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PubMed1992

Determination of cardiac output by an angle and diameter independent dual beam Doppler technique in critically ill infants.

OBJECTIVE: To compare cardiac output measurements in critically ill infants by the dual beam Doppler and thermodilution techniques. DESIGN: Prospective direct comparison of the two techniques. For statistical evaluation one randomly assigned paired measurement of every patient was used. SETTING: Paediatric intensive care unit in a university hospital. PATIENTS: 18 infants after open heart surgery aged 4-25 months (weight 4-10 kg). INTERVENTIONS: Cardiac output measurements by dual beam Doppler and thermodilution techniques were performed within 10 minutes of each other and without knowledge of the results of the other methods. Multiple measurements were performed on some patients with a pharmacological or electrophysiological intervention or with a minimum of six hours between each pair of measurements. MEASUREMENTS AND MAIN RESULTS: Three patients were excluded because of an inadequate Doppler signal or a significant residual shunt. Cardiac output measurements ranged from 0.4 to 2.2 l/min for the thermodilution technique and from 0.5 to 2.1 l/min for the dual beam Doppler technique. Agreement between both methods was acceptable. The mean difference between the two methods was 0.026 l/min with two standard deviations ranging from -0.20 to 0.26 l/min. CONCLUSION: The dual beam Doppler technique was shown to have promise for the non-invasive determination of cardiac output in critically ill infants.

Cardiac Output↗
PubMed1986

Cardiac output is an apparent determinant of nitroglycerin pharmacokinetics in rats.

The steady-state pharmacokinetics of nitroglycerin (NTG) were investigated in 11 rats after sequential infusions of either NTG alone (10 micrograms/kg/min) or NTG plus vasopressin (the latter at 5.5 mU/kg/min). Arterial and venous plasma concentrations of NTG in the femoral bed were obtained at 41 and 45 min during each infusion phase. Cardiac output was estimated twice in each animal using 85Sr and 141Ce microspheres. NTG systemic clearance in arterial plasma was found to be strongly correlated with cardiac output (r = 0.784, n = 22, P less than .001). Because NTG distribution between red blood cells and plasma was independent of concentration (up to 150 ng/ml in plasma) and hematocrit (25-48%), the systemic clearance of NTG in arterial blood could be estimated as about 3/4 of cardiac output. Vasopressin co-infusion decreased both the cardiac output and the arterial NTG plasma clearance, but it also increased the arteriovenous extraction of NTG. Thus, vasopressin had not net effect on the venous plasma clearance, of NTG. In animals with NTG infusions alone, cardiac output also significantly correlated with NTG venous plasma clearance (P less than .01) and arteriovenous extraction (P less than .05). These data indicate that, in the absence of vasopressin, NTG pharmacokinetics are dependent on the cardiac output, thus providing an example wherein the systemic clearance of a drug was shown to be related to systemic blood flow. These results support the concept that the vasculature acts as a clearing organ for organic nitrates, and they also provide a hemodynamic explanation for the high variability in NTG plasma concentrations observed under presumed steady-state conditions.

Animals↗
PubMed1998

Effects of CGS 21680, a selective A2A adenosine receptor agonist, on cardiac output and vascular resistance in acute heart failure in the anaesthetized rat.

1. The effects of CGS 21680, a selective A2A adenosine receptor agonist, on cardiac output, blood pressure, mean circulatory filling pressure (Pmcf), arterial and venous resistances, heart rate and left ventricular end-diastolic pressure were assessed in rats with acute heart failure by means of coronary artery occlusion. 2. Animals (n=6 in each group) were divided into five groups: group I, sham-operated vehicle-treated (0.9% saline; 0.018 mL min(-1)); groups II-V, subject to coronary artery occlusion and treated with vehicle (0.9% saline; 0.018 ml min(-1)) and CGS 21680 (0.1, 0.3 and 1.0 microg kg(-1) min(-1)), respectively. Haemodynamic measurements were taken one hour after completion of surgery, ninety minutes after coronary artery occlusion (except in group I), and fifteen minutes after infusion of saline or CGS 21680. 3. Baseline haemodynamic measurements before occlusion were found not to differ significantly between the different groups of animals. However, after occlusion, cardiac output, rate of rise in left ventricular pressure (+ dP/dt) and blood pressure were significantly reduced when compared to corresponding values in sham-operated animals. In addition, occlusion of the coronary artery resulted in a significant elevation in venous resistance, Pmcf and left ventricular end-diastolic pressure as compared to corresponding values in sham-operated animals. 4. Infusion with CGS 21680 at the highest dose significantly reduced blood pressure, arterial resistance and left ventricular end-diastolic pressure when compared to occluded vehicle-treated animals (group II). Administration of CGS 21680 at the highest dose also significantly increased cardiac output (28%) and heart rate (10%) in comparison to occluded vehicle-treated animals. In addition, the highest dose of CGS 21680 significantly reduced Pmcf (9%) and venous resistance (62%) in comparison to occluded vehicle-treated animals. Administration of CGS 21680 did not significantly affect +dP/dt when compared to occluded vehicle-treated animals. 5. The results from the present investigation indicate that occlusion of the coronary artery in rats results in a state of heart failure characterized by reduced arterial pressure and cardiac output, and increased venous resistance, Pmcf and left ventricular end-diastolic pressure. Administration of CGS 21680 to animals with acute heart failure resulted in increased cardiac output which was due to reduced venous resistance, as well as increased heart rate.

