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PubMed2005

Non-invasive cardiac output determination by two-dimensional independent Doppler during and after cardiac surgery.

PURPOSE: This study was to compare noninvasive measurement of cardiac output (CO) using a novel Doppler technique with invasive CO measurements in the postcardiac surgical intensive care unit. DESCRIPTION: Thirty-six patients (67.2 +/- 10 years, New York Heart Association functional class 3.1 +/- 0.3) undergoing coronary revascularization were prospectively examined postoperatively. One hundred eighty paired CO and stroke volume measurements were compared from the noninvasive USCOM device (Sydney, Australia) and the invasive Swan-Ganz catheter at varying COs. Eighteen measurements were performed intraoperatively by direct insonation of the right ventricular outflow tract. EVALUATION: Mean noninvasive and invasive CO values were 5.15 +/- 1.98 L/min and 4.92 +/- 2.0 L/min, respectively (r = 0.870; p < 0.01). The mean difference between methods was -0.23 +/- 1.01 L/min greater than a range of CO values from 2.5 to 9.9 L/min. Mean central venous saturation percentage was 72 +/- 9%, correlating with both noninvasive and invasive CO (r = 0.474 and 0.606, respectively, p < 0.01). Intraoperatively, both direct and invasive CO were identical. CONCLUSIONS: Using the ultrasonic cardiac output monitoring (USCOM) device it is possible to determine noninvasive beat-to-beat CO in postcardiac surgery patients without the possible complications associated with invasive right heart catheterization. The USCOM CO and stroke volume showed a very good agreement with invasive Swan-Ganz measures and correlated with central venous saturation percentage.

Aged↗
PubMedDate not supplied

Supranormal cardiac output in the dopamine- and dobutamine-dependent preterm infant.

To evaluate the incidence of low cardiac output in preterm infants with respiratory distress syndrome (RDS), we measured cardiac output, stroke volume, heart rate, mean arterial blood pressure, and systemic vascular resistance at 8-48 hours of age in 30 preterm infants with RDS who were dependent on inotropic support. We then compared them to 23 normotensive preterm infants with RDS and 27 preterm infants without RDS. RDS infants had a higher cardiac output and lower systemic vascular resistance and blood pressure than infants without RDS. Infants treated with dopamine and dobutamine had a higher cardiac output and heart rate than infants on dopamine alone or the normotensive controls but a lower blood pressure and systemic vascular resistance than the normotensive controls. Supranormal cardiac output (>400 ml/min/kg) was detected in 57% of the infants in the dopamine + dobutamine subgroup (p = 0.009) versus 17% in the normotensive RDS subgroup and 12% in the dopamine subgroup. These data show that high cardiac output is relatively common in infants with RDS dependent on dopamine and dobutamine but is not reflected in the blood pressure.

Cardiac Output↗
PubMed1997

Near continuous cardiac output by thermodilution.

A new thermodilution method for frequent (near continuous) estimation of cardiac output, without manual injection of fluid into the blood, was tested. The method utilizes a pulmonary artery catheter equipped with a fluid filled heat exchanger. The technique is based on cyclic cooling of the blood in the right atrium and measurement of the temperature changes in the pulmonary artery. Using this technique, a new estimate of cardiac output can be obtained every 32 s. Cardiac output estimates, obtained for a running mean of three measurements with this method, were compared to the mean of three conventional thermodilution measurements. The measurements were obtained during short periods of stable respiration and circulation. In six pigs, we made 46 paired measurements of conventional thermodilution (TD) and near continuous (TDc) thermodilution. The cardiac output (COTD) ranged from 2.4-13.7 l/min (mean 5.4 l/min). The best linear fit through the paired data points was COTDc = -0.57 + 1.01 COTD. The mean difference between the methods was -0.50 l/min (S.D. = 0.39). The mean coefficient of variation of repeated measurements with the near continuous thermodilution was 3.6%. Considering changes of more than 0.25 l/min to be significant, all changes in cardiac output measured by conventional thermodilution were followed by the running mean of three near continuous thermodilution estimates. This study demonstrates the feasibility of the new method to monitor cardiac output, and to detect all changes greater than 0.25 l/min.

