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PubMed1993

Managing low cardiac output states: maintaining volume after cardiac surgery.

Low cardiac output after cardiac surgery may be caused by hypovolemia, myocardial depression, vasoconstriction, and dysrhythmias. Postoperative hypovolemia occurs because of blood volume loss and decreased diastolic filling. Diuresis, intravascular fluid shift into the interstitium, hormonal influences, and bleeding deplete blood volume. Diastolic filling may be compromised by positive end-expiratory pressure, vasodilation, dysrhythmias, and venous return obstruction. The primary indicator of intravascular volume is ventricular preload, which may be measured indirectly with central venous pressure, left atrial pressure, or pulmonary capillary wedge pressure. Recognition of hypovolemia is aided through the use of cardiac pressure trend monitoring and evaluation of noninvasive indicators of hypovolemia. Nursing goals, in response to hypovolemia, are to increase the circulating volume, optimize oxygen delivery, stabilize hemodynamics, improve tissue perfusion, and prevent shock.

Aged↗
PubMed2004

Cardiac output monitoring by pressure recording analytical method in cardiac surgery.

OBJECTIVE: A less-invasive method has been developed that may provide an alternative to monitor cardiac output from arterial pressure: beat-to-beat values of cardiac output can be obtained by pressure recording analytical method (PRAM). The purpose of this study was to assess the reliability of cardiac output determination by PRAM in cardiac surgery. METHODS: Cardiac output was measured in 28 patients undergoing coronary artery bypass grafting at 15 min after anaesthesia induction, 30 min after extracorporeal circulation, 1 and 3 h after arrival in the intensive care unit using thermodilution (ThD) method through a pulmonary artery catheter and PRAM. ThD cardiac output was calculated as the mean of five separate measurements. PRAM provided beat-by-beat cardiac output data continuously throughout the study and the cardiac output values displayed on a dedicated personal computer at each time point were recorded. Correlations were calculated and differences were compared by Bland-Altman analysis. RESULTS: A total of 112 measurements were obtained. Cardiac output ranged from 2.3 to 7.4 l/min, and a good linear correlation (R2=0.78, P<0.0001) was found between ThD and PRAM. The highest degree of correlation (R2=0.86) was obtained at 3 h after arrival in the intensive care unit. The lower degree of correlation (R2=0.70) was obtained 30 min after extracorporeal circulation. At Bland-Altman analysis, the overall estimates of cardiac output measured by PRAM closely agreed with ThD (mean difference, 0.027; standard deviation, 0.43; limits of agreement, -0.83 and +0.89). CONCLUSIONS: Under the studied conditions, our results demonstrate good agreement between PRAM data and ThD measurements, and this new method has shown to be accurate for real-time monitoring of cardiac output in cardiac surgery. Further studies will be required to assess this method in higher-risk patients and in the setting of haemodynamic instability or arrhythmias. This is the first study designed to assess the accuracy of PRAM in cardiac surgery.

Aged↗
PubMed1981

Simultaneous computer-calculated carbon dioxide and oxygen direct Fick and dye dilution measurements of cardiac output in dogs.

Cardiac output was measured by both indocyanine green dye dilution and the direct Fick method using computer-calculated values for oxygen consumption and carbon dioxide excretion in eight mechanically ventilated dogs anesthetized with pentobarbital, with either tubocurarine or succinylcholine intravenous drip for neuromuscular relaxation. Sequential measurements were made during the anesthesia and in response to pharmacologically induced increased cardiac output using doxapram hydrochloride (1.5 mg/kg) given intravenously. The purpose of this project was to investigate the accuracy and reliability of the direct Fick measurements during anesthesia using computer-calculated measurements of pulmonary gas exchange and, since, these measurements have not been reported in detail previously, to establish tentative control values for future projects. The correlation of dye and direct Fick measurements of cardiac output during the first hour after induction of anesthesia was very good (r = 0.85 for all dye-carbon dioxide Fick values; r = 0.83 for all dye-oxygen Fick values.

