Search PubMed⌕ Search

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.

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

At least 1,441 records · Page 80Linked to original sources
PubMedDate not supplied

[Hemodynamic aspects of the use of hemodialysis and hemofiltration in patients with low cardiac output syndrome in the postoperative period].

Central hemodynamics and oxygen balance have been studied in 23 patients with low cardiac output syndrome during postoperative hemofiltration and acetate hemodialysis. Hemodialysis and hemofiltration caused considerable changes in circulation whose nature depended both on the initial state of central hemodynamics and oxygen balance and on detoxication technique. The data have been obtained that hemofiltration as a technique of extracorporeal detoxication was preferable in patients with postoperative low cardiac output syndrome.

Adult↗
PubMed1992

Precision of impedance cardiography measurements of cardiac output in pacemaker patients.

Objective hemodynamic assessment of pacemaker patients is necessary for gauging responses to changes in programming or other conditions that affect the circulation. Impedance cardiography permits noninvasive, repetitive determinations of cardiac output at short intervals, but data regarding variability of this method in patients with pacemakers is unavailable. Thirty-eight patients with implanted pacemakers (24 DDD, 14 VVI) and six normal subjects were studied. A computerized impedance cardiograph was used to calculate cardiac output from the product of the first derivative of the thoracic impedance signal (dZ/dt), the ventricular ejection time, and heart rate. Each patient was studied while supine after a period of at least 15 minutes of rest and repeated impedance measurements (about ten) were performed. Fourteen patients were studied in sinus rhythm, 24 were studied during DDD pacing, and 32 patients were studied during VVI pacing. Cardiac and stroke indices were calculated 706 times on the basis of 11,296 accepted beats. Variability was assessed by methods that analyzed serial measurements and variability between two consecutive and nonconsecutive measurements. The mean indices and coefficients of variation of two measurements and of serial measurements in sinus rhythm and during DDD pacing were 4%; in VVI it was 6%. The precision of impedance cardiography in all pacing modes, as demonstrated by analysis of variability, indicates that detected changes of stroke volume and cardiac output > 7% on serial (two and more) measurements, performed by the same operator and during the same session, represent true hemodynamic alterations with 95% confidence.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1984

Effect of catheter position on thermodilution cardiac output during continuous positive-pressure ventilation.

PEEP may decrease regional perfusion to nondependent lung regions, thereby creating different zones of thermal dissipation in dependent and nondependent zones of the lung. Under these conditions, the measurement of cardiac output by thermodilution may, thus, be influenced by the vertical position of the pulmonary artery catheter in the lung. We investigated this hypothesis in 7 healthy, anesthetized pigs by comparing cardiac output measurements from thermistors located in dependent and nondependent lung regions at varying levels of PEEP. Our data from thermistors in these 2 positions were similar, suggesting that the measurement of cardiac output by thermodilution is not influenced by the vertical position of the thermal sensor with respect to the left atrium.

Animals↗
PubMed1975

[Evaluation of the parietal factor interfering in the measurement of cardiac output by external detection with the aid of 99mTc labelled red cells (author's transl)].

The results of a radioisotopic exploration are not independant of the physical characteristics of the tracer used. Thus in the measurement of cardiac output index by external detection, the substitution of 131I fastened on the human serum albumine by 99mTc fastened on red cells introduces a systematic average error of +20% whose origin is double. Because of the plasma or red cell kind of the tracer, the average error done on the volume is, in 130 measurements, 26% whereas that which results from the difference of photon energy is -6%. Only this last error affects the measurement of the cardiac output and, by that time, it is demonstrated that a direct determination of the cardiac output index by STEWART-HAMILTON'S relation is impossible.

Cardiac Output↗
PubMed1994

Cardiac output and cerebral blood flow velocity in small for gestational age infants during the first 5 days after birth.

