Hasse Møller-Sørensen

Lack of agreement and trending ability of the endotracheal cardiac output monitor compared with thermodilution

Minimally invasive monitoring systems of central haemodynamics are gaining increasing popularity. The present study investigated the precision of the endotracheal cardiac output monitor (ECOM) system and its agreement with pulmonary artery catheter thermodilution (PAC TD) for measuring cardiac output (CO) during steady state and with induced haemodynamic changes in patients scheduled for elective cardiac surgery.

Systematic review of cardiac output measurements by echocardiography vs. thermodilution: the techniques are not interchangeable

AbstractPurposeEchocardiography is frequently used in the hemodynamic evaluation of critically ill patients, but inaccurate measurements may lead to wrong clinical decisions. The aim of our systematic review was to investigate the interchangeability of echocardiography with thermodilution technique in measuring cardiac output and its changes.MethodsIn August 2015 we systematically searched electronic databases and included studies investigating the echocardiographic measurement of cardiac output compared with thermodilution technique using the Bland–Altman method. Two authors independently reviewed the studies and extracted data on type of measurements, clinical setting and characteristics, and those of the Bland–Altman and trending ability analyses.ResultsWe identified 13,834 citations and included 24 studies in the final analysis. The median number of participants was 32 (range 8–65). Most of the studies assessed left-sided heart structures and the majority had small bias, wide limits of agreement, and high percentage error between echocardiography and thermodilution. In only two of the 24 studies the precision of each technique (echocardiography and thermodilution) was assessed before comparing them. In the single study evaluating trending ability using valid methodology, agreement was observed between echocardiography and thermodilution in detecting the directional changes in cardiac output, but the magnitude of changes varied considerably.ConclusionsThe majority of studies comparing echocardiography with thermodilution were difficult to interpret, but current evidence does not support interchangeability between these techniques in measuring cardiac output. The techniques may be interchangeable in tracking directional changes in cardiac output, but this has to be confirmed in large high-quality studies.

First report on intraoperative vector flow imaging of the heart among patients with healthy and diseased aortic valves

The vector velocity method Transverse Oscillation (TO) implemented on a conventional ultrasound (US) scanner (ProFocus, BK Medical, Herlev, Denmark) can provide real-time, angle-independent estimates of the cardiac blood flow. During cardiac surgery, epicardial US examination using TO was performed on (A) 3 patients with healthy aortic valve and (B) 3 patients with aortic valve stenosis. In group B, the systolic flow of the ascending aorta had higher velocities, was more aliased and chaotic. The jet narrowed to 44% of the lumen compared to 75% in group A and with a vector concentration, a measure of flow complexity, of 0.41 compared to 0.87 in group A. The two groups had similar secondary flow of the ascending aorta with an average rotation frequency of 4.8 Hz. Simultaneous measurements were obtained with spectral Doppler (SD) and a thermodilution technique (TD). The mean difference in peak systolic velocity compared to SD in group A was 22% and 45% in B, while the mean difference in volume flow compared to TD in group A was 30% and 32% in B. TO can potentially reveal new information of cardiac blood flow, and may become a valuable diagnostic tool in the evaluation of patients with cardiovascular diseases.

Intraoperative cardiac ultrasound examination using vector flow imaging.

Conventional ultrasound (US) methods for blood velocity estimation only provide one-dimensional and angle-dependent velocity estimates; thus, the complexity of cardiac flow has been difficult to measure. To circumvent these limitations, the Transverse Oscillation (TO) vector flow method has been proposed. The vector flow method implemented on a commercial scanner provided real-time, angle-independent estimates of cardiac blood flow. Epicardiac and epiaortic, intraoperative US examinations were performed on three patients with stenosed coronary arteries scheduled for bypass surgery. Repeating cyclic beat-to-beat flow patterns were seen in the ascending aorta and pulmonary artery of each patient, but these patterns varied between patients. Early systolic retrograde flow filling the aortic sinuses was seen in the ascending aorta as well as early systolic retrograde flow in the pulmonary artery. In diastole, stable vortices in aortic sinuses of the ascending aorta created central antegrade flow. A stable vortex in the right atrium was seen during the entire heart cycle. The measurements were compared with estimates obtained intraoperatively with conventional spectral Doppler US using a transesophageal and an epiaortic approach. Mean differences in peak systole velocity of 11% and 26% were observed when TO was compared with transesophageal echocardiography and epiaortic US, respectively. In one patient, the cardiac output derived from vector velocities was compared with pulmonary artery catheter thermodilution technique and showed a difference of 16%. Vector flow provides real-time, angle-independent vector velocities of cardiac blood flow. The technique can potentially reveal new information of cardiovascular physiology and give insight into blood flow dynamics.

