Doppler Cardiac Output Measurement Research Articles

The Impact of Phenylephrine, Ephedrine, and Increased Preload on Third-Generation Vigileo-FloTrac and Esophageal Doppler Cardiac Output Measurements

Meng, Lingzhong; Tran, Nam Phuong; Alexander, Brenton S.; Laning, Kathleen; Chen, Guo; Kain, Zeev H.; Cannesson, MaximeAuthor Information

The Impact of Phenylephrine, Ephedrine, and Increased Preload on Third-Generation Vigileo-FloTrac and Esophageal Doppler Cardiac Output Measurements

Cardiac output (CO) monitoring based on pulse contour analysis (Vigileo-FloTrac) has the potential to be used for goal-directed fluid therapy in the perioperative setting. However, factors such as vasopressor usage may impact Vigileo-FloTrac's reliability in tracking CO changes. We tested third-generation Vigileo-FloTrac system's ability to accurately measure the changes in CO induced by vasopressor administration and increased preload in comparison with esophageal Doppler measurements. In 33 anesthetized patients, CO was monitored simultaneously by the third-generation Vigileo-FloTrac and esophageal Doppler. Hemodynamic challenges included phenylephrine (to increase vasomotor tone), ephedrine (to increase myocardial contractility and heart rate), and whole-body tilting (to increase preload). Measurements were performed before and after each intervention. Overall, 176 pairs of CO measurements were obtained. The difference between paired pulse contour and Doppler measurements of CO was 0.14 ± 2.13 L/min (mean ± SD), and the percentage error (2 SD of the difference divided by the mean CO of the reference method) was 66%. The trending ability of pulse contour versus Doppler was 23% (concordance, the percentage of the total number of data points that are in 1 of the 2 quadrants of agreement) after phenylephrine treatment, 69% (concordance) after ephedrine treatment, and 96% (concordance) after whole-body tilting. The pulse contour method of measuring CO, as implemented in the third-generation Vigileo-FloTrac device, accurately tracks changes in CO when preload changes. However, the pulse contour method does not accurately track changes in CO induced with phenylephrine and ephedrine.

Challenges in comparison of Doppler CO measurement methods and the importance of understanding ultrasound theory and practice

In your June 2010 edition Nguyen et al. compared transthoracic echocardiography (TTE), using pulsed wave (PW) Doppler ultrasound, with continuous wave (CW) Doppler using the ultrasonic cardiac output monitor (USCOM), and found significant disagreement. This is surprising. Both Doppler methods measure the same flow-generated Doppler frequency shift, so any controlled comparison should yield identical measures, and both methods have high levels of utility in over 40 years of clinical practice [1]. So how did this lack of agreement occur? TTE is ‘‘conventional echocardiography’’ and is a technically difficult method based on image-guided PW Doppler, (‘‘Duplex Doppler’’). It is expensive, requires 2–3 years of training and experience before qualification and professional registration, has a 45 min examination time and generally requires cardiologic supervision [2]. Further, PW is a user-dependent method with high inter and intra-operator variability requiring precise methodology and adherence to rigid examination protocols and guidelines to achieve clinical effectiveness [3]. It is precisely these clinical limitations that encouraged the development of the USCOM. USCOM is a 2D independent, CW Doppler device with an anthropometric algorithm, automated signal tracing and wide transmit beam which increases reliability, reproducibility and applicability of the Doppler method and adds the benefits of generalisability theory to increase sensitivity [5]. Additionally, operational proficiency can be achieved in a few days by both medical and non-medical personnel, has a 5–10 min examination time [4], and has been extensively validated. TTE and USCOM use different Doppler modalities and any valid comparison demands rigorous methodology and a carefully designed experimental protocol if the results are to reflect the modalities being compared rather than flaws in the study design. Nguyen et al. found disagreement between the methods and concluded equivocally on the clinical utility of USCOM. However, examination of Doppler theory and practice may allow for a more positive conclusion. As cardiac output (CO) = cross sectional area (CSA)9 heart rate (HR)9 velocity time integral (vti), the source of error in this study is easily identified from table 2 of the paper. The study found that comparison Phillips RA, Smith BE. Challenges in comparison of Doppler CO measurement methods and the importance of understanding ultrasound theory and practice. J Clin Monit Comput 2011

A novel operator-independent algorithm for cardiac output measurements based on three-dimensional transoesophageal colour Doppler echocardiography