Small for gestational age (SGA) infants are at an increased risk of neurologic handicap. Cardiac output and cerebral blood flow velocity (CBFV) were measured by pulsed Doppler sonography in 15 SGA infants and in 15 appropriate for gestational age (AGA) infants on days 1 and 5 after birth. The gestational age of both groups ranged from 32 to 40 weeks and averaged 37 weeks. Cardiac output was higher in the SGA infants than in the AGA infants on day 1 (314 +/- 62 vs. 275 +/- 36 ml/min/kg; P < 0.05), but similar in the SGA and AGA infants on day 5 (319 +/- 66 vs. 318 +/- 53 ml/min/kg). On day 1, both haematocrit (0.53 +/- 0.04 vs. 0.49 +/- 0.04 l/l; P < 0.05) and systemic red blood cell transport (169 +/- 35 vs. 136 +/- 24 ml/kg/min; P < 0.01) were higher in the SGA infants than in the AGA infants. Systemic red cell flow increased in the AGA infants from day 1 to day 5 (157 +/- 27 ml/min/kg; P < 0.05), but not in the SGA infants (166 +/- 39 ml/kg/min). Mean cerebral blood flow velocity (CBFV) was higher in the AGA infants than in the SGA infants on both days (P < 0.05). However, cerebral red blood cell transport (CBFV x haematocrit) was similar in both groups. We conclude that on day 1, systemic red blood cell transport is higher in SGA infants than in AGA infants due to increased cardiac output and haematocrit.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1989

Use of conjunctival oxygen index for evaluation of cardiac output in dogs.

The relationship between the palpebral conjunctival oxygen (PcjO2) index, mixed venous oxygen tension (PvO2), and cardiac index were compared, using a canine hemorrhagic shock model. The cardiac output was reduced by reducing the blood volume in 5% increments until the initial cardiac output was reduced by one half. In each of 7 dogs, the PcjO2 index and PvO2 were found to have good correlation with cardiac index; however, the correlation coefficients were markedly reduced when the data from all of the dogs were combined. It was concluded that PcjO2 index provides an excellent means of assessing changes in cardiac index over time in the same dog; however, it cannot be used to estimate cardiac index in an individual dog with a degree of accuracy that would be clinically significant.

Animals↗
PubMed1978

Hemodynamic effects of intravenous phentolamine in low output cardiac failu;e. Dose-response relationships.

Nineteen patients with chronic low output cardiac failure were studied before, during and after infusion of phentolamine in doses of 10, 20, 30 and 40 microgram/kg/min. Significant reduction of left- and right-sided pressures and increases in cardiac index and heart rate (HR) were present within 15 minutes of starting phentolamine at the 10 microgram/kg/min dose. Minimal additional effect was observed at 30 minutes. Increased dose from 10 to 20 mu/kg/min resulted in small but significant (P less than 0.05) additional reduction in pressures and increases in HR. No additional significant changes occurred at doses of 30 or 40 microgram/kg/min. Significant hemodynamic changes persisted for at least an hour (53 +/- 3 min) after the phentolamine infusion was discontinued. Near maximal ;emodynamic effects occur within 15 minutes of starting phentolamine infusion and can be achieved at doses of 10 to 20 microgram/kg/min. Increased HR during phentolamine infusion may limit its usefulness in patients with ischemic heart disease.

Cardiac Output↗
PubMedDate not supplied

[Analysis of empyrical factors for the determination of cardiac output].

With a method by which no recirculation was possible the area of a dilution curve was obtained. On this basis it was searched what percentage represents the forward triangle of the total surface of the curve. The rôle of the V/F of the sampling system on this portion of the curve was studied, surface from which the empirical constants for the estimation of the cardiac output derivates. The data obtained suggest that the forward surface triangle was V/F dependent V/F less than 1 gave smaller forward triangles, the opposite was true with V/F greater than 1. It was also found that V/F greater than 1 subestimate the total surface of the dye curve, which means cardiac outputs higher than the real. The forward surface of the curve was reduced to a minimal percentage of the total curve when a V/F less than 1 was used. Situation that makes this area non useful to obtain from them empirical factors. If an empirical factor is use in order to measure cardiac output it had to be accepted that an important grade of error is introduced.

Animals↗
PubMed1996

End-tidal estimates of arterial PCO2 for cardiac output measurement by CO2 rebreathing: a study in patients with cystic fibrosis and healthy controls.

