Helmut Rauch

Continuous versus intermittent cardiac output measurement in cardiac surgical patients undergoing hypothermic cardiopulmonary bypass

OBJECTIVE Continuous thermodilution cardiac output (CCO) measurement was clinically evaluated in patients who underwent coronary revascularization using hypothermic low-flow, low-pressure cardiopulmonary bypass (CPB). DESIGN Prospective study. SETTING University hospital setting. PARTICIPANTS 30 cardiac surgical patients. INTERVENTIONS CCO was correlated to standard bolus thermodilution cardiac output (ICO) obtained at end-expiration. MEASUREMENTS AND MAIN RESULTS Measurements were taken at selected time points (n = 18) before anesthesia induction, before CPB, and 5 minutes to 12 hours after CPB. A total of 540 data pairs were thus obtained. ICO ranged from 1.9 to 9.9 L/min, CCO from 1.5 to 9.9 L/min. Correlation between ICO and CCO was highly significant (r = 0.872; p < 0.01), accompanied by an excellent accuracy (bias -0.0213 L) and precision (0.59 L) before CPB and more than 45 minutes after CPB. However, during the first 45 minutes after CPB, there was no correlation (r = 0.273) between ICO and CCO, and ICO tended to be relatively high, whereas CCO measurements showed relatively low values. During the first 45 minutes after hypothermic CPB, but not during the ensuing time period, central blood temperature decreased, which may be interpreted as a lack of thermal equilibration between central and peripheral compartments. It is hypothesized that thermal instability in combination with increased respiratory variations in pulmonary artery blood temperature caused inhomogenous rewarming of different body sites and might be the main reason for the lack of correlation between ICO and CCO. CONCLUSIONS Despite an excellent correlation, accuracy, and precision between CCO and ICO before CPB and more than 45 minutes after hypothermic CPB, a lack of correlation in the early phase after CPB has been found. Further investigation is needed to elucidate the underlying cause of these findings and to clarify whether ICO or CCO or both fail to represent the real cardiac output up to 45 minutes after weaning from hypothermic CPB.

Left Ventricular Outflow Tract: Intraoperative Measurement and Changes Caused by Mitral Valve Surgery

BACKGROUND The impact of mitral valve surgery on left ventricular outflow tract (LVOT) dimensions is unclear. Real-time three-dimensional transesophageal echocardiography permits excellent visualization of the LVOT and might improve standard two-dimensional measurements. In this study, LVOT area and shape were assessed before and after mitral valve surgery. METHODS Thirty-five patients undergoing mitral valve repair or replacement were retrospectively included in the study and compared with 15 patients undergoing coronary artery bypass grafting. LVOT area was measured by planimetry. Maximum possible methodologic errors by assuming a circular LVOT and an eccentricity index were calculated. LVOT diameter in a midesophageal long-axis view served to calculate the error for the circular LVOT determined in common intraoperative practice. RESULTS Common intraoperative two-dimensional measurements underestimated actual LVOT area by 21%. Mitral valve surgery led to a significant reduction of LVOT area by 7%. Although LVOT height remained unchanged, width decreased from 2.72 to 2.53 cm (-7%), resulting in a more circular shape of the LVOT. This effect was more pronounced the smaller the size of the implanted annuloplasty ring or prosthesis. Coronary artery bypass grafting did not affect the LVOT. Left ventricular ejection fraction was significantly correlated with LVOT eccentricity. Impaired ventricular function and higher end-systolic volumes were associated with a rounder shape. CONCLUSIONS The eccentric LVOT shape leads to a distinct underestimation of its area with two-dimensional measurements. LVOT eccentricity is less distinct in patients with low ejection fractions and higher end-systolic volumes. LVOT width is decreased through annuloplasty rings and prostheses, and the smaller the implanted device, the more profound the reduction.

