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PubMed1979

Automated computer program for radionuclide cardiac output determination.

Radionuclides have provided a safe, reliable, and minimally invasive method for repeated determinations of cardiac output. A completely automated computer program for data analysis is described. Cardiac output values obtained by this technique correlated closely with values obtained by manual determination of the region of interest (r = 0.90 for right-ventricular and 0.98 for left-ventricular outputs, p less than 0.001 for both). Further, cardiac output determined by computer selection of either left-ventricular area of interest or of the "whole heart region" correlated significantly with that simultaneously determined by dye-dilution technique (indocyanine green; r = 0.86, p less than 0.001 for both). The automated approach allows greater objectivity in the selection of the regions of interest, faster turnaround of calculated results, and use of a smaller dose of radionuclide.

Adult↗
PubMed2006

The impact of intra-aortic balloon pumping on cardiac output determination by pulmonary arterial and transpulmonary thermodilution in pigs.

OBJECTIVE: The aim of this study was to evaluate the impact of intra-aortic balloon pumping (IABP) on the comparison of simultaneous measurements of cardiac output via pulmonary arterial and transpulmonary thermodilution (PiCCO; Pulsion Medical Systems, Munich, Germany). DESIGN: Prospective. SETTINGS: University research laboratory. PARTICIPANTS: The data were derived from 9 anesthetized (fentanyl, propofol, flunitrazepam, rocuronium) and ventilated pigs. INTERVENTIONS: A thermodilution catheter was inserted into the pulmonary artery, a PiCCO catheter into the abdominal aorta through the right femoral artery, epicardial atrial pacing wires through a thoracotomy, and a balloon catheter for counterpulsation into the descending thoracic aorta through the left femoral artery. Cardiac output was varied over a wide range by cardiac pacing between 80 and 150/min in steps of 10/min and was measured without and during IABP at an assist frequency of 1:1. MEASUREMENTS AND MAIN RESULTS: A total of 236 paired cardiac output measurements were carried out in a range of cardiac output between 1.4 to 4.9 L/min. A close correlation was found between transpulmonary and pulmonary arterial thermodilution both without and during IABP (r = 0.94 and 0.93, respectively) and a good agreement of both methods (bias of 0.30 and 0.26 L/min, respectively; precision 0.47 and 0.52 L/min, respectively). CONCLUSIONS: Transpulmonary thermodilution is suitable for cardiac output measurement during IABP. Hence, in critically ill patients with cardiac pump failure, blood flow may be determined as accurately with the less-invasive transpulmonary method as with the traditional pulmonary arterial thermodilution one.

Animals↗
PubMed1997

Effects of adenosine and adenosine analogues on mean circulatory filling pressure and cardiac output in anesthetized rats.

The effects of adenosine and adenosine analogues, 2-[p-(2-[carboxyethyl) phenethylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680) and N6-2-(4-aminophenyl)-ethyladenosine (APNEA), on mean arterial pressure, cardiac output, mean circulatory filling pressure, arterial resistance, venous resistance and heart rate in untreated or treated (with ganglion-blockers mecamylamine and atropine) pentobarbital-anesthetized rats were examined. Infusion of adenosine (100, 300 and 900 microg/kg/min), CGS 21680 (0.1, 0.3 and 0.9 microg/kg/min) or APNEA (1.0, 3.0 and 9.0 microg/kg/min) reduced mean arterial pressure and arterial resistance in all groups. Adenosine and APNEA also reduced mean circulatory filling pressure, venous resistance and heart rate in untreated animals. Furthermore, APNEA but not adenosine reduced cardiac output. In contrast, CGS 21680 increased cardiac output and heart rate but did not have any effect on mean circulatory filling pressure or venous resistance. In ganglion-blocked rats, APNEA reduced cardiac output, mean circulatory filling pressure and heart rate, while adenosine did not have any effect on these parameters. In addition, APNEA and adenosine reduced arterial resistance but were unable to alter venous resistance while CGS 21680 reduced mean circulatory filling pressure and arterial resistance but did not further affect cardiac output, heart rate and venous resistance in ganglion-blocked animals. The results of the present study suggest that adenosine and APNEA dilate arterioles and vein, whereas CGS 21680 causes arterial dilatation but not venodilatation in untreated animals due to hypotension-induced sympathetic activation. A possible explanation for the present observations could be differences in the distribution of vascular A2 versus A3 adenosine receptors in the venous circulation.

