SEARCH · Search PubMed

Results for “CARDIAC OUTPUT”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,189 records · Page 66Linked to original sources

PubMed1997

Indicator-dilution dispersion models and cardiac output computing methods.

The general theory of indicator-dilution methods provides a basis for computing improved cardiac output estimates. Interpretation is via indicator-dispersion modeling with Brownian motion of drifting particles. Detected curves indicate the distribution of passage times from the injection site: the local density random walk (LDRW) function of a Wiener process. Fitting the LDRW to 70 dye curves by nonlinear regression for examples, I show how all possible undistorted curves can, in principle, be simulated. I show via semilogarithmic plots that conventional exponential decay constructs systematically underestimate cardiac output by up to 8%. To help reconcile the predictions of LDRW-fitted dilution curves and contemporary practice, I show how curve-shape asymmetry (skewness) dramatically affects the enclosed areas. Mean transit times may overestimate blood volumes by 15-100% in very skewed thermodilution curves if the dispersion effects are overlooked. Triangle constructions, which accounted for hundreds of experimental findings, also have theoretical explanations. Curve-fitting methods reduce the extrapolation biases inherent in many computers and in any respiration-induced artifacts. Compatibility of cardiac output predictions from various dilution methods and modules becomes feasible.

Artifacts↗

PubMed1980

Noninvasive measurement of cardiac output during laparoscopy.

With the use of noninvasive transthoracic impedance cardiography we have demonstrated a consistent fall in stroke volume and cardiac output without significant clinical changes in heart rate in anesthetized patients undergoing laparoscopy. Cardiac output fell to a mean value of 60% in 14 patients undergoing laparoscopy and by a mean value of 6% in four patients undergoing laparotomy. The intraabdominal pressure did not exceed 20 torr in any laparoscopy patient. Some unexplained cardiac arrests during laparoscopy in healthy females may be caused by impaired venous return due to the increased intraabdominal pressure of pneumoperitoneum. Lethal values of cardiac output could result. The routine use of transthoracic impedance cardiography would alert the anesthesiologist to a dangerous situation that cannot be determined by current routine monitoring practice.

Abdomen↗

PubMed2002

Reliability of new and old Doppler echocardiographic indexes of the severity of aortic stenosis in patients with a low cardiac output.

BACKGROUND: In addition to the conventional "flow-corrected" parameters (continuity equation and aortic valve resistance), new and simpler Doppler echocardiographic indexes of the severity of aortic stenosis have recently been introduced. These measures can be classified as "function-corrected" indexes (fractional shortening-velocity ratio and ejection fraction-velocity ratio) and "pressure-corrected" indexes (percent stroke work loss). Little information however is available about the diagnostic accuracy of each of these parameters in identifying patients with severe aortic stenosis in low-flow states, in which the diagnosis and clinical decision-making are more difficult and challenging. METHODS: We analyzed 161 patients with aortic stenosis (96 males, 65 females, mean age 68 +/- 9 years) and a low cardiac output (thermodilution cardiac index < or = 2.5 l/min/m2). All patients underwent both cardiac catheterization and echocardiography within 48 hours one of the other. The invasive Gorlin valve area was used as gold standard (severe aortic stenosis = Gorlin < or = 0.8 cm2). Echocardiographic indexes were assessed by an investigator who was unaware of the hemodynamic findings. RESULTS: The mean Gorlin aortic valve area was 0.7 +/- 0.3 cm2; cardiac catheterization allowed the identification of 129 patients with severe aortic stenosis and of 32 with mild-to-moderate aortic stenosis. The diagnostic accuracy of the Doppler gradient alone was low (sensitivity 55%). The best linear correlation with the Gorlin value was found using the "function-corrected" ejection fraction-velocity ratio (r = 0.85). Similarly, the best combination of sensitivity and specificity in identifying patients with severe aortic stenosis, as assessed by cardiac catheterization, was observed using the ejection fraction-velocity ratio (sensitivity 87%, specificity 88%). CONCLUSIONS: In patients with aortic stenosis and a low cardiac output, the "function-corrected" ejection fraction-velocity ratio offers the better diagnostic accuracy, as compared with the cardiac catheterization valve area calculation.

Aged↗

PubMed1988

Determination of cardiac output by single gated pulsed Doppler echocardiography.

