Clinical validation of the non-invasive cardiac output monitor USCOM-1A in critically ill patients:

Use of the USCOM® noninvasive cardiac output measurement system to predict the development of pre-eclampsia in hypertensive pregnancies

OBJECTIVES

To assess the ability of the USCOM® (USCOM), using measurements of cardiac output (CO) and systemic vascular resistance (SVR), to predict the development of pre-eclampsia (PE) and severe PE in hypertensive pregnancies.

STUDY DESIGN

Prospective cohort study of women in the second or third trimester recruited at a tertiary center in Sydney, Australia. Demographic data and hemodynamic measurements using the USCOM were taken for all study participants at recruitment. Pregnancy outcome, including development of PE and severe PE, was tracked. Data were analyzed using ANOVA testing, pair-wise comparison testing, and Student's t-testing.

RESULTS

Recruitment included 65 normotensive controls, 34 women with chronic hypertension (CH), 51 with gestational hypertension (GH), and 21 with PE. Significantly higher weight, body surface area, and blood pressure measurements were found in the hypertensive, compared with the normotensive control and pregnancies. There were no observed differences in USCOM-measured CO, cardiac index, SVR, or systemic vascular resistance index between hypertensive women who did versus did not develop PE or severe PE in later pregnancy. Analysis of the CH and GH subgroups, as well as only unmedicated hypertensive women (n = 24), also showed no significant difference in hemodynamic parameters between those who did or did not develop PE or severe PE.

CONCLUSIONS

Our group was unable to successfully predict the onset of PE or severe PE based on hemodynamic parameters measured with the USCOM. It is possible this relates to the high proportion of women on antihypertensive medication at recruitment.

The ultrasound-based cardiac output monitoring is a useful tool to define baseline hemodynamic parameters in healthy permanent residents at high altitude: results of a monocentric pilot study

Previous studies on the cardiac data of healthy permanent residents living in high-altitude regions such as Tibet and the Andes have yielded inconsistent findings and significant disparities. These discrepancies can be mainly attributed to the invasive methods conventionally used for parameter evaluation. However, with the introduction of cutting-edge ultrasound technology, there is now an innovative approach to addressing and reconciling these variations. In this pilot study, we employed an ultrasound-based cardiac output monitoring (USCOM) device to evaluate cardiac output and related hemodynamic variables in a group of 20 healthy high-altitude Andean residents (comprising 10 men and 10 women) aged between 26 and 35 years old. The monocentric study was carried out in La Paz, Bolivia, located between at an altitude of 3,600-4,000 m. A total of 60 hemodynamic measurements were evaluated, accounting for three technical replicates per subject. Our results showed strong intrasubject reproducibility and revealed important differences related to both sex and hemodynamic parameters in highlanders compared to individuals residing at sea level. We conclude that USCOM represents a highly reliable technology for performing hemodynamic measurements in high-altitude residents. Our preliminary findings underscore the need for larger studies, encompassing larger sample sizes, specifically tailored to gender considerations, and extendable to broader highland populations. These findings have special significant implications for the management of hemodynamics in intensive care and postoperative settings, warranting further comprehensive research efforts.

Point-of-care Ultrasound to Assess Hemodynamic Contributors to Acute Kidney Injury in Pediatric Patients With Cerebral Malaria: A Pilot Study

BACKGROUND

Acute kidney injury is common in severe malaria and is independently associated with mortality. The pathogenesis of acute kidney injury (AKI) in severe malaria remains incompletely understood. Ultrasound-based tools such as point-of-care ultrasound (POCUS), ultrasound cardiac output monitors (USCOMs) and renal arterial resistive index (RRI) can be used to detect hemodynamic and renal blood flow abnormalities contributing to AKI in malaria.

METHODS

We conducted a prospective study of Malawian children with cerebral malaria to determine the feasibility of using POCUS and USCOM to characterize hemodynamic contributors to severe AKI (Kidney Disease: Improving Global Outcomes stage 2 or 3). The primary outcome was feasibility (completion rate of study procedures). We also assessed for differences in POCUS and hemodynamic variables for patients with or without severe AKI.

RESULTS

We enrolled 27 patients who had admission cardiac and renal ultrasounds and USCOM. Completion rates were high for cardiac (96%), renal (100%) and USCOM studies (96%). Severe AKI occurred in 13 of 27 patients (48%). No patients had ventricular dysfunction. Only 1 patient in the severe AKI group was determined to be hypovolemic ( P = 0.64). No significant differences in USCOM, RRI or venous congestion parameters were detected among patients with and without severe AKI. Mortality was 11% (3/27) with the 3 deaths occurring in the severe AKI group ( P = 0.056).

CONCLUSIONS

Ultrasound-based cardiac, hemodynamic and renal blood flow measurements appear to be feasible in pediatric patients with cerebral malaria. We were unable to detect hemodynamic or renal blood flow abnormalities contributing to severe AKI in cerebral malaria. Larger studies are needed to corroborate these findings.

