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PubMed1996

Effects of cardiac output on Doppler transmitral and transtricuspid flow velocity patterns in very low birth weight infants.

We studied effects of cardiac output on Doppler transmitral and transtricuspid flow velocities in 24 appropriate for gestational age premature infants. We measured peak flow velocity of early diastole (peak E) and atrial contraction (peak A), ratio of peak flow velocity of early diastole to atrial contraction (peak E/A), total flow velocity-time integral, the first third filling fraction, peak filling rate normalized to stroke volume, and deceleration time (DT). Cardiac output was calculated as the product of the aortic flow velocity-time integral, aortic valve area, and heart rate. The cardiac output increased significantly with advancing gestational age and body weight (r = 0.78 and 0.86, P < 0.01, respectively). With increasing cardiac output, the transmitral as well as transtricuspid peak E, peak E/A, and total flow velocity-time integral increased significantly without any change in the peak filling rate normalized to stroke volume, peak A, and deceleration time. The transmitral as well as transtricuspid peak E did not correlate with the heart rate. Although these results do not establish whether changes in ventricular relaxation process or in cardiac output is responsible for the progressive increase in the peak E and peak E/A. Unchanged peak filling rate normalized to stroke volume of the left and right ventricles suggest that changes in cardiac output with maturity is, in fact, one of the important contributory factors. This evidence should be borne in mind in interpreting ventricular diastolic filling as an index of ventricular diastolic function in premature infants.

Blood Flow Velocity↗
PubMed1985

Cardiac output and end-tidal carbon dioxide.

Previous studies demonstrated selective increases in mixed venous carbon dioxide tension (PvCO2) during CPR in a porcine model of cardiac arrest. This was associated with a decrease in end-tidal carbon dioxide concentration (ETCO2), possibly due to a critical reduction in cardiac output and therefore pulmonary blood flow during CPR. We investigated the relationship between ETco2 and cardiac output before cardiac arrest and during CPR. Observations in 19 minipigs confirmed a high linear correlation between ETco2 and cardiac output. We conclude that the increase in Pvco2 and the concurrent decrease in ETco2 reflect a critical reduction in cardiac output, which reduces alveolar blood flow to the extent that carbon dioxide clearance by the lung fails to keep pace with systemic CO2 production.

Animals↗
PubMed2002

Validation of continuous thermodilution cardiac output in patients implanted with a left ventricular assist device.

OBJECTIVE: To assess the accuracy of a continuous cardiac output (CCO) monitor against an independent, intravascular measurement of flow as can be performed in patients fitted with a left ventricular assist device (LVAD). DESIGN: A prospective cohort study. SETTING: Academic tertiary-care center. PARTICIPANTS: Adult patients (n = 15) presenting for LVAD placement. INTERVENTIONS: Consenting patients presenting for LVAD placement for end-stage cardiac failure were anesthetized, and a CCO pulmonary artery catheter was placed (OptiQ, CCO/SvO(2); Abbott Critical Care, North Chicago, IL). Patients were monitored with transesophageal echocardiography and excluded from analysis if aortic regurgitation was found. Cardiac output was determined using a Q-Vue, CCO/SvO(2) computer with digital readout (Abbott Critical Care, North Chicago, IL). The LVAD was placed in standard fashion during cardiopulmonary bypass. The Thoratec vented electric Heartmate (Thoratec Co, Pleasanton, CA) incorporates an LVAD flow console, which computes LVAD flow within +/- 5% (range, 1.8 to 10 L/min). MEASUREMENTS AND MAIN RESULTS: Cardiac output flow measurements were made from both systems at the following time points: 5 minutes and 30 minutes after protamine administration, at chest closure, and after skin closure. Mean cardiac output for each device did not differ at any time point. Regression analysis (Pearson's) showed acceptable correlation (r(2) = 0.79, p < 0.0001), whereas a bias of 529 mL with limits of agreement of 1,208 mL were shown for CCO measurement compared with LVAD flow. CONCLUSION: The data indicate that the CCO system tends to overestimate cardiac output by approximately 500 mL/min when compared with LVAD flow. Nevertheless, this bias is within the range found by other less-invasive studies done to assess the accuracy of this system and further serves to confirm its relative accuracy.

