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At least 1,351 records · Page 75Linked to original sources
PubMed1996

Application of the flow convergence region method to the determination of stroke volume and cardiac output in patients with mitral stenosis.

OBJECTIVE: This study was undertaken to investigate the feasibility and accuracy of determination of stroke volume and cardiac output by calculating transmitral flow volume using the flow convergence region method in patients with mitral stenosis. PATIENTS AND INTERVENTIONS: Fifty-six patients with rheumatic mitral stenosis were studied using imaging and Doppler echocardiography. Aliasing velocities of 20 to 23 cm/s were used to record the flow vonvergence region proximal to the stenotic mitral orifice. The stroke volume (mL) was calculated by multiplying peak transmitral flow rate which was obtained using an angle-corrected hemispheric flow convergence equation, by transmitral velocity time integral (cm) divided by peak transmitral velocity (cm/s) recorded using continuous wave Doppler method. MAIN RESULTS: Stroke volume calculated using the flow convergence region method was not significantly different from that calculated using aortic Doppler two-dimensional echocardiographic method in 39 patients with pure mitral stenosis (75+/-19 [mean+/-1SD] versus 73+/-19 mL, P=0.12), and from that calculated using pulmonic Doppler two-dimensional echocardiographic method in nine patients with mitral stenosis with associated>2+ aortic regurgitation (77+/-12 versus 75+/-14 mL, P=0.49). No significant difference existed between the cardiac output obtained using the flow convergence region method and that obtained using Fick method in 12 patients with pure mitral stenosis. The stroke volume was overestimated by the flow convergence region method when compared with those obtained using aortic Doppler two-dimensional echocardiographic method in patients with mitral stenosis with associated >2+ mitral regurgitation (123+/-40 versus 67+/-15 mL, P=0.001). CONCLUSIONS: The present study provided an alternative way to calculate the stroke volume and cardiac output in patients with mitral stenosis.

Adult↗
PubMed1979

Distribution of cardiac output in different models of hypertension in the conscious rat.

The distribution of cardiac output was determined by 15 micron radioactive microspheres in all the major organs of spontaneous, DOCA/NaCl and one kidney Goldblatt hypertensive rats and compared to normotensive Wistar rats. Although there were alterations in cardiac output distribution which were characteristic of each model of hypertension significant changes were common to all three were an increased distribution to skeletal muscle with decreases to the lungs, spleen and hepatosplanchnic tissues. The results suggest that alterations in peripheral resistance induced by hypertension are of unequal importance in the different vascular beds with certain vascular resistance changes occurring irrespective of the origin of the hypertension.

Animals↗
PubMed1980

Transcutaneous method of measuring Doppler cardiac output--I. Comparison of transcutaneous and juxta-aortic Doppler velocity signals with catheter and cuff electromagnetic flowmeter measurements in closed and open chest dogs.

Cardiac output values obtained by thermodilution technique in 20 closed and open chest dogs were compared with values obtained by multiplying the integral of Doppler systolic velocity signals of aortic flow in 1 minute by the cross-sectional area of the aortic root. Doppler velocity signals were measured either from immediately outside the proximal aortic wall or from outside the chest wall during (1) the baseline state, (2) after 500 ml of hemorrhage, and (3) after reinfusion, (4) after administration of propranolol, and (5) during infusion of dopamine. In addition, Doppler "stroke volume" waveforms were compared with those obtained by electromagnetic flowmeter. Results showed a close similarity between Doppler signals and electromagnetic waveforms, and a close correlatin between Doppler and thermodilution values for cardiac output except at heart rates exceeding 160 beats/min. The studies showed the transcutaneous Doppler method of measuring cardiac output to be an accurate and reliable technique with application to clinical heart disease.

Animals↗
PubMed1994

Do changes in end-tidal PCO2 quantitatively reflect changes in cardiac output?

In anesthetized patients, acute decreases in cardiac output (CO) are often reflected as decreases in end-tidal CO2 tension (PETCO2), but the quantitative relationship between the changes in CO and the changes in PETCO2 is uncertain. We hypothesize that a quantitative relationship can be demonstrated if timing of the measurements in each episode of hemodynamic perturbation is standardized. In 24 patients undergoing abdominal aortic aneurysm surgery with constant ventilation, we prospectively performed 33 measurements of CO, PETCO2, and CO2 elimination (VECO2) within 10 min of hemodynamic changes. The percent decrease in PETCO2 directly correlated with the percent decrease in CO (slope = 0.33, r2 = 0.82). Also, the percent decrease in VECO2 correlated with the percent decrease in CO similarly (slope = 0.28, r2 = 0.84). The changes in PETCO2 and VECO2 following hemodynamic perturbation were parallel. This finding suggests that decreases in PETCO2 quantitatively reflect the decreases in CO2 elimination.

