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At least 1,081 records · Page 60Linked to original sources
PubMed2002

[Partial CO(2) rebreathing technique versus thermodilution: measurement of cardiac output before and after operations with extracorporeal circulation].

BACKGROUND: The NICO(2) monitor determines "pulmonary capillary blood flow" (Qpc) and cardiac output (Qt) using the "partial CO(2) rebreathing technique". The agreement between NICO(2) and thermodilution (TD) cardiac output was compared before and after cardiac surgery with cardiopulmonary bypass (CBP). In addition, the possibility of calculating the intrapulmonary shunt fraction (Qs/Qt) by combining data from the NICO(2) monitor and the TD was investigated. METHODS: In 32 patients measurements were made following induction of anesthesia ("pre-CBP"), 30 min after weaning from CBP ("post-CBP"), and 6-8 h after surgery ("post-OP"). Qt was determined by the NICO(2) monitor and TD, Qpc by the NICO(2) monitor, and Qs/Qt(O(2)) from the standard formula. An intrapulmonary shunt was calculated using Qpc(NICO(2)) and Qt(TD) according to the equation Qs/Qt=1-Qpc/Qt. Bland-Altman and regression analysis techniques were used for statistical evaluation. RESULTS: "Pre-CBP" there was a good agreement between Qt(NICO(2)) and Qt(TD) with both a bias and precision of -0.13+/-0.46 l/min and a correlation of r=0.88+/-0.47 ( p<0.001). In contrast, "post-CBP" and "post-OP" there was a lack of agreement for Qt (bias and precision: 0.97+/-1.05 l/min and -0.33+/-0.8 l/min, respectively). Regarding the shunt calculations no significant correlations between methods could be found. CONCLUSION: Cardiac output measurement by the NICO(2) monitor agree well with TD under steady-state conditions but after CBP the agreement was too small. Combining Qpc(NICO(2)) and Qt(TD) does not offer a reliable possibility for calculating intrapulmonary shunt.

Algorithms↗
PubMed2002

Antenatal diagnosis and treatment of a case of fetal goitrous hypothyroidism associated with high-output cardiac failure.

A case of fetal goitrous hypothyroidism associated with high-output cardiac failure is presented. At 32 weeks of gestation, the antenatal diagnosis of goiter was made based on ultrasound examination, and the fetal thyroid function was examined by amniocentesis and cordocentesis. Color and pulsed Doppler examinations demonstrated a high vascular flow pattern in the goiter and marked elevation of the maximum velocity in the common carotid artery at the level of the neck. It was suspected that arteriovenous shunting through the large goiter resulted in high-output cardiac failure with cardiomegaly and pleural effusion. The fetus was treated by injection of levothyroxine sodium into the amniotic fluid at 33 weeks of gestation and the goiter thereafter decreased in size, with subsequent improvement of the high-output cardiac failure. The maximum velocity in the common carotid artery fell rapidly before the shrinkage of the fetal goiter and in parallel with the fetal level of thyroid stimulating hormone.

Adult↗
PubMed2001

Reproducibility of cardiac output measurements by Doppler echocardiography in prepubertal children and adults.

The aim of this study was to examine reproducibility of stroke volume and cardiac output measurements by Doppler echocardiography during submaximal and maximal exercise in adults and children. Fourteen healthy children (8 girls and 6 boys aged 10.9 +/- 0.9yr) and eleven healthy young adults (1 female and 10 males aged 22.3 +/- 3.8 yr) underwent a progressive maximal upright cycle test until exhaustion with estimation of stroke volume and cardiac output by Doppler echocardiography on two separate occasions (one week apart). Maximal oxygen uptake and maximal heart rate were not significantly different between both tests in the children and adults indicating that similar exhaustive efforts were achieved at each test. No significant differences for mean values of stroke volume and cardiac output were observed at rest in the children and whatever the exercise intensity in the children and adults. No significant differences were observed between values of root mean square (precision and precision of error) in both groups. Thus we demonstrated that stroke volume and cardiac output values obtained by Doppler echocardiography at rest and during submaximal and maximal exercise were reproducible on test-retest measurements in children and adults.

Adolescent↗
PubMed1994

Validation of cardiac output measurements with noninvasive Doppler echocardiography by thermodilution and Fick methods in newborn piglets.