Right ventricular function during orthotopic liver transplantation: Three-dimensional transesophageal echocardiography and thermodilution

BACKGROUND Right ventricular (RV) function is an important aspect of anesthesia management during orthotopic liver transplantation (OLT). Because of its geometrical complexity, assessment of RV dimensions with transesophageal echocardiography (TEE) is a difficult task. The aim of this prospective single-site study was to investigate the feasibility of intraoperative assessment of RV parameters based on reconstructive three-dimensional (3D) TEE and to compare the measurements to thermodilution-derived values acquired with a modified pulmonary artery catheter. MATERIAL/METHODS Measurements were performed at four different time points during 30 OLT with 3D-TEE. At the same time comparative values of RV parameters were acquired with a fast-response thermistor pulmonary artery catheter. RESULTS 3D reconstruction was feasible in all patients. RV dimensions measured with 3D-TEE averaged 119.4 ml (± 38.5 ml) for enddiastolic and 68.9 ml (± 27.7 ml) for endsystolic volumes. The RV ejection fraction was 42.2% (± 9.3%). The volumes obtained by thermodilution were 263.7 ml (± 64.5 ml) enddiastolic and 159.3 ml (± 47.5 ml) endsystolic, both significantly greater than by 3D-TEE, and the ejection fraction was found to be 39.5% (± 8.4%). No correlation was found between the volumes or the function determined by either method. CONCLUSIONS Reconstructive 3D-TEE is a viable technique during OLT and leads to plausible RV parameters. However, no correlation was found with simultaneous measurements or parameters performed with thermodilution. However, based on our data cardiac output measurements by thermodilution appear reasonable. Due to both lack of agreement with 3D-TEE and extraordinary high RV volumes the question about the most valuable monitoring technique of RV dimensions and function during OLT can not finally be answered.

Comparison of Intraoperative Three-Dimensional Doppler Color Flow Mapping to Assess Mitral Regurgitation

Background: Three‐dimensional (3D) transesophageal echocardiography (TEE) enables the determination of the vena contracta area (VCA), which is an approved parameter to quantify mitral regurgitation (MR). The aim of this study was to determine the VCA in the operative setting and to compare it to alternative 3D and standard 2D methods, with respect to different etiologies of MR. Methods: MR in 56 consecutive patients undergoing cardiac surgery was evaluated using 2D and 3D TEE. VCA, vena contracta (VC), and effective regurgitation orifice area (EROA) by 3D and 2D flow convergence methods were determined. The correlations among the methods and the determined areas were evaluated. Results: EROA determination using 3D flow convergence areas correlated strongly with VCA (r = 0.653), however the resulting areas were considerably smaller. VC measurements in the 3D data set correlated slightly less (r = 0.629). EROA, which was determined using 2D flow convergence areas, showed the strongest correlation among the 2D methods (r = 0.406). 2D VC measurements showed weak to no correlation with VCA. Although a correlation was detected when using the biplane method or the midesophageal long‐axis view to measure VC, statistical significance was only reached in functional MR and MR due to simple prolapse. Conclusions: Intraoperative 3D methods to determine MR were feasible and showed improved correlation with VCA compared to 2D measurements. The agreement of 2D methods with VCA declined from functional MR to MR due to prolapse. We recommend the utilization of 3D color Doppler for intraoperative evaluation of MR, especially in patients with complex mitral valve prolapses.

Evoked potential monitoring during repeatedly induced ventricular fibrillation for internal defibrillator implantation.

Repeated induction of ventricular fibrillation (VF) with circulatory compromise during implantable cardioverter defibrillator (ICD) testing may cause cerebral injury. To test this hypothesis, somatosensory evoked potentials (SEP), a more sensitive marker of injury, were recorded in patients (N = 10) undergoing ICD implantation. SEP were recorded before induction of anesthesia, after induction of anesthesia, before and at several times following induction of VF. Possible modifying factors of the SEP measurements such as anesthetic application, blood pressure, body temperature, and hematocrit remained constant throughout the operations. Central conduction time was unaffected by ICD defibrillation testing. Amplitude of SEP primary complexes was transiently reduced at 34.9% (P < 0.01) by defibrillation testing, but returned to control within 10 minutes after testing. It is concluded that while ICD defibrillation testing may produce transient changes in SEP, there is no evidence of residual cerebral injury.

