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PubMed1980

A comparison between freon and acetylene rebreathing for measuring cardiac output.

Cardiac output (CO) was measured in 10 young, healthy male subjects during rest and submaximal exercise on a bicycle ergometer by rebreathing a 2.0-2.8 l (ATPS) gas mixture of acetylene (0.7-1.2%), freon-22 (3-4.2%), argon (6-7%), and oxygen (ca. 40%) in nitrogen. End tidal gas fractions were measured by a mass spectrometer. Argon was used as an inert, insoluble gas for corrections of end tidal acetylene-, freon-, and oxygen fractions. The acetylene results corresponded to cardiac outputs found in literature (6.06 +/- 0.20 l/min, at rest and 15.05 +/- 0.44 l/min at 150 W). The freon values followed those of acetylene but were systematically lower by 0.74 l/min at rest and 1.20 l/min at 150 W. A forced respiratory rate (30-32/min) increased CO and VO2 during rebreathing at rest and lower exercise levels, while a spontaneous respiratory rate (14/min at rest and 22/min at 150 W) did not change VO2 during rebreathing compared to Douglas measurements at steady state. We conclude that freon can be used as the inert, soluble gas in the rebreathing procedure and recommend a spontaneous respiratory rate.

Acetylene↗
PubMed2005

[Measurement of cardiac output after cardiac surgery: validation of a partial carbon dioxide rebreathing (NICO) system in comparison with continuous thermodilution with a pulmonary artery catheter].

UNLABELLED: Cardiac output is usually monitored with a pulmonary artery catheter. However, because that method is not free of risk, devices have been designed in recent years to measure cardiac output in a way that is minimally invasive or fully noninvasive. Among such devices is the NICO monitor, which is based on a modified Fick equation (partial CO2 rebreathing). OBJECTIVE: To compare the accuracy of cardiac output measurements from the NICO monitor to measurements obtained by continuous thermodilution with a pulmonary artery catheter. MATERIAL AND METHODS: A nonprobabilistic, consecutive sample of 20 patients was enrolled in the early postoperative period after elective cardiac surgery (coronary or valve procedures) in the recovery ward. Seven measurements of cardiac output were taken simultaneously with each method in each patient. RESULTS AND CONCLUSIONS: Cardiac output estimated by the partial CO2 rebreathing method was lower than the measurement obtained by the pulmonary artery catheter. The percentage error between the 2 methods was 37%, indicating that the NICO monitor can not substitute for the traditional method. The better correlation found between normal-to-low cardiac output values and the absence of side effects of using the NICO method suggest that it might be indicated for detecting low cardiac output after cardiac surgery, especially when the risk-benefit ratio does not favor using a pulmonary artery catheter.

Aged↗
PubMed1994

Transesophageal echocardiographic measurements of cardiac output in cardiac surgical patients.

Transesophageal echocardiography is becoming increasingly popular as a method of intraoperative monitoring because it can be performed continuously, does not transgress the sterile operative field, and provides data with regard to valve function, ventricular volumes, and contractility. Recently it was suggested that it can be used to measure cardiac output; however, controversy remains regarding its accuracy. Cardiac output was measured simultaneously by transesophageal echocardiography (using a 5-MHz pulse-wave Doppler, single-plane viewing probe) and by the thermodilution method in 21 patients undergoing open heart operations. The cardiac outputs measured by thermodilution correlated poorly (r = 0.45) with the transesophageal values derived from the left ventricular cross-sectional area, and the mean difference was 0.47 +/- 2.17 (standard deviation) L.min-1, giving limits of agreement of from -3.87 to +4.81 L.min-1. Cardiac outputs measured by thermodilution correlated well (r = 0.95) with transesophageal Doppler values derived from pulmonary artery flow velocity, with a mean difference of 0.12 +/- 0.45 L.min-1 and narrow limits of agreement of from -0.78 to +1.02 L.min-1. Based on our findings, transesophageal Doppler echocardiographic determination of cardiac output using pulmonary artery flow measurements can provide accurate hemodynamic data in patients undergoing cardiac operations.

Aged↗
PubMed2006

[Hemodynamic effects of levosimendan compared with dobutamine in patients with low cardiac output after cardiac surgery].

