Clinical evaluation of USCOM ultrasonic cardiac output monitor in cardiac surgical patients in intensive care unit

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.

Is Maternal Cardiovascular Performance Impaired in Altitude-Associated Fetal Growth Restriction?

Mundo, William, Lilian Toledo-Jaldin, Alexandrea Heath-Freudenthal, Jaime Huayacho, Litzi Lazo-Vega, Alison Larrea-Alvarado, Valquiria Miranda-Garrido, Rodrigo Mizutani, Lorna G. Moore, Any Moreno-Aramayo, Richard Gomez, Patricio Gutierrez, and Colleen G. Julian. Is maternal cardiovascular performance impaired in altitude-associated fetal growth restriction? High Alt Med Biol. 23:352-360, 2022. Introduction: The incidence of fetal growth restriction (FGR) is elevated in high-altitude resident populations. This study aims to determine whether maternal central hemodynamics during the last trimester of pregnancy are altered in high-altitude FGR. Methods: In this cross-sectional study of maternal-infant pairs (FGR, n = 27; controls, n = 26) residing in La Paz, Bolivia, maternal heart rate, cardiac output (CO), stroke volume, and systemic vascular resistance (SVR) were assessed using continuous-wave Doppler ultrasound. Transabdominal Doppler ultrasound was used for uterine artery (UtA) resistance indices and fetal measures. Maternal venous soluble fms-like tyrosine kinase-1 (sFlt1) levels were measured. Results: FGR pregnancies had reduced CO, elevated SVR and UtA resistance, fetal brain sparing, and increased maternal sFlt1 versus controls. Maternal SVR was positively associated with UtA resistance and inversely associated with middle cerebral artery resistance and birth weight. Maternal sFlt1 was greater in FGR than controls and positively associated with UtA pulsatility index. Women with elevated sFlt1 levels also tended to have lower CO and higher SVR. Conclusion: Noninvasive assessment of maternal cardiovascular function may be an additional method for detecting high-risk pregnancies at high altitudes, thereby informing the need for increased surveillance and appropriate allocation of resources to minimize adverse outcomes.

Optimization of the target strategy of perioperative infusion therapy based on monitoring data of central hemodynamics in order to prevent complications

Enhanced Recovery After Surgery (ERAS) protocols are increasingly used in the perioperative period around the world. The concept of goal-directed fluid therapy (GDT) is a key element of the ERAS protocols. Inadequate perioperative infusion therapy can lead to a number of complications, including the development of an infectious process, namely surgical site infections, pneumonia, urinary tract infections. Optimal infusion therapy is difficult to achieve with standard parameters (e.g., heart rate, blood pressure, central venous pressure), so there are various methods of monitoring central hemodynamics - from invasive, minimally invasive to non-invasive. The latter are increasingly used in clinical practice. The current evidence base shows that perioperative management, specifically the use of GDT guided by real-time, continuous hemodynamic monitoring, helps clinicians maintain a patient's optimal fluid balance. The manuscript presents the analytical data, which describe the benefits and basic principles of perioperative targeted infusion therapy based on central hemodynamic parameters to reduce the risk of complications.

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.

Effects of Performing Applied Muscle Tension during Recovery after Phlebotomy in Young, First-Time Donors: A Pilot Study

Vasovagal reaction (VVR) compromises donor safety and reduces the subsequent return rates. Performing applied muscle tension (AMT) during phlebotomy may reduce the incidence of VVR. However, the effectiveness of performing AMT after phlebotomy to reduce delayed VVR remains unclear. With ethics approval, 12 young, first-time donors (YFTD) were recruited to study the effects on stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) while performing AMT from needle insertion to end of recovery. Measurements from 12 matched control YFTD were used for comparison. Pre-donation anxiety and VVR severity were assessed. Compared to controls, donors who performed AMT had higher SV (Control: 57 mL vs. AMT: 69 mL, p = 0.045), higher CO (Control: 3.7 L·min⁻¹ vs. AMT: 5.2 L·min⁻¹, p = 0.006) and lower SVR (Control: 1962 dyn·s·cm⁻⁵ vs. AMT: 1569 dyn·s·cm⁻⁵, p = 0.032) during mid-phlebotomy. During recovery, the AMT group retained higher SV, higher CO and lower SVR than the control, but not reaching statistical significance. Practicing AMT during recovery resulted in sustained haemodynamic improvements beyond the donation period, despite the reduction in delayed VVR was insignificant compared to the control group. A larger sample size is needed to validate the effectiveness of performing AMT after donation to mitigate delayed VVR.

Ultrasound Cardiac Output Monitor (USCOM™) Measurements Prove Unreliable Compared to Cardiac Magnetic Resonance Imaging in Adolescents with Cardiac Disease

The purpose of this stuy is to prospectively assess the reliability of the ultrasound cardiac output monitor (USCOM™) for measuring stroke volume index and predicting left ventricular outflow tract diameter in adolescents with heart disease. Sixty consecutive adolescents with heart disease attending a tertiary medical center underwent USCOM™ assessment immediately after cardiac magnetic resonance imaging. USCOM™ measured stroke volume index and predicted left ventricular outflow tract diameter were compared to cardiac magnetic resonance imaging-derived values using Bland-Altman analysis. Ten patients with an abnormal left ventricular outflow tract were excluded from the analysis. An adequate USCOM™ signal was obtained in 49/50 patients. Mean stroke volume index was 46.1 ml/m² by the USCOM™ (range 22-66.9 ml/m²) and 42.9 ml/m² by cardiac magnetic resonance imaging (range 24.7-59.9 ml/m²). The bias (mean difference) was 3.2 ml/m²; precision (± 2SD of differences), 17 ml/m²; and mean percentage error, 38%. The mean (± 2SD) left ventricular outflow tract diameter was 0.445 ± 0.536 cm smaller by the USCOM™ algorithm prediction than by cardiac magnetic resonance imaging. Attempted adjustment of USCOM™ stroke volume index using cardiac magnetic resonance imaging left ventricular outflow tract diameter failed to improve agreement between the two modalities (bias 28.4 ml/m², precision 44.1 ml/m², percentage error 77.3%). Our study raises concerns regarding the reliability of USCOM™ for stroke volume index measurement in adolescents with cardiac disease, which did not improve even after adjusting for its inaccurate left ventricular outflow tract diameter prediction.