Acute Disease↗
PubMed1986

Beneficial effects of atrioventricular sequential pacing on cardiac output and left ventricular filling assessed with pulsed Doppler echocardiography.

There has been increased interest in the beneficial effects of atrio-ventricular (AV) pacing over ventricular (V) pacing. This study attempted to evaluate the changes in cardiac output and left ventricular filling dynamics when the pacing mode was switched from V pacing to AV pacing. Study population consisted of 26 patients with multiprogrammable AV pacemakers. Cardiac output was determined as a product of echocardiographically determined cross sectional area of the aortic annulus and Doppler-determined velocity integral of left ventricular outflow over systole. Left ventricular peak rapid filling rate (PFR) and peak atrial filling velocity to peak rapid filling velocity ratio (A/R) were determined from measurements at the mitral annulus. Cardiac output showed a significant improvement when the pacing mode was switched from V to AV pacing, and the percent change ranged from 3 to 73% (average 26%). The improvement in cardiac output brought about by AV synchrony was greater in patients with smaller PFR (r = -0.71, p less than 0.01) and larger A/R ratio (r = 0.77, p less than 0.01). On the other hand, PFR was greater with V pacing than with AV pacing. Greater increment of the PFR was produced by the loss of atrial contraction in patients with smaller PFR (r = -0.82, p less than 0.01) and larger A/R ratio (r = 0.76, p less than 0.01). Thus, AV pacing provides a great improvement in left ventricular filling, i.e., cardiac output, which cannot be obtained with V pacing even with the compensatory enhancement of left ventricular rapid filling. These beneficial effects of AV pacing seemed to be greater in patients with impaired left ventricular rapid filling.

Adolescent↗
PubMed1999

Lithium dilution cardiac output measurements using a peripheral injection site comparison with central injection technique and thermodilution.

OBJECTIVE: The lithium dilution technique for the measurement of cardiac output by the central injection of lithium chloride was introduced by Linton et al. in 1993. In the present report, we compare lithium dilution cardiac output measurement (LD) by the peripheral injection of lithium chloride (pLD) and by central venous injection (cLD), cardiac output determined by electromagnetic flowmetry (EM), and conventional thermodilution cardiac output measurement (TD) on ten swine. METHODS: The animals were monitored with a pulmonary artery catheter, a femoral artery catheter, and an electromagnetic flowmeter placed around the ascending aorta. cLD, pLD, TD, and EM were determined at the baseline, then in a hyperdynamic state produced by dobutamine administration, at a second baseline, and finally in a hypodynamic state induced by propranolol during deep anesthesia. Data were analyzed by linear regression analysis and the comparison method described by Bland and Altman; bias and precision were calculated using the method of Sheiner and Beal. RESULTS: The correlation coefficient between pLD and EM (0.86) was significantly less than that between cLD and EM (0.96), however it was not significantly different from that between TD and EM (0.85). The precision value of pLD (0.14) was the same as that of TD (0.14). CONCLUSION: The results of the present study indicate that pLD is a reliable technique.

Anesthesia, General↗
PubMed1984

Accuracy of thermodilution measurement of cardiac output in low flows applicable to feline and small canine patients.

