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PubMed1977

[Simultaneous measurement of cardiac output by indium 113 m detected externally and by dye dilution of indocyanine green].

The cardiac output of 11 patients was measured by a method of dilution of a short-life radio-isotope, and compared with measurements obtained simultaneously by a dye dilution technique. After sudden intravenous injection of siderophilin (transferrin) labelled by Indium 113 m, the precoridal radioactivity was measured by a single panel detector probe. In 9 patients these measurements were carried out twice with a 15 minute interval. The correlation coefficient between the two methods was 0.884 for 20 measurements, and 0.939 for the first 11 measurements. The reproducibility of these measurements was comparable for the two techniques. The radio-isotope method of measuring cardiac output, which can be carried out at the bedside, is a simple, reliable and reproducible technique.

Cardiac Output↗
PubMed2001

Noninvasive cardiac output by partial CO2 rebreathing after severe chest trauma.

BACKGROUND: In multiple trauma patients, early continuous cardiac output (CCO) monitoring is frequently desired but is difficult to routinely employ in most emergency departments because it requires invasive procedures. Recently, a noninvasive cardiac output (NICO) technique based on the Fick principle and partial CO2 rebreathing has shown promise under a variety of conditions. Since this method has not been tested after lung damage, we evaluated its utility in a clinically relevant model. METHODS: Anesthetized, ventilated swine (n = 11, 35-45 kg) received a unilateral blunt trauma via a captive bolt gun followed by a 25% hemorrhage. After 60 min of shock, crystalloid resuscitation was given as needed to maintain heart rate < 100 beats/min and mean arterial pressure > 70 mm Hg. Standard CCO by thermodilution (Baxter Vigilance, Irvine, CA) was compared with NICO (Novametrix Medical Systems Inc., Wallingford, CT) for 8 hr. RESULTS: The severity of the injury is reflected by seven deaths (average survival time = 4.25 hr). Trauma increased dead space ventilation (19%), airway resistance (30%), and lactate (3.2 mmol/L), and decreased dynamic compliance (48%) and Pao2/Fio2 (54%). In these extreme conditions, the time course and magnitude of change of CCO and NICO were superimposed. Bland-Altman analysis reveal a bias and precision of 0.01 +/- 0.69 liters/min. The linear relationship between individual CCO and NICO values was significant (p < 0.0001) and was described by the equation NICO = (0.74 +/- 0.1)CCO + (0.65 +/- 0.16 liters/min) but the correlation coefficient (r2 = 0.541) was relatively low. The cause for the low correlation could not be attributed to increased pulmonary shunt, venous desaturation, anemia, hypercapnia, increased dead space ventilation, or hyperlactacidemia. CONCLUSION: NICO correlated with thermodilution CCO, but underestimated this standard by 26% in extreme laboratory conditions of trauma-induced cardiopulmonary dysfunction; 95% of the NICO values fall within 1.38 liters/min of CCO; and with further improvements, NICO may be useful in multiple trauma patients requiring emergency intubation during initial assessment and workup.

Animals↗
PubMed1997

Estimation of cardiac output by noninvasive echocardiographic techniques in the critically ill subject.

We evaluated the accuracy of cardiac output estimations by three transthoracic echocardiographic techniques in critically ill subjects. This study was a prospective comparison study carried out in a general intensive care unit of a teaching hospital. The subjects had a broad range of diagnoses including pulmonary embolus, cardiogenic shock, septic shock, Legionnaire's disease and perioperative myocardial infarction. All patients requiring pulmonary artery catheterization underwent echocardiographic cardiac assessment with comparison of findings to those obtained by thermodilution techniques. Nineteen studies on eighteen patients were performed, with cardiac output calculated by the two-chamber Simpson's, four-chamber Simpson's, and left ventricular outflow tract (LVOT) Doppler methods. Acceptable data was obtained in those patients without mitral regurgitation. There was good correlation between the thermodilution technique and Simpson's two-chamber method (r = 0.91), but less so with the Simpson's four-chamber method (r = 0.77). All studies were included in the LVOT Doppler method with a good correlation (r = 0.94). A plot of differences between methods using the Bland and Altman statistical method indicated that only the LVOT Doppler method demonstrated acceptable agreement with a mean of 0.2 litres/minute, standard deviation of 0.82 litres/minute and 95% limits of agreement of -1.5 to +1.9 litres/minute. We concluded that the LVOT Doppler method was the only one which demonstrated acceptable agreement between the thermodilution method and echocardiographic techniques in all critically ill patients studied.

