Hemodynamic-induced changes in aortic valve area: implications for Doppler cardiac output determinations.

UNLABELLED: Monitoring cardiac output (CO) by transesophageal echocardiography involves measurements of ascending aortic flow and an initial measurement of aortic valve area (AVA). Hemodynamic-induced changes in AVA are a potential source of error for this simplified method. Our goal was to quantify these changes in AVA and their effects on CO calculations. In 17 anesthetized patients, a dobutamine infusion was titrated to achieve a 50% increase in ascending aortic flow velocity (V(max)). Hemodynamic and echocardiographic variables, including V(max) and planimetry of AVA, were determined at baseline and at maximal dobutamine dose. Dobutamine produced a 3.0 +/- 1.4 L/min increase in CO, a 54.5% +/- 19.6% increase in V(max), and a 50.6% +/- 34.2% increase in systolic blood pressure. AVA increased by 4.3% +/- 2.6% during dobutamine infusion (P < 0.001). The simplified CO method, which does not account for increases in AVA, produced a 0.32 +/- 0.24 L/min underestimation of CO. This investigation demonstrates hemodynamic-induced changes in AVA. The use of a single AVA measurement for all subsequent CO calculations introduces a clinically acceptable degree of error, supporting a simplified CO protocol requiring less probe manipulation and reduced procedural time. IMPLICATIONS: An intraoperative dobutamine infusion was used to increase aortic blood flow and demonstrate hemodynamic-induced changes in aortic valve area. These valve-area changes affect the accuracy of Doppler cardiac output determinations.

Multiplane transesophageal echocardiographic acquisition of ascending aortic flow velocities: A comparison with established techniques.

Acquisition of ascending aortic flow velocities with monoplane transesophageal echocardiography (TEE) have been problematic because of limitations of available imaging planes and alignment of the Doppler beam with aortic flow. The rotatable imaging array of multiplane TEE (Multi TEE) may provide improved alignment with ascending aortic blood flow. The purpose of this study was to establish the validity of maximal aortic flow velocities (VMax) and velocity time integrals (VTI) obtained by a Multi TEE continuous wave Doppler technique by comparison with those obtained by established echocardiographic techniques, suprasternal Doppler (SSD), and monoplane TEE (Mono TEE). Forty-five patients scheduled for elective surgery were prospectively studied. Multi TEE-obtained VMax and VTI were significantly greater (P <.05), 120 +/- 28.9 cm/s and 25.8 +/- 7 cm, than those obtained by the SSD method, 100.2 +/- 28.6 cm/s and 19.8 +/- 6.8 cm, respectively. Bias analysis revealed that Multi TEE better assessed VMax (mean difference -19.7, SD of the difference of 28 cm/s) and VTI (mean difference -5.9, SD of the difference of 6.4 cm) than the SSD method. Multi TEE exhibited values for VMax 10% or greater than those obtained by SSD in 18 (48. 6%) of 37 patients, and Multi TEE was 10% or greater than SSD in 23 (67%) of 37 patients for VTI determination. Values obtained by Multi TEE and Mono TEE showed close agreement. Multi TEE provides a favorable alignment for continuous wave Doppler interrogation of aortic flow and compared favorably to established techniques. This technique expands the utility of TEE to evaluate aortic valvular function and cardiac performance.

Intraoperative determination of cardiac output using multiplane transesophageal echocardiography: a comparison to thermodilution.

BACKGROUND: Limitations in the imaging views that can be obtained with transesophageal echocardiography (TEE) have hindered development of a widely adopted Doppler method for cardiac output (CO) monitoring. The authors evaluated a CO technique that combines steerable continuous-wave Doppler with the imaging capabilities of two-dimensional multiplane TEE. METHODS: From the transverse plane transgastric, short-axis view of the left ventricle, the imaging array was rotated to view the left ventricular outflow tract (LVOT) and ascending aorta. Steerable continuous-wave Doppler was subsequently used to measure aortic blood flow velocities. Aortic valve area was determined using a triangular orifice model. Matched thermodilution and Doppler CO measurements were obtained serially during surgery. RESULTS: The left ventricular outflow tract was imaged in 32 of 33 patients (97%). Data analysis reveal a mean difference between techniques of -0.01 l/min, and a standard deviation of the differences of 0.56 l/min. Multiple regression showed a correlation of r = 0.98 between intrasubject changes in CO. Multiplane TEE correctly tracked the direction of 37 of 38 serial changes in thermodilution CO but with a modest 14% underestimation of the magnitude of these changes. CONCLUSIONS: These results indicate that multiplane TEE can provide an alternative method for the intraoperative measurement of CO. The ability of the rotatable imaging array to align with the left ventricular outflow tract and the need for only minimal adjustments in probe position advance the utility of intraoperative TEE.

Alterations of cardiovascular performance during laparoscopic colectomy: a combined hemodynamic and echocardiographic analysis.

