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PubMed1992

Heart size and maximal cardiac output are limited by the pericardium.

We tested the hypothesis that the pericardium, by restricting heart size, limits maximal cardiac output and oxygen consumption. We studied 15 pigs. Five underwent maximal treadmill running before and 14-21 days after thoracotomy and pericardiectomy; these pigs also received sequential volume infusions to determine end-diastolic pressure-dimension relationships. Five underwent maximal treadmill running before and 14-21 days after thoracotomy (pericardium undisturbed) to determine the effect of thoracotomy on exercise performance. Finally, five underwent thoracotomy, instrumentation, loose closure of the pericardium, and sequential volume infusions to determine the effect of thoracotomy without pericardiectomy on end-diastolic pressure-dimension relationships. Pericardiectomy caused similar increases in maximal cardiac output (29% increase; P = 0.007) and maximal oxygen consumption (31% increase; P = 0.02). These results were associated with increased left ventricular end-diastolic dimension (10% increase; P = 0.01) and an estimated 33% increase in end-diastolic volume. In addition, left ventricular mass was increased by pericardiectomy (18% increase; P < 0.04). Thus the pericardium, by limiting utilization of the Starling mechanism, limits maximal cardiac output, and the limit to cardiorespiratory performance lies not in oxygen utilization, but in oxygen delivery. Furthermore, removal of pericardium is associated with myocardial hypertrophy.

Animals↗
PubMed1984

Elementary echographic estimation of cardiac output independent of the symmetry and kinetic state of the left ventricle in mitral stenosis. Potential application to the determination of the circulation of pregnancy.

An orifice equation is demonstrated which is independent of the symmetry and kinetic state of the left ventricle. The expression allows calculation of the cardiac output in conditions of mitral stenosis when the mitral valve area is known. This equation is Q = (1/21) R A T2, where Q = cardiac output in ml/min, R = heart rate, A = mitral valve area and T = diastolic filling period in sec/min. Ten patients whose gynecologic or obstetric exam suggested a diagnosis of mitral stenosis were evaluated by conventional cardiac catheterization and M-mode echocardiography. Cardiac output computed using the new equation and the Fick principle corresponded at r = 0.95, SE = 340 ml, N = 10. These results suggest that cardiac output may be conveniently estimated for serial studies by the readily measurable echographic variables of heart rate and diastolic filling period once the mitral valve area has been measured by conventional catheterization or bi-dimensional echographic methods.

Adolescent↗
PubMed2005

Use of lithium dilution and pulse contour analysis cardiac output determination in anaesthetized horses: a clinical evaluation.

OBJECTIVE: To assess the suitability of a human algorithm for calculation of continuous cardiac output from the arterial pulse waveform, in anaesthetized horses. STUDY DESIGN: Prospective clinical study. ANIMALS: Twenty-four clinical cases undergoing anaesthesia for various conditions. MATERIALS AND METHODS: Cardiac output (Qt), measured by lithium dilution (QtLiDCO), was compared with a preceding, calibrated Qt measured from the pulse waveform (QtPulse). These comparisons were repeated every 20-30 minutes. Positive inotropes or vasopressors were administered when clinically indicated. Cardiac indices from 30.7 to 114.9 mL kg(-1) minute(-1) were recorded. Unusually shaped QtLiDCO curves were rejected and the measurement was repeated immediately. RESULTS: Eighty-nine comparisons were made between QtLiDCO and QtPulse. The bias between the mean (+/-SD) of the two methods (QtLiDCO - QtPulse) was -0.07 L minute(-1)(+/-3.08) (0.24 +/- 6.48 mL kg(-1) minute(-1)). The limits of agreement were -12.72 and 13.2 mL kg(-1) minute(-1) (Bland & Altman 1986; Mantha et al. 2000). Linear regression analysis demonstrated a correlation coefficient (r2) of 0.89. Cardiac output in individual patients varied from 49.1 to 183% of the initial measurement at the time of calibration. Linear regression of log-transformed Qt variation for each method found a mean difference of 9% with limits of agreement of -4.1 to 22.1%. CONCLUSIONS AND CLINICAL RELEVANCE: This method of pulse contour analysis is a relatively noninvasive and reliable way of monitoring continuous Qt in the horse under anaesthesia. The ability to easily monitor Qt might decrease morbidity and mortality in the anaesthetized horse.

Anesthesia, General↗
PubMed1980

Changes of cardiac output caused by aging: an impedance cardiographic study.

The various parameters of cardiac output were studied in 132 healthy subjects from 20 to 89 years of age by impedance cardiography. This noninvasive method supplied data that were similar to those found by others by dye dilution methods. All parameters of cardiac output decrease with age. However, we found a difference between the two sexes in the rate of decrease of the cardiac index: women had a more marked drop at an earlier age and then a steady course, while men had a progressive decrease from the youngest to the oldest group.

