Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cardiac Output”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources
PubMed1988

Baroreflex participation in redistribution of cardiac output at onset of exercise.

The distribution of cardiac output and systemic vascular conductance was measured in five rabbits. Cardiac output was measured by ascending aortic flowmetry and was partitioned according to the distribution of 15-micron radiolabeled microspheres injected into the left atrium. The rabbits were studied under four conditions: at rest and after 20 s of treadmill exercise, both before and approximately 5 min after acute barodenervation of the conscious animal. During exercise in the baroinnervated state, approximately 40% of the increased blood flow to skeletal and cardiac muscle was contributed by diversion from the splanchnic organs, kidneys, systemic arteriovenous anastomoses, and skin. This diversion of blood flow during exercise was absent after arterial barodenervation. We conclude that at the onset of exercise in rabbits the mismatch between cardiac output and the metabolic demands of skeletal and cardiac muscle is accommodated by vasoconstriction in other vascular beds. We suggest that the vasoconstriction in the splanchnic organs and skin may be caused by transient suppression of the reflex effects of arterial baroreceptor input at the onset of exercise.

Animals↗
PubMedDate not supplied

Reconceptualization of the nursing diagnosis decreased cardiac output.

TOPIC: The parameters of the diagnoses decreased cardiac output. PURPOSE: To propose an alternative conceptual structure for cardiac output that links conceptual parameters with clinical and hemodynamic data. SOURCE: Past discussions and research investigations. CONCLUSION: Careful analysis illustrates several diagnoses are contained within cardiac output at differing levels of abstraction. Testing of the model, including linking diagnoses with nursing interventions and outcomes, is suggested.

Cardiac Output, Low↗
PubMed1987

Measurement of cardiac output by electrical impedance plethysmography.

There are many potential applications for cardiac output measurement in clinical and experimental medicine. The most commonly used techniques are invasive procedures, requiring cardiac or arterial catheterization, a disadvantage that has restricted their wider application. Impedance plethysmography has been developed as a non-invasive, beat-by-beat method of cardiac output measurement, which provides an estimate of stroke volume from changes in the electrical impedance of the thorax during cardiac systole. The values for cardiac output obtained by this technique have been extensively compared with values obtained by other methods, both in experimental animals and in the human subject. In the majority of studies high correlation coefficients have been obtained, although impedance plethysmography has tended to give higher absolute values than most other methods. Values for cardiac output obtained by impedance plethysmography are best assessed by comparison with a series of normal values obtained by this technique, rather than with values obtained by other methods. We discuss the results of an investigation of normal cardiac output by impedance plethysmography; theoretical objections to impedance cardiography are considered, and various methods of determining the specific resistivity of blood are reviewed.

Adolescent↗
PubMed1989

First passage radionuclide cardiography for determination of cardiac output: evaluation of an improved method.

A noninvasive method for determination of cardiac output by aid of first passage radionuclide cardiography is presented. As opposed to most other scintigraphic methods, a forward blood flow is measured, even in patients with valvar incompetence. In addition, the technique allows measurement of cardiac output in the presence of cardiac arrhythmias. No geometrical assumptions, corrections for radiation attenuation, loss of tracer, or empirical correction factors due to extracardiac radioactivity are required. We have evaluated the method in 19 patients with various heart diseases by comparison of the radionuclide cardiac outputs with those derived from the thermodilution technique performed simultaneously. Eight patients had valvar incompetence and 2 had cardiac arrhythmias. The mean radionuclide and thermodilution cardiac output values were 5.03 l/min (SD 1.21) and 5.18 l/min (SD 1.09), respectively. The 95% confidence interval for the bias was -0.40 to 0.10 l/min, and correlation analysis demonstrated an excellent correlation between results obtained with the two methods, r = 0.91 (P less than 0.001). This study shows that the improved gamma camera method represents a valid noninvasive technique for determination of cardiac output.

Adult↗
PubMed1983

Noninvasive Doppler determination of cardiac output in man. Clinical validation.

