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PubMed1977

Cardiac output and pulmonary wedge pressure. Use for evaluation of fluid replacement in trauma patients.

Cardiac output and pulmonary wedge pressure (PWP) were used to evaluate the end point of fluid resuscitation in 20 patients suffering from multiple trauma and shock. Eleven patients received crystalloid resuscitation and nine patients received colloid resuscitation. Fifteen of 20 patients had an adequate cardiac output at the termination of resuscitation, but but only six of these patients had a PWP above 10 mm Hg. There was no significant correlation between left ventricular stroke work index and PWP in these patients, either at the completion of resuscitation or during the following three days. Five patients did not achieve adequate cardiac output and four of these patients died, suggesting that cardiac output was the most important criterion for adequate resuscitation. If the goal of fluid resuscitation is to achieve an adequate cardiac output, then PWP was not a reliable guide. Furthermore, using both cardiac output and PWP as a guide to fluid resuscitation of our patients, we found that the type of fluid (crystalloid or colloid) for resuscitation did not influence the course of respiratory distress in these patients up to three days following resuscitation.

Adult↗
PubMed1990

Automated non-invasive measurement of cardiac output by the carbon dioxide rebreathing method: comparisons with dye dilution and thermodilution.

The accuracy and reproducibility of indirect measurement of cardiac output at rest by the carbon dioxide rebreathing (indirect Fick) method with an automated respiratory analysis system (Gould 9000IV) were compared with simultaneous measurements made in duplicate by dye dilution and thermodilution in 25 patients having cardiac catheterisation studies. Measurements of cardiac output by the carbon dioxide rebreathing method were not significantly different from those obtained with dye dilution (mean difference -0.3 l/min, SD 0.76, 95% confidence interval -0.7 to 0.1). Thermodilution significantly over-estimated cardiac output by a mean of 2.2 l/min or 39% (SD 1.5, 95% confidence interval 1.6 to 2.8) compared with the carbon dioxide rebreathing method and significantly overestimated cardiac output by 1.9 l/min or 31% (SD 1.2, 95% confidence interval 1.2 to 2.5) compared with dye dilution. The reproducibility of measurements of cardiac output in individual patients was satisfactory with the dye dilution method but was poor with carbon dioxide rebreathing and thermodilution. Indirect measurement of resting cardiac output by the Gould 9000IV automated carbon dioxide rebreathing method is more accurate but the variability inherent with this method requires that multiple measurements be taken for each determination. Measurement of cardiac output by the thermodilution method by a commercially available cardiac output computer was not satisfactory because not only was there considerable variability between repeat measurements but the method also consistently overestimated cardiac output compared with the dye dilution method.

Adult↗
PubMed2001

Monitoring of pacemaker induced changes in cardiac output with inspired to endtidal oxygen difference in paediatric cardiac surgery patients.

METHODS: Fourteen children aged 4-15 months were studied after corrective cardiac surgery. Heart rate was increased by 20% with an external pacemaker. Cardiac output (CO) was measured with thermodilution. Oxygen saturation was measured in systemic artery (SaO2), central vein (ScvcO2) and pulmonary artery (SvO2). Inspiratory to endtidal oxygen difference (FI-ETO2) was measured using a paramagnetic technique. SvO2 was measured continuously using a spectrophotometric technique. RESULTS: CO increased in three patients and decreased in 11 patients during pacing. Regression between DeltaCO and Delta(1/Sa-vO2), Delta(FI-ETO2/Sa-vO2), Delta(FI-ETO2/Sa-cvcO2) showed r=0.70, r=0.76 and r=0.75, respectively. DeltaCO exceeded 10% in 17 of 26 interventions. Changes in FI-ETO2 of equal direction as changes in CO occurred in 12 of these 17 interventions. CONCLUSION: Estimations of CO changes, based on SvO2, can be enhanced if changes in FI-ETO2 are also measured. ScvcO2 instead of SvO2 gives equivalent results. Sudden changes in FI-ETO2 after pacemaker initiation or termination can predict the direction of CO changes.

Carbon Dioxide↗
PubMed1997

Heart rate and cardiac output after atropine in anaesthetised infants and children.