USER Protocol as a Guide to Resuscitation of the Patient with Septic Shock in the Emergency Department

Introduction

Sepsis is a disease that is still associated with high mortality, in which timely interventions are related to better results.

Objective

To determine if there is a difference in in-hospital mortality, fluid balances, norepinephrine initiation and recovery time of blood pressure, when comparing the resuscitation of the patient who is admitted to the emergency room in septic shock by applying the ultrasound protocol (USER) versus the standard of care.

Patients and Methods

This is a prospective, cohort study conducted in the emergency room of a highly complex hospital of patients with septic shock.

Results

83 patients recruited in total. The groups were comparable in demographics, mean baseline blood pressure, disease severity given by the SOFA value, and arterial lactate. A statistically significant difference was documented in the fluid balances at 4 hours, median 1325mL (IQR:451–2455mL) in Group C versus 900mL (IQR:440–1292) in Group U (p=0.048) and at 6 hours, median 1658mL (IQR:610–2925mL) versus 1107mL (IQR:600–1500mL), p=0.026, as well as in the total fluid balance of hospital stay, median 14,564mL (IQR:8660–18,705mL) versus 8660mL (IQR:5309–16,974mL), p=0.049. On the other hand, in the USER Group, the mean blood pressure ≥ 65mmHg was achieved in 97.4% of the patients 4 hours after the start of the protocol versus 50% in Group C (p=<0.001). Mortality with the use of the protocol compared with conventional therapy was (56.4% vs 61.36%, p=0.647).

Conclusion

The use of the USER protocol in patients with septic shock in the emergency room showed lower fluid balances at 4 and 6 hours, and of the total hospital stay, as well as earlier initiation of norepinephrine and statistically significant faster improvement in blood pressure. Although a statistically significant difference was not found in the days of ICU stay, hospitalization and in-hospital mortality, a trend was observed in the reduction of these parameters.

Treatment of pregnancies complicated by intrauterine growth restriction with nitric oxide donors increases placental expression of Epidermal Growth Factor-Like Domain 7 and improves fetal growth: A pilot study

Intrauterine growth restriction (IUGR) is a pathological condition of pregnancy with high perinatal mortality and morbidity, characterized by inadequate fetal growth associated to altered maternal hemodynamics with impaired uteroplacental blood flow and placental insufficiency. To date, iatrogenic premature delivery remains the elective therapeutic strategy. However, in recent years the possibility of a therapeutic approach with vasodilators and myorelaxants, such as nitric oxide (NO) donors, has gained interest. NO controls many endothelial cell functions, including angiogenesis and vascular permeability, by regulating the expression of angiogenic factors, such as Vascular Endothelial Growth Factor. In the present study, we investigated if treatment of pregnancies complicated by IUGR with NO donors affects the expression of Epidermal Growth Factor-Like Domain 7 (EGFL7), a secreted endothelial factor, previously demonstrated to be expressed by both endothelial and trophoblast cells and involved in proper placental development. NO donor treatment induced placental levels of EGFL7 and, in association with oral fluids, significantly improved fetal growth. Ex vivo experiments confirmed that NO donors increased expression and secretion of EGFL7 by villous explants. To specifically investigate the potential response of trophoblast cells to NO, we treated HTR8-sVneo cells with NO donors and observed induction of EGFL7 expression. Altogether, our findings indicate that NO induces endothelial and trophoblast expression of EGFL7 in the placenta and improves fetal growth, suggesting a correlation between placental levels of EGFL7 and pregnancy outcome.

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

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

Maternal haemodynamic function differs in pre-eclampsia when it is associated with a small-for-gestational-age newborn: a prospective cohort study

OBJECTIVE

To describe maternal haemodynamic differences in gestational hypertension with small-for-gestational-age babies (HDP + SGA), gestational hypertension with appropriate-for-gestational-age babies (HDP-only) and control pregnancies.

DESIGN

Prospective cohort study.

SETTING

Tertiary Hospital, UK.

POPULATION

Women with gestational hypertension and healthy pregnant women.

METHODS

Maternal haemodynamic indices were measured using a non-invasive Ultrasound Cardiac Output Monitor (USCOM-1A^® ) and corrected for gestational age and maternal characteristics using device-specific reference ranges.

MAIN OUTCOME MEASURES

Maternal cardiac output, stroke volume, systemic vascular resistance.

RESULTS

We included 114 HDP + SGA, 202 HDP-only and 401 control pregnancies at 26-41 weeks of gestation. There was no significant difference in the mean arterial blood pressure (110 versus 107 mmHg, P = 0.445) between the two HDP groups at presentation. Pregnancies complicated by HDP + SGA had significantly lower median heart rate (76 versus 85 bpm versus 83 bpm), lower cardiac output (0.85 versus 0.98 versus 0.97 MoM) and higher systemic vascular resistance (1.4 versus 1.0 versus 1.2 MoM) compared with control and HDP-only pregnancies, respectively (all P < 0.05).

CONCLUSION

Women with HDP + SGA present with more severe haemodynamic dysfunction than HDP-only. Even HDP-only pregnancies exhibit impaired haemodynamic indices compared with normal pregnancies, supporting a role of the maternal cardiovascular system in gestational hypertension irrespective of fetal size. Central haemodynamic changes may play a role in the pathogenesis of pre-eclampsia and should be considered alongside placental aetiology.

TWEETABLE ABSTRACT

Hypertensive disorders of pregnancy are associated with worse maternal haemodynamic function when associated with small-for-gestational-age birth.

Performance evaluation of a portable bioimpedance cardiac output monitor for measuring hemodynamic changes in athletes during a head-up tilt test

The use of impedance cardiography to monitor physiological changes in sports is rarely reported. Using head-up tilt test, we evaluated a portable noninvasive impedance cardiography device (PhysioFlow) by comparing it with a reference Doppler monitor (USCOM). Accuracy in tracking hemodynamic changes deteriorated with higher tilt, implying a gravitational influence on its performance. Stroke volume measurements were overestimated, but the changes were underestimated. Despite its convenient physical features, the suitability of PhysioFlow for sports use is questionable.

