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PubMed1992

ATP-MgCl2 restores the depressed cardiac output following trauma and severe hemorrhage even in the absence of blood resuscitation.

A number of beneficial effects of ATP-MgCl2 administration have been demonstrated in preheparinized models of shock and ischemia. However, it is not known whether ATP-MgCl2 restores and maintains the depressed cardiac output in a nonheparinized model of trauma and severe hemorrhage in which resuscitation following shock was provided only with crystalloid. To study this, rats underwent a midline laparotomy (i.e., trauma induced) and were then bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximum shed blood volume was returned in the form of Ringer's lactate (RL). Animals were then resuscitated with 4 times the volume of shed blood with RL (4 X RL) during and following which ATP-MgCl2 (50 mumol/kg body weight each or an equivalent volume of normal saline) was infused intravenously. Cardiac output was determined every 15-30 min for 4.5 hr, using an in vivo hemoreflectometer and indocyanine green dilution technique. Resuscitation with 4 X RL transiently restored but did not maintain cardiac output; however, ATP-MgCl2 treatment restored and maintained cardiac output at control values. ATP-MgCl2 infusion also significantly decreased total peripheral resistance and attenuated tissue water content. Thus, ATP-MgCl2 appears to be a promising adjunct to the treatment of trauma-hemorrhage even in the absence of blood resuscitation.

Adenosine Triphosphate↗

PubMed1995

Cardiac output in single-lead VDD pacing versus rate-matched VVIR pacing.

The importance of atrioventricular synchronous pacing compared with single-chamber rate-responsive pacing is still under discussion, especially for low-intensity workload representing daily life activities. We evaluated hemodynamics in single-lead VDD pacing versus VVIR pacing in 11 patients (8 men and 3 women, aged 58.6 +/- 13.8 years) with normal left ventricular function and a previously implanted single-lead VDDR pacemaker. A low-intensity steady-state treadmill test at 1 to 2.5 mph with a gradient of 2% to 4% was performed. Cardiac output was determined using a standard carbon dioxide rebreathing technique. Initially, the VDD mode was programmed, and after 5 minutes of exercise, cardiac output was measured in steady-state conditions. The pacemaker was then reprogrammed to the VVI mode at a rate 5 to 10 beats above the maximal atrial tracking rate to simulate rate-matched VVIR pacing (VVIRm). After 5 additional minutes of steady-state exercise, cardiac output was measured again. The maximal atrial rate in the VDD mode was 119 +/- 19 beats/min versus a programmed rate of 129 +/- 18 beats/min in the VVIRm mode. VDD pacing resulted in a significantly higher cardiac output than VVIRm pacing (10.6 +/- 1.9 vs 9.2 +/- 1.4 L/min; p < 0.002), with a mean difference of 1.6 +/- 1.2 L/min between the 2 modes. In the VDD mode, stroke volume (90.7 +/- 20.1 vs 71.6 +/- 13.0 ml; p < 0.001) and maximal oxygen uptake (1,183 +/- 264 vs 1,076 +/- 289 ml/min, p < 0.01) were also higher than in VVIRm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1979

Cardiac output and contractility indices: establishing a standard in response to low-to-moderate level exercise in healthy men.

Measurement by impedance cardiography (ZCG) of cardiac output and contractility indices during exercise is a recent addition to exercise testing of the cardiac patient. To provide a needed standard of normal responses to exercise at integrals of resting oxygen consumption (METS), 10 healthy men were tested. Basal oxygen consumption (1MET) under standardized conditions was measured by mass spectrometry. Over several days the subjects were exercised on a treadmill at 2METS through 6METS with monitoring of heart rate, electrocardiogram, oxygen consumption per minute (VO2) and ZCG. The exercise routine was then repeated to look for test-retest effect. Values closely approximating presently accepted basal oxygen consumptions were achieved under these standardized but practical conditions. Cardiac output during sitting, fully supported rest was slightly higher than that at 2METS on treadmill owing to higher stroke volume. From 2METS through 6METS the curvilinear mean heart rate and stroke volume were mirror images, producing a linear increase in mean cardiac output which at 6METS was 145% of basal and 160% of the 2MET value, while the contractility index increased to 217% of basal. Comparison of the 2 trials revealed no significant test-retest effect.