Anesthesia, Intravenous↗
PubMed2006

Arterial pulse wave analysis: An accurate means of determining cardiac output in children.

OBJECTIVE: Cardiac output is a useful measure of myocardial performance. Standard methods of determining cardiac output are not without risk and can be problematic in children. Arterial pulse wave analysis (PulseCO), a novel, minimally invasive cardiac output determination technique, offers the advantage of continuous monitoring, convenience, and low risk. This technique has not been validated in children. The purpose of this study was to validate PulseCO as an accurate means of noninvasively determining real-time cardiac output in children. DESIGN: Prospective, single-center evaluation. SETTING: Children's hospital. PATIENTS: Any child with a structurally normal heart, undergoing hemodynamic evaluation in the cardiac catheterization laboratory, was included. INTERVENTIONS: A prograde right heart catheterization was performed, and cardiac output was determined using the thermodilution technique, via placement of a pulmonary arterial catheter. MEASUREMENTS AND MAIN RESULTS: Thermodilution results were compared with continuous real-time cardiac output measurements obtained with the PulseCO system, and they were then analyzed by standard correlation techniques and Bland-Altman analysis. Twenty patients were evaluated with a median age of 10.5 yrs and a median weight of 25 kg. The mean thermodilution cardiac index was 3.3 +/- 0.9 L/min/m, whereas the mean PulseCO cardiac index was 3.1 +/- 0.9 L/min/m. Standard Pearson correlation tests revealed a correlation coefficient of .94 (p < .001). Bland-Altman analysis revealed excellent clinical agreement with a mean difference of 0.19 L/min/m and a precision of 0.28 L/min/m at 2 sd. CONCLUSIONS: Arterial pulse wave analysis by the PulseCO system provides a novel, minimally invasive method of determining real-time cardiac output in children.

Adolescent↗
PubMed2005

Cardiac output measurement by pulse dye densitometry in cardiac surgery.

Summary The aim of this study was to compare the accuracy of pulse dye densitometry with that of bolus thermodilution cardiac output measurement in patients before and after elective coronary artery bypass grafting. Twenty-eight patients were studied. Agreement between mean thermodilution and pulse dye densitometry cardiac output values was assessed by Bland-Altman analysis. Preoperative median [range] cardiac output was 3.87 [2.37-6.0] l.min(-1) by thermodilution, and 3.11 [1.7-5.45] l.min(-1) by pulse dye densitometry using indocyanine green 5 mg. Pulse dye densitometry underestimated cardiac output (mean bias - 0.42 l.min(-1)); the limits of agreement were +/- 1.91 l.min(-1), and mean error was 50.3%, indicating low precision. Preoperative median [range] cardiac output was 3.85 [2.2-6.0] l.min(-1) for bolus thermodilution cardiac output and 4.2 [2.0-7.2] l.min(-1) for pulse dye densitometry using indocyanine green 20 mg. Mean bias was + 0.566 l.min(-1), the limits of agreement were +/- 2.51 l.min(-1) and mean error was 60.9%. Postoperative cardiac output data were not analysed because pulse dye densitometry signals were low or absent in > 50% of the patients. We conclude that pulse dye densitometry using indocyanine green 5 mg or 20 mg is inaccurate in anaesthetised patients before coronary artery bypass surgery and cannot be used after surgery because of a high incidence of low pulse dye densitometry signal amplitudes.

Aged↗
PubMed1987

Left ventricular derived cardiac output.