The aim of the study was to evaluate the use of single gated pulsed Doppler cross-sectional echocardiography for measurement of the cardiac output. Pulsed Doppler echocardiography was used to assess both area and blood velocity at the aortic orifice. Stroke volume estimates were determined by multiplying area by systolic time velocity integral as measured from the parasternal and apical approach, respectively. We investigated a group of 17 healthy individuals and a group of 20 patients with coronary artery disease. In the first group no change was found in aortic area during systole (P less than 0.01). During a follow-up of two weeks no change in aortic area was observed either (P less than 0.01). Intraobserver, interobserver and day-to-day variability of the aortic area, expressed as the coefficient of variation was 3.6 +- 5.2%, 4.6 +- 5.7% and 7.8 +- 3.8% (mean +- 1 SD), respectively. The interobserver variability of the time velocity integrals was 6.0 +- 6.2%. In the second group the cardiac output as measured with the thermodilution method ranged from 3.8 to 8.0 l/min. Comparison of the Doppler and thermodilution technique for measurement of cardiac output showed a correlation coefficient of r = 0.76 (P less than 0.001) and the following regression equation: CO (Doppler) = 1.0 x CO (thermodilution)-700 ml. The Doppler method underestimated cardiac output relative to the thermodilution method.

Adolescent↗

PubMed1990

Repeatability of the acetylene rebreathing method in measuring cardiac output: influence of acetylene concentration.

The acetylene rebreathing method is a reliable noninvasive method for estimation of cardiac output. However, the method is not commonly used for clinical purposes. This is due mainly to the fact that acetylene is explosive at concentrations above 2% and that acetylene at concentrations above 0.5% has an unpleasant taste. In the present study we have investigated whether it is possible to reduce the concentration of acetylene to 0.3% in the rebreathing bag without degrading the repeatability of the estimated cardiac output. The problem was elucidated theoretically and experimentally. A theoretical investigation was carried out by producing an acetylene rebreathing curve from a single alveolus lung model. The theoretical study showed that the random noise arising from the gas analyzer gives rise to less than 10% of the total variation of the estimated cardiac output. The results of the experimental study showed that it is possible to reduce the acetylene concentration to 0.3% without decreasing the reproducibility of the acetylene rebreathing method.

Acetylene↗

PubMedDate not supplied

Cardiac output monitoring by echocardiography: should we pass on Swan-Ganz catheters?

Transesophageal echocardiography offers a noninvasive technique for the continuous monitoring of cardiac performance. The combination of 2-dimensional echocardiography and Doppler velocitometry provide assessment of cardiac anatomy, valve function and, ventricular loading conditions. Although transesophageal echocardiography has become accepted for perioperative monitoring, it is typically used in conjunction with Swan-Ganz catheterization. To supplant Swan-Ganz catheters, an echocardiographic technique to monitor cardiac output is necessary. Despite considerable effort to achieve this goal, a satisfactory technique has been difficult to realize. This paper discusses the role of cardiac output monitoring in perioperative care and critically examines echocardiographic techniques for cardiac output monitoring.

Cardiac Output↗

PubMed2000

Exercise-induced QTc-interval changes for predicting improvement in regional blood flow in ischemic myocardium and cardiac output after coronary angioplasty in patients with right bundle-branch block.

BACKGROUND: We have previously shown that QT-interval changes are more useful than ST-T changes in evaluating the severity of exercise-induced myocardial ischemia in patients with right bundle-branch block (RBBB). HYPOTHESIS: The purpose of this study was to evaluate whether the improvement in regional myocardial blood flow (RMBF) in ischemic areas and cardiac output after percutaneous transluminal coronary angioplasty (PTCA) can be predicted by exercise-induced QT-interval changes prior to PTCA. METHODS: The RMBF and cardiac output were quantified with nitrogen-13 ammonia positron emission tomography at rest and during exercise in 20 patients with RBBB and ischemic heart disease before and 6 months after PTCA, and in 9 healthy volunteers. RESULTS: Before PTCA, exercise-induced prolongation by < 20 ms or shortening of the Bazett-corrected QT (QTc) interval (454 +/- 38 to 451 +/- 41 ms, p = NS) was observed in 13 patients (Group 1) and prolongation by > or = 20 ms (429 +/- 44 to 466 +/- 50 ms, p < 0.002) was observed in 7 (Group 2). The number of regions of exercise-induced ischemia was significantly greater in Group 2 than in Group 1 (4.0 +/- 1.2 vs. 2.1 +/- 1.2, p < 0.01). The RMBF in regions of exercise-induced ischemia and cardiac output at rest was not significantly different between Groups 1 and 2, whereas during exercise both the parameters were significantly lower in Group 2 than in Group 1 (both p < 0.05). After successful PTCA, RMBF both at rest and during exercise improved significantly in Group 1 (0.67 +/- 0.04 to 0.71 +/- 0.06 ml/min/g, 0.74 +/- 0.05 to 0.84 +/- 0.08 ml/min/g; both p < 0.0001), but did not improve significantly in Group 2 (0.63 +/- 0.05 to 0.65 +/- 0.07 ml/min/g, 0.65 +/- 0.04 to 0.69 +/- 0.11 ml/ min/g; both p = NS). Cardiac output during exercise improved significantly in Group 1 (6.4 +/- 0.7 to 7.4 +/- 0.9 l/min; p < 0.002) but not in Group 2 (5.7 +/- 0.6 to 5.9 +/- 0.6 l/min; p = NS). CONCLUSIONS: Our results suggest that the marked prolongation of the QTc interval induced by pre-PTCA exercise may predict a lack of improvement in RMBF in ischemic areas and cardiac output after PTCA in patients with RBBB and ischemic heart disease.