Cardiac output monitoring: Technology and choice

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

Are maternal hemodynamic indices markers of fetal growth restriction in pregnancies with a small-for-gestational-age fetus?

OBJECTIVE

Pregnancies complicated by fetal growth restriction (FGR) have a worse outcome than those with a small-for-gestational-age (SGA) fetus. There is increasing evidence of a maternal cardiovascular role in the pathophysiology of FGR. We aimed to compare maternal hemodynamic indices between pregnancies complicated by FGR and those delivering a SGA neonate, using a non-invasive device.

METHODS

This was a prospective study of normotensive pregnancies complicated by FGR (defined as estimated fetal weight (EFW) < 3^rd centile or Doppler evidence of impaired placental-fetal blood flow), those with a SGA fetus (defined as EFW < 10^th centile) and control pregnancies with an appropriately grown fetus. Assessment of maternal hemodynamics (heart rate (HR), cardiac output (CO), mean arterial pressure (MAP), systemic vascular resistance (SVR) and stroke volume) was performed using a non-invasive device (USCOM-1A®). Uterine artery (UtA) pulsatility index (PI) was measured using transabdominal ultrasound. Hemodynamic variables that are affected by gestational age and maternal characteristics were corrected for using device-specific reference ranges. Comparison between groups was performed using the chi-square test or the Mann-Whitney U-test, as appropriate.

RESULTS

A total of 102 FGR, 64 SGA and 401 control pregnancies, with a median gestational age of 36 weeks, were included in the analysis. Women with a pregnancy complicated by FGR and those with a SGA fetus were shorter and weighed less than did controls. Compared with controls, the FGR group had significantly lower median maternal HR (80 beats per min (bpm) vs 85 bpm; P = 0.001) and CO multiples of the median (MoM; 0.91 vs 0.98; P = 0.003), and higher median maternal MAP (90 mmHg vs 87 mmHg; P = 0.040), SVR MoM (1.2 vs 1.0; P < 0.001) and UtA-PI MoM (1.1 vs 0.96; P < 0.001), but there was no significant difference in stroke volume MoM (1.0 vs 0.98; P = 0.647). Compared with the SGA group, the FGR group had a significantly lower median HR (80 bpm vs 87 bpm; P = 0.022), and higher median maternal MAP (90 mmHg vs 85 mmHg; P = 0.025), SVR MoM (1.2 vs 1.0; P = 0.002) and UtA-PI MoM (1.1 vs 0.98; P = 0.005), but there was no significant difference in CO MoM (0.91 vs 0.96; P = 0.092) or stroke volume MoM (1.0 vs 1.0; P = 0.806). There were no significant differences in adjusted maternal hemodynamic indices between the SGA group and controls.

CONCLUSION

Pregnancies complicated by FGR presented with impaired maternal hemodynamic function, as evidenced by lower HR and CO, as well as higher MAP, SVR and UtA resistance. Pregnancies delivering a SGA neonate, without evidence of FGR, had normal maternal hemodynamic function. Maternal hemodynamic indices may therefore be of value in distinguishing FGR from SGA pregnancies. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

[Meta-analyses on measurement precision of non-invasive hemodynamic monitoring technologies in adults]

An ideal non-invasive monitoring system should provide accurate and reproducible measurements of clinically relevant variables that enables clinicians to guide therapy accordingly. The monitor should be rapid, easy to use, readily available at the bedside, operator-independent, cost-effective and should have a minimal risk and side effect profile for patients. An example is the introduction of pulse oximetry, which has become established for non-invasive monitoring of oxygenation worldwide. A corresponding non-invasive monitoring of hemodynamics and perfusion could optimize the anesthesiological treatment to the needs in individual cases. In recent years several non-invasive technologies to monitor hemodynamics in the perioperative setting have been introduced: suprasternal Doppler ultrasound, modified windkessel function, pulse wave transit time, radial artery tonometry, thoracic bioimpedance, endotracheal bioimpedance, bioreactance, and partial CO₂ rebreathing have been tested for monitoring cardiac output or stroke volume. The photoelectric finger blood volume clamp technique and respiratory variation of the plethysmography curve have been assessed for monitoring fluid responsiveness. In this manuscript meta-analyses of non-invasive monitoring technologies were performed when non-invasive monitoring technology and reference technology were comparable. The primary evaluation criterion for all studies screened was a Bland-Altman analysis. Experimental and pediatric studies were excluded, as were all studies without a non-invasive monitoring technique or studies without evaluation of cardiac output/stroke volume or fluid responsiveness. Most studies found an acceptable bias with wide limits of agreement. Thus, most non-invasive hemodynamic monitoring technologies cannot be considered to be equivalent to the respective reference method. Studies testing the impact of non-invasive hemodynamic monitoring technologies as a trend evaluation on outcome, as well as studies evaluating alternatives to the finger for capturing the raw signals for hemodynamic assessment, and, finally, studies evaluating technologies based on a flow time measurement are current topics of clinical research.

Cardiac output measurements via echocardiography versus thermodilution: A systematic review and meta-analysis

Echocardiography, as a noninvasive hemodynamic evaluation technique, is frequently used in critically ill patients. Different opinions exist regarding whether it can be interchanged with traditional invasive means, such as the pulmonary artery catheter thermodilution (TD) technique. This systematic review aimed to analyze the consistency and interchangeability of cardiac output measurements by ultrasound (US) and TD. Five electronic databases were searched for studies including clinical trials conducted up to June 2019 in which patients’ cardiac output was measured by ultrasound techniques (echocardiography) and TD. The methodological quality of the included studies was evaluated by two independent reviewers who used the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2), which was tailored according to our systematic review in Review Manager 5.3. A total of 68 studies with 1996 patients were identified as eligible. Meta-analysis and subgroup analysis were used to compare the cardiac output (CO) measured using the different types of echocardiography and different sites of Doppler use with TD. No significant differences were found between US and TD (random effects model: mean difference [MD], -0.14; 95% confidence interval, -0.30 to 0.02; P = 0.08). No significant differences were observed in the subgroup analyses using different types of echocardiography and different sites except for ascending aorta (AA) (random effects model: mean difference [MD], -0.37; 95% confidence interval, -0.74 to -0.01; P = 0.05) of Doppler use. The median of bias and limits of agreement were -0.12 and ±0.94 L/min, respectively; the median of correlation coefficient was 0.827 (range, 0.140–0.998). Although the difference in CO between echocardiography by different types or sites and TD was not entirely consistent, the overall effect of meta-analysis showed that no significant differences were observed between US and TD. The techniques may be interchangeable under certain conditions.

