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PubMed1995

Comparison of the use of a propofol infusion in cardiac surgical patients with normal and low cardiac output states.

OBJECTIVES: This study compared the hemodynamic effects of a propofol infusion with fentanyl analgesia in patients undergoing cardiac surgery with normal and low cardiac output states. Low cardiac output was defined as a cardiac index less than 2.5 L/min/m2 with a minimum pulmonary capillary wedge pressure of 7 mmHg. DESIGN: A prospective and open study. SETTING: A single center cardiothoracic unit within a teaching hospital. PARTICIPANTS: Patients were assigned to group P, poor cardiac output or group N, normal cardiac output, after thermodilution pulmonary artery catheter assessments. INTERVENTIONS: Both groups received a propofol infusion, 8 mg/kg/hr, until induction of anesthesia, followed by 4 mg/kg/hr until the intensive care unit. Fentanyl, 15 micrograms/kg, and pancuronium, 0.15 mg/kg, were administered after induction. The lungs were ventilated with oxygen. MEASUREMENTS AND MAIN RESULTS: Hemodynamic assessments were repeated at intervals until cardiopulmonary bypass. Changes within and between groups were compared using t tests on percentage change from baseline. Group N had significantly greater decreases in cardiac index, stroke volume, and left ventricular stroke work index than group P. There were comparable decreases in mean arterial pressure on induction of anesthesia, 14% and 8% in group N and group P, respectively. In both groups, right ventricular ejection fraction was unchanged. CONCLUSIONS: The use of a propofol infusion for induction and maintenance of anesthesia in patients with low cardiac output states undergoing cardiac surgery is not contraindicated.

Analgesics, Opioid↗
PubMed1991

Simultaneous intraoperative measurement of cardiac output by thermodilution and transtracheal Doppler.

Intraoperative measurement of cardiac output with transtracheal Doppler (DOP) was compared with that measured by thermodilution (TD). Cardiac output was measured simultaneously with both methods in 17 adult patients. For 86 pairs of measurements, the average difference between the two techniques was -0.21.min-1. This bias had a standard deviation of 1.71.min-1. The average of the absolute value of the difference between measurements made with the two techniques was 1.31.min-1, with a standard deviation of 1.11.min-1. The limits of agreement were -3.6 to 3.11.min-1. Linear regression yielded the following equation: DOP = 0.62 TD + 1.54 l.min-1 (r = 0.63). To evaluate the ability of transtracheal DOP to trend changes in cardiac output, the changes in cardiac output at sequential time points were compared for the two techniques. The average difference in the changes in cardiac output measured by the two techniques was 0.01.min-1. This bias had a standard deviation of 1.71.min-1. In conclusion, the transtracheal DOP technique did not reproduce the measurement of cardiac output by TD intraoperatively. Transtracheal DOP did not accurately trend changes in the TD measurement. These findings were obtained from patients with cardiovascular disease, and the conclusions may depend in part on the patient population and the investigators' experience with the transtracheal DOP technique.

Adult↗
PubMed2005

Pressure recording analytical method (PRAM) for measurement of cardiac output during various haemodynamic states.

BACKGROUND: Cardiac output (CO) can be measured using the pressure recording analytical method (PRAM), which is a new, less invasive technique allowing beat-by-beat stroke volume monitoring from the pressure signals recorded in femoral or radial arteries. METHODS: We investigated PRAM by comparing its cardiac output (PRAM-CO) with paired measurements obtained by electromagnetic flowmetry (EM-CO) and by standard thermodilution (ThD-CO) during various haemodynamic states in a swine model. Nine pigs were monitored with a pulmonary artery catheter and a femoral artery catheter at baseline, in a hyperdynamic state produced by administration of dobutamine and in a hypodynamic state induced by progressive exsanguination. Bland-Altman analysis was used. RESULTS: One hundred and eight paired cardiac output values over a range of EM-CO of 1.8-10.4 litre min(-1) resulted. We found close agreement between the techniques. Mean bias between EM-CO and PRAM-CO was -0.03 litre min(-1) (precision 0.58 litre min(-1)). The 95% limits of agreement were -0.61 to +0.55 litre min(-1). Similar results between ThD-CO and PRAM-CO were found. CONCLUSIONS: In a porcine model we have demonstrated accuracy of PRAM during various haemodynamic states. PRAM is a reliable tool to detect changes in cardiac output in pigs and has ability as a basic research tool.