PURPOSE: Heart rate is considered to be a major determinant of cardiac output in infants and small children but the relationships between age, heart rate and cardiac output in humans have never been clearly established. This study was designed to determine the change in cardiac output following atropine iv to anaesthetised infants and small children. METHODS: Following Institutional Ethics Committee approval and written-informed consent, 20 ASA I or II unpremedicated patients aged from 1 to 36 mo were studied. Anaesthesia was induced with 5 mg.kg-1 thiopentone, 2 micrograms.kg-1 fentanyl and maintained with halothane 0.5% in nitrous oxide 66% in oxygen. Vecuronium 0.1 mg.kg-1 was used to provide muscular relaxation. Cardiac output was measured by non-invasive transthoracic blind continuous-wave Doppler echocardiography before and after the administration of 0.02 mg.kg-1 atropine iv. RESULTS: Atropine increased both heart rate and cardiac index by 31.1 +/- 12.8% and 29.4 +/- 17.3% respectively (P < 0.05). The cardiac index before atropine was 5.1 +/- 1.2 L.min-1.m-2 and the increase after atropine varied widely from 1.4 to 52.1%. Although atropine did not alter the overall stroke index the recorded changes ranged from -20.8 to +18.0%. There was no association between age and either cardiac index or % change in cardiac index after atropine. However, there was a positive but weak correlation between percentage change in heart rate and cardiac output (r2 = 0.46). CONCLUSION: Atropine causes a variable increase in cardiac output in infants and children aged between 1 and 36 mo. The change in cardiac output, considering the limits of the transthoracic echocardiography methodology, suggests that this is related to the increase in heart rate but is not dependent of age.

Anesthesia↗
PubMed1984

Comparison of three methods of maintaining a sterile injectate system during cardiac output determinations.

Current technique for determining cardiac output involves multiple manipulations of the injectate system and thereby raises the potential for serious infection. A randomized crossover study was undertaken to compare three methods for determining cardiac outputs, focusing on (1) ability to maintain sterile injectate, (2) operator time, and (3) cost effectiveness. The methods compared were the closed-loop injectate delivery, capped-syringe, and double-bag systems. Forty-five subjects were randomly assigned to one of three methods used, then "crossed over" to an alternate method. This resulted in six different groups: (1) 15 subjects assigned to closed loop first, then crossed over to double bag (eight) or capped syringe (seven), (2) 15 subjects assigned to double bag first, then crossed over to closed loop (seven) or capped syringe (eight), and (3) 15 subjects assigned to capped syringe first, then crossed over to double bag (seven) or closed loop (eight). Quantitative cultures of sample injectates served as indicators of contamination. The Wilcoxon signed rank analysis showed no statistical difference (p greater than 0.9) in patient or catheter characteristics between treatment groups. None of 30 cultures from the closed-loop method yielded bacterial growth, compared to 6 of the 30 cultures positive from each of the other methods (p less than 0.0001). The closed-loop method also required less operator time and was more cost effective than the two alternate methods examined.

Adult↗
PubMed1993

[Measurement of cardiac output by Doppler echocardiography: clinical validation in pediatric patients after open heart surgery].

We compared the cardiac output obtained by pulsed Doppler echocardiography (COPW) with simultaneous thermodilution measurements (COTD) in 13 children for 33 times after open heart surgery. Good correlation (r = 0.84, slope = 1.15) of cardiac output was obtained when direct measurements of aortic diameter during operation were used in the calculations. Cardiac output was overestimated (r = 0.89, slope = 1.42) when 2 DE measurements of aortic diameter were used. Nineteen measurements of 8 VSD patients revealed good correlation (r = 0.89, slope 0.85) using direct measurement of aortic diameter, whereas 14 measurements of TOF patients showed somewhat overestimation of cardiac output (r = 0.90, slope = 1.31). In serial determinations, percent change change in COPW well correlated with COTD (r = 0.75, slope = 1.08). We conclude that accurate cardiac output can be obtained by pulsed Doppler echocardiography after pediatric cardiac surgery by measuring aortic diameter directly in operation room. Accuracy in percent change in cardiac output proved that COPW is useful especially in hemodynamically unstable patients after pediatric cardiac surgery.

