Measurement of systemic oxygen delivery and inotropy in healthy term neonates with the Ultrasonic Cardiac Output Monitor (USCOM)

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.

The clinical value of ultrasonic cardiac output monitor in very-low birth-weight and extremely-low-birth-weight infants undergoing PDA ligation

BACKGROUND

Cardiorespiratory instability occurs very often in very-low-birth-weight (VLBW) and extremely-low-birth-weight (ELBW) infants undergoing patent ductus arteriosus (PDA) ligation during the early postoperative period. This study aimed to investigate ultrasonic cardiac output monitor (USCOM) as a bedside tool by evaluating the hemodynamic changes in preterm infants following PDA ligation and assessing factors that may influence these changes.

METHODS

This was a single-center prospective observational study at a third-level neonatal intensive care unit. A total of 33 infants, including 21 VLBW and 12 ELBW infants, were involved. Hemodynamic measurements were performed in these infants using a USCOM preoperatively as well as 0-1 h, 8-10 h, and 24 h postoperatively.

RESULTS

The PDA ligation was associated with reductions of the left ventricular cardiac output (LVCO) (P < 0.001), cardiac index (P < 0.001), flow time corrected (FTC) (P < 0.001), Smith-Madigan inotropy index (SMII) (P < 0.001), oxygen delivery (DO₂) (P < 0.001), and oxygen delivery index (DO₂I) (P < 0.001) and an increase of the systemic vascular resistance index (SVRI) (P < 0.001) at 0-1 h, 8-10 h, and 24 h post-ligation compared with the respective preoperative values. Compared with the respective values at 0-1 h post-ligation, there was no significant difference in the CI, SMII, or FTC at 8-10 h and 24 h post-ligation. However, the SVRI decreased at 8-10 h and 24 h post-ligation. Moreover, the DO₂I increased at 8-10 h and 24 h post-ligation, and the LVCO and DO₂ increased at 24 h post-ligation.

CONCLUSION

Our study confirmed that the hemodynamic changes measured by the USCOM were similar to those measured by echocardiography in previous reports. Thus, USCOM is a useful and convenient bedside tool for assessing hemodynamic changes to guide the use of fluids, inotropic agents, and vasopressors and help modify the post-ligation course, and they may be a surrogate for repeated echocardiography during the early post-ligation period in preterm infants or a preliminary screening method.

Reduced Echocardiographic Inotropy Index after Cardiopulmonary Bypass Is Associated With Complications After Cardiac Surgery: An Institutional Outcomes Study

OBJECTIVE

Despite advances in echocardiography and hemodynamic monitoring, limited progress has been made to effectively quantify left ventricular function during cardiac surgery. Traditional measures, including left ventricular ejection fraction (LVEF) and cardiac index, remain dependent on loading conditions; more complex measures remain impractical in a dynamic surgical setting. However, the Smith-Madigan Inotropy Index (SMII) and potential-to-kinetic energy ratio (PKR) offer promise as measures calculable during cardiac surgery and potentially predictive of outcomes. Using echocardiographic and hemodynamic monitoring data, the authors aimed to calculate SMII and PKR values after cardiopulmonary bypass and understand associations with postoperative outcomes, adjusting for previously identified risk factors.

DESIGN

Observational cohort study.

SETTING

Tertiary care academic hospital.

PATIENTS

The study comprised 189 elective adult cardiac surgical procedures from 2015-2016.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was postoperative mortality or organ system complication (stroke, prolonged ventilation, reintubation, cardiac arrest, acute kidney injury, new-onset atrial fibrillation). After adjustment, SMII <0.83 W/m² independently predicted the primary outcome (adjusted odds ratio 2.19, 95% confidence interval 1.08-4.42); whereas PKR, LVEF, and cardiac index demonstrated no associations. When SMII and PKR were incorporated into a EuroSCORE II risk model, predictive performance improved (net reclassification index improvement 0.457; p = 0.001); whereas a model incorporating LVEF and cardiac index demonstrated no improvement (0.130; p = 0.318).