Is a 4 days transoesophageal training course sufficient to diagnose shock related pathologies

INTRODUCTION Echocardiography is a useful tool in patients suffering from shock of unknown origin to evaluate cardiac function and volume status in order to decide on further treatment. The aim of the study was to evaluate how well participants could identify function, preload and regional wall motion abnormalities after attending a 4-day transoesophageal echocardiography (TOE) seminar. METHODS In this prospective educational trial, participants of six TOE seminars from 2005 to 2006 were evaluated. On the basis of seven echocardiographic studies, evaluations by participants concerning cardiac function, preload and regional wall motion were analyzed. Moreover, specific causes of undifferentiated hypotension were to be judged in three cases by the participants. RESULTS A total of 115 participants of the TOE seminars from 2005 to 2006 were evaluated. Correct sectional plane was recognized by more than 76% of the participants. Left ventricular function, preload, and regional wall abnormalities were assessed correctly by the participants in 98%, 96%, and 84%, respectively. Moreover, more than 70% of the participants recognized the correct cause of hemodynamic instability. CONCLUSION The results of the investigation show that participants of a 4-day TOE seminar can interpret left ventricular function, preload and regional wall motion abnormalities correctly at a very high rate. TOE seminars seem to be effective in teaching basic theoretical knowledge of TOE.

Image Quality Influences the Assessment of Left Ventricular Function An Intraoperative Comparison of Five 2-Dimensional Echocardiographic Methods With Real-time 3-Dimensional Echocardiography as a Reference

Transesophageal echocardiography has become a standard tool for eval uating left ventricular function during cardiac surgery. However, the image quality varies widely between patients and examinations. The aim of this study was to investigate the influence of the image quality on 5 commonly used 2‐dimensional methods.

Automatic detection of cardiac cycle and measurement of the mitral annulus diameter in 4D TEE images

Mitral regurgitation is a wide spread problem. For successful surgical treatment quantification of the mitral annulus, especially its diameter, is essential. Time resolved 3D transesophageal echocardiography (TEE) is suitable for this task. Yet, manual measurement in four dimensions is extremely time consuming, which confirms the need for automatic quantification methods. The method we propose is capable of automatically detecting the cardiac cycle (systole or diastole) for each time step and measuring the mitral annulus diameter. This is done using total variation noise filtering, the graph cut segmentation algorithm and morphological operators. An evaluation took place using expert measurements on 4D TEE data of 13 patients. The cardiac cycle was detected correctly on 78% of all images and the mitral annulus diameter was measured with an average error of 3.08 mm. Its full automatic processing makes the method easy to use in the clinical workflow and it provides the surgeon with helpful information.

Massive Calcified Tricuspid Valve Endocarditis in a Patient with Dual Lumen Tunneled Venous Catheter

Infection is the most common cause of death in hemodialysis patients after cardiovascular complications. The long-term use of venous catheters for dialysis elevates the risk. Valvular calcification is of special concern in developing infective endocarditis and is often found in chronic dialysis patients. The right-sided endocarditis is rarely reported in the literature and may be overseen until the development of further complications. In our case tricuspid valve endocarditis, with severe insufficiency and stenosis due to a calcified laminar plate was found in a 57-year-old female patient undergoing dialysis due to end-stage renal disease. The calcification aroused from the tip of the dual lumen tunneled venous catheter used for routine dialysis. We replaced the tricuspid valve with mechanical valve prosthesis and reconstructed the right atrium.

Automatische Detektion des Herzzyklus und des Mitralannulus Durchmessers mittels 3D Ultraschall

Mitralklappeninsuffizienz (MI) ist eine weit verbreitete Erkrankung. Fur eine erfolgreiche und nachhaltige chirurgische Therapie ist die Ausmessung des Mitralannulus (MA) notwendig. Wir stellen eine Methode zur automatischen Bestimmung des MA Durchmessers auf Basis von Live-3D Ultraschall Daten vor, die zusatzlich fur jeden Zeitschritt den Herzzyklus detektiert. Dies erreichen wir hauptsachlich durch die Verwendung von Graph Cut Segmentierung und morphologischen Operationen. Die Evaluation anhand von 13 Patienten zeigt, dass der Herzzyklus in 78% aller Zeitschritte korrekt erkannt wurde, wahrend der MA Durchmesser im Mittel 3.08 mm von der Expertenmessung abweicht. Durch die Nutzung des vorgestellten Verfahrens lasst sich die intraoperative Messzeit des MA reduzieren, da die Messung automatisch und praoperativ erfolgen kann.