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At least 577 records · Page 32Linked to original sources
PubMed1988

Use of transthoracic bioimpedance to determine cardiac output in pediatric patients.

The use of a transthoracic bioimpedance monitor to determine cardiac output was evaluated in critically ill children. The children ranged in age from 10 months to 8 yr and their height and weight ranged from the third to the 97th percentile. Each child had a thermodilution catheter in place to monitor cardiac output. The bioimpedance monitor used in this study, the NCCOM-3, required the input of a constant (L), which was obtained for each individual patient by adjusting the L setting until cardiac output measured by bioimpedance (COBI) was within 10% of cardiac output measured by thermodilution (COTD). This method of determining L was superior to using either measured thoracic length or the manufacturer's guidelines to obtain L and resulted in an excellent correlation between COTD and COBI (r = .94; p less than .05; n = 59). In children less than 125 cm in height, measured thoracic length alone was inadequate to use for L but provided a good approximation of L when multiplied by 1.25. This study suggests that the use of transthoracic bioimpedance to determine cardiac output compares favorably with thermodilution techniques and it is noninvasive.

Cardiac Output↗
PubMed2002

Effect of ventilatory settings on accuracy of cardiac output measurement using partial CO(2) rebreathing.

BACKGROUND: Recently, a new device has been developed to measure cardiac output noninvasively using partial carbon dioxide (CO(2)) rebreathing. Because this technique uses CO(2) rebreathing, the authors suspected that ventilatory settings, such as tidal volume and ventilatory mode, would affect its accuracy: they conducted this study to investigate which parameters affect the accuracy of the measurement. METHODS: The authors enrolled 25 pharmacologically paralyzed adult post-cardiac surgery patients. They applied six ventilatory settings in random order: (1) volume-controlled ventilation with inspired tidal volume (V(T)) of 12 ml/kg; (2) volume-controlled ventilation with V(T) of 6 ml/kg; (3) pressure-controlled ventilation with V(T) of 12 ml/kg; (4) pressure-controlled ventilation with V(T) of 6 ml/kg; (5) inspired oxygen fraction of 1.0; and (6) high positive end-expiratory pressure. Then, they changed the maximum or minimum length of rebreathing loop with V(T) set at 12 ml/kg. After establishing steady-state conditions (15 min), they measured cardiac output using CO(2) rebreathing and thermodilution via a pulmonary artery catheter. Finally, they repeated the measurements during pressure support ventilation, when the patients had restored spontaneous breathing. The correlation between two methods was evaluated with linear regression and Bland-Altman analysis. RESULTS: When VT was set at 12 ml/kg, cardiac output with the CO(2) rebreathing technique correlated moderately with that measured by thermodilution (y = 1.02x, R = 0.63; bias, 0.28 l/min; limits of agreement, -1.78 to +2.34 l/min), regardless of ventilatory mode, oxygen concentration, or positive end-expiratory pressure. However, at a lower VT of 6 ml/kg, the CO(2) rebreathing technique underestimated cardiac out-put compared with thermodilution (y = 0.70x; R = 0.70; bias, -1.66 l/min; limits of agreement, -3.90 to +0.58 l/min). When the loop was fully retracted, the CO(2) rebreathing technique overestimated cardiac output. CONCLUSIONS: Although cardiac output was underreported at small VT values, cardiac output measured by the CO(2) rebreathing technique correlates fairly with that measured by the thermodilution method.

Aged↗
PubMedDate not supplied

Measuring cardiac output in critically Ill patients: disagreement between thermodilution-, calculated-, expired gas-, and oxygen consumption-based methods.

Calculated values of oxygen consumption have been used to calculate a Fick cardiac output when thermodilution measurements are unreliable and when oxygen consumption measurements are unavailable. To determine the accuracy of these calculations, we measured cardiac output in 20 patients by four methods: (1) a reference Fick cardiac output calculated from metabolic oxygen consumption measurements and arterial-venous oxygen content difference (COmet); (2) thermodilution cardiac output (COtherm), (3) an estimated Fick cardiac output based on calculated oxygen consumption using standard equations (COcalc), and (4) an estimated Fick cardiac output using a bedside measurement of expired carbon dioxide production (COexp). The mean difference +/- 95% limits of agreement between COtherm and COmet was 1.71 +/- 5 liters/min. The mean difference between COcalc and COmet was -0.04 +/- 3.33 liters/min. The mean difference between COexp and COmet was 0.31 +/- 3.01 liters/min. On the basis of these wide confidence intervals, we conclude that (1) thermodilution and metabolic measurements of cardiac output frequently differ in critically ill patients, and (2) estimates of oxygen consumption, based on either standard equations or on expired carbon dioxide production measurements, are poor substitutes for metabolic measurements of oxygen consumption in critically ill subjects and may provide inaccurate estimates of cardiac output.