Age Factors↗
PubMed1990

Thermodilution cardiac output values obtained by using a centrally placed introducer sheath and right atrial port of a pulmonary artery catheter.

Thermodilution cardiac output measurements obtained using a centrally placed introducer sheath were compared with thermodilution cardiac outputs obtained using the right atrial port of a balloon-tip, flow-directed pulmonary artery catheter in 15 patients with cardiac failure. Cardiac output values were obtained by manually injecting 10 ml of iced, D5W alternately through the introducer sheath and the right atrial port of the flow-directed catheter. Thirty cardiac output readings were obtained in the 15 patients. Cardiac outputs obtained using the right atrial port (CORA) did not differ significantly from cardiac outputs obtained using the introducer sheath (COSP) (5.3 +/- 0.2 vs. 5.2 +/- 0.2 L/min). The correlation between CORA and COSP was significant (r = .94, p less than .0001) and could be described by the formula CORA = 0.33 + 0.96 COSP. We conclude that when the right atrial port of a flow-directed catheter is nonfunctional, a thermodilution cardiac output obtained using a centrally placed introducer sheath offers a reliable alternative.

Adult↗
PubMed1998

Right ventricular overload causes the decrease in cardiac output after nitric oxide synthesis inhibition in endotoxemia.

OBJECTIVE: To determine whether the decrease in cardiac output after nitric oxide synthase inhibition in endotoxemia is due to increased left ventricular afterload or right ventricular afterload. DESIGN: Prospective, randomized, unblinded study. SETTING: Research laboratory at an academic, university medical center. SUBJECTS: Nonanesthetized, sedated, mechanically ventilated pigs. INTERVENTIONS: Pigs were infused with 250 microg/kg of endotoxin over 30 mins. Normal saline was infused to maintain pulmonary artery occlusion pressure (PAOP) at a value not exceeding 1.5 times the baseline value. Left ventricular dimensions and function were studied using echocardiography. Right ventricular volumes and ejection fraction were determined via a rapid thermistor pulmonary artery catheter. We also measured mean arterial pressure (MAP), cardiac output, pulmonary arterial pressure, and calculated pulmonary and systemic resistances. Gastric tonometry was used as an index of gastric mucosal oxygenation and peripheral oxygenation. When MAP had decreased to < or =60 mm Hg or had decreased 30 mm Hg from baseline, nine animals received NG-nitro-L-arginine methyl ester (L-NAME) at 15 mg/kg to restore MAP to baseline. A second group of animals (n = 6) continued to receive normal saline, ensuring that PAOP did not exceed 1.5 times its baseline value. A third group of pigs (n = 5) did not receive endotoxin and served as the time control. In this group, a balloon was used to occlude the descending thoracic aorta and to increase MAP by approximately the same amount as in the L-NAME group. MEASUREMENTS AND MAIN RESULTS: Endotoxin caused an increase in pulmonary arterial pressure and right ventricular volumes, and a decrease in gastric mucosal pH. Cardiac output was maintained in the animals receiving the saline infusion. By 2 hrs, pulmonary arterial pressure had decreased but was still notably higher than baseline. However, by this time, MAP had decreased to < or =60 mm Hg. L-NAME administration restored MAP to its baseline value but resulted in worsening pulmonary hypertension, increased right ventricular volumes, and decreased cardiac output, compared with the saline group. Three animals that received L-NAME died of right ventricular failure. We did not observe any evidence of left ventricular dysfunction with increased left ventricular afterload. Moreover, the restoration of MAP with L-NAME infusion did not correct gastric mucosal acidosis. No changes were noted in the time-control group. Occlusion of the thoracic aorta increased MAP but did not change cardiac output. This finding demonstrates that increases in left ventricular afterload of the magnitude seen with the infusion of L-NAME do not lead to decreases in cardiac output. CONCLUSION: The decrease in cardiac output after nitric oxide synthase inhibition in endotoxemia is due to increased right ventricular afterload and not to left ventricular afterload.

Animals↗
PubMed1986

Effect of methylene blue on cardiac output response to exercise in dogs.