USCOM (Ultrasonic Cardiac Output Monitors) Lacks Agreement with Thermodilution Cardiac Output and Transoesophageal Echocardiography Valve Measurements

The USCOM (Ultrasonic Cardiac Output Monitors) device is a noninvasive cardiac output monitor, which utilises transaortic or transpulmonary Doppler flow tracing and valve area estimated using patient height to determine cardiac output. We evaluated USCOM against thermodilution cardiac outputs and transoesophageal echocardiography valve area measurements in 22 ASA PS4 cardiac surgical patients. Data collection commenced following pulmonary artery catheter insertion, with cardiac output measurements repeated after sternotomy closure. Failure to obtain transaortic Doppler readings using USCOM occurred in 5% of planned measurements. USCOM transaortic analysis was not planned for 11 patients with known aortic disease. Bias at the aortic window (n = 20) was -0.79 l/min with limits of agreement from -3.66 to 2.08 l/min. At the pulmonary window, failure to obtain Doppler readings occurred in 24% of planned measurements. Bias at the pulmonary window (n=36) was -0.17 l/min with limits of agreement from -3.30 to 2.97 l/min. The USCOM estimates of valve area based on height showed poor correlation with the echocardiographic measurements of aortic and pulmonary valves (r=0.57 and r=0.17, respectively). It was concluded that USCOM showed poor agreement with thermodilution. The estimated valve area was identified as one source of error.

Maternal hemodynamics in normal pregnancy: reference ranges and role of maternal characteristics

OBJECTIVES

The main aim of this study was to construct reference ranges of maternal central hemodynamic parameters during pregnancy. The second aim was to determine the maternal and pregnancy characteristics that influence these hemodynamic parameters.

METHODS

This was a prospective cohort study of low-risk pregnant women attending for routine antenatal care at St George's Hospital, London, UK. Exclusion criteria included any medical disorder present at the time of study recruitment, or development of hypertension or intrauterine fetal growth restriction following study recruitment. Stroke volume (SV), cardiac output (CO) and systemic vascular resistance (SVR) were obtained using non-invasive cardiac output monitoring (USCOM-1A®). USCOM-1A utilizes a non-imaging probe in the suprasternal notch to obtain velocity-time integrals of transaortic blood flow at the left ventricular outflow tract. Once the distribution of the data with respect to gestational age had been determined, maternal characteristics were added to the model to test whether they provided a significant improvement in the prediction of the median value.

RESULTS

The study included 627 women with a singleton pregnancy. The estimated median CO was constant for a maternal age above 32 years, but was around 0.5 L/min higher for women aged ≤ 25 years (P < 0.001). Maternal weight (P < 0.001) and height (P < 0.001) significantly affected CO values and there was a significant interaction (P = 0.002) between them. In women with a height of less than 1.60 m, there was no association between median CO and weight; however, in those with a height exceeding 1.60 m, an increase in weight was associated with an increase in CO. SV was primarily associated with height (P < 0.001), although some positive association with weight (P < 0.001) could also be observed within the normal body-mass-index range. Greater height (P < 0.001) was associated with lower median values of SVR, with an estimated difference of around 120 dynes × s/cm⁵ between 1.60 m and 1.80 m. Advancing maternal age was associated with higher median SVR, with an estimated difference of around 50 dynes × s/cm⁵ between 25 and 35 years. Smokers had a lower SVR by 73.5 (95% CI, 8.6-138.4) dynes × s/cm⁵ .

CONCLUSION

Maternal hemodynamics are influenced significantly by maternal age, height and weight. We provide USCOM-1A-specific reference ranges and a calculator for SV, CO and SVR in uncomplicated pregnancies that correct for maternal age, height and weight. This should enable clinical application and comparison in both uncomplicated and pathological pregnancies. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Effect of a nitric oxide donor on maternal hemodynamics in fetal growth restriction

OBJECTIVE

To evaluate the effect on maternal cardiovascular parameters of treatment with a nitric oxide (NO) donor and plasma volume expansion in pregnancies complicated by fetal growth restriction (FGR).

METHODS

Twenty-six pregnant women with a diagnosis of FGR were treated with transdermal patches of a NO donor and plasma volume expansion by co-administration of oral fluids. We compared the treated group to a historical control group of untreated FGR patients. Hemodynamic indices were obtained using the UltraSonic Cardiac Output Monitor system.

RESULTS

At diagnosis, the two groups were similar in terms of maternal and hemodynamic characteristics. In the treated group, we found a significant increase in maternal cardiac output and stroke volume and a decrease in systemic vascular resistance after 2 weeks of therapy. No significant differences were found 2 weeks after diagnosis in the untreated group. The treated group delivered infants with higher birth-weight centile than did the untreated control group.

CONCLUSIONS

The combined therapeutic approach of NO donor administration and plasma volume expansion in FGR apparently improves significantly maternal hemodynamic indices. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

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.

Comparison of bioreactance non-invasive cardiac output measurements with cardiac magnetic resonance imaging

Impedance cardiography measurement of cardiac output gained wide interest due to its ease of use and non-invasiveness. However, validation studies of different algorithms yielded diverging results. Bioreactance (BR) as a recent adaption differs fundamentally as the flow signal is derived from phase shifts. Our aim was to assess the accuracy and reproducibility of BR, as compared to the non-invasive gold standard--cardiac magnetic resonance imaging (CMR). We prospectively included 32 stable patients. BR was performed twice in the supine position and averaged over 30 seconds. Mean bias was 0.2 ± 1.8 l/minute (1 ± 28%, percentage error 55%) with limits of agreement ranging from  -3.4 to 3.7 l/minute. Reproducibility was acceptable with a mean bias of 0.1 ± 0.9 l/minute (1 ± 14%, 27%). Low cardiac output was significantly overestimated (-1.1 ± 1.5 l/minute), while high cardiac output was underestimated (1.5 ± 1.7 l/minute), (P=0.001), although reproducibility was unaffected. Bias and weight were moderately correlated in men (r = 0.50, P=0.02). No differences for accuracy were found in nine patients who had an arrhythmia (0.3 ± 1.4 versus 0.1 ± 2.0 l/minute, P=0.76), while clinically relevant differences were found in patients with mild aortic valve disease (1.9 ± 2.2 versus -0.3 ± 1.7 l/minute, P=0.02). Overall, BR showed insufficient agreement with CMR, overestimating low and underestimating high cardiac output states. Reproducibility was acceptable and not negatively affected by the circulatory condition. Consequently, absolute values acquired with BR should be interpreted with caution and must not be used interchangeably in clinical practice.

