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PubMed2005

Less invasive determination of cardiac output from the arterial pressure by aortic diameter-calibrated pulse contour.

BACKGROUND: Cardiac output by modelflow pulse contour method can be monitored quantitatively and continuously only after an initial calibration, to adapt the model to an individual patient. The modelflow method computes beat-to-beat cardiac output (COmf) from the radial artery pressure, by simulating a three-element model of aortic impedance with post-mortem data from human aortas. METHODS: In our improved version of modelflow (COmfc) we adapted this model to a real time measure of the aortic cross-sectional area (CSA) of the descending aorta just above the diaphragm, measured by a new transoesophageal echo device (HemoSonic 100). COmf and COmfc were compared with thermodilution cardiac output (COtd) in 24 patients in the intensive care unit. Each thermodilution value was the mean of four measurements equally spread over the ventilatory cycle. RESULTS: Least squares regression of COtd vs COmf gave y=1.09x[95% confidence interval (CI) 0.96-1.22], R2=0.15, and of COtd vs COmfc resulted in y=1.02x(95% CI 0.96-1.08), R2=0.69. The limits of agreement of the un-calibrated COmf were -3.53 to 2.79, bias=0.37 litre min(-1) and of the diameter-calibrated method COmfc, -1.48 to 1.32, bias=-0.08 litre min(-1). The coefficient of variation for the difference between methods decreased from 28 (un-calibrated) to 12% after diameter-calibration. CONCLUSIONS: After diameter-calibration, the improved modelflow pulse contour method reliably estimates cardiac output without the need of a calibration with thermodilution, leading to a less invasive cardiac output monitoring method.

Adult↗
PubMed1989

Transthoracic electrical bioimpedance versus thermodilution technique for cardiac output measurement during mechanical ventilation.

To study the possible influence of mechanical ventilation on the accuracy of thoracic electrical bioimpedance (TEI) in the measurement of cardiac output, we determined cardiac output concurrently by TEI using Kubicek's equation and by thermodilution in 8 acutely ill patients who were mechanically ventilated (assist/control mode) but who had no underlying respiratory failure. Cardiac outputs were lower with TEI than with thermodilution (3.97 +/- 0.80 vs 4.83 +/- 1.16 l/min p = 0.004) and there was poor correlation between the values (r = 0.41). Although there is a need to develop non-invasive techniques to measure cardiac output, the present study indicates that TEI is not reliable in mechanically ventilated patients.

Adult↗
PubMed1981

Impedance cardiography: non-invasive cardiac output measurement after burn injury.

The election of blood from the heart produces changes in transthoracic impedance. It has been proposed that the cardiac output may be determined from these changes. The cardiac output was measured by impedance cardiography and by the thermal dilution method before and after full thickness burn injury to the skin of the anaesthetized rat. The values obtained by the impedance method showed a good correlation with simultaneous thermal dilution cardiac output measurements (r=+0.67 pre-burn, and +0.76 post-burn). Impedance cardiography confirmed the early post-burn reduction in cardiac output reported by other workers using invasive techniques. Good agreement between the two methods was also obtained when the cardiac output of burn injured animals was altered by fluid infusion. This non-invasive technique of cardiac output monitoring may therefore have an important place in the investigation of cardiac function after trauma and burn injury.

Animals↗
PubMed1991

[Noninvasive determination of cardiac output by continuous wave Doppler technique using apical approach].

The accuracy of a new method for measuring cardiac output with continuous wave Doppler technique from the cardiac apex (CWa) was studied in comparison with two conventional methods, pulsed Doppler technique using apical approach (PWa) and continuous wave Doppler technique using suprasternal approach (CWs). Study population consisted of 25 patients whose cardiac output had been determined by thermodilution method. None of the patients had aortic valve disease, significant tricuspid regurgitation or intracardiac shunt. Aortic flow velocity curves were recorded with the above three Doppler techniques and the cross-sectional area of the aortic root was measured by two-dimensional echocardiogram at mid-systole. Cardiac output (CO) by each Doppler technique was computed using the following equation: CO = aortic cross-sectional area x systolic velocity integral x heart rate. Cardiac output by CWa had better correlation with thermal output value than those by PWa and CWs (r = 0.94, r = 0.85, r = 0.59, respectively). Outputs by PWa and CWs tended to be underestimated compared with thermodilution output. Interobserver difference was smaller in CWa than in PWa and in CWs (4.5%, 7.7%, 6.6%, respectively). Thus, our new method would appear to be accurate and useful in estimating cardiac output, and so may be applied in its case of seriously ill patients.