Cardiac Output↗
PubMed1979

Cardiac output differences in males and females during mild cycle ergometer exercise.

To study sex differences in cardiac output during submaximum exercise, eight male and eight female subjects were matched on max Vo2 (1 min-1 and ml kg-1 min-1). Each subject performed one, eight minute submaximum bicycle ergometer test at 35% of Vo2max (300 kpm min-1). At a steady state mean Vo2 of 0.96 1 min-1, cardiac output was determined. Significant differences between men and women were observed (p less than .05) in cardiac output, stroke volume and (a-v) O2 difference. The males had a lower cardiac output (1.75 1 min-1) and stroke volume (17.2 ml beat-1) and a higher (a-v) O2 difference (2.01 vol %). When these variables were expressed independent of lean body weight the above differences were non-significant. It was suggested that cardiac output differences between the sexes during mild exercise are due, in part, to differences in lean body weight.

Adult↗
PubMed2005

Comparison of arterial pressure waveform analysis with the lithium dilution technique to monitor cardiac output in anesthetized dogs.

OBJECTIVE: To assess agreement between arterial pressure waveform-derived cardiac output (PCO) and lithium dilution cardiac output (LiDCO) systems in measurements of various levels of cardiac output (CO) induced by changes in anesthetic depth and administration of inotropic drugs in dogs. ANIMALS: 6 healthy dogs. PROCEDURE: Dogs were anesthetized on 2 occasions separated by at least 5 days. Inotropic drug administration (dopamine or dobutamine) was randomly assigned in a crossover manner. Following initial calibration of PCO measurements with a LiDCO measurement, 4 randomly assigned treatments were administered to vary CO; subsequently, concurrent pairs of PCO and LiDCO measurements were obtained. Treatments included a light plane of anesthesia, deep plane of anesthesia, continuous infusion of an inotropic drug (rate adjusted to achieve a mean arterial pressure of 65 to 80 mm Hg), and continuous infusion of an inotropic drug (7 microg/kg/min). RESULTS: Significant differences in PCO and LiDCO measurements were found during deep planes of anesthesia and with dopamine infusions but not during the light plane of anesthesia or with dobutamine infusions. The PCO system provided higher CO measurements than the LiDCO system during deep planes of anesthesia but lower CO measurements during dopamine infusions. CONCLUSIONS AND CLINICAL RELEVANCE: The PCO system tracked changes in CO in a similar direction as the LiDCO system. The PCO system provided better agreement with LiDCO measurements over time when hemodynamic conditions were similar to those during initial calibration. Recalibration of the PCO system is recommended when hemodynamic conditions or pressure waveforms are altered appreciably.

Anesthesia, General↗
PubMed2004

The validity of trans-esophageal Doppler ultrasonography as a measure of cardiac output in critically ill adults.

OBJECTIVE: To determine the validity of the esophageal Doppler monitor (EDM) and echo-esophageal Doppler (Echo-ED) in measuring cardiac output in the critically ill. DESIGN: Systematic search of relevant international literature and data synthesis. SEARCH STRATEGY: Literature search (1989-2003) using Ovid interface to Medline, Embase and Cochrane databases aimed at finding studies comparing EDM or Echo-ED cardiac output with that derived from simultaneous pulmonary artery thermodilution (PAC(TD)) with Bland Altman measures of validity. PATIENTS: Critically ill adults in operating departments or intensive care units. DATA SYNTHESIS: Summary validity measures synthesized from Bland Altman analyses included pooled median bias and the median percentage of clinical agreement (PCA) derived from the limits of agreement. MAIN RESULTS: Eleven validation papers for EDM (21 studies) involving 314 patients and 2,400 paired measurements. The pooled median bias for PAC(TD) versus EDM was 0.19 l/min (range -0.69 to 2.00 l/min) for cardiac output (16 studies), and 0.6% (range 0-2.3%) for changes in cardiac output (5 studies). The pooled median percentage of clinical agreement for PAC(TD) versus EDM was 52% (interquartile range 42-69%) for cardiac output and 86% (interquartile range 55-93%) for changes in cardiac output. These differences in PCA were significant ( p=0.03 Mann-Whitney) for bolus PAC(TD) as the clinical "gold standard". We found an insufficient number of studies (2 papers) to assess the validity of Echo-ED. CONCLUSIONS: The esophageal Doppler monitor has high validity (no bias and high clinical agreement with pulmonary artery thermodilution) for monitoring changes in cardiac output.

