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PubMed1987

Pulsed Doppler ultrasound compared with thermodilution for monitoring cardiac output responses to changing left ventricular function.

To determine the responsiveness of the pulsed Doppler technique to pacing and drug induced changes in left ventricular function 125 simultaneous cardiac output measurements by pulsed Doppler ultrasound and thermodilution were compared in 12 patients. The Doppler velocity frequencies were analysed using a signal averaging process and the validity of this method first tested in vitro. This showed almost perfect linearity of pulsed Doppler and electromagnetic flow determinations in a test rig. Although data points showed greater scatter in the clinical study, a highly significant linear relation between cardiac output measurements by pulsed Doppler and thermodilution was confirmed by regression analysis (r = 0.88, p less than 0.001). Certain mean values for cardiac output by the two techniques differed, however, by up to 0.9 litre.min-1. Despite this, changes in cardiac output in response to pacing, inotropic stimulation with dobutamine, and vasodilatation with nitrates were directionally similar, indicating a useful role for the pulsed Doppler technique in monitoring responses to treatment in the intensive care unit. Pulsed Doppler also provided a simple measure of left ventricular contractile function. Thus the inotropic response to dobutamine produced a significant rise in peak aortic flow velocity, and this variable was unaffected by either pacing or nitrate induced vasodilatation.

Cardiac Output↗
PubMed1977

The effects of four months' treatment with spironolactone on systemic blood pressure, cardiac output and plasma renin activity in hypertensive patients.

The effect of spironolactone on BP, cardiac output, plasma renin activity and urinary excretion of electrolytes has been studied in 12 hypertensive patients. After 1 month of spironolactone therapy there was a significant decrease in arterial BP. Urinary sodium excretion was significantly decreased and plasma renin activity increased. After four months of spironolactone therapy there was no further decrease in arterial BP. Cardiac output, heart rate and stroke volume were unchanged in the supine position, but the calculated total peripheral vascular resistance (TPVR) was reduced, indicating that the lower BP was mainly a result of dilatation of the resistance vessels. During exercise there was still a significant decrease in arterial BP but this was related to a decrease in both cardiac output and TPVR.

Adult↗
PubMed1984

Cardiac output of dogs exercising in the heat.

We measured cardiac output and central blood temperature in five large dogs (27 kg mean body wt) running at 7.5 km/h for 30 min at two work loads and at low and high ambient temperature (Ta). Each animal ran on a level treadmill (O2 cost about 4 times that of resting) at 25 and 35 degrees C Ta and at a 20% slope (O2 cost about 10 times that of resting) at 25 and 35 degrees C Ta. Cardiac output (CO) was the same at 15 and 30 min of exercise at both work loads and both TaS. CO was higher at 35 degrees C Ta at both work loads. Blood temperature rose 0.6 degrees C during exercise on the level treadmill at 25 degrees C and stabilized after the 15th min of exercise. On the level treadmill at 35 degrees C, blood temperature increased by 1.9 degrees C after 30 min. During 30 min of running at 20% slope, blood temperature increased by 3.2 degrees C at 25 degrees C and by 4.6 degrees C at 35 degrees C. At these work loads the dog is able to increase CO during exercise in the heat. This response is similar to that of humans doing moderate exercise in the heat but is in contrast to that of humans doing heavy exercise in the heat, in whom CO shows a drop or no change compared with cool conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

The relationship between cardiac output measured by the thermodilution method and that measured by the carbon dioxide rebreathing technique during laparoscopic surgery.

Carbon dioxide insufflation during laparoscopic surgery may interfere with the accuracy of the cardiac output value measured by the NICO2 system. The authors simultaneously measured cardiac output by the thermodilution method and by the carbon dioxide rebreathing technique during laparoscopic adrenalectomy in a patient with a nonfunctional adrenal tumor. There was a strong correlation between the cardiac output values measured by the two methods. This case report suggests that the carbon dioxide rebreathing technique can be used to monitor cardiac output during laparoscopic surgery.

Aged↗
PubMed2001

Does the optimization of cardiac output by fluid loading increase splanchnic blood flow?

