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

Bilateral remote ischemic conditioning in children: A two-center, double-blind, randomized controlled trial in young children undergoing cardiac surgery

Objective

The study objective was to determine whether adequately delivered bilateral remote ischemic preconditioning is cardioprotective in young children undergoing surgery for 2 common congenital heart defects with or without cyanosis.

Methods

We performed a prospective, double-blind, randomized controlled trial at 2 centers in the United Kingdom. Children aged 3 to 36 months undergoing tetralogy of Fallot repair or ventricular septal defect closure were randomized 1:1 to receive bilateral preconditioning or sham intervention. Participants were followed up until hospital discharge or 30 days. The primary outcome was area under the curve for high-sensitivity troponin-T in the first 24 hours after surgery, analyzed by intention-to-treat. Right atrial biopsies were obtained in selected participants.

Results

Between October 2016 and December 2020, 120 eligible children were randomized to receive bilateral preconditioning (n = 60) or sham intervention (n = 60). The primary outcome, area under the curve for high-sensitivity troponin-T, was higher in the preconditioning group (mean: 70.0 ± 50.9 μg/L/h, n = 56) than in controls (mean: 55.6 ± 30.1 μg/L/h, n = 58) (mean difference, 13.2 μg/L/h; 95% CI, 0.5-25.8; P = .04). Subgroup analyses did not show a differential treatment effect by oxygen saturations (pinteraction = .25), but there was evidence of a differential effect by underlying defect (pinteraction = .04). Secondary outcomes and myocardial metabolism, quantified in atrial biopsies, were not different between randomized groups.

Conclusions

Bilateral remote ischemic preconditioning does not attenuate myocardial injury in children undergoing surgical repair for congenital heart defects, and there was evidence of potential harm in unstented tetralogy of Fallot. The routine use of remote ischemic preconditioning cannot be recommended for myocardial protection during pediatric cardiac surgery.

Early-Stage Vasoactive-Inotropic Score and Left Ventricular Ejection Fraction Following Cardiac Surgery: A Comparison of Two Non-invasive Heart Function Monitoring Technologies in the Prognosis of Infants

Objectives: This study aimed to compare the efficiencies of the vasoactive-inotropic score (VIS) and left ventricular ejection fraction (LVEF) in predicting the condition and prognosis of children with congenital heart disease (CHD). Methods: We retrospectively reviewed the medical charts of 104 infants aged < 1 year who underwent cardiac surgery with cardiopulmonary bypass. The maximum and mean postoperative VIS in the first and second 24 hours [VIS (24MAX), VIS (24MEA), VIS (48MAX), and VIS (48MEA)] were recorded. Similarly, LVEF within 24 hours following surgery was monitored. Receiver operator curve (ROC), regression analysis, chi-square test, and t-test were used to analyze both heart function monitoring technologies Results: Receiver operating characteristic analysis revealed that VIS was strongly associated with adverse events and death [area under ROC (AUROC) > 0.90, P = 0.00], with the two most representative scores being VIS (24MEA) and VIS (48MAX), with cut-off points of 19.42 (sensitivity = 100%; specificity = 93.90%) and 22 (sensitivity = 100%; specificity = 93.90%), respectively for death, and 18.02 (sensitivity = 91.70%; specificity = 89.10%) and 17.75 (sensitivity = 91.70%; specificity = 90.20%), respectively for adverse events. Infants with higher VIS had significantly higher mortality, higher incidence of clinical adverse events, higher lactic acid value, and longer mechanical ventilation and ICU stay (P < 0.05). However, LVEF within 24 hours following surgery was not associated with death (AUROC = 0.65, P = 0.33) or adverse events (AUROC = 0.53, P = 0.81). Moreover, there was no significant change in the length of ICU stay, duration of mechanical ventilation, and lactate value (P > 0.05). Conclusions: Vasoactive-inotropic score at an early stage following surgery was significantly associated with the condition and prognosis of infants with congenital heart disease; however, the predictive value of LVEF within 24 hours following surgery was lower.

Novel approaches to capturing and using continuous cardiorespiratory physiological data in hospitalized children

Continuous cardiorespiratory physiological monitoring is a cornerstone of care in hospitalized children. The data generated by monitoring devices coupled with machine learning could transform the way we provide care. This scoping review summarizes existing evidence on novel approaches to continuous cardiorespiratory monitoring in hospitalized children. We aimed to identify opportunities for the development of monitoring technology and the use of machine learning to analyze continuous physiological data to improve the outcomes of hospitalized children. We included original research articles published on or after January 1, 2001, involving novel approaches to collect and use continuous cardiorespiratory physiological data in hospitalized children. OVID Medline, PubMed, and Embase databases were searched. We screened 2909 articles and performed full-text extraction of 105 articles. We identified 58 articles describing novel devices or approaches, which were generally small and single-center. In addition, we identified 47 articles that described the use of continuous physiological data in prediction models, but only 7 integrated multidimensional data (e.g., demographics, laboratory results). We identified three areas for development: (1) further validation of promising novel devices; (2) more studies of models integrating multidimensional data with continuous cardiorespiratory data; and (3) further dissemination, implementation, and validation of prediction models using continuous cardiorespiratory data. IMPACT: We performed a comprehensive scoping review of novel approaches to capture and use continuous cardiorespiratory physiological data for monitoring, diagnosis, providing care, and predicting events in hospitalized infants and children, from novel devices to machine learning-based prediction models. We identified three key areas for future development: (1) further validation of promising novel devices; (2) more studies of models integrating multidimensional data with continuous cardiorespiratory data; and (3) further dissemination, implementation, and validation of prediction models using cardiorespiratory data.

Electrical cardiometry in monitoring percutaneous closure of ductus arteriosus in preterm infants: a case study on five patients

Patent ductus arteriosus closure by catheter-based interventions has become the preferred therapeutic choice. However, hemodynamic perturbances associated to this procedure have not yet been investigated. This study sought to examine the on-site hemodynamic impact caused by the procedure in preterm neonates. In this study, hemodynamic monitoring was obtained in a non-invasive way using electrical cardiometry in five preterm infants who underwent percutaneous patent ductus arteriosus closing at ASST Grande Ospedale Metropolitano Niguarda of Milan. All five infants underwent successful transcatheter closures. All patients experienced immediate hemodynamic changes upon ductal closing. Significative modifications occurred mainly in heart contractility, cardiac output, and stroke volume. In three cases, there was also a significative increase of systemic vascular resistance which persisted for 4 h after closing. While in two cases they spontaneously reduced with an amelioration of cardiac output and contractility, in the other case they were persistently high, associated with an hypertensive crisis and a progressive reduction of cardiac functions. For these reasons, milrinone was started and hemodynamic parameters returned normal in about 3 h, so therapy was discontinued.   Conclusions: Our single-center, prospective, consecutive, case series demonstrated hemodynamic aberrations due to sudden closure of a patent ductus arteriosus. Moreover, post procedural hemodynamic monitoring is important to precociously detect possible cardiac impairment and start an adequate therapy. What is Known: • It has previously suggested a temporarily impairment in cardiac output following patent ductus arteriosus closing. • Little is known about the other hemodynamic parameters during the procedure and how they change in the next hours according to the new hemodynamic status. What is New: • The persistence of increased systemic vascular resistance after percutaneous closure of ductus arteriosus could suggest the occurrence of hemodynamic complications. • Electrical cardiometry was useful to early detect postoperative hemodynamic changes.

