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PubMed1999

Cardiac output is a determinant of the initial concentrations of propofol after short-infusion administration.

UNLABELLED: Indicator dilution theory predicts that the first-pass pulmonary and systemic arterial concentrations of a drug will be inversely related to the cardiac output. For high-clearance drugs, these first-pass concentrations may contribute significantly to the measured arterial concentrations, which would therefore also be inversely related to cardiac output. We examined the cardiac output dependence of the initial kinetics of propofol in two separate studies using chronically instrumented sheep in which propofol (100 mg) was infused IV over 2 min. In the first study, steady-state periods of low, medium, and high cardiac output were achieved by altering carbon dioxide tension in six halothane-anesthetized sheep. The initial area under the curve and peak value of the pulmonary artery propofol concentrations were inversely related to cardiac output (R2 = 0.57 and 0.66, respectively). For the systemic arterial concentrations, these R2 values were 0.68 and 0.71, respectively. In our second study, transient reductions in cardiac output were achieved in five conscious sheep by administering a short infusion of metaraminol concurrently with propofol. Cardiac output was lowered by 2.2 L/min, and the area under the curve to 10 min of the arterial concentrations increased to 143% of control. IMPLICATIONS: The initial arterial concentrations of propofol after IV administration were shown to be inversely related to cardiac output. This implies that cardiac output may be a determinant of the induction of anesthesia with propofol.

Adrenergic alpha-Agonists↗

PubMed1999

Partial CO2 rebreathing cardiac output--operating principles of the NICO system.

The partial rebreathing method of cardiac output estimation is reviewed with a particular focus on its application for continuous monitoring, rebreathing and implementations and from both a historical and technical perspective. The assumptions of the method are discussed as well as the various implementations. The NICO monitor and rebreathing valve are described from a functional view. The clinical data including (a) comparisons between bolus thermodilution and continuous thermodilution in patients in the OR setting, (b) comparisons to continuous thermodilution with both the Baxter and Abbott continuous cardiac output devices and (c) comparison between different means of shunt correction are presented. Compared to conventional cardiac output methods, the partial CO2 rebreathing technique is non-invasive, can easily be automated and can provide real-time and continuous cardiac output monitoring. Taking advantage of modern sophisticated sensor and signal processing technology and integrating multiple monitored physiological variables the NICO monitor is the first commercially available cardiac output system making use of the partial rebreathing of CO2.

Carbon Dioxide↗

PubMed1970

Effects of training on the distribution of cardiac output in patients with coronary artery disease.

In nine patients with coronary artery disease, cardiac output distribution was evaluated at rest and during exercise by measurement of cardiac output and regional blood flow parameters (hepatic and muscle blood flow). In seven patients repeated values were obtained after a physical training program of 4 to 10 weeks' duration. After training, cardiac output was reduced at moderate work loads (13.1%) causing a change of the relation between oxygen uptake and cardiac output from hyperkinetic to normal. During heavy exercise the cardiac output was increased (5.5%) after training. Similar changes were observed in muscle blood flow, which was reduced at submaximal loads (14.9%) and increased at maximal (8.6%). Hepatic blood flow showed in contrast a less pronounced reduction at both work loads after training (difference, 7.2%). These effects of training could be explained as peripheral regulatory alterations without implying primary improvement in myocardial performance. They are consistent with the view that local changes in the trained muscles are important for the reduction in myocardial pressure-work caused by physical conditioning.

Cardiac Output↗

PubMed1973

Mechanisms regulating the cardiac output response to cyanide infusion, a model of hypoxia.