Analysis of Variance↗
PubMed2005

Evaluation of hemodynamic measurements, including lithium dilution cardiac output, in anesthetized dogs undergoing ovariohysterectomy.

OBJECTIVE: To measure cardiac output in healthy female anesthetized dogs by use of lithium dilution cardiac output and determine whether changes in mean arterial pressure were caused by changes in cardiac output or systemic vascular resistance. DESIGN: Prospective clinical study. ANIMALS: 20 healthy female dogs. PROCEDURE: Dogs were anesthetized for ovariohysterectomy. Ten dogs breathed spontaneously throughout anesthesia, and 10 dogs received intermittent positive-pressure ventilation. Cardiovascular and respiratory measurements, including lithium dilution cardiac output, were performed during anesthesia and surgery. RESULTS: Mean arterial pressure and systemic vascular resistance index were low after induction of anesthesia and just prior to surgery and increased significantly after surgery began. Cardiac index (cardiac output indexed to body surface area) did not change significantly throughout anesthesia and surgery. CONCLUSIONS AND CLINICAL RELEVANCE: Results provide baseline data for cardiac output and cardiac index measurements during clinical anesthesia and surgery in dogs. Changes in mean arterial pressure do not necessarily reflect corresponding changes in cardiac index.

Anesthesia, General↗
PubMed1983

Determination of cardiac output and ejection fraction with the dual cardiac probe.

Cardiac output and left ventricular ejection fraction were determined noninvasively at the bedside in 26 patients by using a dual scintillation probe. The probe is a nonimaging detector that records a high frequency time-activity curve of the passage of an intravenously injected radioactive bolus through the heart. Results were correlated with ejection fraction measured by biplane cineangiography (r = 0.80) and cardiac output determined by green dye dilution (R = 0.86). It is concluded that the dual probe provides an accurate noninvasive means of measuring these parameters, and that it may be particularly applicable to serial measurements in patients in the intensive care unit.

Journal Article↗
PubMed2005

Separating the direct effect of hypoxia from the indirect effect of changes in cardiac output on the maximum pressure difference across the tricuspid valve in healthy humans.

In healthy humans, changes in cardiac output are commonly accommodated with minimal change in pulmonary artery pressure. Conversely, exposure to hypoxia is associated with substantial increases in pulmonary artery pressure. In this study we used non-invasive measurement of an index of pulmonary artery pressure, the maximum systolic pressure difference across the tricuspid valve (DeltaPmax), to examine the pulmonary vascular response to changes in blood flow during both air breathing and hypoxia. We used Doppler echocardiography in 33 resting healthy humans breathing air over 6-24 h to measure spontaneous diurnal variations in DeltaPmax and cardiac output. Cardiac output varied by up to approximately 2.5 l/min; DeltaPmax varied little with cardiac output [0.61+/-0.74 (SD) mmHg min l(-1)]. Eight of the volunteers were also exposed to eucapnic hypoxia (end-tidal PO2 = 50 mmHg) for 8 h. In this group DeltaPmax rose progressively from 21 mmHg to 37 mmHg over 8 h. By comparing diurnal variations in DeltaPmax during air breathing with changes in DeltaPmax during hypoxia in the same eight individuals, we concluded that only approximately 5% of the changes in DeltaPmax during hypoxia could be attributed to concurrent changes in cardiac output. The low sensitivity of DeltaPmax to changes in cardiac output makes it a useful index of hypoxic pulmonary vasoconstriction in healthy humans.

Adult↗
PubMed1982

[Transthoracic electrical impedance plethysmography and thermodilution: comparative evaluation of two methods for cardiac output measurement in man].

The measurement of cardiac output by electrical impedance plethysmography (non invasive technic) seems to be attractive but is still the subject of a certain number of critics. The authors have tried to compare it with a method which validity is well documented, the thermodilution. By these two methods, 87 measures of cardiac output have been performed in 14 hospitalized patients in intensive care, attained of various affections but exempts of cardiac or pulmonary lesions and in stable hemodynamic state. The stroke volume measured by electrical impedance plethysmography is calculated using Kubicek's formula: SV = Q (L2/Zo2) (dz/dt min) t. Results were as follows: absence of significative difference between the coefficients of variation of each series of measures (coefficient of mean variation, 5,6 +/- 3,4 p. cent for impedance and 3,8 +/- 3,2 p. cent for thermodilution); absence of significative difference between the mean values of cardiac output (7,59 +/- 2,69 l . min-1 for impedance and 7,72 +/- 1,99 l . min-1 for thermodilution); highly significant correlation between values for cardiac output obtained for each of these two methods )r = 0,804; n = 87; p less than 0,001). The authors conclude that in patients in intensive care whose pulmonary or cardiovascular system is not in critical situation, the electrical impedance plethysmography appear as a secure method for cardiac output measurement. However its generalisation still require other works.