Adolescent↗
PubMed1984

Application of second-order polynomial equations to the study of pharmacodynamic interactions: the effect of flecainide acetate and propranolol on cardiac output and vascular resistance.

We have examined the analysis of pharmacodynamic data in normal subjects receiving propranolol, flecainide or the two together. We find that a second-order polynomial describes accurately the response of the left ventricular ejection fraction, cardiac output and vascular resistance of the subjects to these drugs. Both single dose and multiple doses of propranolol (80 mg 3 times a day) decreased the left ventricular ejection fraction and cardiac output, but increased the vascular resistance. On the other hand, single and multiple doses of flecainide (200 mg twice a day) decreased the left ventricular ejection fraction but did not affect either the cardiac output or vascular resistance. These data demonstrate the power of the polynomial formulation in analyzing pharmacodynamic data.

Adult↗
PubMed2006

A pilot assessment of the FloTrac cardiac output monitoring system.

OBJECTIVE: To compare measurement of cardiac output (CO) by means of the FloTrac CO monitor with the pulmonary artery catheter (PAC). DESIGN: Prospective observational study. SETTING: Intensive care unit of a tertiary hospital. PATIENTS: Six post-operative cardiac surgery patients with existing arterial cannulas and PACs. INTERVENTIONS: Attachment of the FloTrac CO monitor and transducer to an existing arterial cannula. Simultaneous measurements of CO, indexed to body surface area (cardiac index, CI) by the FloTrac CO monitor and by either a bolus thermodilution or continuous CO PAC. Statistical analysis of observations. MEASUREMENTS AND RESULTS: We performed CO measurements in six patients every 1-4 h after cardiac surgery. Comparison of all measurements showed a limited correlation for CI with the two devices (r (2)=0.1218, bias=0.21, 95% limits of agreement -0.81, 1.23). CI measurements obtained with the intermittent bolus PAC had better correlation with the FloTrac CI values (r (2) = 0.2693, bias=-0.0057, 95% limits of agreement -1.2042, 1.1929) than did those obtained with the continuous CO PAC (r (2)=0.0557, bias=0.2436, 95% limits of agreement -0.7350, 1.2222). When analysed according to heart rhythm, CI values measured during atrial pacing showed the best correlation (r (2)=0.377, bias=-0.0244, 95% limits of agreement -0.5226, 0.5714). CONCLUSIONS: CO measurements obtained using the FloTrac CO monitor show a limited correlation with those acquired using the PAC, relatively wide limits of agreement but no clear bias. Further evaluation is required before this device can be recommended for use in the clinical setting.

Aged, 80 and over↗
PubMedDate not supplied

Determination of cardiac output and of transcapillary fluid exchange by continuous recording of blood density.

We have tested the application of the continuous measurement of the density of the arterial blood for the calculation of the cardiac output and for the determination of the transcapillary fluid exchange. The density of arterial blood was continuously recorded in anesthetized dogs with a mechanical oscillator device (DMA 602 MW built by A. Paar KG, Graz). The time resolution of this device is less than 1 sec, the accuracy is 10(-6) g/ml. Simultaneously the arterial blood temperature was recorded with a thermistor probe. The intravenous injection of isotonic solutions yields temperature and density transients which are of a similar shape and proportional to the injected volume in amplitude. There is a good agreement between the cardiac output calculated from thermodilution transients and from density dilution transients. The injection of hypertonic solutions, e.g. 5% NaCl, 20% mannit or 14.4% urea, into a vein yields arterial density dilution transients which show marked differences and very characteristic features. They can be explained by the assumption of osmotic fluid shifts in the microcirculation of the lung. During the transient of a bolus of hypertonic NaCl or mannit, a transcapillary influx of about 0.170 X 10(-3) ml/sec per mosmols/l and per g wet tissue weight is generated. The effect of hypertonic urea is less by a factor of about 1/2, which is in agreement with the fact that urea diffuses rapidly into the erythrocytes. We conclude that the method of density dilution allows to record and quantify cardiac output and osmotic fluid shifts through the microcirculation of the lung of intact dogs.

Animals↗
PubMed1981

Instrumentation for measuring cardiac output by direct Fick method during liquid ventilation.