Adult↗

PubMedDate not supplied

[Measurement of cardiac output by thermodilution with a diode as a temperature sensor].

An area integrator for the thermodilution curve in cardiac output measurement is described. A new temperature sensor is used, a diode with some advantages over the thermistor normally used. The main advantages are: easy calibration and replacement, and broad range of linearity. The cardiac output values obtained in dog with the integrator follow a linear relationship with those of the flowmeter. In simultaneous measurements the correlation is R = 0.96. Using a diode as temperature sensor a modification of the Steward Hamilton equation (used for thermistor) is necessary. With this new equation a monogram is performed to calculate the cardiac output from the area given by the numerical integrator.

Animals↗

PubMed1985

[Analysis of the factors affecting cardiac output in exclusion of the sino-carotid reflexogenic area].

In acute experiments on cats, the character and mechanisms of changes of the heart pumping function were studied in suppression of the carotid sinus baroreceptors with occlusion of the carotid arteries. In 65% of tests the cardiac output was reduced. Changes of venous return, at that, were diverse and opposite to those of the cardiac output in 50% of observations. Neither vagotomy, nor blockade of beta-adreno- and M-cholinoreceptors affected the character of cardiac output changes. The role of maximal responses of arterial pressure in forming of the cardiac output shifts in sino-carotid reflex, is discussed.

Animals↗

PubMed1976

Cardiac output determination by simple one-step rebreathing technique.

We have developed a rebreathing technique for measuring cardiac output in resting or exercising subjects. The data needed are the subject's CO2 dissociation curve, the initial volume and CO2 fraction of the rebreathing bag, and a record of CO2 at the mouth during the maneuver. From these one can obtain all the values required to solve the Fick equation. The combined error due to inaccuracy in reading the tracings and to the simplifying assumptions was found to be small (mean = 0.5%, SD ;.5%). Cardiac output values determined with this technique in normal subjects were on the average 2% higher than those obtained simultaneously with an acetylene rebreathing method (n = 49, SD = 11%). Among the advantages of the technique are that it requires analysis of a single gas, takes less than thirty seconds per determination, allows one to obtain repeated measurements at rapid intervals, is not affected by the ability of lung tissue to store CO2, and eliminates many of the assumptions usually made in non-invasive measurements of cardiac output.

Acetylene↗

PubMed1979

A comparison between the transthoracic electrical impedance method and the direct Fick and the dye dilution methods for cardiac output measurements in man.

In fourteen patients referred for preoperative evaluation of heart disease we compared the transthoracic electrical impedance method to the direct Fick (four patients) and dye dilution methods (ten patients) for estimation of cardiac output. On statistical analysis of paired differences we found no reliable agreement between the absolute impedance values and the reference methods. The reproducibility was, however, acceptable, and the coefficient of variation for impedance cardiac output was 7.8%, and for impedance stroke volume 7.6%. Our conclusion is that in patients with advanced heart disease cardiac output cannot be determined with accuracy with the impedance cardiographic method. In clinical practice this must be considered so important, that we hesitate to use the method for monitoring cardiac output in critically ill patients even if the reproducibility for individual changes is acceptable.

Adult↗

PubMed1988

Accuracy of an indirect carbon dioxide Fick method in determination of the cardiac output in critically ill mechanically ventilated patients.

