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PubMed1987

Renal fraction of cardiac output cleared of radioactive indicator in 123iodine-hippuran gamma camera renography.

The renal images recorded during 1-2 min post-injection in 123I-hippuran gamma camera renography were used for determination of the total cleared renal fraction (TCRF) of cardiac output with respect to the radioactive indicator. In a study of sixty-seven normal children over two years old TCRF was 0.178 +/- 0.026 (mean +/- 1 SEE). This was in agreement with the estimation of TCRF from values of renal fraction of cardiac output and renal extraction ratio of hippuran in the literature. The left and right cleared renal fractions of cardiac output were determined directly, i.e., assessment of single kidney uptake function within a few minutes post-injection was also possible. TCRF was closely related to the glomerular filtration rate (GFR) in a group of twenty-two subjects with GFR in the interval 20-130 ml/min/1.73 m2. Intraobserver variability of TCRF was unbiased and equal to 4%. TCRF is proposed to represent an alternative to renal clearance for evaluation of renal uptake function.

Adolescent↗
PubMed1985

The effects of acute and chronic morphine on regional distribution of cardiac output in brain.

Both acute and chronic administration of morphine resulted in an increase in the percent cardiac output received by brain. However, various brain regions were affected differently by the drug treatments. The greatest increases in percent cardiac output received after chronic administration of morphine occurred in pons and cerebellum, while the greatest increases after acute administration occurred in cortex and midbrain. The changes found are in contrast with earlier studies which suggest that morphine has no effect on cerebral blood flow.

Animals↗
PubMed1995

Continuous versus bolus thermodilution cardiac output measurements--a comparative study.

OBJECTIVE: To compare the methods for continuous and bolus thermodilution cardiac output measurements. DESIGN: In vivo and in vitro experimental studies. SETTING: Surgical research division in a university hospital. SUBJECTS: Eight calves and flow bench model. INTERVENTIONS: Data were collected in vivo from eight calves instrumented with pulmonary artery catheters, which allowed both continuous and bolus thermodilution measurements. The pulmonary artery catheter was placed through the external jugular vein. All in vitro measurements were performed using a flow bench model. MEASUREMENTS AND MAIN RESULTS: A total of 232 bolus and continuous thermodilution measurements were analysed in vivo to determine the degree of agreement between the two methods. The absolute measurement bias was 0.14 L/min with 95% confidence limits ranging from -0.83 to 1.15 L/min. In vitro analysis of 576 measurements at six different temperature points (range 31 degrees to 41 degrees C), using clinically relevant flows (2 to 9 L/min), showed overestimation of flow values using continuous and bolus thermodilution methods. However, the continuous method showed better accuracy by a lower degree of overestimation. Systematic error was 9.7 +/- 8.4 (SD) % for continuous and 11.1 +/- 6.3% for the bolus method (p < .001). This effect was especially evident at lower flow rates. The influence of various temperatures on the accuracy and reproducibility of both methods of measurement was statistically significant but not clinically relevant. The infusion of lactated Ringer's lactate solution (infusion rates 100 to 1000 mL/hr) affects both methods at a low flow rate of 2 L/min, without causing a significant effect on continuous measurement at a higher flow rate (4 L/min). Shunting of 50% of circulating volume to the distal part of the thermal filament of the pulmonary catheter impaired the accuracy of continuous measurement without affecting results from bolus measurements (systematic error -26.8 +/- 8.2% for continuous and -5.2 +/- 4.1% for bolus thermodilution). CONCLUSIONS: Continuous thermodilution cardiac output measurement provided higher accuracy and greater resistance to thermal noise than standard bolus measurements. The correct placement of the catheter is essential for precise measurements.

Analysis of Variance↗
PubMed1997

The effects of changes in ventilation and cardiac output on expired nitric oxide.