We investigated cardiovascular performance in 12 patients (mean age 66 +/- 12 yr) with significant coexisting cardiopulmonary disease (hypertension, coronary artery disease, chronic obstructive pulmonary disease) during laparoscopic colectomy under general anesthesia. Hemodynamic monitors included arterial and pulmonary artery catheters in combination with transesophageal echocardiography. Hemodynamic and echocardiographic data were obtained at five epochs: baseline (after induction of anesthesia), insufflation (after pneumoperitoneum, supine position), Trendelenburg 5 (5 min after placement into Trendelenburg's position), Trendelenburg 20 (at 20 min in Trendelenburg's position), and end (after release of the pneumoperitoneum, supine position). Hemodynamic responses to peritoneal insufflation resulted in significant increases in systemic vascular resistance (SVR) as well as endsystolic area (ESA) and significant decreases in cardiac index (CI) and ejection fraction area (EFa) compared with baseline. Trendelenburg's positioning augmented ventricular preload and performance, resulting in significant increases in pulmonary capillary wedge pressure, CI, end-diastolic area, and EFa compared with insufflation. At the final epoch, end, a hyperdynamic state occurred as evidenced by a significantly decreased ESA and SVR while heart rate, CI, and EFa increased significantly compared to baseline and insufflation. In an elderly population with significant coexisting cardiopulmonary disease, intraoperative maneuvers required for laparoscopic colectomy resulted in previously undescribed alterations of cardiovascular performance, which persisted after release of the pneumoperitoneum.

A multimedia perioperative record keeper for clinical research.

OBJECTIVE: To develop a multimedia perioperative recordkeeper that provides: 1. synchronous, real-time acquisition of multimedia data, 2. on-line access to the patient's chart data, and 3. advanced data analysis capabilities through integrated, multimedia database and analysis applications. DESIGN: To minimize cost and development time, the system design utilized industry standard hardware components and graphical. software development tools. The system was configured to use a Pentium PC complemented with a variety of hardware interfaces to external data sources. These sources included physiologic monitors with data in digital, analog, video, and audio as well as paper-based formats. DEVELOPMENT: The development process was guided by trials in over 80 clinical cases and by the critiques from numerous users. As a result of this process, a suite of custom software applications were created to meet the design goals. The Perioperative Data Acquisition application manages data collection from a variety of physiological monitors. The Charter application provides for rapid creation of an electronic medical record from the patient's paper-based chart and investigator's notes. The Multimedia Medical Database application provides a relational database for the organization and management of multimedia data. The Triscreen application provides an integrated data analysis environment with simultaneous, full-motion data display. CONCLUSION: With recent technological advances in PC power, data acquisition hardware, and software development tools, the clinical researcher now has the ability to collect and examine a more complete perioperative record. It is hoped that the description of the MPR and its development process will assist and encourage others to advance these tools for perioperative research.

Automated echocardiographic analysis. Examination of serial intraoperative measurements.

BACKGROUND: Although transesophageal echocardiography allows continuous intraoperative cardiac monitoring, the technique has been limited by the lack of a method for realtime, quantitative assessment of cardiac chamber size and systolic function. Automated border detection (ABD), based on an analysis of integrated backscatter, is a new technique that is purported to provide real-time, quantitative assessment of left ventricular (LV) areas and fractional area change (FAC). A prospective investigation was designed to assess the accuracy and trending capability of ABD during continuous intraoperative monitoring. METHODS: In 16 patients monitored throughout noncardiac surgical procedures, serial real-time estimates of LV end-diastolic area (EDA), end-systolic area (ESA), and FAC by ABD were compared with paired off-line manual measurements made by two experiences echocardiographers. RESULTS: There was a high correlation between real-time ABD estimates of LV ESA (r = 0.93), EDA (r = 0.89), and FAC (r = 0.90) to those of the off-line technique. The automated technique systematically underestimated both EDA and ESA, resulting in a small underestimation of FAC. The automated technique demonstrated an accuracy rate of 96% in tracking serial changes in LV area. The technique performed with an 83% sensitivity and 85% specificity for detecting acute changes in LV area. CONCLUSIONS: This analysis of serial intraoperative echocardiograms demonstrates the accuracy of ABD to estimate LV area in real time and to track serial changes in cardiac area during surgery. Although ABD is an automated technique, application by personnel experienced in its operation and an echocardiographic system that includes lateral-gain adjustment controls are recommended for its optimal performance.

Transtracheal Doppler cardiac output monitoring: comparison to thermodilution during noncardiac surgery.