We evaluated the accuracy of an indirect CO2 Fick method for measuring cardiac output in 30 critically ill mechanically ventilated patients. When the Fick principle was applied to CO2 using estimated PaCO2, the cardiac output obtained underestimated the thermodilution technique showing a lack of accuracy. However, there was a significant correlation between thermodilution and CO2 rebreathing methods using measured (r = 0.92; p less than 0.001) and estimated (r = 0.60; p less than 0.01) arterial PCO2. The regression equation using measured arterial PCO2 was y = 0.59 + 0.91x, and for estimated arterial PCO2 was y = 1.7 + 0.33x. The results suggest that the CO2 rebreathing method using measured arterial PCO2 may be useful to determine cardiac output in those seriously ill patients on artificial ventilation not requiring right heart catheterization.

Adult↗

PubMed2004

Cardiac output monitoring during off-pump coronary artery bypass grafting.

OBJECTIVE: To evaluate and compare monitors of cardiac output during repositioning and stabilization of the heart for off-pump coronary artery bypass (OPCAB) surgery. DESIGN: Prospective, observational, clinical study. SETTING: University teaching hospital. PARTICIPANTS: Consecutive patients scheduled to undergo elective OPCAB (n = 19). INTERVENTIONS: Monitoring, induction, and anesthesia followed a routine protocol for coronary artery bypass patients. This included the use of transesophageal echocardiography (TEE) and pulmonary artery catheter placement. MEASUREMENTS AND MAIN RESULTS: After positioning and stabilization for OPCAB surgery, the changes in descending aortic flow velocity (VTI) times heart rate (HR) and the mixed venous oxygen saturation (SvO(2)) could be used to predict the changes in thermodilution cardiac output (TDCO) using the following model: deltaTDCO((calc))=-13.15+0.35(deltaVTI*HR)+0.61(deltaSvO(2)) where Delta indicates the percentage change from baseline values. The changes in mean arterial pressure, mean pulmonary artery pressure, and continuous cardiac output did not correlate with the changes in TDCO. CONCLUSION: The use of the VTI*HR, as determined by TEE, in addition to the SvO(2) can strengthen clinical decision making during repositioning and stabilization of the heart during OPCAB. Changes in the VTI*HR and SvO(2) can be used as surrogate markers for changes in CO during OPCAB surgery.

Aged↗

PubMed1995

Normal stroke volume and cardiac output response during dobutamine stress echocardiography in subjects without left ventricular wall motion abnormalities.

Dobutamine stress echocardiography has become widely utilized for evaluation of coronary artery disease, but the expected responses of stroke volume and cardiac output to the high doses of dobutamine administered in these studies are not known. To determine these responses, stroke volume and cardiac output were measured with 2-dimensional Doppler echocardiography at each stage of dobutamine stress echocardiography and after administration of atropine in 47 patients without resting or inducible wall motion abnormalities. Heart rate increased significantly at each stage of dobutamine infusion and after atropine. Mean blood pressure decreased at the 5 micrograms/kg/min dose, then showed little change. Stroke volume increased 27 +/- 18% from baseline, with significant increases occurring at both the 5 and 10 micrograms/kg/min doses (p < 0.00001). With higher doses of dobutamine, stroke volume tended to plateau or decrease. Mean changes in stroke volume were not significant between the doses of 10, 20, and 30 micrograms/kg/min. The mean change in stroke volume from the 30 to the 40 micrograms/kg/min dose was a significant decrease of 6.3% (p = 0.004); the decrease from the 40 micrograms/kg/min dose to atropine approached statistical significance (p = 0.06). Cardiac output increased throughout dobutamine infusion. Stroke volume during dobutamine stress echocardiography is commonly maximum at a dose of 20 micrograms/kg/min and tends to decline at higher infusion rates. At higher doses, increases in cardiac output are mediated primarily by increases in heart rate.

Aged↗

PubMed1992

Prediction of post-cardiopulmonary bypass cardiac output by venous oximetry.