Cardiac Output↗
PubMed1996

Continuous measurement of cardiac output by the Fick principle in infants and children: comparison with the thermodilution method.

OBJECTIVE: To compare a system that continuously monitors cardiac output by the Fick principle with measurements by the thermodilution technique in pediatric patients. DESIGN: Prospective direct comparison of the above two techniques. SETTING: Pediatric intensive care unit of a university hospital. PATIENTS: 25 infants and children, aged 1 week to 17 years (median 10 months), who had undergone open heart surgery were studied. Only patients without an endotracheal tube leak and without a residual shunt were included. METHODS: The system based on the Fick principle uses measurements of oxygen consumption taken by a metabolic monitor and of arterial and mixed venous oxygen saturation taken by pulse- and fiberoptic oximetry to calculate cardiac output every 20s. INTERVENTIONS: In every patient one pair of measurements was taken. Continuous Fick and thermodilution cardiac output measurements were performed simultaneously, with the examiners remaining ignorant of the results of the other method. RESULTS: Cardiac output measurements ranged from 0.21 to 4.55 l/min. A good correlation coefficient was found: r2 = 0.98; P < 0.001; SEE = 0.41 l/min. The bias is absolute values and in percent of average cardiac output was - 0.05 l/min or - 4.4% with a precision of 0.32 l/min or 21.3% at 2 SD, respectively. The difference was most marked in a neonate with low cardiac output. CONCLUSION: Continuous measurement of cardiac output by the Fick principle offers a convenient method for the hemodynamic monitoring of unstable infants and children.

Adolescent↗
PubMed1989

Renal arterial stenosis as a cause of high output cardiac failure.

A patient is described in whom renal arterial stenosis in a functionally solitary kidney led to arterial hypertension and high output cardiac failure. The pulmonary oedema was resistant to conventional drug therapy but showed prompt regression after percutaneous transluminal angioplasty. This case report demonstrates the usefulness of cardiac output measurement in selected patients presenting with hypertension and pulmonary oedema.

Aged↗
PubMed1997

[Comparison between continuous and intermittent thermodilution measurement of cardiac output during coronary artery bypass operation].

PURPOSE OF THE STUDY: Continuous recording of cardiovascular parameters ranks high in cardioanaesthesia. Various methods to measure the cardiac output have been developed within a period of a few years. We compared the bolus thermodilution method (COI), which has been internationally adopted as "gold standard" method, with the continuous thermodilution method (CCO) for measuring the cardiac output by means of the CCO Vigilance Monitor. Our aim was to find out whether cardiac output can be determined with valid results during coronary artery bypass surgery when using CCO. METHOD: A flow-directed catheter was used (8 Fr. Intelli-Cath CCO PA) in 98 patients during coronary artery bypass surgery after initiation of anaesthesia, introducing the catheter via the right V.jugularis interna, for continuous measurement of the cardiac output via the CCO Vigilance Monitor. The same equipment was also used to measure the cardiac output via the bolus thermodilution method (COI mode) at the following stages: after abandoning the CCO mode 10 minutes subsequent to beginning the operation before sternotomy; 10 minutes after sternotomy before connecting to the heart-lung machine; 15 minutes after disconnecting the heart-lung machine before closing the thorax; and 10 minutes after closing the thorax. As a corresponding comparative value of the CCO method, we used the average cardiac output value calculated for each of the four times of measurement for the last three minutes before applying the boli. RESULTS: In regression analysis we chose the linear model CCO = b x COI with gradient b = 1 and zero point ordinate a = 0. The identity measures, Spearman's rank correlation coefficients, and linear regression coefficients calculated for the four times of measurement, showed good agreement. Scatter of the paired differences between both methods (CCO-CCI) did not have any deterministic structure at all times of measurement. The average bias at the 4 times of measurement was 0.10 l/min, -0.12 l/min, -0.1 l/min, and -0.03 l/min, respectively, with a precision = 2 x s of 1.17 l/min, 1.36 l/min, 1.69 l/min and 1.50 l/min, respectively. The average relative error (100 x [CCO-COI]/COI) with standard deviation was calculated for the 4 times of measurement as 3.2% (s = 15.4%), -1.6% (s = 15.3%), -0.9% (s = 13.9%) and -0.3% (s = 12.0%), respectively. CONCLUSIONS: Literature references show that the continuous thermodilution method is not only valid for intensive-care long-term measurement of cardiac output with approximately stationary haemodynamics, but also-as our results prove-valid if haemodynamics are not usually stationary, such as during coronary artery bypass surgery. The pros of the continuous thermodilution method are that no additional equipment is required apart from the standard equipment used in intensive-care medicine and cardio-anaesthesiology: that there is no stress caused by volume; and that manipulation is safe because no calibration routine is needed and also because measurement and analysis techniques are fully automated. Hence, we are of the opinion that the intraoperative use of this cardiac output measurement technique during open heart surgery is clinically indicated.