Animals↗
PubMed1991

[Non-invasive measurement of cardiac output by the CO2 rebreathing method and its reliability in clinical practice].

A Commercially available, non-invasive system for estimation of cardiac output by the CO2-rebreathing method (Sensormedicus MMC4400) was evaluated to determine its reliability in clinical practice. Values of cardiac output were obtained at rest and during mild to moderate bicycle ergometer work in patients with ischemic heart disease or hypertension. Cardiac output measured by the CO2-rebreathing method was significantly correlated with that measured simultaneously by dye dilution or thermodilution methods. Cardiac output values determined by the CO2-rebreathing method were the same as those obtained by the two invasive methods in reproducibility. When cardiac output and Vo2 were normalized for body weight, they were significantly correlated with each other. This result was obtained both by the CO2-rebreathing method, and by the two invasive methods. These results indicate that MMC4400 will provide a value for cardiac output substantially the same as that obtained by using more laborious invasive methods. Clinical use of the CO2-rebreathing method has been limited by technical difficulties. However, the recently developed non-invasive cardiac output measurement system (MMC4400) uses a microcomputer to analyze the results, and the operator can determine the values for cardiac output easily. Furthermore, it simultaneously measures VO2, VCO2 and VE, so the operator can estimate the measured values for cardiac output with background information on ventilatory gas analysis. Determination of cardiac output through the use of the CO2-rebreathing method is suitable particularly for exercise studies, and it is expected to be a useful device, in the near future, for evaluating cardiac function of patients with primary cardiac diseases.

Adult↗
PubMed1989

Response to low cardiac output: developmental differences in metabolism during oxygen deficit and recovery in lambs.

When cardiac output is critically lowered, whole body O2 consumption decreases and an O2 deficit accumulates. With restoration of cardiac output, an excess O2 consumption is expected in order to "repay" some or all of the O2 deficit. We tested the hypothesis that young lambs, with higher resting O2 consumption, cardiac output and growth rates than older lambs, would repay less of their O2 deficit because they have a higher proportion of nonessential metabolism. We reduced cardiac output acutely by inflating a Foley catheter in the right atrium of spontaneously breathing, sedated lambs at ages 2 (n = 5) and 8 (n = 5) wk. Each lamb was studied with low cardiac output periods of 30 and 60 min on different days. Aortic and pulmonary artery blood pressures, gases, and O2 saturations, venous Hb, and arterial lactate concentrations were measured every 10 min during baseline, low output, and 60 min of recovery. Oxygen consumption was monitored continuously. Oxygen deficit and excess O2 of recovery were calculated from the time integral of the difference between O2 consumption at baseline and during the respective study period. The average percent decreases in cardiac output (66.4 and 64.6%) and O2 consumption (38.1 and 35.1%) were similar in the 2- and 8-wk groups, respectively. There was no consistent relation between O2 deficit and O2 repayment in either age group. However, on average the 2-wk group repaid a significantly lower percentage (3 +/- 16%, mean +/- SEM) than 8-wk-olds (76 +/- 29%).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1981

Control of cardiac output in exercising dogs using different types of workload.

The system which controls cardiac output was studied in dogs during exercise on the treadmill. The aim was to investigate whether the pattern of the workload influences the control system. To measure cardiac output, electromagnetic flow probes were implanted at least 10 days before the exercise study. During the experiments cardiac output was computed on a beat-to-beat basis. We compared changes in cardiac output resulting from stepwise, sinusoidally and randomly varying workloads, obtained by changing treadmill velocity accordingly. The time constants found with sinusoidally and randomly varying workloads were 11.6 and 10.0s respectively. The time constants of the alteration in cardiac output resulting from a step function was 9.9s for the positive step and 15.6s for the negative step. However when the stepwise change in workload was between a velocity of 0.67 and 1.56 m.s-1 positive and negative steps yielded the same time constant (13.5 s). It is concluded that the pattern of the workload has no influence on the control system of cardiac output during exercise.