A model system of feline or small canine cardiac output was used to produce known liquid flow rates in the range of 100 to 750 mL/min for comparison against a thermodilution technique of flow measurement. Thermal indicator size was decided by the thermal time concentration curve detected by the Edwards 9520A cardiac output computer. Ten consecutive readings for each flow were made. Regression analysis and Student's t-test were used to evaluate the results. The computer was found to give good correlation with the accurate flow measured by a graduated cylinder over a period of time (r = 0.99). An error of less than 7% overestimation of flow by thermodilution was found with flows greater than 200 mL/min (p less than 0.05). A significant error of more than 20% overestimation of the actual flow occurred with flows less than 200 mL/min (p less than 0.05). The Edwards 9520A computer was compared to the older Edwards 9510A model by averaged triplicate measurements at six different cardiac outputs in an anesthetized cat. The measurements were not significantly different (p less than 0.01). Thermodilution using an Edwards computer proves to be a promising tool in the measurement of low flows applicable to feline and small canine cardiac outputs.

Animals↗
PubMed1985

Effect of steroids on the cardiac output and renal changes of bacteremia.

The effects of methyl prednisolone pretreatment in dogs prior to a bacterial infusion were measured in relation to cardiac output, blood pressure, intrarenal blood flow, and glomerular filtration rate. In dogs not pretreated with steroid, cardiac output fell 61.1 per cent 30 min postbacterial infusion and remained depressed for the balance of the experiment. Pretreated animals showed a similar 61 per cent depression in cardiac output immediately following bacterial infusion, but then experienced recovery of cardiac output and blood pressure to levels not significantly different from controls at the conclusion of the experiment. Changes in outer cortical bloodflow and glomerular filtration rate were not affected by steroid pretreatment. Based on the above data, the author concludes that the salutary effect of steroid pretreatment on cardiovascular dynamics occurs independently of changes in renal function.

Animals↗
PubMed2005

Reliability of peak VO(2) and maximal cardiac output assessed using thoracic bioimpedance in children.

The purpose of this study was to evaluate the reliability of a thoracic electrical bioimpedance based device (PhysioFlow) for the determination of cardiac output and stroke volume during exercise at peak oxygen uptake (peak VO(2) in children. The reliability of peak VO(2) is also reported. Eleven boys and nine girls aged 10-11 years completed a cycle ergometer test to voluntary exhaustion on three occasions each 1 week apart. Peak VO(2) was determined and cardiac output and stroke volume at peak VO(2) were measured using a thoracic bioelectrical impedance device (PhysioFlow). The reliability of peak VO(2) cardiac output and stroke volume were determined initially from pairwise comparisons and subsequently across all three trials analysed together through calculation of typical error and intraclass correlation. The pairwise comparisons revealed no consistent bias across tests for all three measures and there was no evidence of non-uniform errors (heteroscedasticity). When three trials were analysed together typical error expressed as a coefficient of variation was 4.1% for peak VO(2) 9.3% for cardiac output and 9.3% for stroke volume. Results analysed by sex revealed no consistent differences. The PhysioFlow method allows non-invasive, beat-to-beat determination of cardiac output and stroke volume which is feasible for measurements during maximal exercise in children. The reliability of the PhysioFlow falls between that demonstrated for Doppler echocardiography (5%) and CO(2) rebreathing (12%) at maximal exercise but combines the significant advantages of portability, lower expense and requires less technical expertise to obtain reliable results.

Cardiac Output↗
PubMed1998

Chronic resuscitation after trauma-hemorrhage and acute fluid replacement improves hepatocellular function and cardiac output.

OBJECTIVE: To determine whether prolonged (chronic) resuscitation has any beneficial effects on cardiac output and hepatocellular function after trauma-hemorrhage and acute fluid replacement. BACKGROUND DATA: Acute fluid resuscitation after trauma-hemorrhage restores but does not maintain the depressed hepatocellular function and cardiac output. METHODS: Male Sprague-Dawley rats underwent a 5-cm laparotomy (i.e., trauma was induced) and were bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of maximal bleed-out volume was returned in the form of Ringer's lactate (RL). The animals were acutely resuscitated with RL using 4 times the volume of maximum bleed-out over 60 minutes, followed by chronic resuscitation of 0, 5, or 10 mL/kg/hr RL for 20 hours. Hepatocellular function was determined by an in vivo indocyanine green clearance technique. Hepatic microvascular blood flow was assessed by laser Doppler flowmetry. Plasma levels of interleukin-6 (IL-6) were determined by bioassay. RESULTS: Chronic resuscitation with 5 mL/kg/hr RL, but not with 0 or 10 mL/kg/hr RL, restored cardiac output, hepatocellular function, and hepatic microvascular blood flow at 20 hours after hemorrhage. The regimen above also reduced plasma IL-6 levels. CONCLUSION: Because chronic resuscitation with 5 mL/kg/hr RL after trauma-hemorrhage and acute fluid replacement restored hepatocellular function and hepatic microvascular blood flow and decreased plasma levels of IL-6, we propose that chronic fluid resuscitation in addition to acute fluid replacement should be routinely used in experimental studies of trauma-hemorrhage.

