Weight

Objective:

Change in thoracic fluid content (TFC) derived via a bioreactance technique with a noninvasive cardiac output monitoring device (NICOM) reportedly shows a good correlation with the amount of fluid removed. The present study prospectively evaluated the utility and clinical application of TFC in the intraoperative fluid management of paediatric patients with congenital heart disease, undergoing cardiac surgery with bioreactance-based noninvasive monitoring.

Methods:

Haemodynamic parameters, patient body weight and parameters derived from the NICOM device (including cardiac output, cardiac index, TFC, percentage change in TFC compared with baseline [TFCd0%] and stroke volume variation) were recorded after anaesthesia induction but before surgical incision, and just before departure from the operating room to the intensive care unit.

Results:

In the 80 paediatric patients included in this study, linear regression analyses demonstrated good correlations between body weight gain and TFCd0%, between body weight gain % and TFCd0%, and between intra -operative fluid balance and TFCd0%.

Conclusion:

TFCd0% may be a useful indicator for intraoperative fluid management in paediatric patients with congenital heart disease, undergoing cardiac surgery.

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.

Disagreement between pulse contour analysis and transpulmonary thermodilution for cardiac output monitoring after routine therapeutic interventions in ICU patients with acute circulatory failure

BACKGROUND AND OBJECTIVE

The present prospective study was aimed at assessing the reliability of the pulse contour method for measuring cardiac output (CO) after different routinely used therapeutic interventions that can influence vascular compliance and systemic vascular resistances in ICU patients (fluid challenges, changes in norepinephrine or dobutamine infusion rates and changes in ventilatory settings).

METHODS

In ICU patients requiring CO monitoring, transpulmonary thermodilution CO (COTD) and pulse contour CO (COPC) were measured with a PiCCO device after therapeutic manoeuvre-free periods (≤ and >1 h) and after therapeutic interventions without recalibration.

RESULTS

Three hundred fifty-two sets of CO measurement pairs in 63 ICU patients were performed. The biases (and percentage errors) between COPC and COTD for the overall paired measurement, therapeutic manoeuvre-free periods and therapeutic manoeuvres were 0.20 ± 1.09 (33%), -0.01 ± 0.93 (29%) and 0.37 ± 1.18 (34%), respectively. The percentage errors were 36 and 39% for fluid challenges and changes in norepinephrine infusion rate, respectively.

CONCLUSION

In ICU patients requiring therapeutic interventions, COPC is frequently in disagreement with COTD.

[Reliability of the pulse contour analysis for cardiac output measurement for assessing the fluid responsiveness]

BACKGROUND

The cardiac output (CO) is classically measured in intensive care unit patients. pulse contour (PC) method allows monitoring of CO.

OBJECTIVE

The aim of the present study was to assess the ability of PC to assess the fluid responsiveness defined as an increase in CO more than or equal to 15% after 500 mL hydroxyethyl starch over 20 minutes.

PATIENTS AND METHODS

In this observational prospective study, patients in shock in whom a PC method was inserted were included. CO was measure using the PC and thermodilution methods before and after a fluid challenge indicated by the physician. The correlation coefficient was measured, the diagram of Bland and Altman was built and the percentage of error (Critchley and Critchley method) was calculated. The ability of PC to diagnose fluid responsiveness was assessed using a receiver operating characteristics (ROC) curve.

RESULTS

Sixty-two fluid challenges were performed in 37 included patients. After fluid challenge, r(2) was 0.05 (P<0.01), the bias between PC and thermodilution was 0.3 ± 1.2L/min and the percentage of error was 36%. The area of the ROC curve was 0.601 [0.468-0.723].

CONCLUSION

In ICU patients with shock, PC cannot replace thermodilution to diagnose fluid responsiveness.

Precision of the transpulmonary thermodilution measurements

Introduction

We wanted to determine the number of cold bolus injections that are necessary for achieving an acceptable level of precision for measuring cardiac index (CI), indexed global end-diastolic volume (GEDVi) and indexed extravascular lung water (EVLWi) by transpulmonary thermodilution.