A closed-circuit fluorocarbon oxygenation system was designed and incorporated into an existing liquid breathing system (LBS) to allow measurement of an animal's oxygen consumption during liquid ventilation. This enabled simultaneous determination of cardiac output by the direct Fick method. A series of seven in-vivo experiments were conducted in which the oxygen consumption and cardiac output of adult cats (2.3 +/- 0.1 kg body wt SEM) were measured during both spontaneous gas breathing (Fio2 = 0.80 in the control animals) and fluorocarbon liquid (FC-80) ventilation using the LBS. On conversion to liquid ventilation, cardiac output and oxygen consumption were found to decrease significantly, by 40% (P less than 0.02) and 18.6% (P less than 0.05), respectively, from control values for gas breathing. Use of the closed-loop fluorocarbon oxygenation system provided for total recovery of vaporized fluorocarbon (greater than 750 ml/h) and of oxygen (18 liter/min STPD), which were otherwise discarded in previous experiments with liquid ventilation.

Animals↗
PubMed1991

Cardiac output during exercise in paraplegic subjects.

The purpose of this study was to measure the cardiac output using the CO2 rebreathing method during submaximal and maximal arm cranking exercise in six male paraplegic subjects with a high level of spinal cord injury (HP). They were compared with eight able bodied subjects (AB) who were not trained in arm exercise. Maximal O2 consumption (VO2max) was lower in HP (1.11.min, SD 0.1; 17.5 ml.min-1.kg-1, SD 4) than in AB (2.5 l.min-1, SD 0.6; 36.7 ml.min-1.kg, SD 10.7). Maximal cardiac output was similar in the groups (HP, 14 l.min-1, SD 2.6; AB, 16.8 l.min-1, SD 4). The same result was obtained for maximal heart rate (fc,max) (HP, 175 beats.min-1, SD 18; AB, 187 beats.min-1, SD 16) and the maximal stroke volume (HP, 82 ml, SD 13; AB, 91 ml, SD 27). The slopes of the relationship fc/VO2 were higher in HP than AB (P less than 0.025) but when expressed as a %VO2max there were no differences. The results suggest a major alteration of oxygen transport capacity to active muscle mass in paraplegics due to changes in vasomotor regulation below the level of the lesion.

Adult↗
PubMed1980

An effect of hypothalamic stimulation on cardiac output in the rabbit.

Electrical stimulation of a discrete region of the rabbit brainstem, in the lateral hypothalamic area near the mammillothalamic tract, caused an increase in arterial blood pressure accompanied by bradycardia in anaesthetized animals. The cardiac output, measured by a thermodilution technique, was found to fall when the stimulus strength was great enough to evoke strong bradycardia. Threshold current for this effect varied in different animals in the range: 50-350 microA (1 msec pulse duration and 60 pulses/sec repetition rate). Bilateral vagotomy eliminated almost all the negative chronotropic effects of hypothalamic stimulation, but reversed only about one-third of the fall in cardiac output during strong stimulation. It is suggested that negative chronotropic, and possibly inotropic, vagal effects on the heart play a relatively minor role in reducing cardiac output. The major factor in causing output to fall may be left ventricular overload during the widespread peripheral vasoconstriction that accompanies stimulation of this region of the rabbit hypothalamus.

Animals↗
PubMed2007

Semi-invasive monitoring of cardiac output by a new device using arterial pressure waveform analysis: a comparison with intermittent pulmonary artery thermodilution in patients undergoing cardiac surgery.

BACKGROUND: Thermodilution technique using a pulmonary artery catheter (PAC) is a widely used method to determine cardiac output (CO). It is increasingly criticized because of its invasiveness and its unclear risk-benefit ratio. Thus, less invasive techniques for measuring CO are highly desirable. We compared a new, semi-invasive device (FloTrac/Vigileo) using arterial pressure waveform analysis for CO measurement in patients undergoing cardiac surgery with bolus thermodilution measurements. METHODS: Forty patients undergoing coronary artery bypass grafting or valve repair were enrolled. A PAC was inserted and routine radial arterial access was used for semi-invasive determination of CO with the Vigileo. CO was measured simultaneously by bolus thermodilution and the Vigileo technique after induction of anaesthesia (T1), before cardiopulmonary bypass (CPB) (T2), after CPB (T3), after sternal closure (T4), on arrival in the intensive care unit (ICU) (T5), and 4 h (T6), 8 h (T7), and 24 h after surgery (T8). CO was indexed to the body surface area (cardiac index, CI). RESULTS: A total of 244 pairs of CI measurements were analysed. Bias and precision (1.96 sd of the bias) were 0.46 litre min(-1) m(-2) and +/- 1.15 litre min(-1) m(-2) (r = 0.53) resulting in an overall percentage error of 46%. Subgroup analysis revealed a percentage error of 51% for data pairs obtained intraoperatively (T1-T4), 42% in ICU (T5-T8), and 56% for values obtained during low CI (T1-T8). CONCLUSIONS: In cardiac surgery patients, CO measured by a new semi-invasive arterial pressure waveform analysis device showed only moderate agreement with intermittent pulmonary artery thermodilution measurement.