Measurement of cardiac output (CO) requires right-sided cardiac catheterization. However, to save time and reduce costs, only left-sided cardiac catheterization is usually performed in most patients with suspected coronary artery disease. Thus, CO is not measured. To determine if CO can be measured from the left side of the heart, 24 patients undergoing cardiac catheterization had near-simultaneous determination of CO after indocyanine green dye was injected into the pulmonary artery and left ventricular (LV) cavity. There was close agreement between pulmonary artery and LV derived cardiac outputs (Pulmonary artery = 0.93 LV + 0.12). The pulmonary artery derived CO was 5.7 +/- 2.0 liters/min and the LV derived CO was 6.1 +/- 2.2 liter/min. Also, there was a close relation between pulmonary artery derived stroke volume (82 +/- 33 ml) and LV derived stroke volume (86 +/- 36 ml). Thus, CO can be accurately measured after injection of indocyanine green dye into the LV cavity.

Adult↗
PubMed1987

Transesophageal Doppler scanning versus thermodilution during general anesthesia. An initial comparison of cardiac output techniques.

Measurement of cardiac output has become an essential feature of anesthetic management of patients with cardiac disease requiring operation. Thermodilution by way of a Swan-Ganz catheter is the current popular technique for cardiac output determination. Unfortunately, this method is costly and has an associated irreducible morbidity rate and has, in rare instances, resulted in death. The suprasternal ultrasonographic Doppler technique has shown promise for measuring cardiac output noninvasively; however, it is too cumbersome for continuous intraoperative use. In an effort to overcome this limitation, the esophageal stethoscope was modified to accept a Doppler probe. Herein, we have reported an initial comparison of transesophageal Doppler scanning and thermodilution in 23 adult men during general anesthesia. The average difference between thermodilution and descending cardiac output was 0.16 +/- 0.81 liters/min. The correlation between thermodilution and descending cardiac output increased with operator experience. In the last 13 patients, there was an average correlation of 0.85. After the equipment was mastered and improvements in design were made, descending cardiac output had a high correlation with thermodilution and appeared to track the dynamic changes during general anesthesia.

Aged↗
PubMed1990

[Cardiac output control of total artificial heart during exercise--a predictive control method based on objective functions obtained from changes in cardiac output of the natural heart with respect to time].

In order to establish a total artificial heart (TAH) control method during exercise, a predictive control method was developed to increase the cardiac output (CO) during exercise in a profile similar to that of a natural heart; this was achieved by predicting changes in CO as a time function at various treadmill speeds. During exercise, the CO of the TAH was controlled to follow the time function by changing operating parameters such as the positive and negative pressures, S/D ratio, and pulse rate of both artificial heart pumps under a computerized control algorithm. To evaluate this control method, four TAH goats were exercised on a treadmill. The hemodynamics were recorded before, during, and after exercise; the blood lactate, blood catecholamine, A-V oxygen difference, and blood hemoglobin were measured before and immediately after exercise. The predictive control method was then compared with both the natural heart and also the fixed control method, in which the operating parameters remained unchanged during exercise. It was concluded that 1) with the predictive control method, changes in the CO of the TAH were almost the same as in the natural heart. On the other hand, no increase in CO occurred with the fixed control method. 2) with the predictive control method, changes in the blood lactate, blood catecholamine and A-V oxygen difference were significantly lower than with the fixed control method. This study showed that the TAH goat with the predictive control method resulted in being subjected to less stress than with the fixed control method, and that this method can be usefully employed until such time as an ideal feedback control method for the TAH can be developed.

Algorithms↗
PubMed1997

Non-invasive measurement of cardiac output and ventricular ejection fractions in chronic cardiac failure: relationship to impaired exercise tolerance.

