Cardiac output in twin pregnancy.
No significant difference has been found in either stroke volume or cardiac output between twin pregnancies and singleton pregnancies. Cardiac output is less in preeclamptic twin pregnancies.
Blood Pressure↗
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Cardiac output determination during intravenous cardioangiography using x-ray fluorescence analysis.
Cardiac output was determined with an indicator dilution technique during digital venous angiography of the left ventricle in 11 patients. The contrast medium injected into the right atrium was used as indicator. During and after the injection of contrast medium one blood sample per second was obtained through a catheter placed in the descending aorta. The samples were analyzed for iodine content with x-ray fluorescence analysis and cardiac output determined ad modum Stewart-Hamilton. Thermodilution was used as a reference method. The results indicate that the indicator dilution method with the use of contrast medium might be used for calibration of videodensitometric methods for blood flow measurements.
Adult↗
Comparison of methods of measuring cardiac output in newborn lambs.
To define agreement between methods, we measured cardiac output (CO) in chronically instrumented lambs by four different methods. In 23 lambs we measured CO simultaneously by the Fick and microsphere methods and with an electromagnetic flowmeter over a wide range of CO (80-454 ml/kg/min) in different experimental conditions on 97 occasions. When the electromagnetic flowmeter was corrected for coronary flow (about 8% of CO) calculated from microspheres, the mean cardiac outputs were almost identical for these three methods (237, 235, and 236 ml/kg x min, respectively). Comparisons between any two of the methods showed a correlation coefficient greater than 0.89. In four lambs, 52 measurements of CO by Fick and thermodilution had a correlation coefficient of 0.94. We conclude that any of the four methods, if appropriately applied, adequately measures CO in a variety of circumstances and may be used with confidence for physiologic or other studies.
Animals↗
Noninvasive maternal stroke volume and cardiac output determinations by pulsed Doppler echocardiography.
Sixteen obstetric patients with pulmonary artery catheters were studied by two-dimensional and pulsed Doppler echocardiography to compare prospectively pulsed Doppler-and thermodilution-derived estimations of left ventricular stroke volume and cardiac output. Systolic aortic flow velocity waveforms were obtained by pulsed Doppler ultrasound from the apical five-chamber echocardiographic window. Aortic diameters were obtained by two-dimensional echocardiography from the left parasternal long axis view. The mean (+/- SEM) aortic diameter averaged 2.1 +/- 0.1 cm, with a mean calculated aortic valve area of 3.6 +/- 0.2 cm2. The mean aortic flow velocity integral was 21.8 +/- 0.8 cm. This information was used to calculate aortic stroke volume and cardiac output. Thermodilution- and Doppler-derived estimations for maternal stroke volume (r = 0.86) and cardiac output (r = 0.94) were significantly correlated when aortic diameter measurements based on a leading vessel edge method were used. Our findings verify the accuracy of an important noninvasive technique for quantitating maternal stroke volume and cardiac output by pulsed Doppler echocardiography. This methodology should provide an alternative approach to invasive monitoring in the study of normal and abnormal maternal circulatory hemodynamics.
Aorta↗
Pneumoperitoneum in healthy humans does not affect central blood volume or cardiac output.
BACKGROUND: This study addresses the question of whether the elevation of the mean arterial pressure and central venous pressure in response to pneumoperitoneum for laparoscopic surgery is caused by increases in central blood volume and/or cardiac output. METHODS: Eleven patients in good cardiopulmonary health and scheduled for laparoscopic cholecystectomy, with a mean age of 42 years, were included. After induction of anaesthesia with fentanyl and propofol, radial arterial and central venous lines were introduced. The central blood volume and cardiac output were determined by the indicator-dilution technique, using inline densitometric measurements of indocyanine green (ICG). The measurements were made before and after the establishment of pneumoperitoneum by insufflation of carbon dioxide to an intra-abdominal pressure level of 11-13 mmHg. RESULTS: The mean arterial pressure (62+/-6 mmHg) increased after induction of pneumoperitoneum by 40+/-26% (P<0.05) and the central venous pressure increased from 6+/-4 mmHg to 8+/-6 mmHg (P<0.05). The cardiac output (4.3+/-0.9 L/min) and central blood volume (1.5+/-0.5 L) were not affected by the induction of pneumoperitoneum. CONCLUSIONS: In healthy anaesthetized subjects, the elevation of mean arterial pressure and central venous pressure in response to pneumoperitoneum was not caused by enhancement in cardiac output or central blood volume.