Aged↗
PubMedDate not supplied

Decreased cardiac output: validation with postoperative heart surgery patients.

This study was done to analyze the association between defining characteristics of decreased cardiac output (DCO) identified by noninvasive methods and the cardiac index (CI) estimated by thermodilution. Two defining characteristics were associated with DCO: decreased peripheral pulse and decreased peripheral perfusion. This study points out the relevance of peripheral circulation assessment in postoperative cardiac surgery patients.

Adult↗
PubMed1982

Respiratory muscle contribution to lactic acidosis in low cardiac output.

The role of the respiratory muscles in the evolution of experimental low cardiac output and lactic acidosis was studied in 2 groups of dogs. One group (6 dogs) was paralyzed and artificially ventilated, and the other (6 dogs) was breathing spontaneously. Shock was induced by cardiac tamponade; cardiac output during shock amounted to 25 to 35% of control values in both groups. All the spontaneously breathing dogs died from ventilatory failure (mean time, 2 h), whereas the artificially ventilated dogs were still alive 3 h after the onset of cardiogenic shock. At any given time after the onset of shock, arterial pH was significantly lower in the spontaneously breathing dogs than in the artificially ventilated ones. This was due to a greater increase in arterial blood lactate in the spontaneously breathing dogs than in the artificially ventilated ones (9.47 +/- 2.7 versus 4.74 +/- 56 mmoles/L at 2 h, respectively). Greater glycogen depletion associated with higher muscle lactate concentrations were found in the respiratory muscles of the spontaneously breathing dogs when compared with that in the artificially ventilated ones. It is concluded that artificial ventilation in cardiogenic shock decreases substantially the severity of lactic acidosis and prolongs survival.

Abdominal Muscles↗
PubMed2004

Continuous monitoring of cardiac output from TCG signals.

Continuous measurement of cardiac output (CO) is an important and difficult measure to obtain in an ambulatory environment. A novel ambulatory monitoring system (LifeShirt, VivoMetrics, Inc., Ventura, CA, USA) with three Inductive Plethysmographic (IP) sensors embedded in a garment, enables continuous monitoring of respiration from the ribcage and abdomen areas, and captures thoracocardiograph (TCG) signals from the thorax at the level of the left ventricle. This TCG signal provides a non-invasive measure of the volumetric contractions of the heart. The raw TCG signal must undergo extensive signal processing and digital filtering to extract a volume curve similar to the ventricular volume curve obtained through echocardiography. Typically the respiratory component has an amplitude of over twenty times that of the stroke volume curve. This investigation compares various signal processing algorithms such as spectral subtraction and adaptive filtering to separate these 2 components, which can occupy the same frequency band. These algorithms make use of the ribcage and abdominal signals to predict the respiratory component within the TCG signal. A dual axis accelerometer that measures posture and levels of activity aids filtering movement artifact. With the addition of a single lead ECG, ensemble averaging is used to smooth artifact in the signal, and CO may be obtained by including a heart rate measure. Additional measures can be derived including left ventricular systolic time intervals such as Pre-ejection period, Peak ejection rate and time to peak ejection rate. The results show that increases and decreases in SV and CO can be measured over time.

Algorithms↗
PubMed2001

[Hemodynamic changes during slow induction of anesthesia using propofol and the effect of cardiac output on the propofol concentration].

This investigation assessed the hemodynamic changes during the slow induction of anesthesia using propofol, and evaluated the effects of cardiac output (CO) and other factors on the hypnotic dose of propofol, the time for hypnosis and the plasma propofol concentration. We studied 26 scheduled surgical patients and induced anesthesia with continuous infusion of propofol at the rate of 15 mg.kg-1.hr-1. The required dose of propofol and time for hypnosis were determined and the plasma concentration of propofol was measured after the administration of propofol 2 mg.kg-1. Cardiac output was determined by dye densitometry using indocyanine green 4 times during induction and CO did not show any significant changes during induction of anesthesia. Multiple linear regression analysis demonstrated that in addition to the age and total body weight, CO determined at achieving hypnosis was significantly related to the plasma concentration of propofol. Cardiac output might affect the pharmacokinetics of propofol during induction of anesthesia.