Adult↗
PubMed1992

Arterial vasodilation is not the cause of increased cardiac output in cirrhosis.

A pathological state of arterial vasodilation has been postulated to cause the increased cardiac output commonly observed in cirrhosis. Further, subsequent arterial underfilling has been proposed as the stimulus to sodium retention and ascites formation. Left ventricular size during the cycle of a cardiac contraction is predictably altered by a decrease in afterload. Specifically, increased systolic emptying should be observed. The relationship of left ventricular size during the cardiac cycle to systemic hemodynamic indices and urinary sodium retention was investigated in patients with alcoholic cirrhosis to test these hypotheses. Echocardiographic studies were performed on 24 male patients with alcoholic cirrhosis and compared with the results obtained in 10 age-matched male controls. Patients with cirrhosis had increased cardiac output and heart rate and decreased arterial pressure compared with normal subjects, confirming the presence of a hyperdynamic circulation. Patients with cirrhosis had enlarged left ventricular diameter at both end diastole (0.08 +/- 0.01 vs. 0.07 +/- 0.007 cm/kg dry body wt; P less than 0.001) and end systole (0.06 +/- 0.01 vs. 0.05 +/- 0.005 cm/kg; P less than 0.05). Left ventricular end-diastolic diameter was directly related to blood volume (r = 0.56, P less than 0.005). No significant differences in cardiac output, arterial pressure, or systemic resistance were found between patients with and patients without ascites. Increased cardiac output in cirrhosis occurs in conjunction with an enlarged ventricle throughout the cardiac cycle. The increase in left ventricular end-systolic diameter indicates that diminished afterload is not responsible for the increase in cardiac output. As the diameter of the ventricle during diastolic filling correlates with vascular volume, cardiac output in cirrhosis may be primarily determined by an increase in vascular volume.

Adult↗
PubMed1997

Impedance cardiography in cardiac surgery patients: abnormal body weight gives unreliable cardiac output measurements.

BACKGROUND: To study the accuracy of cardiac output measurement by means of Electrical Impedance Cardiography (EIC) in post-cardiac surgery patients. METHODS: In a prospective study, we compared cardiac output measurements by means of thermodilution (COTD) with impedance cardiographic-derived values (COEIC) in 37 mechanically ventilated patients after cardiac surgery. Both methods were used simultaneously. RESULTS: COEIC values were weakly correlated with COTD in the total group when the equation of Sramek-Bernstein was employed to calculate COEIC (r = 0.60, P < 0.001, mean difference and standard deviation: -0.06 +/- 1.25 l.min-1). After exclusion of the 12 patients whose body weight differed > 15% from their ideal body weight, no significant difference was found between the mean values (5.40 +/- 1.80 l.min-1 (COEIC) vs 5.31 +/- 1.69 l.min-1, n = 25) while the correlation coefficient increased substantially (r = 0.85, P < 0.001, mean difference and standard deviation: 0.09 +/- 0.96 l.min-1). CONCLUSIONS: The results of this study indicate that weight is a very important factor in unreliable measurement of CO by impedance cardiography in cardiac surgery patients. The calculation equation as proposed by Sramek and Bernstein is not accurate enough in patients with more than 15% of weight deviation. Therefore, the use of impedance cardiography in these patients is of limited value until an accurate correction factor has been developed.

Adult↗
PubMed1998

[Automated cardiac output measurement by color Doppler echocardiography].