Measurements of cardiac output obtained with transesophageal echocardiography and pulmonary artery thermodilution are not interchangeable.

Echocardiography is increasingly becoming an integrated tool for circulatory evaluation in the intensive care unit and the operating room. Therefore, it is imperative to know the reproducibility of measurements obtained by echocardiography. In this study, a comparison of cardiac output (CO) measurements obtained with transesophageal echocardiography (TEE) and pulmonary artery catheter (PAC) thermodilution (TD) was carried out to test the precision, accuracy and trending ability of CO measurements obtained with TEE.

Vector Flow Imaging Compared with Conventional Doppler Ultrasound and Thermodilution for Estimation of Blood Flow in the Ascending Aorta

Transverse oscillation (TO) is a real-time ultrasound vector flow method implemented on a commercial scanner. The TO setup was examined on a flowrig with constant and pulsatile flow. Subsequently, 25 patients undergoing cardiac bypass surgery were scanned intraoperatively with TO on the ascending aorta and compared to transesophageal echocardiography (TEE) and pulmonary artery catheter thermodilution (PACTD). On the flowrig, TO had a precision of 5.5%, 9.4% and 14.7%, a percentage error of 18.2%, 14.6% and 40.7%, and a mean bias of 0.4 cm/s, 36.8 ml/min and 32.4 ml/min for velocity and flow rate (constant and pulsatile) estimation. The correlation coefficients for all flowrig evaluations were 0.99 indicating systematic bias. After bias correction, the percentage error was reduced to 11.5%, 12.6% and 15.9% for velocity and flow rate (constant and pulsatile) estimation. In the in vivo setup, TO, TEE, and PACTD had a precision of 21.9%, 13.7%, and 12.0%. TO compared with TEE and PACTD had a mean bias of 12.6 cm/s and −0.08 l/min, and a percentage error of 23.4%, and 36.7%, respectively. The percentage error was reduced to 22.9% for the TEE comparison, but increased to 43.8% for the PACTD comparison, after correction for the systematic bias found in the flowrig. TO is a reliable and precise method for velocity and flow rate estimation on a flowrig. However, TO with the present setup, is not interchangeable with PACTD for cardiac volume flow estimation, but is a reliable and precise angle-independent ultrasound alternative for velocity estimation of cardiac flow.

Vector flow imaging of the ascending aorta

In the ascending aorta, atherosclerotic plaque formation, which is a risk factor for cerebrovascular events, most often occurs along the inner curvature. Atherosclerosis is a multifactorial disease, but the predilection site for the aortic vessel degradation is probably flow dependent. To better understand the aortic flow and especially the complex flow patterns, the ascending aorta was scanned intraoperatively in patients undergoing heart surgery using the angle-independent vector velocity ultrasound method Transverse Oscillation (TO). The primary aim of the study was to analyze systolic backflow in relation to atherosclerosis. Thirteen patients with normal aortic valves were included in to the study. TO implemented on a conventional US scanner (ProFocus 2202 UltraView, BK Medical, Herlev, Denmark) with a linear array transducer (8670, BK Medical, Herlev, Denmark) was used intraoperatively on the ascending aorta in long axis view. The presence of systolic backflow, visualized with TO, was correlated to aortic atherosclerosis, to systolic velocities obtained with transesophageal echocardiography and cardiac output obtained with pulmonary artery catheter thermodilution, to gender, age, aortic diameter, left ventricular ejection fraction (LVEF) and previous myocardial infarctions (MI). Systolic backflow in the ascending aorta was present for 38% (n=5) of the patients. The location of the backflow was strongly associated to the location of the plaques (p<;0.005), and backflow was associated to high systolic velocities (p<;0.05). The other obtained parameters were not associated to systolic backflow. It was shown that systolic backflow is a common flow feature in the ascending aorta, and that backflow is associated to atherosclerotic plaques and systolic velocities. The study indicates that vector flow imaging using TO can provide important blood flow information in the assessment of atherosclerosis.