Animals↗
PubMed1999

A comparison of transoesophageal echocardiographic Doppler across the aortic valve and the thermodilution technique for estimating cardiac output.

This study was undertaken in order to elucidate the differences between various planes of measurement and Doppler techniques (pulsed- vs. continuous-wave Doppler) across the aortic valve to estimate cardiac output. In 45 coronary artery bypass patients, cardiac output was measured each time using four different Doppler techniques (transverse and longitudinal plane, pulsed- and continuous-wave Doppler) and compared with the thermodilution technique. Measurements were performed after induction of anaesthesia and shortly after arrival in the intensive care unit. Optimal imaging was obtained in 91% of the patients, in whom a total of 82 measurements of cardiac output were performed. The respective mean (SD) areas of the aortic valve were 3.77 (0.71) cm2 in the transverse plane and 3.86 (0.89) cm2 in the longitudinal plane. A correlation of 0.87 was found between pulsed-wave Doppler cardiac output and the thermodilution technique in either transverse or longitudinal plane. Correlation coefficients of 0.82 and 0.84 were found between thermodilution cardiac output and transverse and longitudinal continuous-wave Doppler cardiac output, respectively. Although thermodilution cardiac output is a widely accepted clinical standard, transoesophageal Doppler echocardiography across the aortic valve offers adequate estimations of cardiac output. In particular, pulsed-wave Doppler cardiac output in both the transverse and longitudinal plane provides useful data.

Aged↗
PubMed1997

Evaluation of a continuous cardiac output and mixed venous oxygen saturation catheter in critically ill surgical patients.

OBJECTIVE: To evaluate the agreement of continuous cardiac output and mixed venous oxygen saturation measurements, obtained with a modified pulmonary artery catheter, with those values obtained by standard intermittent bolus thermodilution and cooximetry. DESIGN: Prospective, clinical investigation. SETTING: A surgical intensive care unit in a tertiary referral center. PATIENTS: Twenty-one adult critically ill surgical patients, requiring pulmonary artery catheter monitoring. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A modified pulmonary artery catheter capable of continuous monitoring of cardiac output and mixed venous oxygen saturation was used with either an 8.5-Fr or a 9-Fr introducer. At random intervals, the continuous cardiac output measurement was compared with the cardiac output obtained using standard intermittent bolus thermodilution. The system was calibrated every 24 hrs for mixed venous oxygen saturation monitoring. Each saturation obtained by the laboratory cooximeter was compared with that value recorded using the catheter. Data points for 202 pairs of cardiac output (21 patients, 31 catheters) and 65 pairs of mixed venous oxygen saturation (20 patients, 28 catheters) were obtained. The bias and precision of the cardiac output data were 0.49 and 1.01 L/min, respectively. The agreement between the continuous and bolus values decreased as the cardiac output increased. Heart rate did not affect the agreement between the continuous and bolus techniques. The bias and precision of the mixed venous oxygen saturation data were -0.57% and 3.76%, respectively. The hematocrit did not affect the bias or precision of the venous saturation data over the hematocrit range observed (23.2% to 44.6%). Fewer catheter malfunctions were observed when the catheter was used with a 9-Fr introducer than with an 8.5-Fr introducer. CONCLUSIONS: The test catheter adequately measures continuous cardiac output and mixed venous oxygen saturation in the clinical setting. Because intermittent bolus thermodilution is not a true "gold standard" for cardiac output determination, new techniques compared with bolus thermodilution may fail to achieve accuracy expectations. A 9-Fr introducer is recommended, as fiberoptic damage may have occurred when the 8.5-Fr introducer was used.

Adult↗
PubMed1984

[Low cardiac output syndrome in heart surgery patients].