Aged↗
PubMed1996

Cardiac output mediates the antihypertensive effect of vasopressin in spontaneous hypertension.

The contribution of cardiac output and total peripheral resistance to the fall in arterial pressure that follows cessation of a 3-h intravenous infusion of arginine vasopressin (AVP; 20 ng.kg-1.min-1) was studied in conscious spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats instrumented with radiotelemetric probes for recording of blood pressure and ultrasonic transit-time flow probes for measuring cardiac output. Cessation of a 3-h infusion of AVP resulted in a significant decrease in arterial pressure in SHR (14-17 mmHg below preinfusion control levels) but not in WKY or in vehicle-treated controls. The fall in pressure persisted for several days. The fall in pressure was associated with a large decrease in cardiac output of 22 +/- 2 ml/min below control levels in SHR, and the time course of the cardiac output response over several days approximated the time course of the pressure response. By contrast, total peripheral resistance remained elevated for some time on withdrawal of the AVP infusion. We conclude that the withdrawal-induced antihypertensive phenomenon in SHR is mediated by a fall in cardiac output and not by a decline in total peripheral resistance.

Animals↗
PubMed1994

Ethyl alcohol reduces cardiac output, stroke volume, and end diastolic volume in the embryonic chick.

It has been established that ethanol causes both human congenital cardiac malformations and structural intracardiac abnormalities in the embryonic chick. In view of a theory that reduced embryonic tissue hemodynamics are associated with the development of malformations, we attempted to determine whether or not a) ethanol altered cardiac blood flow and b) altered hemodynamics were a function of ethanol dose in the chick embryo. Cardiac function in Hamburger-Hamilton stage 19 chick embryos was recorded on videotape before and up to 10 hours after exposure to graded doses of ethanol. Parameters of cardiac function, including cardiac output, were determined from videotaped images by means of computer assistance. Cardiac output decreased in a linear fashion with dose for up to 3 hours after exposure to ethanol. The maximum relative percent decrease in cardiac output was directly related to the dose of ethanol administered. Furthermore, the time required after ethanol treatment for mean cardiac output to return to pretreatment and control values was also dose-dependent--lower doses of ethanol required less time for mean cardiac output to return to pretreatment and control values. Although relatively high doses of ethanol depress cardiac rate, we attribute the significant decrease in cardiac output primarily to parallel dose-dependent decreases in both stroke volume and end diastolic volume. Our data are consistent with the hypothesis that reduced embryonic cardiac blood flow during cardiogenesis is associated with the development of ethanol-induced intracardiac defects in chick embryos.

Animals↗
PubMed1991

Cardiac output by impedance cardiography: two alternative methodologies compared with thermodilution.