Adult↗
PubMed2002

Measuring cardiac output during dobutamine infusion after off-pump coronary artery bypass: comparison of transesophageal echo-Doppler and thermodilution.

AIM: To compare transesophageal echo-Doppler with thermodilution method for measuring cardiac output during dobutamine infusion after off-pump coronary artery bypass. METHOD: Using transesophageal echo-Doppler and thermodilution methods, we measured cardiac output in 30 patients after off-pump coronary artery bypass, immediately before and 5, 15, and 30 min after the introduction of continuous dobutamine infusion (3 microg/kg/min). Paired t-test and Bland-Altman analysis were used to compare the results obtained by two methods in this prospective study. RESULTS: Significant increase in cardiac output during dobutamine infusion was detected by both thermodilution (from 3.9 +/- 1.0 to 4.6 +/- 1.1 L/min; p < 0.001) and transesophageal echo-Doppler (from 3.8 +/- 1.2 to 4.8 +/- 1.4 L/min; p < 0.001). Initial measurement results of thermodilution and transesophageal echo-Doppler techniques showed clinically acceptable agreement, with a mean difference of only + 0.09 L/min (95% confidence interval (CI), 0.42 to + 0.61). Subsequently repeated measurements after 5, 15, and 30 min showed almost the same agreement between the methods. The highest mean difference between the initial and repeated measurements was found at 5 min after the introduction of dobutamine infusion (-0.29 L/min, 95% CI, -1.06 to + 0.48). CONCLUSION: Transesophageal echo-Doppler and thermodilution can be interchangeable as methods for measuring cardiac output after off-pump coronary artery bypass.

Adult↗
PubMed1986

Cardiac output changes secondary to theophylline therapy in preterm infants.

The cardiovascular effects of theophylline were studied in 11 clinically stable preterm infants. Theophylline was given as aminophylline using a loading dose of 6.8 mg/kg and a maintenance dose of 2 mg/kg every 8 hours intravenously. Cardiac output, stroke volume, and heart rate were measured using a combination of pulsed Doppler ultrasound and M-mode echocardiography. Compared with day 0, an increase was found in both cardiac output (P less than 0.01) and stroke volume (P less than 0.02) on days 1, 2, and 3. By day 7, stroke volume was comparable to pretreatment values, whereas cardiac output was still increased. Heart rate was augmented significantly (P less than 0.01) throughout the treatment period. Mean arterial blood pressure did not change. All but one of the neonates had serum theophylline concentrations between 6 and 13 mg/L. We conclude that both inotropic and chronotropic effects are evident during the first days of theophylline therapy. The metabolic cost of the increased cardiac output in the preterm infant with theophylline therapy deserves further attention.

Aminophylline↗
PubMed1992

Sham-feeding decreases cardiac output in normal subjects.

The cardiovascular effect of sham-feeding was measured in seven healthy non-obese human subjects by the Fick principle using the carbon dioxide rebreathing method. The subjects were resting in the sitting position and were exposed to the sight and smell but not the taste of a breakfast meal. Cardiac output decreased significantly from a mean value of 4.0 1 min-1 to 3.5 1 min-1 during sham-feeding (Friedman, P = 0.004). The cardiac output returned to basal values in all seven subjects when the sensory stimulus was removed. The decrease in cardiac output was due to a decreased stroke volume, whereas heart rate and blood pressure did not change. The mechanism of the decrease in cardiac output during sham-feeding remains to be established.

Adult↗
PubMedDate not supplied

In vitro testing of a new driver for the pneumatic total artificial heart with inherent cardiac output measuring system.

Based upon the Utah pneumatic driver, a new model for use in animal experiments was designed. It enabled measurement of cardiac output, optimal percentage of systole as well as diagnosis of some of the causes of the decrease of cardiac output of the pneumatic total artificial heart, such as valvular stenosis due to pannus formation. This driver is based on the expansion of a known amount of 'driving-air' during the systolic period. In the calculation of the cardiac output, the in vitro experiments yielded an error range of +/- 3.5%. The analysis of the driving-air pressure tracing during its decompression (systolic period) gave accurate information about the optimal percentage of systole for each frequency and the inflow and outflow resistances.

Automobile Driving↗
PubMed1999

A meta-analysis of studies using bias and precision statistics to compare cardiac output measurement techniques.

