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PubMed1988

An approach to measuring cardiac output with Doppler flow probes in conscious rats.

The continuous measurement of cardiac output in conscious rats is difficult. Previously, Doppler flow probes have been applied to the ascending aorta by means of silicone cuffs. The placement of these cuffs can conceivably introduce errors engendered by the destruction of nerve fibers that are important in cardiac autonomic innervation. We report a novel method of Doppler flow-probe attachment directly to the ascending aorta by means of a polyacrylic cement. When we compared the response with baroreceptor activation with methoxamine and nitroprusside in conscious rats equipped either with probes attached via cuffs or directly via cement, we observed that animals equipped with cuffs failed to give the expected cardiac output and heart rate responses after nitroprusside administration. In contrast, animals that had their probes attached with cement displayed the expected responses. The data not only show that probes applied with cement give a result superior to probes attached with cuffs but also verify the suspicion that the ascending aorta is associated with nerve fibers that are important in mediating baroreceptor responses.

Animals↗
PubMed1980

Increased cardiac output and oxygen transport after intraoperative isovolemic hemodilution. A study in patients with peripheral vascular disease.

The effects of isovolemic hemodilution on cardiac output and oxygen transport in 11 patients during elective vascular surgery were evaluated. Mean hemoglobin level was decreased from 12.5 +/- 0.6 to 10.2 +/- 0.5 g/dL by withdrawing blood and replacing it with an equal volume of colloid. Hemodilution increased cardiac output from 4.8 +/- 0.3 to 6.4 +/- 0.4 L/min, increased oxygen delivery from 830 +/- 75 to 900 +/- 95 mL/min and increased oxygen consumption from 190 +/- 20 to 240 +/- 40 mL/min. Systemic vascular resistance and mean arterial blood pressure decreased significantly, but cardiac filling pressure, pulmonary vascular resistance, heart rate, and intrapulmonary shunt did not change. In four of these patients who did not require all their blood during surgery, 1 unit of their withdrawn blood was reinfused after completion of surgery. In all four patients, cardiac output, oxygen delivery, and oxygen consumption decreased from the pretransfusion values. We conclude that, since intraoperative isovolemic hemodilution increased blood flow and systemic oxygen transport, it may be useful in the intraoperative management of patients with atherosclerotic vascular disease.

Aged↗
PubMed1976

Effect of thoracic blood volume changes on steady state cardiac output.

We have investigated the extent to which shifts of blood volume out of or into the thoracic region influence the steady state cardiac output. The systemic circulation of anesthetized dogs was replaced with an artificial circuit which stimulated the pertinent mechanical characteristics of an intact circulation. As in the normal animal, the steady state venous return was proportional to the pressure gradient for venous return (i.e, mean systemic minus right atrial pressure). Cardiac function was altered either by administration of epinephrine or by changes in left ventricular afterload. At a constant mean aortic pressure of 100 mm Hg, epinephrine administration increased the steady state cardiac output by 55%. Half of this increase resulted from the lowered mean right atrial pressure (caused by improved cardiac function); the remainder resulted from an increased mean systemic pressure (caused by the volume shift to the systemic circulation). Increases in afterload transferred sufficient volume to the heart-lung compartment to reduce significantly the mean systemic pressure and, hence, the steady state venous return. Our results indicate that the heart-lung compartment contains a significant volume which is under cardiac control. In addition to being able to alter the right atrial pressure, the heart can modulate the steady state cardiac output by adjusting the mean systemic pressure. To this degree the heart can adjust its own venous return.

Animals↗
PubMed1985

Effect of isoproterenol on uterine blood flow and cardiac output distribution in pregnant guinea pigs.

The effects of isoproterenol, 0.05 micrograms X min-1 X kg-1 infused intravenously for 2 hours, on cardiac output distribution and uteroplacental blood flow were studied in six chronically catheterized guinea pigs between 60 and 68 days of pregnancy. Isoproterenol caused marked cardiac stimulation: Cardiac output was increased by 41%, of which 70% was distributed to the carcass and gastrointestinal tract. Absolute placental blood flow remained essentially unchanged, but the placental fraction of cardiac output decreased from 16% to 11%. Myometrial blood flow increased by 72%. Uteroplacental vascular resistance did not change significantly. In the guinea pig in late pregnancy beta-adrenergic receptors are present in the myoendometrial vessels but could not be demonstrated in the maternal vessels supplying the placenta.