Recently, automated cardiac flow measurement (ACM) has been developed for measuring the volume flow rate of blood flow through the left ventricular outflow tract. Measurements of left ventricular cardiac output by the ACM method were compared with those by the thermal dilution method with a Swan-Ganz catheter in 27 patients (16 men and 11 women; aged 44 +/- 3 years) in whom clear two-dimensional and color Doppler images of the left ventricular outflow tract were obtained. The total time required for left ventricular stroke volume calculation by both ACM and pulsed Doppler methods was measured in 10 patients (six men and four women; aged 41 +/- 2 years). There was an excellent correlation in the measurements of cardiac output between the ACM and thermal dilution methods (y = 0.77x + 0.77, r = 0.84, SEE = 0.4 l/min). The total time required for left ventricular stroke volume calculation by the ACM method was significantly shorter than that by the pulsed Doppler method (92 +/- 10 vs 177 +/- 30 sec, p < 0.01). The ACM method is simple, quick, and accurate for the automated assessment of cardiac output.

Adult↗
PubMed1988

Automated non-invasive measurement of cardiac output: comparison of electrical bioimpedance and carbon dioxide rebreathing techniques.

Two commercial automated, non-invasive systems for estimation of cardiac output were evaluated. Values of cardiac output obtained by electrical bioimpedance cardiography (BoMed NCCOM3 machine) were compared with values derived from an indirect Fick technique that uses carbon dioxide rebreathing (Gould 9000 IV system) during 103 simultaneous measurements made at rest in 19 randomly selected subjects and on exercise in 11 subjects. Cardiac output values obtained with impedance cardiography were significantly correlated with those measured by the indirect Fick method, although there was a wide scatter with over 73% of the readings lying outside the limits defined by the line of identity +/- 20%. This correlation was greatly reduced when stroke volume index was used instead of cardiac output. Indirect Fick results were linearly related to oxygen uptake both at rest and on exercise, while impedance cardiography results did not correlate with oxygen uptake. Impedance cardiography gave consistently lower results for cardiac output than indirect Fick at all levels of exercise. Both machines were easy to use and produced acceptable mean (SE) coefficients of variation (BoMed NCCOM3 7.7 (1.0)%, Gould 9000 IV 10.6 (1.4)%). Further validation is required before either of these machines can be recommended as an alternative to invasive monitoring in clinical practice.

Adolescent↗
PubMed2001

Descending aortic blood flow and cardiac output: a clinical and experimental study of continuous oesophageal echo-Doppler flowmetry.

BACKGROUND: Several studies have demonstrated that perioperative optimisation of oxygen delivery and haemodynamics can reduce mortality and morbidity for high-risk surgical patients. To optimise cardiac output, reliable, continuous and "less invasive" methods for measuring cardiac output are urgently needed. METHODS: Eight landrace pigs were studied during experimental repeated cardiac tamponade and 14 patients during liver transplantation. Aortic blood flow was measured by using transoesophageal echo-Doppler technique. A total of 91 paired measurements of aortic blood flow and cardiac output with different techniques were performed in the pigs and 124 paired measurements in the patients. RESULTS: Transoesophageal echo-Doppler did provide continuous real-time monitoring of the rapid and dramatic haemodynamic changes occurring during cardiac tamponade and during liver transplantation, while only intermittent information was obtained from the bolus thermodilution technique. Changes in haemodynamics were more difficult to detect with the "continual" cardiac output thermodilution technique. Changes in aortic blood flow closely followed changes in cardiac output determined by the bolus thermodilution technique both in pigs (r= 0.89) and in patients (r=0.80). In patients, aortic blood flow constituted about 70% of cardiac output determined by the bolus thermodilution technique. CONCLUSIONS: A combined echo-Doppler technique can be valuable for continuous monitoring of haemodynamic changes in the perioperative setting, and changes in aortic blood flow agree well with corresponding changes in cardiac output intermittently obtained by thermodilution cardiac output measurements. With the combined echo-Doppler technique a proper position of the Doppler beam is greatly facilitated by the M-mode echo visualisation of the aortic wall and aortic cross-sectional area is continuously measured.

Adult↗
PubMed1987

Effects of tricuspid regurgitation on thermodilution cardiac output: studies in an animal model.