We studied the effects of increasing cardiac output by fluid loading on splanchnic blood flow in patients with haemodynamically stabilized septic shock. Eight patients (five female, 39-86 yr) were assessed using a transpulmonary thermo-dye-dilution technique for the measurement of cardiac index (CI) intrathoracic blood volume (ITBV) as a marker of cardiac preload and total blood volume (TBV). Splanchnic blood flow was measured by the steady state indocyanine-green technique using a hepatic venous catheter. Gastric mucosal blood flow was estimated by regional carbon dioxide tension (PRCO2). Hydroxyethyl starch was infused to increase cardiac output while mean arterial pressure was kept constant. In parallel, mean norepinephrine dosage could be reduced from 0.59 to 0.33 microg kg(-1) min(-1). Mean (SD) TBV index increased from 2549 (365) to 3125 (447) ml m(-2), as did ITBV index from 888 (167) to 1075 (266) ml m(-2) and CI from 3.6 (1.0) to 4.6 (1.0) litre min(-1) m(-2). Despite marked individual differences, splanchnic blood flow did not change significantly neither absolutely (from 1.09 (0.96) to 1.19 (0.91) litre min(-1) m(-2)) nor fractionally as part of CI (from 28.4 (19.5) to 24.9 (16.3)%). Gastric mucosal PRCO2 increased from 7.7 (2.6) to 8.3 (3.1) kPa. The PCO2-gap, the difference between regional and end-tidal PCO2, increased slightly from 3.2 (2.7) to 3.4 (3.1) kPa. Thus, an increase in cardiac output as a result of fluid loading is not necessarily associated with an increase in splanchnic blood flow in patients with stabilized septic shock.

Adult↗
PubMed1979

Cardiac output and blood pressure at rest and during exercise in boys with bronchial asthma.

Cardiac output, using dye-dilution technique, and intra-arterial blood pressure at rest and during exercise on a bicycle ergometer were determined in six boys with bronchial asthma, mean age 11.9 years. Intra-arterial blood pressure was also measured in another group of eight boys with bronchial asthma. Cardiac output, stroke volume, arteriovenous oxygen difference, blood pressure and total peripheral vascular resistance at rest and during exercise up to maximal level were within the normal limits of healthy boys of the same age. At maximal exercise, cardiac output averaged 12.4 l/min, stroke volume 66 ml, systolic, diastolic and mean blood pressures 128, 81 and 107 mmHg, respectively, and total peripheral vascular resistance 10.9 mmHg/l/min. The maximal arteriovenous oxygen difference amounted to 14.1 ml/100 ml blood which is similar to that in healthy adults.

Adolescent↗
PubMed1985

[Mechanisms of changes in cardiac output during stimulation of afferent fibers of a somatic nerve].

In anesthetized cats, the technique of electromagnetic expenditure-metry aided to study changes of the cardiac output and venous inflow in pressor responses to stimulation of the tibial nerve's afferent fibers. The cardiac output was found to increase in 47% of observations which was accompanied by increased venous inflow in half of the cases and by decreased one in 1/3 of observations. Vagotomy as well as suppression of the efferent link of cardiac responses with atropin and obsidan induced shifts of the cardiac output in the somatic nerve stimulation. The optimum level of arterial pressure responses was revealed peculiar by positive shifts of the cardiac output in pressor responses to the above action.

Animals↗
PubMed1976

Comparison of methods to calculate cardiac output using the CO2 rebreathing method.

A comparison was made of methods used to calculate cardiac output by the indirect (CO2) Fick procedure (equilibrium method). Alternative methods for calculation of arterial PCO2, mixed venous PCO2, and conversion of gas tension to content were tested. Cardiac output values determined with a "corrected" equilibrium PCO2, to approximate mixed venous PCO2, were observed to be closest to cardiac output values determined on similar populations by the dye dilution method. Arterial PCO2 was best estimated from the Bohr equation using a dead space in exercise from prediction equations in the literature applicable to the populations under study. CO2 dissociation curves used to derive the veno-arterial CO2 content difference, were shown to differ considerably. For the present, the curve by McHardy [25], as modified by Jones (personal communication), and similar to the standard Comroe curve [5], was chosen.