Adult↗
PubMed2005

Comparison and reliability of two non-invasive acetylene uptake techniques for the measurement of cardiac output.

Comparison and reliability of two non-invasive acetylene uptake techniques for the measurement of cardiac output. Thirteen trained male cyclists performed CO2 rebreathing (CO2RB) at intensities from rest to 200 W, and open-circuit acetylene uptake (OpCirc) and single-breath acetylene uptake (SB) at intensities from rest to 300 W, with all procedures using 50 W increments. Oxygen consumption VO2 cardiac output Q and heart rate (HR), were measured at each stage, and the values for each variable were compared within each intensity to determine reliability of the measuring device. Both the OpCirc and SBs were shown to be reliable measures of cardiac output (r = 0.95 and 0.92, respectively) with decreasing coefficients of variation (CV) as intensity increased, and were similar to published data. The Q-VO2 relationship using the SB diverged from the regression line for OpCirc and CO2RB. Linear regression of the Q--VO2 relationship for CO2RB was y = 6.18 x VO2 + 2.59 for OpCirc was y = 6.12 x VO2 + 2.98 and for SB was y = 5.05 x VO2 + 3.76. The OpCirc and SBs were both shown to be reliable techniques for measuring cardiac output, comparable to previously reported cardiac output measurements, and suitable for use in exercise testing. However, the SB, requiring a constant, slow exhalation rate, made the procedure difficult to perform at higher exercise intensities.

Acetylene↗
PubMed1994

Postural effect on cardiac output, oxygen uptake and lactate during cycle exercise of varying intensity.

Owing to changes in cardiac output, blood volume distribution and the efficacy of the muscle pump, oxygen supply may differ during upright and supine cycle exercise. In the present study we measured, in parallel, circulatory (heart rate, stroke volume, blood pressure) and metabolic parameters (oxygen uptake, lactic acid concentration [la]) during incremental-exercise tests and at constant power levels ranging from mild to severe exercise. In supine position, cardiac output exceeded the upright values by 1.0-1.5 l.min-1 during rest, light ([la] < 2 mmol.l-1) and moderate ([la] = 2-4 mmol.l-1) exercise. At higher exercise intensities the cardiac output in an upright subject approached and eventually slightly exceeded the supine values. For both rest-exercise transitions and large-amplitude steps (delta W > or = 140 W) the cardiac output kinetics was significantly faster in upright cycling. The metabolic parameters (VO2 and [la]) showed no simple relationship to the circulatory data. In light to moderate exercise they were unaffected by body position. Only in severe exercise, when cardiac output differences became minimal, could significant influences be observed: with supine body posture, [la] started to rise earlier and maximal power (delta W = 23 W) and exercise duration (64 s) were significantly reduced. However, the maximal [la] value after exercise was identical in both positions. The present findings generally show advantages of upright cycling only for severe exercise. With lower workloads the less effective muscle pump in the supine position appears to be compensated for by the improved central circulatory conditions and local vasodilatation.

Adult↗
PubMed1990

Role of tricuspid regurgitation and left ventricular damage in the treatment of right ventricular infarction-induced low cardiac output syndrome.

