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At least 1,531 records · Page 85Linked to original sources
PubMed1976

On-line computation of cardiac output with the thermodilution method, using a digital minicomputer.

In the present study, several techniques for calculating cardiac output were evaluated in order to find an accurate technique suitable for on-line digital computation. The thermodilution method was evaluated by different calculation techniques and by comparing these techniques with electromagnetic flowmeter values. Comparison of thermal dilution curves, manually calculated by the log-normal and the exponential assumption, showed a correlation coefficient of 0.978 between the two methods, the former values being 11% higher. The exponential method correlated very well with the technique, using a correction factor for injection errors (r = 0.999). Since the exponential technique correlated well with the electromagnetic values (r = 0.84) and since it was less complicated than the technique, using correction factors, this technique was chosen for automation. Comparison of exponential calculated thermodilution values with a digital computer and manually, showed a correlation coefficient of 0.991. Therefore, it was concluded that on-line computation of thermodilution curves improves the applicability of the termodilution techniques as a means of measuring cardiac output.

Animals↗
PubMed1977

Cardiac output following adrenomedullary deprivation.

This study was performed to determine whether or not the adrenal medulla supports cardiac output and total peripheral vascular resistance after acute hypovolemia. Two groups of anesthetized dogs were studied. The first group underwent right adrenalectomy and the second, left adrenal denervation in addition. Adrenocortical function, as reflected by compound F and dihydroepiandrosterone determinations, was equally maintained in both groups for 120 minutes after hemorrhage. Arterial plasma concentrations of norepinephrine and epinephrine were low in group 2, p greater than 0.05 to greater 0.01. Cardiac index and peripheral vascular resistance were comparable in both groups before and for two hours after the induction of hypovolemia to a mean arterial pressure of 50 millimeters of mercury. The findings indicate that cardiac output and total peripheral resistance do not require adrenomedullary catecholamine release after acute hypovolemia.

Adrenal Cortex↗
PubMed1988

Relationships between heart rate, exercise tolerance and cardiac output in atrial fibrillation: the effects of treatment with digoxin, verapamil and diltiazem.

Six patients with chronic atrial fibrillation (AF) took single doses of digoxin, verapamil and diltiazem, alone and in combination. Three hours after dosing, resting and post-exercise heart rate, exercise tolerance and resting and post-exercise cardiac output were measured. Post-exercise heart rates ranged from 167 bpm (after placebo) to 122 bpm (after digoxin plus diltiazem) (P less than 0.05). However, the lower ventricular rates seen after treatment with the calcium antagonists were not associated with improved exercise tolerance, which did not differ significantly between the various treatments. Reduction of the ventricular rate was associated with a small increase in stroke volume but the benefits of this were offset by a rate related reduction in cardiac output. Further reduction of the rapid ventricular rates seen in digitalized patients with AF does not appear to be of benefit in terms of improving either exercise tolerance or cardiac output.

Aged↗
PubMed1992

William Harvey, Peter Lauremberg and cardiac output.

In 1636, the Rostock professor of medicine and the art of poetry, Peter Lauremberg (1585-1639), was one of the earliest to mention circulation which had been discovered by William Harvey and documented in his anatomical manual. In 1628 William Harvey proved the existence of the blood circulation by calculating the "cardiac output in a half an hour (semihora)". The answer to the question why Harvey chose half an hour as the time range can be found in the way of measuring time usual at that period. The sandglasses were turned half-hourly in maritime navigation and the wheel-clocks on shore had only the hour-hand. Improved chronometry was one of the prerequisites for measuring cardiac output. The minute-hand became usual after 1700 and the second-hand later on. Taking into consideration the alterations of cardiac output made the latter one of the most important circulation parameters in diagnostics, prognostication and therapeutics.

Blood Circulation↗
PubMed2003

Effect of extracellular volume expansion and surgical stress on splanchnic blood flow and cardiac output in anesthetized rats: role of nitric oxide.

In a normal volume state, surgical stress decreases rather than increases nitric oxide (NO) production in the vascular system. In our studies, the effect of minor and major surgical stress and three different degrees of volume expansion on systemic and splanchnic circulatory parameters and on the NO dependence of the circulation have been investigated. When the degree of volume expansion was increased, cardiac output and organ blood flow increased without significant change in vascular resistances. Major surgical stress reduced the increase in cardiac output and organ blood flow elicited by the volume expansion. NO synthase (NOS) inhibition significantly increased blood pressure and total peripheral resistance (TPR) and decreased cardiac output in all groups of animals. As the degree of volume expansion was increased, the NO dependence of the circulation in the surgically less- and more-stressed animals was inversely influenced in some cases. With the three degrees of volume expansion (20, 40, and 60 ml/kg), the NOS inhibition increased the TPR from 30.7 R/kg +/- 1.90 to 73.6 R/kg +/- 5.00, from 20.7 R/kg +/- 1.43 to 66.7 R/kg +/- 3.88, and from 19.9 R/kg +/- 1.25 to 49.1 R/kg +/- 3.84 in the surgically less-stressed animals and from 38.6 R/kg +/- 2.14 to 59.8 R/kg +/- 5.62, from 31.9 R/kg +/- 2.70 to 81.7 R/kg +/- 9.89, and from 29.1 R/kg +/- 2.49 to 91.1 R/kg +/- 6.36 in the surgically more-stressed animals. Volume expansion increases the NO dependence of the vascular resistance in the surgically more-stressed animals but decreases it in the surgically less-stressed animals.

