Thermodilution-derived Cardiac Output Research Articles

Central Venous Waveform Analysis and Cardiac Output in a Porcine Model of Endotoxemic Hypotension and Resuscitation.

Cardiac output (CO) is a valuable proxy for perfusion, and governs volume responsiveness during resuscitation from distributive shock. The underappreciated venous system has nuanced physiology that confers valuable hemodynamic information. In this investigation, deconvolution of the central venous waveform by the fast Fourier transformation (FFT) algorithm is performed to assess its ability to constitute a CO surrogate in a porcine model of endotoxemia-induced distributive hypotension and resuscitation. Ten pigs were anesthetized, catheterized, and intubated. A lipopolysaccharides infusion protocol was used to precipitate low systemic vascular resistance hypotension. Four crystalloid boluses (10 cc/kg) were then given in succession, after which heart rate, mean arterial pressure, thermodilution-derived CO, central venous pressure (CVP), and the central venous waveform were collected, the last undergoing fast Fourier transformation analysis. The amplitude of the fundamental frequency of the central venous waveform's cardiac wave (f0-CVP) was obtained. Heart rate, mean arterial pressure, CVP, f0-CVP, and CO were plotted over the course of the boluses to determine whether f0-CVP tracked with CO better than the vital signs, or than CVP itself. Distributive hypotension to a 25% mean arterial pressure decrement was achieved, with decreased systemic vascular resistance (mean 918 ± 227 [SD] dyne/s/cm-5 vs 685 ± 180 dyne/s/cm-5; p = 0.038). Full hemodynamic parameters characterizing this model were reported. Slopes of linear regression lines of heart rate, mean arterial pressure, CVP, f0-CVP, and CO were -2.8, 1.7, 1.8, 0.40, and 0.35, respectively, demonstrating that f0-CVP values closely track with CO over the 4-bolus range. Fast Fourier transformation analysis of the central venous waveform may allow real-time assessment of CO during resuscitation from distributive hypotension, possibly offering a venous-based approach to clinical estimation of volume responsiveness.

Increased FIO2 influences SvO2 interpretation and accuracy of Fick-based cardiac output assessment in cardiac surgery patients: A prospective randomized study.

Introduction:The study aimed to reveal how the fraction of inspired oxygen (FIO2) affected the value of mixed venous oxygen saturation (SvO2) and the accuracy of Fick-equation-based cardiac output (Fick-CO).Methods:Forty two adult patients who underwent elective cardiac surgery were enrolled and randomly divided into 2 groups: FIO2 < 0.7 or >0.85. Under stable general anesthesia, thermodilution-derived cardiac output (TD-CO), SvO2, venous partial pressure of oxygen, hemoglobin, arterial oxygen saturation, arterial partial pressure of oxygen, and blood pH levels were recorded before surgical incision.Results:Significant differences in FIO2 values were observed between the 2 groups (0.56 ± 0.08 in the <70% group and 0.92 ± 0.03 in the >0.85 group; P < .001). The increasing FIO2 values lead to increases in SvO2, venous partial pressure of oxygen, and arterial partial pressure of oxygen, with little effects on cardiac output and hemoglobin levels. When comparing to TD-CO, the calculated Fick-CO in both groups had moderate Pearson correlations and similar linear regression results. Although the FIO2 <0.7 group presented a less mean bias and a smaller limits of agreement, neither group met the percentage error criteria of <30% in Bland-Altman analysis.Conclusion:Increased FIO2 may influence the interpretation of SvO2 and the exacerbation of Fick-CO estimation, which could affect clinical management.Trial Registration:ClinicalTrials.gov ID number: NCT04265924, retrospectively registered (Date of registration: February 9, 2020).