Methods

We included 91 hemodynamically stable patients (age 59 (25% to 75% interquartile range: 39 to 79) years, simplified acute physiologic score (SAPS)II 59 (53 to 65), 56% under norepinephrine) who were monitored by a PiCCO2 device. We performed five successive cold saline (15 mL, 6°C) injections and recorded the measurements of CI, GEDVi and EVLWi.

Results

Considering five boluses, the coefficient of variation (CV, calculated as standard deviation divided by the mean of the five measurements) was 7 (5 to 11)%, 7 (5 to 12)% and 7 (6 to 12)% for CI, GEDVi and EVLWi, respectively. If the results of two bolus injections were averaged, the precision (2 × CV/√ number of boluses) was 10 (7 to 15)%, 10 (7 to 17)% and 8 (7 to 14)% for CI, GEDVi and EVLWi, respectively. If the results of three bolus injections were averaged, the precision dropped below 10%, that is, the cut-off that is generally considered as acceptable (8 (6 to 12)%, 8 (6 to 14)% and 8 (7 to 14)% for CI, GEDVi and EVLWi, respectively). If two injections were performed, the least significant change, that is, the minimal change in value that could be trusted to be significant, was 14 (10 to 21)%, 14 (10 to 24)% and 14 (11 to 23)% for CI, GEDVi and EVLWi, respectively. If three injections were performed, the least significant change was 12 (8 to 17)%, 12 (8 to 19)% and 12 (9 to 19)% for CI, GEDVi and EVLWi, respectively, that is, below the 15% cut-off that is usually considered as clinically relevant.

Conclusions

These results support the injection of at least three cold boluses for obtaining an acceptable precision when transpulmonary thermodilution is used for measuring CI, GEDVi and EVLWi.

Assessing the left ventricular systolic function at the bedside: the role of transpulmonary thermodilution-derived indices

Evaluating the systolic function of the left ventricle (LV) is important in the hemodynamic management of the critically ill patients with circulatory failure. Echocardiography is considered the standard monitor for estimating the LV function at the bedside in the intensive care unit. However, it requires a trained operator and is not a real-time monitoring tool. For monitoring of the systolic function, the pulmonary artery catheter has been the gold standard for a long time. However, now there are alternatives to this device, with transpulmonary thermodilution being one of them. This paper provides an overview of the usefulness of the transpulmonary thermodilution-derived indices for assessing systolic function at the bedside.

Hemodynamic monitoring by transpulmonary thermodilution and pulse contour analysis in critically ill children

OBJECTIVES

To summarize the physiologic principles underlying the hemodynamic monitoring using the PiCCO device (Pulsion, Munich, Germany) incorporating the transpulmonary thermodilution technique, the pulse contour cardiac output, and estimation of the arterial pressure variation method. Analysis and review of the current literature.

DESIGN

A MEDLINE-based literature search using the key words transpulmonary thermodilution, pulse contour analysis, cardiac output, animal models, and child.

MEASUREMENTS AND MAIN RESULTS

The bias and precision of cardiac output measured by transpulmonary thermodilution are reliable. The reproducibility for repeated measurements is approximately 5% and the percentage error is approximately 15%. Transpulmonary thermodilution may adequately track changes in cardiac output in animals submitted to hypovolemic conditions and during volume loading. Conversely, data from experimental and clinical studies suggest that continuous monitoring of cardiac output using pulse contour analysis requires careful interpretation because periodic recalibration with transpulmonary thermodilution is necessary. Transpulmonary thermodilution-derived static indicator of cardiac preload (global end-diastolic volume, intrathoracic blood volume) may be more sensitive than conventional measurements of vascular filling pressure. However, the value of stroke volume variation or pulse pressure variation have not been evaluated in pediatric patients. Further studies are needed to determine whether theoretical assumptions underlying the measurement of extravascular lung water are valid in children.

CONCLUSIONS

The PiCCO device may be a useful adjunct for hemodynamic monitoring in critically ill children. Further studies are needed to clarify the reliability and clinical value of pulse contour method and extravascular lung water measurement.

