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PubMed1977

Studies on methods for determination of the distribution of cardiac output in the mouse.

Different techniques for determining cardiac output distribution in the mouse have been studied. The soluble indicator technique using injection of rubidium on the right side of the heart was found to give a satisfactory reproducibility which made it possible to determine cardiac output fractions in the normal mouse. The use of radioactivity-labelled microspheres, which must be injected on the side of the heart, was found to give unreliable and non-reproducible results. This was due to difficulty in depositing the microspheres into the left ventricle both when a catheter was inserted via the right carotid artery, or by means of cardiac puncture.

Animals↗
PubMed1992

Haemodynamic changes associated with thermodilution cardiac output determination during myocardial ischaemia or pulmonary oedema in dogs.

Since the technique of thermodilution (TD) cardiac output measurements per se causes haemodynamic alterations, the authors examined whether the alterations elicited by iced injectate are augmented in the presence of myocardial ischaemia (MI) or pulmonary oedema (PE), compromised conditions frequently associated with critically ill patients. MI (N = 7) or PE (N = 7) was induced by clamping the anterior descending coronary artery or by a slow infusion of oleic acid into the right atrium, respectively, in anaesthetized dogs. Injection of iced injectate, 3 ml, caused similar changes in heart rate, mean systemic and pulmonary arterial pressures, pulmonary blood flow, right ventricular dP/dt, and right atrial pressure in dogs with and without MI or PE. Cardiac output estimated by TD correlated closely with pulmonary blood flow measured by electromagnetic flowmeter in both MI and PE (r > 0.9). No profound alterations in haemodynamics were observed at any injection during TD cardiac output measurements under MI or PE. These results indicate that TD cardiac output determination does not cause serious haemodynamic alterations, and can estimate right ventricular output accurately under MI and PE.

Animals↗
PubMed1989

Continuous cardiac output determination using transtracheal Doppler: initial results in humans.

Transtracheal Doppler, a procedure developed in the authors' laboratory, provides an estimate of cardiac output in endotracheally intubated dogs. The present study reports initial results in humans with a Doppler probe incorporated into an endotracheal tube. The system was first calibrated by empirically determining phi, the angle of the ultrasound beam with respect to the blood velocity vector. For a best least squares fit for phi, aortic diameters can be calibrated over a range of 22-37 mm. The calibration was then tested in a separate group of patients using the same empirically derived angle to calculate cardiac outputs. The transtracheal Doppler cardiac outputs show good correlation with those obtained by thermodilution over a range of cardiac outputs, 2.69-8.62 1/min, R2 = 0.835.

Adolescent↗
PubMed1978

Cardiac output and uterine blood flow in the pregnant ewe.

Fifteen pregnant ewes were studied to determine what fractions of the increases in maternal cardiac output and oxygen consumption found in pregnancy were due to the concomitant increases in blood flow to and oxygen consumption of the uterus and its tissue contents. Maternal cardiac output rose at term to 6.65 +/- 0.47 L. per minute, a value 40 per cent above the postpartum level. Uterine blood flow, which had increased at term to 1.62 +/- 0.15 L. per minute, represented 24 per cent of maternal cardiac output above postpartum levels. Maternal oxygen consumption at term was 259 +/- 11 c.c. per minute, a value 33 per cent above the postpartum level. Uterine oxygen consumption, which had increased at term to 57 +/- 4 c.c. per minute, represented 22 per cent of maternal oxygen consumption and accounted for 87 per cent of the increase in maternal cardiac output above postpartum levels. These data indicate that in the ewe most of the pregnancy-associated increases in maternal cardiac output and oxygen consumption are due to the demands of the uterus and its tissue contents.

Animals↗
PubMed1976

[Pathogenesis of the low cardiac output syndrome in postreanimation states].

Functional reserves of the cardiovascular system during sharp depression of the cardiac output in the postreanimation period after 15-minute cardiac arrest were studied in experiments on dogs (by loading with different fluid volumes). Acute hypervolemia did not produce any circulatory decompensation. Reinforcement of venous return and changes in the peripheral circulation due to polyglucine loading augmented the CVP temporarily, and produced a stable increase of the AP, of the cardiac output, systolic volume, the work of the left cardiac ventricle and of the total oxygen consumption by the organism. Meanwhile there was a decrease of the peripheral vascular resistance. In model experiments on dogs, which sustained 20-minute isolated compression ischemia the syndrome of low cardiac output developed too. This indicated the relation of this phenomenon to the disorders in the neuro-humoral regulation of blood circulation.