We set out to determine the effects of various estimates of arterial PCO2 (PaCO2) on calculation of cardiac output (Q) by the indirect Fick (CO2) method in healthy children and children with cystic fibrosis (CF), and to develop a prediction equation for children for PaCO2, based on end-tidal PCO2 (PetCO2). The study had 3 parts: 1) Twenty-three healthy children exercised lightly and moderately while arterialized capillary blood gases and PetCO2 were measured simultaneously so that a prediction equation for PaCO2 could be derived from PetCO2. Cardiac output was measured by CO2 rebreathing at each workload; different values for PaCO2 (measured in arterialized capillary blood, end-tidal, and PaCO2 derived from the Bohr equation assuming normal dead space) were used to calculate Q; 2) our equation PaCO2 = 0.647 PetCO2 + 12.4 was tested prospectively to measure Q in 9 healthy children; and 3) cardiac output based on arterialized capillary PaCO2 was compared with that based on Jones-corrected PetCO2 during light and moderate exercise in 16 CF patients whose forced expiratory volume in 1 second (FEV1), range from normal to 37% predicted. Our results have shown that in healthy children end-tidal based-estimates of PaCO2 tended to overestimate Q, whereas PaCO2 values derived by the Bohr equation and assuming normal dead space tended to underestimate Q, compared with Q calculated from directly measured PaCO2. Our prediction equation resulted in good agreement compared with directly measured PaCO2 when used to calculate Q (mean difference, +1.3%; range, +9% to -13%). CF patients with little or no airway obstruction had results similar to healthy controls, but those with severe airway obstruction had lower values for Q when PetCO2 was used instead of directly measured PaCO2. We conclude that estimates of PaCO2 from PetCO2 are not reliable in patients with moderately severe pulmonary disease due to CF. In healthy children, the prediction equation for PaCO2 from PetCO2 derived in the present study gives results superior to other bloodless methods currently in use for computation of Q by the indirect Fick (CO2) method.

Adolescent↗
PubMed1990

Improved method for cardiac output determination in man using ultrasound Doppler technique.

An existing ultrasound Doppler method for measuring cardiac output has been improved and refined, partly by locating the sampling volume higher up in the aorta while still using the aortic ring size as the effective transverse flow area. The basis for using this technique is the approximately rectangular systolic velocity profile in the aortic orifice in physiologically and anatomically normal subjects, and the fact that this profile velocity is conserved as the maximum velocity in the ascending aorta for some 3 to 4 cm above the valves. This higher location of the sampling volume improves Doppler signal quality, and does not reduce the accuracy of the method, as can be confirmed in each experimental subject. Together with automatic computer-based online signal analysis, the technique employed enables us to make continuous long-term beat-to-beat measurements of cardiac output in subjects without aortic valve disease or grossly deforming disease of the aortic root.

Aorta↗
PubMed1975

The use of radioactive microspheres to compare the effects of hydralazine, guanethidine and SK & F 24260 on the redistribution of cardiac output in anaesthetized rabbits.

1 The use of radioactive microspheres is described for the measurement of cardiac output in anaesthetized rabbits and its redistribution after the administration of drugs which lower blood pressure. 2 Hydralazine increased peripheral vascular conductance by 123%. The vascular beds in which it had most effect were those of the carcass (mainly muscle) and the kidneys. 3 SK&F 24260, (1,4 dihydro-2, 6-dimethyl-4(2-trifluoremethylpheny)-3,5,-pyridinedicarboxylic acid diethyl ester), had similar vasocilator actions. Its effect in the carcass contributed relatively more to the increase of total peripheral conductance. It also caused a remarkable degree of cerebral vasodilatation. 4 Guanethidine had a relatively small effect on total peripheral conductance and lowered blood pressure mainly by reducing stroke volume and cardiac output.

Anesthesia↗
PubMed1976

Effect of beta-adrenergic agonists aerosolized by freon propellant on tracheal mucous velocity and cardiac output.

The present study was designed to assess the effects of two beta-adrenergic agonists, isoproterenol sulfate and carbuterol hydrochloride, and aerosolized Freon propellant (a mixture of Freon II, Freon 12, and Freon 114) on tracheal mucous velocity and cardiac output in anesthetized dogs. Five groups of ten animals each received the following dosages of aerosols: Freon, 20 puffs; isoproterenol, four puffs; carbuterol, four puffs; isoproterenol, 20 puffs; and carbuterol, 20 puffs. The puff was delivered by a standard metered aerosol; each puff of isoproterenol spray contained 75 mug of isoproterenol sulfate, and each puff of carbuterol spray contained 100 mug of carbuterol hydrochloride. Tracheal mucous velocity was not changed by receiving Freon, but administration of both isoproterenol and carbuterol caused a significant increase in this measurement, with peak increases ranging from 74 to 111 percent above control values. The duration of action for four and 20 puffs of isoproterenol and for four puffs of carbuterol was two hours. Twenty puffs of carbuterol increased tracheal mucous velocity for three hours. Administration of carbuterol effected a slightly larger increase in cardiac output than isoproterenol. The duration of action for the increased cardiac output was shorter than the duration of action for the increased tracheal mucous velocity. These studies indicate that beta-adrenergic agonists may have an important role in improving mucous transport in patients with chronic obstructive pulmonary disease in whom mucociliary clearance is depressed.