Adult↗
PubMed1990

Effects of behavioural states on cardiac output in the healthy human fetus at 36-38 weeks of gestation.

Doppler velocity waveforms from atrioventricular valves were recorded in 20 healthy fetuses at 36--38 weeks of gestation during both behavioural states 1F (quiet sleep) and 2F (active sleep). No significant changes were found in the ratios between the velocities during early passive ventricular filling and active ventricular filling (E/A ratios) at the level of both mitral and tricuspid valves when the measurements obtained during states 1F and 2F were compared. Moreover, during state 2F the left ventricular output increased and the right ventricular output decreased, resulting in a marked modification of the right to left cardiac output ratio. Our data suggest a redistribution of cardiac output in favour of the left side of the heart during state 2F.

Blood Circulation↗
PubMed1982

Evaluation of a method for estimating cardiac output from a single breath in humans.

We have modified the single-breath method of Kim et al. (J. Appl. Physiol. 21: 1338-1344, 1966) for estimating cardiac output and arterial and mixed venous carbon dioxide tensions (PCO2). We assessed this using 30 normal subjects and 23 cardiac patients. The procedure was performed satisfactorily in all but two patients. The random errors, from 60 pairs of estimates of cardiac output in normal subjects and 50 pairs in patients, were +/- 12.8 and +/- 19.6% (95% tolerance limits; i.e., coefficient of variation multiplied by 2 for n greater than 50). The systematic error was assessed in 15 patients from comparisons with results obtained by the direct Fick method. There was no significant difference except in two patients with large intracardiac shunts. Mean values of cardiac output by single-breath and direct Fick estimates were 3.80 and 3.83 l/min. Arterial and mixed venous PCO2 were estimated by the single-breath method with random errors of +/- 1.5 and +/- 1.4 Torr, respectively, and no significant systematic errors. We conclude that our modification of the single-breath method is reliable in humans at rest, although the procedures for delivering the breath and processing the data are of critical importance.

Cardiac Output↗
PubMed1996

Comparison of quantitation of left ventricular volume, ejection fraction, and cardiac output in patients with atrial fibrillation by cine magnetic resonance imaging versus invasive measurements.

Currently available invasive and noninvasive techniques for the determination of left ventricular end-diastolic and end-systolic volumes, ejection fraction, and cardiac output are more time-consuming and potentially less accurate in patients with atrial fibrillation (AF) than in those with sinus rhythm. Although magnetic resonance imaging (MRI) can rapidly and accurately measure these variables in patients with sinus rhythm, its ability to do so in subjects with AF is not known. To determine if left ventricular volumes, ejection fraction, and cardiac output can be measured accurately in patients with AF using MRI, 26 subjects (13 women and 13 men, aged 15 to 76 years) in sinus rhythm (n = 13) or AF (n = 13) underwent MRI followed immediately by invasive measurements of these indexes. For those in AF, MRI measurements of left ventricular end-diastolic volume, end-systolic volume, stroke volume, ejection fraction, and cardiac output correlated well with catheterization measurements (r = 0.90, 0.90, 0.95, 0.85, and 0.90, respectively). In addition, the mean difference between MRI and catheterization measurements was similar in subjects with AF and in those with sinus rhythm. Compared with standard invasive measurements, MRI provides an accurate noninvasive determination of left ventricular volumes, ejection fraction, and cardiac output in patients with AF.

Adolescent↗
PubMed1992

Lack of increased cardiac output during hemoglobin hemodilution can be reversed with sodium nitroprusside.