Adenosine↗
PubMed1999

Development of a system to record cardiac output continuously in the newborn.

Intermittent recordings of Doppler flow velocity and cardiac output are of value during intensive care of the sick newborn infant but result in repeated disturbance of the child. We describe a new device for making continuous precordial recordings of Doppler flow velocity from the pulmonary artery in healthy resting newborn infants. Optimal probe siting was evaluated in six babies, and signals were found to be best when the pulmonary artery was insonated from the mid left parasternum. Continuous recordings were made in 13 other babies. Pulmonary artery velocities and, by calculation, cardiac output were measured continuously over periods ranging from 24 to 60 min. Median right ventricular output ranged widely from 148 to 246 mL x kg(-1) x min(-1). In contrast, for individual babies, the values were remarkably stable: the interquartile ranges varied from 13.2 to 29.9 mL x kg(-1) x min(-1). The simultaneous display of signal power allowed independent assessment of artifactual changes in cardiac output. This technique is feasible in healthy term infants and now requires evaluation in the intensive care setting where it may provide useful information concerning trends and short-term variability in right ventricular output.

Cardiac Output↗
PubMedDate not supplied

Effect of hemodialysis on blood volume distribution and cardiac output.

Effects of hemodialysis on extracellular fluid volume distribution, left ventricular volumes, and cardiac output were determined in patients with end-stage renal disease (n = 19). Distribution of extracellular fluid loss from hemodialysis differed widely among patients, so that weight change correlated weakly with contraction of total blood volume (index of determination 29%, p less than 0.05). End-diastolic volume (EDV) decreased from 150 +/- 49 ml (mean +/- SD) to 118 +/- 42 ml, p less than 0.001; stroke volume (SV) decreased from 108 +/- 36 to 86 +/- 33 ml (p less than 0.001) without change in ejection fraction (from 0.73 +/- 0.09 to 0.74 +/- 0.11). A significant correlation was found between total blood volume (TBV) and EDV before (r = 0.66, p less than 0.005) and after dialysis (r = 0.61, p less than 0.001). The correlation between TBV and SV was highly significant before (r = 0.78, p less than 0.001) and after dialysis (r = 0.66, p less than 0.005), but there was no correlation between change in TBV and change in EDV or in SV. The ratio of EDV to TBV (EDV/TBV x 100) was reduced significantly from 3.49 +/- 0.92 to 3.06 +/- 0.97, p less than 0.001). There results suggest that, although intravascular volume was the major determinant of cardiac output in dialyzed patients, the postdialysis reduction in cardiac output might be related more to the relocation of blood volume than to the absolute degree of blood volume contraction.

Blood Volume↗
PubMed1985

Modification of focal cerebral ischemia by cardiac output augmentation.

Intravascular volume expansion has been employed successfully for treatment of ischemic stroke from cerebral vasospasm and from cerebrovascular occlusive disease. The physiologic mechanism responsible for this success has not previously been delineated in controlled experimentation. The objective of this investigation was to delineate the effects of cardiac output and of hemodilution in a primate model of focal cerebral ischemia. Two groups of anesthetized rhesus monkeys received extensive cardiovascular monitoring, and local cerebral blood flow (lCBF) was determined in both ischemic and nonischemic brain regions by the hydrogen clearance method. Both groups were subjected to unilateral middle cerebral artery occlusion. One group then underwent blood volume expansion with Dextran 40 (cardiac output augmentation), and one group underwent isovolemic hemodilution with Dextran 40, cardiac output being maintained constant. Significant increases in lCBF occurred in ischemic regions only and occurred only in response to augmentation of cardiac output. Isovolemic hemodilution failed to produce any changes in lCBF. This investigation indicates that ischemic brain regions are selectively vulnerable to alterations in cardiac output, these effects being independent of alterations in blood pressure. Blood viscosity changes may play only a minor role. This study strongly suggests an important role of intravascular volume expansion and cardiac output augmentation in treatment of acute ischemic stroke.

Animals↗
PubMed1976

Reference sample method for cardiac output and regional blood flow determinations in the rat.