Cardiac Output Measurement in Neonates and Children Using Noninvasive Electrical Bioimpedance Compared With Standard Methods: A Systematic Review and Meta-Analysis

OBJECTIVE

To systematically review and meta-analyze the validity of electrical bioimpedance-based noninvasive cardiac output monitoring in pediatrics compared with standard methods such as thermodilution and echocardiography.

DATA SOURCES

Systematic searches were conducted in MEDLINE and EMBASE (2000-2019).

STUDY SELECTION

Method-comparison studies of transthoracic electrical velocimetry or whole body electrical bioimpedance versus standard cardiac output monitoring methods in children (0-18 yr old) were included.

DATA EXTRACTION

Two reviewers independently performed study selection, data extraction, and risk of bias assessment. Mean differences of cardiac output, stroke volume, or cardiac index measurements were pooled using a random-effects model (R Core Team, R Foundation for Statistical Computing, Vienna, Austria, 2019). Bland-Altman statistics assessing agreement between devices and author conclusions about inferiority/noninferiority were extracted.

DATA SYNTHESIS

Twenty-nine of 649 identified studies were included in the qualitative analysis, and 25 studies in the meta-analyses. No significant difference was found between means of cardiac output, stroke volume, and cardiac index measurements, except in exclusively neonatal/infant studies reporting stroke volume (mean difference, 1.00 mL; 95% CI, 0.23-1.77). Median percentage error in child/adolescent studies approached acceptability (percentage error less than or equal to 30%) for cardiac output in L/min (31%; range, 13-158%) and stroke volume in mL (26%; range, 14-27%), but not in neonatal/infant studies (45%; range, 29-53% and 45%; range, 28-70%, respectively). Twenty of 29 studies concluded that transthoracic electrical velocimetry/whole body electrical bioimpedance was noninferior. Transthoracic electrical velocimetry was considered inferior in six of nine studies with heterogeneous congenital heart disease populations.

CONCLUSIONS

The meta-analyses demonstrated no significant difference between means of compared devices (except in neonatal stroke volume studies). The wide range of percentage error reported may be due to heterogeneity of study designs, devices, and populations included. Transthoracic electrical velocimetry/whole body electrical bioimpedance may be acceptable for use in child/adolescent populations, but validity in neonates and congenital heart disease patients remains uncertain. Larger studies in specific clinical contexts with standardized methodologies are required.

Comparison of the effects of shortening rest intervals on the quality of cardiopulmonary resuscitation, physiological parameters, and hemodynamic parameters in well-trained rescuers: Randomized simulation study

BACKGROUND

Cardiopulmonary resuscitation (CPR) performance depends on individual ability and training. Well-trained or professional rescuers can maintain high-quality CPR for longer than laypeople. This study aimed to examine the effects of reducing resting intervals on CPR performance, physiological parameters, and hemodynamic parameters during prolonged CPR in well-trained providers.

METHODS

The study enrolled 90 volunteers from the paramedic students of our institution. They were randomly divided into 3 groups: 2 minutes, 1 minute 45 seconds, and 1 minute 30 seconds rest groups. Each participant performed 5 cycles of chest compression only CPR (2 min/cycle) with different resting intervals according to grouping. CPR quality, physiological variations, and hemodynamic variations were measured for each cycle and compared across the groups.

RESULTS

Of the 90 volunteers, 79 well-trained providers were finally included. The variation of the average chest compression depth across the 5 cycles showed significant differences between the 3 groups: from cycle 1 to 2: 1.2 (3.1) mm, -0.8 (2.0) mm, and -2.0 (3.0) mm in the 2 minutes, 1 minute 45 seconds, and 1 minute 30 seconds groups, respectively (P < .001); from cycle 1 to 3: 0.0 (3.0) mm, -0.7 (3.2) mm, and -2.6 (3.9) mm, respectively (P = .030). However, all 3 groups maintained the recommended rate and chest compression depth for all 5 cycles. Physiological and hemodynamic parameters showed no significant differences between the groups.

CONCLUSIONS

Well-trained providers were able to maintain high-quality CPR despite reducing rest intervals. Adjusting the rest interval may help maintain overall CPR quality in special situations or where layperson rescuers are involved.

Bilateral Remote Ischaemic Conditioning in Children (BRICC) trial: protocol for a two-centre, double-blind, randomised controlled trial in young children undergoing cardiac surgery

INTRODUCTION

Myocardial protection against ischaemic-reperfusion injury is a key determinant of heart function and outcome following cardiac surgery in children. However, with current strategies, myocardial injury occurs routinely following aortic cross-clamping, as demonstrated by the ubiquitous rise in circulating troponin. Remote ischaemic preconditioning, the application of brief, non-lethal cycles of ischaemia and reperfusion to a distant organ or tissue, is a simple, low-risk and readily available technique which may improve myocardial protection. The Bilateral Remote Ischaemic Conditioning in Children (BRICC) trial will assess whether remote ischaemic preconditioning, applied to both lower limbs immediately prior to surgery, reduces myocardial injury in cyanotic and acyanotic young children.

METHODS AND ANALYSIS

The BRICC trial is a two-centre, double-blind, randomised controlled trial recruiting up to 120 young children (age 3 months to 3 years) undergoing primary repair of tetralogy of Fallot or surgical closure of an isolated ventricular septal defect. Participants will be randomised in a 1:1 ratio to either bilateral remote ischaemic preconditioning (3×5 min cycles) or sham immediately prior to surgery, with follow-up until discharge from hospital or 30 days, whichever is sooner. The primary outcome is reduction in area under the time-concentration curve for high-sensitivity (hs) troponin-T release in the first 24 hours after aortic cross-clamp release. Secondary outcome measures include peak hs-troponin-T, vasoactive inotrope score, arterial lactate and central venous oxygen saturations in the first 12 hours, and lengths of stay in the paediatric intensive care unit and the hospital.

ETHICS AND DISSEMINATION

The trial was approved by the West Midlands-Solihull National Health Service Research Ethics Committee (16/WM/0309) on 5 August 2016. Findings will be disseminated to the academic community through peer-reviewed publications and presentation at national and international meetings. Parents will be informed of the results through a newsletter in conjunction with a local charity.