Does stroke volume variation predict fluid responsiveness in children: A systematic review and meta-analysis

OBJECTIVE

Stroke volume variation (SVV) is a reliable predictor of fluid responsiveness in adult patients. However, the predictive value of SVV is uncertain in pediatric patients. We performed the first systematic meta-analysis to evaluate the diagnostic value of SVV in predicting fluid responsiveness in children.

METHODS

PUBMED, EMBASE, and Cochrane Central Register of Controlled Trials were searched up to December 2016. Original studies assessing the diagnostic accuracy of SVV in predicting fluid responsiveness in children were considered to be eligible. A random-effects model was used to calculate pooled values of sensitivity, specificity and diagnostic odds ratio with 95% CI. The summary receiver operating characteristic curve was estimated and area under the curve was calculated. Quality of the studies was assessed with the QUADAS-2 tool.

RESULTS

Six studies with a total of 279 fluid boluses in 224 children were included. The analysis demonstrated a pooled sensitivity of 0.68 (95% CI,0.59-0.76), pooled specificity of 0.65 (95% CI, 0.57-0.73), pooled diagnostic odds ratio of 8.24 (95% CI, 2.58-26.30), and the summary area under the summary receiver operating characteristic curve of 0.81. However, significant inter-study heterogeneity was found (p<0.05, I2 = 61.3%), likely due to small sample size and diverse study characteristics.

CONCLUSIONS

Current evidence suggests that SVV was of diagnostic value in predicting fluid responsiveness in children under mechanical ventilation. Given the high heterogeneity of published data, further studies are needed to confirm the diagnostic accuracy of SVV in predicting fluid responsiveness in pediatric patients.

Relationship between maternal hemodynamics and plasma natriuretic peptide concentrations during pregnancy complicated by preeclampsia and fetal growth restriction

OBJECTIVE

A proper maternal cardiovascular adaptation to the pregnancy plays a key role for promoting an adequate uteroplacental perfusion, for ensuring normal fetal development and for preventing gestational hypertensive complications such as preeclampsia. This study aims to evaluate hemodynamic measurements obtained by noninvasive methods among preclamptic women with and without fetal growth restriction (FGR) and the relationship with plasma levels of natriuretic peptides.

STUDY DESIGN

The study compared 98 pregnant women (n=48 with preeclampsia; n=50 normotensive pregnant women) and 50 nonpregnant normotensive control subjects undergoing anultrasonic cardiac output monitor (USCOM) and plasma assessment of atrial N-terminal pro B-type natriuretic peptide (NT-proBNP). The statistical analysis was carried out by analysis of variance and correlation analysis.

RESULTS

Preeclampsia state is associated with increased vascular resistance (mean 1587±236 vs 978±153 dyn s cm^-3) and lower cardiac output (mean 5.7±1.1 vs 6.78±0.8 l) and this hemodynamic state is associated with higher levels of NT-proBNP (mean 121.2±26.3 vs 42.5±11.4 pg ml^-1); furthermore, we found an inverse correlation between maternal cardiac output and plasma levels of NT-proBNP only if preeclampsia is associated with FGR.

CONCLUSION

The elevated NT-proBNP in preeclampsia may reflect ventricular stress and subclinical cardiac dysfunction worsening if FGR is present. This may have implications for the acute management of the preeclampsia and FGR women and for appropriately timed therapeutic interventions later in life.

Cardiac output assessment in pregnancy: comparison of two automated monitors with echocardiography

OBJECTIVE

To compare non-invasive hemodynamic measurements obtained in pregnant and postpartum women using two automated cardiac output monitors against those obtained by two-dimensional (2D) transthoracic echocardiography (TTE).

METHODS

This was a cross-comparison study into which we recruited 114 healthy women, either with normal singleton pregnancy (across all three trimesters) or within 72 hours following delivery. Cardiac output estimations were obtained non-invasively using two different monitors, Ultrasound Cardiac Output Monitor (USCOM®, which uses continuous-wave Doppler analysis of transaortic blood flow) and Non-Invasive Cardiac Output Monitor (NICOM®, which uses thoracic bioreactance), and 2D-TTE. The performance of each monitor was assessed relative to that of TTE by calculating bias, precision, 95% limits of agreement and mean percentage difference (MPD). Intraobserver repeatability was assessed for both monitors and interobserver reproducibility was assessed for USCOM, NICOM being operator-independent.

RESULTS

Following exclusions due to poor-quality results of a monitor or TTE, or for medical reasons, our analysis included 98 women (29 in the first trimester, 25 in the second and 21 in the third, and 23 postpartum). For cardiac output estimation, when compared with TTE, USCOM had a bias ranging from 0.4 to 0.9 L/min. The MPD of USCOM was 29% in the third-trimester cohort. NICOM had a bias ranging from -1.0 to 0.6 L/min, with a MPD of 32% in the third-trimester group. There was limited agreement between the cardiac output monitors and TTE in the first and second trimesters, with a MPD of 38% for USCOM in both first and second trimesters, and 71% and 61% for NICOM in first and second trimesters, respectively. For cardiac output estimation using USCOM, we found excellent intraobserver repeatability (intraclass correlation coefficient (ICC), 0.97; 95% CI, 0.95-0.98) and interobserver reproducibility (ICC, 0.90; 95% CI, 0.81-0.94), and the repeatability for NICOM was comparable (ICC, 0.95; 95% CI, 0.93-0.97).