1. The role of cardiac output limitation in the pathophysiology of exercise in patients with chronic failure remains undefined. During steady-state submaximal exercise, oxygen uptake is similar in patients and control subjects, but it is not known if cardiac output is also similar. We wished to determine if the reduced exercise tolerance of patients with chronic cardiac failure during such exercise is related to reduced cardiac output, or to peripheral factors. 2. Ten male patients with stable chronic failure and ten age-matched male normal controls were studied at rest and during exercise. Each subject performed a familiarization exercise test, a symptom-limited maximal exercise test and two submaximal exercise tests. Cardiac output was measured by a carbon dioxide rebreathing method. We also measured oxygen consumption, ventilation, Borg score of perceived exertion and venous lactate concentration, and ejection fractions. 3. As expected, patients had lower peak oxygen consumption [median (range) 1.18 (0.98-1.76) versus 1.935 (1.53-2.31) l/min; P < 0.001], lower peak venous lactate concentration but a similar overall level of perceived exertion. At the same submaximal workload, patients and control subjects had similar oxygen consumption [0.67 (0.59-0.80) versus 0.62 (0.52-0.82) l/min] and cardiac output [6.92 (5.79-9.76) versus 7.3 (5.99-10.38) l/min] but the patients had a greater perceived level of exertion [Borg score: 4 (1-6) versus 3 (1-5); P < 0.005], higher venous lactate concentration [1.6 (1-3.3) versus 1.14 (0.7-1.7) mmol/l; P < 0.05] and higher heart rate [106 (89-135) versus 87 (69-112) beats/ min; P < 0.005]. 4. During submaximal exercise at a similar absolute workload, patients with cardiac failure have a similar oxygen uptake and cardiac output but greater anaerobiosis and increased fatigue when compared with normal subjects. These findings appear to relate predominantly to changes that occur in the periphery rather than abnormalities of central cardiac function.

Adult↗
PubMed1976

Control of cardiac output in essential hypertension.

Cardiac and renal hemodynamics and cardiopulmonary and total blood volume were determined in 202 men, 101 with normotension and 101 of the same age with chronic essential hypertension, normal renal function and balanced sodium intake and urinary output. Cardiac output was identical in the two groups, whereas blood pressure and total peripheral resistance were significantly different. The two groups exhibited strong differences in the correlation study: (1) Correlations of blood pressure with, respectively, heart rate, cardiopulmonary blood volume and total blood volume were significant in the normotensive group but not in the hypertensive group. (2) Correlations of cardiac output with, respectively, heart rate, cardiopulmonary blood volume and total blood volume were significant in both groups. (3) Correlations of renal blood flow with, respectively, cardiac output, blood pressure and total blood volume were significant in the hypertensive group but not in the normotensive group. This study provides evidence that: (1) the volume and neural control of blood pressure are disrupted in hypertension whereas control of cardiac output is maintained; and (2) adaptive mechanisms involving renal function are necessary to the maintenance of normal cardiac output in patients with essential hypertension.

Adult↗
PubMed1985

Two-dimensional echocardiographic method for the estimation of cardiac output independent of left ventricular geometry. Comparison with cardiac catheterization in mitral stenosis.

An hydraulic formula for the estimation of cardiac output independent of the geometric status of the left ventricle was studied by comparing the predictions based upon echographic and catheterization data with the results of the standard Fick principle method for cardiac output. The formula tested specifies cardiac output as Q = (1/21) RAT2, where Q is the cardiac output in ml, R is the heart rate, A is the mitral valve area in cm2 and T is the diastolic filling period in seconds per minute. Cardiac output estimated by this equation corresponds with cardiac output as determined by the Fick principle method at a level characterized by a correlation coefficient of r = 0.92 and a standard error of SE = 0.15 L/min for N = 26. The results suggest that the new expression may be useful for estimating cardiac output from echographic data.

Cardiac Catheterization↗
PubMed1979

Experimental evaluation of 2F transthoracic thermodilution cardiac outputs in small animals.

Cardiac output can be measured with a computer using a 2F transthoracic catheter placed during surgery. When injections are made into a central venous catheter, this technique allows for cardiac output measurements to be made in children with complex congenital heart disease not appropriate for placement of a transvenous pulmonary artery catheter. Using rabbits similar in size to the infants most likely to need this technique, 26 experimental comparisons of thermodilution and indocyanine green dye cardiac outputs were made with cardiac outputs as low as 0.2-0.4 liter/min. The relationship between green dye and thermodilution was statistically significant (p less than 0.001) and almost linear (r = 0.92). This documents the validity of both the 2F transthoracic catheter technique in the low range of cardiac outputs appropriate for infants and children.