Animals↗
PubMed1991

Hepatic extraction of indocyanine green is depressed early in sepsis despite increased hepatic blood flow and cardiac output.

Although active hepatocellular function is depressed during sepsis, it is not known whether this occurs in the very early stages of sepsis and whether it is due to depressed cardiac output or hepatic blood flow. To study this, rats were subjected to sepsis by cecal ligation and puncture and hepatocellular function was determined at various intervals thereafter by assessing the ability of the liver to clear different doses of indocyanine green. The indocyanine green concentration was continuously measured in vivo with a fiberoptic catheter and an in vivo hemoreflectometer. Maximal velocity and kinetic constant of the clearance of indocyanine green, hepatic blood flow, and cardiac output were determined in experimental and sham-operated rats. The results demonstrate that hepatic blood flow and cardiac output increased 2 to 10 hours after cecal ligation and puncture, while hepatocellular function (maximum velocity and kinetic constant) was decreased even 2 hours following cecal ligation and puncture. No linear correlation between hepatocellular function and hepatic blood flow or cardiac output was found under such conditions. The extremely early depression in active hepatocellular function, despite the increased hepatic blood flow and cardiac output, may form the basis for cellular dysfunctions leading to multiple organ failure during sepsis.

Animals↗
PubMed1990

Noninvasive assessment of cardiac output in children using impedance cardiography.

This study evaluated the effect of intracardiac shunting on the accuracy of thoracic bioimpedance-derived cardiac output determinations. Twenty-six patients, ranging in age from 3 months to 17 years, underwent cardiac catheterization during which simultaneous Fick and impedance measurements of cardiac output were obtained. The subjects were divided into three groups: 10 children with no intracardiac shunts, nine children with predominant left-to-right intracardiac shunts, and seven children with predominant right-to-left intracardiac shunts. Positive correlations between impedance and Fick-derived cardiac output determinations were obtained in the non-shunt group (r = 0.84), with lower correlations in the left-to-right shunt group (r = 0.70). In the right-to-left shunt group, the impedance derived cardiac output correlated with Fick pulmonary flow (r = 0.82), but the variability was unacceptably large. Although further study is needed, impedance cardiography appears to have validity as a methodology in pediatric critical care and cardiovascular health research.

Adolescent↗
PubMed1977

Use of the intra-aortic balloon support for refractory low cardiac output in myocardial contusion.

A patient with refractory low cardiac output and recurring ventricular arrhythmias resulting from myocardial contusion was treated with intra-aortic balloon counterpulsation. Use of the intra-aortic balloon resulted in an increased cardiac output and control of the ventricular arrhythmias. After 1 year the patient shows no sequelae of myocardial contusion, although he is still paraplegic.

Assisted Circulation↗
PubMed1983

Cardiac output measurements with thermodilution and radioactive microspheres. A comparative study in cats.

Thermodilution and radioactive microsphere measurements are both commonly used methods for determination of cardiac output in experimental animals. However, no comparison has been made of these methods for cardiac output determination, which is why this study was made. In cats 65 simultaneous measurements of cardiac output with the two methods were performed. No difference in mean values was found and the coefficient of correlation was 0.955 (P less than 0.001). Only eight out of the 65 measurements differed more than 10%. Thermodilution measurements are suitable for repeated determinations and when immediate data are wanted. On the other hand radioactive microsphere measurements are preferable when data on tissue blood flow and blood flow distribution are desired as well. The high correlation found seems to allow cardiac output measurements with these two methods to be grouped together.

Animals↗
PubMed1998

Middle cerebral artery blood velocity depends on cardiac output during exercise with a large muscle mass.