The thermal dilution technique (TD) of measuring cardiac output (Q) has been assumed to be inaccurate when the tricuspid valve is regurgitant (TR). The indicator transit time from the right atrium to pulmonary artery (PA) is prolonged and may increase indicator loss to the heart and adjacent tissue. We surgically created TR in four anaesthetized dogs and compared simultaneous cardiac output measurement made with an implanted PA flow probe with intermittent TD cardiac output measurements. We found an excellent correlation (r = 0.98) between the techniques in the normal heart when Q was increased by 100-150 per cent of control values using an intravenous dobutamine infusion. After TR was produced by incorporating the tricuspid valve leaflet within a suture, Q decreased. Dextran 40 was then infused and Q increased significantly. The rate at which Q increased was greater with the TD technique than with the PA flow probe; however, a significant (r = 0.85) linear relationship was still present with TR. The altered thermal waveform detected by the PA thermistor in TR was characterized by a lower peak amplitude and a slower return to baseline. Within the limitations of an animal model, our data suggest that TD cardiac output may be more accurate than previously assumed, particularly in low output states.

Animals↗
PubMed2001

Effect of a catecholamine-induced increase in cardiac output on extravascular lung water.

OBJECTIVE: To determine the influence of dopamine- and dobutamine-induced increases in cardiac output on the extravascular lung water in an experimental model of pulmonary edema. DESIGN: Animal experimental study. SETTING: Animal experimental laboratory of a tertiary hospital. SUBJECTS: Mixed-race pigs (n = 20) weighing 28-32 kg. INTERVENTIONS: After the animals were anesthetized and tracheotomized, they were injected with 0.1 mL/kg of oleic acid, producing a pulmonary edema by increased permeability. The animals then were randomized into two groups: Group I (n = 10) received no medication to alter cardiac output and remained on mechanical ventilation during the 240 mins of the experiment; group II (n = 10) received a continuous infusion of dopamine and dobutamine to produce a cardiac output increase of >or=30% the basal value and underwent the same mechanical ventilation regimen as group I. MEASUREMENTS AND MAIN RESULTS: Hemodynamic and respiratory variables were measured at 0 (baseline) and 30, 60, 120, 180, and 240 mins after the infusion of oleic acid. At 30 mins, the cardiac output of group II (5.40 +/- 0.94 L/min) was significantly (p < .005) higher than that of group I (3.65 +/- 1.02 L/min), and a similar significant increase was recorded at all measurement times until the end of the experiment. The mean pulmonary arterial pressure was similar in both groups except that at 240 mins it was significantly higher in group I (normal cardiac output) than in group II (high cardiac output; 34.9 +/- 7.9 mm Hg vs. 27.2 +/- 3.8 mm Hg, p = .01). The extravascular lung water was calculated by gravimetric method after the death of the animal. The extravascular lung water of group I (13.8 +/- 3.6 mL/kg) did not significantly differ from that of group II (11.5 +/- 4.0 mL/kg). CONCLUSIONS: An increase in cardiac output experimentally produced by the infusion of dopamine and dobutamine does not modify the amount of extravascular lung water.

Animals↗
PubMed1996

[Left cardiac output curve and pulmonary venous return curve in patients with various heart diseases].

This study assessed the cardiac function of humans by drawing simultaneous left cardiac output and pulmonary venous return curves using radionuclide angiocardiography and right heart catheterization which allows recording of the pressure-flow relationship. Thirty-one subjects with various cardiac diseases were divided into two groups [18 patients with New York Heart Association (NYHA) functional class I and 13 patients with NYHA classes II or III]. Mean pulmonary filling pressure (Pmp) was calculated from the formula of Guyton, using pulmonary arterial compliance which was measured by Reuben's method and pulmonary venous compliance measured as reported previously. On the pressure-flow plane, the down slope of the pulmonary venous return curve was drawn by joining the points of (Pmp, 0) and (mean pulmonary capillary wedge pressure, cardiac output). To construct the cardiac output curve, two levels of lower body negative pressure were used to regulate the venous return to the heart. Pmp and the resistance to pulmonary venous return in NYHA II or III patients were significantly higher than those in NYHA I patients (Pmp: 16.3 +/- 1.5 vs 9.0 +/- 0.5 mmHg, p < 0.01; resistance to pulmonary venous return: 0.75 +/- 0.09 vs 0.43 +/- 0.04 mmHg/l/min, p < 0.01, respectively). The slope of pulmonary venous return curve in NYHA II or III patients was smaller than that in NYHA I patients and the pulmonary venous return curve in NYHA II or III patients shifted rightward. The slope of cardiac output curve in NYHA II or III patients was significantly smaller than that in NYHA I patients. This curve in NYHA II or III patients shifted downward and rightward. These results indicate that simultaneous cardiac output and pulmonary venous return curves may be a useful method for assessing the cardiac function in patients with various heart diseases.