Measurement of Cardiac Output Using an Ultrasonic Cardiac Output Monitor (USCOM) in Patients with Single-Ventricle Physiology

We evaluate the validity of cardiac index (CI) measurements utilizing the Ultrasonic Cardiac Output Monitor (USCOM), a non-invasive Doppler ultrasound device, by comparing measurements to cardiac catheterization-derived CI measurements in patients with single-ventricle physiology. USCOM measurements were repeated three times for each patient at the beginning of a cardiac catheterization procedure for twenty-six patients undergoing elective pre-Glenn or pre-Fontan catheterization. CI was measured by USCOM and was calculated from cardiac catheterization data using Fick's method. Bland-Altman analysis for CI showed bias of 0.95 L/min/m² with the 95% limits of agreement of - 1.85 and 3.75. Pearson's correlation coefficient was 0.89 (p < 0.001) indicating a strong positive relationship between USCOM and cardiac catheterization CI measurements. When excluding two patients with significant dilation of the neo-aortic valve (z-score >  + 5), the bias improved to 0.66 L/min/m² with the 95% limits of agreement of - 1.38 and 2.70. Percent error of limits of agreement was 34%. There was excellent intra-operator reproducibility of USCOM CI measurements with an intra-class coefficient of 0.96. We demonstrate the use of USCOM to measure CI in patients with single-ventricle physiology for the first time, showing acceptable agreement of the CI measurements between USCOM and cardiac catheterization with a high intra-operator reproducibility.

Role of placental, fetal and maternal cardiovascular markers in predicting adverse outcome in women with suspected or confirmed pre-eclampsia

OBJECTIVE

To assess the performance of placental, fetal and maternal cardiovascular markers in the prediction of adverse perinatal and maternal outcomes in women with suspected or confirmed pre-eclampsia.

METHODS

This was a prospective prognostic accuracy study of women with suspected or confirmed pre-eclampsia who underwent a series of investigations to measure maternal hemodynamic indices, mean arterial pressure, augmentation index, ophthalmic artery peak systolic velocity (PSV) ratio, uterine artery pulsatility index (UtA-PI), fetal biometric and Doppler parameters, soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF). The performance of these markers, individually or in combination, in predicting adverse perinatal and maternal outcomes was then assessed using receiver-operating-characteristics (ROC)-curve analysis. Adverse maternal outcome was defined as one or more of severe hypertension, admission to the intensive care unit, eclampsia, placental abruption, HELLP syndrome, disseminated intravascular coagulation, platelets < 100 × 10⁹ /L, creatinine > 90 μmol/L and alanine aminotransferase > 100 U/L. Adverse perinatal outcome was defined as one or more of preterm birth at or before 34 + 0 weeks, neonatal intensive care unit admission for > 48 h, respiratory distress syndrome, intraventricular hemorrhage, hypoxic ischemic encephalopathy, necrotizing enterocolitis, retinopathy of prematurity and confirmed fetal infection.

RESULTS

We recruited 126 women with suspected (n = 31) or confirmed (n = 95) pre-eclampsia at a median gestational age of 33.9 weeks (interquartile range, 30.9-36.3 weeks). Pregnancies with adverse perinatal outcome compared to those without had a higher median UtA-PI (1.3 vs 0.8; P < 0.001), ophthalmic artery PSV ratio (0.8 vs 0.7; P = 0.01) and umbilical artery PI percentile (82.0 vs 68.5; P < 0.01) and lower median estimated fetal weight percentile (4.0 vs 43.0; P < 0.001), abdominal circumference percentile (4.0 vs 63.0; P < 0.001), middle cerebral artery PI percentile (28.0 vs 58.5; P < 0.001) and cerebroplacental ratio percentile (18.0 vs 46.5; P < 0.001). Pregnancies with adverse perinatal outcome also had a higher median sFlt-1 (8208.0 pg/mL vs 4508.0 pg/mL; P < 0.001), lower PlGF (27.2 pg/mL vs 76.3 pg/mL; P < 0.001) and a higher sFlt-1/PlGF ratio (445.4 vs 74.4; P < 0.001). The best performing individual marker for predicting adverse perinatal outcome was the sFlt-1/PlGF ratio (area under the ROC curve (AUC), 0.87 (95% CI, 0.81-0.93)), followed by estimated fetal weight (AUC, 0.81 (95% CI, 0.73-0.89)). Women who experienced adverse maternal outcome had a higher median sFlt-1 level (7471.0 pg/mL vs 5131.0 pg/mL; P < 0.001) and sFlt-1/PlGF ratio (204.3 vs 93.3; P < 0.001) and a lower PlGF level (37.0 pg/mL vs 66.1 pg/mL; P = 0.01) and estimated fetal weight percentile (16.5 vs 37.0; P = 0.04). All markers performed poorly in predicting adverse maternal outcome, with sFlt-1 (AUC, 0.69 (95% CI, 0.60-0.79)) and sFlt-1/PlGF ratio (AUC, 0.69 (95% CI, 0.59-0.78)) demonstrating the best individual performance. The addition of cardiovascular, fetal or other placental indices to the sFlt-1/PlGF ratio did not improve the prediction of adverse maternal or perinatal outcomes.