Abdominal Cavity↗
PubMed1989

Single-breath breath-holding estimate of pulmonary blood flow in man: comparison with direct Fick cardiac output.

1. Resting pulmonary blood flow (Q), using the uptake of the soluble inert gas Freon-22 and an indirect estimate of lung tissue volume, has been estimated during breath-holding (Qc) and compared with direct Fick cardiac output (Qf) in 16 patients with various cardiac disorders. 2. The effect of breath-hold time was investigated by comparing Qc estimated using 6 and 10 s of breath-holding in 17 patients. Repeatability was assessed by duplicate measurements of Qc in the patients and in six normal subjects. 3. Qc tended to overestimate Qf, the bias and error being 0.09 l/min and 0.59, respectively. The coefficient of repeatability for Qc in the patients was 0.75 l/min and in the normal subjects was 0.66 l/min. For Qf it was 0.72 l/min. There was no significant difference in Qc measured at the two breath-hold times. 4. The technique is simple to perform, and provides a rapid estimate of Q, monitoring acute and chronic changes in cardiac output in normal subjects and patients with cardiac disease.

Adult↗
PubMedDate not supplied

[The determination of cardiac output by the dilution of ultrasonic blood density].

The authors propose assessing cardiac output (CO) by diluting the blood ultrasonic properties. For measuring CO, the peripheral artery and vein were connected with a catheter, and ultrasonic flowmetric pickup was attached to the shunt. Indicator (0.9% sodium chloride) was injected into the central vein. Changes in the blood ultrasonic characteristics during the indicator flow were recorded by ultrasonic flowmeter. Dilution curves were computer processed. The method was tried in 7 experimental dogs and clinically in 11 patients and compared with the thermodilution method. The coefficient of correlation was 0.98 in experiment and 0.97 in clinical trials. Dilution of ultrasonic density of the blood helps accurately assess the CO and is highly informative, which is confirmed by a strong correlation with the results of thermodilution. The method is simple, little invasive, realized using available equipment, the indicators are cheap and available, and repeated studies can be performed within short periods of time.

Animals↗
PubMed1987

Noninvasive Doppler assessment of human postprandial renal blood flow and cardiac output.

We compared the effects of protein, carbohydrate, or water ingestion on human renal blood flow (RBF) and cardiac output (CO). We validated and applied a noninvasive ultrasonic Doppler method to measure blood velocities and lumen diameters in the right renal artery and the ascending aorta of five healthy adults. From these measurements, we calculated the average RBF and CO over five cardiac cycles. Normalizing to body surface area, renal blood flow index to one kidney (RI) and cardiac index (CI) were calculated. The percentage of the CI distributed to a single kidney was determined as %CI = RI/CI. Subjects were studied randomly on three separate days after ingestion of each of the following equivolume (500 ml) meals: 1) 150 g protein, 30 g fat, and 30 g carbohydrate (P); 2) 150 g carbohydrate, 30 g fat, and 30 g protein (C); and 3) water. Data were obtained after 12 h of fasting and at 30, 60, 90, 120, 180, and 240 min postprandially. Analysis of covariance revealed significant (P less than 0.05) increases from fasting levels in postprandial RI at 90 to 240 min after P. Postprandial RI with P was significantly higher than with C at 180 and 240 min. Postprandial %CI with P and C decreased significantly from the fasting value at 30 to 180 min. Heart rate and mean arm cuff blood pressure did not change significantly with any diet. Results suggest that the protein-rich meal evokes a more sustained increase in postprandial RI than the carbohydrate rich meal. Despite the increase in postprandial RI, the percentage of cardiac output perfusing a kidney declines similarly with both diets.

Adult↗
PubMed2006

Interrater reliability of cardiac output measurements by transcutaneous Doppler ultrasound: implications for noninvasive hemodynamic monitoring in the ED.