Adult↗
PubMedDate not supplied

Cardiac output in asymptomatic primary hyperparathyroidism: a stigma of early cardiovascular dysfunction?

The resting cardiac output pre- and postoperatively in 10 patients with asymptomatic primary hyperparathyroidism has been studied. All patients had normal renal function and arterial blood pressure without a previous history of cardiovascular disease. Ten normotensive patients with a non-toxic goitre awaiting thyroidectomy were studied as controls. The mean cardiac output of the hyperparathyroid patients was 7.2 l/minute (range 5.3-8.9) and of the control group 5.8 l/minute (range 5.2-6.3). Following a successful parathyroidectomy with return of the serum calcium to normal, the mean cardiac output was 6.3 l/minute (range 4.9-7.8) (p < 0.04). In 8 of the 10 patients there was a fall in the cardiac output following surgery; in 2 there was an increase. These results suggest that hyperparathyroid patients often have an elevated cardiac output which may fall following a successful parathyroidectomy.

Adenoma↗
PubMed1989

Clinical evaluation of esophageal doppler cardiac output measurement during general anesthesia.

We evaluate the accuracy of cardiac output measurement with esophageal Doppler ultrasonography (ECO). A total of 71 simultaneous measurement of esophageal Doppler and thermodilution cardiac output were compared in 16 patients undergoing general anesthesia in the supine position. ECO was determined easily with minimal experience, and significantly correlated with thermodilution cardiac output (TDCO) measurement ( P < 0.001). The regression equation obtained was Y = 0.983X + 0.019, and the correlation coefficient was 0.935. Furthermore, ECO was more reproducible than TDCO. However, ECO is not able to assess CO accurately in either lateral or prone position and after cardiopulmonary bypass in open heart surgery. Our results suggest that the esophageal Doppler technique allows a noninvasive and continuous cardiac output monitoring in patients during general anesthesia, and that it is more useful in patients for whom invasive monitoring is considered inappropriate. However, further improvement in this technique will be necessary for its routine use in clinical anesthesia.

Journal Article↗
PubMed1987

Comparison of pulsed Doppler and thermodilution methods for measuring cardiac output in critically ill patients.

We obtained 145 consecutive cardiac output measurements in 38 critically ill patients, using the invasive thermodilution and the noninvasive pulsed Doppler methods. The mean thermodilution cardiac output (TDCO) was 5.7 +/- 1.87 L/min and the mean pulsed Doppler cardiac output (PDCO) was 5.16 +/- 1.66 L/min. The mean difference between the two measurements was 0.51 L/min with an SD greater than 1.6 L/min, reflecting the scattering of results. The overall correlation coefficient was .58. The intercepts were large and the regression equation some way from the line of equal values (TDCO = 2.28 + 0.66 PDCO). When the results were analyzed according to diagnosis or by group experience, there were some differences in the bias of the estimate; however, the SD of the difference between methods was greater than one liter/min in all groups. Thus, the pulsed Doppler method failed to estimate accurately TDCO in critically ill patients.

Cardiac Output↗
PubMed1979

Multiple cardiac output measurements in man. Evaluation of a new closed-system thermodilution method.

Cardiac output estimates by a new closed-system automatic injection thermodilution method (COI-TD) were compared serially with the direct Fick technique (COFICK) and the standard open-system manual injection thermodilution method (COTD). Comparison with cardiac outputs determined simultaneously by the direct Fick technique in 100 measurements involving ten patients showed close agreement with the new closed system method using both 25 degrees C and 3 degrees C injectates. The cardiac output range was between 1.9 to 11.6 L/min. The open-system manual injection thermodilution method under identical conditions produced a wide scatter of measurements when compared to the direct Fick technique. Reproducibility of simultaneous COI-TD and COTD measurements was examined in quadruplicate. The reproducibility of measurements was within 1.9 percent with COI-TD and 5.9 percent with the COTD method using both 25 degrees C and 3 degrees C injectates. The COI-TD method eliminates the technical problems of recirculation, unstable indicator baseline changes, thermal continuity, and reproducibility encountered with the current COTD method. Analysis of cardiac output by the closed-system automatic injection thermodilution method provides a simple, rapid, reproducible, and highly accurate method for multiple cardiac output measurements suitable for use at the bedside.

Cardiac Catheterization↗