To investigate a possible connection between EDRF or nitric oxide (NO) and the unchanged cardiac output (CO) during hemoglobin-hemodilution we infused nitroprusside (NP) in eight Hb-diluted dogs (Hct approximately 20%). Normal hypotensive doses of NP were not effective and supranormal doses (133.0 micrograms/kg/min) were needed to induce even a modest decrease in mean AoP (approximately 25 mmHg). With these NP doses, cardiac output increased 177%, diastolic AoP (afterload) decreased 30%, while systolic AoP and LVEDP (preload) were unchanged. Heart rate, LV contractility (pressure-volume function) and blood volume were not changed throughout the study. Normally, NP alone decreases both preload and afterload resulting in unchanged CO. In the Hb + NP dogs, CO increased because only afterload decreased suggesting a selective effect of Hb on venous and arterial smooth muscle relaxation. In hemodilution with nonhemoglobin colloids, CO increases primarily because the diluted blood offers less viscous resistance to ventricular ejection. It appears that in order for cardiac output to increases in the presence of Hb, some decrease in arteriolar resistance is needed, presumably to unmask the effects of reduced viscosity. These results suggest the unchanged CO during Hb-dilution is related to a selective effect of Hb on venous and arteriolar nitric oxide (EDRF) function.

Animals↗
PubMed1997

Endomorphin 1 and 2, endogenous ligands for the mu-opioid receptor, decrease cardiac output, and total peripheral resistance in the rat.

Endomorphin 1 and 2 are recently discovered endogenous ligands for the mu-opioid receptor. In the present study, responses to intravenous administration of endomorphin 1 and 2 were investigated in the systemic vascular bed of the rat. Endomorphin 1 and 2 induced dose-related decreases in systemic arterial pressure when injected in doses of 10-100 nmol/kg i.v.. The decreases in systemic arterial pressure in response to endomorphin 1 and 2 were associated with significant decreases in heart rate, cardiac output, and total peripheral resistance. The endogenous ligand for the ORL1 receptor, nociceptin/OFQ had similar effects on systemic arterial pressure, heart rate, cardiac output, and total peripheral resistance in the rat. Injections of isoproterenol (1 microgram/kg i.v.) and calcitonin gene-related peptide (CGRP; 0.3 nmol/kg i.v.), decreased systemic arterial pressure and total peripheral resistance. However these decreases in arterial pressure were associated with increases in heart rate and cardiac output. The results of the present study demonstrate that the endomorphin peptides have significant vasodilator activity in the systemic vascular bed of the rat and show that this response is associated with a decrease in heart rate and cardiac output.

Animals↗
PubMed2003

Cardiac output by femoral arterial thermodilution-calibrated pulse contour analysis during liver transplantation: comparison with pulmonary artery thermodilution.

PURPOSE: The continuous monitoring of the cardiac output during liver transplantation (LT) is an essential part of the intraoperative management of the patient's hemodynamics. To verify the accuracy of a new method based on femoral artery thermodilution-calibrated pulse contour analysis (PCCO) during LT, we compared the technique with the results of an intermittent pulmonary artery thermodilution method (ICO). METHOD: A prospective study included 314 paired cardiac output measurements at 10 sampling times in 35 patients undergoing LT. After initial calibration of the pulse contour analysis, no further recalibrations were performed. Bland and Altman's statistical method, one-way ANOVA, and one sample t tests were used for the analysis of the data. A P<.05 was considered significant. RESULTS: There was a small bias 0.18 L x min(-1) (6.29% from the ICO) for the whole sample of paired measurements, associated with 95% limits of agreement of +/-4.72 (68.89%) L x min(-1). The additional analysis showed comparable biases and limits of agreement for any single time in the study period. The difference PCCO-ICO showed a negative sign for ICO >10 L x min(-1) (P<.001) and a positive sign for ICO <5 L x min(-1) (P<.001). It was greater during infusion of a vasoactive drug (P<.001). CONCLUSION: The pulse contour analysis was found to be an unsatisfactory substitute for intermittent thermodilution measurement of cardiac output during the LT.

Analysis of Variance↗
PubMed1992

The influence of arm position and cardiac output on bolus clearance from the arm.

The importance of arm position and cardiac output on the clearance of a bolus injection from the arm was assessed in 63 patients using technetium-99m. Injections were made in the left arm which was either adducted, abducted or adducted with the forearm flexed over the lower chest. The clearance of isotope was assessed by measuring the amount of radioactivity remaining in the arm at 10 s intervals and calculating it as a fraction of the injected dose. The clearance of Tc-99m was significantly faster and more complete from the abducted arm than from the adducted arm. There was no correlation between clearance and cardiac output.

Arm↗
PubMed1988

Calculating cardiac output from transmitral volume flow using Doppler and M-mode echocardiography.