CONCLUSIONS

The sFlt-1/PlGF ratio performs well in predicting adverse perinatal outcomes but is a poor predictor of adverse maternal outcomes in women with suspected or diagnosed pre-eclampsia. The addition of cardiovascular or fetal indices to the model is unlikely to improve the prognostic performance of the sFlt-1/PlGF ratio. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Characteristics of hemodynamic parameters after fluid resuscitation and vasoactive drugs administration in pediatric shock: A prospective observational study

Background

Prior studies have shown that septic shock survivors had a normal cardiac index (CI) and systemic vascular resistance index (SVRI). However, this feature seems to be questionable in other-caused shock, since several factors are associated with the hemodynamic profile. This study aims to describe hemodynamic profiles (preload, inotropy, afterload, stroke volume, and cardiac output) after fluid resuscitation and vasoactive therapy in children with shock.

Methods

Children aged 1 month to 18 years old with shock conditions were included in this study. Fluid resuscitation was administered following the American College of Critical Care Medicine (ACCM) protocol. Hemodynamic profiles were assessed at 1 and 6 h from the start of fluid resuscitation. Grouping of the subjects was determined by the USCOM examination in 1st hour until the end of the study and we divided into 3 groups.

Results

At 1 h, group 1 (low CI) was 14% (CI:2.5[1.2–3.2]L/min/m²), group 2 (normal CI) was 66% (CI:4.2[3.4–5.8]L/min/m²), and group 3 (high CI) was 20% (CI:7.1[6.1–9.4]L/min/m²). SVRI was higher in groups 1 and 2 compared to group 3 (p < 0.05). Group 1 and 2 revealed fluid-refractory shock (SVV:25[12–34]% and 29(13–58)%, respectively), lower Smith-Madigan Inotropy Index (SMII) and higher Potential to Kinetic Ratio (PKR) compared to group 3 (p < 0.05). Group 3 revealed fluid-responsive shock (Stroke Volume Variation (SVV):32[18–158]%), higher SMII and lower PKR. At 6th hour, CI in all groups were normal (group 1:3.5[1.2–7.5]; group 2:4.0[1.7–6.1]; group 3:6.0[3.1–6.2]). However, 71.4% and 54.5% of subjects in groups 1 and 2, respectively, still revealed low inotropy. Group 3 revealed a significant increase in SVRI and PKR (p < 0.01).

Conclusions

Most pediatric shock patients were hypodynamic. Even when the CI was normal, the preload, inotropy, and afterload may still be abnormal. It represented the inotropy as a key to hemodynamic.

•

Describe the macrocirculation parameter (preload, inotropy, afterload) in children with shock.

•

Most pediatric shock tend to be hypodynamic.

•

Fluid and vasoactive agent therapy should be guided by combination of the hemodynamic parameters.

Bioimpedance analysis as a tool for hemodynamic monitoring: overview, methods and challenges

Recent advances in hemodynamic monitoring have seen the advent of non-invasive methods which offer ease of application and improve patient comfort. Bioimpedance Analysis or BIA is one of the currently employed non-invasive techniques for hemodynamic monitoring. Impedance Cardiography (ICG), one of the implementations of BIA, is widely used as a non-invasive procedure for estimating hemodynamic parameters such as stroke volume (SV) and cardiac output (CO). Even though BIA is not a new diagnostic technique, it has failed to gain consensus as a reliable measure of hemodynamic parameters. Several devices have emerged for estimating CO using ICG which are based on evolving methodologies and techniques to calculate SV. However, the calculations are generally dependent on the electrode configurations (whole body, segmental or localised) as well as the accuracy of different techniques in tracking blood flow changes. Blood volume changes, concentration of red blood cells, pulsatile velocity profile and ambient temperature contribute to the overall conductivity of blood and hence its impedance response during flow. There is a growing interest in investigating limbs for localised BIA to estimate hemodynamic parameters such as pulse wave velocity. As such, this paper summarises the current state of hemodynamic monitoring through BIA in terms of different configurations and devices in the market. The conductivity of blood flow has been emphasized with contributions from both volume and velocity changes during flow. Recommendations for using BIA in hemodynamic monitoring have been mentioned highlighting the suitable range of frequencies (1 kHz-1 MHz) as well as safety considerations for a BIA setup. Finally, current challenges in using BIA such as geometry assumption and inaccuracies have been discussed while mentioning potential advantages of a multi-frequency analysis to cover all the major contributors to blood's impedance response during flow.

Investigating Electrical Impedance Spectroscopy for Estimating Blood Flow-Induced Variations in Human Forearm

This work aims to investigate the feasibility of employing multi-frequency bioimpedance analysis for hemodynamic assessment. Towards this, we aim to explore one of its implementations, electrical impedance spectroscopy (EIS), for estimating changes in radial artery diameter due to blood flow. Following from our previous investigations, here, we use a commercial device-the Quadra^® Impedance Spectroscopy device-for impedance measurements of the forearm of three subjects under normal conditions and occluding the artery with a cuff. This was performed simultaneously with ultrasound measurements as a reference. The impedance spectra were measured over time, yielding waveforms reflecting changes due to blood flow. Contributions from the fat/muscle domains were accounted for using the occluded impedance response, resulting in arterial impedance. A modified relationship was approximated to calculate the diameter from the arterial impedance, which showed a similarity with ultrasound measurements. Comparison with the ultrasound measurements revealed differences in phase and amplitude, primarily due to the approximated relationship between impedance and diameter and neglecting the impedance phase analysis. This work shows the potential of EIS, with improvements, towards estimating blood flow-induced variation in arteries. Further analysis and improvements could help place this technology in mainstream clinical practice for hemodynamic monitoring.