Animals↗
PubMed1989

Changes in cardiac output after acute blood loss and position change in man.

Thoracic bioimpedance cardiac output (Qtbi) was measured at 1-min intervals in 27 volunteers before, during, and after withdrawing 500 ml (3.7 to 8.5 ml/kg; mean 5.8) of blood. The effects of passive leg raising (PLR) and standing on Qtbi were measured before and after blood withdrawal. Arterial oxygen saturation (SaO2), transcutaneous oxygen tension (PtcO2), mean arterial BP (MAP), and heart rate (HR) were also measured before and after blood withdrawal. Thoracic bioimpedance cardiac index (CI) decreased 18% (0.8 +/- 0.1 L/min.m2, p less than .0001) and stroke volume index (SI) decreased 22% (14.8 +/- 2.7 ml/beat.m2, p less than .0001) after blood withdrawal. HR, MAP, SaO2, and PtcO2 were not significantly different after blood withdrawal. Before blood withdrawal PLR increased CI 6.8% (0.3 +/- 0.1 L/min.m2, p less than .0001); after blood withdrawal PLR increased CI 11.1% (0.4 +/- 0.1 L/min.m2, p less than .0001). PLR can increase stroke volume and cardiac output in hypovolemic humans.

Acute Disease↗
PubMed1988

Sterility and efficiency of two methods of cardiac output determination: closed loop and capped syringe methods.

A prospective randomized study was done to compare the fluid contamination rates of two methods used to determine cardiac output by thermodilution under in-use conditions. Fifty patients were randomly assigned to have cardiac output measured by the capped syringe or closed loop method, and were followed with quantitative cultures of fluid and catheter. The two treatment groups (n = 25 each) were comparable in terms of age, sex, intensive care unit location, underlying diagnosis, and mean number of cardiac output determinations performed in the first 24 hours after placement of the catheter line. No differences in the rates of fluid contamination were seen at any time between the two groups. The overall fluid contamination rate was 2/124 cultures (1.8% with 95% confidence interval +/- 4.1%) with one colony of Staphylococcus epidermidis from a closed loop sample and one colony of Pseudomonas maltophilia in a capped syringe sample. Although no difference in contamination rates was documented, the closed loop system required less nursing time and effort.

Adult↗
PubMed1983

Cardiac output, pulmonary hypertension, hypoxaemia and survival in patients with chronic obstructive airways disease.

A prospective study of cor pulmonale in 74 patients relates pulmonary haemodynamics to survival. Mean arterial oxygen tension (PaO2) was 7.2 +/- 0.14 kPa and mean arterial carbon dioxide tension (PaCO2) 6.6 +/- 0.12 kPa at entry. Pulmonary artery pressure (PAP), pulmonary vascular resistance (PVR), and cardiac output (CO) sitting and supine and where possible on exercise, were measured every one or two years by a floating catheter technique. Survivors showed very little change in pulmonary artery pressure, pulmonary vascular resistance or cardiac output. Those who did not survive, showed a steady increase of PAP and PVR, whether or not they had received continuous oxygen therapy at home. Cardiac output remained normal or slightly elevated despite increasing pulmonary artery pressure. The relationship between VO2 (minute oxygen consumption) and cardiac output remained within the normal or greater than normal range, even on exercise. Although a deteriorating clinical situation may be paralleled by changes in pulmonary haemodynamics, it is questioned whether such changes are causally implicated in mortality.

Cardiac Output↗
PubMed1981

The influence of ectopic beats and tachyarrhythmias on stroke volume and cardiac output.

