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PubMed1992

Continuous thermodilution cardiac output measurement in sheep.

A technique has been developed to continuously measure cardiac output by means of the principles of thermodilution. Pulmonary artery catheters were modified by placing a 10 cm filament near the usual injectate port. Small amounts of heat were infused according to a randomly repeating binary on-off sequence. The distal blood temperature was recorded and cross-correlated with the heat waveform to produce a dilution curve and calculate cardiac output. The technique was compared with bolus thermodilution in seven sheep. Cardiac output ranged from 1.5 to 13.2 L/min, and heart rate varied from 59 to 180 beats/min. The linear regression between the data obtained by the two methods is represented by the equation y = 1.00x + 0.13; the correlation coefficient, R, is 0.97, and the p value is less than 0.0001.

Animals↗
PubMed1977

Thallium-201: non-invasive determination of the regional distribution of cardiac output.

Sapirstein (1) employed cationic radiopotassium to determine the fractional distribution of cardiac output to several organs. Thallium-201 can substitute for radiopotassium in myocardial imaging, and was evaluated in the present studies to determine the distribution of cardiac output in the anesthetized dog in comparison with tracer microspheres, both under control circumstances and following the infusion of norepinephrine in a dose sufficient to raise the blood pressure 20 mm Hg above control levels. The concentrations of thallium-201 and microspheres were similar in the heart, kidney, thyroid, and skeletal muscle in both control and norepinephrine-treated animals (r=0.93). Thallium concentration in the liver and lung exceeded that of microspheres, however, and probably is not related solely to the regional distribution of arterial perfusion. These data suggest that in the heart, kidney, thyroid, and skeletal muscle, thallium-201 distribution reflects the fractional distribution of cardiac output.

Animals↗
PubMed1983

Thermodilution cardiac output determination in hypothermic postcardiac surgery patients: room vs ice temperature injectate.

In normothermic patients, room temperature and ice temperature injectate have been shown to result in comparable thermodilution cardiac output measurements. However, room temperature injectate may give inaccurate results in hypothermic patients, particularly if the injectate volume is small, because of the lower injectate-to-blood temperature differential. We compared determinations of cardiac output using 10- and 5-ml volumes of room temperature (19-25 degrees C) injectate to those using 10-ml volumes of ice temperature (0-5 degrees C) injectate in 26 hypothermic (32.7 +/- 1.2 degrees C) postcardiac surgery patients. The cardiac outputs ranged from 1.8 to 5.3 L/min. Regression analysis demonstrated a close relationship between the cardiac outputs measured using room temperature injectate compared to those using ice temperature injectate (0.951 for the 10-ml volumes, 0.925 for the 5-ml volumes). We conclude that the room temperature injectate method is acceptable for determining thermodilution cardiac outputs in moderately hypothermic patients.

Adult↗
PubMed1990

Measurement of cardiac output by the thermodilution method during left thoracotomy in the lateral position in the dog.

The validity of cardiac output measurement by thermodilution in the lateral position during thoracotomy was assessed. Three balloon thermodilution Swan-Ganz catheters were placed in the pulmonary artery trunk and the right and left pulmonary arteries in 12 mongrel dogs, after left thoracotomy had been performed. Cardiac output was measured simultaneously from two of the three sites. The cardiac output measurements show no significant difference related to the location of the catheter extremities: the mean cardiac index was found to be 2.164 +/- 0.448 l/min/m2 from the pulmonary artery trunk, 2.127 +/- 0.404 l/min/m2 from the left branch and 2.116 +/- 0.421 l/min/m2 from the right branch. It is concluded that the measurement of cardiac output during left thoracotomy is valid, whether the thermistor is situated in the pulmonary artery trunk or in a main branch to either the dependent or non-dependent lung.

Animals↗
PubMed1982

The effect of hyperacetatemia on cardiac output during regular hemodialysis.

We used impedance cardiography to monitor changes in cardiac output in 22 adult patients with terminal renal failure during hemodialysis against a dialyzate containing acetate. In 7 patients arterial acetate levels rose progressively during dialysis while in the remainder they remained low and steady. Patients who developed hyperacetatemia were able to maintain an elevated cardiac output during dialysis in contrast to the patients with stable acetate levels in whom cardiac output fell. These results strengthen our previous conclusion that acetate as used in conventional regular hemodialysis does not have a cardiodepressant action. The reported benefits of bicarbonate dialysis therefore involve other factors.

