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PubMed1991

Cardiac output by pulsed Doppler in neonates using the apical window.

In 18 healthy neonates, cardiac output was measured by range-gated Doppler echocardiography with simultaneous two-dimensional echocardiography, using the apical approach. Maximal and modal flow velocities were compared by using spectral analysis of the Doppler signal. Blood flow velocities were measured in the left ventricular outflow tract and in the ascending aorta. Cardiac index (cardiac output per kg body weight), with the sample volume placed in the left ventricular outflow, averaged 170 +/- 45 ml/min/kg in the maximal flow velocity mode and 133 +/- 39 ml/min/kg in the modal mode, respectively (p less than 0.05). Sampling in the ascending aorta gave cardiac index values of 198 +/- 73 ml/min/kg in the maximal velocity and 167 +/- 58 ml/min/kg in the modal velocity mode. Maximal flow velocities in the ascending aorta came closest to published data obtained by invasive and noninvasive methods.

Blood Flow Velocity↗
PubMed1986

Maintenance of cardiac output with normal filling pressures in patients with dilated heart failure.

Therapy of elevated ventricular filling pressures in patients with dilated heart failure may be limited by concern that cardiac output will be further compromised. Twenty-five patients with severe symptoms and ejection fractions of 25% or less were studied to determine the lowest ventricular filling pressures that could be achieved with vasodilator and diuretic therapy while maintaining cardiac output. In 20 of 25 patients normal pulmonary capillary wedge pressures (PCWs) were achieved (mean 10 mm Hg compared with 30 mm Hg at baseline). Stroke volume was 60 vs 39 ml at baseline. Stroke work index was 30 vs 19 g-m/m2. For each patient, over the range of PCWs, stroke volume and stroke work index were maintained and were often maximal at the lowest PCW achieved. The upright position was well tolerated in patients with normal supine PCW. Normal filling pressures can be achieved in patients with congestive heart failure without compromise of cardiac output. While congestive symptoms should be improved, the feasibility and benefit of maintaining normal filling pressures over a long term must be established.

Cardiac Catheterization↗
PubMed2002

Cardiac output, coronary blood flow, and blood gases during open-chest standard and compression-active-decompression cardiopulmonary resuscitation.

OBJECTIVE: To determine whether open-chest compression-active-decompression (CAD) could improve cardiac output, coronary blood flow, blood gases, and resuscitation compared to open-chest manual compression in a porcine model of cardiac arrest. DESIGN: Prospective, randomized laboratory investigation for measurement of cardiac output, coronary blood flow, arterial and mixed venous blood gases and potassium levels, and return of spontaneous circulation. SUBJECTS: Ten pigs each weighing approximately 36.4 kg. INTERVENTIONS: Following preparation of the model and opening of the chest, ultrasonic flow probes were placed on the ascending aorta and left anterior descending artery. Cardiac arrest was induced by epicardial pacing. Subjects received either open-chest CAD or open-chest manual compression. After 10 min of arrest, defibrillation was attempted. MEASUREMENTS AND MAIN RESULTS: Cardiac output fell to 46+/-53% (95% CI: -20 to 112) and 41+/-14% (95% CI: 23-59) (P>0.05) of baseline with CAD and manual methods at 5 min after arrest, respectively. Similarly, coronary blood flow fell to 33+/-14% (95% CI: 16-50) and 42+/-16% (95% CI: 22-62) (P>0.05) of baseline at 5 min. Both groups developed similar levels of metabolic acidosis, mixed venous hypoxemia, and hyperkalemia, with potassium levels: 6.5+/-4.0 meq/l (95% CI: 1.6-11.4) at 5 min and 7.5+/-4.6 meq/l (95% CI: 1.8-13.2) at 10 min in the CAD group and 5.8+/-2.0 meq/l (95% CI: 3.4-8.3) at 5 min and 6.1+/-1.4 meq/l (95% CI: 4.4-7.9) at 10 min in the manual group. Levels of hyperkalemia were inversely proportional to the square of PvO(2). One pig in each group was resuscitated after defibrillation. CONCLUSION: We found no benefit using CAD. Both low coronary blood flow and hyperkalemia may have limited resuscitation.

Animals↗
PubMed1984

Validation of noninvasive maximal cardiac output measurement.

Due to the invasiveness of direct techniques and problems that constrain the use of popular indirect techniques during very heavy (non-steady-state) exercise, measurements of maximal cardiac output are seldom included in studies of exercise. The acetylene-rebreathing technique is well-suited for maximal exercise; however, until recent technological advances, difficulties involved in collecting and measuring alveolar acetylene samples have restricted its use. We compared cardiac output values measured via the acetylene-rebreathing technique (QA) (modified for use with a mass spectrometer) and the dye-dilution technique (QD) at rest and during light to maximal exercise in six moderately active males. Although QA consistently underestimated QD, the two techniques showed a significant correlation of 0.87 throughout all levels of exercise. During maximal exercise, QA and QD values were not significantly different (24.7 and 26.7 l X min-1, respectively). Modifications in the QA technique that reduce potential sources of error were also examined. We conclude that the acetylene-rebreathing technique, modified for use with a mass spectrometer, is a simple and valid procedure for measuring maximal cardiac output.