Cardiac output (CO) measurements from three-dimensional (3D) trans-mitral Doppler echocardiography are prone to error as manual selection of the region of interest (i.e. the site of measurement) is required. We newly developed an automated, user-independent algorithm to select the site of colour Doppler CO measurement. We aimed to validate this new method by benchmarking it against thermodilution, the current gold standard for CO measurements. Transoesophageal colour 3D Doppler echocardiographic studies were obtained from 15 patients who also had received a pulmonary catheter for invasive CO measurements. Trans-mitral flow was determined using a novel operator-independent algorithm to automatically select the optimal site of measurement. The operator-independent CO measurements were referenced against thermodilution. A good correlation was found between operator-independent Doppler flow computations and thermodilution with a mean bias of 0.09 L/min, standard deviation of bias 1.3 L/min, and a 26% error (2 SD/mean CO). Mean CO was 4.94 L/min (range 3.10-7.10 L/min). Our findings demonstrate that CO computation from transoesophageal colour 3D Doppler echo can be automated concerning the site of velocity measurement. Our operator-independent algorithm provides an objective and reproducible alternative to thermodilution.

Epi-aortic Doppler measurement of cardiac output in univentricular connection

In the initial postoperative period after a Fontan-type operation for a univentricular circulation, cardiac output information is important, but cannot be provided by conventional methods due to the surgical reconstruction of the heart. In this regard we investigated the feasibility of epi-aortic Doppler measurements in order to calculate cardiac output. : Epi-aortic cardiac output measurement was compared with Fick measurements as the gold standard in eight patients with a univentricular circulation after a Fontan-type operation. The mean diameter of the aorta by epi-aortic measurement was 18 mm (range 14 to 25), by angiography 17 mm (range 10 to 24), correlation coefficient 0.88 (p < 0.05). The mean cardiac output by epi-aortic measurement was 2.8 l.min(-1) (range 1.2 to 6.3), by the Fick calculations 1.8 l.min(-1) (range 0.8 to 5.0). The correlation coefficient for cardiac output data in aortic diameters up to 20 millimeter in diameter was 0.55 (p < 0.05). Epi-aortic Doppler measurement of cardiac output after Fontan type reconstructions could be applied in aortas up to 20 millimeter in diameter. A reasonable correlation with Fick calculations was found. This was supported by Bland-Altman plotting. The method is intrinsically invasive, but application and removal of the device were easy and no complications related to the system were observed. An important restriction is the often present abnormal anatomy, either congenitally or after surgery.

Non-invasive ultrasonic cardiac output monitoring in exercise testing

Background The purpose of this study was to evaluate the relationship of breath-by-breath oxygen uptake (VO 2) and CO, cardiac index (CI), stroke volume (SV) and heart rate (HR) determined by a non-invasive continuous wave (CW) Doppler-based system (USCOM) in healthy adolescent and adult athletes during exercise treadmill testing. Methods Twenty athletes were enrolled for a standardized ramp treadmill test including transthoracic echocardiography at rest, incremental breath-by-breath spiroergometry, lactate kinetics and CW Doppler. Results VO 2 max was 51 ± 11 ml/min/kg in the adolescent cross country skiers (CI 8.2 ± 1.2 l/min/m 2) and 50 ± 12 ml/min/kg in adult soccer referees (CI 7.1 ± 1.2 l/min/m 2). CW Doppler hemodynamic variables showed significant correlation with VO 2 ( p < 0.01, n = 95) across the total of measures, with excellent correlation demonstrated for CO and CI (0.904 and 0.897), while HR and SV showed good to very good correlation with r values of 0.842 and 0.766, respectively. Correlation of the variables at peak exercise and 1 and 3 min after recovery, demonstrate that CO and SV show superior correlation with peak oxygen consumption (VO 2 max). The regression equation for VO 2 and CO USCOM was VO 2 = 4.43CO USCOM–10.3. Conclusion CW Doppler measurement of cardiac output is feasible as a measure of cardiac performance during standardized treadmill testing in adolescent and adult athletes.

The use of oesophageal Doppler cardiac output measurement to optimize fluid management during colorectal surgery

The use of oesophageal Doppler cardiac output measurement to optimize fluid management during colorectal surgery

Accuracy and repeatability of pediatric cardiac output measurement using Doppler: 20-year review of the literature.