Adrenergic beta-Agonists↗
PubMed1998

Use of peripheral temperature and core-peripheral temperature difference to predict cardiac output in dehydrated calves housed in a thermoneutral environment.

OBJECTIVE: To investigate the relation between cardiac output (CO) and peripheral (fetlock) temperature (PT) and core-peripheral (rectal-fetlock) temperature difference (CPTD) in dehydrated calves housed in a thermoneutral environment. ANIMALS: 28 male dairy calves 3 to 10 days old. PROCEDURE: Severe dehydration and watery diarrhea were induced by administering diuretics (furosemide, hydrohlorothiazide, spironolactone) and sucrose solution. Cardiac output was measured by means of thermodilution, core temperature was determined by placing a digital thermometer in the rectum, and PT was measured by taping a thermistor to the left hind fetlock and insulating the thermistor from ambient air. RESULTS: In thermoneutral ambient temperatures (10 to 24 C), PT and CPTD were constant and independent of CO at normal or high CO values but were linearly dependent on CO below a critical value (78% of normal CO output). Regression equations were developed that predicted CO from measured PT or CPTD. At ambient temperatures below the lower critical temperature for neonatal calves (8 to 10 C), normal values for PT and CPTD in healthy calves were significantly different from those at thermoneutral ambient temperatures. CONCLUSIONS AND CLINICAL RELEVANCE: Peripheral temperature and CPTD are practical, noninvasive, and inexpensive but only moderately useful methods for predicting CO in hemodynamically stable calves housed in a thermoneutral environment. Thus, these parameters are of some value in daily monitoring of the response to treatment and in determining need for i.v. fluid administration in dehydrated calves housed at a dry still-air temperature of 10 to 24 C but are of minimal to no value in calves housed at < 10 C.

Animals↗
PubMed2000

Cardiac output measurement with an esophageal doppler in critically ill Emergency Department patients.

Cardiac output (CO) is a principal determinant of perfusion in many critically ill patients. The objectives of this study were to determine whether physicians' estimates of CO, or cardiac index (CI), are accurate compared with CO/CI measured by esophageal doppler, and to estimate the physician time necessary for Emergency Department (ED) CO/CI measurement. We prospectively evaluated a convenience sample of critically ill, adult ED patients. Based on all available clinical information, residents and emergency medicine attendings estimated patients' CI as being high, normal, or low. A blinded investigator measured CO/CI using an esophageal doppler probe. Times to achieve optimal doppler signal were recorded. Agreement between physician CI estimates and measured CI values was assessed using the weighted kappa statistic. Thirty-three patients were evaluated. There was no agreement beyond chance between physicians' estimates of CI and measured CI. The mean time for optimal doppler signal was 5.7+/-4.3 min. Physicians' estimates of CI were inaccurate compared with measured CI. Esophageal doppler measurement of CO/CI appears to be practical from a physician time standpoint.

Adult↗
PubMed1980

Thromboresistant surface coatings for the measurement of cardiac output through continuous low flow peripheral A-V shunts.

The dilution technique for determining cardiac output using indocyanine green dye is limited in patients weighing less than 20 kg because of the obligatory volume loss. Reproducible achieved using the green dye dilution method by the establishment of a low flow peripheral arteriovenous shunt. The shunt materials were treated with thromboresistant agents--TDMAC (7%) and albumin (1 g/dl)--to facilitate the use of this technique without heparin. For A-V shunt flow rates of 8-30 cc/min reproducible values of cardiac output were obtained for up to 38 hours which were in good agreement with determinations made using the conventional technique of dye dilution.

Animals↗
PubMed1980

[The effects of changes in mean aortic pressure on the reliability of cardiac output determination from the aortic pressure curve (author's transl)].