The reference sample method was used for simultaneous determinations of cardiac output and regional blood flows in conscious rats. Microspheres (15 +/- 5 mum in diam) labeled with strontium-85 were injected into the left ventricle and known volumes of reference sample were withdrawn from peripheral arteries. The calculated cardiac output measurements agreed with the previously reported values in rats. The percent distribution of the cardiac output to the brain, intestinal bed, and lungs were different from the reported values obtained in the rats using larger spheres. These differences may be related to the use of smaller spheres and to differences in the preparation. The absolute regional flows to various organs expressed in terms of milliliters per minute per gram tissue weight were also determined. The results indicate that the reference sample method can be applied to smaller mammals for determinations of regional flows and cardiac output.

Animals↗
PubMed1997

Lithium dilution cardiac output measurement: a comparison with thermodilution.

OBJECTIVE: To compare the results of cardiac output measurements obtained by lithium dilution and thermodilution. DESIGN: Case series, observational study. SETTING: High-dependency postoperative unit and intensive care unit of a teaching hospital. PATIENTS: Forty patients were studied. Thirty-four patients had undergoing heart surgery requiring cardiopulmonary bypass within the previous 2 days; the diagnoses in the other patients were myocardial infarct (n = 2), septicemia (n = 2), adult respiratory distress syndrome, and pericardectomy. INTERVENTIONS: Cardiac output was measured five times in each patient, using lithium dilution (single measurement) and bolus thermodilution (series of three to six measurements according to standard clinical practice, taking the average of the closest three). In a subgroup of 14 patients, cardiac output was also measured using "continuous thermodilution." MEASUREMENTS AND MAIN RESULTS: Comparing lithium dilution with bolus thermodilution, the mean of the differences (lithium dilution-thermodilution) was -0.25 +/- 0.46 [SD] L/min. Linear regression analysis gave y = 0.31 + 0.89x (r2 = .94) for lithium dilution vs. thermodilution. CONCLUSIONS: The overall agreement between the two methods was good. The variability of the thermodilution measurements was greater than that of the lithium dilution measurements. The lithium dilution method is at least as accurate as bolus thermodilution and, since pulmonary artery catheterization is not needed, it has the advantages of being safe and quick to perform.

Adult↗
PubMed2002

Assessment of arterial gas pressures and cardiac output using a breathing lung model.

PURPOSE: The aim of this investigation was to evaluate a breathing lung model to estimate arterial gas partial pressures and cardiac output at rest and during exercise. METHODS: A mathematical model was used to describe variations in gas fractions, alveolar volume, and gas exchange in the pulmonary capillaries during the breathing cycle. Experimental data were obtained from 17 healthy subjects at rest and during exercise at 40, 50, 65, and 75% VO(2max) on a cycle ergometer. VO(2), VCO(2), and P(ET,CO2) were monitored continuously with a MedGraphics CPX/D gas exchange system. Arterial gases were measured in brachial artery blood samples drawn simultaneously with gas exchange. Cardiac output was measured using the CO(2) rebreathing method corrected by the arterial blood sample data. The model parameters including cardiac output, end-expiratory alveolar volume, and mixed-venous gas contents were estimated by fitting modelVCO(2) to experimental values over 50 breaths. RESULTS: The fit of model parameters gave arterial gas partial pressures not significantly different from measured data. Measured P(a,C02) and P(a,O2) were significantly correlated with model outputs (R(2) = 0.991 for P(a,CO2) and R(2) = 0.999 for P(a, CO2); P < 0.0001). The cardiac output values estimated using the breathing lung model were significantly correlated with the values obtained with the corrected CO rebreathing method (R(2) = 0.71; P < 0.0001). There was, however, a significant 2.3 L x min(-1) difference between these two methods. CONCLUSION: Results obtained with the proposed method were in good agreement with measured arterial gas partial pressures. Despite a certain degree of bias, the promising results for cardiac output demonstrate the reliability of this method that should be now evaluated using a gold standard method.

Adult↗
PubMed1999

Thermal filament continuous thermodilution cardiac output delayed response limits its value during acute hemodynamic instability.