CONCLUSIONS

We found good agreement of both USCOM and NICOM when compared with 2D-TTE, specifically in the third trimester of pregnancy. Both devices had good intraobserver repeatability and either had good interobserver reproducibility or were operator-independent. Future studies should take into account the significant differences in the precise maternal hemodynamic values obtained by these devices, and consider developing device-specific reference ranges in pregnancy and the postpartum period. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Preterm delivery and elevated maternal total vascular resistance: signs of suboptimal cardiovascular adaptation to pregnancy?

OBJECTIVE

To evaluate the maternal hemodynamic profile in women with a diagnosis of threatened preterm delivery (TPD) in order to understand the possible pathophysiologic mechanism leading to an increased lifetime risk for future cardiovascular disease.

METHODS

Patients with a diagnosis of TPD were enrolled and assessed using a non-invasive method (USCOM^® ) for the determination of hemodynamic parameters. Vaginal and rectal swabs were taken, cervical length, blood inflammatory indices, fetal blood-vessel Doppler velocimetry were measured and gestational age at the time of delivery and neonatal outcomes were noted.

RESULTS

A total of 68 patients were enrolled and included in the analysis. The population was divided into two groups according to total vascular resistance (TVR): Group A with a TVR of ≤ 1000 dynes × s/cm⁵ (n = 48) and Group B with a TVR of > 1000 dynes × s/cm⁵ (n = 20). C-reactive protein (CRP) was higher in Group B than in Group A, suggesting a systemic inflammation status. Group B delivered earlier (32 + 4 weeks vs 38 + 2 weeks; P < 0.01) and neonatal outcome was worse than in Group A. Significantly lower values of cardiac output, stroke volume, peak velocity of flow, velocity time integral, minute distance, stroke volume index, cardiac index, stroke work, cardiac power, inotropy index and potential-to-kinetic energy ratio were observed in Group B than in Group A.

CONCLUSIONS

Women with a diagnosis of TPD showing TVR values of > 1000 dynes × s/cm⁵ and elevated levels of CRP are at high risk of preterm delivery. An impaired maternal cardiovascular adaptation during pregnancy in these patients might suggest a possible higher risk for subsequent future cardiovascular disease. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Validation of an Ultrasound Cardiac Output Monitor as a Bedside Tool for Pediatric Patients

The aim of our study was to determine the validity of cardiac output (CO) measurements taken with the ultrasonic cardiac output monitor (USCOM) by comparing to CO measured by pulmonary arterial catheter (PAC) thermodilution during cardiac catheterization. We enrolled thirty-one children (<18 years) undergoing cardiac catheterization in this double-blinded, prospective, observational study. The median CO measured by USCOM was 4.37 L/min (IQR 3.73, 5.60 L/min) compared to 4.28 L/min (IQR 3.52, 5.26 L/min) by PAC thermodilution. The bias (mean difference) between the two methods was 0.2 L/min, and the 95% limits of agreement were -1.2 to 1.6 L/min. The mean percentage error of CO between USCOM and PAC thermodilution was 11%. When excluding a sole outlier, the bias between the two measures decreased to 0.1 L/min (95% limits of agreement -0.6 to 0.9 L/min), and the percentage error was reduced to 8%. The median SVRI measured by USCOM was 22.0 Wood Units (IQR 17.0, 26.8 Wood Units) compared to 22.1 Wood Units (IQR 17.6, 27.4 Wood Units) by PAC thermodilution. Bias (mean difference) between the two methods was -0.6 Wood Units, and the 95% limits of agreement were -8.2 to 6.9 Wood Units. We found that the estimation of CO and by extension SVRI with USCOM is reliable against pulmonary artery catheter thermodilution in children with normal cardiac anatomy. Given the noninvasive nature of USCOM, speed of measurement, and relative ease of use, it may be useful as a bedside tool for pediatric patients.

Less Invasive and Inotrope-Reduction Approach to Automated Closed-Loop Control of Hemodynamics in Decompensated Heart Failure

We have been developing an automated cardiovascular drug infusion system for simultaneous control of arterial pressure (AP), cardiac output (CO), and left atrial pressure (PLA) in decompensated heart failure (HF). In our prototype system, CO and PLA were measured invasively through thoracotomy. Furthermore, the control logic inevitably required use of inotropes to improve hemodynamics, which was not in line with clinical HF guidelines. The goal of this study was to solve these problems and develop a clinically feasible system. We integrated to the system minimally invasive monitors of CO and pulmonary capillary wedge pressure (PCWP, surrogates for PLA) that we developed recently. We also redesigned the control logic to reduce the use of inotrope. We applied the newly developed system to nine dogs with decompensated HF. Once activated, our system started to control the infusion of vasodilator and diuretics in all the animals. Inotrope was not infused in three animals, and infused at minimal doses in six animals that were intolerant of vasodilator infusion alone. Within 50 min, our system controlled AP, CO, and PCWP to their respective targets accurately. Pulmonary artery catheterization confirmed optimization of hemodynamics (AP, from 98 ± 4 to 74 ± 11 mmHg; CO, from 2.2 ± 0.5 to 2.9 ± 0.3 L·min(-1)·m(-2); PCWP, from 27.0 ± 6.6 to 13.8 ± 3.0 mmHg). In a minimally invasive setting while reducing the use of inotrope, our system succeeded in automatically optimizing the overall hemodynamics in canine models of HF. The present results pave the way for clinical application of our automated drug infusion system.

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.

Assessing volume status

Shock is a physiologic state associated with high morbidity and mortality rates. The clinician has several tools available to evaluate volume status. Each modality has its benefits and limitations but, to date, no one test can indicate with 100% accuracy which patients will be truly volume responsive. Although the search for the Holy Grail of a perfect intravascular monitor continues, we must remember the importance of early, aggressive, and goal-directed interventions for patients in shock. Finally, there is no substitute for the most important intervention-the frequent presence of the physician at the patient's bedside.