Adolescent↗
PubMed1980

Blood pressure, not cardiac output, determines blood loss during induced hypotension.

Cardiac output characteristically decreases during trimethaphan infusion but is well maintained or increased during sodium nitroprusside infusion. We postulated that at similar levels of mean arterial pressure, sodium nitroprusside might be associated with greater blood loss than trimethaphan due to the increase in cardiac output. We studied 20 young healthy patients scheduled for bilateral sagittal osteotomies of the mandible. Ten subjects received trimethaphan and 10 subjects received sodium nitroprusside. Using halothane (0.8% to 1%) and nitrous oxide (60%) for maintenance of anesthesia, trimethaphan or sodium nitroprusside was infused to maintain mean arterial pressure between 55 to 60 torr. Cardiac output was measured in five subjects in each group. Heart rate and cardiac output increased significantly and total peripheral resistance decreased significantly during sodium nitroprusside infusion when compared to trimethaphan infusion. There were no significant differences in duration of hypotension or in blood loss. We conclude that operative blood loss during induced hypotension is determined by mean arterial pressure, not cardiac output.

Adolescent↗
PubMed1986

Determination of cardiac output by ultrafast computed tomography.

Three methods of determining cardiac output were compared in six anesthetized dogs (23-28 kg) for the purpose of evaluating the ability of ultrafast computed tomography to measure cardiac output at three points of the circulation: pulmonary artery, left ventricle, and descending aorta. Computed tomography cardiac output is calculated by indicator dilution analysis of an iodinated contrast bolus time-density curve. Computed tomography cardiac output was compared to thermodilution and radioactive microsphere cardiac output methods. The results show very good agreement between thermodilution and computed tomography methods (r = .90) and good agreement between microsphere and computed tomography (r = .88). Comparison of computed tomography cardiac output measurements from the left ventricle and pulmonary artery was excellent (r = .99), as were measurements from the left ventricle and descending aorta (r = .97). This study also showed minimal interlevel scan-density response variability (3%) and minimal variability between experiments (7%). Therefore, it is concluded that cardiac output can be accurately measured at many points in the blood pool by ultrafast computed tomography.

Animals↗
PubMedDate not supplied

A non-invasive method for measuring cardiac output: the effect of Christmas lunch.

Cardiac output was measured in ten patients at routine cardiac catheterisation and three patients with severe heart failure by means of a carbon dioxide rebreathing technique with a computer-assisted mass spectrometer and compared with cardiac output measured by thermodilution. There was a close correlation (r = 0.96, p less than 0.01) between the two methods. Cardiac output measured by the carbon dioxide rebreathing technique increased after a typical Christmas lunch by a mean of 1.6 1/min in a group of healthy volunteers.

Carbon Dioxide↗
PubMed1981

Reliability of echocardiography in assessing cardiac output. A comparative study with a dye dilution technique.

Because of the potential benefits froma noninvasive technique in assessing cardiac output, we compared cardiac output estimates from left ventricular echocardiograms with results obtained simultaneously by a standard technique, dye dilution in 10 healthy normal volunteers. During rest, cardiac outputs by echocardiographic and dye dilution techniques were reproducible and not significantly different. Increases in cardiac output produced by intravenous infusion of isoproterenol (15 ng/kg/min for 4 min) were accurately estimated by echocardiography in subjects whose stroke volume increased less than 40%, but were significantly underestimated when stroke volume increased more than 40%. Decreased cardiac output produced by intravenous propranolol (0.2 mg/kg) was comparable by both methods. Although echocardiography accurately estimated mean cardiac output for the group it over- or underestimated cardiac output in individual subjects. We propose that echocardiography can reliably estimate cardiac output in groups at rest and when stroke volume changes less than 40%.

Cardiac Output↗
PubMed1990

Inconsistent esophageal Doppler cardiac output during acute blood loss.