Rationale for using the velocity-time integral and the minute distance for assessing the stroke volume and cardiac output in point-of-care settings

Background

Stroke volume (SV) and cardiac output (CO) are basic hemodynamic parameters which aid in targeting organ perfusion and oxygen delivery in critically ill patients with hemodynamic instability. While there are several methods for obtaining this data, the use of transthoracic echocardiography (TTE) is gaining acceptance among intensivists and emergency physicians. With TTE, there are several points that practitioners should consider to make estimations of the SV/CO as simplest as possible and avoid confounders.

Main body

With TTE, the SV is usually obtained as the product of the left ventricular outflow tract (LVOT) cross-sectional area (CSA) by the LVOT velocity–time integral (LVOT VTI); the CO results as the product of the SV and the heart rate (HR). However, there are important drawbacks, especially when obtaining the LVOT CSA and thus the impaction in the calculated SV and CO. Given that the LVOT CSA is constant, any change in the SV and CO is highly dependent on variations in the LVOT VTI; the HR contributes to CO as well. Therefore, the LVOT VTI aids in monitoring the SV without the need to calculate the LVOT CSA; the minute distance (i.e., SV × HR) aids in monitoring the CO. This approach is useful for ongoing assessment of the CO status and the patient’s response to interventions, such as fluid challenges or inotropic stimulation. When the LVOT VTI is not accurate or cannot be obtained, the mitral valve or right ventricular outflow tract VTI can also be used in the same fashion as LVOT VTI. Besides its pivotal role in hemodynamic monitoring, the LVOT VTI has been shown to predict outcomes in selected populations, such as in patients with acute decompensated HF and pulmonary embolism, where a low LVOT VTI is associated with a worse prognosis.

Conclusion

The VTI and minute distance are simple, feasible and reproducible measurements to serially track the SV and CO and thus their high value in the hemodynamic monitoring of critically ill patients in point-of-care settings. In addition, the LVOT VTI is able to predict outcomes in selected populations.

Emergency department non-invasive cardiac output study (EDNICO): an accuracy study

BACKGROUND

There is little published data investigating non-invasive cardiac output monitoring in the emergency department (ED). We assess here the accuracy of five non-invasive methods in detecting fluid responsiveness in the ED: (1) common carotid artery blood flow, (2) suprasternal aortic Doppler, (3) bioreactance, (4) plethysmography with digital vascular unloading method, and (5) inferior vena cava collapsibility index. Left ventricular outflow tract echocardiography derived velocity time integral is the reference standard. This follows an assessment of feasibility and repeatability of these methods in the same cohort of ED patients.

METHODS

This is a prospective observational study of non-invasive methods for assessing fluid responsiveness in the ED. Participants were non-ventilated ED adult patients requiring intravenous fluid resuscitation. Sensitivity and specificity of each method in determining the fluid responsiveness status of participants is determined in comparison to the reference standard.

RESULTS

Thirty-three patient data sets were included for analysis. The specificity and sensitivity to detect fluid responders was 46.2 and 45% for common carotid artery blood flow (CCABF), 61.5 and 63.2% for suprasternal artery Doppler (SSAD), 46.2 and 50% for bioreactance, 50 and 41.2% for plethysmography vascular unloading technique (PVUT), and 63.6 and 47.4% for inferior vena cava collapsibility index (IVCCI), respectively. Analysis of agreement with Cohen's Kappa - 0.08 for CCABF, 0.24 for SSAD, - 0.04 for bioreactance, - 0.08 for PVUT, and 0.1 for IVCCI.

CONCLUSION

In this study, non-invasive methods were not found to reliably identify fluid responders. Non-invasive methods of identifying fluid responders are likely to play a key role in improving patient outcome in the ED in fluid depleted states such as sepsis. These results have implications for future studies assessing the accuracy of such methods.

Emergency department non-invasive cardiac output study (EDNICO): a feasibility and repeatability study

Background

There is little published data investigating non-invasive cardiac output monitoring in the emergency department (ED). We assessed six non-invasive fluid responsiveness monitoring methods which measure cardiac output directly or indirectly for their feasibility and repeatability of measurements in the ED: (1) left ventricular outflow tract echocardiography derived velocity time integral, (2) common carotid artery blood flow, (3) suprasternal aortic Doppler, (4) bioreactance, (5) plethysmography with digital vascular unloading method, and (6) inferior vena cava collapsibility index.

Methods

This is a prospective observational study of non-invasive methods of assessing fluid responsiveness in the ED. Participants were non-ventilated ED adult patients requiring intravenous fluid resuscitation. Feasibility of each method was determined by the proportion of clinically interpretable measurements from the number of measurement attempts. Repeatability was determined by comparing the mean difference of two paired measurements in a fluid steady state (after participants received an intravenous fluid bolus).