The potentially adverse influence of premature ectopic beats or tachyarrhythmias on cardiac performance was studied by assessing the echocardiographic left ventricular stroke volume in 21 patients with cardiac rhythm disturbances. The beat to beat stroke volume correlated closely with end-diastolic volume in each patient (average R = .9). Premature ventricular contractions decreased stroke volume by an average of 48 +/- 8 ml (-71%) compared with sinus beats; whereas the postextrasystolic beats, although preceded by a pause and higher end-diastolic volume, increased stroke volume by only 16 +/- 7 ml (18%) over the sinus beats. Those postextrasystolic beats with equivalent timing and end-diastolic volume to the sinus beats had a mean stroke volume only 8 ml higher, suggesting that postextrasystolic potentiation plays only a minor role in augmenting stroke volume. Transient aberrant ventricular conduction of intermittent left bundle branch block, ectopic beats or atrial fibrillation failed to alter stroke volume. Ventricular bigeminy, trigeminy and quadrigeminy lowered cardiac output by 1.3, .9 and .7 l/min. The onset of tachyarrhythmias was oftentimes associated with a continuously changing end-diastolic volume and stroke volume, with either alternation or progressive increment of these variables. It is apparent that premature contractions decrease stroke volume by virtue of their infringement on diastolic filing, the principle beat to be determinant of stroke volume in arrhythmias being left ventricular end-diastolic volume. Since premature beats decrease stroke volume to an extent greater than postextrasystolic beats increase it, they may reduce cardiac output by a substantial degree, depending on their frequency of occurrence and degree of prematurity.

Arrhythmias, Cardiac↗
PubMedDate not supplied

Cardiac output monitoring: aortic transpulmonary thermodilution and pulse contour analysis agree with standard thermodilution methods in patients undergoing lung transplantation.

PURPOSE: The PiCCO System is a relatively new device allowing intermittent cardiac output monitoring by aortic transpulmonary thermodilution technique (Aorta intermittent) and continuous cardiac output monitoring by pulse contour analysis (Aorta continuous). The objective of this study was to assess the level of agreement of Aorta intermittent and Aorta continuous with intermittent (PA intermittent) and continuous cardiac output (PA continuous) measured through a special pulmonary artery catheter (Vigilance System SvO(2)/CCO Monitor) in patients undergoing single- or double-lung transplantation. METHODS: Measurements were obtained in 58 patients: at four time points in patients undergoing single-lung transplantation and at six time points in those undergoing double-lung transplantation. Bland and Altman and correlation analyses were used for statistical evaluation. RESULTS: We found close agreement between the techniques. Mean bias between Aorta intermittent and PA intermittent and between Aorta continuous and PA continuous was 0.18 L x min(-1) (2SD of differences between methods = 1.59 L x min(-1)) and -0.07 L x min(-1) (2SD of differences between methods = 1.46 L x min(-1)) respectively. Mean bias between PA continuous and PA intermittent and Aorta continuous and PA intermittent was 0.15 L x min(-1) (2SD of differences between methods = 1.39 L x min(-1)) and 0.08 L x min(-1) (2SD of differences between methods = 1.43 L x min(-1)). CONCLUSION: Measurements with the aortic transpulmonary thermodilution technique give continuous and intermittent values that agree with the pulmonary thermodilution method which is still the current clinical standard.

Aorta↗
PubMed2006

Cardiac output estimation with a new Doppler device after off-pump coronary artery bypass surgery.

OBJECTIVE: To compare cardiac output (CO), stroke volume (SV), and cardiac index (CI) as estimated with a new, noninvasive Doppler device (Ultrasonic Cardiac Output Monitor [USCOM]; USCOM Ltd, Sydney, Australia) with those measured with the bolus thermodilution (TD) technique. DESIGN: Prospective nonrandomized study. SETTING: Postcardiac surgery recovery unit of a tertiary cardiac center. PARTICIPANTS: Fifty patients after off-pump coronary artery bypass (OPCAB) surgery. MEASUREMENT AND MAIN RESULTS: Both right-sided and left-sided CO were estimated with a USCOM continuous-wave (CW) Doppler device, and CO was determined with the bolus TD technique performed in triplicate. On comparing the right-sided CO, SV, and CI with those of TD, the mean bias was 0.03 L/min, 1.6 mL, and 0.02 L/min/m(2), respectively. The comparison of left-sided CO, SV, and CI with those of TD revealed a means bias of 0.14 L/min, 1.0 mL, and 0.08 L/min/m(2), respectively. CONCLUSION: This study showed excellent agreement between the values for CO, SV, and CI as determined with USCOM and TD. Since there was only 1 time period for CO estimation in each patient with both methods, the stability of this correlation needs to be further investigated over time.

Adult↗
PubMed1997

The new pulmonary artery catheters: continuous venous oximetry, right ventricular ejection fraction, and continuous cardiac output.