BACKGROUND: It has been suggested that measurement of continuous cardiac output (CCO) is an advancement in the management of critically ill patients. Our objective was to determine the accuracy of CCO during the rapid hemodynamic changes induced by hemorrhage and resuscitation. METHODS: In 12 anesthetized dogs (20.2+/-0.9 kg), pulmonary artery blood flow, our "gold standard" cardiac output, was measured with an sonographic flowprobe, whereas CCO, intermittent bolus cardiac output (ICO), and mixed venous oxygen saturation were measured with a thermodilution fiberoptic pulmonary artery catheter with a thermal filament. A graded hemorrhage (20 mL/min) was produced to a mean arterial pressure of 40 mm Hg, which was maintained at this level for 30 minutes. Total shed blood volume (701+/-53 mL) was retransfused at a rate of 40 mL/min, over 30 minutes, after which a massive hemorrhage (100 mL/min) was produced over 10 minutes. RESULTS: Hemorrhage induced significant decreases in mean arterial pressure, mixed venous oxygen saturation, and oxygen delivery, which were all restored during early resuscitation. However, CCO showed a delayed response after hemorrhage and resuscitation, compared with pulmonary blood flow, throughout the study (r = 0.549), matching only at baseline and at the end of both graded hemorrhage and resuscitation periods. There was a good correlation between ICO and pulmonary artery blood flow (r = 0.964) and no significant differences between them throughout the study. CONCLUSION: CCO has a delayed response during acute hemodynamic changes induced by hemorrhage and resuscitation. When sudden changes in mean arterial pressure or in mixed venous oxygen saturation are detected, cardiac output must be estimated by the standard bolus thermodilution technique, not by CCO.

Animals↗
PubMed1987

First-pass radionuclide determination of cardiac output: an improved gamma camera method.

A technique for noninvasive determination of cardiac output by aid of first-pass radionuclide cardiography is described. After intravenous injection of 10-15 mCi technetium-99m-(99mTc) labeled red blood cells the method requires acquisition of a first passage time-activity curve recorded with a gamma camera over the left ventricle, the background corrected left ventricular count rate recorded after complete mixing of the tracer in the circulation, and determination of the distribution volume of the tracer. The method was applied in 14 patients with heart disease of various origins and evaluated against the conventional tracer dilution technique with arterial sampling of blood activity. Cardiac output determinations by external counting ranged from 2.30 to 8.56 l/min, mean +/- s.d. 4.50 +/- 1.66 l/min and by arterial blood sampling from 1.88 to 8.96 l/min, mean +/- s.d. 4.52 +/- 1.71 l/min. An excellent correlation was demonstrated between the two techniques, r = 0.978 (p less than 0.001). When no background subtraction was applied to the left ventricular counts at equilibrium, radionuclide cardiac output values were approximately 40% higher than those obtained by arterial sampling. The new first-pass radionuclide cardiographic technique may prove a useful tool in the noninvasive evaluation of cardiac function, especially in patients with arrhythmias and/or valvular incompetence.

Adult↗
PubMed2003

A comparative evaluation of thermodilution and partial CO2 rebreathing techniques for cardiac output assessment in critically ill patients during assisted ventilation.

OBJECTIVE: To evaluate the reliability and clinical value of partial noninvasive CO2 (NICO2) rebreathing technique for measuring cardiac output compared with standard thermodilution in a group of intensive care nonpostoperative patients. DESIGN AND SETTING: Clinical investigation in a university hospital ICU. PATIENTS: Twelve mechanically ventilated patients with high (n=6) and low (n=6) pulmonary shunt fractions. MEASUREMENTS AND RESULTS: Thirty-six paired measurements of cardiac output were carried out with NICO2 and thermodilution in patients ventilated in pressure-support mode and sedated with a sufentanil continuous infusion to obtain a Ramsay score value of 2. The mean cardiac output was: thermodilution 7.27+/-2.42 l/min; NICO2 6.10+/-1.66 l/min; r2 was 0.62 and bias -1.2 l/min+/-1.5. Mean values of cardiac output were similar in the low shunt group (Qs/Qt < 20), with r2=0.90 and a bias of 0.01 l/min+/-0.4; conversely, in the high pulmonary shunt group (Qs/Q > 35%) the mean was 9.32+/-1.23 l/min with thermodilution and a mean NICO2CO value was 6.97+/-1.53 l/min, with r2 of 0.38 and a bias of -2.3 l+/-1.2 min. CONCLUSIONS: The partial CO2 rebreathing technique is reliable in measuring cardiac output in nonpostoperative critically ill patients affected by diseases causing low levels of pulmonary shunt, but underestimates it in patients with shunt higher than 35%.