Using cardiac chamber catheterization and isotope methods, the systemic and intracardiac hemodynamics was studied in 232 patients who had undergone heart surgery under conditions of extracorporeal circulation. The syndrome of a low cardiac output was detected in 46.9% of the patients and was caused by various forms of heart failure, by hypovolemia, a postoperative shock and pericardiac tamponade. The functional state of the right and the left ventricles of the heart in various types of circulatory insufficiency was shown to vary in different directions. The volume of the circulating blood in the postoperative period was determined by the adequacy of the blood loss compensation, by blood deposition, the redistribution of fluid between the vascular, interstitial and cellular spaces of the body and also by the functional condition of the myocardium. The syndrome of a low cardiac output associated with cardiac tamponade is due largely to the diastolic insufficiency of the myocardium. The shock noted in the open heart surgery patients is a polyetiological syndrome in which the impaired circulation is secondary to myocardial failure, deficit of the circulation blood volume, and microcirculatory disorders.

Blood Transfusion↗
PubMed2004

In vitro assessment of a continuous cardiac output catheter system.

Continuous measurement of cardiac output (CCO) is useful in assessing the cardiovascular status of patients during cardiac surgery and in intensive care. Recently, a CCO system (truCCOMS, Aortech, UK), capable of detecting rapid changes in cardiac output (CO) was introduced. The method is based on the energy required to maintain an integral heat-transfer device at constant temperature above the ambient value. The aim of this study was to assess the performance of this CCO system in vitro under in steady as well as pulsatile flow conditions representative of those in the pulmonary artery. In order to determine the sensitivity of the system to changes in vessel cross-sectional area and therefore local flow velocity, the catheter was deployed in a linear-tapered tube. Steady and pulsatile flows were generated, and the electrical power at various locations along the tapered tube was recorded. The results show significant differences in the performance under the two different flow conditions. In steady flow, the CO was highly dependent on the local velocity whereas in pulsatile flow, CO varied much less with local velocity. The sensitivity expressed as a percentage increase in CO per 100% increase in velocity at a CO of 5 l min(-1) was 87% in steady flow and 24% in pulsatile flow. Experiments carried out with three fluids with different viscosity show that the errors in determining CO in the tapered tube were also dependent on the Reynolds number and flow regime. The mean errors ranged from about 50% at 2 l min(-1) to less than 10% at 8 l min(-1). The correlation between the predicted and actual CO was generally good. In conclusion, the pulmonary artery catheter is not recommended in situations where blood flow is expected to be steady or of low pulsatility. It may, however, be suitable under normal pulsatile flow conditions in the pulmonary artery.

Cardiac Catheterization↗
PubMed1992

Respiration and measurement of cardiac output by thermodilution and central or peripheral dye dilution.

Cardiac output as measured by indicator dilution methods during artificial ventilation shows differences up to +/- 35%. We studied the influence of spontaneous breathing on measurement of cardiac output by thermodilution (TD) and central (CDD) and peripheral dye dilution (PDD) in seven anesthetized dogs. Injection of indicator was timed at one of five chosen moments in a respiratory cycle. The indicator for TD was also used as solvent for indocyanine green. Results were normalized by the value obtained with injection at inspiratory onset. Results of the central dilution methods showed a slight but not significant difference between values measured with injection at 25 and 75% of the respiratory cycle: 105.7 and 98.0%, respectively, (TD) and 102.3 and 97.2% (CDD). Mean cardiac output determined by TD, CDD, or PDD was not significantly different. We conclude that 1) a reasonable estimate of cardiac output may be obtained by means of a single indicator-dilution curve and 2) the choice of the dilution method may be determined by practical considerations.

Animals↗
PubMed1996

Testing the safety of Baxter continuous cardiac output monitoring system.