Adult↗
The initial distribution volume of glucose and cardiac output in the critically ill.
Blood or plasma glucose concentration can be measured accurately and rapidly. However, after a glucose challenge metabolism may modify glucose kinetics, so that glucose has not been used as an indicator for dilution volumetry. To test the hypothesis that the initial distribution volume of glucose (IDVG) reflects cardiac output rather than glucose metabolism in the critically ill, the relationship between IDVG and thermodilution cardiac output was evaluated at 27 points in 13 non-surgical, critically ill patients without congestive heart failure. The IDVG was calculated from incremental plasma glucose concentrations using a one compartment model. Correlations were obtained between the IDVG and cardiac output (r = 0.89, n = 27, P < 0.001), and between the incremental plasma glucose concentrations three minutes after the injection and the IDVG (r = 0.94, n = 27, P < 0.001). No difference was found between the IDVG with or without continuous insulin infusions. The results indicate that the IDVG reflects cardiac output rather than glucose metabolism in patients without congestive heart failure.
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Evaluation by exercise Doppler echocardiography of maintenance of cardiac output during ventricular pacing with or without chronotropic response.
To examine the effectiveness of activity-initiated rate-responsive pacing, this study assessed the increases in stroke volume and cardiac output during randomized treadmill exercise in rate-responsive and fixed-rate ventricular (VVI) pacing in 10 patients. Stroke volume index and cardiac index were determined by suprasternal Doppler measurements. Compared with the findings during VVI pacing, the rate-responsive pacing was associated with (1) prolongation of exercise duration (8.0 +/- 4.0 vs 7.3 +/- 3.6 minutes, p less than 0.05); (2) greater exercise-induced positive chronotropic response (mean maximal heart rate 127 +/- 12 vs 78 +/- 15 beats/min, p less than 0.001); (3) smaller increase in stroke volume index (38 +/- 10 vs 50 +/- 11 ml/m2, p less than 0.001), and (4) greater increase in cardiac index (4.7 +/- 1.1 vs 3.9 +/- 1.0 liters/min/m2, p less than 0.001). A significant correlation was observed between age and percent increase in stroke volume index during VVI pacing (p less than 0.05). These findings indicate that VVI pacing increased stroke volume more than did rate-responsive pacing, especially in younger patients, but the increase in cardiac output was less than that seen with rate-responsive pacing due to the absence of chronotropic response. Accordingly, an activity-sensing, rate-responsive pacemaker can effectively increase the heart rate, significantly augment cardiac output and extend the duration of exercise.
Adult↗
Cardiac output as a predictor of metabolic rate in cod gadus morhua
Adult Atlantic cod (2 kg Gadus morhua) were fitted with Doppler ultrasonic flow-probes to measure ventral aortic outflow (i.e. cardiac output). The probes remained patent for upwards of 3 months, during which time detailed relationships between cardiac output (), heart rate (fh) and rate of oxygen consumption (O2) were determined as a function of swimming speed and temperature (5 degreesC and 10 degreesC). The rate of oxygen consumption increased linearly with and exponentially with swimming speed. A very good correlation was observed between O2 and (r2=0.86) compared with the correlation between O2 and fh (r2=0.50 for all 10 degreesC data and r2=0.86 for all 5 degreesC data). However, the O2 versus fh correlation gradually improved over approximately 1 week after surgery (r2=0.86). The relationship between O2 and was independent of temperature, while the relationship between O2 and fh changed with temperature. Hence, calculating O2 from is simpler and does not require that temperature be recorded simultaneously. Variations in cardiac output were determined more by changes in stroke volume (Vs) than by fh; therefore, fh was a less reliable predictor of metabolic rate than was . Given that can be used to estimate O2 so faithfully, the advent of a cardiac output telemeter would enable robust estimates to be made of the activity metabolism of free-ranging fish in nature, thereby strengthening one of the weakest links in the bioenergetic models of fisheries biology.