Results

76 patients were recruited in the study. A total of 207 fluid responsiveness measurement sets were analysed. Feasibility rates were 97.6% for bioreactance, 91.3% for vascular unloading method with plethysmography, 87.4% for common carotid artery blood flow, 84.1% for inferior vena cava collapsibility index, 78.7% for LVOT VTI, and 76.8% for suprasternal aortic Doppler. The feasibility rates difference between bioreactance and all other methods was statistically significant.

Conclusion

Our study shows that non-invasive fluid responsiveness monitoring in the emergency department may be feasible with selected methods. Higher repeatability of measurements were observed in non-ultrasound methods. These findings have implications for further studies specifically assessing the accuracy of such non-invasive cardiac output methods and their effect on patient outcome in the ED in fluid depleted states such as sepsis.

Electronic supplementary material

The online version of this article (10.1186/s13049-019-0586-6) contains supplementary material, which is available to authorized users.

The assessment of circulating volume using inferior vena cava collapse index and carotid Doppler velocity time integral in healthy volunteers: a pilot study

BACKGROUND

Assessment of circulating volume and the requirement for fluid replacement are fundamental to resuscitation but remain largely empirical. Passive leg raise (PLR) may determine fluid responders while avoiding potential fluid overload. We hypothesised that inferior vena cava collapse index (IVCCI) and carotid artery blood flow would change predictably in response to PLR, potentially providing a non-invasive tool to assess circulating volume and identifying fluid responsive patients.

METHODS

We conducted a prospective proof of concept pilot study on fasted healthy volunteers. One operator measured IVC diameter during quiet respiration and sniff, and carotid artery flow. Stroke volume (SV) was also measured using suprasternal Doppler. Our primary endpoint was change in IVCCI after PLR. We also studied changes in IVCCI after "sniff", and correlation between carotid artery flow and SV.

RESULTS

Passive leg raise was associated with significant reduction in the mean inferior vena cava collapsibility index from 0.24 to 0.17 (p < 0.01). Mean stroke volume increased from 56.0 to 69.2 mL (p < 0.01). There was no significant change in common carotid artery blood flow. Changes in physiology consequent upon passive leg raise normalised rapidly.

DISCUSSION

Passive leg raise is associated with a decrease of IVCCI and increase in stroke volume. However, the wide range of values observed suggests that factors other than circulating volume predominate in determining the proportion of collapse with respiration.

CONCLUSION

In contrast to other studies, we did not find that carotid blood flow increased with passive leg raise. Rapid normalisation of post-PLR physiology may account for this.

In vitro evaluation of an ultrasonic cardiac output monitoring (USCOM) device

Non-invasive cardiac output monitoring techniques provide high yield, low risk mechanisms to identify and individually treat shock in the emergency setting. The non-invasive ultrasonic cardiac output monitoring (USCOM) device uses an ultrasound probe applied externally to the chest; however limitations exist with previous validation strategies. This study presents the in vitro validation of the USCOM device against calibrated flow sensors and compares user variability in simulated healthy and septic conditions. A validated mock circulation loop was used to simulate each condition with a range of cardiac outputs (2-10 l/min) and heart rates (50-95 bpm). Three users with varying degrees of experience using the USCOM device measured cardiac output and heart rate by placing the ultrasound probe on the mock aorta. Users were blinded to the condition, heart rate and cardiac output which were randomly generated. Results were reported as linear regression slope (β). All users estimated heart rate in both conditions with reasonable accuracy (β = 0.86-1.01), while cardiac output in the sepsis condition was estimated with great precision (β = 1.03-1.04). Users generally overestimated the cardiac output in the healthy simulation (β = 1.07-1.26) and reported greater difficulty estimating reduced cardiac output compared with higher values. Although there was some variability between users, particularly in the healthy condition (P < 0.01), all estimations were within a clinically acceptable range. In this study the USCOM provided a suitable measurement of cardiac output and heart rate when compared with our in vitro system. It is a promising technique to assist with the identification and treatment of shock.

Age-specific non-invasive transcutaneous Doppler ultrasound derived haemodynamic reference ranges in elderly Chinese adults

Background

Whilst there is a presumption in medicine that ageing adversely affects cardiovascular function, it is unknown if resting haemodynamics are compromised in the elderly, and if so, to what degree. This study was intended to answer several questions; whether age-related changes in haemodynamics occur; whether there was a difference between the haemodynamics of ageing subjects with and without mild chronic disease; whether there was a difference in haemodynamics as measured from either the aortic or the pulmonary valve; and to establish reference ranges for this population.

Methods

Chinese adults aged over 60 years were divided into three age bands of 61–70, 71–80 and over 80 years. The haemodynamic parameters were measured using a non-invasive Doppler ultrasound-based instrument, the Ultrasonic Cardiac Output Monitor (USCOM).

Results

One hundred and sixty-five subjects (48.5% males) were recruited. 78 (47.3%) had no known disease whilst 87 (52.7%) had mild chronic illness. A total of 21 individual haemodynamic parameters were measured or calculated for each subject. There were no significant differences in stroke volume (SV), cardiac output (CO), systemic vascular resistance (SVR) or in body surface area (BSA)-indexed parameters, SV index (SVI), cardiac index (CI) and SVR index (SVRI) across age groups, or in other indexed haemodynamic parameters. No significant differences in indexed haemodynamics were found between those subjects with and those without mild chronic disease. Small, statistically significant, but clinically insignificant, differences (< 5%) were found between the aortic and pulmonary valve measurements for SV, SVI and heart rate.