To determine whether the increase in cardiac output during mild to moderate exercise is related to an increase in the tissue redox potential, we compared the responses of cardiac output, total body oxygen consumption, and arterial blood lactate-to-pyruvate ratio (a measure of NADH/NAD) to treadmill exercise between dogs treated with normal saline and those treated with a hydrogen acceptor, new methylene blue. Normal saline was infused into the left atrium in the first group of dogs at a rate of 0.38 ml/min throughout the treadmill exercise (2.5 mph and 5.0 mph on a 6% incline, each for 20 min). In the second group, methylene blue was administered as a loading dose (4 mg/kg) before exercise, followed by a continuous infusion (0.15 mg X kg-1 X min-1) throughout exercise. A similar infusion of methylene blue was given to a third group of dogs without exercise; it reduced the arterial lactate-to-pyruvate ratio from 6.70 +/- 0.35 to 4.12 +/- 0.27 but had no or little effects on cardiac output, heart rate, arterial pressure, and left ventricular dP/dt and (dP/dt)/P. Treadmill exercise doubled cardiac output and increased total body O2 consumption three- to fourfold in the first two groups but increased arterial blood lactate-to-pyruvate ratio only in group 1 (6.0 +/- 0.54 to 9.97 +/- 0.91). The relationship between cardiac output and total body O2 consumption was unaffected by the simultaneous administration of methylene blue during exercise. Groups 1 and 2 also did not differ in their heart rate, left ventricular dP/dt and (dP/dt)/P, and plasma catecholamine responses to exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Contribution of superior vena caval flow to total cardiac output in children. A Doppler echocardiographic study.

BACKGROUND: After a cavopulmonary anastomosis, the superior vena caval flow, by virtue of being the effective pulmonary blood flow, is the most important factor influencing the systemic arterial saturation. Determination of the amount of this blood flow will allow a better understanding of the physiology of the circulation after this anastomosis. The purposes of this study were to determine the volumetric flow in the superior vena cava and to evaluate its contribution to the cardiac output as children grow. METHODS AND RESULTS: Using two-dimensional and Doppler echocardiography, we measured the diameter of and mean flow velocities in the superior venae cavae and the pulmonary arteries of 145 healthy children. We calculated the volumetric flow in each vessel and determined the ratio of superior vena caval flow to total cardiac output. Cardiac output and superior vena caval flow increased with increasing age and body surface area. The superior vena caval flow accounted for 49% of cardiac output in newborn infants. This contribution increased to a maximum of 55% at the age of 2.5 years. Afterward, there was a slow decline in the ratio of superior vena caval-pulmonary arterial flow; it reached the adult value of 35% by 6.6 years of age. CONCLUSIONS: There is a maturational change in the superior vena caval contribution to total cardiac output in children. This is most likely related to somatic growth and changes in body segment proportions. This flow maturation may explain the higher systemic saturation in infants compared with older children after cavopulmonary anastomosis.

Blood Flow Velocity↗
PubMed1981

Cardiac output distribution before and after endotoxin challenge in the rooster.

Cardiac output and its distribution to selected organs was studied using radiolabeled microspheres in unanesthetized, restrained white Leghorn roosters before and 3 h after an Escherichia coli endotoxin challenge. Cardiac output was not significantly altered in either control or endotoxin-treated animals, nor was there a difference in cardiac output between the two groups. Systemic arterial pressure decreased by 37% in the endotoxin group from 187 +/- 14 to 117 +/- 9 mmHg, thus reflecting a marked reduction in total peripheral resistance. The fraction of cardiac output perfusing the heart, adrenals, and liver (hepatic arterial) was not altered by the challenge. Conversely, the percent of total blood flow received by the kidneys, pancreas, and gut (proventriculus and duodenum) was significantly (P less than 0.05) reduced during endotoxemia. Absolute flow to the brain was also decreased. These findings demonstrate that in the rooster endotoxin-induced systemic arterial hypotension is a sufficient stress to cause a redistribution of blood flow, and that the brain in this species (unlike its counterpart in mammals) probably regulates its blood supply passively during periods of hypotension. Conversely, the reduced blood supply to such organs as the gut, pancreas, and kidney following the endotoxin challenge is similar to changes seen in the more commonly studied mammals during experimental endotoxemia.