CONCLUSION

The present study demonstrated that SMII, but not PKR, as a measure of cardiac function was associated with major complications. The study's data may guide investigations of more suitable perioperative goal-directed therapies to reduce complications after cardiac surgery.

Evaluation of hemodynamics in healthy term neonates using ultrasonic cardiac output monitor

BACKGROUND

Transition from intrauterine to extrauterine life is a critical phase during which several changes occur in cardiovascular system. In clinical practice, it is important to have a method that allows an easy, rapid and precise evaluation of hemodynamic status of a newborn for clinical management. We here propose a rapid, broadly applicable method to monitor cardiovascular function using ultrasonic cardiac output monitoring (USCOM).

METHODS

We here present data obtained from a cohort of healthy term newborns (n = 43) born by programmed cesarean section at Fondazione MBBM, Ospedale San Gerardo. Measurements were performed during the first hour of life, then at 6 + 2, at 12-24, and 48 h of life. We performed a screening echocardiography to identify a patent duct at 24 h and, if patent, it was repeated at 48 h of life.

RESULTS

We show that physiologically, during the first 48 h of life, blood pressure and systemic vascular resistance gradually increase, while there is a concomitant reduction in stroke volume, cardiac output, and cardiac index. The presence of patent ductus arteriosus significantly reduces cardiac output (p = 0.006) and stroke volume (p = 0.023). Furthermore, newborns born at 37 weeks of gestational age display significantly lower cardiac output (p < 0.001), cardiac index (p = 0.045) and stroke volume (p < 0.001) compared to newborns born at 38 and ≥ 39 weeks. Finally, birth-weight (whether adequate, small or large for gestational age) significantly affects blood pressure (p = 0.0349), stroke volume (p < 0.0001), cardiac output (p < 0.0001) and cardiac index (p = 0.0004). In particular, LGA infants display a transient increase in cardiac index, cardiac output and stroke volume up to 24 h of life; showing a different behavior from AGA and SGA infants.

CONCLUSIONS

Compared to previous studies, we expanded measurements to longer time-points and we analyzed the impact of commonly used clinical variables on hemodynamics during transition phase thus making our data clinically applicable in daily routine. We calculate reference values for each population, which can be of clinical relevance for quick bedside evaluation in neonatal intensive care unit.

Measurement of inotropy and systemic oxygen delivery in term, low- and very-low-birth-weight neonates using the Ultrasonic Cardiac Output Monitor (USCOM)

Background The aim of this study was to assess the normal values of the Smith-Madigan inotropy index (SMII) and oxygen delivery index (DO2I) in low-birth-weight (LBW) and very-low-birth-weight (VLBW) newborns on the first 3 days of life, and to identify how different degrees of maturity influence cardiovascular alterations during the transitional period compared with term neonates. Methods Twenty-eight VLBW newborns, 46 LBW newborns and 50 normal full-term newborns admitted to our department were studied. Hemodynamics of the left heart were measured in all neonates over the first 3 days using the Ultrasonic Cardiac Output Monitor (USCOM). This was combined with hemoglobin concentration and pulse oximetry to calculate DO2I. Blood pressure was combined with the hemodynamic measures and hemoglobin concentration to calculate SMII. Results SMII showed statistically significant differences among the three groups (VLBW 0.48 ± 0.11; LBW 0.54 ± 0.13; term 0.69 ± 0.17 W/m2 P < 0.001), which was in line with the following myocardial parameters: stroke volume index (SVI) and cardiac index (CI) (P < 0.001 and <0.001). For systemic oxygen delivery (DO2) parameters, significant differences were found for DO2I (P < 0.001) while hemoglobin concentration and pulse oximetry demonstrated no significant differences. In the VLBW group, SMII and DO2I showed no significant change over the 3 days. Conclusion Normal inotropy and systemic DO2I values in VLBW neonates over the first 3 days of life were assessed. SMII and DO2I were significantly lower in VLBW neonates during the first 72 h of life. With increasing birth weight, higher myocardial inotropy and DO2 were found. The addition of USCOM examination to standard neonatal echocardiography may provide further important information regarding cardiac function.