The measurement of nitric oxide (NO) in expired gas is being increasingly reported in disease states such as sepsis, heart failure, and asthma. However, the effects of changes in ventilatory and cardiac parameters on expired NO are not known. Therefore, we assessed the effects of changes in minute ventilation (VE), ventilatory pattern, and cardiac output on expired gas NO levels in five anesthetized, intubated pigs. The animals were mechanically ventilated at three settings for each of respiratory rate (12 to 14, 16 to 18, and 22 to 24/min) and tidal volume (10, 15, and 20 mL/kg) applied in random sequence, yielding nine ventilatory patterns and a range of VE (3.7+/-0.1 to 13.2+/-0.8 L/min). When VE was increased, expired NO concentration declined slightly (r=-0.40, p<0.01), but the rate of excretion of NO in expired gas increased significantly (r=0.60, p<0.01). In contrast, when cardiac output was increased progressively from 3.6+/-0.1 to 4.7+/-0.3 and 5.8+/-0.4 L/min (p<0.01) by volume loading during constant eucapneic ventilation, there was no change in expired NO. Changes in VE over a physiologic range significantly affect the measurement of NO in expired gas, whereas short-term changes in cardiac output do not. To facilitate comparison between studies, we suggest that the measurement of expired NO should be reported in conjunction with data on VE.

Animals↗
PubMed2003

Impact of adaptive rate pacing controlled by a right ventricular impedance sensor on cardiac output in response to exercise.

This study examined the effects of adaptive rate pacing controlled by closed-loop right ventricular impedance sensing on exercise hemodynamics. Twelve patients in whom Biotronik INOS2+ pacemakers had been implanted 4-6 weeks earlier participated in the study. All patients completed two graded, symptom-limited exercise tests. The pacemaker was programmed to DDDR with an upper rate limit of 75-85% of the age-predicted maximum heart rate and a lower rate limit of 45-60 ppm. Heart rate was recorded continuously. An average of 5 beats during the last 10 seconds of each exercise stage was used in the analysis. Oxygen uptake (VO2) was measured using open circuit spirometry. The VO2 values from the final 15 seconds of each exercise stage were used for analysis. Stroke volume and cardiac output were measured during the last minute of each stage using impedance cardiography. The test-retest reliability of heart rate and cardiac output responses to graded exercise was assessed using repeated measures analysis of variance, for which the reliability coefficients were r = 0.993 and r = 0.954, respectively (P < 0.01). There were significant correlations (P < 0.01) between VO2 and heart rate and between VO2 and cardiac output, with correlation coefficients of r = 0.907 and r = 0.824, respectively. This method of adaptive rate pacing produced reliable, positive hemodynamic responses to graded exercise on a test-retest basis.

Aged↗
PubMed1992

Effect of nasal continuous positive airway pressure on cardiac output and oxygen delivery in patients with congestive heart failure.

We studied the acute hemodynamic effects of increasing nasal continuous positive airway pressure (CPAP) in 13 patients with acute decompensation of congestive heart failure. Heart rate, respiratory rate, pulmonary capillary wedge pressure, right atrial pressure, systemic blood pressure, and thermodilution cardiac outputs were measured at baseline, during, and after application of nasal CPAP at increasing pressures of 5, 10, and 15 cm H2O. Cardiac index, stroke volume, and oxygen delivery were calculated. Based on a significant change in cardiac output greater than or equal to 400 ml, seven patients were classified as responders, whereas six patients were considered to be nonresponders. In responders, significant increases were noted in cardiac index (2.5 +/- 0.7 to 2.9 +/- 0.9 L/min/m2), stroke volume (49 +/- 15 to 57 +/- 16 ml), and oxygen delivery (10.3 +/- 5.1 to 12.3 +/- 6.0 ml/min/kg) without a change in pulmonary capillary wedge pressure. In contrast, the nonresponders showed no significant change in any of the hemodynamic parameters. Improvement in cardiac output could not be predicted by any of the baseline hemodynamic or clinical variables, nor was it related to random variations since all variables returned to baseline after cessation of CPAP. Increase in stroke volume without a change in pulmonary capillary wedge pressure (preload) suggests either improved inotropic function of the left ventricle or reduced left ventricular afterload with CPAP. Thus, CPAP may offer a new noninvasive adjunct to improving left ventricular function and augmenting cardiac performance in a subset of patients with congestive heart failure.

Adult↗
PubMed1980

Cardiac output and regional blood flow studies in golden hamsters.