Animals↗
PubMed1991

Transesophageal Doppler cardiac output monitoring: performance during aortic reconstructive surgery.

Transesophageal Doppler (TED) monitoring provides continuous, noninvasive monitoring of cardiac output by measurement of aortic flow velocities. Because of the effects on aortic flow dynamics resulting from atherosclerosis, aortic cross-clamping, and wide variations in arterial blood pressure, the validity of TED monitoring during aortic surgery is unresolved. The authors prospectively evaluated a second-generation TED cardiac output monitor in 42 patients undergoing aortic reconstructive surgery. Four hundred eighty-nine simultaneous measurements of TED and thermodilution cardiac output were obtained. Transesophageal Doppler measurements were highly correlated to thermodilution measurements (R = 0.94); however, Bland-Altman analysis revealed a moderate error in the TED measurements (2 SD of the bias = 1.4 L/min). Trending analysis showed that TED monitoring accurately tracked changes in thermodilution cardiac output. Placement of an aortic cross-clamp resulted in significant reductions in the accuracy of Doppler measurements. Arterial blood pressure variations did not systematically affect the accuracy of the transesophageal technique. Limitations of TED monitoring, including a difficult calibration procedure, poor performance during aortic cross-clamping, and the need for probe repositioning, suggest further development is warranted.

Aorta, Abdominal↗
PubMedDate not supplied

Improvements in determination of cardiac output with a Swan-Ganz catheter.

The time constant for heat transfer may affect exact determination of cardiac output with Swan-Ganz catheters. Commercially available Swan-Ganz catheters are provided with thermistors with varying time constants. Current monitoring of cardiac output is not corrected for these time constants, so the conventional method of determining cardiac output using the equation of Stewart-Hamilton produces marked errors. The authors propose a new method of determining cardiac output with Swan-Ganz catheters with varying time constants from thermal dilution curve data based on Newton's cooling law. Values for blood flow rate determined by the new method using a completely stirred tank of original design, mimicking the natural heart and using bovine blood, are almost the same as values observed at varying saline infusion volumes, saline temperatures, and saline infusion times.

Blood Flow Velocity↗
PubMedDate not supplied

Oxygen uptake and cardiac output during progressive and constant load work in patients after acute myocardial infarction.

PURPOSE: Simultaneously measured oxygen uptake (VO2) and Doppler echocardiography could verify if an alteration in the VO2 response to progressive and constant load work is due to reduced cardiac output. METHODS: The study group consisted of nine patients after acute myocardial infarction (MI), five age-matched healthy subjects (HE), and five young well-trained subjects (WT). Each subject performed a progressive exercise test and two bouts of constant load work at power outputs equated to 10% below (W1) and 10% above (W2) their ventilatory thresholds. VO2 and cardiac output were measured continuously and simultaneously during the tests. RESULTS: VO2 was significantly reduced for the MI group during the initial stages of the progressive exercise test (P < .02) and remained lower throughout the entire test. During the first 60 seconds of constant load work (W2), VO2 was lower for MI (P < .05). At steady state exercise during W2, cardiac output was significantly less for MI (P < .05). VO2 for the MI group was more reliant on cardiac output during lower power outputs and differences in the arterial and venous O2 content (a-VO2 difference) during greater power outputs. CONCLUSIONS: Cardiac rehabilitation programs must be aware of this delayed VO2 and cardiac output response when setting training workloads or selecting the magnitude of the workload increments during progressive exercise tests.

Adult↗
PubMed2006

Cardiac output measurement during infrarenal aortic surgery: echo-esophageal Doppler versus thermodilution catheter.

OBJECTIVE: Aortic surgery is associated with various hemodynamic and cardiac output modifications. These disorders may be partly caused by blood flow redistribution between supra-aortic and descending aorta regions during clamping and unclamping. A new echo-esophageal Doppler (Hemosonic 100; Arrow, Reading, PA) calculates cardiac output from a simultaneous measurement of blood flow velocity and diameter of the descending aorta. This calculation may be affected by blood redistribution during aortic clamping. The aim of this study was to compare cardiac output measured by echo-esophageal Doppler and by bolus thermodilution catheter during infrarenal aortic surgery. DESIGN: Prospective, observational study. SETTING: University hospital, single institution. PARTICIPANTS: Twenty-two adult patients. INTERVENTIONS: Infrarenal aortic surgery. MEASUREMENTS AND MAIN RESULTS: Cardiac outputs monitored by both devices were highly correlated during the whole surgical procedure (r2 ranging from 0.54 to 0.76). Bland and Altman analysis showed absence of significant bias before and after clamping (ranging from 0.1 +/- 0.73 L/min to 0.18 +/- 1 L/min, p > 0.05) and a significant bias of 0.5 +/- 1.05 L/min (p < 0.05) during aortic clamping. Limits of agreement did not differ significantly during the whole surgical procedure (ranging from -1.36/2.19 to -2.23/2.49). During clamping and unclamping, changes in cardiac output obtained by both methods were positively correlated (r2 = 0.7). CONCLUSIONS: Bias between both methods was clinically acceptable, and limits of agreement were not significantly modified by aortic clamping. However, larger studies including homogenous aortic pathologies are necessary to validate this method during infrarenal aortic surgery.