To simplify transmitral volume flow determination by Doppler echocardiography, a formula for calculating mean mitral valve orifice area using M-mode echocardiography without any 2-dimensional measurements was developed and evaluated in this study. The maximal mitral orifice area was assumed to be circular and its diameter was calculated from the maximal M-mode mitral leaflet separation. The maximal area was multiplied by the mean to maximal anterior mitral leaflet excursion ratio to correct for phasic changes in flow orifice area during ventricular filling. This measurement had a high correlation (r = 0.97, standard error of the estimate + 0.26 cm2) with mean mitral valve orifice area calculated from frame-by-frame analysis of short-axis 2-dimensional echoes in a select group of 10 normal volunteers and 10 patients with cardiomyopathy who had very high quality images of the mitral valve leaflet tips. Cardiac output calculated using the new method for orifice area estimation combined with apex view mitral valve Doppler velocities was then validated in 48 consecutive patients undergoing thermodilution cardiac output determinations with a close correlation between Doppler and thermodilution cardiac output (2.3 to 6.1 liter/min, r = 0.93, standard error of the estimate = 362 ml). The correlation improved when 12 patients with mild mitral insufficiency were excluded (r = 0.95). The M-mode echocardiogram-derived mitral valve orifice method combined with Doppler mitral valve velocities is accurate, easy to perform, has a high success rate and should increase the applicability of Doppler echocardiography for estimation of cardiac output.

Adult↗
PubMed2001

Increased cerebral blood flow and cardiac output following cerebral arterial air embolism in sheep.

1. The effects of cerebral arterial gas embolism on cerebral blood flow and systemic cardiovascular parameters were assessed in anaesthetized sheep. 2. Six sheep received a 2.5 mL injection of air simultaneously into each common carotid artery over 5 s. Mean arterial blood pressure, heart rate, end-tidal carbon dioxide and an ultrasonic Doppler index of cerebral blood flow were monitored continuously. Cardiac output was determined by periodic thermodilution. 3. Intracarotid injection of air produced an immediate drop in mean cerebral blood flow. This drop was transient and mean cerebral blood flow subsequently increased to 151% before declining slowly to baseline. Coincident with the increased cerebral blood flow was a sustained increase in mean cardiac output to 161% of baseline. Mean arterial blood pressure, heart rate and end-tidal carbon dioxide were not significantly altered by the intracarotid injection of air. 4. The increased cardiac output is a pathological response to impact of arterial air bubbles on the brain, possibly the brainstem. The increased cerebral blood flow is probably the result of the increased cardiac output and dilation of cerebral resistance vessels caused by the passage of air bubbles.

Animals↗
PubMed1995

Vascular capacitance and cardiac output in pacing-induced canine models of acute and chronic heart failure.

The relationship between stressed and total blood volume, total vascular capacitance, central blood volume, cardiac output (CO), and pulmonary capillary wedge pressure (Ppcw) was investigated in pacing-induced acute and chronic heart failure. Acute heart failure was induced in anesthetized splenectomized dogs by a volume load (20 mL/kg over 10 min) during rapid right ventricular pacing at 250 beats/min (RRVP) for 60 min. Chronic heart failure was induced by continuous RRVP for 2-6 weeks (average 24 +/- 2 days). Total vascular compliance and capacitance were calculated from the mean circulatory filling pressure (Pmcf) during transient circulatory arrest after acetylcholine at three different circulating volumes. Stressed blood volume was calculated as a product of compliance and Pmcf, with the total blood volume measured by a dye dilution. Central blood volume (CBV) and CO were measured by thermodilution. Central (heart and lung) vascular capacitance was estimated from the plot of Ppcw against CBV. Acute volume loading without RRVP increased capacitance and CO, whereas after volume loading with RRVP, capacitance and CO were unaltered from baseline. Chronic RRVP reduced capacitance and CO. All interventions, volume +/- RRVP or chronic RRVP, increased stressed and central blood volumes and Ppcw. Acute or chronic RRVP reduced central vascular capacitance. Cardiac output was increased when stressed and unstressed blood volumes increased proportionately as during volume loading alone. When CO was reduced and Ppcw increased, as during chronic RRVP or acute RRVP plus a volume load, stressed blood volume was increased and unstressed blood volume was decreased. Thus, interventions that reduced CO and increased Ppcw also increased stressed and reduced unstressed blood volume and total vascular capacitance.

Acute Disease↗