A noninvasive technique for assessing cardiac output (CO) was evaluated by comparing it with thermodilution determinations in patients in the intensive care unit. The new method uses pulsed ultrasound to measure aortic diameter and continuous-wave Doppler ultrasound to obtain aortic blood velocity. An initial study evaluating just the velocity measurement showed that changes of the Doppler index of output (DI) correlated well with those of thermodilution cardiac output (TDCO). Linear regression analysis yielded delta DI = 0.87 delta TDCO + 0.14 (r = 0.83, n = 95). Using a university research instrument these measurements were possible in 54 of 60 patients (90%). A second study using a prototype commercial device incorporated the diameter measurement. Ultrasonic cardiac output (UCO), calculated as the time integral of velocity multiplied by the aortic area, was compared to TDCO. The data, obtained from 45 of 53 patients (85%), are described by the linear regression UCO = 0.95TDCO + 0.38 (r = 0.94, n = 110) over a range of 2-11 l/min. Patients with aortic stenosis, aortic insufficiency or a prosthetic valve have been excluded from the second study due to conditions likely to violate the assumptions upon which the calculation of absolute cardiac output is based. These results indicate that accurate CO can be measured by noninvasive ultrasound in most patients. The technique may be useful for extended CO monitoring in acute care patients and for CO assessment in many other types of patients undergoing diagnostic studies and therapeutic interventions.

Aorta↗
PubMedDate not supplied

Effects of arteriolar vasodilators on hepatic venous compliance and cardiac output in anesthetized cats.

The effects of cumulative doses of seven arteriolar vasodilators were examined in cats anesthetized with pentobarbital. Cardiac output was measured by a thermodilution technique and hepatic venous compliance by plethysmography. All the drugs produced dose-related decreases in total peripheral resistance. Diazoxide, prazosin, and sodium nitroprusside produced no significant changes in hepatic venous compliance or cardiac output. Diazoxide and prazosin produced no change in right atrial pressure, while nitroprusside produced a small fall. It is concluded that these drugs do not alter hepatic venous tone, although nitroprusside may cause a small venodilator effect elsewhere. Epinephrine and dopamine produced marked decreases in hepatic venous compliance and increased cardiac output. This increased cardiac output can be explained on the basis of cardiac stimulation combined with no increase in afterload due to arteriolar vasodilatation and maintenance of preload by venoconstriction. Isoproterenol and hydralazine unexpectedly produced a similar pattern--marked decreases in hepatic venous compliance and increased cardiac output. With hydralazine, these effects preceded arterial hypotension. Possible mechanisms are discussed. These studies support our roterenol and hydralazine produce a beta-receptor-mediated cardiac stimulation and an indirect hepatic venoconstriction, which are not secondary to the hypotension. Possible mechanisms are discussed. These studies support our hypothesis that splanchnic venoconstriction is a necessary factor for the production of large sustained increases in cardiac output. A reduction in afterload per se doesnot increase cardiac output in normal anesthetized cats since a compensatory decrease in preload occurs. It is suggested that afterload influences cardiac output only in situations where the heart is on the flat portion of the Starling function curve.

Animals↗
PubMed1992

Leg vasoconstriction during dynamic exercise with reduced cardiac output.

We evaluated whether a reduction in cardiac output during dynamic exercise results in vasoconstriction of active skeletal muscle vasculature. Nine subjects performed four 8-min bouts of cycling exercise at 71 +/- 12 to 145 +/- 13 W (40-84% maximal oxygen uptake). Exercise was repeated after cardioselective (beta 1) adrenergic blockade (0.2 mg/kg metoprolol iv). Leg blood flow and cardiac output were determined with bolus injections of indocyanine green. Femoral arterial and venous pressures were monitored for measurement of heart rate, mean arterial pressure, and calculation of systemic and leg vascular conductance. Leg norepinephrine spillover was used as an index of regional sympathetic activity. During control, the highest heart rate and cardiac output were 171 +/- 3 beats/min and 18.9 +/- 0.9 l/min, respectively. beta 1-Blockade reduced these values to 147 +/- 6 beats/min and 15.3 +/- 0.9 l/min, respectively (P < 0.001). Mean arterial pressure was lower than control during light exercise with beta 1-blockade but did not differ from control with greater exercise intensities. At the highest work rate in the control condition, leg blood flow and vascular conductance were 5.4 +/- 0.3 l/min and 5.2 +/- 0.3 cl.min-1.mmHg-1, respectively, and were reduced during beta 1-blockade to 4.8 +/- 0.4 l/min (P < 0.01) and 4.6 +/- 0.4 cl.min-1.mmHg-1 (P < 0.05). During the same exercise condition leg norepinephrine spillover increased from a control value of 2.64 +/- 1.16 to 5.62 +/- 2.13 nM/min with beta 1-blockade (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Cardiac output during liver transplantation.