Adolescent↗
PubMed1986

Relationship between frequency of ventilation, airways and pulmonary artery pressures, cardiac output and tracheal tube deadspace.

Intravascular and airway pressures, cardiac output (CO) and blood gas tensions were measured in five adult patients after hepatobiliary surgery. They were ventilated at frequencies of 15, 100 and 200 breaths min-1 (bpm) with the respiratory fresh gas (RFG) supplied at the proximal and distal end of a Mallinckrodt Hi-Lo tracheal tube. The peak airway pressure (P AW) fell from 1.20 kPa at 15 bpm to 0.6 kPa at 100 bpm, rising again to 1.9 kPa at 200 bpm, and both changes were significant (P less than 0.05). The mean pulmonary artery pressure (PAMP) remained in the range 1.87-2.00 kPa (14-15 mmHg) at 15 and 100 bpm but rose to over 2.67 kPa (20 mmHg) at 200 bpm (P less than 0.05). Cardiac output, heart rate and systemic arterial pressure remained unchanged. A small but significant (P less than 0.05) reduction in PaCO2 occurred when the RFG was moved to the distal end of the tracheal tube. A theoretical analysis predicts that the minimal P AW to maintain CO2 hemostasis will occur between 30 to 100 bpm, which is reflected in the results of the present study.

Adult↗
PubMed1992

Influence of cardiac output on the correlation between mixed venous and central venous oxygen saturation.

The influence of cardiac output on the correlation between central venous oxygen saturation and mixed venous oxygen saturation was assessed in 51 patients who had both a pulmonary artery catheter and separate central venous catheter in situ. Seventy-six paired samples were taken from the catheters and oxygen saturation measured immediately in a Ciba Corning 2500 Co-oximeter. Cardiac output was measured using a standard thermodilution technique. The data were separated into groups with low cardiac index (< 2.5 litre min-1 m-2; n = 20), medium cardiac index (2.5-4.0 litre min-1 m-2; n = 36) and high cardiac index (> 4.0 litre min-1 m-2; n = 20). The correlation coefficients of the three groups were: low cardiac index 0.95, medium cardiac index 0.88 and high cardiac index 0.95 (P < .001 for all three groups). All measurements were made before any x-ray and necessary repositioning of the central venous catheter. These results suggest that central venous oxygen saturation is a useful estimate of mixed venous oxygen saturation and that the influence of cardiac output on that estimate is minimal.

Aged↗
PubMed1998

[Effects of cardiac output on blood and tissue pH during general anesthesia with constant ventilation].

We investigated the effects of cardiac output on blood and tissue pH in 106 adult patients undergoing cardiac or non-cardiac surgery under general anesthesia. After anesthetic induction, the minute ventilation volume was kept constant at 10 ml.kg-1 x 10 cycles.min-1. A pulmonary artery catheter and a nasogastric tube incorporating a tonometer were inserted. During surgery, cardiac index (CI), pH, Pco2, BE, So2 and Hb of arterial and mixed venous blood as well as gastric intramucosal pH (pHi) were measured simultaneously. Oxygen uptake index (Vo2I) and blood CO2 contents were calculated. The measurements were repeated every 10 to 20 minutes during surgery or during the prebypass period. Two patients with preoperative cardiogenic shock were excluded from data analysis because of development of severe acidosis and 624 sets of data from 104 patients were analyzed. Arterial and mixed venous pH correlated negatively with CI. Blood Pco2 and base excess (BE) correlated positively and negatively, respectively, with CI. Blood lactate concentration measured 142 times in the last 30 patients correlated positively with CI. Vo2I correlated positively with CI and Paco2 correlated positively with Vo2I. Veno-arterial differences in Pco2 and Cco2 correlated negatively with CI. Due to the difference, Caco2 correlated positively with CI, while Cvco2 did not correlate with CI. pHi correlated negatively with CI but only marginally. By multiple regression analysis, pHi was not affected significantly by CI, while it showed positive correlation with pHa, Hb, Sao2 and negative correlation with blood temperature. When cardiac output increased, blood pH decreased due to increased Pco2 and decreased BE. An increase in Paco2 might result from both an increase in Vo2 or Vco2 and decreased ventilation-to-perfusion ratio. A decrease in BE might result from increased washout of acids (e.g. lactate) from the tissue to the central circulation. In contrast to blood pH, pHi or tissue pH was not affected significantly by cardiac output unless patients were in cardiogenic shock.