Adult↗
PubMed1999

Beneficial effects of exercise training in heart failure patients with low cardiac output response to exercise - a comparison of two training models.

BACKGROUND: Exercise capacity of patients with chronic heart failure (CHF) correlates poorly with estimates of cardiac function. Yet, it has been suggested that only patients without severely impaired cardiac output (CO) benefit from exercise training. Comparisons of different training models have not been made in the same study. AIMS: To evaluate whether the response to different training models diverges according to the cardiac output response to exercise in patients with chronic heart failure. METHODS: Sixteen CHF patients (63 +/- 11 years) with an ejection fraction of 30 +/- 11% underwent a baseline cardiopulmonary exercise test, right heart catheterization and leg muscle biopsy. Cardiac output (CO) response to exercise was defined as the ratio between CO increase and the increase in oxygen uptake (CO response index) during exercise. Patients were randomized into two training regimens, differing with regard to active muscle mass, i.e. whole body and one-legged exercise. RESULTS: Baseline exercise capacity expressed as W kg-1 correlated with the CO response index (r = 0.51, P < 0.05). Exercise capacity on the cycle ergometer increased in both groups but more in the one-legged than in the two-legged training group (P < 0.05). The improvement in exercise capacity did not correlate with base-line exercise capacity. It correlated with CO response index in the one-legged (r = 0.75, P < 0.01) but not in the two-legged training group. CO response index correlated negatively with the pulmonary capillary wedge pressure at peak exercise (r = - 0.60, P < 0.05). The increase in leg muscle citrate synthase activity after training correlated negatively with the baseline CO response index (r = - 0. 50, P < 0.05). CONCLUSIONS: The improvement of exercise capacity after one-legged training correlates with the CO increase in relation to the O2 uptake before training. In patients with low CO response, individualization of the exercise regimen is needed and the benefits of training a limited muscle mass at a time deserve further study.

Adult↗
PubMed1985

Analysis of factors affecting the variability of Fick versus indicator dilution measurements of cardiac output.

This study was performed to assess the relation between Fick and indicator dilution measurements of cardiac output (CO) in a large number of subjects and to evaluate this relation in patients with a low CO, a high CO, and left-sided cardiac regurgitation. In 808 patients (428 men, 380 women, mean age 50 +/- 11), CO was measured by Fick and either thermodilution (right atrium to pulmonary artery)(n = 252) or indocyanine green dye ("dye")(pulmonary artery to systemic artery)(n = 556) within 10 minutes of each other. There was excellent agreement between Fick and both thermodilution and dye. The difference between Fick and indicator dilution measurements was 9 +/- 9%; it was 10% or less in 67% and 20% or less in 91% of patients. The disparity between Fick and indicator dilution measurements was increased in patients with a low CO (less than 2 liters/min/m2)(n = 152) (difference 14 +/- 11%, p less than 0.001) and those with aortic or mitral regurgitation (n = 83) (difference 13 +/- 11%, p less than 0.001). In these groups, the disparity between Fick and thermodilution measurements was not exaggerated, but the disparity between Fick and dye measurements was greater. Thus, although there is excellent agreement between Fick and both thermodilution and dye measurements of CO, thermodilution is preferable to dye in patients with a low CO and those with aortic or mitral regurgitation.

Adolescent↗
PubMed1984

[Determination of cardiac output by thoracic electric impedance: comparison with thermodilution].

When an alternating current of high frequency is applied to the thorax, the first derivative of the impedance (dZ/dt) is affected by the cardiac cycle, resulting in a characteristic wave form. The maximum negative of this wave occurring during systole together with the length of ejection time (VET), the blood resistivity, the basal impedance (ZO) and the distance between the inner detecting electrodes (L) makes it possible to calculate stroke volume (SV) and related parameters, as cardiac output (CO) and cardiac index (Cl) by a formula developed by Kubicek. Thoracic electrical impedance has been proposed as a non invasive technique to evaluate cardiac emodinamics. In the present study we have evaluated thoracic electrical impedance by comparing it with thermodilution, simultaneously performed in 21 catheterized patients. Reproducibility was assessed by comparing Cl measured several times in the same patient during ten minutes of rest in the supine position: coefficient of variation, expressed as CV = SD/m X 100 was 8,5 +/- 4,2% and 9,4 +/- 3,2% (p = NS) for thermodilution and thoracic electrical impedance respectively. Cl values obtained by both methods correlated well, with little scatter either baseline (r = 0,784, n = 40, p less than 0,001), either after an handgrip manoeuvre (r = 0,629, n = 15, p less than 0,05). This degree of correlation is similar to that observed comparing invasive techniques (Fick, thermodilution, dye dilution) either among them, or with noninvasive methods (echocardiography, gated equilibrium blood pool scintigraphy and ultrasonic Doppler).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Longitudinal trends in left ventricular cardiac output in healthy infants in the first year of life.