PURPOSE: Measurement of cardiac output is an essential part of anaesthetic practice in patients undergoing major operative procedures. A thermodilution technique, using a pulmonary artery catheter is currently accepted as the gold standard in clinical practice. However its use is associated with several limitations. METHOD: In this prospective randomised controlled study measurement of cardiac output, an oesophageal Doppler monitor (ODM) was compared with the thermodilution technique in 18 patients undergoing orthotopic liver transplantation. Measurements were taken during the three phases of liver transplantation, i) dissection phase (three measurements), ii) anhepatic phase (four) and iii) reperfusion phase (six). RESULTS: There were no differences observed between the two measurements at any of the times studied and a strong correlation was observed (r = 0.714; P < 0.00001). However, when the data was analysed using Bland and Altman analysis, while the mean difference was small (0.07 l.min-1) it was > 2 l.min-1 in one third of measurements recorded i.e., the bias was near zero but the precision was large. No consistent differences were seen using the two methods in individual patients. CONCLUSION: The use of the ODM results in cardiac output measurements which are considerably different from those obtained using thermodilution and its use cannot be recommended in patients undergoing orthotopic liver transplantation.

Adult↗
PubMed2001

The effect of cardiac output changes on end-tidal volatile anaesthetic concentrations.

Cardiac output is a major determinant of the rate of uptake of volatile anaesthetic agents. Theoretical work suggests a 30% change in cardiac output will produce a measurable change in end-tidal volatile agent. We present three patients in whom significant changes in haemodynamic parameters, consistent with a large fall in cardiac output, were accompanied by an increase in end-tidal volatile agent concentrations. The changes in end-tidal volatile agent concentrations were comparable in magnitude but in the opposite direction to the changes in end-tidal CO2. Clinically, an unexplained change in end-tidal concentration of a volatile agent may signify a large change in cardiac output.

Adult↗
PubMed1984

Limitations of thermodilution cardiac output measurements in the rat.

Heat loss from the vascular system could introduce an error in thermodilution cardiac output determinations. Cardiac output measured in the rat via the thermodilution technique following right atrial injection yielded different values (P less than 0.001), depending whether sampling was from the pulmonary artery (460 +/- 31 ml X min-1 X kg-1), right ventricle (311 +/- 19), or thoracic aorta (245 +/- 15). Recirculation errors could not account for the differences. Heat loss from the vascular system was measured from extravascular thermistors within both the thorax and the abdomen. These dilutions were 22-57% in peak height of aortic curves recorded at approximately the same location. Differences in calculated cardiac output between sampling sites could be attributed to rapid heat conduction directly from the right atrium and inferior vena cava to the thoracic aorta with progressive loss of indicator from both the right ventricle and pulmonary artery.

Animals↗
PubMed1975

[On-line monitoring of cardiac output with a new pulse contour computer (author's transl)].

A new pulse contour cardiac output computer, operating from the aortic pressure wave form was tested in cardiac surgical patients. Reference cardiac output was measured by thermal dilution technique. Satisfactory agreements were obtained between the thermal dilution and the COC-pulse-contour cardiac outputs when rapid variations of cardiac output occurred as well as slowly developing changes. The results show that the computation of the stroke volume from the aortic pressure wave form offers a simple, clinically useful method for on-line monitoring of cardiac output in critically ill patients. Possible error sources are discussed.

Aorta↗
PubMed1992

Continuous thermodilution cardiac output measurement in intensive care unit patients.

A new continuous thermodilution cardiac output measurement technique and companion flow-directed pulmonary artery catheter were evaluated in intensive care unit (ICU) patients. Continuous cardiac output was monitored for 6 hours in each patient, and, at selected intervals, a series of bolus thermodilution cardiac output determinations was made and averaged for comparison. A total of 222 data pairs was obtained in 54 patients. The cardiac outputs ranged from 2.8 to 10.8 L/min. The linear regression is represented by the following equation: continuous thermodilution = 0.99 bolus thermodilution + 0.02. The correlation coefficient r was 0.94, the Syx was 0.54. The mean relative error was 0.3%, and the standard deviation of the relative error was 11.5%. The absolute measurement bias was 0.02 L, and the 95% confidence limits were 1.07 and -1.03 L. The results demonstrated that the new continuous thermodilution cardiac output measurement technique provided acceptable accuracy and was considerably easier to use in the clinical situations studied in the ICU.