TRIAL REGISTRATION NUMBER

ISRCTN12923441.

Comparison of cardiovascular parameter estimation methods using swine data

In this study, new and existing methods of estimating stroke volume, cardiac output and total peripheral resistance from analysis of the arterial blood pressure waveform were tested over a wide range of conditions. These pulse contour analysis methods (PCMs) were applied to data obtained in six swine during infusion of volume, phenylephrine, dobutamine, isoproterenol, esmolol and nitroglycerine as well as during progressive hemorrhage. Performance of PCMs was compared using true end-ejection pressures as well as estimated end-ejection pressures. There was considerable overlap in the accuracies of the PCMs when using true end-ejection measures. However, for perhaps the most clinically relevant condition, where radial artery pressure is the input, only Wesseling's Corrected Impedance method and the Kouchoukos Correction method achieved statistically superior results. We introduced a method of estimating end-ejection by determining when the systolic pressure dropped to a value equal to the sum of the end-diastolic pressure plus a fraction of the pulse pressure. The most accurate estimation of end-ejection was obtained when that fraction was set to 60% for the central arterial pressure and to 50% for the femoral and radial arterial pressures. When the estimated end-ejection measures were used for the PCMs that depend on end-ejection measures and when radial artery pressure was used as the input, only Wesseling's Corrected Impedance method and the modified Herd's method achieved statistically superior results. This study provides a systematic comparison of multiple PCMs' ability to estimate stroke volume, cardiac output, and total peripheral resistance and introduces a new method of estimating end-systole.

Effect of hemodialysis on impedance cardiography (electrical velocimetry) parameters in children

BACKGROUND

Pediatric hemodialysis (HD) patients have a high incidence of cardiovascular morbidity and mortality. The study aim was to investigate whether impedance cardiography (electrical velocimetry, EV) is suitable as a hemodynamic trend monitoring tool in pediatric patients during HD.

METHODS

Measurements by EV were obtained before, during, and after HD in a prospective single-center pediatric observational study. In total, 54 dialysis cycles in four different pediatric patients with end-stage kidney disease on chronic HD were included. EV parameters analyzed were heart rate (HR), stroke volume (SV), stroke volume index (SI), cardiac output (CO), cardiac index (CI), thoracic fluid content (TFC), index of contractility (ICON), stroke volume variation (SVV), variation of ICON (VIC), R-R interval (TRR), pre-ejection period (PEP), left ventricular ejection time (LVET), and systolic time ration (STR). Systemic vascular resistance index (SVRI) was calculated.

RESULTS

EV did measure significant changes in cardiovascular parameters associated with HD. The following parameters increased after HD: HR (9%), SVV (19%), VIC (33%), PEP (8%), and STR (18%). A decrease after HD was measured in SV (18%), SI (18%), CO (10%), CI (10%), TFC (10%), ICON (7%), TRR (7%), LVET (8%), and LVET (8%). SVRI was not affected by HD. The changes were correlated to ultrafiltration. HD cycles without fluid withdrawal also altered cardiovascular parameters.

CONCLUSIONS

Pediatric HD with and without fluid withdrawal changes hemodynamic EV monitoring parameters. Possibly EV may be useful to optimize HD management in pediatric patients.

Successful management of an infant with hypertensive heart failure associated with Wilms' tumor: a case report

Background

Wilms’ tumor with hyperreninemia may result in critical cardiovascular decompensation. We report a case of severe hypertensive heart failure followed by tumor resection in a 3-month-old infant with Wilms’ tumor.

Case presentation

A 3-month-old girl was admitted to the intensive care unit for Wilms’ tumor with hypertension and hypoxia. Her systolic blood pressure was 110 mmHg, and her SpO₂ was 92%. She presented with severe hypertensive heart failure and received mechanical ventilation and antihypertensive therapy for hypertension and heart failure. An alpha 2-adrenergic receptor agonist was used for sedation as part of her antihypertensive therapy. On hospital day 16, nephrectomy with tumor resection was performed under general anesthesia. Her systolic blood pressure did not vary more than 20 mmHg during surgery due to appropriate preoperative management. Hemodynamic collapse did not occur.

Conclusions

The highlight of this case report is the successful management of an infant with Wilms’ tumor, particularly with respect to preoperative hemodynamic control and sedation.

Accuracy and precision of non-invasive cardiac output monitoring by electrical cardiometry: a systematic review and meta-analysis

Cardiac output monitoring is used in critically ill and high-risk surgical patients. Intermittent pulmonary artery thermodilution and transpulmonary thermodilution, considered the gold standard, are invasive and linked to complications. Therefore, many non-invasive cardiac output devices have been developed and studied. One of those is electrical cardiometry. The results of validation studies are conflicting, which emphasize the need for definitive validation of accuracy and precision. We performed a database search of PubMed, Embase, Web of Science and the Cochrane Library of Clinical Trials to identify studies comparing cardiac output measurement by electrical cardiometry and a reference method. Pooled bias, limits of agreement (LoA) and mean percentage error (MPE) were calculated using a random-effects model. A pooled MPE of less than 30% was considered clinically acceptable. A total of 13 studies in adults (620 patients) and 11 studies in pediatrics (603 patients) were included. For adults, pooled bias was 0.03 L min^-1 [95% CI - 0.23; 0.29], LoA - 2.78 to 2.84 L min^-1 and MPE 48.0%. For pediatrics, pooled bias was - 0.02 L min^-1 [95% CI - 0.09; 0.05], LoA - 1.22 to 1.18 L min^-1 and MPE 42.0%. Inter-study heterogeneity was high for both adults (I² = 93%, p < 0.0001) and pediatrics (I² = 86%, p < 0.0001). Despite the low bias for both adults and pediatrics, the MPE was not clinically acceptable. Electrical cardiometry cannot replace thermodilution and transthoracic echocardiography for the measurement of absolute cardiac output values. Future research should explore it's clinical use and indications.

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.

Non-invasive measurement of cardiac output in children with repaired coarctation of the aorta using electrical cardiometry compared to transthoracic Doppler echocardiography

OBJECTIVE

To evaluate the equivalence of the ICON^® electrical cardiometry (EC) haemodynamic monitor to measure cardiac output (CO) relative to transthoracic Doppler echocardiography (TTE) in paediatric patients with repaired coarctation of the aorta (CoA).

APPROACH

A group of n  =  28 CoA patients and n  =  27 matched controls were enrolled. EC and TTE were performed synchronously on each participant and CO measurements compared using linear regression and Bland-Altman analysis. The CoA group was further subdivided into two groups, with n  =  10 and without n  =  18 increased left ventricular outflow tract velocity (iLVOTv) for comparison.