Adult↗

PubMed1991

Pharmacologic support for postoperative low cardiac output.

This review has outlined a rational approach to the understanding and pharmacologic treatment of low output states after cardiac surgery. There are clearly other reasonable schemes for the use of these agents for management of these difficult patients. However, the principles of management remain the same. Data about the specific effects of these drugs must be applied to specific patients whose particular hemodynamic derangements have been analyzed carefully. However, the complex and changing interactions between the heart and the peripheral vascular system and the effects of these agents on both signify that these analyses must be made continuously during the early hours after cardiac surgery. Rational use of these agents requires careful analysis of the specific hemodynamic disorder in a given patient. Pharmacologic inotropic therapy should then be tailored to these abnormalities and based on what is known about the expected effects of these drugs on the heart and peripheral circulation. Careful and repeated follow-up measurements to document both the effects of the drugs and potential changes in the patient's hemodynamic state are required if successful therapy is to be achieved. A rational approach to the selection of the inotropic agents requires not only an understanding of the effects of the drugs, but continuous monitoring of the patient's hemodynamic state and recognition that the patient's condition and needs may change and dictate alteration in subsequent therapy.

Cardiac Output, Low↗

PubMed1979

Redistribution of cardiac output and oxygen delivery in the hypoxemic fetal lamb.

In hypoxia, fetal cardiac output and the product arterial O2 content x blood flow to the fetal heart and central nervous system (CNS) tend to remain constant. As a consequence the percentage of cardiac output directed to the heart and CNS increases hyperbolically in inverse relation to the oxygen content of the fetal ascending aorta, [O2]as. The fetal lamb maintains [O2]as approximately 0.45 mM (0.45 +/- 0.02 SEM) higher than the O2 content in the abdominal aorta, [O2]ab, over a wide range of oxygenation. When [O2]as decreases below the 2 mM level, the [O2]as--[O2]ab difference (delta O2) decreases also. A mathematical model of the fetal circulation shows that delta O2 is a function of the ratio oxygen consumption of fetal upper body/abdominal aorta blood flow (VU/FA). The behavior of delta O2 in hypoxia can be explained by assuming that the VU/FA ratio is maintained in moderate hypoxia and decreases in sever hypoxia.

Animals↗

PubMed1987

A modified single breath method for estimation of cardiac output in humans at rest and during exercise.

This study was undertaken to determine the accuracy of a modification of a single breath method for estimation of cardiac output. The technique incorporated a single rebreathing stage followed by a prolonged expiration. Cardiac output was determined from the O2 uptake and the instantaneous changes in O2 and CO2 in the expired gas during the prolonged expiration. The mean values and the random errors (determined from the differences between pairs of estimates) of cardiac outputs in normal subjects at rest and exercise were 5.42 and +/- 0.60 litres/min (2 SD, 60 pairs) and 14.1 and +/- 1.8 litres/min (40 pairs). Larger random errors were obtained in a group of cardiac patients but, except in hypoxic patients, the mean values obtained by the single breath and the direct (Fick) methods were almost identical. We conclude that our modification of the single breath method is simple to use and sufficiently reliable for use in humans both at rest and during steady states of light exercise.

Adult↗

PubMed2005

Evaluation of cardiac output from a tidally ventilated homogeneous lung model.