Acetates↗
PubMed1994

On-line estimation of cardiac output with a new automated border detection system using transesophageal echocardiography: a preliminary comparison with thermodilution.

Continuous estimation of cardiac output would be extremely useful for hemodynamic monitoring of patients in the operating room and intensive care settings. A recently developed echocardiographic imaging system provides real-time automated border detection (ABD) with the ability to measure cyclic changes in cavity area, and thus calculate changes in intracavitary volumes. Eight patients undergoing cardiac surgery were studied with intraoperative transesophageal (TEE), and cardiac outputs obtained with this new imaging system were compared with thermodilution (TD). Triplicate measurements were obtained simultaneously at five intraoperative times, three before and two after cardiopulmonary bypass. The 91 of 120 measurements with adequate TEE and TD data were analyzed. The average difference between the two techniques (bias) was -0.2 +/- 1.3 L/min. The limits of agreement (bias +/- 2 SD) were -2.8 L/min to 2.4 L/min. The average of the absolute value of the difference between measurements made with the two techniques was 0.9 +/- 0.8 L/min. Linear regression yielded the equation: ABD = 0.64TD + 1.57 L/min (r = 0.71). The average difference between the two techniques (bias) for detecting changes in cardiac output between sequential intraoperative times was 0.1 +/- 1.1 L/min. With further development, this new method shows promise for measurement of cardiac output in selected patient care settings.

Adult↗
PubMed1986

Non-invasive assessment of cardiac output and stroke volume in patients during exercise. Evaluation of a CO2-rebreathing method.

A one-step CO2 rebreathing method for the determination of cardiac output and stroke volume (SV) has been evaluated by comparison with the direct Fick technique during recumbent exercise (10-90 W) in 13 patients. In an initial analysis, the influence of different rebreathing times and of correction for haemoglobin concentration was studied. The best correlation with the direct Fick technique was obtained with the longest analysis time, i.e. 21 s, and correction for variations in haemoglobin concentration further improved the correlation. Consequently, an analysis time of 21 s and correction for haemoglobin have been used. At low cardiac outputs, the CO2-rebreathing method overestimated the flow compared to the Fick technique. The correlation between the methods, however, was so good that a valid estimate of cardiac output could be obtained from the CO2 rebreathing method with appropriate corrections (Cardiac output, CO2 method = 2.7 + 0.77. Cardiac output, Fick; r = 0.91; Residual Standard deviation (SD res) = 0.77 l X min-1). Stroke volumes measured with the CO2 rebreathing method did not differ significantly from those obtained with the direct Fick technique, although there was a tendency to overestimate stroke volume with the CO2 rebreathing method (SV, CO2 method = 12 + 0.89 X SV, Fick; r = 0.82; SD res = 11 ml).

Adult↗
PubMed1995

Influence of the renal nerves on sodium excretion during progressive reductions in cardiac output.

The purpose of this study was to elucidate the role of the renal nerves in promoting sodium retention during chronic reductions in cardiac output. In five dogs, the left kidney was denervated and the urinary bladder was surgically divided to allow separate 24-h urine collection from the innervated and denervated kidneys. Additionally, progressive reductions in cardiac output were achieved by employing an externally adjustable occluder around the pulmonary artery and by servo-controlling right atrial pressure (control = 0.9 +/- 0.2 mmHg) at 4.7 +/- 0.1, 7.5 +/- 0.1, and 9.8 +/- 0.2 mmHg for 3 days at each level. At the highest level of right atrial pressure, the 24-h values for mean arterial pressure (control = 97 +/- 3 mmHg) and cardiac output (control = 2,434 +/- 177 ml/min) were reduced approximately 25 and 55%, respectively; glomerular filtration rate fell by approximately 35% and renal plasma flow by approximately 65%. However, despite the sodium retention induced by these hemodynamic changes, there were no significant differences in renal hemodynamics or sodium excretion between the two kidneys during pulmonary artery constriction. In contrast, after release of the pulmonary artery occluder on day 9, sodium excretion increased more (approximately 28% during the initial 24 h) in innervated than in denervated kidneys. These results suggest that the renal nerves are relatively unimportant in promoting sodium retention in this model of low cardiac output but contribute significantly to the short-term elimination of sodium after partial restoration of cardiac output and mean arterial pressure.