MAIN RESULTS

CO measurements from EC and TTE in controls showed a strong correlation (R  =  0.80, p  <  0.001) and an acceptable percentage error (PE) of 28.1%. However, combining CoA and control groups revealed a moderate correlation (R  =  0.57, p  <  0.001) and a poor PE (44.2%). We suspected that the CO in a subset of CoA participants with iLVOTv was overestimated by TTE. Excluding the iLVOTv CoA participants improved the correlation (R  =  0.77, p  <  0.001) and resulted in an acceptable PE of 31.2%.

SIGNIFICANCE

CO measurements in paediatric CoA patients in the absence of iLVOTv are clinically equivalent between EC and TTE. The presence of iLVOTv may impact the accuracy of CO measurement by TTE, but not EC.

Oxygen Delivery and Oxygen Consumption in Pediatric Fluid Refractory Septic Shock During the First 42 h of Therapy and Their Relationship to 28-Day Outcome

Background: In septic shock, both oxygen delivery (DO₂) and oxygen consumption (VO₂) are dysfunctional. The current therapeutic regimens are geared to normalize global oxygen delivery (DO₂) to tissues via goal directed therapies but mortality remains high at 10-20%. Methods: We studied cardiac index (CI), systemic vascular resistance index (SVRI), central venous oxygen saturation (ScvO2), central venous pressure (CVP), peripheral oxygen saturation (SpO2), mean blood pressure (MBP), body temperature, blood lactate, base excess and hemoglobin concentration (Hb) in a cohort of children admitted in "fluid-refractory" severe septic shock to pediatric intensive care, over 4.5-years. We calculated their 6 h global oxygen delivery (DO2) and global oxygen consumption (VO2) over the first 42 h and looked at factors associated with VO2/DO2 ratio (i.e., global oxygen extraction, gO2ER) and 28-day mortality. Results: Sixty-two children mean age (SD) 7.19 (5.44) years were studied. Fifty-seven (93%) children were sedated and mechanically ventilated and all received adrenaline or noradrenaline or both and added milrinone in 6 (9.6%). At 28 days, 9 (14.5%) were dead. The global oxygen extraction ratio (gO2ER) was consistently lower amongst the survivors and independently predicted mortality (ROC AUC = 0.75). A lactate level of 4 mmol/l or above, when associated with a concurrent metabolic acidosis predicted mortality with a sensitivity of 100% (95% CI 90.5-100) and a specificity of 67.7% (95% CI 62.2-72.9). A gO2ER of 0.48 or above on admission to the PICU was associated with death with a 66.7% sensitivity (95%CI 29.9-92.5) and 90.5% specificity (95%CI 79.3-96.8). A global O2ER of >0.48 combined with a concurrent blood lactate >4.0 mmol/l at any time within the first 42 h of therapy predicted death with a sensitivity of 63.9% (95% CI, 46.2-79.1) and specificity of 97.8% (95% CI, 95.7-99.0). A radar plot identified MBP-CVP difference, and CI as additional goals of therapy that may offer a survival benefit. Conclusions: Global O2ER of >0.48 with a concurrent blood lactate >4.0 mmol/l in children with metabolic acidosis was an independent factor associated with death in fluid resistant septic shock. Trends of gO2ER seem useful to recognize survivors and non-survivors early in the illness.

Anesthetic considerations for a pediatric patient with Wolf-Hirschhorn syndrome: a case report

Wolf-Hirschhorn syndrome is a rare hereditary disease that results from a 4p chromosome deletion. Patients with this syndrome are characterized by craniofacial dysgenesis, seizures, growth delay, intellectual disability, and congenital heart disease. Although several cases have been reported, very little information is available on anesthetic management for patients with Wolf-Hirschhorn syndrome. We encountered a case requiring anesthetic management for a 2-year-old girl with Wolf-Hirschhorn syndrome. The selection of an appropriately sized tracheal tube and maintaining intraoperatively stable hemodynamics might be critical problems for anesthetic management. In patients with short stature, the tracheal tube size may differ from what may be predicted based on age. The appropriate size ( internal diameter ) of tracheal tubes for children has been investigated. Congenital heart disease is frequently associated with Wolf-Hirschhorn syndrome. Depending on the degree and type of heart disease, careful monitoring of hemodynamics is important.

Impedance cardiography in healthy children and children with congenital heart disease: Improving stroke volume assessment

INTRODUCTION

Stroke volume (SV) and cardiac output are important measures in the clinical evaluation of cardiac patients and are also frequently used in research applications. This study was aimed to improve SV scoring derived from spot-electrode based impedance cardiography (ICG) in a pediatric population of healthy volunteers and patients with a corrected congenital heart defect.

METHODS

128 healthy volunteers and 66 patients participated. First, scoring methods for ambiguous ICG signals were optimized to improve agreement of B- and X-points with aortic valve opening/closure in simultaneously recorded transthoracic echocardiography (TTE). Building on the improved scoring of B- and X-points, the Kubicek equation for SV estimation was optimized by testing the agreement with the simultaneously recorded SV by TTE. Both steps were initially done in a subset of the sample of healthy children and then validated in the remaining subset of healthy children and in a sample of patients.

RESULTS

SV assessment by ICG in healthy children strongly improved (intra class correlation increased from 0.26 to 0.72) after replacing baseline thorax impedance (Z₀) in the Kubicek equation by an equation (7.337-6.208∗dZ/dt_max), where dZ/dt_max is the amplitude of the ICG signal at the C-point. Reliable SV assessment remained more difficult in patients compared to healthy controls.

CONCLUSIONS

After proper adjustment of the Kubicek equation, SV assessed by the use of spot-electrode based ICG is comparable to that obtained from TTE. This approach is highly feasible in a pediatric population and can be used in an ambulatory setting.

Identification of the State of Maximal Hyperemia in the Assessment of Coronary Fractional Flow Reserve Using Non-Invasive Electrical Velocimetry

Previous research revealed that, in patients with coronary pressure-derived fractional flow reserve (FFR) in the 'grey zone' (0.75-0.85), repeated FFR assessments sometimes yield conflicting results. One of the causes of the fluctuations in FFR values around the grey zone may be imprecise identification of the point where maximal hyperemia is achieved. Identification of the state of maximal hyperemia during assessment of FFR can be challenging. This study aimed to determine whether non-invasive electrical velocimetry (EV) can be used to identify the state of maximal hyperemia.Stroke volume (SV), SV variation (SVV), and systemic vascular resistance index (SVRI) were determined by EV in 15 patients who underwent FFR assessment. Time intervals from initiation of adenosine infusion to achieving maximal hyperemia (time^mFRR), as well as to achieving maximal cardiac output (CO), SV, SVV, and SVRI (time^mCO, time^mSV, time^mSVV, and time^mSVRI, respectively), were determined. Time^mCO and time^mSVV were closer to time^mFRR than other values (time^mSVV/time^mFRR versus time^mSVRI/time^mFRR = 1.03 ± 0.2 versus 1.36 ± 0.4, P < 0.05). The maximum of SV was difficult to determine owing to considerable variations, but the maximum of SVV was clearly recognized. Time^mCO and time^mSVV were significantly correlated with time^mFFR, with time^mSVV showing a stronger correlation than time^mSV (time^mSVV: r = 0.92, P < 0.01; time^mCO: r = 0.80, P < 0.01).Maximal SVV is reached close to maximal hyperemia. Monitoring of SVV with non-invasive EV during FFR assessment can help identify the state of maximal hyperemia.