Journal Article↗
Core-peripheral temperature gradient does not predict cardiac output or systemic vascular resistance in children.
We prospectively measured toe temperature, rectal temperature, systemic arterial pressure and cardiac output on two occasions one hour apart in 136 children who had had phenoxybenzamine after cardiac surgery while on cardiopulmonary bypass. Repeated measures analysis showed that there was no significant correlation between the change in temperature gradient over one hour in each patient and the change in cardiac index (r = 0.03, P greater than 0.1) or systemic vascular resistance (r = 0.007, P greater than 0.1). Although the peripheral temperature (toe temperature), and the core-peripheral temperature difference are simple, safe and inexpensive to measure in the population studied, they did not provide any guide to either cardiac output or systemic vascular resistance.
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VDD pacing at short atrioventricular intervals does not improve cardiac output in patients with dilated heart failure.
Atrial synchronous pacing with short, nonphysiological atrioventricular (AV) intervals has been reported to increase cardiac output in selected patients with severe dilated heart failure. The aim of this study was to determine the acute effect of atrial synchronous pacing with short AV intervals in a consecutive series of patients with dilated heart failure. Twelve patients with a mean ejection fraction of 21% +/- standard error 2.5% were studied. Pacing catheters were placed in the high right atrium and right ventricular apex and a balloon flotation catheter in the pulmonary artery for measurement of cardiac output. Simultaneous transthoracic echocardiography was performed for measurement of left ventricular filling time and mitral regurgitation. In a randomized crossover design, measurements were made during VDD pacing at programmed AV intervals of 100 and 60 msec and during a control period in sinus rhythm. Left ventricular filling time increased at AV intervals of 100 and 60 msec (mean difference 37 +/- 9 and 34 +/- 11 msec, respectively, both P < 0.01 compared to control). Despite increases in ventricular filling time, stroke, and cardiac index declined with short atrioventricular intervals (at an AV interval of 60 msec, stroke index fell by 2.1 +/- 0.5 mL/m2, P < 0.05 and cardiac index by 125 +/- 45 mL/m2; P = NS). Heart rate was unchanged at both AV intervals (78 +/- 4.9 at control, 78 +/- 5.2 at 100 msec and 79 +/- 4.9 beats/min at 60 msec; P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)
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Limitations of the metabolic rate meter for measuring oxygen consumption and cardiac output.
Over the past few years, a metabolic rate meter has been introduced for easy measurement of oxygen consumption. However, its accuracy is unproved. In 40 patients (26 men, 14 women, ages 34 to 73 years), cardiac output was measured simultaneously by thermodilution and the Fick method using the metabolic rate meter to quantitate oxygen consumption. In comparison with thermodilution, the results using the Fick method were low (5.26 +/- 1.18 vs 4.14 +/- 0.99 liters/min, respectively, p less than 0.01). In 18 patients cardiac output also was measured by the Fick method using a Douglas bag to quantitate oxygen consumption. In these patients, oxygen consumption measured with the metabolic rate meter was lower than that obtained using the Douglas bag (168 +/- 25 vs 216 +/- 42 ml/min, respectively, p less than 0.01). With the Douglas bag, the Fick and thermodilution cardiac output measurements were similar (4.68 +/- 1.08 vs 4.87 +/- 0.86 liters/min, respectively, difference not significant), and they differed by less than or equal to 10% in 15 patients. In contrast, with the metabolic rate meter, the results of thermodilution were higher than those with the Fick method (4.84 +/- 0.95 vs 3.60 +/- 0.71 liters/min, respectively, p less than 0.01), and differed by less than or equal to 10% in only 1 patient (p less than 0.01). Thus, the values for oxygen consumption and cardiac output obtained with the metabolic rate meter are lower than actual values. This device is less accurate than the Douglas bag.