Since cardiac output measured by the noninvasive pulsed Doppler technique has not been well correlated to results from the invasive thermodilution or Fick methods in neonates, the three methods were evaluated in 6 sedated newborn piglets (age < or = 7 days, weight 1.5 +/- 0.7 kg) in room air and after 10 min of hypoxia. Doppler velocities were measured in the ascending aorta, and the aortic root diameter was measured in early diastole. A Swan-Ganz catheter in the left pulmonary artery sampled mixed venous blood for central venous O2 content and measured cardiac output by thermodilution. Oxygen consumption was measured by the open-circuit technique and used to determine cardiac output by the Fick method. In room air, values obtained by pulsed Doppler, thermodilution and Fick methods (0.270 +/- 0.05, 0.246 +/- 0.05 and 0.241 +/- 0.05 liters/kg/min, respectively) were similar, with a correlation coefficient (r) between Doppler and thermodilution values of 0.89, Doppler and Fick values of 0.82 and thermodilution and Fick values of 0.88. Although hypoxia sometimes produced larger differences between paired values, correlation coefficients remained high (Doppler echocardiography vs. thermodilution, r = 0.96; Doppler vs. Fick methods, r = 0.92; thermodilution vs. Fick method, r = 0.95). The mean +/- SD of the percent difference between values obtained by Doppler echocardiography and thermodilution was 4.2 +/- 14.4% in room air and 12.8 +/- 14.4% in hypoxia, whereas differences in values obtained by Doppler and Fick methods was 6 +/- 14.9% in room air and 14.7 +/- 8.5% with hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Multiple determination of cardiac output using a two-bottle technique.

A technique is described to perform multiple determinations of cardiac output; two 150 ml bottles of 5% dextrose in water, stored in identical conditions, are immersed in an ice slush, contained in a styrofoam cooler. Comparison of cardiac output determinations obtained with this technique and with multiple syringes indicates very close duplication of results. The technique is very inexpensive and allows one to follow patients for up to four hours with as many as 30 consecutive determinations of cardiac output.

Cardiac Output↗
PubMed1993

Solubility characteristics of the ideal agent for measurement of cardiac output by soluble gas uptake methods.

Measurements of the rate of uptake of soluble gases such as nitrous oxide or acetylene has been used as the basis of a method of cardiac output estimation since 1912. Using theoretical models of single, multiple and rebreathing techniques of cardiac output measurement, we determined the effect of solubility in blood and lung tissue on the changes in the final expired concentration of the gas. Decreasing lung tissue solubility increased the sensitivity of all three models to cardiac output changes. When the lung tissue/blood partition coefficient was 1, the optimum blood/gas partition coefficients were 2.6 for the single-breath model, 4.1 for the three breath-model and 3.5 for the rebreathing model. A selection of gases, including volatile anaesthetic agents was studied using the same models. Under most conditions, enflurane approximated most closely to the requirements for an ideal agent for use in this technique of cardiac output measurement.

Anesthetics↗
PubMedDate not supplied

Cardiovascular changes during laparoscopy. Studies of stroke volume and cardiac output using impedance cardiography.

The stroke volume and cardiac output changes in twenty-four patients undergoing laparoscopy were measured using the non-invasive technique of impedance cardiography. There was a moderate fall of stroke volume and cardiac output during intraperitoneal insufflation of carbon dioxide which was directly related to the volume of gas used. The need for caution during laparoscopy particularly in ill patients is emphasised.

Adult↗
PubMed1995

Changes in end-tidal carbon dioxide tension following sodium bicarbonate administration: correlation with cardiac output and haemoglobin concentration.

An intravenous administration of sodium bicarbonate (NaHCO3) forms excess CO2, resulting in an immediate increase in end-tidal carbon dioxide tension (PETCO2). We hypothesized that the time until PETCO2 reached a maximum, and the magnitude of the increase in PETCO2 are influenced by cardiac output and haemoglobin concentration, respectively. To test this hypothesis, we examined changes in PETCO2 following an intravenous administration of NaHCO3 at different levels of cardiac output and haemoglobin concentration. We administered 0.2 mmol.kg-1 of 8.4% NaHCO3 into the vena cava in 15 anesthetized dogs under mechanical ventilation of 20 breaths per min. Cardiac output was increased by dopamine infusion, and decreased by blood withdrawal under halothane anaesthesia. Haemoglobin concentrations were changed by haemodilution with hydroxyethyl starch. When control measurements were taken, time-max (the time until the increase in PETCO2 reached a maximum) was 4 +/- 0.2 breaths-time, and delta CO2-max (the magnitude of the increase in PETCO2) was 0.90 +/- 0.04 kPa (6.6 +/- 0.3 mmHg). Cardiac output was inversely correlated with time-max (r = 0.94, P < 0.0001), while it revealed a poor correlation with delta CO2-max. Haemoglobin concentration showed a significant correlation with delta CO2-max (r = 0.736, P < 0.005), but not with time-max. We concluded that the time course and the magnitude of changes in PETCO2 following intravenous administration of NaHCO3 reflect changes in cardiac output and haemoglobin concentration, respectively.