The validity of transtracheal Doppler (TTD) cardiac output (CO) monitoring during noncardiac surgery has not been established. A prospective evaluation was undertaken in 30 patients undergoing noncardiac surgery to assess the agreement between TTD and thermodilution measurements of CO. Linear regression, Bland-Altman analysis, and receiver operator characteristic (ROC) techniques were employed to evaluate the accuracy, reliability, and trending capability of TTD monitoring. A total of 250 simultaneous TTD and thermodilution CO values were compared. TTD and thermodilution CO measurements were highly correlated (P < 0.005, r = 0.84) and Bland-Altman analysis revealed a small systematic underestimation of thermodilution CO (mean bias = -0.25 L/min) with a SD of the bias of 0.88 L/min and a mean percent error of 12.4%. TTD performed particularly well in patients in whom the Doppler signal was stable throughout surgery and required minimal manipulation. In these patients, linear regression yielded the relation TTD CO = 0.96 thermodilution CO + 0.15 with a correlation coefficient r = 0.92. Mean percent error was 10.0% with a mean bias of -0.02 L/min and a SD of the bias of 0.58 L/min. The ability of TTD to track directional changes in thermodilution CO was evaluated by regression analysis and a ROC plot. Changes in TTD CO were highly correlated to changes in thermodilution CO (r = 0.81). ROC plots showed that changes in TTD CO reliably identified large (greater than 15%) changes in thermodilution CO with a sensitivity of 92% and a specificity of 87%. Clinical experience with the TTD device is needed to obtain accurate measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Intraoperative cardiac output monitoring: comparison of impedance cardiography and thermodilution.

Impedance cardiography (IC) is a noninvasive, simple to use method of cardiac output (CO) determination. A prospective evaluation of IC monitoring was performed in 50 patients undergoing noncardiac surgery. IC CO measurements (NC-COM3-Revision 7, BoMed Manufacturing) were compared to simultaneous measurements of thermodilution (TD) CO to assess the validity of this technique for intraoperative cardiac monitoring. Adequate impedance signals could not be obtained in 7 of the 50 patients. IC CO measurements were highly correlated to TD CO (P < .005), with a correlation coefficient r = 0.84. Bias analysis, however, indicated clinically significant disagreement between the two techniques. IC CO tended to underestimate TD CO (mean bias = -0.41 L/min) and the SD of the bias was 1.0 L/min (95% level of agreement 1.6 to -2.4 L/min). Trending data showed IC to accurately track the direction of TD CO changes but to underestimate their magnitude (r = 0.60, intercept -0.7 L/min, slope 0.47). Factors that may have impaired the performance of IC in this study include the high prevalence of cardiac disease in the study population and electrical noise in the operative setting. Further development of IC appears warranted if it is to prove useful as an intraoperative cardiac monitor.

Cardiac output monitoring by echocardiography: should we pass on Swan-Ganz catheters?

Transesophageal echocardiography offers a noninvasive technique for the continuous monitoring of cardiac performance. The combination of 2-dimensional echocardiography and Doppler velocitometry provide assessment of cardiac anatomy, valve function and, ventricular loading conditions. Although transesophageal echocardiography has become accepted for perioperative monitoring, it is typically used in conjunction with Swan-Ganz catheterization. To supplant Swan-Ganz catheters, an echocardiographic technique to monitor cardiac output is necessary. Despite considerable effort to achieve this goal, a satisfactory technique has been difficult to realize. This paper discusses the role of cardiac output monitoring in perioperative care and critically examines echocardiographic techniques for cardiac output monitoring.

Transesophageal Doppler cardiac output monitoring: performance during aortic reconstructive surgery.

Transesophageal Doppler (TED) monitoring provides continuous, noninvasive monitoring of cardiac output by measurement of aortic flow velocities. Because of the effects on aortic flow dynamics resulting from atherosclerosis, aortic cross-clamping, and wide variations in arterial blood pressure, the validity of TED monitoring during aortic surgery is unresolved. The authors prospectively evaluated a second-generation TED cardiac output monitor in 42 patients undergoing aortic reconstructive surgery. Four hundred eighty-nine simultaneous measurements of TED and thermodilution cardiac output were obtained. Transesophageal Doppler measurements were highly correlated to thermodilution measurements (R = 0.94); however, Bland-Altman analysis revealed a moderate error in the TED measurements (2 SD of the bias = 1.4 L/min). Trending analysis showed that TED monitoring accurately tracked changes in thermodilution cardiac output. Placement of an aortic cross-clamp resulted in significant reductions in the accuracy of Doppler measurements. Arterial blood pressure variations did not systematically affect the accuracy of the transesophageal technique. Limitations of TED monitoring, including a difficult calibration procedure, poor performance during aortic cross-clamping, and the need for probe repositioning, suggest further development is warranted.

Transesophageal Doppler ultrasonography: evidence for improved cardiac output monitoring.

Cardiac output monitoring by transesophageal Doppler ultrasound has not gained wide clinical acceptance. A recently developed transesophageal Doppler device, Accucom 2, features technological advances aimed to reduce the error of this approach to the monitoring of cardiac output. To determine if Accucom 2 enables more accurate cardiac output monitoring, a prospective investigation was undertaken. Analyses of 923 simultaneous measurements of transesophageal Doppler and thermodilution cardiac output in 47 anesthetized patients were compared. Results using Accucom 2 were highly correlated with the results obtained with thermodilution (R = 0.91) and provided significantly greater accuracy in comparison with a previously developed Doppler cardiac output monitor, Accucom 1. Technological advances in transesophageal Doppler ultrasound hold promise for clinically useful noninvasive monitoring of cardiac output.