Animals↗
PubMed1999

Neuronally induced augmentation of cardiac output.

OBJECTIVE: To determine whether cardiac output can be augmented by preferentially activating cardiac adrenergic efferent neurons. DESIGN: Elicited cardiac output responses were compared when cardiac myocytes were directly stimulated by a beta1-adrenoceptor agonist versus when they were indirectly influenced by beta2- adrenergic-sensitive cardiac efferent neurons. ANIMALS AND METHODS: The beta1-adrenoceptor agonist dobutamine or the selective beta2-adrenoceptor agonist terbutaline was continuously infused individually into the systemic circulation of 15 anesthetized pigs for 20 mins in 5 and 15 microgram/kg/min doses. Heart rate, left atrial chamber pressure, regional left ventricular intramyocardial systolic pressure, left ventricular chamber pressure and aortic pressure were monitored. Cardiac output was determined via the thermodilution technique before and at 10 min intervals during drug infusions. Ventricular tissues were removed thereafter and immediately frozen in liquid nitrogen for subsequent cardiac myocyte cell surface beta-adrenoceptor analysis. MAIN RESULTS: Both doses of terbutaline increased heart rate (approximately +18%) and cardiac output (approximately +20%). Heart rate (+12%) and cardiac output (+16%) increased when the high dose of dobutamine was tested. Left ventricular intramyocardial systolic pressure was increased by dobutamine (+15%) but not by terbutaline. Porcine ventricular cardiac myocytes primarily possess cell surface beta1-, rather than beta2-, adrenoceptors, making it unlikely that cardiac myocytes were directly affected by the doses of terbutaline tested. CONCLUSIONS: Beta2-adrenoceptor agonists enhance cardiac output primarily as a result of neuronally induced increases in heart rate in the porcine model. Adrenergic efferent neuronal enhancement of heart rate may be an effective way to increase cardiac output independently of directly augmented ventricular dynamics. Further study is required to determine whether the diseased myocardium can be supported by such neurocardiological means.

Adrenergic beta-Agonists↗
PubMed1990

[Cardiac output monitoring by impedance cardiography in cardiac surgery].

The cardiac output monitoring by impedance cardiography, NCCOM3, was evaluated in adult patients (n = 12) who were subjected to coronary artery bypass grafting. Values of cardiac output measured by impedance cardiography were compared to those by the thermodilution method. Changes of base impedance level used as an index of thoracic fluid volume were also investigated before and after cardiopulmonary bypass (CPB). Correlation coefficient (r) of the values obtained by thermodilution with impedance cardiography was 0.79 and the mean difference was 1.29 +/- 16.9 (SD)% during induction of anesthesia. During the operation, r was 0.83 and the mean difference was -14.6 +/- 18.7%. The measurement by impedance cardiography could be carried out through the operation except when electro-cautery was used. Base impedance level before CPB was significantly lower as compared with that after CPB. There was a negative correlation between the base impedance level and central venous pressure (CVP). No patients showed any signs suggesting lung edema and all the values of CVP, pulmonary artery pressure and blood gas analysis were within normal ranges. From the result of this study, it was concluded that cardiac output monitoring by impedance cardiography was useful in cardiac surgery, but further detailed examinations will be necessary on the relationship between the numerical values of base impedance and the clinical state of the patients.

Aged↗
PubMed1975

Seasonal variations of cardiac output in rats.

Cardiac output of rats shows seasonal variations with low values in spring and summer and high ones in autumn and winter. The stroke volume was much more implicated in these changes than the heart rate. The seasonal changes of cardiac output are probably due to changes of thyroid function.

Animals↗