We studied left ventricular (LV) cardiac output as estimated by ascending aorta blood flow (QAo) longitudinally in 31 healthy infants from birth through the first year of life using noninvasive pulsed Doppler ultrasound technique. The temporal mean ascending aortic blood flow velocity (VAo) was measured with a 5-MHz pulsed Doppler velocimeter and on line integration system. Ascending aortic cross-sectional area (AAo) was determined using M-mode echography. Ascending aortic blood flow was calculated as QAo = VAo X AAo and was corrected to body weight (BW) in kilograms or body surface area (BSA) in meters squared. Mean ascending aortic flow velocity (VAo) remained relatively constant over the first year, averaging 20.5 +/- 3.4 cm/sec (+/- SD). Changes in AAo over time correlated strongly with changes in BW or BSA (r = 0.99). Therefore, changes in QAo correlated strongly with changes in AAo, BW, and BSA (r = 0.99). LV cardiac output corrected for body weight or BSA remained relatively constant throughout the first year, mean values ranging from 180-226 ml/min/kg or 3.06-3.76 L/min/m2 and averaging 204 +/- 45 ml/min/kg or 3.48 +/- 0.74 L/min/m2. A similar strong correlation was seen between serial changes in LV stroke volume and changes in BW or BSA (r = 0.99).

Aging↗
PubMed1997

Comparison of indirect calorimetry and thermodilution cardiac output measurement in children.

We validated experimentally the ability of hood indirect calorimetry to measure accurately VO2. For this purpose we compared cardiac output calculated from the Fick equation Q = VO2/(Ca(O2) - CV(O2)), in which VO2 was obtained by hood indirect calorimetry, to thermodilution cardiac output (Qth) measured simultaneously during cardiac catheterization in children (n = 16). Because FI(CO2) is a critical factor in hood indirect calorimetry calculations, we also assessed the consequence of taking into account measured FI(CO2) rather than using the usual standard value of 0.0004. We found a good agreement between Q and Qth whether we used experimentally measured FI(CO2) in ambient air (Qth = 0.89 Q + 0.39, r = 0.941) or standard FI(CO2) (Qth = 0.84 Q + 0.55, r = 0.930). However, VCO2 and R computed from standard FI(CO2) differed significantly (p < 0.001) from values derived from measured FI(CO2). This demonstrates that indirect calorimetry allows reasonable estimates of Q, VO2, VCO2, and R provided that the actual values of FI(CO2) are used.

Adolescent↗
PubMed2002

Evaluation of a noninvasive method for cardiac output measurement in critical care patients.

OBJECTIVE: Thermodilution (TD) is the gold standard to monitor cardiac output (CO) in critical care. However, there is concern about the safety of right-ventricular catheterization. The CO(2) rebreathing technique allows noninvasive CO determination by means of the indirect Fick principle. Our objectives were: (a) to assess the accuracy of a new system of CO measurement using the CO(2) partial rebreathing method (PRCO); (b) to evaluate whether the PRCO itself may induce changes in CO. DESIGN AND SETTING: Prospective study in the intensive care department in a university-affiliated hospital. PATIENTS: Twenty-two mechanically ventilated critically ill patients. INTERVENTIONS: CO measured simultaneously by PRCO and TDCO. MEASUREMENTS AND RESULTS: PRCO and TDCO values were compared by concordance analysis. Stability of cardiac output during PRCO was evaluated by comparing the TDCO measurements before, during, and after the partial rebreathing period using analysis of variance. From a total of 79 valid sets of measurements, bias and precision was calculated at -0.18+/-1.39 l/min. The concordance analysis of lower and intermediate CO values (<7 l/min) yielded a bias and precision calculation of -0.07+/-0.91 l/min. No changes in hemodynamics were observed during the partial rebreathing period. CONCLUSIONS: The noninvasive partial CO(2) rebreathing technique may be an alternative method for CO determination in mechanically ventilated critically ill patients. The rebreathing maneuver alone does not induce changes in CO.

Breath Tests↗