Application of the Doppler principle can provide relatively noninvasive and continuous measurement of cardiac output. However, it is based on certain assumptions that may introduce error. Esophageal Doppler cardiac output was compared with Fick cardiac output during acute blood loss (35-45% estimated blood volume) in eight anesthetized pigs. Mean Fick cardiac output decreased from 4.8 to 1.9 l/min, mean Doppler cardiac output from 4.9 to 2.9 l/min. This was accompanied by a decrease in mean arterial pressure from 119 to 55 mmHg and increase in heart rate from a mean of 115 to 156 beats/min. There was an inconsistent association between the two methods both within and between individual animals. Cubic polynomial regression equations of cardiac output with time indicated small measurement error in Fick (R2: mean 0.93, range 0.99-0.75) as opposed to Doppler (R2: mean 0.67, range 0.93-0.16) cardiac output. In one animal Doppler cardiac output showed an increase with time and in one the Doppler cardiac output measurements were unrelated to time. There was highly variable association comparing Fick versus Doppler cardiac output with correlations ranging from -0.76 to 0.98. A sign test for mean differences indicated that Doppler derived cardiac output was higher than Fick cardiac output, and the chance of this occurring if the true difference was zero was less than 1 in 1,000. A test for homogeneity of correlations was also rejected. Inaccuracies in individual assumptions in the computation of esophageal Doppler cardiac output, especially unaccounted changes in aortic diameter, are responsible for the inconsistent and unpredictable values of Doppler cardiac output obtained in this experimental model of hemorrhage.

Acute Disease↗
PubMed1975

Cardiac output in the conscious and anaesthetised horse.

Cardiac output in the horse was measured before and at predetermined times during 2-hour periods of thiopentone-halothane and thiopentone-diethyl ether anaesthesia. Left ventricular stroke volume was decreased to a similar extent during anaesthesia with each volatile agent, but a greater reduction in cardiac output occurred during halothane anaesthesia. This finding reflected the differing effects of halothane and ether on heart rate, a slight bradycardia occurring with the former agent while ether produced a small degree of tachycardia. The latter effect was attributed to enhanced sympathoadrenal activity. Changes in cardiac output and stroke volume were considered in relation to other factors, including arterial blood pH and tensions of oxygen and carbon dioxide. Positive correlations between some of these variables and cardiac function were established. With both volatile agents the reductions in stroke volume and cardiac output were related to the duration of anaesthesia, being greatest during the early stages. Possible reasons for the tendency of stroke volume and cardiac output to return towards control levels are discussed.

Anesthesia, Inhalation↗
PubMedDate not supplied

[Monitoring cardiac output: esophageal doppler vs thermodilution].

OBJECTIVE: Evaluation of continuous cardiac output monitoring based on the esophageal Doppler in the critically ill. DESIGN: Prospective clinical investigation. SETTING: An intensive care unit of an University hospital. PATIENTS: Ten critically ill patients who needed pulmonary artery catheterization. MEASUREMENTS: Cardiac output was monitored continuously by a transesophageal Doppler device, consisting of an esophageal probe and a bedside microprocessor that calculated cardiac output using a new algorithm. Standard bolus thermodilution technique (10 ml of saline solution) was used to compare the continuous Doppler cardiac output measurement with the intermittent bolus measurement. MAIN RESULTS: A total of 50 pairs of intermittent (bolus) cardiac output and continuous (Doppler) cardiac output measurements were obtained from the 10 patients. The mean value of CO measured with TD was 5.81 +/- 0.83, while using esophageal Doppler was 5.84 +/- 0.81. The correlation coefficient of the two methods was r = 0.93. The Bland and Altman showed 95% of agreement limits as +0.52 and -0.64 L/min. CONCLUSIONS: Continuous monitoring of cardiac output using esophageal Doppler has proven to be safe, accurate, and precise when compared with the standard intermittent bolus thermodilution technique. The continuous monitoring technique improves our armamentarium for more intensive monitoring of the critically ill patients.

Adult↗
PubMed1991

[Transesophageal Doppler echocardiographic measurement of cardiac output using mitral anulus method].