Cardiac Output↗
PubMed2006

The effect of incomplete acetylene washout on cardiac output measurement using open circuit acetylene uptake.

The open circuit acetylene uptake method is a useful non-invasive means of measuring cardiac output. However, because of accumulation of inhaled acetylene in tissues, the cardiac output uptake is underestimated, if residual acetylene is not allowed to wash out completely in between measurements. We determined the effect of applying a correction factor that estimates mixed venous acetylene concentration from endtidal values to the calculation of cardiac output. This accounts for mixed venous acetylene present during measurements made before complete washout. Six healthy subjects performed steady-state exercise at approximately 30% and 60% of V(O2 max). Cardiac output measurements were made at each exercise intensity using the open circuit acetylene uptake method (inspired [acetylene] approximately 1%), with the first and last measurements having no detectible levels of acetylene in expired gas (reference measurement). Data were also obtained with immediate pre-measurement endtidal concentrations ranging from 3% to 15% of the inspired [acetylene], in random order in between. Oxygen consumption, carbon dioxide production and heart rate did not change significantly during testing at each exercise intensity. Reference cardiac output also did not change significantly and averaged 11.1+/-0.8 L/min at 30% of V(O2 max) and 16.5+/-2.0 L/min at 60% of V(O2 max). Uncorrected cardiac output measurements progressively underestimated cardiac output by 15% at the 3% of inspired endtidal [acetylene] and by over 50% at 15% [acetylene] (p<0.0001). However, when corrected for residual endtidal [acetylene], cardiac outputs were not significantly different from the reference measurements. The results of this study suggest that by accounting for residual endtidal acetylene in mixed venous blood, cardiac output can be accurately measured even when washout of acetylene is incomplete, allowing measurements as often as every 10-15 s.

Acetylene↗
PubMed2000

Non-invasive estimation of cardiac output in critical care patients.

OBJECTIVE: This study was carried out to compare cardiac output measurements determined by thermodilution and by Portapres, a non-invasive system. DESIGN, PATIENTS AND SETTING: Eighty-seven non-invasive blood pressure measurements were performed in 46 patients in our critical care unit utilising the new, non-invasive Portapres system. Cardiac output values were obtained from these blood pressure values using an aortic impedance model and compared to cardiac output values estimated by the thermodilution technique. MEASUREMENTS AND MAIN RESULTS: Statistically significant (p < 0.01) differences (2.3 l/min; limits of agreement +/-5 l/min) were noted between invasive and non-invasive cardiac output measurements. Differences in measured cardiac outputs increased for patients receiving catecholamine therapy, in patients with hemodynamic instability (e.g., sepsis and cardiac insufficiency), in patients with artificial ventilation, in patients with long duration of intensive care, in younger (<60 yr) patients and in women. We found no influence of the body mass index (BMI) on the accuracy of Portapres results. In only one single subgroup, 10 patients with pulmonary diseases, Portapres measurements were not statistically significant different from reference results. CONCLUSIONS: To date, Portapres measurements cannot replace thermodilution cardiac output estimations. Fluctuations of finger arterial perfusion due to hemodynamic instability, hypothermia and catecholamines may be responsible for problems of Portapres use in critically ill patients.

Aged↗
PubMed1973

Effects of splenectomy and beta-adrenoceptor blockade on cardiac output response to acute hypoxemia.

Acute hypoxemia produced by the inhalation of 8% and 5% oxygen increased cardiac output in intact anesthetized dogs by 38% and 62%, respectively. Although practolol, a cardioselective beta-adrenergic blocking agent, reduced the increase in cardiac output in dogs subjected to severe hypoxemia (5% O(2) breathing) from 62% to 43%, it only slightly reduced the cardiac output rise in dogs subjected to moderate hypoxemia (8% O(2) breathing). Splenectomy, on the other hand, abolished the increase in cardiac output produced by moderate hypoxemia except for a small initial rise, but it reduced the increase in cardiac output during severe hypoxemia only to 37%. The entire increase, except for a small initial rise, disappeared only when splenectomized dogs were pretreated with practolol. Sham operation did not affect the cardiac output response to hypoxemia. It is concluded that an intact spleen is required for a significant portion of the increased cardiac output that occurs during both moderate and severe hypoxemia and that catecholamines do not participate in the regulation of cardiac output unless severe hypoxemia occurs.