A method is described for the acute catheterization of the left ventricle of the heart and descending aorta combined with the use of the radioactive microsphere technique to study hemodynamic parameters in anaesthetized hamsters. The hemodynamic parameters studied include mean blood pressure, cardiac output, percentage distribution of cardiac output and regional blood flows in different organs.

Animals↗
PubMed1990

Continuous measurement of cardiac output with the use of stochastic system identification techniques.

The limitations of developing a technique to measure cardiac output continuously are given. Logical explanations are provided for the economic, technical, and physiologic benefits of a stochastic system identification technique for measuring cardiac output. Heat is supplied by a catheter-mounted filament driven according to a pseudorandom binary sequence. Volumetric fluid flow is derived by a cross-correlation algorithm written in the C language. In vitro validation is performed with water in a flow bench. The computed flow (y) compared with the in-line-measured flow (x) yields the linear regression y = 1.024x - 0.157 (r = 0.99). The average coefficient of variation is less than 2% over a volumetric fluid flow range of 2 to 10 L/min.

Analog-Digital Conversion↗
PubMedDate not supplied

[Estimation of cardiac output from dynamic contrast multispiral tomographic data].

OBJECTIVE: To describe and apply a method for programmatically calculating central hemodynamic parameters from the data of dynamic contrast X-ray computed tomography (CT). MATERIAL AND METHODS: A procedure is proposed to calculate cardiac output (CO) on the basis of the tracer dilution method as a ratio of the injected dose of a contrast agent (Urografin, Shering AG, Austria) to the area under the concentration-time curve derived for one of the cardiac chambers: [see text]. The blood concentration of the agent was estimated from the blood iodine (I) concentration-X-ray density (XD) regression dependence: [XD] = 0.49+22.07 x [I]. Thirty-three patients were studied on a multispiral X-ray Somatom Sensation 4 computed tomograph (Siemens), by injecting 15-20 ml of Urografin. The calculating method was realized as a software package for processing dynamic contrast CT data. RESULTS: The proposed method could exactly determine the values of cardiac output: the correlation with the results of the reference technique (Doppler echo measurement) was highly significant (r = 0.95; p < 0.001) in the whole range of values. Moreover, the data on XD could accurately determine the blood concentration of both iodine (I): [XD] = 0.49+22.07 x [I] and gadolinium as a component of the contrast paramagnetic Gd-DTPA for which the solution concentration-XR dependence was as follows: XD 1.2+33.6 x [Gd]. CONCLUSIONS: Thus, dynamic spiral CT may be also used for the estimation of cardiac output by the tracer dilution method.

Adolescent↗
PubMed2003

Exercise blood pressure response, cardiac output and 24-hour ambulatory blood pressure monitoring in children after aortic coarctation repair.

BACKGROUND: The aim of this study was to assess blood pressure at rest, the response to exercise and the 24-hour ambulatory blood pressure monitoring (ABPM) profile in children operated for aortic coarctation. METHODS: Twenty children were operated upon for aortic coarctation. The patients' data were compared with those obtained from 19 healthy controls of the same age. Treadmill exercise testing was performed and cardiac output was determined using the acetylene-rebreathing method and indexed for the body surface area; ABPM was performed only in the patients group. The main outcome measures were the time of exercise, systolic (SBP) and diastolic (DBP) blood pressure both at rest and at peak exercise, maximal heart rate, total peripheral vascular resistance at rest and at peak exercise, and the pulse pressure (PP = SBP-DBP) at rest, at peak exercise and at ABPM. The Mann-Whitney test (non-parametric) and linear regression analysis were used when appropriate. RESULTS: Patients compared with healthy controls showed significant differences in SBP and PP at rest, and in DBP, cardiac index, total peripheral vascular resistance and PP at peak exercise. In the patients group only, linear regression analysis showed a significant correlation between PP and cardiac output, both at rest and at peak exercise, and between the arm-leg gradient at rest and PP at ABPM. CONCLUSIONS: These findings suggest that blood pressure abnormalities could be due both to the altered baroceptor reflex control mechanism, resulting in cardiac output and total peripheral vascular resistance abnormalities, and to the progressive increase in resistance during exercise at the site of the repair, resulting in the higher PP, that may be related to a local loss of the natural aortic elasticity.