We used the direct Fick measurements to validate a method for estimating cardiac output by iteratively fitting VCO(2) at the mouth to lung model values. This model was run using a series of 50, 30 and 10 breaths to test sensitivity to number of breaths used for fitting. The lung was treated as a catenary two-compartment lung model consisting of a dead space compartment connected with a single alveolar space compartment, perfused with constant pulmonary blood flow. The implemented mathematical modeling described variations in O(2) and CO(2) compartmental fractions and alveolar volume. This model also included pulmonary capillary gas exchange. Experimental data were collected from measurements performed on six healthy subjects at rest and during 20, 40, 60 and 85-90% of peak V(O)(2). The correlation between the two methods was highest and the average agreement between the methods was best using 50 breaths R = 095; P < 0.0001; Q(model) = 1.1Q(Fick) - 2.3). The mean difference and lower to upper limits of agreement between measured and estimated data were 0.7 l/min (-2.7 to 4.1 l/min) for cardiac output; -0.9 ml/100 ml (-1.3 to -0.5 ml/100 ml) for arterial O(2) content; -0.8 ml/100 ml (-3.8 to 2.2 ml/100 ml) for mixed venous O(2) content and -0.1 ml/100 ml (-2.9 to 2.7 ml/100 ml) for arteriovenous difference O(2) content. The cardiac output estimated by the lung model was in good agreement with the direct Fick measurements in young healthy subjects.

Adult↗

PubMed1979

Distribution of cardiac output in anaesthetised horses.

The radioactive microsphere method was used to determine the distribution of cardiac output in six anaesthetised ponies. Simultaneous measurements of cardiac output allowed calculation of the tissue perfusions (ml/min/100 g). Allowing for the fact that measurements were carried out on animals under halothane anaesthesia and which had respiratory acidosis, the results were comparable with published values for other species.

Anesthesia, Inhalation↗

PubMed1979

[Assessment of the cardiac output by impedance cardiography (differential rheography) to give optimum continuous positive pressure ventilation (author's transl)].

It is very important to know the cardiac output in artificial positive pressure ventilation for the determination of the exact dosage of dopamine and the endexpiratory pressure. Invasive monitoring of the cardiac output is not suitable for routine bedside use. In our study we looked into the question of whether the dosage of dopamine in continuous positive pressure ventilation could be controlled by impedance determination. Differential rheography, as described by Kaindl, Polzer, and Schuhfried, was used in the study. Relative changes in cardiac output after dopamine administration are shown with sufficient accuracy using the above-mentioned method.

Cardiac Output↗

PubMed2001

Angiographic and prognostic correlates of cardiac output by cardiopulmonary exercise testing in patients with anterior myocardial infarction.

STUDY OBJECTIVE: To assess the diagnostic and prognostic value of cardiac output assessed by cardiopulmonary exercise testing in patients with anterior acute myocardial infarction (AMI) and left ventricular dysfunction. PATIENTS AND SETTING: Forty-six patients with AMI (7 female patients; mean +/- SD age, 55 +/- 8 years; ejection fraction, 39 +/- 7%) underwent cardiopulmonary exercise testing and coronary angiography following hospital discharge. MEASUREMENT AND RESULTS: Cardiac output was estimated from oxygen uptake (VO(2)) during exercise according to a method based on the linear regression between arteriovenous oxygen content difference and percent maximum VO(2). Angiograms were scored using Gensini and Duke "jeopardy" scores. Cardiac output at anaerobic threshold (COAT) < or = 7.3 L/min was the best cutoff value for identifying multivessel coronary artery disease (relative risk, 3.1). Angiographic scores were significantly higher in patients with COAT < 7.3 L/min as compared to those with COAT > 7.3 L/min (82 +/- 8 vs 53 +/- 7 and 6 +/- 2 vs 4 +/- 3, respectively; p < 0.05) and were inversely and significantly correlated to COAT. Conversely, no correlation was found with ECG changes. COAT, VO(2) at anaerobic threshold, and peak VO(2) were univariate prognostic indicators. However, using Cox's model, COAT was the only multivariate predictor of outcome (odds ratio, 0.28; 95% confidence interval [CI], 0.09 to 0.9). Moreover, COAT < 7.3 L/min was associated to an increased risk of further cardiac events (odds ratio, 5; 95% CI, 1.4 to 17) and provided a significant discrimination of survival for the combined end point of cardiac death, reinfarction, and clinically driven revascularization. CONCLUSIONS: COAT is a safe and feasible tool providing additional diagnostic and prognostic information in patients with AMI.