In seven postoperative patients the effects of changes in mean aortic pressure on the reliability of cardiac output determination from the aortic pressure curve by the method of Wesseling et al. [8] were tested. Reference cardiac output (CO) was measured by thermal dilution technique. The wave impedance Zo, needed for the "contour method" of Wesseling, was derived from the initial CO-determinations. Overall correlation of both methods was good with a correlation coefficient of 4 = 0.8740. The percentage error of the contour method was -4.59 +/- 25.01%. In 4 of 7 patients there was an individual differing effect of pressure changes on the impedance Zo and by this on the error of the method. 1/Zo was clearly correlated to mean aortic pressure (r = -0.4021 to r = -0.8381). To examine the reliability of contour method also in great variations of mean aortic pressure additionally 6 aortic vessels of dogs and 1 human aortic vessel were tested in a perfusion model. In all cases increase of blood pressure was followed by a systematic failure of the contour method between +77% and +1112%. Corresponding to the mean pressure the individual failure curves were of exponential character. 1/Zo and mean aortic pressure showed high negative correlation coefficients (r = -0.9056 to r = -0.9923). The pressure dependent changes of the impedance Zo were comparable to the corresponding changes of volume elasticity coefficients. Subsequently for every vessel and patient respectively an estimation function for pressure dependent impedance Zo was calculated by use of two CO-determinations at different pressure levels. The correction of Zo by these functions resulted in a considerable reduction of the pressure dependent failure.

Adult↗
PubMed2006

Are the arms and legs in competition for cardiac output?

Oxygen transport to working skeletal muscles is challenged during whole-body exercise. In general, arm-cranking exercise elicits a maximal oxygen uptake (VO2max) corresponding to approximately 70% of the value reached during leg exercise. However, in arm-trained subjects such as rowers, cross-country skiers, and swimmers, the arm VO2max approaches or surpasses the leg value. Despite this similarity between arm and leg VO2max, when arm exercise is added to leg exercise, VO2max is not markedly elevated, which suggests a central or cardiac limitation. In fact, when intense arm exercise is added to leg exercise, leg blood flow at a given work rate is approximately 10% less than during leg exercise alone. Similarly, when intense leg exercise is added to arm exercise, arm blood flow and muscle oxygenation are reduced by approximately 10%. Such reductions in regional blood flow are mainly attributed to peripheral vasoconstriction induced by the arterial baroreflex to support the prevailing blood pressure. This putative mechanism is also demonstrated when the ability to increase cardiac output is compromised; during exercise, the prevailing blood pressure is established primarily by an increase in cardiac output, but if the contribution of the cardiac output is not sufficient to maintain the preset blood pressure, the arterial baroreflex increases peripheral resistance by augmenting sympathetic activity and restricting blood flow to working skeletal muscles.

Arm↗
PubMed1988

Transition from high cardiac output to elevated vascular resistance in hypertension.

The early phase of hypertension (borderline hypertension) is characterized by a hyperkinetic circulation caused by excessive sympathetic drive and decreased parasympathetic inhibition to the heart. In later phases the cardiac output becomes normal, but the hypertension is still neurogenic, as demonstrated by the fact that continued pharmacologic parasympathetic, beta- and alpha-adrenergic inhibition normalizes the blood pressure. In both of these phases of the process, plasma norepinephrine values are elevated. These patients also show characteristic behavioral patterns; they are outward oriented, submissive, but experience unexpressed anger and frequently harbor hostile feelings. In late phases of hypertension the cardiac output is normal and the total peripheral resistance is elevated. This hemodynamic transition can be explained by a secondary response to elevated blood pressure. The heart becomes less responsive as a result of altered receptor responsiveness and decreased cardiac compliance, whereas the responsiveness of arterioles increases because of vascular hypertrophy, which leads to changes in the wall-to-lumen ratio. However, one observation eludes explanation: the absence of plasma norepinephrine elevation in later phases of hypertension. We propose a new conceptual framework to explain the disappearance of elevated plasma norepinephrine in the course of hypertension. The concept is based on a wide range of observations with the use of various receptor-blocking agents during neurogenic pressor responses. Invariably, the blood pressure response is preserved, but the hemodynamic pattern can be altered from a high cardiac output to high total peripheral resistance or vice versa.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