Anesthetics, Intravenous↗
PubMed1976

Simultaneous measurement of cardiac output and its distribution with microspheres in the rat.

The radioactive microsphere method was used to estimate simultaneoulsy the cardiac output and its distribution in the same rat by the use of an arterial reference sample obtained during microsphere distribution. Sufficient microspheres were injected so that all counted samples contained more than 400 spheres. No haemodynamic changes occurred during microsphere injection. The results for cardiac output of 253 +/- 11 ml/min per kg body weight agree with published estimates utilizing other techniques. The distribution of cardiac output also agrees with most published reports. This method should allow the rat to be conveniently used for certain haemodynamic studies when cardiac output and organ blood flow are necessary.

Animals↗
PubMed1992

Thoracic electrical bioimpedance measurement of cardiac output and cardiovascular responses to the induction of anaesthesia and to laryngoscopy and intubation.

Noninvasive methods of determining cardiac output (by thoracic electrical bioimpedance) and arterial pressure (by intermittent oscillometry) were used to record minute-by-minute changes in heart rate, mean arterial pressure, stroke volume, cardiac output and systemic vascular resistance following induction of general anaesthesia and laryngoscopy and intubation in 60 healthy female patients who were either unpremedicated, or premedicated with temazepam or papaveretum-hyoscine. Anaesthesia was induced with a sleep dose (3-5 mg.kg-1) of thiopentone and maintained with 70% nitrous oxide in oxygen with 0.5-1% enflurane. Tracheal intubation was facilitated by administration of vecuronium 0.1 mg.kg-1. Mean arterial pressure and cardiac output decreased maximally 5 min after induction in all premedication groups by mean estimates of 21-25% and 14-22% respectively. Heart rate increased initially one minute after induction, but decreased to less than the baseline value 5 min after induction. Systemic vascular resistance was unchanged. The stimulus of laryngoscopy and tracheal intubation was accompanied by a significant pressor response and tachycardia one minute after intubation (with mean increases in mean arterial pressure and heart rate of 29-34% and 22-33% respectively). The increase in mean arterial pressure was secondary to an increase in systemic vascular resistance (36-57%), and was accompanied by a decrease in stroke volume (-25 to -31%). These changes were significant in all three groups. Cardiac output decreased only in unpremedicated patients. There were wide variations in the different haemodynamic indices.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Evidence of redistribution of cardiac output in asymmetrical growth retardation.

Thirty-one fetuses with growth retardation were studied by Doppler estimation of the cardiac output from each side of the fetal heart. Asymmetrical growth retardation was diagnosed in 16 fetuses by a head to abdominal circumference ratio above the 95th centile. In the 15 fetuses with symmetrical growth retardation, the distribution of cardiac output was normal. The mean and maximum velocity of blood flow in the pulmonary artery and aorta were similar to values in normal fetuses, and there was a greater calculated output from the right heart than from the left. The right heart flow expressed as a percentage of the combined cardiac output was not statistically significantly different from that in normal fetuses. In contrast, all 16 fetuses with asymmetrical growth retardation had a higher mean and maximum velocity in the aorta than in the pulmonary artery. The calculated volume flow from each side of the heart showed a greater output from the left than the right heart in 15. The right heart flow expressed as a percentage of the combined cardiac output was statistically different from the value in normal fetuses. These findings are consistent with theories of the redistribution of fetal blood flow, where cerebral blood flow is preferentially 'spared'.

Cardiac Output↗
PubMed1990

Cardiac output measured by Doppler echocardiography in patients with aortic prosthetic valves.