Adrenergic beta-Antagonists↗
PubMed1997

[Comparison between intraarterial pulsegraphy and thermodilution method for determination of cardiac output during anesthesia and operation in patients undergoing cardiac valve replacement].

Comparison of intraarterial pulsegraphy and standard thermodilution methods for determination of cardiac output (CO) in 14 patients with poor cardiac function following valve replacement operation was performed. The CO, cardiac index (CI) were moderate to high correlated between the two methods before and after valve replacement respectively. The study indicates that intraarterial pulsegraphy provides a continous method of determining CO in patients with poor cardiac function during operation.

Adult↗
PubMed2001

Cardiac output and central distribution of blood flow in the human fetus.

BACKGROUND: The objectives of this study were to establish reference ranges for left and right cardiac output and to investigate blood flow distribution through the foramen ovale, ductus arteriosus, and pulmonary bed in human fetuses. METHODS AND RESULTS: A prospective study was performed in 222 normal fetuses from 13 to 41 weeks of gestation with high-resolution color Doppler ultrasound. Cardiac output and ductal flow were calculated by use of vessel diameter and the time-velocity integral. Pulmonary blood flow was expressed as the difference between right cardiac output and ductal flow. Foramen ovale flow was estimated as the difference between pulmonary flow and left cardiac output. Gestational age-specific reference ranges are given for left, right, and biventricular output and volume of ductal blood flow, showing an exponential increase with gestational age. Median ratio of right to left cardiac output was 1.42 and was not associated with gestational age. Right cardiac output was 59% and left cardiac output was 41% of biventricular cardiac output. Median biventricular cardiac output was estimated to be 425 mL. min(-1). kg(-1) fetal weight. Ductal blood flow was 46%, estimated pulmonary flow was 11%, and estimated foramen ovale flow was 33% of biventricular output. CONCLUSIONS: The study establishes reference ranges for fetal cardiac output and offers insights into the central blood flow distribution in human fetuses from 13 weeks to term. There is a clear right heart dominance. The estimated ratio of pulmonary blood flow to cardiac output is higher than in fetal lamb studies.

Blood Flow Velocity↗
PubMed1998

PEEP decreases oxygenation of the intestinal mucosa despite normalization of cardiac output.

OBJECTIVE: To evaluate if normalization of cardiac output reverses the attenuation of local intracapillary hemoglobin saturation (HbO2) of gastric mucosa by PEEP (positive end-expiratory pressure) during IPPV (intermittent positive pressure ventilation). MATERIALS AND METHODS: Four healthy, chronically instrumented, anesthetized dogs were repeatedly studied (n = 7). Local HbO2 of gastric mucosa was measured continuously by tissue lightguide spectrophotometry and cardiac output (CO) was recorded continuously by means of a precalibrated ultrasonic transit time flowmeter chronically implanted around the pulmonary artery. After obtaining baseline values during IPPV and ZEEP (zero end-expiratory pressure) 15 cmH2O PEEP was added. To compensate the reduction of CO during PEEP ventilation, HES (hydroxyethyl starch 6%) was infused until CO reached baseline values during ZEEP. RESULTS: Despite of unimpaired systemic oxygen saturation, PEEP reduced HbO2 of gastric mucosa from 55.1 +/- 4.2% to 42.1 +/- 4.7% (mean +/- SEM) and CO dropped from 67.7 +/- 4.9 ml.kg-1.min-1 to 33.9 +/- 4.6 ml.kg-1.min-1. Whereas infusion of HES during PEEP ventilation normalized CO to 65.1 +/- 6.2 ml.kg-1.min-1, HbO2 reached only 48.1 +/- 3.3%, a statistically significant improvement compared to HbO2 during PEEP ventilation before HES infusion (p < 0.03, Wilcoxon signed rank test), but still below baseline values (p < 0.04). CONCLUSIONS: Our findings demonstrate that the side effects of PEEP ventilation on cardiac output can be compensated by restoring preload, but normalizing CO did not completely normalize HbO2 of the gastric mucosa. This further emphasizes that global measurements of variables of systemic circulation and oxygenation do not necessarily reflect regional abnormalities of tissue oxygenation. Therefore, in view of the importance of tissue hypoxia especially in the splanchnic region in the pathogenesis of multiple organ failure, monitoring of HbO2 of the intestinal mucosa during PEEP ventilation may be particularly useful in the care of the critically ill patient.

Animals↗