Adult↗
Measurement of cardiac output with first-pass determination during rubidium-82 PET myocardial perfusion imaging.
In addition to providing useful clinical information, cardiac output determined during rubidium-82 positron emission tomographic (PET) myocardial perfusion studies can be used in the measurement of absolute regional myocardial blood flow using Sapirstein's method. This investigation was conducted to compare cardiac output values obtained by post-processing data acquired in a list mode PET myocardial perfusion study with those obtained using a technetium-99m-labeled red blood cell method on the same patients. Results from 14 patients showed that cardiac output can be accurately measured simultaneously in a 82Rb PET myocardial study, allowing determination of multiple perfusion and functional parameters of the heart, thus improving the cost-effectiveness of the 82Rb PET study.
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Relation of portal hemodynamics to cardiac output during mechanical ventilation with PEEP.
The relation of portal hemodynamics to cardiac output (CO) during mechanical ventilation with 15 cm H2O PEEP was studied in 12 dogs under pentobarbital anesthesia. Cardiac output was measured by thermal dilution. Portal vein flow (PF) and superior mesenteric artery flow (SMAF) were measured by electromagnetic flow probes. Intraesophageal, intraabdominal, portal vein (PVP) and intrathoracic caval (CVP) pressures, as well as the intraluminal venous pressure gradient across the liver (PVP-CVP) were measured. Intravascular volume was expanded with dextran prior to the addition of PEEP. In nine animals, dextran plus PEEP maintained CO and visceral flows within 3% of control. In three animals, CO and visceral flows fell to the same proportion. There was no increase in hepatic resistance. PF showed a linear correlation with SMAF, and SMAF had a linear correlation with CO. In these experiments, the effect of PEEP on portal hemodynamics system is primarily the consequence of reduced CO.
Animals↗
[In vitro response time of continuous cardiac output measurement in STAT mode of Vigilance after controlled flow change].
BACKGROUND: Continuous cardiac output measurement in STAT mode (STAT CCO) equipped with Vigilance displays cardiac output every 30 to 60 seconds. The aim of this study is to verify the hypothesis that each value with this system is computed only from the data collected in one update period. METHODS: The circuit was filled with normal saline and flowed by a roller pump in in vitro setting. The flow rate was set at either 2.5 l x min(-1) or 5.0 l x min(-1) and changed quickly to another state after each state had been maintained for 25 minutes. The change operation was repeated 10 times. The maximum difference was defined as the difference between the value at the start and the maximum change value. The response time was defined as the time from the start to the time to reach 80% of the maximum difference. In each operation, the response time of STAT CCO was calculated. RESULTS: The response time of STAT CCO was 9.7 +/- 1.3 min (mean +/- SD). CONCLUSIONS: The response time of STAT CCO was about 10 times longer than one update period. This result suggests that STAT CCO values are not computed only from the data collected in one update period.
Cardiac Output↗
Edwards FloTrac sensor and Vigileo monitor: easy, accurate, reliable cardiac output assessment using the arterial pulse wave.
Edwards Lifesciences has recently introduced the FloTrac sensor and Vigileo monitor system for monitoring cardiac output continuously. It does not require thermodilution or dye dilution, but rather bases its calculations on arterial waveform characteristics in conjunction with patient demographic data. It is unique among arterial waveform cardiac output systems in that it does not require calibration with another method. Studies thus far indicate that it is robust and accurate over a wide range of cardiac output and clinical conditions. It will be valuable in the care of many patients, such as those with critical illness, cardiovascular dysfunction, trauma or undergoing major surgery.
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Effects of indomethacin on cardiac output distribution in normal and asphyxiated piglets.