Aged↗

PubMed2005

Cardiac output monitoring using a brachial arterial catheter during off-pump coronary artery bypass grafting.

OBJECTIVE: To investigate the accuracy of cardiac output measurements by transpulmonary thermodilution and pulse contour analysis using a brachial arterial catheter. STUDY DESIGN: Criterion standard study. SETTING: University hospital, single institution. POPULATION: Twenty-three adult patients undergoing off-pump coronary artery bypass grafting. MEASUREMENTS AND MAIN RESULTS: Cardiac output was measured with a thermistor-tipped brachial arterial catheter using pulse contour analysis (COpc) and transpulmonary thermodilution (COba), which serves to calibrate COpc in the system tested. Both methods were compared separately with standard pulmonary artery thermodilution (COpa). COba was closely correlated with COpa (r = 0.93, p < 0.001). Bland-Altman analysis showed a bias of 0.91 L/min with limits of agreement of +/-0.98 L/min. COpc was also closely correlated (r = 0.80, p < 0.001) with COpa and was found to have a bias of 1.08 L/min with limits of agreement of +/-1.50 L/min. During the surgical procedure, changes in COpa from baseline were closely correlated with changes in COba (r = 0.90, p < 0.01) and COpc (r = 0.81, p < 0.01). CONCLUSIONS: The brachial arterial access allows a reliable assessment of cardiac output by transpulmonary thermodilution and pulse contour analysis in patients undergoing off-pump coronary artery bypass grafting.

Aged↗

PubMed1988

Cardiac output determinations in the newborn. Reproducibility of the pulsed Doppler velocity measurement.

Cardiac output (QAo) can be estimated noninvasively by pulsed Doppler (PD) ultrasonographic determination of mean ascending aortic blood flow velocity (VAo) combined with M-mode echocardiographic determination of ascending aortic cross sectional area (AAo). Cardiac output is calculated from the volumetric flow equation (QAo) = (VAo) X (AAo). Pulsed Doppler measurements are known to correlate well with Fick and thermodilution methods; however, inter- and intraoperator variability of the velocity component of the PD method has not been determined in newborns. We did three repeated PD measures of mean aortic flow velocity in ten term infants (using four trained operators) to determine inter- and intraoperator reproducibility. The coefficient of variation for intraoperator variability (random error) for a single measurement of VAo was 11.7%. If three repeated measures by a single operator were averaged, the random error was 7.0%. There was little interoperator variability found.

Aorta↗

PubMed1976

[Determination of cardiac output by means of an automatized thermal dilution technique (author's transl)].

Cardiac output was measured in 55 patients by the direct Fick method and an automatized thermodilution method. The results showed a good correlation (correlation factor r = 0.87, regression equation y = 0.91 x + 0.59). For the thermodilution method ice-cold normal saline solution as indicator substance was injected into the right atrium. The temperature-time-curve was measured by a thermistor located in the pulmonary artery. The area of indicator dilution was determined by electronic integration, the calculated cardiac output appeared as 1/min in digital display.

Autoanalysis↗

PubMed1978

Effect of chronic dietary saline loading on the fractional distribution of cardiac output and intrarenal circulation in the rat.

The effect of chronic saline loading for 3 weeks has been studied on the fractional distribution of cardiac output and intrarenal circulation in the rat. In response to the saline loading extracellular volume was slightly expanded and cardiac output moderately increased, the extent of which seemed to correlate with the fluid intake. Fractional organ flow distribution remained unaffected. Long-term saline loading resulted in a redistribution of intrarenal circulation characterized by an enhanced medullary blood flow, either isolated, or associated with an eventual dispropartional increase of cortical flow, while the renal fraction remained unaltered. On the basis of the results it is concluded that during long-term saline loading the augmentation of medullary circulation is a specific phenomenon characteristic of the kidney and is independent of the changes in cardiac output or other systemic haemodynamic effects. The isolated increase of medullary circulation is claimed to have a volume-regulatory function.