Conclusions

Ageing does not have any significant effect on resting haemodynamics in the elderly population studied. Mild chronic disease does not adversely affect resting haemodynamics in this population.

General Significance

Reference ranges were established for 21 haemodynamic parameters, as measured by USCOM, for an elderly Chinese population but not for non-Chinese populations.

•

Ageing has no significant effect on resting haemodynamics in the population studied.

•

Mild chronic disease does not adversely affect resting haemodynamics in this population.

•

Reference ranges were established for 21 haemodynamic parameters in Chinese elderly.

Influence of different positions on hemodynamics derived from noninvasive transcutaneous Doppler ultrasound

A proper alignment of the ultrasound beam to the aortic or pulmonary outflow tracts is essential to acquire accurate signals. This study aimed to investigate the influence of different positions on the acquisition of Doppler signals using a noninvasive transcutaneous Doppler ultrasound. This was a prospective observational crossover study. Two operators performed hemodynamics measurements on each subject in supine, sitting, semirecumbent, passive leg raising (PLR) 20°, and PLR 60° positions using both aortic and pulmonary approaches. All Doppler flow profile images were assessed using the Fremantle and Prince of Wales Hospital criteria. Time required to obtain Doppler signals was recorded. A total of 60 subjects (50% males) aged 18–60 years old were investigated. In both sitting and semirecumbent positions, aortic stroke volume indexes (SVIs) and cardiac indexes (CIs) were significantly lower than those in the other three positions while the pulmonary CIs were comparable to that in the supine position. In the sitting position, the aortic signal qualities were lower and the time to obtain the pulmonary Doppler signals was prolonged. Instead, the signal quality and the time to obtain the Doppler signals in the semirecumbent position were similar to those in the other three positions using the pulmonary approach. PLR did not cause a significant increase in SVI regardless of the degree of leg elevation. These data show that it is feasible to perform the noninvasive transcutaneous Doppler ultrasound using the pulmonary approach in the semirecumbent position for patients unable to maintain the supine position. The aortic approach in the sitting and semirecumbent positions is not suitable as it is not sufficiently reliable.

Urgent ultrasound guided hemodynamic assessments by a pediatric medical emergency team: a pilot study

Purpose

To determine the feasibility of using the Ultrasound Cardiac Output Monitor (USCOM) as an adjunct during hemodynamic assessments by a pediatric medical emergency team (PMET).

Methods

Pediatric in-patients at McMaster Children’s Hospital aged under 18 years requiring urgent PMET consultation, were eligible. Patients with known cardiac outflow valve defects, Pediatric Critical Care Unit in-patients, and those in cardiorespiratory arrest, were excluded. The primary outcome was feasibility, and the ease of USCOM transport and application as assessed by a self-administered user questionnaire. Secondary outcomes included the quality of USCOM measurements, and agreement in clinical versus USCOM-derived assessments.

Results

Forty-one patients from 85 eligible PMET consultations were enrolled between March and August 2011. A total of 55 USCOM assessments were performed on 36 of 41 (87.8%) participants. USCOM could not be completed in 5 (12.2%) participants due to patient agitation (n = 4) and emergent care (n = 1). USCOM was reported as easy to transport and apply by 97.4% and 94.7% of respondents respectively, not obstructive to patient care by 94.7%, and yielded timely measurements by 84.2% respondents. USCOM tracings were of good quality in 41 (75.9%) assessments. Agreement between clinical and USCOM-derived hemodynamic assessments by two independent raters was poor (Rater 1: κ = 0.094; Rater 2: κ = 0.146).

Conclusion

USCOM can be applied by a PMET during urgent hemodynamic assessments in children. While USCOM has been validated in stable children, its role in guiding hemodynamic resuscitation and informing therapeutic goals in a hemodynamically unstable pediatric population requires further investigation.

Cardiotoxicity After Anthracycline Treatment in Survivors of Adult Cancers: Monitoring by USCOM, Echocardiography and Serum Biomarkers

Background

Anthracyclines are agents with a well known documented anti-tumoral activity. Cardiac side effects are the principal toxicity. Here we evaluate and monitor the onset of late anthracycline-induced cardiotoxicity with real-time CW-Doppler ultrasound cardiac output monitoring (USCOM®) and echocardiography in combination with serum biomarkers.

Methods

Fifty-two patients without cardiac disease who had received an anthracycline-based regimen for various cancer types were included in this study. Patients’ hemodynamic parameters as stroke volume (SV USCOM (mL)) and ejection fraction (EF ECHOCARDIOGRAPHY (%)) were measured with USCOM and echocardiography and correlated to serum biomarkers (NT-pro-BNP and cTnT).

Results

Eighteen patients (34.6%) developed cardiac disease (NYHA I-III). An increasing cumulative anthracycline dose was associated with a decrease of the EF determined by echocardiography as well the SV by USCOM and with a higher NYHA class. Those patients who experienced cardiac disease showed a reduction of the EF and SV and increased serum biomarkers.