Review of the accuracy and repeatability of Doppler cardiac output (CO) measurements in children. Publications in the scientific literature retrieved using a computerized Medline search from 1982-2002 and a manual review of article bibliographies. Studies comparing Doppler flow measurements with thermodilution, Fick, or dye dilution methods in the pediatric critical care setting were identified to assess the bias, precision, and intra- and interobserver repeatability of Doppler CO measurement. Where results were not suitable for comparison and the original measurements available, data were re-analyzed using appropriate statistical methods and presented in comparative tables. The precision of pediatric Doppler CO measurements compared to thermodilution, dye dilution, or Fick methods is around 30% and repeatability varies from less than 1% to 22%. Bias is generally less than 10% but varies considerably. The bias, precision, and repeatability from study to study indicate that Doppler CO measurements are acceptably reproducible in children, with best results when used to track changes rather than absolute values, and using the transesophageal approach.

Physicians’ Estimates of Cardiac Index and Intravascular Volume Based on Clinical Assessment Versus Transesophageal Doppler Measurements Obtained by Critical Care Nurses

To compare physicians' estimates of cardiac index and intravascular volume with transesophageal Doppler measurements obtained by critical care nurses, to assess the overall safety of transesophageal Doppler imaging by critical care nurses, and to compare hemodynamic measurements obtained via transesophageal Doppler imaging with those obtained via pulmonary artery catheterization. Data were collected prospectively on 106 patients receiving mechanical ventilation. Physicians estimated cardiac index and intravascular volume status by using bedside clinical assessment; critical care nurses, by using transesophageal Doppler imaging. In 24 patients, Doppler measurements were obtained within 6 hours of placement of a pulmonary artery catheter and recording of cardiac output and pulmonary artery occlusion pressure. With Doppler measurements as the reference, physicians correctly estimated cardiac index in 46 (43.8%) of 105 patients, underestimated it in 24 (22.9%), and overestimated it in 35 (33.3%). They correctly estimated volume status in 31 patients (29.5%), underestimated it in 16 (15.2%), and overestimated it in 58 (55.2%). Doppler measurements of cardiac output correlated with those obtained via pulmonary artery catheterization (r = 0.778; P < .001). Two patients had minor complications: dislodgement of a nasogastric tube and inability to obtain a Doppler signal. Physicians' assessment of cardiac index and intravascular volume in patients receiving mechanical ventilation is correct less than half of the time. Transesophageal Doppler imaging by critical care nurses appears to be a safe method for measuring cardiac index and estimating intravascular volume. Measurements obtained via Doppler imaging correlate well with those obtained via pulmonary artery catheterization.

Pulmonary Hypertension in Pregnancy

Abstract Objective: To describe the clinical course of pregnancies complicated by pulmonary hypertension and treated with the pulmonary vasodilators nifedipine and prostacyclin. Methods: Four pregnant women with pulmonary hypertension were treated with pulmonary vasodilators. Therapy with oral nifedipine and intravenous prostacyclin was guided by right pulmonary artery catheterization and Doppler measurements of cardiac output. Results: Three of four women responded to vasodilator therapy and successfully completed their pregnancies. Two who conceived at least 1 year after successful treatment and normalized right ventricle function carried three uncomplicated pregnancies. The woman who did not respond died. Delay in diagnosis contributed to her outcome. Noninvasive measurement of cardiac output helped diagnosis of right ventricular failure and offered reassurance in women who remained compensated. Postpartum decompensation in one woman was characterized by a negative Starling response as central venous pressure increased from 4 to 11 mmHg. She responded positively to diuresis. Conclusion: Early diagnosis of pulmonary hypertension is critical. Volume overload postpartum might significantly contribute to decompensation. We recommend a year of successful therapy after a response to vasodilator therapy and near-normal right ventricular function before pregnancy is considered. In complicated pregnancies, women must balance the best estimate of risk with the value they put on pregnancy.