To evaluate, in right ventricular (RV) myocardial infarction, the role of tricuspid regurgitation (TR) and left ventricular (LV) damage and the response to treatment of low cardiac output, 20 patients were prospectively studied. Volume infusion increased cardiac output only slightly (11%, p less than 0.001), despite a dramatic increase in ventricular filling pressures. Dobutamine (4 micrograms.kg-1.min-1) markedly increased cardiac output (24%, p less than 0.001) with a decrease in ventricular filling pressures. In the 5 patients with TR, dobutamine only modestly increased cardiac output (9 vs 26%, p less than 0.001), while stroke index and LV end-diastolic dimensions decreased in comparison (-5 vs 33% and -6 vs 9%, respectively, p less than 0.001). In the absence of TR (n = 15), there was no significant difference in response to volume expansion between patients with normal (n = 7) and depressed LV ejection fraction (n = 8). In contrast, dobutamine, in patients with depressed LV function, induced a greater increase in cardiac output (38 vs 17%, p less than 0.01) and RV ejection fraction (36 vs 12%, p less than 0.05). All patients with RV infarction-induced low cardiac output responded only modestly to volume loading. Dobutamine is particularly efficacious in patients without TR who have depressed LV function by improving RV function and, consequently, LV preload. In the 5 patients with TR, increasing RV contractility failed to improve the forward stroke volume by increasing the regurgitant fraction.

Adult↗
PubMedDate not supplied

Non-invasive ultrasonic cardiac output measurement in intensive care unit.

A non-invasive method for measuring cardiac output utilizing M-mode echography and pulsed Doppler ultrasound is described. Measurements were obtained in 26 of 29 randomly selected, mechanically ventilated patients. These values were compared with simultaneously measured cardiac outputs by thermodilution. There was a statistically significant linear relationship between Cardiac Output measured by Doppler (DCO) and Thermodilution (TDCO): DCO = 0.86 TDCO + 0.29 l/min (r = 0.96, n = 26, SEE = 0.45 l/min) over the range of 1.75-8.5 l/min. DCO had the additional advantage of measuring peak flow velocity and maximal blood flow acceleration during early systole, indices of left ventricular pumping ability. Ultrasonic monitoring of cardiac output may be an important supplement to invasive methods in critical care.

Adult↗
PubMed2006

Epicardial microwave ablation on the beating heart for atrial fibrillation: the dependency of lesion depth on cardiac output.

BACKGROUND: Microwave energy is commonly used on the beating heart to create lesions for the surgical treatment of atrial fibrillation. However, lesion transmurality is likely to depend on several factors including tissue thickness and blood flow. This study was designed to determine the effect of cavitary blood flow on transmurality of acute atrial lesions with the FLEX 10 (Guidant Corporation, Santa Clara, Calif) microwave device. METHODS: Six pigs underwent median sternotomy and were placed on cardiopulmonary bypass. Microwave lesions on the atrium were performed for 60 seconds at 65 Watts at 4 different levels of cardiac output by varying cardiopulmonary bypass flow rates. Cardiac output was measured with a pulmonary artery flow probe. Four additional lesions on 2 animals were done for 120 seconds at 65 Watts with 0.0 to 0.5 L/min cardiac output. The animals were sacrificed, and tissue was stained with 2,3,5-triphenyltetrazolium chloride and sectioned at 5-mm intervals. Lesion depth and width were determined from photomicrographs. RESULTS: Sixty-second lesions were transmural in 90%, 65%, 54%, and 46% of atrial sections at cardiac output of 0.0 to 0.5 L/min, 0.6 to 1.9 L/min, 2.0 to 3.9 L/min, and 4.0 L/min or greater, respectively (P < .001). When ablations were performed for 120 seconds with a cardiac output of 0.0 to 0.5 L/min, 100% of lesions were transmural. Lesion width was also related to cardiac output, with the widest lesions produced when cardiac output was 0.0 to 0.5 L/min. CONCLUSIONS: Acute microwave ablation lesion depth and width are strongly dependent on the magnitude of cardiac output. Transmural lesions can be reliably produced on the porcine heart only while on cardiopulmonary bypass.