Animals↗
PubMed1998

Validation of cardiac echocardiography for measuring cardiac output to be applied for the multiple inert gas elimination technique.

The multiple inert gas elimination technique (MIGET) is being increasingly used in respiratory physiology and pathophysiology. Six inert gases are given as an intravenous infusion then measured in samples of expired air and mixed arterial and venous blood. This requires right-sided catheterization, a procedure that is sometimes ethically inappropriate. The present article reports a method in which inert gas levels in mixed venous blood were calculated, rather than measured, using Fick's law. Echocardiography was used to measure arterial inert gas levels and cardiac output. The method was validated in 11 men scheduled to undergo coronary bypass surgery. Cardiac output was either calculated based on biometrical (C) data or measured using four different methods in random order, namely Fick's law with oxygen (FiO2) or the inert gases (FiIG) as the tracers, thermodilution (TH), and echocardiography (E). Cardiac output values in L.min-1 (mean +/- SD) were as follows: C, 4.99 +/- 0.39; FiO2, 5.44 +/- 0.86; FiIG, 5.55 +/- 0.92; TH, 5.77 +/- 0.88; and E, 5.53 +/- 0.64. No significant differences were found among the four measured cardiac output values, of which the mean was 5.57 +/- 0.70 L/min, a value that was significantly higher than the calculated value. This difference is probably ascribable to the use of dopamine, dobutamine, or epinephrine in six of the 11 patients. A 1 L/min-1 cardiac output error, in either direction, was found to have a marked influence on the distribution of alveolar perfusion at various VA/Q ratios. Conversely, as expected, ventilation distribution was not influenced by cardiac output. In conclusion, echocardiography provides satisfactory cardiac output estimations using the MIGET except in patients with septal hypertrophy, subaortic membranes, a mitral valve prosthesis, or a mitral valve ring.

Adult↗
PubMed1992

Validity of cardiac output measurement by computer-averaged impedance cardiography, and comparison with simultaneous thermodilution determinations.

The accuracy and reproducibility of noninvasive cardiac output determinations by computer-averaged impedance cardiography were compared with those of simultaneously performed thermodilution cardiac output. In all, 43 patients (14 men and 29 women = 201 pairs) were studied by simultaneously performed impedance and thermal determinations. Individual impedance values correlated with paired thermodilution determinations (r = 0.75; p less than 0.0001). Each patient's average thermodilution values correlated with the average impedance values (r = 0.86; p less than 0.0001). Mean thermodilution output was 4.6 +/- 1.37 liters/min. Mean impedance output was 4.5 +/- 1.27 liter/min Reproducibility was comparable for impedance (0.0059 +/- 0.639) and thermodilution cardiac output (0.023 +/- 0.556). There was high agreement between methods by plot of the difference against mean of the 2 methods. Impedance cardiac output values agree and correlate highly with quality-controlled thermodilution outputs across a wide range of clinical conditions and hemodynamic values.

Adult↗
PubMed1984

Changes in regional blood flow and cardiac output after L-glutamate stimulation of A5 cell group.

Changes in regional blood flow and cardiac output were measured by the reference organ method in pentobarbital-anesthetized rats with radioactive microspheres (15 microns) before and after chemical stimulation of the A5 cell group with the excitatory amino acid L-glutamate an agent that excites cell bodies but not fibers of passage. This stimulation caused a decrease in mean arterial pressure, heart rate, cardiac output, and calculated stroke volume. The limb skeletal muscles showed a large increase in blood flow and decrease in vascular resistance, whereas the trunk musculature showed no change in flow or resistance. The blood flow of the entire gastrointestinal tract decreased. Blood flow in the skin decreased with no change in resistance. The cardiac muscle of the ventricles showed a decrease in flow without a change in resistance. The ipsilateral half of the brain showed a decrease in blood flow, while the contralateral side showed no change. The kidneys exhibited no change in blood flow and a decrease in resistance. A5 stimulation in guanethidine-sympathectomized rats caused no change in regional blood flow. In contrast, an increase in cardiac output was observed, and the possible interpretations for this change are discussed. Rats treated with intraventricular injections of 6-hydroxydopamine showed no changes in regional blood flow or cardiac output, indicating that catecholamine neurons are involved in these responses.

Animals↗
PubMed1975

Mechanisms of enhancement of cardiac output during paced tachycardia in conscious dogs.