Hemodynamic coherence in critically ill pediatric patients

Differences in physiology and pathophysiology make the treatment of developing, critically ill children particularly challenging as compared to that of adults. Significant differences in the cardiovascular system of neonates and children in size, weight, body proportions, and metabolism should be considered. Hemodynamic monitoring is crucial for early warning of pending deterioration and to guide therapy. Current monitoring is limited to the macrocirculation, but an adequately functioning macrocirculation does not guarantee a well-functioning microcirculation. Research in children revealed loss of hemodynamic coherence, i.e., microcirculatory alterations despite normal systemic hemodynamics. Implementing the framework of hemodynamic coherence in microcirculatory monitoring in children can aid physicians in titrating therapy on both macrocirculatory and microcirculatory effects to assure optimal oxygen delivery. Monitoring the microcirculation at the bedside requires further technical development. Although more research is necessary to validate the concept of hemodynamic coherence in children, the possibilities of applying this concept in children seem promising.

Stroke volume and cardiac output evaluation by electrical cardiometry: accuracy and reference nomograms in hemodynamically stable preterm neonates

OBJECTIVE

To investigate the accuracy of electrical cardiometry (EC) to measure stroke volume (SV) and cardiac output (CO) and to provide gestational age (GA) and birth weight (BW)-based reference data for SV and CO in hemodynamically stable preterm neonates.

STUDY DESIGN

Prospective observational blinded study. Paired measurements of SV and CO on stable preterm infants without any hemodynamic compromise were carried out using EC (SVEC) and echocardiography (SVECHO).

RESULTS

Seventy-nine preterm neonates (mean GA: 31±3.2 weeks) were enrolled. A good correlation was found for SV (r=0.743; P<0.0001) and CO (r=0.7; P<0.0001) measured by EC and echocardiography. These correlations remained significant after adjusting for GA, patent ductus arteriosus and type of respiratory support (SV: St.β=0.48, P<0.0001 and CO: St.β=0.69, P<0.0001). Mean biases (and variabilities) were -1.1 (from 0.7 to -2.9) ml and -0.21 (from 0.15 to -0.55) l min(-1) for SV and CO, respectively. Local regression shows a tendency for EC to overestimate SV and CO especially at higher values (at about >2 ml and >0.4 l min(-1), respectively). Coefficient of variation of SV was 48.9% and 52%, for EC and echocardiography. SV and CO rose with increasing GA and BW following an exponential equation (R(2)>0.8).

CONCLUSION

Measuring SV and CO with EC in hemodynamically stable preterm infants shows good correlation and variability similar to that of echocardiography. A trend to overestimation exists at highest values, but it is unlikely to be clinically significant. Reference GA and BW-based nomograms for SV and CO are provided.

Hemodynamic reference for neonates of different age and weight: a pilot study with electrical cardiometry

OBJECTIVE

Electrical cardiometry (EC) is an impedance-based monitor that provides noninvasive, real-time hemodynamic assessment. However, the reference values for neonates have not been established.

STUDY DESIGN

EC (Aesculon) was applied to hemodynamically stable preterm and term infants. Hemodynamic variables included cardiac output (CO), cardiac index (CI), stroke volume (SV) and heart rate (HR). Their gestational age (GA), weight and body surface area (BSA) were recorded.

RESULTS

A total of 280 neonates were studied. Their GA ranged from 26(5/7) to 41(4/7) weeks, weight 800 to 4420 g and BSA 0.07 to 0.26 m(2). CO was positively correlated to GA, weight and BSA (r=0.681, 0.822, 0.830, respectively; all P<0.001). Using regression analysis, CO was most significantly correlated to BSA. Mean CI was 2.55±0.37 l min(-1) per m(2).

CONCLUSION

Hemodynamic reference by EC is notably distinct among neonates of diverse maturity. CO is most closely correlated to BSA.

Age-related incidence of desaturation events and the cardiac responses on stroke index, cardiac index, and heart rate measured by continuous bioimpedance noninvasive cardiac output monitoring in infants and children undergoing general anesthesia

STUDY OBJECTIVE

To assess the effects of desaturation on stroke index (SI), cardiac index (CI), and heart rate (HR) using the ICON continuous noninvasive cardiac output monitor in children undergoing general anesthesia.

DESIGN

Retrospective analysis of a prospectively collected data set.

SETTING

Pediatric operating rooms in a tertiary academic medical center.

PATIENTS

Children younger than 20 years who experienced desaturation while undergoing general anesthesia.

INTERVENTION

All records were retrospectively searched for desaturation events defined as a recorded Spo2 ≤ 90%. We compared the data from the prior 4 minutes (baseline) with mild, moderate, and severe levels of desaturation.

MEASUREMENTS

The relationship between Spo2 and percent change in SI, CI, and HR from baseline was assessed using a generalized linear model with repeated measures and the least-squares method.

MAIN RESULTS

Data from 446 patients were reviewed; 38 events were eligible for analysis after exclusions. There were significant decreases in SI at all saturation ranges below 95%: -6.5% (P < .001) for 85%-95%, -8.9% (P = .002) for 71%-84%, and -11% (P < .001) for ≤70%. Based on the result from the regression, Spo2 was associated with change in SI with borderline significance (P = .053) but not that of HR and CI. There was a strong relationship to desaturation events with young age (P < .001), particularly infants younger than 6 months.

CONCLUSION

Events associated with desaturation in children under general anesthesia were significantly associated with decreased SI with a greater effect with lower saturation nadirs. It is unclear if other concurrent events could have also contributed to adverse hemodynamic responses during desaturation. In most children, a compensatory increase in HR generally offsets concurrent decreases in CI. It would appear that bradycardia is a late manifestation of hypoxemia.

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.