Adult↗
PubMed1998

Evaluation of a new semi-continuous cardiac output system in the intensive care unit.

PURPOSE: A new semi-continuous thermodilution cardiac output (CCO) system has been developed recently (Opti-Q and Q-vue Abbott critical care system). The aim of this study was to compare the accuracy and reproducibility of this new device with conventional ice-bolus thermodilution cardiac output (BCO). METHODS: Fifteen critically ill patients who needed pulmonary artery catheterization were prospectively investigated. Eighty seven paired data using BCO and CCO methods were compared. Reproducibility was assessed from 90 BCO and 87 CCO determinations by calculation of the mean standard error (SEM) and according to Bland and Altman methodology. RESULTS: The BCO and CCO ranged from 2.46 to 11.20 L.min-1 and from 1.75 to 10.05 L.min-1 respectively. Bias (mean difference between BCO and CCO) was null (0.002 L.min-1, P = 0.98), precision (SD of the bias) was 0.74 L.min-1 and the limits of agreement (mean difference +/- 1.96 SD) ranged from -1.45 to 1.45 L.min-1. The threshold to consider two cardiac outputs as different (3 x SEM) was equivalent for BCO and CCO (0.54 and 0.465 L.min-1 respectively). According to the Bland and Altman method, reproducibility of CCO was greater than that of BCO; bias of repeated measurements of BCO and CCO were 0.15 L.min-1 (P < 0.05) and 0.047 L.min-1 (NS), respectively. CONCLUSION: Compared with BCO, this new device was accurate but cannot be considered as interchangeable regarding the limits of agreement. Reproducibility of CCO was superior to BCO.

APACHE↗
PubMedDate not supplied

Comparison of impedance cardiography to direct Fick and thermodilution cardiac output determination in pulmonary arterial hypertension.

Cardiac output (CO) is an important diagnostic and prognostic tool for patients with ventricular dysfunction. Pulmonary hypertension patients undergo invasive right heart catheterization to determine pulmonary vascular and cardiac hemodynamics. Thermodilution (TD) and direct Fick method are the most common methods of CO determination but are costly and may be associated with complications. The latest generation of impedance cardiography (ICG) provides noninvasive estimation of CO and is now validated. The purpose of this study was to compare ICG measurement of CO to TD and direct Fick in pulmonary hypertension patients. Thirty-nine enrolled patients were analyzed: 44% were male and average age was 50.8+/-17.4 years. Results for bias and precision of cardiac index were as follows: ICG vs. Fick (-0.13 L/min/m2 and 0.46 L/min/m2), TD vs. Fick (0.10 L/min/m2 and 0.41 L/min/m2), ICG vs. TD (respectively, with a 95% level of agreement between -0.72 and 0.92 L/min/m2; CO correlation of ICG vs. Fick, TD vs. Fick, and ICG vs. TD was 0.84, 0.89, and 0.80, respectively). ICG provides an accurate, useful, and cost-effective method for determining CO in pulmonary hypertension patients, and is a potential tool for following responses to therapeutic interventions.

Adolescent↗
PubMed1983

Cardiac output and gas exchange during heavy exercise with a positive pressure respiratory protective apparatus.

Cardiac output and gas exchange during heavy exercise with a positive pressure respiratory protective apparatus. Scand j work environ health 9 (1983) 471-477. Continuous positive pressure breathing effectively prevents inward leakage of noxious agents into a breathing apparatus but may interfere with venous return and cardiorespiratory performance during heavy work. Cardiac output was therefore recorded with a dye dilution method, and ventilatory variables were measured from expired air, for seven well-trained firemen at a work load of 150 W. All the variables except the invasive ones were also measured during the maximal work load that each subject could sustain for 10 min. At random the subjects worked with a mouthpiece and a face mask with and without a positive pressure of 0.4 kPa. No variable deteriorated during positive pressure breathing, although the central venous oxygen pressure increased, an occurrence indicating higher cardiac output in relation to oxygen demand. Dead space ventilation decreased, an indication of increased ventilatory efficiency. Positive pressure breathing (0.4 kPa) thus does not deteriorate cardiopulmonary function during intermediate or maximal work loads.