Two- or 3-Dimensional Echocardiography–Derived Cardiac Output Cannot Replace the Pulmonary Artery Catheter in Cardiac Surgery

Three-dimensional (3D) transesophageal echocardiography (TEE) has been shown to be more accurate than 2D TEE for the evaluation of the left ventricular outflow tract area. The aim of the present study was to compare the agreement of 3D echocardiography-derived cardiac output (CO) with thermodilution-derived CO (TDCO) before and after cardiopulmonary bypass (CPB). This was a prospective observational study of patients who underwent cardiac surgery between 2016 and 2018. Weill Cornell Medicine, a single large academic medical center. The study comprised 78 patients undergoing elective cardiac surgery. CPB, TEE, pulmonary artery catheter, and elective cardiac surgery. Two-dimensional CO, 3D CO-diameter, and 3D CO-area values pre-CPB were strongly correlated with one another both pre-CPB and post-CPB. The 3D CO-diameter and the 3D CO-area were mildly correlated, with TDCO measurements pre-CPB (r = 0.46 and 0.39, respectively) and post-CBP (r = 0.43 and 0.47, respectively). Pre-CPB 3D CO-diameter had the most agreement with TDCO in terms of bias (-0.13 L/min); however, the limits of agreement (LOA) were wide (-2.2- to- 2.45 L/min). Post-CPB, 3D CO-diameter had the most agreement with TDCO in terms of bias (0.41) but with wide LOA (-3.29 to 2.47). All pre-CPB echocardiography-derived CO (2D CO, 3D CO-diameter, 3D CO-area) had more agreement with TDCO than did post-CPB measurements. Three-dimensional CO measurements were only modestly correlated with pulmonary artery catheter-derived CO pre-bypass and post-bypass. Despite low bias, the wide LOA from 2D CO, 3D CO-diameter, and 3D-area compared with TDCO suggested that the 2 methods are not interchangeable.

Pulse-contour derived cardiac output measurements in morbid obesity: influence of actual, ideal and adjusted bodyweight

The non-invasive Nexfin cardiac output (CO) monitor shows a low level of agreement with the gold standard thermodilution method in morbidly obese patients. Here we investigate whether this disagreement is related to excessive bodyweight, and can be improved when bodyweight derivatives are used instead. We performed offline analyses of cardiac output recordings of patient data previously used and partly published in an earlier study by our group. In 30 morbidly obese patients (BMI > 35 kg/m2) undergoing laparoscopic gastric bypass, cardiac output was simultaneously determined with PiCCO thermodilution and Nexfin pulse-contour method. We investigated if agreement of Nexfin-derived CO with thermodilution CO improved when ideal and adjusted—instead of actual- bodyweight were used as input to the Nexfin. Bodyweight correlated with the difference between Nexfin-derived and thermodilution-derived CO (r = −0.56; p = 0.001). Bland Altman analysis of agreement between Nexfin and thermodilution-derived CO revealed a bias of 0.4 ± 1.6 with limits of agreement (LOA) from −2.6 to 3.5 L min when actual bodyweight was used. Bias was −0.6 ± 1.4 and LOA ranged from −3.4 to 2.3 L min when ideal bodyweight was used. With adjusted bodyweight, bias improved to 0.04 ± 1.4 with LOA from −2.8 to 2.9 L min. Our study shows that agreement of the Nexfin-derived with invasive CO measurements in morbidly obese patients is influenced by body weight, suggesting that Nexfin CO measurements in patients with a BMI above 35 kg/m2 should be interpreted with caution. Using adjusted body weight in the Nexfin CO-trek algorithm reduced the bias.

Cardiac output measured by uncalibrated arterial pressure waveform analysis by recently released software version 3.02 versus thermodilution in septic shock