The present study evaluates two equations for predicting the post-cardiopulmonary bypass cardiac output (CO) in 10 patients undergoing coronary artery bypass grafting. One equation is based on the relationship of CO with mixed venous oxygen saturation (SVO 2), while the second equation is based on the relationship with oxygen extraction (1 - SVO 2). Each patient served as his own control. During bypass, when the patients were normothermic and perfused with a pump flow of 2.4 L/min/m 2, the SVO 2 was monitored by an in-line Bentley oxystat Meter. Just before termination of bypass, the pump flow was decreased to 0.4 L/min/m 2 and the left atrial pressure was increased to 10-15 mmHg; the resulting SVO 2 was recorded. The post-bypass CO was predicted in every patient by the two equations. Immediately after weaning from bypass, the cardiac output was measured by thermodilution. The thermodilutional CO measurement was correlated with the CO predicted by the two equations. Correlation analysis suggests that CO prediction is more accurate and approaches the 1:1 ratio when the calculation of predicted CO is based on the relationship between cardiac output and oxygen extraction.

Adult↗

PubMed1978

Effects of intravenous vasopressin on canine mesenteric arterial blood flow, bowel oxygen consumption, and cardiac output.

The effects of various doses of intravenous vasopressin on mesenteric arterial blood flow, intestinal oxygen consumption, and cardiac output in anesthetized dogs were investigated. Optimal dose rate of intravenous vasopressin was found to be 3.0 mU/kg/min. At this dose rate, mesenteric arterial blood flow, intestinal oxygen consumption, and cardiac output decreased by 57%, 57% and 26%, respectively. Increasing the dose rate to 8.0 mU/kg/min did not offer significant gains. Maximum effect was observed 20 min after the beginning of the infusion. The effects disappeared 10-20 min after the infusion was discontinued, with the exception of superior mesenteric blood flow which showed a rebound increase. We conclude that in the anesthetized dog, intravenous infusions of vasopressin at low dose rates (3.0 mU/kg/min) substantially reduce mesenteric blood flow and intestinal oxygen extraction with moderate reduction of cardiac output. Possible clinical applications of low dose intravenous infusions of vasopressin would include reduction of portal hypertension and bowel protection during radiation therapy.

Animals↗

PubMed1986

Leukocytosis of exercise: role of cardiac output and catecholamines.

The effect of propranolol (5 mg iv) on the leukocytosis of exercise was studied in seven normal young males. Leukocyte counts, plasma norepinephrine (NE), epinephrine (E), and cardiac output were measured at rest and in the steady state of several submaximal work loads when subjects exercised on a cycle ergometer. The results in control experiments were compared with those obtained on a different day with propranolol. Propranolol decreased heart rate at all work loads (P less than 0.001) but had no effect on the increase in cardiac output at increasing work loads. Plasma NE and E levels were similar at rest and in exercise in control and propranolol studies. There was no effect of propranolol on the increase in leukocyte counts with increasing work loads. Although propranolol did not affect the increase in total leukocyte count, the increase in lymphocyte count at higher work loads was less with propranolol. We conclude that the demargination of leukocytes from the pulmonary circulation in exercise is probably a mechanical effect of the increase in cardiac output. However, we have not excluded a contribution from a humoral event that would decrease the adherence of leukocytes to endothelium during exercise. The smaller increase in lymphocytes at higher work loads in the presence of propranolol suggests that catecholamines affect the lymphocyte count over and above their effect on cardiac output.

Adult↗

PubMed1996

Long-term recording of cardiac output via an implantable haemodynamic monitoring device.

Long-term monitoring of central haemodynamics with implanted monitoring systems might be valuable in managing heart failure patients. Such systems offer an opportunity for repeated 'semi-invasive' cardiac output determinations according to the Fick principle. Five patients, four with chronic heart failure and one with chronic pulmonary disease, underwent supine exercise testing during cardiac catheterization at 0, 2, 6 and 11 months after implantation of a right ventricular mixed venous oxygen saturation sensor connected to an implantable haemodynamic monitor. The monitor provided a continuous measure of oxygen saturation via a radio-telemetry link to a metabolic cart capable of measurement of breath-by-breath oxygen consumption. Cardiac output was computed using oxygen consumption, mixed venous oxygen saturation, arterial oxygen saturation by pulse oximetry and haemoglobin oxygen capacity. Biosensor-derived oxygen saturation compared to blood samples from the pulmonary artery showed an excellent correlation over time, r2 = 0.94 (implant), r2 = 0.91 (6-11 months). There was a strong correlation between semi-invasive-determined cardiac output using the biosensor and the invasive technique, which persisted over the entire follow-up period. Repeated semi-invasive cardiac output measurements using an implanted haemodynamic monitoring system in chronic heart failure patients is feasible and the data may be of value for optimizing therapy.

Adult↗