Animals↗

PubMed1995

The effect of cardiac output on the onset of neuromuscular block by vecuronium.

A relationship between cardiac output and the onset time of neuromuscular blockade administered into a peripheral vein was evaluated in 41 adult patients. Anaesthesia was induced with midazolam and fentanyl and maintained with intermittent doses of fentanyl and 66% nitrous oxide in oxygen. After immobilisation of the forearm in a splint, the ulnar nerve in the other arm was stimulated supramaximally every 10 s and the adduction force of the thumb was recorded. The times from administration of vecuronium 0.08 mg.kg-1 to first and 95% depression of twitch response was 82.4 (18.0) s and 191.7 (33.5) s (mean, SD), respectively. A significant correlation between cardiac index and the onset time of blockade was observed. This study demonstrated that the rapidity of the onset of paralysis in the adductor pollicis muscle after vecuronium injection into a peripheral vein is clearly related to cardiac output.

Adolescent↗

PubMed1980

[Assessment of cardiac output by a non-invasive method. Estimation of partial pressure of CO2 by rebreathing of expired gas. Comparison with thermodilution].

The cardiac output was measured in 65 patients by the FICK principle after estimation of the pp CO2 in mixed venous blood by rebreathing. This technique has been used mainly during exercise, and recently in intensive care units. We used it in resting patients hospitalised for diagnosis and treatment of a range of cardiac diseases, and in patients referred to our Physiological Laboratory. The reproductibility of our results using the rebreathing method was good: the variation of the individual results averaged 8.9%. The values of the cardiac output by rebreathing were compared to those obtained by thermodilution in 30 patients. A high coefficient of correlation was found: r = 0,897 (2p less than 0,001). This non-invasive technique is simple, rapid, and easily repeatible. Its use for serial estimations of the cardiac output should be retained.

Carbon Dioxide↗

PubMed2001

[Introduction and clinical evaluation of a new non-invasive cardiac output monitor (NICO) based on Fick partial CO2 rebreathing method].

A newly developed non-invasive monitor, NICO (Novametrix Medical Systems Inc.), measures cardiac output based on changes in respiratory CO2 concentration caused by a brief period of rebreathing. By applying modified form of the CO2 Fick principle, cardiac output is calculated. We determined the accuracy and precision of this technique (RBCO) by comparing it with continuous thermodilution technique (TDCCO) and pulse dye densitometry technique (PDD). The overall difference between RBCO and TDCCO(n = 46) was -0.21 +/- 1.43 (bias +/- 2 SD)l.min-1. On the other hand, the overall difference between RBCO and PDD (n = 53) was -0.1 +/- 2.04 (bias +/- 2 SD)l.min-1. The degree of accuracy of RBCO was thought to be the same as those of TDCCO and PDD. We expect that NICO will be a useful cardiac output monitor in any method of general anesthesia in which PA catheterization is difficult or not indicated.

Anesthesia, General↗

PubMed1991

Exercise capability in heart failure: is cardiac output important after all?

The exercise capability of 39 patients with severe chronic heart failure was assessed in several ways and compared with measurements of cardiac output. The relation between cardiac index and exercise tolerance measured on a treadmill was poor (r = 0.191, p = 0.245). However, exercise tolerance measured with a series of self-paced corridor walk tests showed moderate correlations with cardiac index (r = -0.404, p = 0.015 to r = -0.516, p = 0.001) and customary activity assessed by step counting correlated better with cardiac index (r = 0.537, p less than 0.001). Cardiac output therefore seems to be a factor determining patients' exercise capability when they choose their own walking speed but not when they undergo formal treadmill tests in the laboratory.

Aged↗