Anesthesia, Inhalation↗
PubMedDate not supplied

Cardiac output effects of O3 and NO2 exposure in healthy older adults.

Eight healthy adults (56-85 yrs) were exposed in an environmental chamber to filtered air (FA), 0.60 ppm NO2, 0.45 ppm O3, and 0.60 ppm NO2 + 0.45 ppm O3 to investigate the effects of NO2 and O3 exposure on cardiac output. The subjects were exposed to each condition for two hours, while they exercised and rested in alternating 20-min periods. Minute ventilation averaged 26-29 l/min among the four exposures. Cardiac output was measured by the noninvasive impedance cardiography method, and was recorded prior to each exposure with the subject at rest, and during the last five minutes of each exercise period. There were no differences in cardiac output at preexposure among the four exposures. The exercise-induced increase in cardiac output with NO2/O3 exposure was significantly smaller (P < 0.05) than with the FA or O3 alone exposures. Reaction products of inhaled NO2 are known to cross the lung membranes, probably as a nitrate or nitrite. NO2 and O3 are also known to react together to form nitrate and nitrite. We hypothesize that a nitrate or nitrite reaction product of inhaled O3 and NO2 crosses the lung membrane into the general circulation, where it functions as a vasodilator, thereby reducing cardiac output.

Aged↗
PubMed1980

Electromagnetic flow-probe implantation for cardiac output measurements in rabbits.

A technique suitable for continuous measurement of beat-to-beat cardiac output in conscious rabbits for relatively longer periods is described. The method consists, essentially, of implanting a specially constructed electromagnetic flow probe around either the pulmonary artery or the aorta during left thoracotomy (second intercostal space) in animals anesthetized with hypnorm. With care, the procedure is successful in a large proportion of the animals. Little postoperative care is required and the flow probe remains functional for several weeks up until the animals were killed to recover the probe for reimplantation. The cardiac output values (ml/min/kg) in conscious rabbits were: normal 183 +/- 9; unilateral renal hypertensive animals, 108 +/- 10 and bilateral renal hypertensive animals, 153 +/- 15. Isoprenaline increased, and propranolol decreased, the cardiac output in conscious normotensive rabbits.

Animals↗
PubMed2003

Cardiac output, oxygen consumption and muscle oxygen delivery in submaximal exercise. Normal and low O2 states.

Cardiac output (Q) changes linearly with oxygen consumption (VO2) in normal subjects undertaking submaximal exercise (Q = A + B x VO2 where A is the y intercept and B the slope). If (hypothesis 1) the increase in cardiac output above the resting state represents the blood flow to exercising muscle (qm) and the increase in VO2 represents the oxygen consumption of exercising muscle (VO2m) then, where CaO2 is the arterial oxygen content, oxygen extraction, Em = 1/(B x CaO2). Secondly, exercising muscle venous oxygen content, CvO2m = CaO2 - 1/B. Limiting the hypothesis just to the calculation of VO2m (hypothesis 2) allows calculation of qm if CaO2 and CvO2m are available. From Koskolov et al. (Am. J. Physiol.: Heart and Circ. Physiol. 273, H1787-H1793, 1997), exercising muscle blood flow (qm) is equal to the increment in cardiac output when CaO2 is normal but exceeds it when CaO2 is low. Muscle Oxygen extraction (Em) is found to be 68% in submaximal exercise. Hence, muscle oxygen delivery (DaO2m) for a given metabolic rate is sustained in low O2 states (at 1.48 ml DaO2m per ml VO2m), confirmed by analysis of Roach et al. (Am. J. Physiol.: Heart and Circ. Physiol. 276, H438-H445, 1999).

Anemia↗
PubMed1989

[The interrelations of arterial pressure, cardiac output and coronary blood flow during orthostatic reactions].

The influence of hypotension induced with orthostasis, upon cardiac output and coronary flow was studied in anesthetized cats. The body tilt to 15-60 degrees lowered the mean arterial pressure parallel with reduction of cardiac output. Under the tilt up to 30 degrees and 60 degrees, a significant difference was found in decrease of systolic but not diastolic pressures. The degree of cardiac output reduction was two-fold greater than the degree of diastolic pressure reduction. The findings suggest a participation of vascular constrictor responses in the forming of orthostatic reactions. The coronary flow decrease only began with the tilt up to 30 degrees. Its extent did not depend on the intensity of hypotension being, probably, the result of the reduction of the heart work.

Animals↗
PubMed1992

The validity of cardiac output measurement by thoracic impedance: a meta-analysis.