Hemodynamic alterations recorded by electrical cardiometry during ligation of ductus arteriosus in preterm infants

This is a prospective study using non-invasive electrical cardiometry to measure hemodynamic changes during surgical ligation of patent ductus arteriosus (PDA) in very low birth weight (VLBW, ≤1500 g) infants. The aims of this study were to examine hemodynamic aberration caused by abrupt closure of a ductal shunting and to define factors that affect hemodynamic changes. Simultaneous measurements of heart rate (HR), stroke volume (SV), cardiac output (CO), and systemic vascular resistance (SVR) were collected at ten time points: 1 h prior to anesthesia, at the beginning of anesthesia, starting of surgery, immediately after PDA being ligated, and 1 h followed by 6, 12, 18, 24, and 48 h after the surgery. Thirty infants with gestational age of 27.7 ± 2.0 weeks and birth weight of 929 ± 280 g were studied. Upon sudden termination of ductal shunting, there was a significant decline in CO to 73 % of presurgery baseline. The deterioration in CO was associated with a decreased SV rather than HR. At the same time, there was an increase of SVR following ductal ligation. Magnitude of CO and SV reduction were higher in smaller infants (≤1 kg), and recovery was to a lesser degree in infants with more severe PDA.

CONCLUSION

Reduced stroke volume and elevated vascular resistance contribute to the major hemodynamic aberrations in VLBW infants receiving PDA ligation surgery.

Propofol effect on cerebral oxygenation in children with congenital heart disease

Propofol is a short-acting, intravenously administered hypnotic agent which is used in procedural sedation in children. Propofol is known to decrease systemic vascular resistance, arterial blood pressure and can lead to desaturations and decreased systemic perfusion in children with cardiac shunting. This may result in a reduction in cerebral blood flow and oxygenation. Near-infrared spectroscopy (NIRS) can monitor cerebral tissue oxygenation in the frontal neocortex. The objective of our study was to measure the changes in cerebral oxygen and blood supply after Propofol infusion in children with congenital heart disease. Propofol infusion may reduce cerebral oxygenation in children with congenital heart disease. The study group consisted of 32 children (f:m = 18:14), with median age of 49 (5-112) months and median weight of 15 (5-34) kg. We performed NIRS derived continuous measurement of cerebral oxygenation and cardiac output using Electrical velocimetry for 5 min before and after sedation with Propofol (1-2 mg/kg i.v.) for cardiac catheterization. Simultaneously, non-invasive arterial blood pressure and transcutaneous oxygen saturation were measured. Propofol sedation led to a significant decrease in mean arterial pressure (79 ± 16 vs. 67 ± 12 mmHg) (p = 0.01) and cardiac index (3.2 ± 0.8 vs. 2.9 ± 0.6 ml/min/m(2)) (p = 0.03). In contrast, cerebral tissue oxygenation index, increased significantly from 57 ± 11 to 59 ± 10 % (p < 0.05). Sedation with Propofol increased cerebral tissue oxygenation despite a decrease in cardiac index and arterial blood pressure. This may be caused by a decreased oxygen consumption of the sedated brain with intact cerebral auto-regulation.

Continuous noninvasive cardiac output in children: is this the next generation of operating room monitors? Initial experience in 402 pediatric patients

BACKGROUND

Electrical Cardiometry(™) (EC) estimates cardiac parameters by measuring changes in thoracic electrical bioimpedance during the cardiac cycle. The ICON(®), using four electrocardiogram electrodes (EKG), estimates the maximum rate of change of impedance to peak aortic blood acceleration (based on the premise that red blood cells change from random orientation during diastole (high impedance) to an aligned state during systole (low impedance)).

OBJECTIVE

To determine whether continuous cardiac output (CO) data provide additional information to current anesthesia monitors that is useful to practitioners.

METHODS

After IRB approval and verbal consent, 402 children were enrolled. Data were uploaded to our anesthesia record at one-minute intervals. Ten-second measurements (averaged over the previous 20 heart beats) were downloaded to separate files for later comparison with routine OR monitors.

RESULTS

Data from 374 were in the final cohort (loss of signal or improper lead placement); 292,012 measurements during 58,049 min of anesthesia were made in these children (1 day to 19 years and 1 to 107 kg). Four events had a ≥25% reduction in cardiac index at least 1 min before a clinically important change in other monitored parameters; 18 events in 14 children confirmed manifestations of other hemodynamic measures; eight events may have represented artifacts because the observed measurements did not seem to fit the clinical parameters of the other monitors; three other events documented decreased stroke index with extreme tachycardia.

CONCLUSIONS

Electrical cardiometry provides real-time cardiovascular information regarding developing hemodynamic events and successfully tracked the rapid response to interventions in children of all sizes. Intervention decisions must be based on the combined data from all monitors and the clinical situation. Our experience suggests that this type of monitor may be an important addition to real-time hemodynamic monitoring.

Comparison of monitoring performance of bioreactance versus esophageal Doppler in pediatric patients

Background and Aims:

Cardiac output (CO) monitoring and goal-directed therapy during major abdominal surgery is currently used to decrease postoperative complications. However, few monitors are currently available for pediatric patients. Nicom^® is a noninvasive CO monitoring technique based on the bioreactance principle (analysis of frequency variations of a delivered oscillating current traversing the thoracic cavity). Nicom^® may be a useful monitor for pediatric patients.

Subjects and Methods:

Pediatric patients undergoing major abdominal surgery under general anesthesia with cardiac monitoring by transesophageal Doppler (TED) were included. Continuously recorded hemodynamic variables obtained from both bioreactance and TED were compared. Data were analyzed using the Bland–Altman method.

Results:

A total of 113 pairs of cardiac index (CI) measurments from 16 patients were analyzed. Mean age was 59 months (95% CI: 42-75) and mean weight was 17 kg (95% CI: 15–20). In the overall population, Bland–Altman analysis revealed a bias of 0.4 L/min/m², precision of 1.55 L/min/m², limits of agreement of −1.1 to 1.9 L/min/m² and a percentage error of 47%. For children weighing >15 kg, results were: Bias 0.51 L/min/m², precision 1.17 L/min/m², limits of agreement −0.64 to 1.66 L/min/m² and percentage error 34%.

Conclusion:

Simultaneous CI estimations made by bioreactance and TED showed high percentage of errors that is not clinically acceptable. Bioreactance cannot be considered suitable for monitoring pediatric patients.

Non-invasive cardiac output measurement in low and very low birth weight infants: a method comparison

BACKGROUND

Cardiac output (CO) measurement in low (LBW) and very low (VLBW) birth weight infants is difficult. Hitherto, sporadical transthoracic echocardiography (TTE) is the only non-invasive measurement method. Electrical velocimetry (EV) has been evaluated as an alternative in normal weight newborns.

OBJECTIVES

The study was designed to evaluate if EV could be interchangeable with TTE even in LBW and VLBW infants.

METHODS

In 28 (17 LBW, 11 VLBW) pre-mature newborns, n = 228 simultaneous TTE (trans-aortic Doppler), and EV measurements (134 LBW, 94 VLBW) of stroke volume (SV) and heart rate (HR) were performed, thereof calculating body weight indexed SV (=SV*) and CO (=CO*) for all patients and the subgroups. Method comparison was performed by Bland-Altman plot, method precision expressed by calculation of the coefficient of variation (CV).