Emerging technologies

Hemodynamic monitoring in critically ill patients has been considered part of the standard of care in managing patients with shock and/or acute lung injury, but outcome benefit, particularly in pediatric patients, has been questioned. There is difficulty in validating the reliability of monitoring devices, especially since this validation requires comparison to the pulmonary artery catheter, which has its own problems as a measurement tool. Interpretation of the available evidence reveals advantages and disadvantages of the available hemodynamic monitoring devices.

Cardiac output can be measured with the transpulmonary thermodilution method in a paediatric animal model with a left-to-right shunt

BACKGROUND

The transpulmonary thermodilution (TPTD) technique for measuring cardiac output (CO) has never been validated in the presence of a left-to-right shunt.

METHODS

In this experimental, paediatric animal model, nine lambs with a surgically constructed aorta-pulmonary left-to-right shunt were studied under various haemodynamic conditions. CO was measured with closed and open shunt using the TPTD technique (CO(TPTD)) with central venous injections of ice-cold saline. An ultrasound transit time perivascular flow probe around the main pulmonary artery served as the standard reference measurement (CO(MPA)).

RESULTS

Seven lambs were eligible for further analysis. Mean (sd) weight was 6.6 (1.6) kg. The mean CO(MPA) was 1.21 litre min(-1) (range 0.61-2.06 l min(-1)) with closed shunt and 0.93 litre min(-1) (range 0.48-1.45 litre min(-1)) with open shunt. The open shunt resulted in a mean Q(p)/Q(s) ratio of 1.8 (range 1.6-2.4). The bias between the two CO methods was 0.17 litre min(-1) [limits of agreement (LOA) of 0.27 litre min(-1)] with closed shunt and 0.14 litre min(-1) (LOA of 0.32 litre min(-1)) with open shunt. The percentage errors were 22% with closed shunt and 34% with open shunt. The correlation (r) between the two methods was 0.93 (P<0.001) with closed shunt and 0.86 (P<0.001) with open shunt. The correlation (r) between the two methods in tracking changes in CO (ΔCO) during the whole experiment was 0.94 (P<0.0001).

CONCLUSIONS

The TPTD technique is a feasible method of measuring CO in paediatric animals with a left-to-right shunt.

Methods in pharmacology: measurement of cardiac output

Many methods of cardiac output measurement have been developed, but the number of methods useful for human pharmacological studies is limited. The 'holy grail' for the measurement of cardiac output would be a method that is accurate, precise, operator independent, fast responding, non-invasive, continuous, easy to use, cheap and safe. This method does not exist today. In this review on cardiac output methods used in pharmacology, the Fick principle, indicator dilution techniques, arterial pulse contour analysis, ultrasound and bio-impedance are reviewed.

Measurement of cardiac output in children by bioreactance

The objective of this study was to evaluate a new bioreactance method for noninvasive cardiac output (CO) measurement (NICOM) in children. Ten patients between 1 and 144 months of age and with no hemodynamic disturbances were studied. Using bioreactance, heart rate (HR), mean arterial pressure (MAP), and cardiac index (CI) measurements were made every 6-8 h. CI was 2.4 ± 1.03 l/min/1.73 m(2) (range 1-4.9 l/min/1.73 m(2)); There were significant correlations between CI and age (r = 0.50, P = 0.003), weight (r = 0.66, P < 0.001), and MAP (r = 0.369, P = 0.037). Significant differences in CI (P < 0.001) were detected between children weighing <10 kg (1.9 ± 0.73 l/min/1.73 m(2); range 1-3.2), 10-20 kg (2.07 ± 0.7 l/min/1.73 m(2); range 1-3.6), and >20 kg (3.7 ± 0.8 l/min/1.73 m(2); range 2.4-4.9). We conclude that the CI measured by bioreactance in children varies with the age and weight of the patients and is lower than the normal range in a large percentage of measurements. These data suggest that this method is not useful for evaluating CI in small children.

Changes in pulse pressure following fluid loading: a comparison between aortic root (non-invasive tonometry) and femoral artery (invasive recordings)

PURPOSE

To document the relationship between stroke volume (SV) and pulse pressure (PP) recorded at the femoral and aortic sites during volume expansion (VE) in patients in shock. We hypothesized that non-invasively estimated aortic PP would exhibit the same ability as PP recorded invasively at the femoral level to track SV changes.