To evaluate the 3.02 software version of the FloTrac/Vigileo™ system for estimation of cardiac output by uncalibrated arterial pressure waveform analysis, in septic shock. Nineteen consecutive patients in septic shock were studied. FloTrac/Vigileo™ measurements (COfv) were compared with pulmonary artery catheter thermodilution-derived cardiac output (COtd). The mean cardiac output was 7.7Lmin(-1) and measurements correlated at r=0.53 (P<0.001, n=314). In Bland-Altman plot for repeated measurements, the bias was 1.7Lmin(-1) and 95% limits of agreement (LA) were -3.0 to 6.5Lmin(-1), with a %error of 53%. The bias of COfv inversely related to systemic vascular resistance (SVR) (r=-0.54, P<0.001). Above a SVR of 700 dynscm(-5) (n=74), bias was 0.3 Lmin(-1) and 95% LA were -1.6 to 2.2Lmin(-1) (%error 32%). Changes between consecutive measurements (n=295) correlated at 0.67 (P<0.001), with a bias of 0.1% (95% limits of agreement -17.5 to 17.0%). All changes >10% in both COtd and COfv (n=46) were in the same direction. Eighty-five percent of the measurements were within the 30°-330° of the polar axis. COfv with the latest software still underestimates COtd at low SVR in septic shock. The tracking capacities of the 3.02 software are moderate-good when clinically relevant changes are considered.

Effects of one-lung ventilation on thermodilution-derived assessment of cardiac output

Cardiac output (CO) monitoring can be useful in high-risk patients during one-lung ventilation (OLV), but it is unclear whether thermodilution-derived CO monitoring is valid during OLV. Therefore, we compared pulmonary artery (CO(PATD)) and transcardiopulmonary thermodilution (CO(TPTD)) with an experimental reference in a porcine model. CO(PATD) and CO(TPTD) were measured in 23 pigs during double-lung ventilation (DLV) and 15 min after the onset of OLV, during conditions of normovolaemia and after haemorrhage. An ultrasonic flow probe placed around the pulmonary artery (CO(PAFP)) was used for reference. The range of CO in these experiments was 1.5-3 litre min(-1). Normovolaemia: during DLV and conditions of normovolaemia, the mean (95% limits of agreement) bias for CO(PATD) compared with CO(PAFP) was -0.05 (-0.92 and 0.83) litre min(-1), and 0.58 (-0.40 and 1.55) litre min(-1) for CO(TPTD). During OLV, the bias for CO(PATD) remained unchanged at 0.08 (-0.51 and 0.66) litre min(-1), P=0.15, and the bias for CO(TPTD) increased significantly to 0.85 (0.05 and 1.64) litre min(-1), P=0.047. Hypovolaemia: during DLV, the bias for CO(PATD) compared with CO(PAFP) was 0.22 (-0.20 and 0.66) litre min(-1) and for CO(TPTD) was 0.60 (0.12 and 1.10) litre min(-1). There was no significant change of bias during OLV for CO(PATD) [0.30 (-0.10 and 0.70) (litre min(-1)), P=0.25] or bias CO(TPTD) [0.72 (0.21 and 1.22) (litre min(-1)), P=0.14]. Trending ability during OLV, quantified by the mean of angles θ, showed good values for both CO(PATD) (θ=11.2°) and CO(TPTD) (θ=1.3°). CO(TPTD) is, to some extent, affected by OLV, whereas CO(PATD) is unchanged. Nonetheless, both methods provide an acceptable estimation of CO and particularly of relative changes of CO during OLV.

Comparison of the anesthetic efficacy and cardiopulmonary effects of continuous rate infusions of alfaxalone-2-hydroxypropyl-β-cyclodextrin and propofol in dogs