When tissue metabolic changes like those of hypoxia were induced by intra-aortic infusion of cyanide in dogs, cardiac output began to increase after 3 to 5 min, reached a peak (220% of the control value) at 15 min, and returned to control in 40 min. This pattern of cardiac output rise was not altered by vagotomy with or without atropine pretreatment. However, this cardiac output response could be differentiated into three phases by pretreating the animals with agents that block specific activities of the sympatho-adrenal system. First, ganglionic blockade produced by mecamylamine or sympathetic nerve blockade by bretylium abolished the middle phase of the cardiac output seen in the untreated animal, but early and late phases still could be discerned. Second, beta-adrenergic receptor blockade produced by propranolol shortened the total duration of the cardiac output rise by abolishing the late phase. Third, when given together, propranolol and mecamylamine (or bretylium) prevented most of the cardiac output rise that follows the early phase. When cyanide was given to splenectomized dogs, the duration of the cardiac output response was not shortened, but the response became biphasic, resembling that seen after chemical sympathectomy. A similar biphasic response of the cardiac output also resulted from splenic denervation; sham operation or nephrectomy had no effect on the monophasic pattern of the normal response. Splenic venous blood obtained from cyanide-treated dogs, when infused intraportally, caused an increase in cardiac output in recipient dogs; similar infusion of arterial blood had no effects. THESE RESULTS SUGGEST THAT THE CARDIAC OUTPUT RESPONSE TO CYANIDE INFUSION CONSISTS OF THREE COMPONENTS: an early phase, related neither to the autonomic nervous system nor to circulating catecholamines; a middle phase, caused by a nonadrenergic humoral substance released from the spleen by sympathetic stimulation; and a late phase, dependent upon adrenergic receptors but not upon sympathetic transmission.

Animals↗

PubMed1997

ECT in patients with major depressive disorder and low cardiac output.

Electroconvulsive therapy (ECT) in patients with impaired cardiac output may be associated with significant cardiovascular morbidity and mortality because of its hemodynamic effects. Many clinicians are reluctant to treat these patients with ECT because of the high risk associated with the treatment. In this report, we present a clinically appropriate protocol for ECT treatment of patients with impaired cardiac output and major depressive disorder. Three patients, ages 59-78 years, with resistant major depression and impaired cardiac output (ejection fraction 20-25%), were successfully treated with ECT according to this protocol.

Aged↗

PubMed1990

[Arrhythmia in patients with low cardiac output after valvular surgery. Randomized, double-blind comparative study of dobutamine versus enoximone].

Forty patients with low cardiac output (cardiac index less than 2.2 l/mn/m2 and pulmonary wedge pressure greater than 15 mmHg) after valvular surgery were randomised into two groups. Patients in Group 1 were given 5 to 10 micrograms/Kg/mn of Dobutamine (D) and those In Group 2 a bolus of Enoximone (E) 1 mg/kg followed by an intravenous infusion of 5 to 10 micrograms/Kg/mn. Holter ECG monitoring over 42.65 +/- 6.02 hrs (24-48 hours) was obtained and interpreted blindly in 37/40 patients (19 Group D and 18 Group E). The results were analysed by the t and X2 tests. A p value of less than .05 was considered statistically significant. The two groups were comparable. No deaths occurred during the protocol period. The total duration of inotropic therapy (86 +/- 49 hours) and the period spent in the intensive care unit (155 +/- 129 hours) were longer in Group D than in Group E (60 +/- 23 hrs and 92 +/- 37 hrs, respectively; p less than .05). Antiarrhythmic therapy was used more often in Group D (4 patients) than in group E (1 patient) (p = 0.09).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1975

Evaluation of impedance cardiography as a non-invasive means of measuring systolic time intervals and cardiac output.

Impedance cardiography was used for non-invasive determinations of systolic time intervals (STI) and cardiac output. The results were compared with simultaneously obtained invasive measurements of STI from central aortic pressure curves and of cardiac output using the dye-dilution technique. The study was performed on eight dogs during increasing halothane concentration. A close correlation was found between non-invasively and invasively measured left ventricular ejection time = LVET (r = 0.986) and pre-ejection period - PEP (r - 0.948). Measurements of cardiac output derived from changes in thoracic impedance were determined 1) using a fixed value of p (p - the resistivity of blood) and 2) using an individual value of p based on the actual hematocrits. When compared to cardiac outputs obtained by dye-dilution the correlation coefficients were r = 0.806 and r = 0.816, respectively. Impedance cardiography is a useful method of evaluating changes in cardiac output. The method permits simultaneous observations of changes in STI and cardiac output as an index of cardiac function.

Animals↗

PubMed1991

Measurement of cardiac output--transtracheal Doppler versus thermodilution.