INTRODUCTION AND OBJECTIVES: Levosimendan is an inotropic agent that is effective in the treatment of heart failure. However, experience with levosimendan in patients with reduced cardiac output following cardiopulmonary bypass is limited. The objective of this study was to compare the short-term hemodynamic effects of levosimendan with those of dobutamine in managing low cardiac output after cardiac surgery. METHODS: Forty-one patients who had low cardiac output after cardiopulmonary bypass were randomly assigned to dobutamine (n=20), 24-hour infusion of 7.5 microg/kg per min, or levosimendan (n=21), at a loading dose of 12 microg/kg followed by 24-hour infusion of 0.2 microg/kg per min. The following parameters were determined during a 48-hour observation period: arterial, central venous, pulmonary arterial and pulmonary capillary wedge pressure, cardiac index, heart rate, stroke volume, and systemic and pulmonary vascular resistance. RESULTS: Although both dobutamine and levosimendan improved the cardiac index, the increase was significantly greater with levosimendan (2.4 [0.2] l/min per m2 vs 2.9 [0.3] l/min per m2, respectively, at 24 h; P<.05). Moreover, levosimendan significantly reduced systemic and pulmonary vascular resistance, and significantly decreased systemic arterial, pulmonary arterial, pulmonary capillary wedge, and central venous pressure. CONCLUSIONS: Both dobutamine and levosimendan are effective in managing postoperative low cardiac output. However, levosimendan induces non-specific systemic, venous and pulmonary vasodilation which can result in hypotension as a adverse event. In these patients, it is advisable to omit or reduce the loading dose.

Aged↗
PubMed1992

Prolonged infusion of varied doses of dopexamine hydrochloride for low cardiac output after cardiac surgery.

Circulatory failure after cardiac surgery often calls for active hemodynamic management with fluids, inotropes, and vasodilators. Dopexamine hydrochloride is a new combined beta 2-adrenergic and DA1-dopaminergic receptor agonist and an inhibitor of the uptake-1 mechanism of endogenous catecholamines. As a result, it exerts inotropic and vasodilator effects on the heart and systemic vasculature. The effects were examined over a mean of 22 hours, using 1 to 4 micrograms/kg/min of dopexamine to treat low cardiac output states following coronary bypass and valvular/ventricular repair surgery. In 8 out of 14 patients, low cardiac output was readily reversed by 1 microgram/kg/min of dopexamine. Six patients required higher doses (2 to 4 micrograms/kg/min) to achieve a satisfactory cardiac index. Significant changes from control values were observed throughout the infusion for heart rate (67 to 102 beats/min), cardiac index (2.0 to 3.4 L/min/m2), and systemic vascular resistance (1,545 to 914 dyne.s.cm-5). Pulmonary vascular resistance, pulmonary artery wedge pressure, and right atrial pressure were also significantly reduced during the infusion. Most of these changes reversed when dopexamine was discontinued, suggesting a drug-specific effect and a lack of tolerance. Nausea was a frequent complaint, but was no more frequent than in a random sample of similar patients. Titration of dopexamine, 1 to 4 micrograms/kg/min, was efficacious in producing circulatory improvement in patients with a low cardiac output after cardiac surgery.

Adrenergic Agonists↗
PubMed1993

Indicator amount, temperature, and intrinsic cardiac output affect thermodilution cardiac output accuracy and reproducibility.