A structured review of existing literature was undertaken to provide an objective evaluation of the validity of cardiac output measurement by thoracic impedance. Relevant studies were obtained from journals, advertising literature, and N.A.S.A. contract publications, using MEDLINE retrieval and references from other studies. Studies describing concurrent measurement of impedance cardiac output with other techniques were selected if they met certain technical and methodological criteria known to improve the validity of impedance cardiac output measurement. All studies provided Pearson's correlation coefficient as a measure of association. A weighted mean coefficient was calculated for selected studies using Fisher's Z transformation of the data. Correlation of impedance with thermodilution gave r = 0.82; with dye dilution, r = 0.83; with Fick technique, r = 0.80; and with radionuclear angiography, r = 0.65. Studies done on ICU patients showed a lower correlation than studies done on non-ICU patients (p = 0.003). A moderately good correlation exists between impedance cardiac output measurement and other techniques, although correlation is not so good when ICU patients are studied. Better techniques and methodology may improve this correlation.

Adult↗
PubMed2000

Influence of cardiac output on dexmedetomidine pharmacokinetics.

Dexmedetomidine, a highly selective alpha(2)-adrenoceptor agonist, reduces the requirements for anesthetic, analgesic, sedative, and hypnotic drugs. Dexmedetomidine pharmacokinetics were characterized in healthy subjects after intravenous administration by means of a computer-controlled infusion pump. A series of seven stepwise increasing pseudo-steady-state plasma concentrations were targeted. The influence of cardiac output on the pharmacokinetics was investigated by use of a compartmental modeling approach in which the elimination clearance was characterized as being either cardiac output independent or dependent. At dexmedetomidine concentrations of 0, 0.6, and 1.2 ng/mL, mean (SD) estimated cardiac outputs were 5. 6 (0.85), 5.1 (0.67), and 4.5 (0.83) L/min, and mean (SD) clearances were 40 (10), 38 (9.0), and 35 (8.5) L/h, respectively. Dexmedetomidine V(SS) and elimination half-life were 72 (19) L and 1. 9 (0.62) h, respectively. The approximately 3 to 19% decrease in cardiac output observed within the anticipated therapeutic range of 0.3 to 1.2 ng/mL was similar to that observed for clonidine. The decrease in cardiac output with increasing plasma concentrations of dexmedetomidine resulted in a corresponding decrease in drug elimination clearance of < or =12% within the therapeutic range; however, this decrease in dexmedetomidine clearance is likely not clinically relevant.

Adolescent↗
PubMedDate not supplied

Noninvasive cardiac output monitoring during exercise before and after coronary artery bypass surgery.

A computerized continuous wave Doppler instrument was used to monitor changes in cardiac output and stroke volume during supine symptom limited graded bicycle exercise in 30 subjects. Eight patients were studied before and after coronary artery bypass graft (CABG) and were found to have patent grafts (group 1). Six patients were symptomatic after CABG and had at least one graft occluded (group 2). Sixteen age matched asymptomatic subjects served as controls (group 3). In group 1 patients before CABG, the duration of exercise was 5 +/- 2 mins (mean +/- standard deviation), the double product was 162 +/- 25, the percentage change in cardiac output with exercise was 33 +/- 7 and the percentage change in stroke volume was 1 +/- 5. Following CABG in group 1 patients, the duration of exercise increased to 9 +/- 2 mins, the double product to 186 +/- 16, the percentage change in cardiac output to 74 +/- 14 and the stroke volume to 13 +/- 12% (P less than 0.05). These results were not significantly different from those obtained in the group 3 patients (controls) in whom the duration of exercise was 10 +/- 3 mins, double product 211 +/- 24, percentage change in cardiac output 95 +/- 30 and the percentage change in stroke volume was 13 +/- 5.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Output↗
PubMedDate not supplied

In vitro comparison of six commercially available thermodilution cardiac output systems.

Six commercially available thermodilution cardiac output catheter-and-computer systems were evaluated over a variety of simulated clinical conditions using a fixed-output pulsatile-flow pumping unit. Simultaneous testing was performed at pumping rates of 60, 80, and 120 beats per minute and over an output range of 1.57 liters/min to 14.11 liters/min under normothermic, hyperthermic, and hypothermic conditions. Precision within each thermodilution system, as measured by the standard deviation (S.D.) of serial determinations, was acceptable with an overall S.D. range between 0.015 and 0.588 liters/min. When averaged over all experimental situations, the mean percent deviation of five or ten serial measurements was within 10 percent of the known pump output for all systems and maintained a fairly constant relationship above or below the pump output. In this in vitro test, iced injectate did not consistently improve precision or accuracy above that obtained with room-temperature injectate. Features other than performance should also be considered when selecting a particular unit to fulfill a clinical or research need.

Cardiac Output↗