Optimal management of the critically ill: anaesthesia, monitoring, data capture, and point-of-care technological practices in ovine models of critical care

Animal models of critical illness are vital in biomedical research. They provide possibilities for the investigation of pathophysiological processes that may not otherwise be possible in humans. In order to be clinically applicable, the model should simulate the critical care situation realistically, including anaesthesia, monitoring, sampling, utilising appropriate personnel skill mix, and therapeutic interventions. There are limited data documenting the constitution of ideal technologically advanced large animal critical care practices and all the processes of the animal model. In this paper, we describe the procedure of animal preparation, anaesthesia induction and maintenance, physiologic monitoring, data capture, point-of-care technology, and animal aftercare that has been successfully used to study several novel ovine models of critical illness. The relevant investigations are on respiratory failure due to smoke inhalation, transfusion related acute lung injury, endotoxin-induced proteogenomic alterations, haemorrhagic shock, septic shock, brain death, cerebral microcirculation, and artificial heart studies. We have demonstrated the functionality of monitoring practices during anaesthesia required to provide a platform for undertaking systematic investigations in complex ovine models of critical illness.

Impact of positive end-expiratory pressure on cardiac index measured by ultrasound cardiac output monitor*

OBJECTIVES

To evaluate the impact of different levels of positive end-expiratory pressure on cardiac index in children receiving mechanical ventilation. To explore the effect of lung recruitment on the relationship between positive end-expiratory pressure and cardiac output.

DESIGN

Prospective, single center, and interventional.

SETTING

PICU in a tertiary care children's hospital.

PATIENTS

Fifty mechanically ventilated, hemodynamically stable children between 1 month and 20 years old.

INTERVENTIONS

Positive end-expiratory pressure was altered to levels of 0, 4, 8, and 12 cm H2O in random order. Cardiac output was measured at different levels of positive end-expiratory pressure by continuous wave Doppler ultrasound (ultrasound cardiac output monitor). Baseline vital signs were recorded, as well as cardiac index and dynamic compliance of the respiratory system at each positive end-expiratory pressure level.

MEASUREMENTS AND MAIN RESULTS

Median cardiac index decreased marginally as positive end-expiratory pressure increased, with a median change in cardiac index of 0.4 (< 10%) between positive end-expiratory pressure of 0 and 12 cm H2O (p < 0.001). There was no difference in heart rate or blood pressure as positive end-expiratory pressure increased (p > 0.5). For a subset of 29 patients (58%) in whom the highest dynamic compliance was at a positive end-expiratory pressure of 4 or 8 cm H2O, there was no difference in cardiac index between positive end-expiratory pressure 4 below versus positive end-expiratory pressure at highest dynamic compliance, or cardiac index between positive end-expiratory pressure 4 above versus positive end-expiratory pressure at highest dynamic compliance (p > 0.2). Regardless of optimal dynamic compliance, cardiac index decreased as positive end-expiratory pressure increased (p = 0.02).

CONCLUSIONS

In hemodynamically stable mechanically ventilated children, although there is a statistically significant decrease in cardiac output as positive end-expiratory pressure is increased between 0 and 12 cm H2O, the mean change is less than 10%, and this is likely not clinically significant. In the presence of lung disease, intensive care physicians should feel less reluctant in their use of positive end-expiratory pressure for hemodynamically stable patients.

Elevated positive end-expiratory pressure decreases cardiac index in a rhesus monkey model

RATIONALE

Clinicians are often concerned that higher positive end-expiratory pressure (PEEP) will decrease cardiac index (CI). PEEP affects CI through multiple inter-related mechanisms. The adult Rhesus monkey is an excellent model to study cardiopulmonary interaction due to similar pulmonary and chest wall compliances to human infants.

OBJECTIVE

Our goal was to examine the impact of increasing PEEP on CI in Rhesus monkeys as a model for critically ill children.

METHODS

Prospective, experimental animal study. Nine healthy anesthetized, intubated Rhesus monkeys were allowed to breathe spontaneously at a PEEP of 0, 5, 10, and 15 cm H2O while CI was measured with an ultrasonic Doppler (USCOM).

MEASUREMENTS AND MAIN RESULTS

Cardiac index decreased between PEEP levels of 5 and 15 cm H2O. The mean decrease in CI for the entire cohort of monkeys was 18% (p < 0.01) with a range of -11 to 49%. Stroke volume and oxygen delivery also decreased between PEEP levels of 5 and 15 cm H2O (p < 0.01).

CONCLUSION

Between PEEP levels of 5 and 15 cm H2O, there was a decrease in CI, stroke volume, and oxygen delivery in intubated Rhesus monkeys. A plausible mechanism is that over-distention of normally compliant lungs at increased PEEP resulted in decreased preload to the right ventricle, outweighing the potentially beneficial decrease in left ventricular afterload or pulmonary vascular resistance. Further investigation is warranted, particularly in children with lung injury, who have historically benefited from increased PEEP levels without over-distention.

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.

Less invasive methods of advanced hemodynamic monitoring: principles, devices, and their role in the perioperative hemodynamic optimization

The monitoring of the cardiac output (CO) and other hemodynamic parameters, traditionally performed with the thermodilution method via a pulmonary artery catheter (PAC), is now increasingly done with the aid of less invasive and much easier to use devices. When used within the context of a hemodynamic optimization protocol, they can positively influence the outcome in both surgical and non-surgical patient populations. While these monitoring tools have simplified the hemodynamic calculations, they are subject to limitations and can lead to erroneous results if not used properly. In this article we will review the commercially available minimally invasive CO monitoring devices, explore their technical characteristics and describe the limitations that should be taken into consideration when clinical decisions are made.

Non-invasive assessment of maternal hemodynamics in early pregnancy

OBJECTIVES

Non-invasive assessment of maternal hemodynamics in early pregnancy may be promising in evaluating maternal hemodynamic (mal)adaptation to pregnancy. We explored usage of applanation tonometry and Doppler ultrasound for assessment of cardiac output (CO), systemic vascular resistance (SVR) and arterial stiffness in early pregnancy.

METHODS

Pregnant healthy nulliparous women were studied during first trimester. Radial artery pressure waveform (augmentation index(AIx)), carotid-femoral pulse wave velocity (PWV) and cardiac output (CO) were measured by applanation tonometry (SphygmoCor), electrocardiogram and Doppler ultrasound (USCOM) and related to maternal demographic characteristics and literature concerning advanced pregnancy and non-pregnant subjects.

RESULTS

116 women were studied during gestational age range of 7(+2)-14weeks. Systolic and diastolic central blood pressure were correlated with systolic and diastolic brachial blood pressure respectively. Both measures of arterial stiffness (heart rate corrected AIx(AIx@75) and PWV) were correlated. AIx@75, PWV and SVR were correlated with central mean arterial pressure. CO was negatively correlated with AIx and associated with BMI. PWV was associated with age and BMI, whereas SVR was associated with age.