OBJECTIVE: To determine the accuracy and reproducibility of four thermodilution indicators (5-mL room temperature, 10-mL room temperature, 5-mL iced, and 10-mL iced injectates) at clinically relevant flow rates. DESIGN: Quasi-experimental study. SETTING: Animal research laboratory of a health sciences university. SUBJECTS: Six virgin western-breed ewes. INTERVENTIONS: Data were collected from six ewes that had ascending aorta electromagnetic flow probes and inferior vena cava occluders. Cardiac output was manipulated by inferior vena cava occlusion and isoproterenol infusion. Four thermodilution indicators were tested at high and low levels of cardiac output and compared with the electromagnetic flowmeter measurements of cardiac output. MEASUREMENTS AND MAIN RESULTS: The indicator amounts were determined from both injectate volume and temperature difference between the injectate and blood. Using 5-mL room temperature injectate as a reference, 10-mL room contained 2 x, 5-mL iced 2.1 x, and 10-mL iced 4.1 x the indicator amount of 5-mL room temperature injectate. Approximately 210 simultaneous thermodilution and electromagnetic flow measurements were made for each injectate over a flow range of 1.5 to 15.7 L/min. For the entire cardiac output range, systematic error was not present. However, the r2 value (.92) for the 10-mL iced injectate group was greater (p < .05) than that value (.79) for the 5-mL iced injectate group, while r2 values were .79 for the 10-mL room temperature group and .49 for the 5-mL room temperature group. At flow rates of < 4.7 L/min, r2 was not different among injectates, but reduced indicator amounts progressively overestimated output (p < .05), reaching 21% for the 5-mL room temperature group. At flow rates of > 7.7 L/min, the r2 value (.81) for the 10-mL iced group was greater (p < .05) than that value (.45) for the 5-mL iced group, while r2 values were .24 for the 10-mL room temperature group and .08 for the 5-mL room temperature group. Systematic error was not present. CONCLUSIONS: At low cardiac output levels, reduced indicator impairs accuracy but not reproducibility, a phenomenon that is perhaps related to indicator loss. At high cardiac output rates, reduced indicator impairs reproducibility. This phenomenon is probably related to low signal-to-noise ratio. Thermodilution indicator amounts should be tailored to the output range.

Animals↗
PubMedDate not supplied

Milrinone and low cardiac output following cardiac surgery in infants: is there a direct myocardial effect?

We assessed the effect of milrinone on myocardial function in pediatric patients with postoperative low cardiac output syndrome by index of myocardial performance in a prospective, open-label, nonrandomized, consecutive study. Fifteen patients with low cardiac output syndrome following cardiac surgical treatment were studied in the tertiary cardiothoracic pediatric intensive care unit between April 2001 and November 2003 (age range, 0.2-16 months; median, 7; weight, 2.7-11.8 kg; median, 5). Echocardiographic, Doppler-derived, time interval-based index of myocardial performance (Tei index) was used to study cardiac function prior to and while on intravenous milrinone treatment for 18-24 hours. Treatment with milrinone led to improvement in biventricular myocardial function [mean right ventricular index from 0.521 (SD-0.213) to 0.385 (SD-0.215), p = 0.003; mean left ventricular index from 0.636 (SD-0.209) to 0.5 (SD-0.171), p = 0.012). No difference was found in the values of heart rate corrected right or left ventricular ejection time prior to and while on treatment with milrinone (right ventricle: mean, 1.23 (SD-0.42) and 1.14 (SD-0.48), p = 0.29; left ventricles: mean, 1.17 (SD-0.51) and 1.13 (SD-0.48), p = 0.66) Our data support the direct myocardial effect of milrinone as part of the mechanism behind its already proven benefit in children with low cardiac output syndrome following cardiac surgery.

Cardiac Output, Low↗
PubMed1991

Continuous extracorporeal fluid removal in children with low cardiac output after cardiac operations.

Eleven hypervolemic and oliguric children with low cardiac output after cardiac operations were treated by slow continuous ultrafiltration or continuous arteriovenous hemofiltration. A mean negative fluid balance of 1.63 +/- 0.37 ml/kg/hr (standard error of the mean [SEM]) significantly improved the hemodynamic status within 59 +/- 6.1 hours (SEM). Although the central venous pressure decreased significantly from 15.2 +/- 0.84 to 8.8 +/- 0.92 mm Hg (p less than 0.0001), the mean arterial pressure increased significantly from 41.5 +/- 2.54 to 53.5 +/- 2.21 mm Hg (p less than 0.001). In addition, pH increased significantly from 7.31 +/- 0.01 (SEM) to 7.43 +/- 0.001 (SEM) (p less than 0.001) and oxygenation index (arterial oxygen tension/inspired oxygen fraction) from 119 +/- 15.2 (SEM) to 214 +/- 27.0 (SEM) (p less than 0.001). Hemodynamic improvement during slow continuous extracorporeal fluid removal allowed a significant decrease of the catecholamine infusion rate. After normovolemia had been achieved, continuous arteriovenous hemofiltration had to be continued in four children because of persistent anuria. Eight patients could be weaned from artificial ventilation and vasopressor support. Two patients died without recovery of renal function and one with restored renal function. Slow continuous ultrafiltration and continuous arteriovenous hemofiltration improve the cardiovascular function in children with low cardiac output by optimizing the preload conditions of the failing heart. In addition, they improve acid-base balance and pulmonary gas exchange.