Aged↗
PubMed1994

Determination of cardiac output using acoustic quantification in critically ill patients.

The reliability of automated acoustic quantification (AQ) in yielding real-time left ventricular (LV) area, volume, and ejection fraction has been validated. The purpose of this study was to explore the potential of AQ in providing accurate immediate determination of cardiac output in critically ill patients. A total of 48 patients were studied. One group consisted of 37 critically ill patients with indwelling Swan-Ganz catheters. In these patients, cardiac output by AQ, manual tracing of end-diastolic and end-systolic frames of 2-dimensional images, and thermodilution were measured. AQ was also compared with Doppler calculation of flow through the left and right ventricles in 11 additional patients. Adequate data for calculation of cardiac output with AQ were obtained in 78% of critically ill patients. There was an excellent correlation between AQ and off-line manual analysis for LV volumes (r = 0.94 and 0.91 for end-diastole and end-systole), ejection fraction (r = 0.85), and cardiac output (r = 0.93). AQ also correlated well with Doppler analysis (r = 0.97) and thermodilution technique (r = 0.95) in the determination of cardiac output. However, AQ slightly underestimated thermodilution measurements, with rather wide limits of agreement (-0.3 +/- 1.1 liter/min). There was a similar underestimation of cardiac output with manual analysis when compared with thermodilution. Given the absence of significant differences between AQ and manual analysis, this observation suggests that the bias is related to the echocardiographic determination of stroke volume, and not to errors from the automated border detection. It is concluded that AQ, besides providing information on LV volumes and ejection fraction, also can yield rapid measurements of cardiac output in most patients who are acutely ill.

Acoustics↗
PubMed1996

Orthotopic heart transplantation hemodynamics: does atrial preservation improve cardiac output after transplantation?

BACKGROUND: We have described an alternative technique for orthotopic heart transplantation (bicaval Wythenshawe technique) which maintains the right and left atrial anatomy and contractility. METHODS: Fifty patients were randomized into two groups: group A (n = 25) who had orthotopic heart transplantation using the bicaval Wythenshawe technique and group B (n = 25) who had conventional (Lower and Shumway) technique of orthotopic heart transplantation. We compared the cardiac output (measured by thermodilution technique) with atrial activation (AAI pacing) to cardiac output without atrial activity (VVI pacing) in both groups to identify any beneficial hemodynamic effects. All patients were studied the first and second weeks after transplantation. The inaccuracies of comparing cardiac output measurements caused by different loading conditions, inotropic state, and systemic vascular resistance were eliminated by using the patient as his or her own control. RESULTS: The difference between the measured cardiac output with atrial pacing and ventricular pacing was 1.42 +/- 0.44 L/min in group A in comparison with 0.32 +/- 0.4 L/min in group B (p = 0.001 Wilcoxon signed rank). The percentage of atrial contribution to the cardiac output in group A was 30% +/- 12% (standard deviation), 95% confidence interval in comparison with 7% +/- 9%, 95% confidence interval in group B. The mean stroke volume in group A was higher in sinus rhythm (65 +/- 19.2 ml) and atrial pacing (62 +/- 17.7 ml) compared with ventricular pacing (49.17 +/- 16.43 ml) p = 0.001. In group B no statistical difference was found between stroke volume measured with atrial (47.71 +/- 6.23 ml) or ventricular pacing (46.9 +/- 6.35 ml). CONCLUSIONS: We conclude that the bicaval technique of orthotopic heart transplantation preserve the atrial kick and its contribution to cardiac output early after transplantation.

Atrial Function↗
PubMed1984

Distribution of cardiac output, oxygen consumption and lactate production in canine endotoxin shock.