RESULTS

Mean CO* in all patients was 256.4 ± 44.8 (TTE) and 265.3 ± 48.8 (EV) ml/kg/min. Bias and precision were clinically acceptable, limits of agreement within the 30% criterion for method interchangeability (17). According to their different anatomic dimensions and pathophysiology, there were significant differences of SV(*), HR, and CO* for LBW and VLBW infants as well for inotropic treatment and ventilation mode.

CONCLUSION

Extending recent publications on EV/TTE comparison in newborns, this study suggests that EV is also applicable in LWB/VLBW infants as a safe and easy to handle method for continuous CO monitoring in the NICU and PCICU.

Reference values of aortic flow velocity integral in 1193 healthy infants, children, and adolescents to quickly estimate cardiac stroke volume

The aortic velocity time integral (VTI) is an echocardiographic tool used to estimate cardiac output (CO) by multiplying it with the aortic valve (AV) area and heart rate (HR). Inaccurate measurement of AV diameter will lead to squared miscalculation of CO. The aortic VTI itself can serve as a left-ventricular (LV) output parameter. The normal range of aortic VTI in adulthood is relatively stable, compared with childhood, but reference data are lacking. The aim of this study was to establish reference values of VTI in infants, children, and adolescents. A retrospective analysis of 1223 echocardiographic examinations of healthy children (age 0-20 years, body surface area [BSA] 0.11-2.23 m(2)) was performed. Data were correlated with age, BSA, and HR, and age subgroups with normal distribution were determined. Interobserver and intraobserver variability was calculated. Aortic VTI ranged from mean 13.8 cm (10.0-18.4 cm 5-95th percentile) in neonates to 25.1 cm (19.6-32.8 cm 5-95th percentile) in children >17 years of age and had a positive correlation with age (r = 0.685, p < 0.001), BSA (r = 0.645, p < 0.001) and a negative correlation with HR (r = -0.710, p < 0.001). Interobserver and intraobserver variability were excellent (3.9 ± 3.1 and 4.6 ± 3.7 %, respectively). Calculated mean values and percentile charts for the different age groups can serve as reference data to easily judge LV output in patients with or without congenital heart disease without enlargement or dysfunction of the AV.

Plethysmographic variability index (PVI) accuracy in predicting fluid responsiveness in anesthetized children

INTRODUCTION

Plethysmographic Variability Index (PVI) has been shown to accurately predict responsiveness to fluid loads in adults. The goal of this study was to evaluate PVI accuracy when predicting fluid responsiveness during noncardiac surgery in children.

MATERIAL AND METHODS

Children aged 2-10 years scheduled for noncardiac surgery under general anesthesia were included. PVI was assessed concomitantly with stroke volume index (SVI). A response to fluid load was defined by an SVI increase of more than 15%. A 10 ml·kg(-1) normal saline intravenous fluid challenge was administered before surgical incision and after anesthetic induction. After incision, fluid challenges were administered when SVI values decreased by more than 15% or where judged necessary by the anesthesiologist. Statistical analyses include receiving operator characteristics (ROC) analysis and the determination of gray zone method with an error tolerance of 10%.

RESULTS

Fifty-four patients were included, 97 fluid challenges administered and 45 responses recorded. Area under the curve of ROC curves was 0.85 [0.77-0.93] and 0.8 [0.7-0.89] for baseline PVI and SVI values, respectively. Corresponding gray zone limits were [10-17%] and [22-31 ml·m(-2)], respectively. PVI values exhibited different gray zone limits for pre-incision and postincision fluid challenges, whereas SVI values were comparable. PVI value percentages in the gray zone were 34% overall and 44% for challenges performed after surgical incision.

DISCUSSION

This study found both PVI and prechallenge SVI to be accurate when used to predict fluid load response during anesthetized noncardiac surgery in children. However, a third of recorded PVI values were inconclusive.

Cardiac parameters in children recovered from acute illness as measured by electrical cardiometry and comparisons to the literature

Electrical cardiometry (EC) is a non-invasive cardiac output method that can assess cardiac index (CI) and stroke index (SI) but there are no reference values for children per se. The primary aim of this study was to develop reference values for clinical application. The secondary aim was to compare the EC measurements to published values. We performed a prospective observational study in patients (<21 years of age) without structural heart disease who had recovered from an acute illness. EC recordings in children that had normal heart rate and mean arterial blood pressure at discharge were eligible for analysis. The relationship of CI or SI and age in children was performed by regression analysis. Similar analysis was performed comparing measurements by EC to cardiac parameters values compiled from reference sources to assess bias in EC. Eighty-three children (2 weeks-21 years of age) were studied. There was a significant curvilinear relationship between CI or SI and age by EC (F-test, p < 0.05). Regression curves of cardiac parameters reported in the literature using 6 Fick's method, thermodilution, echocardiography and cardiac MRI were the same or higher than (0-19.6 %) values obtained with EC, with higher values being statistically significant (p < 0.05 all). There is a curvilinear relationship of CI or SI and age by EC in normal children. Cardiac parameters reported in the literature using alternative methods are different from those obtained with EC but are within acceptable ranges, with EC biased to underestimate CI. Adjustment of target value is required for EC goal-directed therapies.

New technologies in pediatric anesthesia

This article reviews potential pediatric applications of 3 new technologies. (1) Pulse oximetry-based hemoglobin determination: Hemoglobin determination using spectrophotometric methods recently has been introduced in adults with varied success. This non-invasive and continuous technology may avoid venipuncture and unnecessary transfusion in children undergoing surgery with major blood loss, premature infants undergoing unexpected and complicated emergency surgery, and children with chronic illness. (2) Continuous cardiac output monitoring: In adults, advanced hemodynamic monitoring such as continuous cardiac output monitoring has been associated with better surgical outcomes. Although it remains unknown whether similar results are applicable to children, current technology enables the monitoring of cardiac output non-invasively and continuously in pediatric patients. It may be important to integrate the data about cardiac output with other information to facilitate therapeutic interventions. (3) Anesthesia information management systems: Although perioperative electronic anesthesia information management systems are gaining popularity in operating rooms, their potential functions may not be fully appreciated. With advances in information technology, anesthesia information management systems may facilitate bedside clinical decisions, administrative needs, and research in the perioperative setting.

Changes in cardiac output and stroke volume as measured by non-invasive CO monitoring in infants with RSV bronchiolitis

OBJECTIVES

The primary aim of the study was to determine the changes, if any, in cardiac output (CO) and stroke volume (SV) in normal infants with RSV bronchiolitis. The secondary aim was to determine whether changes in CO (ΔCO) and SV (ΔSV) are associated with changes in respiratory rate (ΔRR).