Adult↗
PubMed1997

Stroke volume and cardiac output in normotensive children and adults. Assessment of relations with body size and impact of overweight.

BACKGROUND: Relations between organs and body size are not linear but rather follow allometric (growth) relations characterized by their powers (exponents). METHODS AND RESULTS: Stroke volume (SV) by M-mode echocardiography was related to height, weight, body surface area (BSA), and ideal BSA (derived from ideal body weight for given height) in 970 normotensive individuals (1 day to 85 years old; 426 < 18 years old; 204 overweight to obese; 426 female). In normal-weight children, adults, and the entire population, SV was related by allometric relations to BSA (power = 0.82 to 1.19), body weight (power = 0.57 to 0.71), and height (power = 1.45 to 2.04) (all P < .0001). Relations of cardiac output to measures of body size had lower allometric powers than those for SV in the entire population (0.41 for body weight, 0.62 for BSA, and 1.16 for height). In overweight adults, observed SVs were 17% greater than predicted for ideal BSA, a difference that was approximated by normalization of SV for height to age-specific allometric powers. Similarly, observed cardiac output was 19% greater than predicted for ideal BSA, a difference that was accurately detected by use of cardiac output/height to age-specific allometric powers but not of BSA to the first power. CONCLUSIONS: Indices of SV and cardiac output for BSA are pertinent when the effect of obesity needs to be removed, because these indices obscure the impact of obesity. To detect the effect of obesity on LV pump function, normalization of SV and cardiac output for ideal BSA or for height to its age-specific allometric power should be practiced.

Adolescent↗
PubMed1985

Systemic cardiac output and distribution during high-frequency oscillation.

High-frequency oscillation (HFO) appears to be an alternate, less traumatic mode of ventilating surfactant-deficient patients, because conventional (mechanical) pressure-limited ventilation (CMV) compromises cardiac function at high mean airway pressures. We compared systemic cardiac output and its distribution during HFO and CMV in ten adult rabbits rendered surfactant deficient by repeated pulmonary saline lavage. Cardiac output and organ blood flow were measured using the radionucleotide-labeled microsphere technique during ventilation at a mean airway pressure of 15 cm H2O and an inspired oxygen concentration of 100%. Both cardiac output and organ perfusion were similar during both modes of ventilation.

Animals↗
PubMed1977

Hemodynamic responses to dopamine infusion at controlled normal and low cardiac output states in the anesthetized dog.

In order to isolate the renal and pulmonary vascular effects of dopamine, we employed a dog preparation utilizing fixed venous return in order to control cardiac output at either a normal or low flow state. Dopamine infusion was carried out at doses of 8 and 16 microng/Kg./min. Heart rate, mean systemic arterial pressure, mean pulmonary artery pressure, and renal blood flow were measured. Changes in mean systemic arterial pressure, mean pulmonary artery pressure, and renal blood flow were not significant at either doses of dopamine. There was a dose-related increase in heart rate, most significant with a dose of 16 microng/Kg./min. and low cardiac output. No evidence was found to substantiate the existence of a specific dopaminergic receptor in the renal vasculature when cardiac output was controlled.

Animals↗
PubMed2002

Equipment review: new techniques for cardiac output measurement--oesophageal Doppler, Fick principle using carbon dioxide, and pulse contour analysis.

Measuring cardiac output is of paramount importance in the management of critically ill patients in the intensive care unit and of 'high risk' surgical patients in the operating room. Alternatives to thermodilution are now available and are gaining acceptance among practitioners who have been trained almost exclusively in the use of the pulmonary artery catheter. The present review focuses on the principles, advantages and limitations of oesophageal Doppler, Fick principle applied to carbon dioxide, and pulse contour analysis. No single method stands out or renders the others obsolete. By making cardiac output easily measurable, however, these techniques should all contribute to improvement in haemodynamic management.

Blood Pressure↗
PubMed2004

A novel approach to measure cardiac output noninvasively: a comparison with the thermodilution method on critical care patients.

OBJECTIVE: To compare the accuracy and reliability of cardiac output (CO) measurement by a Noninvasive Hemodynamic Analyzer (NHA) to the thermodilution cardiac output (COTD) technique in ICU patients of cardiac condition. METHOD: ICU retrospective data collected in a 700-bed university-affiliated regional medical center. The data results from 203 patients who required invasive hemodynamic monitoring for clinical and/or surgical management. RESULTS: The ranges of the two CO measurements were: CO(TD) = 2.06 to 8.8 l/min and CO(NHA) = 2.06 to 8.46 l/min, respectively. The Mean and SD of CO(NHA) = 4.819 l/min +/- 1.053 was near to CO(TD) = 4.902 l/min +/- 1.421. Variance was better for CO(NHA) = 1.110 l/min compared to CO(TD) = 1.421 l/min. Median of CO(NHA) showed 4.813 l/min and CO(TD) = 4.660 l/min. Bias was 0.083 l/min with 95% Confidence Interval (Precision): -0.26 to 0.040, and 95% Limits of Agreement was between -1.661 to 1.827 l/min. CONCLUSIONS: The results of this retrospective study indicate that the CO(NHA) technique may be a promising screening method. Additional studies are needed to explore its diagnostic trending capability. This noninvasive CO technique has been proven to be clinically accurate and may be applicable for telemedicine applications.