Adult↗
PubMed1988

[Measurement of cardiac output by thoracic electrical bioimpedance or thermodilution].

The present study was designed to assess a new non invasive method for measuring cardiac output. The thoracic electrical bioimpedance method was compared with the reference one, thermodilution. The measurements were made simultaneously with NCCOM3 (bioimpedance) using the freeze data mode, and with a Swan-Ganz catheter and a haemodynamic computer (thermodilution). The study involved 11 spontaneously breathing patients in a steady haemodynamic state. Ten measurements were carried out with both methods for each patient. Statistical analysis of the 110 paired values was carried out by computer. The various statistical tests applied confirmed that there was a highly significant correlation between values for cardiac output obtained by each of these two methods (r = 0.818; p less than 0.005); they also showed a significantly more important dispersion of the measures for each patient with thermodilution. The mean value of the thermodilution "standard deviation" (0.64 l.min-1) was significantly more important (p less than 0.005) than the one with NCCOM3 (0.24 l.min-1). Thoracic electrical bioimpedance appeared a safe method for measuring cardiac output, providing the limits of the method are kept. The objective is not to replace the Swan-Ganz catheter, but to propose an alternative method for measuring cardiac output. This method is very interesting in many circumstances, particularly for intensive care patients: it is a non invasive technique, continual measurement is not time-limited, and its use is very easy.

Adult↗
PubMed1996

Pressure support ventilation increases cardiac output in neonates and infants.

Fifteen neonates and infants were investigated during pressure controlled ventilation (PCV) and pressure support ventilation (PSV) on a Servo 300 ventilator. Changes in cardiac output (aortic mean blood flow velocity) were assessed with the Doppler technique. During PSV cardiac output increased by 16% (P < 0.01) compared with PCV with equal ventilation. Mean airway pressure decreased significantly during PSV compared with PCV, which may explain the increased cardiac output. During PSV, when inspiratory/expiratory (I:E) relations are dependent on the patient, we found a lower I:E ratio compared with PCV. It can be assumed that at least part of the decreased mean airway pressure is caused by the lower I:E ratio. As the heart rate was unchanged, the variations in cardiac output were caused by alterations in stroke volume. It is concluded that a patient triggered mode should be preferred providing that the neonate/infant has the ability to elicit the ventilator's triggering system.

Airway Resistance↗
PubMed1986

Continuous noninvasive real-time monitoring of stroke volume and cardiac output by thoracic electrical bioimpedance.

Thoracic electrical bioimpedance (TEB) is a noninvasive method for the estimation of left ventricular stroke volume (SV). Objections to TEB in the past have included systematic overestimation of SV and cardiac output in normals, poor correlation in absolute terms with standard cardiac output reference techniques, motion and ventilation artifacts which distorted recorded waveforms except when patients remained in apnea during measurements, and lack of a computer to yield rapid heat-to-beat quantitation of SV and cardiac output. The present study entails real-time, beat-to-beat cardiac output determinations using TEB and assessing its agreement via a digital computer against a reference standard, thermodilution. A correlation coefficient of 0.88 is reported with 85% of data points falling within 20% confidence limits on either side of the line of identity.

Adult↗
PubMed1986

Effect of ritodrine on uteroplacental blood flow and cardiac output distribution in unanesthetized pregnant guinea pigs.

The effects of ritodrine, 15 micrograms X min-1 X kg-1 infused intravenously for 2 hours, on cardiac output distribution and uteroplacental blood flow were investigated in 10 chronically catheterized guinea pigs between 57 and 63 days of pregnancy. Ritodrine produced an average 29% increase in cardiac output, three quarters of which was distributed to the carcass and myocardium. Absolute placental blood flow decreased by 10%, and the placental fraction of cardiac output decreased by one third. Uteroplacental vascular resistance increased by 41% during ritodrine infusion. The proportional changes in placental blood flow were positively correlated and those in placental vascular resistance negatively correlated with the change in cardiac output.

Animals↗