METHODS

Non-invasive CO recordings were obtained within 24 h of admission and discharge. Changes in CO, SV, and HR measurements were compared using paired t-tests. The effect of fluid boluses during the first 24 h (<60 or ≥60 cc/kg) on CO was assessed by 2 way ANOVA with time and group as main effect. The relationship between ΔRR and ΔCO or ΔSV was assessed by linear regression. Data is presented as Mean ± SEM and mean differences with 95 % confidence interval (p < 0.05 considered significant).

RESULTS

15 infants with RSV bronchiolitis were studied. CO (1.31 ± 0.13 to 1.11 ± 0.11 l/min (0.21 [0.04-0.37]) and SV (9.42 ± 1.10 to 7.75 ± 0.83 ml/beat (1.67 [0.21-3.12]) decreased significantly while HR (142.1 ± 4.0 to 145.2 ± 3.1 beats/min 3.0 [-5.3 to 11.3]) was unchanged. SV (p = 0.02) and CO (p = 0.04) significantly decreased only in the 7 infants that received ≥60 cc/kg. ΔRR correlated significantly with ΔCO (r (2) = 0.28, p = 0.04); but not with ΔSV (r (2) = 0.20, p = 0.09).

CONCLUSIONS

∆CO was related to ΔSV and not Δ HR. The ∆CO and ΔSV were affected by fluid boluses. ΔRR correlated with ΔCO. Non-invasive CO monitoring can trend CO and SV in infants with bronchiolitis during hospitalization.

Electrical velocimetry as a tool for measuring cardiac output in small infants after heart surgery

PURPOSE

Cardiac output (CO), the product of stroke volume (SV) and heart rate, is essential to guarantee organ perfusion, especially in the intensive care setting. As invasive measurement of CO bears the risk of complications there is a need for non-invasive alternatives. We investigated if electrical velocimetry (EV) and transthoracic Doppler (Doppler-TTE) are interchangeable for the non-invasive measurement of SV and able to reflect the post-surgical SV/CO trend.

METHODS

Comparison of SV measurements by EV and Doppler-TTE was performed in 24 newborns after switch operation (n = 240 measurements). Three subgroups of measurements (=periods) were created according to the patients' status in the course of post-surgical CO recovery.

RESULTS

Bland-Altman analysis found acceptable bias and limits of agreement for the interchangeability of the two methods. Mean overall SV was 3.7 ml with a mean overall bias of 0.28 ml (=7.6 %). The mean percentage error of 29 % was acceptable according to the method of Critchley and Critchley. Overall precision expressed by the coefficient of variation (CV) was 6.6 % for SV(TTE) and 4.4 % for SV(EV). SV(TTE) and SV(EV) medians in the three periods were significantly different and documented the post-surgical CO trend.

CONCLUSIONS

EV and Doppler-TTE are interchangeable for estimating SV. EV has the advantages of easy handling and allows continuous measurement.

Non-invasive cardiac output and oxygen delivery measurement in an infant with critical anemia

OBJECTIVE

To assess the combination of a non-invasive blood oxygen content (CaO(2)) monitor and a non-invasive cardiac output (CO) monitor to continuously measure oxygen delivery (DO(2); DO(2) = CaO(2) × CO).

METHODS

DO(2) was assessed during blood transfusions in an infant with acute hemolytic anemia following admission (~48 h). CaO(2) was measured by Pulse Co-Oximetry, which also provides estimates of hemoglobin (Hgb) concentration and percent oxygen saturation. CO was measured by Electrical Velocimetry, which also provides an estimate of stroke volume (SV). Lactate levels, an indirect measure of adequate DO(2), were assessed during the initial 8 h following admission.

RESULTS

Incremental blood transfusions during the first 36 h increased Hgb from 2.7 to 9.5 g/dL during which time heart rate (HR) normalized from 156 to 115 beats/min. Lactate levels decreased from 20 to 0.8 mmol/L in the first 7 h. Non-invasive Hgb and CaO(2) measurements were well correlated with invasive Hgb and CaO(2) measures (r (2) = 0.88; P = 0.019; r (2) = 0.86; P = 0.0074, respectively). CO decreased from 2.47 ± 0.06 to 1.28 ± 0.02 L/min and SV decreased from 15.9 ± 0.4 to 11.1 ± 0.2 mL/beat. Mean arterial blood pressure was stable throughout the admission with systemic vascular resistance increasing from 407.6 ± 15.2 to 887.7 ± 30.1 dynes-s/cm(5). DO(2) was estimated to increase from 120.2 ± 18.9 to 182.4 ± 5.6 mL O(2)/min.

CONCLUSIONS

Non-invasive continuous CO and CaO(2) monitors are shown in this single case to provide continuous DO(2) measurement. The ability to assess DO(2) may improve hemodynamic monitoring during goal directed therapies.

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.

Objective assessment of cardiac output in infants after cardiac surgery

An accurate measurement of cardiac performance in infants after cardiopulmonary bypass has long been considered to be an important part of postoperative management. To be useful in clinical decision making, such measurements should ideally be reproducible, non invasive and accurately reflect tissue perfusion and oxygen delivery. Historically, we have relied on intermittent measurements of cardiac output using indicator dilution methods; and more recently, technologies that use pulse contour analysis, bio-impedance, or Doppler methodology. These all have the same shortcoming, that they provide a number that the information as to whether it provides adequate tissue perfusion. There is increasing emphasis being placed on the measurement of oxygen delivery either by mixed venous oxygen saturation and serum lactate, which are important markers of the adequacy of organ perfusion; and relating this to outcome, the development of organ dysfunction and length of ICU stay.

Pro: NIRS is "standard of care" for postoperative management

Successful postoperative management depends on early detection and correction of circulatory insufficiency. Global cardiac output and oxygen delivery must be adequate and distributed appropriately to meet metabolic demands to prevent the development of multi-organ dysfunction, morbidity, and death. Decreased cardiac output during the postoperative period is common, but circulatory assessment using standard monitoring provides inadequate information to reliably detect low cardiac output syndrome or effectively guide therapy. Goal-directed therapy using invasive estimates of global oxygen supply-demand balance (SvO2) has been shown to improve survival among patients in shock states. Near infrared spectroscopy (NIRS) is a noninvasive assessment of regional oxygen supply-demand balance. Multiple prospective observational studies have shown that NIRS-derived measures of systemic oxygen balance correlate with global circulatory measures, including SvO2 and biochemical indicators of shock. Additionally, NIRS has been shown in multiple prospective observational studies to identify circulatory inadequacy in specific organ systems, such as the brain, kidney, and gut. NIRS provides continuous, non-invasive measures that are suitable targets for goal-directed therapy to treat deficiencies in global and regional perfusion and should be standard of care.