The safety of a new continuous cardiac output monitoring system, recently introduced by Baxter Healthcare Corporation's Edwards Critical-Care Division, was evaluated in normal sheep. The study compared the biocompatibility and safety of the Vigilance CCO Monitoring System, which employs a continuous cardiac output (CCO) catheter with Baxter Edward's standard Paceport pulmonary artery catheter. The CCO catheter, which monitors hemodynamic pressures and provides continuous measurement of cardiac output based on the thermodilution principle, contains a thermal filament that is powered and controlled by a unique cardiac output monitor. Parameters were measured periodically in conscious animals and complete necropsies were performed after each study. Time Control, Paceport, and four CCO groups were studied. Selected groups were studied for 3 days (acute), 7 days (subacute), and/or 4 weeks after 3 days of continuous use (recovery). Results showed no significant differences between the CCO and Paceport catheters in any of the parameters studied. On gross pathology, observations were similar. The only difference between catheters were microscopic findings of focal subendothelial or subendocardial changes correlated with areas that could have come into contact with the CCO catheter. In acute groups, these changes consisted of a localized myofiber degeneration or necrosis, while in subacute and recovery groups, consisted only of fibrosis. None of the changes were clinically significant. Thus, the CCO catheter, used in conjunction with the Vigilance CCO Monitoring System, appears to pose no additional risk over a standard Paceport catheter in normal sheep after continuous use for up to 7 days.

Animals↗
PubMed1996

An investigation of the changes in aortic diameter and an evaluation of their effect on Doppler measurement of cardiac output in pregnancy.

Measurement of cardiac output by means of Doppler ultrasound is based on the velocity of aortic blood flow and therefore requires that aortic diameter should not change between measurements. Work has been published which suggests that, in pregnancy, aortic diameter varies significantly with systemic blood pressure. The implication of this is that aortic diameter must be remeasured for each determination of cardiac output in pregnant patients. This study investigated the changes in aortic diameter with blood pressure in patients having spinal anaesthesia for caesarean section. Aortic diameter did appear to vary with blood pressure but this variation was within the error of the measurement and did not significantly affect the accuracy of the technique.

Journal Article↗
PubMed1987

Changes in cardiac output during sustained maximal ventilation in humans.

To determine the increment in cardiac output and in O2 consumption (Vo2) from quiet breathing to maximal sustained ventilation, Vo2 and cardiac output were measured using an acetylene rebreathing technique in five subjects. Cardiac output and Vo2 were measured multiple times in each subject at rest and during sustained maximal ventilation. During maximal ventilation subjects breathed 5% CO2 to prevent hypocapnia. The increase in cardiac output from rest to maximal breathing was taken as an estimate of respiratory muscle blood flow and was used to calculate the arteriovenous O2 content difference across the respiratory muscles from the Fick equation. Cardiac output increased by 4.3 +/- 1.0 l/min (mean +/- SD), from 5.6 +/- 0.7 l/min at rest to 9.9 +/- 1.1 l/min, during maximal ventilations ranging from 127 to 193 l/min. Vo2 increased from 312 +/- 29 to 723 +/- 69 ml/min during maximal ventilation. O2 extraction across the respiratory muscles during maximal breathing was 9.6 +/- 1.0 vol% (range 8.5 to 10.7 vol%). These values suggest an upper limit of respiratory muscle blood flow of 3-5 l/min during unloaded maximal sustained ventilation.

Adult↗
PubMed1994

Thermodilution left-sided cardiac output for valve area determination after balloon mitral valvotomy.