Animals↗
PubMed1978

Heat and mass transfer of a thermal indicator in pulsatile flow through the cardio-pulmonary system. II. Identification of cardiac output.

Hamilton's celebrated formula for cardiac output measurement is simple but its validity is dependent on several methodologic requirements which are not generally fulfilled, particularly in thermal dilution. A quite different method, based on a physico-mathematical model of the indicator dispersion in the circulation, is proposed. It allows direct derivation of cardiac output once the model's parameters have been identified. Combined deconvolution and least squares procedures are used with truncated data for this identification. Numerical tests and application to clinical observations are presented. Both limitations and possibilities of further developments in estimation of pulsatile flow conditions from TD technique are discussed.

Blood Circulation↗
PubMed2004

Cardiac output by Portapres.

Portapres derives continuous estimates of cardiac output from the peripheral pulse and has the potential to be an extremely valuable physiological and clinical tool. We assessed Portapres estimates of cardiac output in healthy subjects at rest, during maximal treadmill exercise ( n = 8) and during decreases caused by orthostatic stress ( n = 8). Comparison with a rebreathing method indicated that Portapres tended to overestimate cardiac output. The random errors of the estimates (precision), expressed as +/- 2 S.D. of the differences between paired estimates during steady states, ranged between 1.2 and 2.6 litres/min. We conclude that these errors indicate that the method is probably only useful for assessing changes in individual subjects where large changes are anticipated, as during exercise. When smaller changes occur, as during orthostasis, the errors preclude the use of individual subject data and only permit group average data to be examined.

Adult↗
PubMed1979

Measurement of cardiac output by carbon dioxide rebreathing.

Twenty patients were studied on a bicycle ergometer at rest and at varying workloads to compare methods of measuring cardiac output. In nine patients, a comparison of carbon dioxide rebreathing and dye dilution techniques for measuring cardiac output were made. In eleven patients, comparisons between carbon dioxide rebreathing, dye dilution, and direct oxygen Fick techniques were made. The cardiac output measured by carbon dioxide rebreathing was reproducible and compared well with both the dye dilution and direct oxygen Fick. The correlation coefficient for the relationship between carbon dioxide rebreathing and direct oxygen Fick cardiac outputs was 0.80 and between carbon dioxide rebreathing and dye dilution cardiac outputs was 0.75. The relationship between dye dilution and direct oxygen Fick cardiac output was 0.71. The carbon dioxide rebreathing technique is a safe, non-invasive and reproducible method to measure cardiac output. The results compare well with the cardiac output measured by either the direct oxygen Fick or dye dilution technique.

Adult↗
PubMed1988

Thoracic electric bioimpedance measurement of cardiac output in the newborn infant.

To evaluate thoracic electric bioimpedance as a noninvasive method for measuring cardiac output, we compared the bioimpedance measurements with those obtained by means of the thermodilution indicator cardiac output technique in seven preterm and term lambs; we also studied 17 term and preterm infants. Sixty-seven simultaneous bioimpedance and thermodilution cardiac output measurements were obtained in the animals after intravascular volume expansion (saline solution infusion) and contraction (phlebotomy). A significant correlation between the cardiac output measurements by the two methods (0.82; p less than 0.001) was observed. In neonates, the observed cardiac output was 198 +/- 46 ml/kg.min in the preterm infants and 178 +/- 46 ml/kg.min in the term infants. Extrapolating animal data to the neonates, we found the thoracic segment length recommended (the average of 29% of body length and electrode distance) to be accurate. These data indicate that bioimpedance cardiac output measurement (1) is comparable to measurement by the thermodilution indicator technique in the newborn animal and (2) may be suitable for use in infants and children.

Animals↗
PubMed1977

[Effect of dopamine, histamine and acetylcholine on the distribution of cardiac output in the anesthetized rat (author's transl)].