CONCLUSIONS

Applanation tonometry and Doppler Ultrasound for assessment of maternal hemodynamics in early pregnancy revealed similar associations between different hemodynamic parameters and maternal characteristics as have previously been reported in advanced pregnancy and non-pregnant subjects. The SphygmoCor and the USCOM appear to be reliable methods for the assessment of maternal hemodynamics in early pregnancy. Obtaining a comprehensive hemodynamic profile using these modalities may offer insight in maternal (mal)adaptation to pregnancy. Future work needs to be done relating such measures to pregnancy outcome.

Study to determine the repeatability of supra-sternal Doppler (ultrasound cardiac output monitor) during general anaesthesia: effects of scan quality, flow volume, and increasing age

BACKGROUND

The ultrasound cardiac output monitor (USCOM) is a continuous wave Doppler system designed to measure cardiac output (CO) non-invasively and intermittently either from the pulmonary or from the aortic valve. USCOM scan quality is critical to obtaining reliable data and during anaesthesia it is said to deteriorate with increasing age. The aim of this study was to investigate the effect of age on supra-sternal USCOM scan repeatability during anaesthesia.

METHODS

We performed a series of 6 USCOM scans in 180 patients of all ages after induction for routine surgery. A 12-point Cattermole (CS) score and 10-point insonation (IS) score were used to evaluate scan quality and ease of insonation. The coefficients of variation (CVs) of USCOM variables [CO, peak velocity, stroke volume index (SVI) and the corrected flow time] were derived from the series of six readings.

RESULTS

In >95% of young patients (age <50 yr), it was easy to obtain a good-quality USCOM scan (CS>8). In these patients, repeatability of serial readings was good with CVs<5% and precision of less than ±10%. In older patients (>50 yr), scan quality and ease of insonation declined, with >25% of patients >60 yr having unreliable USCOM scans (CS<5). In these patients, the CV was >5-10%. In several elderly patients (>65 yr), we failed to locate the USCOM signal. Average scan time increased with age (30 to >60 s). SVI was also strongly correlated with scan quality (R(2)=0.77).

CONCLUSIONS

Increasing age has a significant effect on USCOM scan quality and data reliability.

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.

Noninvasive transcutaneous Doppler ultrasound-derived hemodynamic reference ranges in Chinese adolescents

OBJECTIVES

The ultrasonic cardiac output monitor is a noninvasive, quantitative method for measuring and monitoring cardiovascular hemodynamic parameters in patients. The aims of this study were first to establish reference ranges for cardiovascular indices measured by the ultrasonic cardiac output monitor in Chinese children aged 12-18 yr, second to assess the interobserver reliability of the method, and third to compare these ranges with a Caucasian group from Australia.

DESIGN, SETTING, AND SUBJECTS

This was a population-based cross-sectional cohort study of Chinese adolescents 12-18 years old, performed in secondary schools in Hong Kong.

INTERVENTIONS

Ultrasonic cardiac output monitor scans were performed on each subject to measure stroke volume, cardiac output, and systemic vascular resistance together with standard oscillometric measurement of blood pressure and heart rate. Ultrasonic cardiac output monitor parameters were also standardized by deriving body surface area referenced indices. Normal ranges were defined as lying within two standard deviations on either side of the mean. To assess interobserver variability, a second, blinded operator repeated 17% of scans.

MEASUREMENTS AND MAIN RESULTS

A total of 590 Chinese adolescents (49% boys) were scanned. Normal ranges for cardiac output, cardiac index, stroke volume, stroke volume index, stroke volume resistance, and systemic vascular resistance index are presented. Males had a significantly higher mean stroke volume, cardiac output, and systemic vascular resistance index compared with females (p < 0.05), but no significant differences were found for the indexed values. When compared with a group of 31 Australian Caucasian adolescents (71% boys), Chinese adolescents have a significantly lower cardiac output and stroke volume (p <0.05), but these differences disappeared when adjusted for body surface area (i.e., stroke volume index, cardiac index, and systemic vascular resistance index). Interobserver variability of ultrasonic cardiac output monitor-derived stroke volume showed a coefficient of variation of 10.2%, a correlation coefficient of 0.90 (95% confidence interval 0.85-0.93), while Bland-Altman analysis showed a mean bias of 1.5% (95% limits of agreement were -19.9% to 23.0%).

CONCLUSIONS

This study presents normal values for cardiovascular indices in Chinese adolescents using the ultrasonic cardiac output monitor. When referenced to body surface area, the differences between Caucasians and Chinese were insignificant.

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.

Children's Discomfort during Noninvasive Cardiac Output Monitoring by Suprasternal Ultrasonographic Transducer

Objectives

To investigate the level of discomfort/pain in children receiving Ultrasonic Cardiac Output Monitoring (USCOM), as compared to blood pressure measurement.

Methods

Healthy children, aged 3-12 years old, were recruited from kindergartens and schools as a part of the “Healthy children's vital signs and USCOM values” project. Oscillometric blood pressure was measured, followed by USCOM measurement. The discomfort experienced by the child during each intervention was assessed using the Wong-Baker FACES pain rating scale. The pain scores (scale from 0-5) were compared using Wilcoxon signed rank test. A difference in score of one point was considered to be clinically relevant. Gender differences in pain score were analysed using Mann-Whitney-U test.

Results

A total of 254 subjects (131 boys, 123 girls) were included. Mean age was 7.9 years with standard deviation (SD) of 2.4 years. The median pain score for USCOM measurement was 1.0 (95% CI=1.0 to 2.0) with interquartile range 1.0 to 2.0. The median pain score for BP measurement was 1.0 (95% CI,=1.0 to 1.0) with interquartile range 0.0 to 2.0. Overall, the pain score associated with USCOM was significantly higher than that associated with BP measurement. However, the difference fails to reach the minimum clinically significant difference of one-point. No significant difference was shown between boys and girls.

Conclusion

USCOM appears to be tolerated well by healthy children. The discomfort reported during USCOM measurement is comparable to that associated with blood pressure measurements.