To compare the cardiopulmonary effects of continuous rate infusions (CRIs) of alfaxalone-2-hydroxypropyl-beta-cyclodextrin (HPCD) and propofol in healthy dogs. 6 young adult medium-sized healthy crossbred dogs. A crossover design was used with a washout period of 6 days between anesthetic treatments. Each dog was sedated with acepromazine (0.02 mg/kg, IV) and hydromorphone (0.05 mg/kg, IV). Anesthesia was induced with propofol (4 mg/kg) or alfaxalone-HPCD (2 mg/kg). After endotracheal intubation, anesthesia was maintained with the same agent (propofol, 0.25 mg/kg/min; alfaxalone-HPCD, 0.07 mg/kg/min) for 120 minutes. Dogs spontaneously breathed 100% oxygen. Measurements included end-tidal partial pressure of carbon dioxide, heart and respiratory rates, mean arterial blood pressure, thermodilution-derived cardiac output, and body temperature. Paired arterial and mixed venous blood samples were collected for determination of blood pH, PaCO(2), and PaO(2). Data were recorded prior to induction; 5, 15, 30, 60, 90, and 120 minutes after induction of anesthesia; and 20 minutes after stopping the CRI, when feasible. Stroke volume and systemic vascular resistance were calculated. Quality of anesthetic induction and recovery and interval to recovery were recorded. Both propofol and alfaxalone-HPCD produced excellent induction of anesthesia, maintenance, and recovery. Respiratory depression was evident with both anesthetics. Clinically acceptable, mild hemodynamic changes were similar for both anesthetics. Alfaxalone-HPCD produced clinically acceptable anesthetic quality and hemodynamic values ideal for use as a CRI. Ventilation may need to be supported if hydromorphone is used at these propofol and alfaxalone-HPCD infusion rates.

Reliability of Cardiac Output Calculation by the Fick Principle and Central Venous Oxygen Saturation in Emergency Conditions

For many years thermodilution has been the gold standard for determining cardiac output in the critically ill patients. Less invasive methods have recently been introduced. This study aimed at evaluating the agreement between cardiac output (CO) measured by a new Fick method, using central venous saturation (Scvo(2)), and that measured by the classic thermodilution technique, in patients requiring emergent CO evaluation. Prospective clinical study in a university-affiliated, tertiary hospital, at surgical and general intensive care units. Fifteen mechanically ventilated patients arriving in the emergency department in hemodynamic shock, had immediately a pulmonary artery catheter introduced under fluoroscopy upon arrival into the ICU. Cardiac output (CO) was obtained in each patient via both thermodilution and the Fick method, using oxygen consumption, SpO(2) and Scvo(2). COs ranged between 2 and 2.3 (in the Fick and thermodilution methods, respectively) and 19 or 19.5 l/min (respectively). Mean thermodilution-derived CO was 6.2 +/- 4.2 l/min whereas the Fick's was 7.0 +/- 4.3 l/min. There was statistical significant correlation between the two modalities of measurements, with an r (2) = 0.9 (P < 0.001). The new method of Fick assessed emergent CO as reliably as the thermodilution, regardless of whether it was low or high. The use of Scvo(2) allows for prompt bedside calculation for most emergency patients.

The Accuracy of Diagnostic and Haemodynamic Data Obtained by Transthoracic Echocardiography in Critically Ill Adults: A Systematic Review

We systematically assessed the utility of diagnostic data and the accuracy of haemodynamic data obtained by transthoracic echocardiography in critically ill adults, by examination of prospective studies in unselected adult intensive care patients. Of the ten studies identified, three examined the diagnostic utility of transthoracic echocardiography. Thirty-eight percent of clinical questions were answered by a single transthoracic echocardiogram. The weighted mean percentage of clinical findings yielded by transoesophageal echocardiography not found by the transthoracic approach was 33% (range 28–50%). Four studies examined the correlation between transthoracic echocardiographic estimation of pulmonary artery occlusion pressure and pulmonary artery catheter-derived measurement. Correlation was strong in all studies: for example in one study r=0.98, p&lt;0.001, with a mean difference of 0.0 (2.5) mm Hg by the Bland-Altman technique. Three studies examined the correlation between transthoracic echocardiography and thermodilution-derived cardiac output measurement. Correlation varied with the echocardiographic technique used and correlated best with Dopplerderived measurement: r=0.93, p&lt;0.0001, mean difference of 0.2 (0.82) litres per minute. The diagnostic utility of transthoracic echocardiography compared with transoesophageal echocardiography in the critically ill cannot be reliably assessed from the available studies. More relevantly designed studies are required. Transthoracic echocardiography can accurately estimate pulmonary artery occlusion pressure, but the technique requires the patient to be in sinus rhythm. Transthoracic echocardiography can also accurately estimate cardiac output in the critically ill. Further studies should concentrate on Doppler-based assessments. The scene is now set for the development of this valuable non-invasive tool.