1. The distribution of cardiac output has been studied in rats, using 15 micrometer radioactive microspheres, before and during an I. V. infusion of dopamine, histamine and acetylcholine (3 microgram/kg/min for 3 min). 2. Dopamine decreased the fraction of cardiac output in the spleen (-26%), colon (-23%) and portal vein (-16%) but did not change significantly the flow fraction delivered to the kidneys. 3. Histamine increased the fraction of cardiac output in the stomach (+66%), pancreas (+42%), small intestine (+15%) and decreased it in the colon (-22%) and kidneys (-12%. 4. Acetylcholine reduced the fraction of cardiac output in the colon (-45%), small intestine and spleen (-24%) and increased it in the liver (hepatic artery, +62%). 5. The fractions of microspheres trapped in the lungs were enhanced by histamine (+69%) and acetylcholine (+111%), probably due to an increase in the fraction of cardiac output passing through the peripheral arteriovenous anastomoses.

Acetylcholine↗
PubMed1997

Effects of velocity distribution, diameter measurement and velocity tracing on the accuracy of cardiac output measurement by pulsed Doppler echocardiography in the aortic annulus of pigs.

UNLABELLED: The accuracy of cardiac output measurement by pulsed Doppler echocardiography can be affected by several factors, such as the velocity distribution, the measurement of diameter and the method of tracing the pulsed Doppler flow spectrum. This experimental study was designed to find the most accurate way of measuring cardiac output in consideration of all these factors. In 10 open-chest normal piglets (24 +/- 1 kg), the velocity distribution in the aortic annulus was evaluated using Doppler colour flow mapping. Cardiac output was measured by pulsed Doppler echocardiography in the aortic annulus by a number of different ways and compared to the simultaneous result of the thermodilution method. All measurements were made at baseline, after intravenous injection of esmolol and during infusion of dobutamine. RESULTS: (1) the velocity distribution in the aortic annulus in the piglets was just slightly skewed during all three haemodynamic situations; (2) The in vivo measurements of the diameter of the aortic annulus varied throughout the ejection period, but the average of the three largest diameter measurements was almost identical with the diameter measured in vitro (18.5 +/- 0.3 mm vs. 18.6 +/- 0.2 mm; p = NS); (3) Tracing the maximal velocity of the pulsed Doppler flow spectrum produced a cardiac output that was 18%-21% higher than that measured by the thermodilution method, while tracing the brightest part (modal velocity) of the pulsed Doppler flow spectrum yielded a cardiac output very close to the thermodilution measurement. CONCLUSION: The velocity distribution in the aortic annulus in the piglet has little effect on cardiac output measurement by pulsed Doppler. Using the maximal measurable diameter of the aortic annulus and tracing the brightest part of the pulsed Doppler flow spectrum yielded the cardiac output closest to that measured by the thermodilution method.

Adrenergic beta-Antagonists↗
PubMed1997

Noninvasive measurements of cardiac output in sheep: an improved thermometry method.

In 25 sheep and 5 goats, which were anesthetized, intubated and mechanically ventilated a sudden decrease in the inspired gas humidity was used to cool the lungs. The dynamics of the temperature of expired gas and its relationship to ventilation rate and cardiac output measured by thermodilution were investigated. In six animals minute ventilation was changed at a stable cardiac output and in 14 animals cardiac output was changed by infusion of saline or by bleeding at a constant ventilation. The difference between the blood temperature and the expired gas temperature at a steady state is proportional to minute ventilation and is inversely proportional to the cardiac output. The inverse time constant of the decay of temperature of the expired gas is proportional to the cardiac output and does not depend on ventilation. The lungs function as a natural humidifier of the respiratory gases with an inner heat source from the pulmonary circulation and an outer heat sink to the expired gas. A simple lumped heat capacity model of non-steady state heat exchange in the lungs was developed, which may be used as a basis for the non-invasive method for determining cardiac output. The coefficient of the lung thermal conductivity (KT/(rho WCpW) = 0.156 +/- 0.056) was determined and applied to measure cardiac output in a separate group, designed as a prospective study. When calculations of cardiac output were done based on the lung mass, estimated from the body weight (12 g/kg), bias and precision compared with thermodilution were -0.27 l/min and 0.38 l/min, respectively in 15 animals. Measurements of blood flow by the air thermometry correlated very well with thermodilution cardiac output (r = 0.92). Thermometry of the expired gas is a promising approach to measure the cardiac output non-invasively.

Animals↗