Extravascular doppler measurement of cardiac output in infants and children after operations for congenital heart disease

J Thorac Cardiovasc Surg 1999;117:1223-5

Pulmonary Hypertension in Pregnancy

In Brief Objective To describe the clinical course of pregnancies complicated by pulmonary hypertension and treated with the pulmonary vasodilators nifedipine and prostacyclin. Methods Four pregnant women with pulmonary hypertension were treated with pulmonary vasodilators. Therapy with oral nifedipine and intravenous prostacyclin was guided by right pulmonary artery catheterization and Doppler measurements of cardiac output. Results Three of four women responded to vasodilator therapy and successfully completed their pregnancies. Two who conceived at least 1 year after successful treatment and normalized right ventricle function carried three uncomplicated pregnancies. The woman who did not respond died. Delay in diagnosis contributed to her outcome. Noninvasive measurement of cardiac output helped diagnosis of right ventricular failure and offered reassurance in women who remained compensated. Postpartum decompensation in one woman was characterized by a negative Starling response as central venous pressure increased from 4 to 11 mmHg. She responded positively to diuresis. Conclusion Early diagnosis of pulmonary hypertension is critical. Volume overload postpartum might significantly contribute to decompensation. We recommend a year of successful therapy after a response to vasodilator therapy and near-normal right ventricular function before pregnancy is considered. In complicated pregnancies, women must balance the best estimate of risk with the value they put on pregnancy. Pulmonary vasodilator therapy can benefit women with pulmonary hypertension in pregnancy, and favorable response before conception can predict successful pregnancy.

Pulmonary hypertension in pregnancy: treatment with pulmonary vasodilators

Objective: To describe the clinical course of pregnancies complicated by pulmonary hypertension and treated with the pulmonary vasodilators nifedipine and prostacyclin. Methods: Four pregnant women with pulmonary hypertension were treated with pulmonary vasodilators. Therapy with oral nifedipine and intravenous prostacyclin was guided by right pulmonary artery catheterization and Doppler measurements of cardiac output. Results: Three of four women responded to vasodilator therapy and successfully completed their pregnancies. Two who conceived at least 1 year after successful treatment and normalized right ventricle function carried three uncomplicated pregnancies. The woman who did not respond died. Delay in diagnosis contributed to her outcome. Noninvasive measurement of cardiac output helped diagnosis of right ventricular failure and offered reassurance in women who remained compensated. Postpartum decompensation in one woman was characterized by a negative Starling response as central venous pressure increased from 4 to 11 mmHg. She responded positively to diuresis. Conclusion: Early diagnosis of pulmonary hypertension is critical. Volume overload postpartum might significantly contribute to decompensation. We recommend a year of successful therapy after a response to vasodilator therapy and near-normal right ventricular function before pregnancy is considered. In complicated pregnancies, women must balance the best estimate of risk with the value they put on pregnancy.

Measurement of cardiac output in standing horses by Doppler echocardiography and thermodilution.

Measurement of cardiac output by Doppler echocardiography were compared to simultaneous measurements by thermodilution in 9 conscious horses. In the Doppler technique, mean blood flow velocities for estimation of cardiac output were recorded from the aorta and pulmonary artery. The flow area of each vessel was calculated from the vessel diameter, measured from a 2-dimensional ultrasound image. Differences in the site and method of measuring the vessel diameter altered the estimation of cardiac output by the Doppler method. Cardiac output was modified by the i.v. infusion of 4 micrograms/kg bwt/min dopamine and 4 micrograms/kg bwt/min dobutamine and by the i.v. administration of 10 micrograms/kg bwt detomidine and 20 micrograms/kg bwt butorphanol. Doppler measurements of cardiac output correlated closely with measurement by thermodilution. Measurements from the aortic outflow correlated more closely with thermodilution, than those from the pulmonary artery (r = 0.89 and r = 0.77, respectively). Doppler measurements when the mean flow velocity was recorded from the aorta and the flow area was measured from the ascending aorta using the leading edge method. There was no significant bias between the 2 techniques when Doppler flow velocities were recorded by this method and the limits of agreement were narrow (+/- 12.26 l/min). The differences between the 2 methods increased with increasing cardiac output. Doppler echocardiography is a safe noninvasive method of measuring cardiac output in horses. The agreement between Doppler echocardiography and thermodilution in this study is similar to that reported in man and is similar to that reported between thermodilution and other techniques in man.