Adolescent↗
PubMed2002

Predictive performance of a physiological model for enflurane closed-circuit anaesthesia: effects of continuous cardiac output measurements and age-related solubility data.

BACKGROUND: The disposition of inhalation anaesthetics is governed by the factors described in the Fick principle. METHODS: We have recalibrated a previously validated physiological model for enflurane closed-circuit inhalation anaesthesia, using individual continuous cardiac output measurements as well as age-related enflurane solubility coefficients as inputs to the model. Two model versions using 'calculated' (Brody's formula) or 'measured' (thoracic electrical bioimpedance) cardiac output values, and two versions with 'standard' (fixed) or 'age-related' solubility coefficients were formulated. RESULTS: Data from 62 ophthalmic surgical patients were used to validate the predictive performance of the four model versions. The root mean squared errors (total error) and scatters (error variation) were similar with the extended model versions, but the group biases (systematic error component) were significantly less with the model versions that included age-related solubility compared with the versions using standard solubility coefficients (bias -0.76/-0.78% vs -3.44/-3.60%). CONCLUSION: The inclusion of age-related solubility coefficients but not of continuous cardiac output measurements improves the predictive performance of the physiological model for closed-circuit inhalation anaesthetic conditions in routine clinical practice.

Adolescent↗
PubMed1998

Test-retest reproducibility of maximum cardiac output by Doppler echocardiography.

Test-retest reproducibility of stroke volume and cardiac output using Doppler echocardiography was examined during maximum cycle exercise in 13 young men. A coefficient of variation of 8.5% and 8.1% and intraclass correlation coefficient of 0.90 and 0.91 for maximum stroke volume and cardiac output, respectively, indicate a high degree of reproducibility using this technique.

Adult↗
PubMed2000

Cardiac output measurements during cross-clamping of the descending thoracic aorta in pigs. A comparison between transit-time ultrasound, thermodilution and pulsed Doppler ultrasound.

BACKGROUND: Cross-clamping of the descending thoracic aorta (XC) induces an increase in cardiac output (CO). The intention of this study was to evaluate the high CO during XC by the use of clinically available methods (thermodilution and pulsed Doppler ultrasound) compared to transit-time ultrasound flowmetry of the ascending aorta as the gold standard. METHOD: Ten pigs were anaesthetised with ketamine and fentanyl. The descending thoracic aorta was cross-clamped for 30 min, and cardiac output was measured with pulmonary artery thermodilution technique, pulsed Doppler ultrasound on the aortic annulus and transit-time ultrasound flowmetry of the ascending aorta. RESULTS: At 15 min following XC, CO increased from 1.7 l/min to 4.6 l/min measured with transit-time ultrasound (P<0.05). With thermodilution technique, CO increased from 2.6ll/min to 5.7 l/min (P<0.05), and from 2.4 l/min to 6.0 l/min measured with Doppler ultrasound (P<0.05). There was an increase in mean arterial pressure of 81% and heart rate increased 76% (P<0.05). CONCLUSION: XC of the descending thoracic aorta induces an increase in CO of 171%. Thermodilution and pulsed Doppler ultrasound are reliable methods for detecting high cardiac output during thoracic aortic surgery.

Animals↗
PubMed1993

Assessing and treating decreased cardiac output.

The compensatory pathophysiological mechanisms for a decreased cardiac output are explored via three case studies. The assessments and nursing interventions appropriate to these patients are included in separate tables. Evaluation and decision making about the patient's clinical status and responses are major nursing responsibilities that require astute assessment and skilled intervention to lead to optimal patient outcomes.

Aged↗
PubMed1979

Evaluation of the microsphere method for determination of cardiac output and flow distribution in the rat.

The radioactive microsphere technique was applied to determine simultaneous cardiac output and flow distribution in the rat. Left ventricular injections of large numbers of microspheres were given, without significant adverse effects, allowing determination of flow to organs and tissues with low perfusion rates. In order to determine coronary blood flow it was necessary to excise the inner lining of the left ventricle, thus eliminating activity from deposits of microspheres. Cardiac output determination showed less variation with the sampling catheter in the abdominal aorta than in the femoral artery. It is concluded that the microsphere method can be conveniently used for hemodynamic studies in the rat, and that the abdominal aorta is the preferred site for the placement of the reference catheter in the rat.