Algorithms↗
PubMed2004

Effects of vasopressin on left anterior descending coronary artery blood flow during extremely low cardiac output.

UNLABELLED: Because of the possibility of vasopressin-mediated coronary vasospasm, this study was designed to assess effects of vasopressin compared to saline placebo on left anterior descending (LAD) coronary artery blood flow. Twelve anaesthetized domestic swine were prepared for LAD coronary artery blood flow measurement with ultrasonic flow probes, using cardiopulmonary by-pass adjusted to 10% of the prearrest cardiac output. This 10% value approximates that reported for cardiac output during conventional closed-chest CPR. After 4 min of untreated ventricular fibrillation, and 3 min of cardiopulmonary by-pass blood flow, 12 pigs were randomly assigned to receive intravenously, every 5 min, either vasopressin (0.4, 0.4, and 0.8 U/kg; n = 6) or saline placebo (n = 6). The mean +/- S.D. LAD coronary artery blood flow in the vasopressin and placebo pigs was comparable before cardiac arrest, and during cardiopulmonary by-pass low flow; but increased significantly (P < 0.05) 90 s after each of three vasopressin injections compared to placebo (78 +/- 1 versus 42 +/- 2 ml/min; 62 +/- 2 versus 36 +/- 1 ml/min; and 54 +/- 1 versus 27 +/- 1 ml/min), respectively. Coronary vascular resistance decreased significantly (P < 0.05 ) 90 s after each of three vasopressin and placebo injections. In this model, repeated bolus administration of vasopressin, given during simulated extremely low cardiac output improved LAD coronary artery blood flow to prearrest levels without affecting coronary vascular resistance. CONCLUSIONS: during extremely low blood flow using cardiopulmonary by-pass, vasopressin improves LAD coronary artery blood flow without affecting coronary vascular resistance.

Animals↗
PubMed1989

Decreased O2 consumption and cardiac output during normobaric hyperoxia in conscious dogs.

Recent reports indicate that under certain restricted conditions hyperoxia may decrease tissue O2 consumption. However, this effect has not been established for whole body O2 consumption in the intact healthy conscious state. The goal of the present study was to document the effect of hyperoxia on resting whole body O2 consumption and hemodynamics under these latter more general physiological conditions. The inspired gas was delivered by mask to six fasted resting conscious dogs and alternated hourly between air and O2-enriched air (hyperoxia) for 5 h, while hemodynamics and blood gas data were obtained every 20 min. Compared with air breathing, hyperoxia increased the mean arterial O2 tension from 95 to 475 Torr and decreased heart rate, cardiac output, pulmonary vascular resistance, and right and left ventricular work rates and thus, presumably, myocardial O2 consumption. Hyperoxia also increased systemic vascular resistance and right atrial pressure but did not change stroke volume or systemic arterial pressure. The increase in arterial O2 content during hyperoxia was counterbalanced by the decrease in cardiac output, so that O2 delivery was unchanged by hyperoxia. Surprisingly, hyperoxia decreased the arterial-to-mixed venous difference in O2 content; this decrease together with the decrease in cardiac output produced a decrease in resting whole body O2 consumption from 5.88 +/- 0.68 to 4.80 +/- 0.62 ml O2.min-1.kg-1 (P = 0.0002). It is concluded that under physiological conditions normobaric hyperoxia may decrease metabolic rate in addition to cardiac output, which may have important implications for the metabolic regulation of O2 utilization as well as for the medical and nonmedical uses of O2.

Animals↗
PubMed1990

First passage radionuclide cardiography for determination of cardiac output: a critical analysis.

First-pass radiocardiography, by single probe or gamma camera, has the theoretic potential to be an attractive non-invasive indicator dilution method of measuring cardiac output. Registrations, once programmed, require little time to perform and entail hardly any risk for the subject. At the same time, they are to varying degrees inaccurate. As long as technology is not standardized, each institution that wishes to employ these measurements has to do its own critical validation before results can be accepted. As with any other indicator dilution technique, precision of radiocardiography is served by repetitive measurements. However, radiation dose and disturbing background radioactivity preclude taking multiple measurements within a short period. This holds particularly for the gamma camera. The speed and simplicity of the probe system make this device very suitable for serial evaluation of cardiac function at the bedside. Depending on collimation of the probe and extracardiac background activity, a correction factor has to be derived empirically to avoid overestimation of cardiac output. The major advantage of the gamma camera linked to a data system is that an infinite number of first-pass curves can be obtained from different parts of the heart. Provided that appropriate regions of interest are selected, first-pass studies can yield reasonably accurate and reproducible determinations of cardiac output. In addition, functional image analysis during the equilibrium phase enables calculation of other cardiac variables such as ejection fraction and chamber size. Nevertheless, standardization of 'hardware' and 'software' is imperative.

Cardiac Output↗