The ABCOM 1 transtracheal Doppler (TTD) has been developed as a non-invasive cardiac output monitor. With this device, cardiac output is continuously calculated from ascending aortic blood flow velocity and aortic diameter obtained via an ultrasound transducer incorporated into the tip of an endotracheal tube. We evaluated the clinical use of the ABCOM 1 monitor and compared cardiac outputs obtained using the TTD system with simultaneous thermodilution (TD) measurements. We found the operation of the ABCOM 1 monitor to be difficult and time-consuming. In our operating rooms, acceptable Doppler signal quality was difficult to obtain. There was no correlation between 36 simultaneously obtained TTD and TD cardiac output measurements. The average difference between measurement techniques and the limits of agreement were unacceptably large (mean difference = 3.04 L.min-1, mean +/- 2 SD = -6.04 to 12.48 L.min-1). Separately analyzing only those measurements during which Doppler signal quality was adequate did not improve agreement between TTD and TD measurements. On the basis of these findings, TTD cannot be recommended as a clinical cardiac output measurement technique.

Cardiac Output↗

PubMed1985

Doppler-echocardiographic assessment of cardiac output.

Noninvasive Doppler-echocardiographic estimates of cardiac output correlate well with invasive measures of cardiac output, making Doppler echocardiography useful in clinical practice. The ability of Doppler echocardiography to measure flow at multiple sites within the heart makes calculation of intracardiac shunt flow ratios and regurgitant flow volume possible. Measurement of flows at stenotic and nonstenotic sites provides the potential for determining the area of a stenotic valve without cardiac catheterization. Although considerable work must be done before all of these methods can be applied routinely, Doppler echocardiography is clearly emerging as a powerful quantitative tool that greatly enhances the strength of noninvasive evaluation in cardiac diagnosis and management.

Blood Flow Velocity↗

PubMed1992

Doppler echocardiographic measurement of cardiac output in man using mitral annulus method.

The mitral inflow method of measuring cardiac output with pulsed Doppler two-dimensional echocardiography was developed and validated against the thermodilution technique in 42 patients. A mitral inflow method combined the velocity of left ventricular inflow at the mitral annulus (apical long-axis view) with the cross-sectional area of the annulus calculated from its diameter (parasternal long-axis view). A good correlation was observed between thermodilution and Doppler measurements of cardiac output (r = 0.93). The ratio of Doppler measurements to thermodilution measurements will be between 0.76 and 1.15 for about 95% of cases. There was a good correlation between percentage change in thermal cardiac output and those in Doppler cardiac output (r = 0.95); the limits of agreement were -11.5% to 10.5%, suggesting that this method can be most useful for assessing relative changes in cardiac output.

Blood Flow Velocity↗

PubMed1992

High cardiac output of advanced liver disease persists after orthotopic liver transplantation.

This study measured cardiac output before and 1 or 2 yr after orthotopic liver transplantation in 23 patients. Cardiac output was measured by thermodilution before transplantation and by first-pass radionuclide angiocardiography at follow-up. Study patients were selected as those doing well clinically and by standard laboratory tests at 1-yr and 2-yr reevaluations with no evidence of rejection: six had mild recurrent hepatitis shown on biopsy samples. Hepatocyte function was normal at the time of the study as shown by galactose elimination capacity of 442 +/- 90 mg/min. Medications were cyclosporine and prednisone in all patients, azathioprine in 10 patients and a combination of antihypertensive therapy to maintain diastolic blood pressure less than 90 mm Hg in 20 patients. Mean (+/- S.D.) pretransplantation cardiac output was 9.1 +/- 3.1 L/min and remained elevated at 8.3 +/- 2.1 L/min 1 yr, and 9.6 +/- 2.6 L/min (n = 13) 2 yr after transplantation. A significant (p less than 0.001) correlation was found between pretransplant and follow-up cardiac output. End diastolic, end systolic and stroke volumes are all increased in a pattern similar to that seen in end-stage cirrhosis. These data show that the high cardiac output of the hyperdynamic state of advanced liver disease persists after liver transplantation. The mechanisms and consequences of this require further study.

Cardiac Output↗

PubMed1997

Postcardiac surgery low cardiac output syndrome: dopexamine or dopamine?