The mechanisms of enhancement of cardiac output of unanesthetized dogs from 2.7 to 3.6 l min-1 during paced heart rate increase from 92 to 178 beats min-1 were studied in 92 trials with 5 dogs. This enhancement of cardiac output was accompanied by a 0.6 mm Hg fall in right atrial pressure and a 3.3 mm Hg fall in left ventricular end-diastolic pressure. The results are compatible with the hypothesis that an isolated rise in cardiac function shifts blood from the heart and lungs into the systemic circulation which increases the degree of filling of the peripheral vessels and hence increases mean systemic pressure. We postulate that decompression of both atria reflexly raises the tone of the peripheral vessels while the increase in arterial blood pressure reflexly lowers the tone. Apparently a balance is achieved that results in an elevated mean systemic pressure, displacement of the venous return curve to the right, and an increase in the amount of venous return that matches the enhanced cardiac output.

Animals↗
PubMed1977

Tissue blood flow and distribution of cardiac output in cats: changes caused by intravenous infusions of histamine and histamine receptor agonists.

1 The effects of infusions of histamine on blood pressure, cardiac output, heart rate, total peripheral resistance, stroke volume and tissue blood flow have been determined in anaesthetized cats using radio-active microspheres to measure cardiac output and tissue blood flow.2 Histamine caused dose-dependent falls in blood pressure and total peripheral resistance over the dose-range 1 x 10(-8) to 3.3 x 10(-7) mol kg(-1) min(-1). Histamine had no effect on cardiac output, heart rate or stroke volume.3 Histamine caused vasodilatation in the heart and stomach, with increased blood flow through these organs, and in the small and large intestine where blood flow was maintained despite the falls in arterial blood pressure. Blood flow to the brain, kidneys, liver, adrenal glands, skeletal muscle, spleen and skin was reduced when arterial blood pressure fell. Vascular resistance increased in the skin and spleen, presumably due to reflex vasoconstriction when blood pressure fell.4 The selective H(1)-receptor agonist 2-(2-aminoethyl)pyridine lowered blood pressure and decreased total peripheral resistance but did not change cardiac output, heart rate or stroke volume. 2-(2-Aminoethyl)pyridine caused vasodilatation in the heart, small and large intestine and kidneys. Vascular resistance was increased in the spleen and skin.5 The selective H(2)-receptor agonist 4-methylhistamine also lowered blood pressure and decreased total peripheral resistance but did not change cardiac output, heart rate or stroke volume. 4-Methylhistamine caused vasodilatation in the heart, stomach, small and large intestines and skeletal muscle. Vascular resistance was increased in the skin.

Animals↗
PubMed1992

Comparison of cardiac output determinants in response to upright and supine exercise in patients with cystic fibrosis.

This study characterizes cardiac output response to progressive submaximal upright cycling in CF patients. Thirty-one CF patients as well as 11 aged-matched CF control subjects completed cardiac output determinations (CO2-rebreathing) at rest, and at submaximal exercise corresponding to 30, 50 and 75 percent VO2max, in both upright and supine positions. The VO2max was similar in three of four groups, but lower in those with severe CF. The cardiac output generally increased with exercise intensity in both positions, except in severe CF. The change from upright to supine posture resulted in a significant increase in SI at rest and for every submaximal exercise in control subjects, but not CF patients. These observations may suggest that the abnormal cardiac output response observed in severe CF could be related to a potential limitation in ventricular diastolic reserve found in all CF patients independent of disease severity which becomes more apparent under increased ventricular preload.

Adolescent↗
PubMed2003

Cardiac output determined by echocardiography in patients with cirrhosis: comparison with the indicator dilution technique.

BACKGROUND/AIMS: Measurement of cardiac output in hyperkinetic patients with cirrhosis by Doppler echocardiography is increasingly reported, but has not been validated. We have compared simultaneous measurements of cardiac output by Doppler echocardiography (CO(d)) and by the indicator dilution technique (CO(I)). METHODS: Twelve patients with cirrhosis were studied. CO(d) was measured as the spatial mean velocity of the left ventricular outflow tract, multiplied by the cross-sectional area and the heart rate. CO(I) was determined by the standard indicator dilution technique after injection of 125I albumin and 99mTc albumin into the right atrium and subsequent sampling from the femoral artery. RESULTS: The mean CO(d) and CO(I) were similar (7.20 vs 7.15 l/min, NS). A highly significant correlation was present between CO(d) and CO(I) (r = 0.86, P < 0.0001; slope 0.91, Y(0) = 0.78 l/min). However, the mean squared difference between CO(d) and CO(I) was 2.3 (l/min)2. A Bland-Altman plot revealed no trend with the level of cardiac output. The standard deviation (0.79 vs 0.30 l/min, P < 0.01) and the coefficient of variation (10.5 vs 4.2%, P < 0.01) of duplicate measurements were significantly higher with the Doppler technique. CONCLUSION: Doppler measurements of cardiac output in groups of patients with cirrhosis are accurate with respect to the group mean, but marked disagreements of over- and underestimation were seen in individual patients. The reproducibility of the Doppler technique is acceptable, although not as good as that of the indicator dilution technique.