Blood Pressure↗
PubMed1986

Ultrasound Doppler methods for calculating cardiac volume flows, cardiac output, and cardiac shunts.

The variety of volume flow calculation methods described for determination of cardiac output by Doppler and the controversy surrounding their relative accuracy is to some extent a result of how difficult they are to use and the fact that they break down in patients whose anatomic and physiologic flow cross sections do not match, in patients who may have flow in vessels with flow profiles that are not flat, and in patients who are difficult to examine in one view or another or who do not give clean Doppler waveforms. Nonetheless, most of the methods work to some extent in most patients. Discovering those patients who do not fit the assumptions in these methods and whose cardiac output can therefore not be accurately calculated will probably be a major contribution of the new flow mapping Doppler technologies. We believe these new technologies may provide more sophisticated methods for calculating volume flows, cardiac outputs, regurgitant fractions, and shunt volumes.

Algorithms↗
PubMed1982

Coenzyme Q10: the prophylactic effect on low cardiac output following cardiac valve replacement.

A randomized, prospective study of the effectiveness of preoperative administration of coenzyme Q10 on the prophylaxis of postoperative low cardiac output state was performed in 50 patients with acquired valvular diseases necessitating valve replacement. There were 25 patients in the treatment group and 25 in the control group. Patients in the treatment group received 30 to 60 mg of coenzyme Q10 orally for six days before operation. Preoperative clinical variables, operative procedures, total cardiopulmonary bypass time, and aortic cross-clamping time were similar for the two groups. Postoperatively, mild to severe low cardiac output state developed in 28 of 50 patients (56%) and necessitated the administration of considerable amounts of inotropic agent. The treatment group showed a significantly lower incidence of low cardiac output state during the recovery period than the control group (p less than 0.05). These results suggest that preoperative administration of coenzyme Q10 will increase the tolerance of human hearts to ischemia during aortic cross-clamping.

Adult↗
PubMed2003

Measurement of cardiac output after cardiac surgery by a new transesophageal Doppler device.

OBJECTIVES: Assessment of hemodynamics by transesophageal Doppler devices (TDD) may be a less invasive alternative to the pulmonary artery catheter. In contrast to the TDD evaluated so far, a new monitor (HemoSonic100) measures both blood flow velocity and the diameter of the descending aorta. The aim of this study was to assess the accuracy of the cardiac output/index (CO/CI) measured by this device compared with the CO/CI measured by thermodilution. DESIGN: Prospective nonrandomized study. SETTING: Community hospital; university-based statistician. PARTICIPANTS: Twenty-two patients. INTERVENTIONS: Elective coronary artery bypass grafting and/or valve replacement/repair. MEASUREMENTS AND MAIN RESULTS: After routine cardiac surgery, CO/CI was determined in the intensive care unit by iced-water bolus (IWB), continuous cardiac index (CCI) assessment, and the TDD. Matched measurements were made with each patient at intervals of 30 minutes. Six percent of sets were incomplete because of failed signal detection by the TDD. Bland-Altman analysis revealed a mean bias of 0.23 L/min/m(2) for TDD and IWB. Mean bias for CCI and IWB was 0.11 L/min/m(2). The correlation between TDD and IWB (r(2) = 0.09) for cardiac index was found to be inferior to the correlation between CCI and IWB (r(2) = 0.65). Trend analysis between sequential measurements (T1-4: dTDD, dCCI, dIWB) showed a lower correlation between dTDD and dIWB (r(2) = 0.1) compared with the correlation between dCCI and dIWB (r(2) = 0.44). CONCLUSION: The transesophageal Doppler device (HemoSonic100) cannot be recommended as a sole method for monitoring cardiac output in patients after cardiac surgery.

Aged↗
PubMed1982

Cardiac output and cardiac load during isometric exercise in man.