Conclusions

Real-time CW-Doppler USCOM, is a fast and reliable method to monitor late hemodynamic changes as a symptom of anthracycline-induced cardiotoxicity comparable to the findings by echocardiography and serum biomarkers.

Pulmonary Artery Catheter (PAC) Accuracy and Efficacy Compared with Flow Probe and Transcutaneous Doppler (USCOM): An Ovine Cardiac Output Validation

Background. The pulmonary artery catheter (PAC) is an accepted clinical method of measuring cardiac output (CO) despite no prior validation. The ultrasonic cardiac output monitor (USCOM) is a noninvasive alternative to PAC using Doppler ultrasound (CW). We compared PAC and USCOM CO measurements against a gold standard, the aortic flow probe (FP), in sheep at varying outputs. Methods. Ten conscious sheep, with implanted FPs, had measurements of CO by FP, USCOM, and PAC, at rest and during intervention with inotropes and vasopressors. Results. CO measurements by FP, PAC, and USCOM were 4.0 ± 1.2 L/min, 4.8 ± 1.5 L/min, and 4.0 ± 1.4 L/min, respectively, (n = 280, range 1.9 L/min to 11.7 L/min). Percentage bias and precision between FP and PAC, and FP and USCOM was -17 and 47%, and 1 and 36%, respectively. PAC under-measured Dobutamine-induced CO changes by 20% (relative 66%) compared with FP, while USCOM measures varied from FP by 3% (relative 10%). PAC reliably detected -30% but not +40% CO changes, as measured by receiver operating characteristic area under the curve (AUC), while USCOM reliably detected ±5% changes in CO (AUC > 0.70). Conclusions. PAC demonstrated poor accuracy and sensitivity as a measure of CO. USCOM provided equivalent measurements to FP across a sixfold range of outputs, reliably detecting ±5% changes.

Anthracycline-induced cardiotoxicity: cardiac monitoring by continuous wave-Doppler ultrasound cardiac output monitoring and correlation to echocardiography

BACKGROUND

Anthracyclines are agents with a wellknown cardiotoxicity. The study sought to evaluate the hemodynamic response to an anthracycline using realtime continuous-wave (CW)-Doppler ultrasound cardiac output monitoring (USCOM) and echocardiography in combination with serum biomarkers.

METHODS

50 patients (26 male, 24 female, median age 59 years) suffering from various types of cancer received an anthracycline-based regimen. Patients' responses were measured at different time points (T0 prior to infusion, T1 6 h post infusion, T2 after 1 day, T3 after 7 days, and T4 after 3 months) with CW-Doppler ultrasound (T0-T4) and echocardiography (T1, T4) for hemodynamic parameters such as stroke volume (SV; SVUSCOM ml) and ejection fraction (EF; EFechocardiography%) and with NT-pro-BNP and hs-Troponin T (T0-T4).

RESULTS

During the 3-month observation period, the relative decrease in the EF determined by echocardiography was -2.1% (▵T0-T4, T0 71 ± 7.8%, T4 69.5 ± 7%, p = 0.04), whereas the decrease in SV observed using CW-Doppler was -6.5% (▵T0-T4, T0 54 ± 19.2 ml, T4 50.5 ± 20.6 ml, p = 0.14). The kinetics for serum biomarkers were inversely correlated.

CONCLUSIONS

Combining real-time CW-Doppler USCOM and serum biomarkers is feasible for monitoring the immediate and chronic hemodynamic changes during an anthracycline-based regimen; the results obtained were comparable to those from echocardiography.

Cardiac Output Measurements in Septic Patients: Comparing the Accuracy of USCOM to PiCCO

USCOM is an ultrasound-based method which has been accepted for noninvasive hemodynamic monitoring in various clinical conditions (USCOM, Ultrasonic cardiac output monitoring). The present study aimed at comparing the accuracy of the USCOM device with that of the thermodilution technique in patients with septicemia. We conducted a prospective observational study in a medical but noncardiological ICU of a university hospital. Septic adult patients (median age 55 years, median SAPS-II-Score 43 points) on mechanical ventilation and catecholamine support were monitored with USCOM and PiCCO (n = 70). Seventy paired left-sided CO measurements (transaortic access = CO_US-A) were obtained. The mean CO_US-A were 6.55 l/min (±2.19) versus CO_PiCCO 6.5 l/min (±2.18). The correlation coefficient was r = 0.89. Comparison by Bland-Altman analysis revealed a bias of −0.36 l/min (±0.99 l/min) leading to a mean percentage error of 29%. USCOM is a feasible and rapid method to evaluate CO in septic patients. USCOM does reliably represent CO values as compared to the reference technique based on thermodilution (PiCCO). It seems to be appropriate in situations where CO measurements are most pertinent to patient management.

Clinical review: Update on hemodynamic monitoring--a consensus of 16

Hemodynamic monitoring plays a fundamental role in the management of acutely ill patients. With increased concerns about the use of invasive techniques, notably the pulmonary artery catheter, to measure cardiac output, recent years have seen an influx of new, less-invasive means of measuring hemodynamic variables, leaving the clinician somewhat bewildered as to which technique, if any, is best and which he/she should use. In this consensus paper, we try to provide some clarification, offering an objective review of the available monitoring systems, including their specific advantages and limitations, and highlighting some key principles underlying hemodynamic monitoring in critically ill patients.