Endotoxin causes shock accompanied by compensatory changes such as redistribution of cardiac output and increased oxygen extraction. We studied these effects in anaesthetised dogs (etomidate: 4 mg X kg-1 X h-1, n = 14) randomly assigned to a control (n = 6) and a shock group (endotoxin 1.5 mg X kg-1; n = 8). We measured left ventricular pressure, LVEDP and LVdP/dt (Millar microtip), mean systemic, central venous and pulmonary artery pressure (Statham P23Db), cardiac output (thermodilution), organ flow (microspheres, 15 micron, 5 labels), bloodgases (PO2, PCO2), pH and lactate. All measurements were performed before and at 60, 90, 120 and 150 min after endotoxin or saline. Sixty minutes after endotoxin mean systemic pressure, LVdP/dt and cardiac output had decreased (by 60, 50 and 35%), while heart rate had increased (by 30%). Arterial PO2 was lower after endotoxin (-29%), haematocrit and mixed venous PCO2 were higher (+16 and +38%) and arterial pH had decreased from 7.34 to 7.14. After endotoxin perfusion of heart and adrenals did not change but muscle perfusion increased (by 33% at t = 90). Endotoxin caused vasoconstriction in spleen and kidneys: the percentage of cardiac output to these organs thus decreased (by 50 and 69%). Sixty minutes after endotoxin we found vasodilatation in the hepatic arterial, pancreatic, and gastrointestinal beds. Later the percentage of cardiac output to these beds decreased. Systemic arterio-venous shunting fell (from 6.5 to 0.7%). Systemic and splanchnic oxygen extraction increased (by 66 and 71% at t = 60): oxygen consumption hardly changed; 60 min after endotoxin it tended to decrease. During shock serum lactate rose (by 167% at t = 60) before oxygen consumption fell. Myocardial oxygen consumption did not alter during shock but the tension time index decreased.

Animals↗
PubMed1976

Effect of oral pretreatment with ethyl apovincaminate on the cardiac output and nutritive blood flow of various organs in rats.

Effect of ethyl apovincaminate (RGH-4405, Cavinton), administered repeatedly p.o. in doses of 0.5-1.5-4.5 mg/100 g body weight for 5 days, on cardiac output and organ fractions of cardiac output were studied in rats anaesthetized with sodium pentobarbital by Evans-blue dilution and isotope fractionation technique of Sapirstein. Cardiac output, cerebral, coronary, renal, intestinal and dermal blood flow was increased by 18-42% after 4.5 mg/100 g Cavinton, while blood pressure was unaltered. Total peripheral resistance, cerebral, coronary, dermal resistance and that of the carcass decreased significantly. Organ fractions of the cardiac output were not significantly altered after treatment.

Animals↗
PubMed1975

Determinants of cardiac output during experimental therapeutic hemodilution.

In 20 dogs, blood loss of 20 ml/kg during thoracotomy was immediately replaced with 40 ml/kg of 2.5% dextran-40 or dextran-70 in saline. An immediate rise in blood volume, associated with a decrease in hematocrit and blood viscosity, produced a marked rise in cardiac output. This effect was slightly greater with dextran-40. During the first four hours after infusion of dextran-40, both blood volume and cardiac output fell below control levels. Blood volume and cardiac output remained at or near control levels during this period in the group receiving dextran-70. In both groups, blood viscosity and hematocrit remained low throughout the study, but cardiac output increased only in response to an increase in blood volume. Twenty-four hours after infusion of either dextran-40 or dextran-70, hematocrit had decreased further, presumably due to postoperative blood loss while blood volume and cardiac output remained at or near control levels. During isovolemic hemodilution in this experimental setting, cardiac output responded primarily to changes in blood volume rather than blood viscosity. Therefore, decreased oxygen availability during hemodilution was compensated only by a rise in oxygen extraction.

Acid-Base Equilibrium↗
PubMed2005

Comparison between cardiac output values measured by thermodilution and partial carbon dioxide rebreathing in patients with acute lung injury.