Animals↗
PubMed1986

Improvement of cardiac output estimation by the thermodilution method during mechanical ventilation.

The reliability of cardiac output estimation by thermodilution during artificial ventilation was studied in anesthetized pigs at the right side of the heart. The estimates exhibited a cyclic modulation related to the ventilation. The amplitude of the modulation was independent of the level of positive end-expiratory pressure, ventilatory pattern and volemic loading of the animals. However, a non-constant phase relation existed between the ventilatory cycle and the modulation. Single observations at a fixed moment in the ventilatory cycle are therefore not appropriate for estimation of mean cardiac output nor for studying its relative changes. The averaging of estimates spread equally over the ventilatory cycle led to a much larger reduction in the deviation of the averages from the mean cardiac output than an averaging procedure of randomly selected estimates. The accuracy of estimation of mean cardiac output by two estimates equally spread in the ventilatory cycle was equal to the accuracy obtained by averaging five randomly selected estimates. Averaging four estimates, equally spread in the cycle, appeared to be the optimal procedure. For 89% of all averages an accuracy of 5% around the mean was obtained and for 99% an accuracy of +/- 10%.

Anesthesia, General↗
PubMed1991

Diaphragmatic fatigue and its recovery are influenced by cardiac output.

The effects of cardiac output (Qt) on diaphragmatic blood flow (Qdi) and diaphragmatic fatigue and its recovery were studied in dogs. Qdi was estimated by measurement of the left inferior phrenic arterial blood flow (QdiL). There was a significant positive correlation between % Qt and % QdiL. Transdiaphragmatic pressure (Pdi) was significantly smaller in the lowered Qt group than the control at the end of fatigue, and the speed of recovery from the fatigue was also significantly slower in the lowered Qt group. It is concluded that Qt was considered to play an important role in the pathogenesis of diaphragmatic fatigue and its recovery in the mechanically ventilated dogs.

Journal Article↗
PubMed1991

[Selection of correct treatment in patients with low cardiac output after open-heart surgery].

In operations of the open heart inadequate cardiac output can lead to the so-called syndrome of a low cardiac output. The main indicator of cardiac function is the cardiac index. In patients in a critical state reduction of the cardiac index below 1.9 l/min q.m. suggests the presence of this syndrome. The submitted paper deals with the early detection of a low cardiac output which makes it possible to select optimal treatment before clinical signs of failure as well as further complications develop. The submitted paper deals with a group of 115 operated patients incl. 53 operated on account of IHD and 62 on account of rheumatic heart disease. Treatment was according to haemodynamic values divided into four groups: 1. Insurance of an optimal intravascular volume without pharmacological support, 2. pharmacological support of vasodilatating agents (nitroglycerine, sodium nitroprusside), 3. positive inotropic support by dobutamine, 4. support by a combination of vasodilatating agents and positive inotropic pharmaceutical preparations (dobutamine, dopamine). The favourable effect of treatment in the above groups is apparent already after four hours, and after 20 hours the investigated values shift to an optimal zone. The authors emphasize the high diagnostic value of comprehensive extensive monitoring which influences and controls therapy by retrospective informations.

Cardiac Output, Low↗
PubMed1988

Cardiac output and O2 consumption during inspiratory threshold loaded breathing.