Influence of extravascular lung water on transpulmonary thermodilution-derived cardiac output measurement

The transpulmonary thermo-dye dilution technique enables assessment of cardiac index (CI) intrathoracic blood volume index (ITBVI) and extravascular lung water index (EVLWI). Since the extent of lung edema may influence the reliability of CI measurement by transpulmonary thermodilution due to loss of indicator, we analyzed the impact of EVLWI on transpulmonary thermodilution-derived CI in critically ill patients. Retrospective, clinical study. Surgical intensive care unit in a university hospital With ethics approval we analyzed data from 57 patients (38 men, 19 women; age range 18-79 years) who, for clinical indication, underwent hemodynamic monitoring by transpulmonary thermo-dye dilution and pulmonary artery thermodilution (572 measurements). All patients were mechanically ventilated and had received a femoral artery thermo-fiberoptic and pulmonary artery catheter which were connected to a computer system (Cold-Z021, Pulsion Medical Systems, Munich, Germany). For each measurement, 15-17 ml indocyanine green(4-6 degrees C) was injected central venously. Injections were made manually and independently from the respiratory cycle. Linear regression was used for statistical analysis. The difference between transpulmonary and pulmonary artery thermodilution CI was not correlated with EVLWIfor all measurements (n=572, r=0.01, p=0.76) and when using only the first simultaneous measurement (n=57, r=0.08, p=0.56). Furthermore, EVLWI was not correlated with transpulmonary thermodilution CI (n=572, r=0.07, p=0.08). Coefficient of variation for transpulmonary thermodilution CI was 7.7+/-4.3%. Measurement of cardiac output by transpulmonary thermodilution is not influenced by EVLWI in critically ill patients and loss of indicator as the underlying reason is probably overestimated.

Pulse dye densitometry using indigo carmine is useful for cardiac output measurement, but not for circulating blood volume measurement.

We evaluated the validity of a newly developed pulse dye densitometer for indigo carmine for measuring cardiac output and circulating blood volume. Measurements of cardiac output and circulating blood volume were performed with the indigo carmine densitometer during normovolaemia, hypovolaemia and hypervolaemia in nine mongrel dogs under general anaesthesia. The validity was evaluated by comparison of the values of cardiac output and circulating blood volume obtained by the thermodilution technique and the 51Cr-labelled red blood cell method, respectively. We also examined indigo carmine removal by continuous veno-venous haemofiltration after indigo carmine injection. There was good agreement between dye densitometer- and thermodilution-derived cardiac output (r = 0.885, P < 0.001). The bias and limits of agreement of these values were 0.09 and+/-1.07 L min(-1) (2 SD, n 22), respectively. The dye-densitometer-derived circulating blood volume was greater than that of the 51Cr-labelled red blood cell method, and both values showed weak agreement (r = 0.587, P < 0.027). The sieving coefficient of indigo carmine through continuous veno-venous haemofiltration was 0.34+/-0.06. These data indicate that indigo carmine densitometry is a reliable method for cardiac output determination, but it overestimates circulating blood volume, probably due to the transition of indigo carmine into the extravascular space in the systemic circulation.

Comparison of continuous cardiac output measurements in patients after cardiac surgery