We determined the effect of breathing 9% CO2/10% O2/81% N2 (asphyxia) on cardiac output distribution (microspheres) in 4-5 day old unanesthetized, chronically instrumented piglets prior to and following intravenous indomethacin administration. Thirty minutes of asphyxia caused PaCO2 to increase from 35 +/- 2 mmHg to 66 +/- 2 mmHg, PaO2 to decrease from 73 +/- 4 mmHg to 41 +/- 1 mmHg, and pH to decrease from 7.52 +/- 0.05 to 7.21 +/- 0.07. Arterial pressure was increased slightly but cardiac output was not changed significantly. Asphyxia caused blood flow to the brain, diaphragm, liver, heart, and adrenal glands to increase while causing decreases in blood flow to the skin, small intestine, and colon. Blood flows to the stomach and kidneys tended to decrease, but the changes were not significant. Treatment with indomethacin during asphyxia did not alter arterial pressure or cardiac output but decreased cerebral blood flow to the preasphyxiated level and decreased adrenal blood flow about 20%. Indomethacin did not alter blood flow to any other systemic organ. At this time the piglet was allowed to breathe air for 2.5 hr undisturbed. Two and a half hours after indomethacin administration, blood flows to all organs returned to the preasphyxia control levels with the exception of cerebral blood flow which was reduced (93 +/- 13 to 65 +/- 7 ml/100 g X min). Three hours after indomethacin administration, the cerebral hyperemia caused by asphyxia was less (134 +/- 17 ml/100 g X min) than prior to indomethacin (221 +/- 15 ml/100 g X min). Indomethacin did not alter the asphyxia-induced changes to any other systemic organ.(ABSTRACT TRUNCATED AT 250 WORDS)
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Effects of a specific antidiuretic agonist on cardiac output and its distribution in intact and anephric dogs.
1. The specific antidiuretic agonist [4-valine, 8-D-arginine]vasopressin (VDAVP) was administered intravenously to seven conscious dogs at a rate of 10 ng min-1 kg-1. Cardiac output (aortic electromagnetic flowmeter), mean arterial pressure and regional blood flows (radioactive microspheres) were measured before and after 30 min of infusion. 2. Mean arterial pressure fell from 89.9 +/- 4.5 (mean +/- SEM) to 82.3 +/- 5.9 mmHg and cardiac output increased from 115.4 +/- 8.7 to 163.0 +/- 14.4 ml min-1 kg-1. Total peripheral resistance decreased from 41.6 +/- 3.7 to 27.8 +/- 3.6 units and heart rate increased from 79.2 +/- 5.9 to 123.2 +/- 5.9 beats/min. Blood flow increased significantly in the myocardium, fat and skeletal muscle vascular bed. 3. In another group of six dogs subjected to a similar protocol 24 h after bilateral nephrectomy, mean arterial pressure fell from 102.2 +/- 5.3 to 82.7 +/- 3.4 mmHg and cardiac output increased from 125.6 +/- 3.0 to 171.2 +/- 4.0 ml min-1 kg-1. Total peripheral resistance decreased from 39.3 +/- 3.4 to 23.4 +/- 1.3 units and heart rate increased from 84 +/- 4.9 to 113.3 +/- 4.3 beats/min. The increase in cardiac output and the fall in total peripheral resistance did not differ significantly between intact and anephric dogs. Regional blood flow responses differed in some respects in the two groups studied, but there was no evidence that the vasodilatory action of VDAVP depended on the presence of the kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)
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[A new approach of the hemodynamics of human essential hypertension. Study of the control of cardiac output].
The smoothing technique is used in this part II to study the cardiac output control in normotensive and hypertensive subjects. It is proved that: 1. cardiac frequency and total blood volume are both determinants of cardiac output in the normotensives; 2. in the hypertensives, blood volume is the main factor, the role of the frequency becomes negligible; 3. at high pressures, the part of the blood volume in the body-weight increases, suggesting an overhydration phenomenon in essential human hypertension.
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