INTRODUCTION: Bias and precision statistics have succeeded regression analysis when measurement techniques are compared. However, when applied to cardiac output measurements, inconsistencies occur in reporting the results of this form of analysis. METHODS: A MEDLINE search was performed, dating from 1986. Studies comparing techniques of cardiac output measurement using bias and precision statistics were surveyed. An error-gram was constructed from the percentage errors in the test and reference methods and was used to determine acceptable limits of agreement between methods. RESULTS: Twenty-five articles were found. Presentation of statistical data varied greatly. Four different statistical parameters were used to describe the agreement between measurements. The overall limits of agreement in studies evaluating bioimpedance (n = 23) was +/-37% (15-82%) and in those evaluating Doppler ultrasound (n = 11) +/-65% (25-225%). Objective criteria used to assess outcome were given in only 44% of the articles. These were (i) limits of agreement approaching +/-15-20%, (ii) limits of agreement of less than 1 L/min, and (iii) more than 75% of bias measurements within +/-20% of the mean. Graphically, we showed that limits of agreement of up to +/-30% were acceptable. CONCLUSIONS: When using bias and precision statistics, cardiac output, bias, limits of agreement, and percentage error should be presented. Using current reference methods, acceptance of a new technique should rely on limits of agreement of up to +/-30%.

Bias↗
PubMed1989

[Comparative investigation of cardiac output using impedance rheography and invasive methods].

Authors performed comparative measurements of cardiac output using the impedance rheography and Fick's method in healthy men (6) reaching the value of correlation coefficient 0.88 and in patients with acquired cardiac defects (n = 21; r = 0.68). Authors also compared cardiac output values measured at rest and during exercise by means of thermodilution and rheographic methods in patients with heart failure (n = 9). Correlation coefficient was respectively 0.92 and 0.81.

Adult↗
PubMed1959

The central action of lignocaine and its effect on cardiac output.

Fifty-nine tests were performed on twenty-four anaesthetized dogs in a study of the effects of lignocaine on circulatory and respiratory functions. In single-dog experiments, it was shown that lignocaine (1 to 2 mg./kg. body weight) increased ventilation somewhat, but had no effect on O(2) consumption. Cardiac output was increased due to a rise in both heart rate and stroke volume. There was an elevation of arterial blood pressure. The central blood volume was increased, but central venous pressure, total peripheral resistance and the ventilationperfusion ratio were decreased. The increase in cardiac output after lignocaine was abolished both in decerebrate and in vagotomized dogs. In cross-circulation experiments with dogs, it was demonstrated that the primary site of action of lignocaine on cardiac output was central. The effect of lignocaine on cardiac output could be blocked by intravenous procaine.

Animals↗
PubMed1998

Non-invasive assessment of cardiac output in children.

BACKGROUND: Stroke distance, the systolic velocity integral of aortic blood flow, is a linear analogue of stroke volume; its product with heart rate is minute distance, analogous to cardiac output. OBJECTIVE: To investigate the feasibility of assessing cardiac output in children with a simple non-invasive Doppler ultrasound technique, and to determine the normal range of values. METHODS: Peak aortic blood velocity, stroke distance, and minute distance were measured through the suprasternal window in 166 children (mean age 9.6 years, range 2-14) using a portable non-imaging Doppler ultrasound instrument. RESULTS: The technique was well tolerated by all the children participating. Mean peak aortic blood velocity was 138 cm/s and was independent of age. Mean stroke distance was 31.8 cm and showed a small but significant increase with age; mean minute distance was 2490 cm and fell with age, as did heart rate. CONCLUSIONS: Suprasternal Doppler ultrasound measurement of stroke distance is a convenient, well tolerated, non-invasive technique for the assessment of cardiac output in children. The normal range of values during childhood has been established. The technique has great potential for assessing hypovolaemia in children.

Adolescent↗
PubMed2000

Comparison of cardiac output measured by two automated methods of CO2 rebreathing.

PURPOSE: The aim of the present study was to investigate the reproducibility of the exponential method of CO2 rebreathing with the use of automated curve fitting and to determine whether this method is superior to the equilibrium method in terms of reproducibility and clinical practicability. METHODS: Repeated measurements of cardiac output were performed using the automated equilibrium and exponential methods. These measurements were compared in 12 healthy male subjects at rest and during incremental exercise tests. RESULTS: Estimated cardiac output was not significantly different between duplicate measurements at rest nor at any level of exercise with either method. At rest the exponential method showed a tendency toward larger variability than the equilibrium method. The exponential method produced significantly higher (P < or = 0.001) estimates at rest (averaging up to 9.8 L x min(-1)) compared with the equilibrium method (averaging up to 6.5 L x min(-1)). Reproducibility improved for both methods with increasing workloads, and a second measurement at rest also seemed more reproducible and valid than the first. During exercise, both methods produced comparable values for cardiac output, and highly significant relations between cardiac output and oxygen uptake were observed for both methods (ranging from r2 = 0.79 to r2 = 0.88, P < or = 0.001). The equilibrium method produced unpleasant side effects more frequently (75% vs 21%, P < or = 0.001) compared with the exponential method and lead more subjects to premature interruption of the exercise test because of the rebreathing maneuver (42% vs 17%, P = 0.058). CONCLUSIONS: Automated curve fitting for the exponential method gave reproducible and valid results during submaximal and maximal exercise but not at rest. The equilibrium method on the other hand interfered with exercise. Therefore, the equilibrium method is recommended at rest and at lower levels of exercise and the exponential method at higher intensities.