Understanding the Haemodynamics of Hypertension

PURPOSE OF REVIEW

This article introduces the haemodynamic principles that underpin the pathophysiology of hypertension and introduces a rational physiological approach to appropriate pharmacologic treatment.

RECENT FINDINGS

Outdated understanding of haemodynamics based on previous measurement systems can no longer be applied to our understanding of the circulation. We question the current view of hypertension as defined by a predominantly systolic blood pressure and introduce the concept of vasogenic, cardiogenic and mixed-origin hypertension. We postulate that failure to identify the individual's haemodynamic pattern may lead to the use of inappropriate medication, which in turn may be a major factor in patient non-compliance with therapeutic strategies. A population-based approach to treatment of hypertension may lead to suboptimal functional dynamics in the individual patient. Finally, we question the validity of current guidelines and published evidence relating morbidity and mortality to the future treatment of hypertension. The importance of individual haemodynamic profiles may be pivotal in the understanding, diagnosis and treatment of hypertension if optimal control with minimal adverse effects is to be achieved. Research based on individual haemodynamic patterns is overdue.

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.

[Application of ultrasonic cardiac output monitor in evaluation of cardiac function in children with severe pneumonia]

OBJECTIVE

To study the clinical application of ultrasonic cardiac output monitor (USCOM) in evaluation of cardiac function in children with severe pneumonia.

METHODS

Twenty-nine children with severe pneumonia were enrolled in the observation group and forty-three children with common pneumonia were enrolled in the control group. The USCOM was used to measure the cardiac function indices in the two groups. The results were compared between the two groups. The changes in cardiac function indices after treatment were evaluated in the observation group.

ESULTS

The observation group had a significantly higher heart rate and significantly lower cardiac output, systolic volume, and aortic peak velocity than the control group (P<0.05). There were no significant differences in cardiac index or systemic vascular resistance between the two groups (P>0.05). In the observation group, the heart rate, cardiac output, systolic volume, aortic peak velocity, cardiac index, and systemic vascular resistance were significantly improved after treatment (P<0.05).

CONCLUSIONS

The USCOM is a fast, convenient, and accurate approach for dynamic measurement of cardiac function and overall circulation state in children with severe pneumonia. The USCOM can provide a basis for diagnosis, treatment, and evaluation of the disease, which is quite useful in clinical practice.

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.

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

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

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

USCOM-window to the circulation: utility of supra-sternal Doppler in an elderly anaesthetized patient for a robotic cystectomy

Supra-sternal Doppler (USCOM Ltd., Sydney, Australia) can be used during anaesthesia to measure cardiac output (CO) and related flow parameters. However, before the USCOM can be used routinely, its utility and limitations need to be fully understood and critical information about its use disseminated. In "Window to the Circulation" we use the example of an elderly man undergoing major urological robotic surgery to highlight the utility and limitations of intra-operative USCOM use. USCOM readings were verified against oesophageal Doppler. Despite the lack of major blood loss (<500 ml in 8-h), significant changes in haemodynamics were recorded. CO ranged from 3.2 to 8.3 l/min. The quality of USCOM scans and reliability of data was initially poor, but improved as CO increased as surgery progressed. When USCOM scans became acceptable the correlation with oesophageal Doppler was R(2) = 8.0 (p < 0.001). Several characteristic features of the supra-sternal Doppler scans were identified: Aortic and pulmonary flow waves, valve closure, E and A waves, false A-wave and aberrant arterial flow patterns. Their identification helped with identifying the main flow signal across the aortic valve. The USCOM has the potential to monitor changes in CO and related flow parameters intra-operatively and thus help the anaesthetist to more fully understand the patient's haemodynamics. However, achieving a good quality scan is important as it improves the reliability of USCOM data. The supra-sternal route is rich in flow signals and identifying the aortic valve signal is paramount. Recognizing the other characteristic waveforms in the signal helps greatly.

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.