One critical component of the Kubicek (8) stroke volume equation, used to measure cardiac output by impedance cardiography, is dZ/dt(max). The present study, conducted on six anesthetized dogs, compared impedance cardiac output derived using two alternative methods of quantifying dZ/dt(max), with simultaneous thermodilution measures. Values for dZ/dt(max) quantified relative to dZ/dt = 0 baseline and relative to the dZ/dt B-point were entered into the Kubicek equation to generate cardiac output measures designated as impedance-A and impedance-B, respectively. Emphasis was placed upon evaluating impedance cardiac output within its accepted limits as a relative change measure. Systematic alterations in cardiac output were produced by intravenously administered isoproterenol, phenylephrine and nitroprusside. Drug-induced changes in cardiac output measured by the impedance-A method were statistically identical to thermodilution. For the impedance-B method, similarity to thermodilution was limited to two of the three drug conditions. Correlations of impedance cardiac output with thermodilution tended to be higher for the impedance-A method. Together with theoretical and practical considerations, these results support quantification of dZ/dt(max) relative to dZ/dt = 0 when used in the Kubicek stroke volume equation.

Animals↗
PubMed1982

Effects of diltiazem on total cardiac output distribution in conscious rats.

The present study was conducted to determine the effect of a "calcium channel blocker," diltiazem (DZ), on cardiovascular dynamics and the distribution of total cardiac output in the conscious rat. Animals were instrumented for right atrial, left ventricular, arterial and venous pressure recordings and the radioactive microsphere technique was used to measure regional blood flow and cardiac output before (control) and during the intravenous infusion of either DZ at three dosage levels (0.4, 2.0, and 10.0 mg/kg/hr) or saline placebo at rates matching those of the DZ protocol (0.015, 0.1 and 0.5 ml/min). Maximum volume infusion rate equaled approximately a 2% increase in blood volume/minute. Systemic vascular resistance, stroke volume, regional vascular resistances and the regional percent distribution of total cardiac output were calculated. In the experimental group (n = 9, body weight = 404 +/- 7 g), DZ, at the highest dose, caused a nonsignificant increase in cardiac output of 61% (cardiac output decreased in one animal) and a significant drop in systemic vascular resistance (45%) while no changes occurred in the control group (n = 5, body weight = 440 +/- 9 g). The major effect of DZ was to increase blood flow and reduce vascular resistance in the coronary circulation (percent distribution of total cardiac output to the coronary circulation, control vs. maximum infusion: saline placebo, 3.9 +/- 0.5 to 4.5 +/- 0.4%; DZ, 3.5 +/- 0.5 to 6.9 +/- 0.5%, P less than .01). The results indicate that DZ does not suppress cardiac function and may actually increase cardiac output secondary to afterload reduction. DZ results in a balanced increase in regional blood flow and no major change in total cardiac output distribution in the conscious rat.

Animals↗
PubMed1981

Direct measurement of cardiac output by gated equilibrium blood pool scintigraphy: validation of scintigraphic volume measurements by a nongeometric technique.

A nongeometric technique for the determination of left ventricular volumes from the count data derived from gated equilibrium blood pool scans was previously described and validated by the demonstration of an excellent correlation between the derived data and angiographically determined left ventricular volumes. To provide a further prospective evaluation of this method and to validate its ability to determine stroke volume and cardiac output by a technique that is itself independent of geometric assumptions, simultaneous measurements of cardiac output by the thermodilution technique and gated scintigraphy were performed in 21 patients without valve regurgitation or intracardiac shunts. To substantiate the reliability of scintigraphic measurements at high levels of cardiac output, seven patients had multiple measurements of cardiac output at rest and during an infusion of isoproterenol. There was an excellent correlation between thermodilution and scintigraphic values for cardiac output (scan cardiac output = 0.99 thermodilution cardiac output - 0.005 liters/min; n = 31, standard error of the estimate [SEE] = 0.175 liters/min, r = 0.97) as well as between thermodilution and scintigraphic stroke volumes (scan stroke volume = 1.03 thermodilution stroke volume - 2.8 ml; n = 31, SEE = 2.5 ml, r = 0.95). In addition, the relation between scintigraphic and angiographic measurements of left ventricular volumes continued to be excellent: In 15 patients with technically adequate angiograms, scintigraphic left ventricular volume = 0.90 angiographic left ventricular volume + 7 ml (n = 30, SEE = 10 ml, r = 0.91). Thus, this study further validates the nongeometric method of measuring left ventricular volumes with gated scintigraphy and demonstrates its ability to measure left ventricular stroke volume and cardiac output reliably.