This study was conducted to establish the validity of left-sided cardiac output measurement with a Swan-Ganz catheter and assess its accuracy in estimating mitral valve area (MVA) by the Gorlin formula. The use of right-sided cardiac output after balloon mitral valvotomy (BMV) can give inaccurate measurements for Gorlin-derived MVA because of the atrial septal defect (ASD) created during the procedure. The left-sided cardiac output was measured with a Swan-Ganz catheter (proximal port in the left atrium and then in the left ventricle, and distal port in the ascending aorta) in 10 consecutive patients before and after BMV. Gorlin-derived MVA cardiac output by this method was compared with (1) Gorlin-derived MVA by means of right-sided cardiac output with and without balloon occlusion of the ASD and (2) MVA measured by echocardiography. Before BMV, a close agreement with a good correlation between left-sided and right-sided cardiac output was found (r = 0.83, p = 0.006). Furthermore, Gorlin-derived MVA by cardiac output with either method was comparable with valve area by echo. After BMV, left-sided cardiac output correlated well (r = 0.92, p = 0.0002) and was comparable with right-sided cardiac output with occlusion of the ASD (mean difference 0.17 +/- 0.49 L/min, p = 0.3) but was significantly lower than the value obtained with open ASD (mean difference 0.93 +/- 0.77 L/min, p = 0.004). Comparison of the correspondent MVAs yielded similar results. Gorlin-derived MVA with left-sided cardiac output and MVA by echo were also similar.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMed2001

Liver transplantation without venovenous bypass: morbidity and mortality in patients with greater than 50% reduction in cardiac output after vena cava clamping.

OBJECTIVE: To investigate whether a decrease in cardiac output of >or=50% after vena cava clamping is associated with an increase in perioperative morbidity or mortality in patients undergoing orthotopic liver transplantation without venovenous bypass. DESIGN: Retrospective, clinical study. PARTICIPANTS: Patients undergoing elective orthotopic liver transplantation without venovenous bypass (n = 172). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: In 82 patients (group 1), the decrease in cardiac output after vena cava clamping was >or=50%; in 90 patients (group 2), the decrease was <50%. Hemodynamics during surgery and perioperative morbidity and mortality were compared between group 1 and group 2 patients. Mean arterial pressure during the anhepatic phase was not significantly different between groups, but cardiac output and mixed venous oxygen saturation were significantly lower in group 1 patients. Perioperative mortality, need for postoperative renal replacement therapy, postoperative serum creatinine levels, and graft function were not different between groups. CONCLUSION: A >50% reduction in cardiac output after vena cava clamping is not associated with an increase in perioperative morbidity and mortality when compared with patients with a less pronounced reduction in cardiac output. These results question the common practice of basing the indication for venovenous bypass during the anhepatic phase on a reduction in cardiac output of >50% after a trial of vena cava clamping.

Cardiac Output↗
PubMed1986

Thermodilution cardiac output--an in vitro model of low flow states.

The accuracy and reproducibility of thermodilution cardiac output measurements were examined in vitro at low flows, using the Edwards cardiac output computer. For each of 18 different volumetrically measured flows between 130 and 1035 ml/min, three cardiac outputs were determined for each of four different injectate volumes (1,2,3, and 5 ml) at two different temperatures (0 degrees C and room temperature). There was a significant (p less than .001) correlation between measured flow and cardiac output for all injectate volumes at both temperatures. The slopes of the regression lines ranged between 0.97 and 1.25, and the y-intercepts were all greater than 0. Although this thermodilution technique overestimated cardiac output, it was a reproducible means of measuring cardiac output in this low-flow in vitro model.

Cardiac Output↗
PubMed1985

Thermodilution cardiac output measurement. Effects of the respiratory cycle on its reproducibility.

Thermodilution cardiac output measurements are commonly employed in the management of critically ill patients. Serial measurements often show significant variation, and poor reproducibility limits their clinical utility. There are no clinical studies revealing when to perform thermodilution cardiac output measurements in relation to the respiratory cycle. We prospectively studied 32 patients in a randomized scheme comparing three thermodilution cardiac output measurements at peak-inspiration, at end-exhalation, or randomly in spontaneously breathing and mechanically ventilated patients. Saline injections initiated at peak-inspiration or end-exhalation resulted in cardiac output measurements with much smaller standard deviations than those seen with random injections. Thermodilution cardiac output measurements performed at random times in the respiratory cycle should be avoided, and we recommend initiating these measurements at end-exhalation.

Cardiac Catheterization↗