Objective: To investigate in a direct comparison accuracy and precision of continuous cardiac output measurements assessed by continuous pulmonary artery thermodilution technique (TDCCO), continuous pulse contour analysis (PCCO), and noninvasive partial CO2-rebreathing technique (NICO) in patients after coronary artery bypass grafting (CABG) during the postoperative period. Design: Prospective, controlled clinical study. Setting: University hospital. Participants: Twenty-two patients undergoing elective CABG surgery. Interventions: Hemodynamic measurements were performed after admission to the ICU and in sequence every 2 hours during the subsequent 6-hour period. Simultaneously, cardiac output (CO) was measured using a TDCCO, PCCO, and NICO. After the continuous cardiac output measurements were read, bolus thermodilution-derived cardiac output was obtained from thermodilution curves detected in the pulmonary artery (TDBCOpa). Four intermittent consecutive boli consisting of 10 mL of ice-cold saline were randomly injected over the ventilatory cycle. Measurements and Main Results: The comparison between the continuous cardiac output measurement methods TDCCO versus PCCO showed a bias of −0.12 L/min, between TDCCO versus NICO −0.17 L/min, and between PCCO versus NICO −0.44 L/min. The comparison to the reference technique between TDBCOpa versus TDCCO revealed a bias of −0.28 L/min, between TDBCOpa versus PCCO −0.40 L/min, and between TDBCOpa versus NICO −0.64 L/min. Conclusions: The results of this clinical investigation show agreement between TDCCO and PCCO to satisfy clinical requirements in a setting of postoperative patients after cardiac surgery. In contrast, the NICO monitor is of very limited use in these patients. © 2003 Elsevier Inc. All rights reserved.

Perioperative considerations in the patient with a left ventricular assist device.

Perioperative considerations in the patient with a left ventricular assist device.

Comparison of Continuous Left Ventricular Volumes by Transthoracic Two-Dimensional Digital Echo Quantification with Simultaneous Conductance Catheter Measurements in Patients with Cardiac Diseases

Automated border detection enables real-time tracking of left ventricular (LV) volume by 2-dimensional transthoracic echocardiography. This technique has not been previously compared with simultaneously measured continuous LV volumes at rest or during transients in humans. We performed 18 studies in 16 patients (age 50 ± 15 years, range 22 to 70; ejection fraction 63 ± 20%, range 15% to 85%) in which continuous LV volumes acquired by digital echo quantification (DEQ) were compared with simultaneous conductance catheter volume obtained by cardiac catheterization. Both volume signals were calibrated by thermodilution-derived cardiac output and ventriculogram-derived ejection fraction. Volume traces acquired at rest were averaged to generate a comparison cycle. The averaged volume waveforms acquired by DEQ and by conductance catheter were similar during all phases of the cardiac cycle and significantly correlated (conductance catheter = slope·DEQ + intercept, slope = 0.94 ± 0.09, intercept = 5 ± 8 ml, r2 = 0.86 ± 0.12, all p <0.0001). Steady-state hemodynamic parameters calculated using either averaged volume signal were significantly correlated. Transient obstruction of the inferior vena cava yielded a 45 ± 13% decrease in end-diastolic volume. Successful recordings of DEQ volume during preload reduction were obtained in only 50% of studies. End-diastolic volumes from the 2 methods were significantly correlated (mean slope 0.88 ± 0.31, mean intercept 14 ± 37 ml, average r2 = 0.89 ± 0.11, all p <0.01), as were end-systolic volumes: mean slope 0.80 ± 0.43, intercept = −20 ± 26 ml, r2 = 0.67 ± 0.18, all p <0.05). We conclude that automated border detection technique by DEQ is reliable for noninvasive, transthoracic, continuous tracking of LV volumes at steady state, but has limitations in use during preload reduction maneuvers in humans.

Pulsed Doppler transesophageal echocardiographic determination of cardiac output in human beings: Comparison with thermodilution technique

Measurement of cardiac output is a clinically valuable and widely used index of cardiac function. Although transesophageal echocardiography has been used to assess left ventricular function, little data exist on the accuracy of this technique in the measurement of cardiac output. Therefore cardiac output derived by pulsed Doppler transesophageal echocardiography and thermodilution methods were compared in adult patients being mechanically ventilated. The left ventricular outflow tract diameter was determined from a transgastric long-axis view of the left ventricle by using the transverse plane and longitudinal plane of the transesophageal scope. The cross-sectional area of the left ventricular outflow tract was calculated from the diameter assuming a circular shape. Pulsed Doppler recordings were obtained at the left ventricular outflow tract. Doppler time-velocity integrals were measured from the leading edge of the velocity curve. Cardiac output derived by tranesophageal echocardiography was calculated as time-velocity integral multiplied by left ventricular outflow tract area and heart rate. Cardiac output derived by transesophageal echocardiography from the transverse plane ( n = 26) and longitudinal plane ( n = 22) were correlated with simultaneous thermodilution measurements. Thermodilution-derived cardiac output demonstrated excellent correlation with cardiac output measured by using transesophageal echocardiography from the transverse plane ( r = 0.97, SEE = 0.84 L/min; p < 0.0001) and longitudinal plane ( r = 0.95, SEE = 0.97 L/min; p < 0.0001). Transesophageal echocardiography is a promising technique in the measurement of cardiac output and expands the clinical use of this modality in the assessment of cardiac function.