Adult↗
PubMedDate not supplied

[Measuring cardiac output in infants with the Fick principle via oxygen consumption: animal experiment and clinical results].

UNLABELLED: The aim of this investigation was the validation of cardiac output measurement in children using the method of Fick with the help of a new equipment for the determination of oxygen uptake. METHODS: We compared the cardiac output measured with thermodilution with the calculated cardiac output using the method described by Fick in an animal model (11 dogs, mean weight 20 kg). For determining the cardiac output on Fick's principle oxygen uptake and oxygen content of the arterial and pulmonary-arterial blood was measured in the ventilated dogs. To examine the method of Fick in clinical routine we also determined oxygen uptake and arterial and central venous oxygen content in 5 children in the postoperative period after cardiac surgery with a mean weight of 8.5 kg. Cardiac output in the patients was calculated with the central venous and the pulmonary-arterial oxygen content. The two results were compared. RESULTS: The animal model showed a good correlation of cardiac output measurement on thermodilution and on Fick's method (alpha = 0.001, t-test of significance of correlation). With the method of Fick we found also reliable results at follow up in the clinical routine in the 5 children. The comparison of cardiac output calculated with the central venous oxygen content versus the pulmonary-arterial oxygen content shows a good correlation over all (r = 0.92). In some cases however we found profound differences.

Animals↗
PubMed1991

Continuous determination of cardiac output using a flow-directed Doppler pulmonary artery catheter.

A newly developed, flow-directed, Doppler pulmonary artery catheter that uses multiple ultrasonic transducers to measure instantaneous and continuous cardiac output was evaluated in 20 patients undergoing cardiac and vascular surgical procedures. Cardiac output was determined using the product of the average velocity and the area of the main pulmonary artery. Pulmonary artery area was obtained from measurements of diameter via ultrasound transit time, and average velocity of blood flow was determined from the Doppler shift frequency. Two hundred thirty-eight simultaneous Doppler catheter and thermodilution cardiac output measurements were obtained preoperatively, intraoperatively, and during postoperative recovery. Catheter indwelling time varied from 18 through 94 hours (mean +/- SD, 40 +/- 19 hours) with 2 to 26 (mean +/- SD, 12 +/- 6) sets of triplicate cardiac output measurements obtained per patient. Doppler catheter cardiac output correlated well with thermodilution (r = 0.76, slope or m = 0.87, and SEE = 0.05 with P = 0.0001) and mean predictive error (bias) appeared clinically insignificant (bias +/- SD, -0.13 +/- 0.79 L/min). Accurate, continuous monitoring of instantaneous and mean cardiac output appears possible with use of this Doppler pulmonary artery catheter system.

Blood Flow Velocity↗
PubMed1997

Reproducibility of a semiautomated acetylene rebreathing technique for measuring cardiac output in humans at rest.