OBJECTIVE: To review the literature addressing the new pulmonary artery catheters: continuous venous oximetry, right ventricular ejection fraction, and continuous cardiac output. DATA SOURCE: All pertinent English language literature dealing with new pulmonary artery catheters were retrieved from 1981 through 1996. STUDY SELECTION: Articles were chosen for review if the primary objective of the paper was study or review of technology related to new pulmonary artery catheters. DATA EXTRACTION: From the literature selected, information was obtained about continuous venous oximetry, right ventricular ejection fraction, and continuous cardiac output catheters. DATA SYNTHESIS: When pulmonary artery catheterization is used, continuous venous oximetry catheters may be considered for use when it is anticipated that therapy will be based upon oxygen transport end points. When pulmonary artery catheterization is used, right ventricular ejection fraction catheters may be considered for use when the anticipated therapy will be based upon evaluation of ventricular preload and when central venous pressure and/or pulmonary artery occlusion do not accurately reflect preload. When pulmonary artery catheterization is used, continuous cardiac output catheters may be considered for use in titration of interventions employed to alter stroke volume. CONCLUSION: Clinician misinterpretation and misapplication of the data appear to be the greatest impediment to using pulmonary artery catheterization to alter pathophysiologic processes and improve outcome in critically ill patients. Future research should first document effectiveness or lack of effectiveness of the "standard" pulmonary artery catheter (PAC). Pending these results, outcome and cost/benefit studies should be performed comparing "standard" with new PACs.

Cardiac Output↗
PubMed1995

Continuous measurement of cardiac output during aortic cross-clamping by the oesophageal Doppler monitor ODM 1.

We have compared the Doppler against the thermodilution technique for measurement of cardiac output in six patients during aortic surgery. The correlation coefficient between the two methods was between 0.76 and 0.84 during the different periods of the operation. Using the integral nomogram instead of direct calibration, the Doppler system underestimated cardiac output in atherosclerotic patients. However, the Doppler method did register accurately significant changes in cardiac output.

Aged↗
PubMed2005

[Measurement of cardiac output].

Diagnosis and therapy of hemodynamic instability are of the utmost importance in the treatment of critically ill patients during surgery and in intensive care. For both diagnosis and therapy, adequate and preferably continuous hemodynamic monitoring is essential. Besides the assessment of cardiac preload and blood pressure, cardiac output represents an important clinical marker of cardiac performance and global perfusion. Since its clinical introduction by Swan and Ganz in 1970, the standard technique for measuring cardiac output has been the pulmonary arterial thermodilution technique using a pulmonary artery catheter. The ongoing discussion on the risk-benefit ratio of such a pulmonary artery catheter has led to the introduction of several less invasive methods for determining cardiac output. The aim of this review is to provide background information on these alternative methods and to discuss the individual advantages and disadvantages of each method in the context of their clinical applicability.

Algorithms↗
PubMed1987

Redistribution of cardiac output after hypothalamic lesions and hemorrhage.

The effects of ablation of the anteroventral portion of the third cerebral ventricle (AV3V) on cardiac output and distribution of regional blood flows were determined in conscious rats using 15 micron radiolabelled microspheres before, and 2 min and 15 min after hemorrhage (n = 11 for each group). Prior to hemorrhage, cerebral blood flow was significantly greater (216 +/- 30 ml/min/100 g), and cerebral vascular resistance was lower (0.60 +/- 0.09 mm Hg/ml/min/100 g) in rats with AV3V lesions than in control-operated animals (132 +/- 16 ml/min/100 g; 0.92 +/- 0.1 mm Hg/ml/min/100 g, respectively), while mean arterial blood pressure, cardiac output, and regional blood flow to other organs were similar. Less blood was withdrawn from animals with AV3V lesions (4.4 +/- 0.6 ml) than from control-operated rats (6.0 +/- 0.5 ml) to reduce blood pressure to approximately 65 mm Hg. Hemorrhage decreased cerebral vascular resistance in control-operated animals (0.52 +/- 0.07 mm Hg/ml/min/100 g), but not in rats with AV3V lesions (0.48 +/- 0.1 mm Hg/ml/min/100 g). Cardiac output and regional blood flow to other organs were similar between rats with AV3V lesions and control-operated animals following hemorrhage. These data demonstrate that electrolytic ablation of the AV3V region results in a selective increase in cerebral blood flow and decreased cerebral vascular resistance, but does not alter the reflex changes in regional blood flow evoked by hemorrhage.