Optimal number of beats for the Doppler measurement of cardiac output in atrial fibrillation

This study was undertaken to determine the optimum number of Doppler velocity waveforms required to calculate cardiac output in atrial fibrillation with the same degree of accuracy as that for sinus rhythm. Twenty-one patients in atrial fibrillation underwent calculations of cardiac output derived from aortic Doppler waveform velocity time integrals and RR intervals. The variability in estimates of the cardiac output was calculated with the successive addition of sequential beats and compared with that determined in a control group of 12 subjects in sinus rhythm. For the group in atrial fibrillation, a mean of 13 beats (range 4 to 17 beats) was required to achieve an estimation of cardiac output with a variability of less than 2%, compared with a mean of four beats in sinus rhythm. In atrial fibrillation, the mean number of beats required to determine cardiac output was approximately three times that necessary in sinus rhythm.

Doppler measurement of cardiac output during cardiopulmonary resuscitation.

To estimate the cardiac output produced by external cardiac compression during standard cardiopulmonary resuscitation performed by two groups of operators with different levels of experience and training. Cardiac output was measured by Doppler aortovelography. All patients included in the study had necropsy examinations. Only patients without evidence of pulmonary embolism, myocardial rupture, aortic valve disease, or acute depletion of the intravascular volume were included. 31 patients presenting to the accident and emergency department suffering from non-traumatic cardiac arrest had cardiac output measurements made during resuscitation. Eleven patients were excluded after necropsy examination. The median cardiac index for the 20 study patients was 3.2 L min-1 m-2. The cardiac output produced by massage by less experienced personnel (median 1.2 L min-1 m-2) was significantly less than that produced by those fully trained in the technique (median 3.2 L min-1 m-2; P < 0.01 95% confidence interval -2.36 to -1.29). The amount of resuscitation related trauma was no greater than in other published series. Differences in cardiac output during external cardiac compression are related to experience with the technique.

Pulsed Wave Doppler Measurement of Cardiac Output from the Right Ventricular Outflow Tract

Pulsed Wave Doppler Measurement of Cardiac Output from the Right Ventricular Outflow Tract

An investigation of the changes in aortic diameter and an evaluation of their effect on Doppler measurement of cardiac output in pregnancy

Measurement of cardiac output by means of Doppler ultrasound is based on the velocity of aortic blood flow and therefore requires that aortic diameter should not change between measurements. Work has been published which suggests that, in pregnancy, aortic diameter varies significantly with systemic blood pressure. The implication of this is that aortic diameter must be remeasured for each determination of cardiac output in pregnant patients. This study investigated the changes in aortic diameter with blood pressure in patients having spinal anaesthesia for caesarean section. Aortic diameter did appear to vary with blood pressure but this variation was within the error of the measurement and did not significantly affect the accuracy of the technique.

Simultaneous analysis of inulin and 15N2-urea kinetics in humans

To elucidate the physiologic basis of multicompartmental systems used to model drug distribution, we studied inulin and 15N2-urea kinetics after simultaneous intravenous injection in five normal subjects. Distribution of both compounds was characterized by three-compartment models in which the central compartment corresponded to intravascular space. The mean distribution volumes of 0.164 +/- 0.009 L/kg (+/- SD) for inulin and of 0.670 +/- 0.143 L/kg for urea were similar to expected values for extracellular space and total body water, respectively. Distribution from intravascular space was kinetically heterogeneous, presumably reflecting differences in vascular beds supplied by either fenestrated and discontinuous capillaries or capillaries with a continuous basement membrane. Intercompartmental clearances of inulin and urea and the ratio of their free water diffusion coefficients were used to estimate blood flows and permeability coefficient-surface area products for the peripheral compartments. The sum of compartmental blood flows averaged 5.39 +/- 0.49 L/min and was similar to dual-beam Doppler measurements of cardiac output (5.47 +/- 0.40 L/min).

Doppler echocardiographic measurement of cardiac output in man using mitral annulus method.

The mitral inflow method of measuring cardiac output with pulsed Doppler two-dimensional echocardiography was developed and validated against the thermodilution technique in 42 patients. A mitral inflow method combined the velocity of left ventricular inflow at the mitral annulus (apical long-axis view) with the cross-sectional area of the annulus calculated from its diameter (parasternal long-axis view). A good correlation was observed between thermodilution and Doppler measurements of cardiac output (r = 0.93). The ratio of Doppler measurements to thermodilution measurements will be between 0.76 and 1.15 for about 95% of cases. There was a good correlation between percentage change in thermal cardiac output and those in Doppler cardiac output (r = 0.95); the limits of agreement were -11.5% to 10.5%, suggesting that this method can be most useful for assessing relative changes in cardiac output.