Adult↗
PubMed1991

Continuous cardiac output determination by thermodeprivation.

A modified thermodilution catheter (KATS catheter) capable of monitoring continuous cardiac output by thermodeprivation and preserving its conventional function was devised. The KATS catheter has a thermistor incorporated closer to the tip of the catheter in addition to the usual thermistor used for conventional thermodilution. This additional thermistor is heated by a constant electric current but is capable of measuring its own temperature. The degree of heat deprivation is detected as the cooling of the thermistor, which is proportionally larger with larger blood velocity. Since blood flow is not the only source of heat deprivation, the actual formula was empirically derived by performing in vitro studies. Cardiac output can be determined by assuming the cross sectional area of the pulmonary artery is stationary. Calibration can be derived from a cardiac output measurement by the usual thermodilution method with the same catheter. The KATS catheter readings correlated significantly with conventional thermodilution values and electromagnetic flowmeter readings in anesthetized dogs. Continuous cardiac output measurement by the KATS catheter appears to be a promising technique.

Journal Article↗
PubMed1984

Non-invasive measurement of cardiac output by a single breath constant expiratory technique.

A new single breath test has been developed that measures pulmonary blood flow (Qc) and pulmonary tissue volume by using the fact that Qc is proportional to the relationship between the absorption rate of acetylene (C2H2) from the alveolar gas and the rate of change of lung volume during constant expiratory flow. To make these measurements a bag in bottle system with a rolling seal spirometer, a mass spectrometer, and a minicomputer with analogue to digital conversion have been used. Qc was compared with cardiac output measured by the thermodilution technique in 20 patients with cardiac disease; some also had mild chronic obstructive pulmonary disease. The mean (SD) resting Qc for the group was 5.27 (1.22) l/min and the cardiac output measured by thermodilution was 5.30 (1.31) l/min. The mean difference between the two estimations of cardiac output was 0.03 l and the standard deviation of this difference was 0.76 l. The Qc technique was not successful in patients with an FEV1/FVC less than 60%, but seemed to be accurate in those with higher FEV1/FVC values. Correction of Qc for the effect of venous admixture in 14 patients resulted in an average 19% overestimation of cardiac output (6.01 (2.52) l/min v 5.05 (1.64) l/min). It is concluded that cardiac output can be accurately measured in patients with cardiac or mild pulmonary disease. No correction for venous admixture due to ventilation-perfusion mismatch was necessary in these patients, presumably because the large breath used by the technique overcomes most mild ventilation-perfusion maldistribution. These findings, in addition to the non-invasive nature of the technique, suggest potential value for the measurement of cardiac output in various clinical conditions.

Adult↗
PubMed1990

Validation of impedance cardiography measurements of cardiac output during limited exercise in heart transplant recipients.

Twenty-one patients were studied at rest and during exercise after heart transplantation to compare cardiac output measured by thermodilution and impedance cardiography. Exercise was performed on a bicycle ergometer over a limited range of work load (25 and 50 watt) whilst metabolic gas exchange was recorded. One patient was studied at rest whilst his circulation was maintained by a Jarvik-7 artificial heart. The values of cardiac output measured by impedance cardiography corresponded closely with the flow rate from the artificial heart. There was also close agreement between the impedance and thermodilution measurements of cardiac output at rest and during exercise. Both measurements followed the changes in heart rate and oxygen consumption. Both thermodilution and impedance cardiography methods elicited good reproducibility of cardiac output measurements at rest and during exercise. These observations suggest that the noninvasive and continuous record of cardiac output obtained by impedance cardiography can be used for the postoperative monitoring of heart transplant recipients.

Adult↗