Animals↗
PubMed1975

Blood viscosity and cardiac output in acute experimental anemia.

The significance of blood viscosity alterations during anemia was evaluated in dogs under morphine-chloralose anesthesia. In group I, anemia (mean hematocrit 18.1 +/- 1.3 vol %) was produced by exchange transfusion with clinical dextran (avg mol wt 70,000). In group II, anemia was produced (mean hematocrit 19.9 +/- 0.88 vol %) with 500,000 molecular weight dextran, thus preventing the decrease in blood viscosity in group I. The cardiac output increase in group I (93.4%) with low-viscosity anemia was significantly greater than in group II (43.3%) with unchanged blood viscosity. Group III animals were transfused with a clinical dextran-red cell mixture, and group IV animals received a 500,000 mol wt dextran-red cell mixture. In group III, blood viscosity and cardiac output did not change. In group IV, blood viscosity rose and cardiac output fell significantly. The results suggest that a change in blood viscosity exerts a significant effect upon cardiac output, especially during acute dextran-exchange anemia.

Anemia↗
PubMed1999

Kinetics of oxygen uptake at onset of exercise related to cardiac output, but not to arteriovenous oxygen difference in patients with chronic heart failure.

Patients with chronic heart failure performed exercise tests to evaluate the relation of kinetics of oxygen uptake to cardiac output and arteriovenous oxygen difference at the onset of exercise. The kinetics of oxygen uptake are primarily determined by cardiac output; these kinetics are useful in evaluating exercise intolerance and cardiac output response during exercise.

Adult↗
PubMed1991

Evaluation of the Velcom-100 pulse Doppler cardiac output computer.

The use of Doppler ultrasound as a means of obtaining cardiac output (CO) measurements quickly, easily, and noninvasively has been made possible by recent technologic developments. We evaluated a new pulse Doppler ultrasonic unit (Velcom-100, Waters Instruments, Inc) in the Surgical Intensive Care Unit at the University of Michigan Medical Center. Accuracy of this device was determined by comparison of CO results obtained from the Velcom-100 (COV) against those of conventional thermal dilution cardiac output (COT) measurements. Twenty-six postoperative patients were used for this study, ranging in age from 20 to 82 years old. Initial studies prior to in vivo standardization demonstrated a significantly lower result (p = 0.039) for the Velcom-100 with a mean difference of 0.86 L/min (COT-COV). This comparison was significantly improved in subsequent studies following in vivo standardization (COT-COV = 0.02 L/min, p = 0.646). Linear regression analysis showed a significant, positive correlation between the two results (r = 0.82, p less than 0.05) indicating an excellent trending capability for the Velcom-100. Our evaluation found the Velcom-100 to be user friendly, allowing rapid training of ICU technicians and applicability for postoperative monitoring.

Adult↗
PubMed2001

[Coupling of cardiac output or systemic O2 transport and metabolism during catecholamine therapy].

Catecholamines increase cardiac output (CO) and thus systemic oxygen delivery, but they also increase the tissue's oxygen demand (thermogenic or calorigenic effect). Therefore, it is of particular interest for the choice of a catecholamine as to what extent CO is increased in relation to oxygen demand (VO2), because the tissue's oxygen balance is improved only if CO and thus oxygen delivery increases more than oxygen demand. For this purpose we reviewed the literature and analysed the relation between CO and VO2 during physiological as well as during pathological conditions. In particular, we compared the slopes of the regression lines of the individual CO/VO2-relation for each catecholamine. Dependent on study conditions, the extent of the increases in CO and VO2 varies substantially already for one and the same agent. During physiological conditions, the synthetic agents dobutamine and dopexamine primarily increase CO, whereas the endogenous ones epinephrine and particularly norepinephrine increase both CO and VO2 to about the same extent. During pathological conditions the literature is inconsistent, but it appears that the CO/VO2-relations do not differ substantially from those observed under physiological conditions. With due caution the current information implies that the synthetic catecholamines dobutamine and in particular dopexamine might be preferred in the treatment of low cardiac output states because they increase CO and thus oxygen delivery above the increase in metabolic demand.

Animals↗