Cardiac output, heart rate, arterial pressure and indirect left ventricular oxygen consumption have been measured in three subjects during isometric contractions (50-170 kg) of the plantar flexors until fatigue was reached and during walking on a treadmill. Cardiac output was linearly related to VO2 for both exercises. However, for the same VO2, Q was four times higher during isometric effort than during walking. In the last 15 s of static tasks, HR was linearly increasing to VO2 and AP reached values of 160 and 125 Torr (systolic and diastolic respectively) independently of VO2. For comparable VO2 in static and isotonic exercises myocardial O2 uptake was doubled during isometric rather than during the isotonic exercise.

Blood Pressure↗
PubMed1986

A new radiographic method for cardiac output and cardiac shunt determination in vivo.

The present paper describes a new method for the measurement of cardiac output (CO) and cardiac shunt (CS). The CO method is based on the accurate determination of the concentration of the indicator in large vessels. For the measurement of the left to right shunting volumes, a double tracer technique is used by which radioactively labeled transferrin or erythrocytes are applied together with radioactively labelled human-serum-albumin (HSA) microspheres. The results obtained using these methods were compared with the data obtained by invasive methods. High correlation of both sets of data suggests that the proposed methods might provide an excellent extension of noninvasive procedures in the first months of a childs life.

Adult↗
PubMed1998

17beta-estradiol effect on critical cardiac output with reduction of cardiac output in oophorectomized sheep.

Acute administration of 17beta-estradiol (E2beta) leads to increases in cardiac output, oxygen delivery, and oxygen consumption and increases the critical cardiac output in the nonpregnant sheep. We sought to determine whether the lack of a critical cardiac output or flow-dependent oxygen consumption during states of low cardiac output in late gestation can be reproduced in nonpregnant sheep treated with estrogen. We studied five nonpregnant oophorectomized sheep in a randomized crossover design by placing catheters in the pulmonary artery, the right atrium, and the descending aorta. Three experiments were randomly performed on each sheep 3 to 5 days apart: 1) without estrogen or vehicle, 2) 2-3 h after intravenous administration of vehicle, and 3) 2-3 h after intravenous E2beta (3 microg/kg). Cardiac output was gradually reduced while hemodynamic, cardiorespiratory, acid-base, and metabolic variables were simultaneously evaluated. There was a 70% increase in cardiac output in animals given E2beta compared with that in the same animals given either vehicle or nothing (194.0 +/- 13.0, 120.0 +/- 14.5, and 114.0 +/- 16.2 ml . min-1 . kg-1, respectively; P < 0.05). Oxygen consumption was twofold higher in the E2beta series compared with that in the no-treatment and vehicle series (10.01 +/- 1.3, 6.04 +/- 0.77, and 4.52 +/- 0.42 ml O2 . min-1 . kg-1, respectively; P < 0. 05). Tissue oxygen extraction was unaltered by estrogen. However, tissue oxygen extraction at the critical cardiac output was lower in the estradiol group. In relation to oxygen consumption, all three groups demonstrated a critical cardiac output when cardiac output was gradually reduced. However, the level of critical cardiac output was significantly higher in the E2beta group (68.4 +/- 2.4, 42.8 +/- 2.6, and 46.2 +/- 2.6 ml . min-1 . kg-1, respectively; P < 0.05). We conclude that E2beta exhibits increases in systemic tissue blood flow and oxygen consumption. Animals given E2beta show increases in critical cardiac output and impairment of tissue oxygen extraction at critical cardiac output, which leads to development of flow-dependent oxygen consumption at higher cardiac outputs than in the control animals.

Animals↗
PubMed1988

Monitoring of cardiac output and cardiac work during anaesthesia by means of pulsed ultrasound Doppler.