Quantification of blood flow is important for the correct interpretation of pressure gradients across prosthetic valves. Cardiac output was assessed simultaneously by Doppler echocardiography and the Fick oxygen method in 20 patients with aortic prosthetic valves. Velocity integral and diameter were measured in the outflow tract close to the valve at a site where the colour flow map showed no interference by valvular velocity. Doppler cardiac output was calculated by multiplying systolic velocity integral with area and heart rate. The variability of the haemodynamic parameters was tested in 10 additional patients. The non-invasive results correlated closely with the invasive results (r = 0.91, SEE 0.6 l min-1). Analysis of variance showed that no bias was introduced when cardiac output was determined by two different observers and on different days. Coefficient of variation for velocity integral, outflow area, heart rate and cardiac output were 9.6%, 7.2%, 6% and 10.8%, respectively. In conclusion, Doppler echocardiography is useful for estimating cardiac output in patients with aortic prosthetic valves.

Aortic Valve↗
PubMed1983

Cardiac output and its distribution through capillaries and A-V shunts in diving seals.

Regional blood flow and cardiac output were determined by distribution of radioactive microspheres injected via catheter into the left ventricle during experimental diving and recovery in juvenile spotted seals (Phoca vitulina largha) and grey seals (Halichoerus grypus). Cardiac output was 9.7 L/min before diving, declined 90% during submersion and increased to 12.1 L/min after 40 s of recovery. Left ventricular myocardial perfusion declined from 179 +/- 24 (21) to 25 +/- 2 (6) ml/min . 100 g at 2 min submersion, and measured 23 +/- 3 (8) after 10 min of submersion. Cerebral cortical flow was reduced from a pre-dive value of 115 +/- 3 (15) to 40 +/- 5 (3) and 49 +/- 6 (3) at 2 and 5 min of diving, respectively, but increased to 253 +/- 14 (4) ml/min . 100 g at 10 min along with elevated PCO2 (84 torr) and lowered pH (7.10) in arterial blood. It remained at that level in recovery. Brain stem perfusion after 10 min submersion was still identical with control, but increased to 275% of control in recovery. Adrenal flow decreased to 34 and 27% of control at 2 and 5 min of diving, respectively. Recovery flow after 10 min of diving was 200% of control. Liver, kidney, fat, skin, and stomach were ischemic throughout the dive. Recovery flow increased slowly in these tissues. Skeletal muscle (M. psoas) was perfused at a low rate. (3 ml/min . 100 g) pre-dive and was ischemic during diving. Recovery muscle perfusion was variable at different sites (from 5 to 105 ml/min . 100 g). Pre-dive pulmonary capillary perfusion was 58 +/- 8 (9) ml/min . 100 g, decreased to 7 +/- 0 (3) ml/min . 100 g min of submersion, and had increased to 50% of pre-dive value after 40 s of recovery from a 10 min dive. Conclusions are: (1) previous information from implanted flow transducers was confirmed, (2) detailed data for discrete tissues elaborate the concept of selective redistribution of cardiac output in diving seals, (3) non-uniform reperfusion contributes to the maintenance of arterial pressure during recovery, and (4) substantial A-V shunting of cardiac output took place in the first 2-5 min of the dive, when total capillary/nutritive flow was low. Late in the dive, however, CO was routed through systemic capillaries mainly in the cerebral circulation and less than 15% through A-V shunts.

Adrenal Glands↗
PubMed1983

Single breath cardiac output--enhanced sampling and analysis techniques.

The single breath method for measuring cardiac output (Q) was enhanced using new computer sampling and analysis techniques. The carbon dioxide (CO2) elimination rate was measured breath by breath using computer integration of expired flow rate and CO2 concentration. The concentration of CO2 in the arterial blood was determined from the CO2 partial pressure at the end of a normal breath. The concentration of CO2 in mixed venous blood was determined with a modification of the single breath method. The variability and relative accuracy of measurement of cardiac output were evaluated using four healthy men who exercised at three work rates from 0.5 L X min-1 (rest) to 2 L X min-1 oxygen consumption (VO2). Repeatability of measurements was assessed by making repeated measurements on one subject at a steady state exercise work rate. The coefficients of variation for repeated measurements made at 0.5 L X min-1 (rest), 1.0 L X min-1 VO2, and 2.0 L X min VO2 were 18.2, 10.5% and 8.8%, respectively. Regression lines relating cardiac output and oxygen consumption from three separate studies, employing the direct Fick method, and the described method were all similar. The probability of a successful breathing maneuver was increased to nearly 100%. Success was defined as a linear regression correlation coefficient (r2), relating instantaneous exchange ratio and CO2 during the breathing maneuver, of greater than 0.9.

Adult↗