CONTEXT: Thermodilution, which is considered to be a standard technique for measuring the cardiac output in critically ill patients, is not free from relevant risks. There is a need to find alternative, noninvasive, automatic, simple and accurate methods for monitoring cardiac output at the bedside. OBJECTIVE: To compare cardiac output measurements by thermodilution and partial carbon dioxide rebreathing in patients with acute lung injury at two levels of severity (lung injury score, LIS: below 2.5, group A; and above 2.5, group B). TYPE OF STUDY: Comparative, prospective and controlled study. SETTING: Intensive Care Units of two university hospitals. METHODS: Cardiac output was measured by thermodilution and partial carbon dioxide rebreathing. Twenty patients with acute lung failure (PaO2/FiO2 < 300) who were under mechanical ventilation and from whom 294 measurements were taken: 164 measurements in group A (n = 11) and 130 in group B (n = 9), ranging from 14 to 15 determinations per patient. RESULTS: There was a poor positive correlation between the methods studied for the patients from groups A (r = 0.52, p < 0.001) and B (r = 0.47, p < 0.001). The application of the Bland-Altman test made it possible to expose the lack of agreement between the methods (group A: -0.9 +/- 2.71 l/min; 95% CI = -1.14 to -0.48; and group B: -1.75 +/- 2.05 l/min; 95% CI = -2.11 to -1.4). The comparison of the results (Student t and Mann-Whitney tests) within each group and between the groups showed significant difference (p = 0.000, p < 0.05). DISCUSSION: Errors in estimating CaCO2 (arterial CO2 content) from ETCO2 (end-tidal CO2) and situations of hyperdynamic circulation associated with dead space and/or increased shunt possibly explain our results. CONCLUSION: Under the conditions of this study, the results obtained allow us to conclude that, in patients with acute lung injury, the cardiac output determined by partial rebreathing of CO2 differs from the measurements obtained by thermodilution. This difference becomes greater, the more critical the lung injury is.

Acute Disease↗
PubMed1984

Noninvasive measurement of cardiac output by continuous-wave Doppler echocardiography: initial experience and review of the literature.

Doppler echocardiographic measurement of the velocity of blood flow in the ascending aorta is a noninvasive method for determining cardiac output in the critically ill patient. Fifty-four patients in the medical intensive care unit (35 men and 19 women, age range 41 to 91 years) in whom a Swan-Ganz catheter had been inserted underwent measurement of cardiac output with use of a commercially available continuous-wave Doppler echocardiographic instrument. The aortic root diameter was measured by A-mode echocardiography. An additional 26 patients (17 men and 9 women, age range 20 to 83 years) who had undergone an open-heart surgical procedure and had hemodynamic monitoring in the postoperative period also underwent Doppler measurement of cardiac output. In these patients, the aortic root diameter was measured directly intraoperatively. Cardiac output was also determined by thermodilution in both groups. An adequate A-mode study was possible in 83% of the medical patients but only 27% of the surgical patients. Doppler signals were adequate in 84% of the medical patients and 92% of the surgical patients. The correlation between thermodilution and Doppler-derived cardiac output was good in both the medical (r = 0.94, SEE = 0.78, P less than 0.001) and the surgical (r = 0.85, SEE = 0.78, P less than 0.001) group. Doppler echocardiography is a promising noninvasive method for determining cardiac output in critically ill patients.

Adult↗
PubMed1973

Comparison of cardiac output responses to 2,4-dinitrophenol-induced hypermetabolism and muscular work.

Both electrically induced exercise and infusion of 2,4-dinitrophenol (DNP) increased oxygen consumption and tissue metabolism in chloralose-anesthetized dogs. Cardiac output increased with oxygen consumption at the same rate in both experimental conditions. The increase in cardiac output induced by exercise was, as expected, accompanied by increases in both lactate-to-pyruvate ratio and "excess lactate" in arterial blood. However, these parameters did not increase after DNP infusion until the rate of oxygen consumption had increased four- to fivefold, perhaps due to facilitation of mitochondrial electron transport by DNP. Anaerobic tissue metabolism therefore probably did not contribute significantly to increased cardiac output during the mild-to-moderate tissue hypermetabolism induced by DNP. The increased cardiac output may have been the result of metabolic changes common to both exercise and DNP infusion; muscular activity alone may not have been the primary determinant of the cardiac output response during exercise.

Anesthesia, Inhalation↗
PubMed1980

Mild hypothermia: its effect on cardiac output and regional perfusion in the neonatal piglet.

Cardiac output and regional perfusion was measured in neonatal piglets using radionuclide labeled microspheres. Measurements made at normal core body temperature (38-39.5 degrees C) were compared to those obtained after a 4-5 degrees C reduction in temperature. There is a significant reduction in cardiac output and in the myocardial, renal, pancreatic, and adrenal blood flow. The separated layers of the gastrointestinal tract wall are subject to varying decreases in blood flow. The mucosa of the distal small intestine demonstrated the most significant decreases in blood flow during mild hypothermia.

Animals↗