METHODS

Included in this prospective study were 56 ICU patients needing VE. Femoral PP (indwelling catheter), aortic PP (tonometry) and cardiac output (thermodilution) were recorded before and after VE. Responders were defined as patients who showed an increase in SV of ≥15% after VE.

RESULTS

Of the 56 included patients in shock, 39 (age 57 ± 14 years, SAPS II 46 ± 18) completed the study. At both sites, PP increased after VE in responders (n=17, mean SV increase 30 ± 15%) but not in non-responders. In the overall population, there was a positive relationship between VE-induced changes in SV and in PP at the femoral (r=0.60, p<0.001) and aortic (r=0.52, p<0.001) sites. Increases in femoral PP of ≥9% indicated SV increases of ≥15% with 82% sensitivity and 95% specificity. Increases in aortic PP of ≥4.5% indicated SV increases of ≥15% with 76% sensitivity and 82% specificity. Areas under the ROC curves indicated that aortic PP was not different from femoral PP for tracking changes in SV.

CONCLUSION

The ability of non-invasively estimated aortic PP to track fluid response was the same as that of invasively recorded femoral PP. This may have implications for non-invasive haemodynamic monitoring.

Transpulmonary thermodilution in neonates undergoing arterial switch surgery

Measurement of the global end-diastolic volume index (GEDI) by transpulmonary thermodilution (TPTD) has become a useful technique for measuring preload in adults. This study aimed to investigate the hemodynamic changes in neonates during the postoperative period after arterial switch surgery. Over a 13-month period, the postoperative data of 12 neonates with transposition of the great arteries were retrospectively investigated. Arterial and central venous blood pressures were monitored, Cardiac index (CI), stroke volume index (SVI), systemic vascular resistance index (SVRI), GEDI, and extravascular lung water index (ELWI) were measured by thermodilution. The CI was significantly correlated with the SVRI only in the closed chest condition (r = -0.92; P < 0.001). The CI and SVI values were significantly lower and the ELWI and SVRI values significantly higher in both the open and closed chest conditions than the postextubation values. The relationship between change in GEDI and change in CI was stronger in the open chest condition (r = 0.93; P < 0.006) than in the closed chest condition (r = 0.75; P = 0.055). However, the latter just missed statistical significance. According to the findings, TPTD seems to be a useful tool for assessing cardiac function after neonatal arterial switch surgery. Establishment of normal values will be essential for proper guidance of therapy for this population using volumetric parameters.

Experimental validation of cardiac index measurement using transpulmonary thermodilution technique in neonatal total liquid ventilation

This study aimed to assess the precision and the interchangeability of cardiac index measurement by transpulmonary thermodilution (TPTD) and pulmonary thermodilution (PTD) devices on a neonatal animal model of acute respiratory distress syndrome under total liquid ventilation (TLV) and conventional mechanical ventilation (CMV). After acute respiratory distress induction by tracheal instillation of hydrochloric acid, transpulmonary (CI(TPTD)) and pulmonary (CI(PTD)) cardiac index were simultaneously measured every 30 minutes for a 240-minute experiment. Reproducibility of both thermodilution techniques was very good to excellent in both groups of ventilation with intrainstrument intraclass correlation coefficient >0.60. Disagreement was found between TPTD and PTD in TLV and CMV. Bland-Altman analysis revealed mean biases of 0.98 L/min/m² (22.8%) with limits of agreement of -1.33 to 3.25 L/min/m² in CMV and 1.28 L/min/m² (17.3%) with limits of agreement of -1.17 to 3.72 L/min/m² in TLV. Bias between TPTD and PTD was not statistically different in TLV than in CMV (p = 0.11). Transpulmonary thermodilution and PTD remained precise but not interchangeable techniques under TLV as well as CMV. Because TLV does not bring additional bias between both thermodilution techniques, we advocate the use of the less-invasive TPTD under TLV as currently recommended in CMV.