Validity of cardiac output measurement by the thermodilution method in the presence of acute tricuspid regurgitation

Evaluation of patients with acute tricuspid insufficiency may include assessment of cardiac output by the thermodilution method. The accuracy of estimates of thermodilution-derived cardiac output in the presence of tricuspid insufficiency has been questioned. This study was designed to determine the validity of the thermodilution technique in a canine model of acute reversible tricuspid insufficiency. Cardiac output as measured by thermodilution and electromagnetic flowmeter was compared at two grades of regurgitation. The relationship between these two methods (thermodilution/electromagnetic) changed significantly from a regression slope of 1.01 +/- 0.18 (mean +/- standard deviation) during control conditions to a slope of 0.86 +/- 0.23 (p < 0.02) during severe regurgitation. No significant change was observed between control and mild regurgitation or between the initial control value and a control measurement repeated after tricuspid insufficiency was reversed at the termination of the study. This study shows that in a canine model of severe acute tricuspid regurgitation the thermodilution method underestimates cardiac output by an amount that is proportional to the level of cardiac output and to the grade of regurgitation.

Intraoperative Estimation of Cardiac Output by Transesophageal Pulsed Doppler Echocardiography

To determine whether transesophageal echocardiography could be used to estimate intraoperative cardiac output, the authors studied 35 consecutive patients undergoing cardiovascular surgery (coronary artery disease [n = 22], aortic valve disease [n = 5], mitral valve stenosis [n = 5], peripheral vascular disease [n = 3]). Two-dimensional echocardiographic and pulsed-wave Doppler signals of the pulmonary artery and mitral valve flow velocity were obtained simultaneously with thermodilution measurements of cardiac output. Cardiac output derived from pulsed Doppler imaging of pulmonary artery systolic flow velocity modestly correlated with the thermodilution-derived cardiac output (r = 0.65), but output determined from the mitral valve diastolic flow velocity did not (r = 0.24). Transesophageal echocardiography of pulmonary artery systolic flow satisfactorily detected intraoperative increases in cardiac output greater than 15% (sensitivity, 71%; specificity, 82%) but not decreases (sensitivity, 54%; specificity, 90%). Although this technique identifies increases in cardiac output greater than 15%, it does not detect decreases as accurately as those detected by thermodilution measurements. At this time, therefore, transesophageal Doppler echocardiography has significant limitations as an off-line monitor of cardiac output.

Determination of cardiac output in critically ill patients by dual beam doppler echocardiography

Recent technology in Doppler echocardiography has produced a dual beam Doppler instrument that is capable of insonating the total cross-sectional area of the ascending aorta. The purpose of this study was to evaluate the accuracy of this instrument in measuring cardiac output in critically ill patients by comparing results with those of the thermodilution-derived cardiac output. A technically adequate Doppler cardiac output measurement was attained in 71 (91%) of 78 patients. The range of thermodilution-derived cardiac output measurements was from 1.58 to 11.70 liters/min.To maximize thermodilution cardiac output reliability, several measurements were made for each patient. Those patients in whom the difference between the highest and lowest measurement varied by <10% from the averaged results were accepted into the 50 patient study. There was significant correlation between dual beam Doppler- and thermodilution-derived cardiac output (r = 0.96, SEE = 0.55 liters/min, p < 0.0001). This study demonstrates that dual beam Doppler ultrasound is a promising noninvasive method of measuring cardiac output in the critically ill patient.