During anaesthesia haemodynamic measurements were performed with pulsed ultrasound Doppler in six patients with a Swan-Ganz catheter. Cardiac output (CO), heart rate (HR), arterial blood pressure (AP), systemic vascular resistance (SVR) and left cardiac work (LCW) were measured simultaneously with the velocity measurements of the bloodstream in the ascending aorta. Six to fourteen (median 9) simultaneous measurements were done in each patient. Sixty-two measurements were made. The velocity (V) and the product of velocity and heart rate (VHR) were compared with CO in order to establish a non-invasive index of the cardiac output. The product of velocity, the heart rate and the arterial blood pressure (VHRAP) was compared with LCW, showing a good correlation between VHR and CO (V = maximum velocity) (rho = median 0.85), as was the case between VHRAP and LCW (rho = 0.88). Furthermore, a negative correlation between V and SVR was found, illustrating that the velocity of the bloodstream in the aorta obviously depends on the afterload. It is concluded that pulsed ultrasound Doppler in combination with HR and AP can measure relative changes in CO and LCW.

Aged↗
PubMed2003

Comparison of thermodilution bolus cardiac output and Doppler cardiac output in the early post-cardiopulmonary bypass period.

OBJECTIVE: To evaluate the accuracy of measuring cardiac output (CO) in the early post-cardiopulmonary bypass (CPB) period by comparing thermodilution with Doppler methods. DESIGN: Prospective and blinded human trial. SETTING: Academic medical center. PARTICIPANTS: Thirty adult patients undergoing elective coronary artery bypass graft surgery. MEASUREMENTS AND MAIN RESULTS: Thermodilution CO (TCO) was obtained in triplicate. Doppler CO (DCO) in triplicate was obtained at the left ventricular outflow tract (LVOT), aortic valve (AV), and right ventricular outflow tract (RVOT). CO measurements were made (1). before CPB (baseline), (2). immediately after CPB, (3).15 minutes after CPB, and (4). 30 minutes after CPB. Before CPB, the DCO at LVOT, RVOT, and AV showed good correlations (r = 0.87, r = 0.88, and r = 0.84, respectively) with TCO. Bias analysis showed no significant difference among TCO and 3 DCOs (p > 0.05 each). Correlation between DCO and TCO decreased but remained significant after CPB (r between 0.57 and 0.85, p < 0.001). The bias among TCO and each of the DCOs at the LVOT, RVOT, and AV increased immediately after CPB (p < 0.01, p < 0.01, and p < 0.05, respectively) and remained significant at 15 minutes and 30 minutes post-CPB except for DCO at the AV. TCO exceeded DCO by 0.44 to 0.72 L/min immediately after CPB. The CO measured by both thermodilution and Doppler methods gradually decreased over time post-CPB. The decrease in CO was significant at 30 minutes post-CPB (p < 0.01). CONCLUSION: This study adds further support that DCO is a clinically acceptable method to accurately assess the CO in patients even during periods of uneven regional body temperatures as may occur in the early post-CPB period.

Aged↗
PubMed2002

Effect of three emergency pacing modalities on cardiac output in cardiac arrest due to ventricular asystole.

Pacing is a well recognised treatment in asystolic arrest with residual p wave activity. This can be achieved by transvenous, transthoracic, or manual external (cardiac percussion) pacing techniques. We report a case of ventricular asystole in which all three pacing modalities were applied, and demonstrate their relative effectiveness with invasive haemodynamic monitoring data. Stroke volumes were comparable with all three methods. Manual external pacing is an effective holding measure when cardiac output is compromised due to bradycardia or asystole with residual p wave activity before more definitive pacing techniques are instituted.

Cardiac Output↗
PubMed1986

Continuous Fick cardiac output compared to thermodilution cardiac output.

A system has been developed to monitor continuously the components of the oxygen Fick equation: oxygen consumption by a gas exchange analyzer and arteriovenous oxygen difference by pulse and fiberoptic oximetry. A computer-based system was developed which calculates cardiac output and other variables every 20 sec. Continuous Fick (CF) cardiac output was compared to thermodilution (TD) cardiac output in 21 ventilated post-cardiac surgery patients. A total of 237 simultaneous cardiac output measurements had a range between 2 and 11 L/min. The correlation between CF and TD cardiac outputs was r = .86, with an equation of TD cardiac output = 0.92 CF cardiac output + 1.16. There was a significant (p less than .001) difference between the two methods of cardiac output estimation. The CF method was consistently lower than TD; this difference was greater at lower flows. CF cardiac output measurement is practical; it offers distinct advantages in viewing cardiac output together with oxygen demand and oxygen extraction.

Cardiac Output↗