Intra- and inter-observer reliability using a noninvasive ultrasound cardiac output monitor in healthy anesthetized children

BACKGROUND

Accurate and reliable evaluation of cardiac index (CI) in critically ill pediatric patients can optimize their management. Although validated, noninvasive ultrasound measurement techniques have been previously shown to be unreliable because of observer variability.

OBJECTIVE

To confirm intra- and inter-observer reliability when using the noninvasive USCOM(®) in healthy anesthetized children.

METHODS

Prospective observational study at the Children's Hospital of Eastern Ontario, Ottawa, included newborns to 12 years of age undergoing elective surgery or magnetic resonance imaging. The USCOM(®) was used to assess CI via aortic flow with a trans-sternal approach. Two trained observers were responsible for taking two measurements of CI each at steady state in randomized succession after stable depth of anesthesia was achieved.

RESULTS

Fifty-nine patients were included. Forty-seven (80%) were between 3 and 7 years old, with 57% male. The mean difference ± sd for repeat CI measurements by each of two observers was 0.11 ± 0.47 and 0.05 ± 0.65 l·min(-1) ·m(-2) , respectively. Intra-observer reliability for these repeat measurements by each observer determined by Lin's concordance correlation coefficient was 0.92 and 0.85, respectively. The mean difference ± sd between observers was 0.16 ± 0.59 l·min(-1) ·m(-2) , and Lin's concordance correlation coefficient was 0.87. The two observers subjectively rated measurements as 'Difficult' or 'Very difficult' only 14% (16/118) and 3% (4/118) of the time, respectively. No adverse events were reported.

CONCLUSION

This study confirms that the USCOM(®) is relatively easy to use and reliable in healthy children when operated by trained users.

The Acute Impact of Smoking One Cigarette on Cardiac Hemodynamic Parameters

Background

The acute impact of tobacco smoking on the cardiac hemodynamic parameters and its pathological implication in the process of arterial atherosclerosis need further exploration. This investigation was purposed to assess the acute impact of tobacco smoke on blood pressure and cardiac hemodynamic parameters.

Methods

Using an Ultrasonic Cardiac Output Monitor, and DINAMAP Pro 400 Series V2 blood pressure monitor, several cardiac hemodynamic parameters and the blood pressure were assessed in 14 smokers, 11 females and 3 males, at 2 time points, before and after smoking of one cigarette. Data, in terms of ratio of the means and 95% confidence interval were analyzed using ANOVA.

Results

Single-subject design in which the subject has served as his/her own control has been used. Tobacco smoking led to statistically significant acute increase in the means of all hemodynamic parameters, except for heart rate in female subjects, as compared to the means obtained before smoking.

Conclusions

Cigarette smoking induces acute non-physiologic alteration in cardiac outflow forces, exposing the aortic valve and arch to mechanical injury that might be implicated in initiating and promoting the process of aortic arch atherosclerosis and associated pathological lesions.

Cardiac index measurements by transcutaneous Doppler ultrasound and transthoracic echocardiography in adult and pediatric emergency patients

INTRODUCTION

Non-invasive hemodynamic monitoring may facilitate resuscitation in critically ill patients. Validation studies examining a transcutaneous Doppler ultrasound technology, USCOM-1A, using pulmonary artery catheter as the reference standard showed varying results. In this study, we compared non-invasive cardiac index (CI) measurements by USCOM-1A with transthoracic echocardiography (TTE).

METHODS

This study was a prospective, observational cohort study at a university tertiary-care emergency department, enrolling a convenience sample of adult and pediatric patients. Paired measures of CI, stroke volume index (SVI), aortic outflow tract diameter (OTD), velocity time integral (VTI) were obtained using USCOM-1A and TTE. Pearson's correlation and Bland-Altman analyses were performed.

RESULTS

One-hundred and sixteen subjects were enrolled, with obtainable USCOM-1A CI measurements for 99 subjects (55 adults age 50 +/- 20 years and 44 children age 11 +/- 4 years) in the final analysis. Cardiac, gastrointestinal and infectious illnesses were the most common presenting diagnostic categories. The reference standard TTE measurements of CI, SVI, OTD, and VTI in all subjects were 3.08 +/- 1.18 L/min/m(2), 37.10 +/- 10.91 mL/m(2), 1.92 +/- 0.36 cm, and 20.36 +/- 4.53 cm, respectively. Intra-operator reliability of USCOM-1A CI measurements showed a correlation coefficient of r = 0.79, with 11 +/- 22% difference between repeated measures. The bias and limits of agreement of USCOM-1A compared to TTE CI were 0.58 (-1.48 to 2.63) L/min/m(2). The percent difference in CI measurements with USCOM-1A was 31 +/- 28% relative to TTE measurements.

CONCLUSIONS

The USCOM-1A hemodynamic monitoring technology showed poor correlation and agreement to standard transthoracic echocardiography measures of cardiac function. The utility of USCOM-1A in the management of critically ill patients remains to be determined.