Adolescent↗
PubMed1986

Ventricular volume and ejection fraction in the diagnosis of the aetiology of low cardiac output in burned patients.

Cardiovascular instability following burns may result from either cardiac or non-cardiac causes. We illustrate three cases in whom routine measurements of atrial filling pressures and cardiac output alone did not reflect the adequacy of blood volume or the myocardial performance. In each instance, measurements of ventricular volume and ejection fraction by thermodilution technique or 99mTC ventriculography were useful to determine the actual causes of decreased cardiac output.

Adult↗
PubMed2001

Arterial thermodilution: an alternative to pulmonary artery catheter for cardiac output assessment in burn patients.

STUDY OBJECTIVE: To study the agreement between cardiac output measurements with the pulmonary artery catheter and with the transpulmonary thermodilution technique in patients with burns. DESIGN: Prospective, clinical study. PATIENTS: 23 patients with serious burns and an abbreviated burn severity index score (ABSI)>6. SETTING: intensive care unit for severely burned in a burn center in Germany. RESULTS: A total number of 218 cardiac output measurements obtained during the first 72 h postburn were analysed. In the pulmonary artery group, mean cardiac index was 3.93 l/min/m2 and ranged from 0.96 to 9.58. In the transpulmonary group the cardiac index measurements ranged from 0.96 to 9.61 with a mean of 4.0 l/min/m2. During the entire observation period cardiac index was consistently higher in the transpulmonary group than in the pulmonary artery group with a bias of 0.32 l/min/m2 and a standard deviation (S.D.) of 0.29 l/min/m2. Linear regression analysis revealed CI(arterial)=0.98xCI(pulm)+0.22l/min/m2 (r=0.9678, P<0.038). Bias and precision to each time point according to Bland and Altman demonstrated a good agreement between both techniques. CONCLUSION: The transpulmonary thermodilution offers an attractive, less invasive alternative to the pulmonary artery catheter in patients with burns. Arterial thermodilution for CO measurements is as precise as PA thermal dilution, and CO(pulm) can be replaced by CI(arterial) when basic methodological principles are respected.

Adult↗
PubMed1988

The effects of hypoxemia on cardiac output. A dose-response curve.

To establish a dose-response curve for the effects of isocapnic hypoxemia on cardiac output (CO), we studied 20 healthy men, aged 20 to 34 years, using a tight-fitting face mask and an isocapnic partial rebreathing system (a modified anesthesia machine). We blended oxygen and hypoxic gas to achieve arterial oxygen saturations (SaO2) of 80, 85, and 90 percent; subjects also breathed 100 percent oxygen and room air (RA). Target SaO2 and end-tidal carbon dioxide were continuously monitored using an ear oximeter and CO2 gas analyzer. Subjects experienced the five SaO2 measurements in random order. CO was measured noninvasively at approximately two-minute intervals, using continuous-wave Doppler echocardiography. Mean cardiac output increased with increasing hypoxemia from 6.84 L/min at FIo2 1.0 to 8.44 L/min at SaO2 80 percent (p less than 0.0005); the increase was entirely due to increased heart rate. We concluded that cardiac output increases significantly in a dose-response manner in response to acute isocapnic hypoxemia in normal persons.

Acute Disease↗
PubMed1997

Large increase in cardiac output in a patient with ARDS and acute right heart failure during inhalation of nitric oxide.

BACKGROUND: Inhaled nitric oxide (NO), a selective pulmonary vasodilator, reduces pulmonary artery pressure in patients with acute respiratory distress syndrome (ARDS). In spite of the reduction of right ventricular afterload, the effect of NO on cardiac output remains unclear. METHODS: A patient with ARDS and echocardiographically determined severe acute right heart failure was treated with increasing concentrations of inhaled nitric oxide (NO). Haemodynamic and gas exchange variables were determined for each concentration of NO. NO treatment was continued for 3 days. RESULTS: During initial right heart failure, administration of NO resulted in a large increase (32%) in cardiac output in a dose-dependent manner. When right ventricular function had improved, inhalation of NO did not increase cardiac output. CONCLUSION: Our observations suggest that inhalation of NO is likely to increase cardiac output in ARDS when severe acute right heart failure is present.

Acute Disease↗