INTRODUCTION: Hemodynamic monitoring is an important aspect of caring for the critically ill patients boarding in the emergency department (ED). The purpose of this study is to investigate the interrater agreement of noninvasive cardiac output measurements using transcutaneous Doppler ultrasound technique. METHODS: This is a prospective observational cohort study performed in a 32-bed adult ED of an academic tertiary center with approximately 65000 annual patient visits. Patients were enrolled after verbal consent over a 7-month period. The raters were ED personnel involved in patient care. Paired measurements of cardiac index (CI) and stroke volume index (SVI) were obtained from a transcutaneous Doppler ultrasound cardiac output monitor. RESULTS: A convenience sample of 107 (50 women and 57 men) patients with a median age of 49 (32, 62) years was enrolled. One hundred two paired measurements were performed in 91 patients in whom adequate Doppler ultrasound signals were obtainable. The raters included 35 emergency medicine attending physicians, 31 emergency medicine residents, 80 medical students, 47 nurses, and 11 emergency medical technicians. Cardiac index range was 0.6 to 5.3 L/min per square meter, and SVI range was 7.7 to 63.0 mL/m(2). The correlation of CI measurements between 2 raters was good (r(2) = 0.87; 95% confidence interval, 0.86-1.00; P < .001). Likewise, SVI measurements between 2 raters also showed acceptable correlation (r(2) = 0.84; 95% confidence interval, 0.81-0.96; P < .001). Interrater reliability was strong for CI (kappa = 0.83 with 92.2% agreement) and SVI measurements (kappa = 0.72 with 88.2% agreement). Most patients had an interrater difference below 10% in CI and SVI measurements. CONCLUSIONS: Emergency department personnel, regardless of their role in patient care, are able to obtain reliable cardiac output measurements in ED patients over a wide range of CI and SVI. Transcutaneous Doppler ultrasound technique may be an alternative to traditional invasive hemodynamic monitoring of critically ill patients presenting to the ED.

Adult↗
PubMed1983

Errors in calculating cardiac output due to administration of perfluorochemicals.

Intravenous administration of perfluorochemicals (PFC) will alter the density (rho)B, the gravimetric specific heat (c)B, and the volumetric specific heat (rho c)B of blood. Changes in hematocrit also influence (rho c)B. The calibration constant employed in the determination of cardiac output (CO) by thermal dilution depends inversely on (rho c)B. We estimate the effect of addition of PFC and changes in hematocrit on (rho c)B. Consider blood to be a mixture of red cells, emulsified PFC particles, and plasma. This leads to the equation: (rho c)cB = 0.96 - 0.11Hct - 0.48Fct. Here Hct and Fct are the fractional volume concentrations of red blood cells and PFC, and (rho c)cB is the calculated specific heat based on the actual composition of blood. CO can be corrected for changes in (rho c)B by the equation: (CO)c = [(rho c)sB/(rho c)cB](CO)o. Here (CO)o is the observed cardiac output, (rho c)sB is the standard specific heat of blood used in the calculation of (CO)o, and (CO)c is the corrected cardiac output. We have observed laboratory situations where the correction factors have been as high as 10%.

Cardiac Output↗
PubMed1975

Evaluation of portable radionuclide method for measurement of left ventricular ejection fraction and cardiac output.

Seventeen patients with coronary artery, valvular, or myopathic heart disease were studied to determine correlations of the cardiac output and ejection fraction when comparing the results obtained with a portable probe technique using 113mIn with those obtained with standard methods (cineangiographic, Fick, and dye dilution). With ejection fractions ranging from o.10 to 0.85, the coefficient of correlation was 0.90 when comparing cineangiographic and radionuclide techniques. Cardiac output determinations by the radionuclide technique also correlated well with standard methods (r equals 0.88). The radionuclide method shows promise as an accurate, safe, and simple method in the evaluation of cardiac function at the bedside.

Angiocardiography↗
PubMed1992

Factors enhancing cardiac output in resting subjects during cold exposure in air environment.

Six young males, in semi-nude conditions, resting in dorsal reclining position, were exposed successively to a thermoneutral environment (30 min), a cold environment (1 degree C) (Cold) or thermoneutrality (Control) (120 min), and during 60 min recovery in thermoneutral conditions. Cardiac output has been measured using a Dual Beam Doppler. During cold stress a significant increase of heart rate (66.4 +/- 6.4 to 91.0 +/- 14.9 beats.min-1), systolic blood pressure (119.5 +/- 7.8 to 218.7 +/- 18.7 mmHg), diastolic blood pressure (68.1 +/- 11.7 to 114.3 +/- 28.3 mmHg) and cardiac output (5.42 +/- 0.96 to 8.08 +/- 1.28 l.min-1) were observed. On the contrary initial systolic aorta flow acceleration is significantly lowered (1130 +/- 120 to 840 +/- 170 cm.s-2). Systolic ejection volume remained unchanged throughout the whole experiment. Increase in cardiac output during cold air (1 degree C) exposure is thus only imputed to the higher heart rate partly due to hypersecretion of catecholamines. The diminution of the blood flow acceleration could be related to a lesser arterial compliance and/or to the cold induced hemoconcentration. Enhanced heart's mechanical work due to sympathetic stimulation, seems thus to be absorbed by the increase in the peripheral resistance.

Adult↗