Animals↗
PubMed1992

Estimation of the following cardiac output using sympathetic tone and hemodynamics for the control of a total artificial heart.

A sympathetic neurogram is potentially useful for the development of a real time total artificial heart (TAH) control system. We used sympathetic tone and hemodynamic derivatives to estimate the following cardiac output in acute animal experiments using adult mongrel dogs. Moving averages of the mean left atrial pressure and mean aortic pressure were used as parameters of the preload and afterload, respectively. Renal sympathetic nerve activity (RSNA) was employed as a parameter of sympathetic tone. Equations for the following cardiac output were calculated using multiple linear regression analysis of the time series data. A significant correlation was observed between the estimated and following measured cardiac output. These results suggest the potential usefulness of the sympathetic neurogram for the real time TAH automatic control system.

Animals↗
PubMed1998

[Evaluation of continuous measurement of cardiac output with thermodilution in critical patients].

BACKGROUND: A new pulmonary artery catheter and monitor for continuous cardiac output measurement (CCO), based on thermodilution principle, has been recently developed. Aim of our study was to evaluate the new system by comparing data obtained with the CCO with the standard bolus thermodilution method (TD). METHODS: Nineteen patients admitted in a medical intensive care unit were studied. In each patient 6 daily measurements of cardiac output (CO) were recorded using both the CCO and the TD. The parallel monitoring was continued for 48 h; 12 pair determinations were obtained in each patient with a total of 228. RESULTS: Total CO ranged from 2.6 L/min to 10.6 L/min. The regression coefficient was 0.94. The bias of all measurements was 0.03 (SD: +1.22-1.16). The mean relative error was 1.52% +/- 29.9. Modifications in temperature or variations in heart rate did not change the agreement between the two techniques. CONCLUSIONS: Our results confirm that CCO, although does not have all the characteristics of an ideal monitoring system, can be considered extremely useful and safe.

Adult↗
PubMedDate not supplied

A comparison of the effects of salbutamol, etilefrine and dextran during hypotension and low cardiac output states in rabbit.

The effects of salbutamol (25 and 50 micrograms/kg), etilefrine (50 and 200 micrograms/kg) and dextran (8 ml/kg) on cardiovascular function have been studied in the rabbit. The three drugs raised the resting cardiac output (with salbutamol producing delta max 52%, P less than 0.001, n = 5) and right heart filling pressure (RHFP, delta max from dextran 3.5 cmH2O; P less than 0.001, n = 6) and lowered total peripheral resistance (TPR, delta max from salbutamol 46%, P less than 0.001, n = 5). However, TPR rose with the 200 micrograms/kg etilefrine (P less than 0.05, n = 5). Pulse pressure rose with salbutamol (P less than 0.001, n = 6) and etilefrine (P less than 0.05, n = 6). Etilefrine raised resting BP (delta max, P less than 0.001, n = 6); salbutamol lowered resting BP (delta max, P less than 0.001, n = 6) while dextran (n = 6) had little effect on resting BP. The actions of salbutamol are mediated mainly through beta 2-adrenoceptors although the drug also has some minor beta 1-adrenoceptor action. With etilefrine, the increase in cardiac output and the reduction in TPR are mediated through beta-adrenoceptors while the increases in RHFP, blood pressure and TPR are a direct action on the alpha-adrenoceptors. However, during haemorrhage the fall in diastolic pressure produced by salbutamol was considerably reduced while the reduction in mean BP and systolic pressure (which sometimes rose) was abolished. Dextran raised BP during hypotension produced by either sympathectomy or haemorrhage but not during normotension. The reflex recovery in RHFP and the reflex tachycardia were slightly attenuated during lower body negative pressure (LBNP) after salbutamol or dextran. The reflex recovery in blood pressure was complete and the pressure sometimes exceeded the resting level by up to 10 mmHg during LBNP after salbutamol, etilefrine (50 micrograms/kg only) and dextran. The reduced TPR (presumably due to vasodilation) and the increases in cardiac output and RHFP at an adequately maintained blood pressure produced by suitable doses of the three drugs may be useful in the management of circulatory shock and related states.

Albuterol↗