In this study, noninvasive measurements of cardiac output and O2 consumption were performed to estimate the blood flow to and efficiency of the respiratory muscles that are used in elevated inspiratory work loads. Five subjects were studied for 4.5 min at a respiratory rate of 18 breaths/min and a duty cycle of 0.5. Studies were performed at rest without added respiratory loads and at elevated inspiratory work loads with the use of an inspiratory valve that permitted flow only when a threshold pressure was maintained. Cardiac output and O2 consumption were calculated using a rebreathing technique. Respiratory muscle blood flow and O2 consumption were estimated as the difference between resting and loaded breathing. Work of breathing was calculated by integrating the product of mouth pressure and volume. Increases in cardiac output and O2 consumption in response of 4.5 min loaded breathing averaged 1.84 l/min and 108 ml/min, respectively. No increases were seen in response to 20-s loaded breathing. In a separate series of experiments on four subjects, though, cardiac output increased for the first 2 min then leveled off. These results indicate that the increase in cardiac output was a metabolic effect of the increased work load and was not caused primarily by the influence of the highly negative intrathoracic pressure on venous return. Efficiency of the respiratory muscles during inspiratory threshold loading averaged 5.9%, which was similar to measurements of efficiency of respiratory muscles using whole-body O2 consumption that have been reported previously in humans and in dogs.

Adult↗
PubMed1990

Comparison of a modified Fick method with thermodilution for determining cardiac output in critically ill patients on mechanical ventilation.

We compared a modified Fick method for measuring cardiac output against the thermodilution method in 11 critically-ill patients on mechanical ventilation. Oxygen consumption (VO2) was calculated indirectly, by measuring the carbon dioxide elimination (VCO2) during steady state and by assuming an average respiratory quotient of 0.9. For a total of 129 measurements, the mean difference in cardiac output between both methods was 0.03 +/- 1.3 l/min (95% confidence interval, -0.19 to 0.25 l/min, p = 0.7) standard deviation, with the largest differences being measured in the low cardiac output range (less than 5 l/min). No statistically significant difference was found between the cardiac output values obtained with either method. These data showed a good correlation between the two methods and suggest that the modified Fick method may be useful in determining cardiac output in seriously ill patients on mechanical ventilation not requiring pulmonary arterial catheterisation, or where facilities for undertaking metabolic measurements are not available.

Adult↗
PubMed2006

Evaluation of a noninvasive cardiac output monitor in mechanically ventilated children.

OBJECTIVE: To compare measurements of cardiac output (CO) and cardiac index (CI) obtained by a recently developed noninvasive continuous cardiac output system, NICO (CONICO), and transthoracic Doppler echocardiography (COTTE) in mechanically ventilated children. DESIGN AND SETTING: Prospective study in a university-affiliated tertiary pediatric intensive care unit. PATIENTS: A total of 21 mechanically ventilated children, weighing >15 kg, in stable respiratory and hemodynamic condition. MEASUREMENTS: Sets of three successive measurements of CO with the NICO system and transthoracic Doppler echocardiography were obtained. Bland-Altman analysis was used to compare the agreement between the two methods. RESULTS: The mean +/- sd CO values were 4.06 +/- 1.43 L/min for CONICO and 4.67 +/- 1.78 L/min for COTTE. Bias +/- sd between the two methods was -0.61 +/- 0.94 L/min. The variability of the difference between the two methods increased as the magnitude of the CO measurement increased. Similar results were obtained for cardiac index: 4.01 +/- 1.40 L.min.m for CINICO and 4.59 +/- 1.48 L.min.m for CITTE. Bland-Altman analysis revealed a nonuniform relationship between CI difference and the magnitude (y = -0.299 - 0.0655 x mean). The variability of the differences did not increase as the magnitude of the CO measurement increased (sd of estimate was 0.827 L.min.m). With both CONICO and CINICO, each measurement was highly repeatable, with coefficient of variation of only 2.88% +/- 2.31%. Repeatability with Doppler echocardiography was 7.02% +/- 4.33%. CONCLUSIONS: The NICO system is a new device that measures CO easily and automatically in mechanically ventilated children weighing >15 kg. CO values obtained with this technique were in agreement with those obtained with Doppler echocardiography in children in respiratory and hemodynamic stable condition. The NICO system needs further investigation in children in unstable respiratory and hemodynamic condition.

Adolescent↗