OBJECTIVE: To compare the efficacy and safety of dopexamine with dopamine in the treatment of low cardiac output syndrome after cardiac surgery. DESIGN: This was a multicentre, double-blind, randomised, parallel-group study conducted in intensive care units at centres in Holland and Belgium. Patients were randomised to receive dopexamine (up to 2.0 micrograms/ kg per min) or dopamine (up to 6.0 micrograms/kg per min) for 6 h after low cardiac output syndrome was confirmed. RESULTS: 70 patients were enrolled (35/group) and there was no significant differences in the operative procedures or haemodynamics at entry into the study. Clinical efficacy, defined as a cardiac index > 2.5 l/min per m2 with urine production > 0.5 ml/kg per h and stable haemodynamics for two consecutive readings 1 h apart, was achieved by 90 and 87% of patients in the dopexamine and dopamine groups, respectively. However, more patients maintained clinical efficacy over the 6-h period in the dopexamine group, which was statistically significant at 1-2 h and approached significance at all other time points. Safety was assessed by comparing the adverse events and concomitant medication. Fewer patients on dopexamine had cardiac events compared with dopamine-treated patients (25 vs 38 events), although there was no difference in the pattern of rhythm disturbance. Fewer patients in the dopexamine group required concomitant vasodilating drugs (18 vs 30). CONCLUSION: Taking the proportion of patients achieving clinical efficacy, the time to achieve it and the maintenance of it along with the adverse event profile, dopexamine was shown to be an effective and safe drug to use in the management of low cardiac output syndrome after coronary artery bypass graft surgery and may be superior to dopamine.

Adrenergic beta-Agonists↗

PubMed2004

Effect of xenon anaesthesia on accuracy of cardiac output measurement using partial CO2 rebreathing.

Cardiac output (CO) determination based on partial CO(2) rebreathing has recently been introduced into clinical practice. The determination of flow is crucial for exact CO readings and the physical properties of xenon, i.e. high density and viscosity, may influence flow readings. This study compared echocardiography-derived CO measurements with the partial rebreathing method during total intravenous (TIVA) vs. xenon-based anaesthesia. Thirty-nine patients ASA physical status III undergoing aortic reconstruction were randomly assigned to receive either xenon (Xe, n = 20) or TIVA (T, n = 19) based general anaesthetic. Paired measurements were taken before xenon administration, after xenon administration, before and after clamping of the abdominal aorta and after declamping and at corresponding time points in the TIVA group. Data were analysed with a Bland-Altmann plot. Bias and precision were acceptable and comparable before xenon administration (T 0.54 +/- 0.92 l.min(-1) vs. Xe 0.11 +/- 1.1 l.min(-1)), but after xenon administration CO was largely overestimated by partial CO(2) rebreathing (T 0.04 +/- 0.91 l.min(-1) vs. Xe -4.0 +/- 2.1 l.min(-1)). In the TIVA group, bias and precision after declamping increased significantly (P < 0.01) compared to all time points except baseline. In its current application, the NICO cardiac output monitor appears to be inappropriate for determination of CO during xenon based anaesthesia.

Aged↗

PubMed1992

Evaluation of cardiac output by thoracic electrical bioimpedance during exercise in normal subjects.

We compared cardiac output determined simultaneously by two methods, the CO2 rebreathing technique and the thoracic electrical bioimpedance method (Bomed NCCOM-3 equipment). The studies were performed in duplicate in 11 healthy male subjects at rest and during three levels of steady-state exercise on a cycle ergometer at 60, 120, and 180 W. Cardiac output at 60 and 120 W was slightly lower (p less than 0.01) by the thoracic impedance method (12.2 +/- SE 2.2 and 15.7 +/- SE 3.5 L/min, respectively) than by the CO2 rebreathing method (14.0 +/- SE 2.1 and 17.9 +/- SE 3.0 L/min, respectively), suggesting a systematic bias between the two methods of measurement. However, if allowance is made for that bias, there would be acceptable agreement between the two methods at 60 and 120 W. Although the results were not significantly different between the two methods at rest and at 180 W, there was no acceptable agreement between the two methods probably because the CO2 rebreathing method at rest was more liable to show error due to the small arteriovenous CO2 difference, while the impedance method was less reliable at 180 W. Cardiac output by both methods correlated with O2 consumption, with the correlation being higher for cardiac output by the rebreathing method (r = 0.94) than for thoracic impedance (r = 0.88). The results suggest that the thoracic electrical bioimpedance method can be used for determination of cardiac output during mild or moderate levels of exercise in normal subjects.