The method of measuring cardiac output with transesophageal pulsed Doppler two-dimensional echocardiography was developed and validated by comparison with the thermodilution technique in 65 adult patients. With the use of transesophageal four-chamber view, the Doppler sample volume was placed in the center of the mitral ring and the mitral flow velocity-time integral was obtained through planimetric measurements of the mitral flow velocity curve. The diameter of the mitral valve anulus was measured at the time of peak rapid filling flow velocity, and the cross-sectional area of the mitral valve anulus was calculated, assuming a circular shape. Doppler-determined cardiac output was calculated by using the following formula: Cardiac output [1.min-1] = pi (D [cm] /2)2.MFVI [cm].heart rate [bpm].10(-3), where MFVI is mitral flow velocity-time integral, and D is the diameter of the mitral valve anulus. There was a weak correlation between thermodilution and Doppler measurements of cardiac output (r = 0.64, p less than 0.01), while a good correlation was observed between percent changes in thermodilution-derived cardiac output and those in Doppler-determined cardiac output (r = 0.92, p less than 0.01) during different loading conditions. It has been suggested that this method may be useful for assessing relative changes in cardiac output during short time periods.

Adult↗
PubMed1993

Arterial pulse contour analysis trending of cardiac output: hemodynamic manipulations during cerebral arteriovenous malformation resection.

OBJECTIVE: Intravascular pressure and cardiac output monitoring are frequently performed in the operating room and intensive care unit. Currently, cardiac output is only measured intermittently, although continuous measurement would be preferable. One method proposed for measuring cardiac output continuously is arterial waveform pulse contour analysis. This study examines the utility of trending cardiac output using pulse contour analysis during manipulations of blood pressure. METHODS: Eleven patients were studied while undergoing resection of cerebral arteriovenous malformations. Cardiac output measured by pulse contour analysis was compared with thermodilution cardiac output measurements in patients subjected to induced hypotension with esmolol and restoration of blood pressure with phenylephrine. RESULTS: Esmolol infusion resulted in a decrease in mean arterial pressure from 81 +/- 13 to 62 +/- 7 mm Hg (p < 0.025), a decrease in thermodilution cardiac output from 6.4 +/- 0.9 to 4.4 +/- 1.1 L/min (p < 0.025), and a decrease in pulse contour cardiac output from 6.2 +/- 1.0 to 4.5 +/- 0.9 L/min. Phenylephrine increased mean arterial pressure from 68 +/- 6 to 95 +/- 9 mm Hg with no change in either thermodilution or pulse contour cardiac output. CONCLUSIONS: This study demonstrates that during surgery for arteriovenous malformations in the brain, the pulse contour method was able to reflect cardiac output accurately during induced hypotension with esmolol and during restoration of blood pressure with phenylephrine.

Adolescent↗
PubMed2002

Comparison of lithium dilution and thermodilution cardiac output measurements in anaesthetised neonatal foals.

Knowledge of cardiac output is expected to help guide the treatment of hypotension associated with critical illness and/or anaesthesia in neonatal foals. However, a practical and safe method of measuring cardiac output has not been described for the foal. Lithum dilution, a new method of cardiac output determination not requiring cardiac catheterisation, has recently been reported in mature horses. We compared this method to thermodilution in isoflurane-anaesthetised foals age 30-42 h and found good agreement between the 2 methods in a range of cardiac outputs 5.4-20.4 l/min. The lithium dilution technique is a practical and reliable method of measuring cardiac output in anaesthetised neonatal foals, and warrants investigation in critically ill conscious foals.

Animals↗
PubMed2006

Cardiac output measurement by pulse dye densitometry: comparison with pulmonary artery thermodilution in post-cardiac surgery patients.

OBJECTIVE: Pulse-dye densitometry (PDD) could be a suitable, low-invasive alternative to thermodilution using a pulmonary artery catheter (PAC) for monitoring cardiac output. The aim of our study was to assess the reproducibility and validity of PDD compared to PAC-thermodilution. METHODS: In 43 post-cardiac surgery patients, the mean of triplicate readings of cardiac output was assessed using both methods. In a subgroup of 26 patients, a second set of measurements was obtained on average 2 h later. RESULTS: Reproducibility of consecutive measurements was slightly better for PAC-thermodilution than for PDD (median coefficient of variation of the triplicate measurements: 3.5% versus 5.4%, P < 0.01). Both methods correlated well (r = 0.84, p < 0.001). Using Bland and Altman analyses with PAC-thermodilution as the reference method, PDD showed a bias of -0.68 +/- 0.82 L/min, mainly due to differences in higher ranges of cardiac output (>6.5 L/min). Measured changes in cardiac output were 81% concordant (i.e. <1 L/min different) between both methods. CONCLUSION: PDD correlates well with PAC-thermodilution and thus deserves consideration as a low-invasive alternative for measurement and follow-up of cardiac output.

Aged↗