We tested the hypothesis that pharmacological reduction of the increase in cardiac output during dynamic exercise with a large muscle mass would influence the cerebral blood velocity/perfusion. We studied the relationship between changes in cerebral blood velocity (transcranial Doppler), rectus femoris blood oxygenation (near-infrared spectroscopy) and systemic blood flow (cardiac output from model flow analysis of the arterial pressure wave) as induced by dynamic exercise of large (cycling) vs. small muscle groups (rhythmic handgrip) before and after cardioselective beta 1 adrenergic blockade (0.15 mg kg-1 metoprolol i.v.). During rhythmic handgrip, the increments in systemic haemodynamic variables as in middle cerebral artery mean blood velocity were not influenced significantly by metoprolol. In contrast, during cycling (e.g. 113 W), metoprolol reduced the increase in cardiac output (222 +/- 13 vs. 260 +/- 16%), heart rate (114 +/- 3 vs. 135 +/- 7 beats min-1) and mean arterial pressure (103 +/- 3 vs. 112 +/- 4 mmHg), and the increase in cerebral artery mean blood velocity also became lower (from 59 +/- 3 to 66 +/- 3 vs. 60 +/- 2 to 72 +/- 3 cm s-1; P < 0.05). Likewise, during cycling with metoprolol, oxyhaemoglobin in the rectus femoris muscle became reduced (compared to rest: -4.8 +/- 1.8 vs. 1.2 +/- 1.7 mumol L-1, P < 0.05). Neither during rhythmic handgrip nor during cycling was the arterial carbon dioxide tension affected significantly by metoprolol. The results suggest that as for the muscle blood flow, the cerebral circulation is also affected by a reduced cardiac output during exercise with a large muscle mass.

Adrenergic beta-1 Receptor Antagonists↗
PubMed1989

Redistribution of cardiac output to the kidneys by tertatolol does not involve prostaglandins.

Renal perfusion has been shown to be preserved or improved during treatment by tertatolol in patients with arterial hypertension. The aims of the present study were (1) to document the central and renal hemodynamic effects of tertatolol in normal subjects and (2) to look for a possible interaction between tertatolol and products of the cyclooxygenase pathway of arachidonic acid metabolism. Five mg of tertatolol, 1 g aspirin, 5 mg tertatolol together with 1 g aspirin, and placebo were administered to 8 healthy volunteers at 1 week intervals in a random order and in a double-blind fashion. Cardiac output was measured by cardiac Doppler echography and renal blood flow and glomerular filtration rate by constant infusion techniques using I123-iodohippurate and Cr51-EDTA respectively. Measurements were performed before and then successively 2 and 4 h after oral intake of drugs or placebo. Tertatolol alone or with aspirin significantly decreased heart rate and cardiac output (P less than .05) without change in blood pressure, renal blood flow or glomerular filtration rate. The renal fraction of cardiac output was increased by tertatolol alone or with aspirin (P less than .05). Either placebo or aspirin alone had no effect. Thus tertatolol redistributes cardiac output to the kidneys in normal subjects as previously reported in hypertensive patients. This favorable effect on renal hemodynamics appers unlikely to be mediated by a local release of vasodilating prostaglandins.

Adrenergic beta-Antagonists↗
PubMed1984

Right-side cardiac output determined with a newly developed catheter-tip resistivity probe using saline indicator.

Right-heart cardiac output was determined in 10 dogs using a newly developed, highly accurate catheter-tip resistivity probe. A saline indicator was injected into the right atrium and the blood resistivity was monitored at the catheter tip in the pulmonary artery. The resulting dilution curves were calibrated electrically according to the manner in which blood resistivity changes with saline concentration and cardiac output values were calculated. Cardiac output values determined simultaneously by the direct Fick method were used as a reference.

Animals↗
PubMed1977

Measurement of cardiac output by earpiece dye-dilution method with automatic calibration of dye concentration.

A non-invasive method for measuring cardiac output by an earpiece dye densitometer was proposed. The densitometer is dichromatic and has an air capsule to make subject's ear bloodless by inflation, so that it can calibrate indocyanine green dye concentration without blood sampling. Duplicate measurements of cardiac output showed a good agreement in 40 cases (r = 0.97, standard deviation (S.D.) = 8.9%), which was comparable to the result of the cuvette method (r = 0.98, S.D. = 8.1%). Simultaneous measurements of cardiac output by the earpiece method (x) and the standard cuvette method (y) revealed a good agreement (r = 0.91, y = 0.96x+0.34, S.D. = 16.4%) in 52 measurements of 25 cases. A similarly good correlation was obtained between the two methods during ergometer exercise in supine position in 5 cases. These suggest that this earpiece dye-dilution method is reliable for cardiac output measurement and advantageous for clinical use because of non-invasive technique.

Adult↗