The specific aims of the present study were to determine: (1) the day-to-day reproducibility of a semiautomated acetylene rebreathing technique for measuring cardiac output under resting conditions; (2) the reproducibility of this technique among subjects differing in gender and age; and (3) the number of trials within a session necessary to maximize the day-to-day reproducibility of the technique. To address these aims, cardiac output was measured in 21 healthy men (n = 8) and women (n = 13) between the ages of 25 and 71 years in the supine posture on two separate days. Mean levels of cardiac output at rest were similar on day 1 vs. day 2 in the overall group. Cardiac output measured on day 1 was highly correlated (r = 0.98, P < 0.001) with cardiac output measured on day 2. The day 1 to day 2 mean difference in cardiac output for the individual subjects was < 4%. The mean levels of heart rate and stroke volume also were similar between day 1 and day 2. The relation between cardiac output measured on day 1 vs. day 2 in the gender and age subgroups was similar to that observed in the overall group. The mean absolute difference among the three rebreathing trials within a day was 360 ml min-1 in the overall group, with a coefficient of variation of 7%. The variability between rebreathing trials measured on day 1 vs. day 2 in the gender and age subgroups was similar to that observed in the overall group. The reliability of cardiac output measured on different days was excellent with a single rebreathing trial (r = 0.93) and improved significantly up to three trials (r = 0.98). In conclusion, the findings of the present study indicate that the acetylene rebreathing technique can be a highly reproducible method for measuring cardiac output under resting conditions. The reproducibility is consistently strong in healthy humans of varying age and in both genders, and is enhanced by the use of multiple trials.

Acetylene↗
PubMed1997

Cardiac output estimation by visual inspection vs thermodilution during cardiac surgery.

PURPOSE: The objectives of this study were: 1) to compare the estimated cardiac output (CO) by visual inspection with objective measurements by thermodilution: 2) to compare the estimated systemic vascular resistance (SVR) with objective measurements by thermodilution; and 3) to assess whether management of the patient, based on subjective values, would have differed from the management of the patient based on the objective values. METHODS: A non-randomized, prospective, blinded study was conducted at a tertiary care university hospital. Following institutional ethics approval, 35 patients undergoing cardiac surgery, with pulmonary artery catheter (PAC) monitoring, were studied. Prior to the measurement of CO by thermodilution, but after separation from cardiac pulmonary bypass, the CO and SVR were estimated by the anaesthetist and the surgeon. Bland and Altman's method was used for statistical analysis. RESULTS: Surgeons' estimates of CO were comparable with the objectively measured thermodilution measures: in each case (100%), the difference between the subjective estimate and the objective measurement was less than two standard deviations from the mean difference of the two methods. Anaesthetists' estimates, by visual inspection, were also comparable with the objectively measured thermodilution values; 94.6% of cases. The surgeons' and anaesthetists' estimates of SVR were also comparable with the thermodilution measures in all cases. Management based on subjective values would have differed from those based on objective values in only 8.6% of cases. CONCLUSION: An advantage of cardiac surgery is the ability to observe the heart and assess its performance visually. This study demonstrated that estimates of CO and SVR by clinical observation are comparable with the pulmonary artery catheter's derived values.

Aged↗
PubMed2003

Esophageal Doppler: noninvasive cardiac output monitor.

In this article we describe the esophageal Doppler, a noninvasive, instantaneous cardiac output monitor. Its reliability has been demonstrated to be comparable to that of other current techniques used in the clinical arena to measure cardiac output. It helps guiding intravascular fluid resuscitation by quantifying the increase in flow in response to fluid challenges and by indicating the plateau of the patient's cardiac function curve. When the plateau has been reached, further fluid loading may result in congestion without improvement in systemic flow. Thus, measuring cardiac output is the only way to determine the upper limit for fluid intake. In addition, a strategy based on cardiac output optimization has proven beneficial in high-risk surgical patients.

Cardiac Output↗
PubMed1985

A longitudinal study of cardiac output in unstressed pregnant guinea pigs.

A previous study in pregnant guinea pigs failed to demonstrate any increase in cardiac output when a group of pregnant animals was compared with four nonpregnant animals. In the current study an increase in cardiac output of 35 +/- 14 (SE) ml/min, a 13% increase, was observed during an average 2-wk interval between 44 and 58 days of pregnancy (P less than 0.05, term 68 days, n = 8). A significant increase in placental blood flow of 14.8 +/- 6.2 ml/min (42% increase, P less than 0.05) was also observed during this interval without significant change in the percentage of cardiac output going to the uterus. The data on cardiac output and its distribution to the uteroplacental circulations are consistent with reports in other mammalian species; to accommodate the increased demands of the uteroplacental circulation, cardiac output increases as pregnancy advances. These data demonstrate that multiple observations in the same animal describe cardiac output and its distribution more accurately than a single observation.

Animals↗