Adult↗

PubMed1985

The reproducibility of nongeometric analysis of cardiac output and left ventricular volume by radionuclide angiography.

This study examines the reproducibility of individual radionuclide attenuation factors used in the calculation of cardiac output and left ventricular volume by the nongeometric radionuclide method. Twenty male patients were studied at rest with thermodilution measurements of cardiac output on two separate days. Simultaneous equilibrium radionuclide angiograms were performed and left ventricular stroke volume and cardiac output were determined by the nongeometric method. Individual patient attenuation factors were calculated as the ratio of thermodilution and radionuclide cardiac output measurements at each study. There was a close linear relationship between radionuclide and thermodilution measurements of cardiac output in each study (r = 0.88 study 1, r = 0.97 study 2). A similar relationship was found for measurements of left ventricular stroke volume (r = 0.86, study 1, r = 0.97 study 2). Individual radionuclide attenuation factors ranged from 2.49 to 3.46 in study 1 and from 2.77 to 3.29 in study 2. The individual attenuation factors were reproducible to within 10% in 13 patients and to within 15% in 19 patients. When cardiac output was calculated from the radionuclide data of study 2, by means of individual attenuation factors previously determined in study 1, there was a good correlation with the simultaneous thermodilution measurements of cardiac output (r = 0.92, SEE = 0.38 L/min). Individual radionuclide attenuation factors show little variation in serial studies. Thus the nongeometric radionuclide technique can be used to make accurate serial measurements of cardiac output and left ventricular volume.

Adult↗

PubMed1980

Determination of cardiac output based on breath-holding.

A breath-holding method for determination of cardiac output is described. It is based on the indirect Fick principle applied to carbon dioxide. Mixed venous PCO2 (PvCO2) is measured noninvasively using a CO2 breath-holding technique and PaCO2 is obtained by arterial puncture. Partial pressures are converted into contents using each patient's CO2 dissociation curve, taking into account temperature, hemoglobin, arterial and venous pH. The authors have applied this method to the determination of cardiac output in 20 patients, in whom cardiac output was also measured invasively using either direct Fick or thermodilution method. Mean cardiac output determined using the breath-holding method was 5.48 +/- 2.95 (SD) L/min, compared to 5.54 +/- 2.88 L/min as determined by the direct Fick or thermodilution method. Good correlation was found between the invasive and breath-holding method (r = 0.97, p < 0.001). The authors conclude that cardiac output at rest may be estimated with considerable accuracy from the measurements of PaCO2, CO2 production and the breath-holding mixed venous PCO2 without right-sided cardiac catheterization.

Arteries↗

PubMed1989

Noninvasive assessment of cardiac output by impedance cardiography in the newborn canine.

Currently, critical care monitoring of cardiac function in the newborn human consists mainly of measuring heart rate and BP. A noninvasive technique for assessing cardiac output routinely in the critically ill neonate would facilitate clinical management. Impedance cardiography (IC) is a noninvasive technique which measures stroke volume on a beat-by-beat basis. This study compared cardiac output as measured by thermodilution (TD) to that measured by IC in seven canine pups 6 to 7 days old weighing 0.66 to 0.86 kg. Cardiac output was altered by the withdrawal and reinfusion of blood. There were no significant differences between the two methods for either the absolute value of cardiac output (r = .96) or the percent change in cardiac output (r = .97). Coefficients of variation were 3.0% for TD and 3.6% for IC. These results indicate that IC can be used to assess serially cardiac function in the newborn.

Animals↗

PubMed1994

Banding a hemodialysis arteriovenous fistula to decrease blood flow and resolve high output cardiac failure: report of a case.

We report herein the successful surgical treatment of a patient with high-output cardiac failure which developed from a high-flow hemodialysis arteriovenous fistula of the Brescia-Cimino type. Banding correction of the venous limb of the fistula with a woven Dacron prosthesis resulted in marked improvement of the cardiac failure. An ultrasonic study showed the fistula flow of 3.2 l/min to be as high as 40% of the resting cardiac output, or 8.0 l/min, before banding, while an intraoperative electromagnetic study was useful for controlling the degree of banding and showing the decrease of fistula flow from 3.7 l/min to 1.4 l/min.

Aortic Aneurysm, Abdominal↗