Using clinical parameters to guide fluid therapy in high-risk thoracic surgery. A retrospective, observational study.

BackgroundDespite extensive research, the debate continues as to the optimal way of guiding intraoperative and postoperative fluid therapy. In 2009 we changed our institutional guideline for perioperative fluid therapy in patients undergoing extrapleural pneumonectomy (EPP) and implemented the use of central venous oxygen saturation and intended low urine output to guide therapy in the early postoperative period. Here we evaluate the consequences of our changes.MethodsRetrospective, observational study of 30 consecutive patients undergoing EPP; 18 who had surgery before and 12 who had surgery after the changes. Data were collected from patient files and from institutional databases. Outcome measures included: Volumes of administered fluids, fluid balances, length of stays and postoperative complications. Dichotomous variables were compared with Fisher’s exact test, whereas continuous variables were compared with Student’s unpaired t-test or the Wilcoxon Two-Sample Test depending on the distribution of data.ResultsThe applied changes significantly reduced the volumes of administered fluids, both in the intraoperative (p = 0.01) and the postoperative period (p = 0.04), without increasing the incidence of postoperative complications. Mean length of stay in the intensive care unit (LOSI) was reduced from three to one day (p = 0.04) after the changes.ConclusionThe use of clinical parameters to balance fluid restriction and a sufficient circulation in patients undergoing EPP was associated with a reduction in mean LOSI without increasing the incidence of postoperative complications. Due to methodological limitations these results are only hypothesis generating.

Intraoperative vector flow imaging of the heart

The cardiac flow is complex and multidirectional, and difficult to measure with conventional Doppler ultrasound (US) methods due to the one-dimensional and angle-dependent velocity estimation. The vector velocity method Transverse Oscillation (TO) has been proposed as a solution to this. TO is implemented on a conventional US scanner (Pro Focus 2202 UltraView, BK Medical) using a linear transducer (8670, BK Medical) and can provide real-time, angle-independent vector velocity estimates of the cardiac blood flow. During cardiac surgery, epicardiac US examinations using TO were performed on three patients. Antegrade central jet and retrograde flow near the vessel wall in the ascending aorta and the pulmonary artery were seen during systole, while stable vortices were seen in the aortic sinuses and complex flow patterns were seen around the valves during diastole. In the right atrium, a stable vortex was seen during the entire heart cycle. For comparison, simultaneous measurements were obtained with conventional spectral Doppler (SD) and intravenous catheter thermodilution technique (TD). Peak systolic velocities were underestimated by 18% compared to SD and cardiac output was underestimated by 16% compared to TD. This is the first time TO measurements have been obtained of cardiac flow. TO can potentially reveal new information of cardiovascular physiology and blood flow dynamics, and become a valuable tool in cardiology.

NIRS and indocyanine green determined muscle blood flow during exercise in humans

We present a method for determination of muscle blood flow (MBF) using near infrared spectroscopy (NIRS) with indocyanine green (ICG) as the tracer. MBF was quantified using the integrated arterial [ICG] and the accumulation of ICG in muscle. MBF was determined together with ICG-assessed cardiac output (CO) at rest and during incremental cycling. To further modify CO, the same work loads were performed after cardio-selective beta blockade by metoprolol. In one subject both MBF (9 to 110 ml (DOT) 100 g-1 (DOT) min-1) and CO increased linearly with work rate (8 to 19 l (DOT) min-1). Under beta blockade, both the increase in MBF and CO were lower: 5 to 70 ml (DOT) 100 g-1 (DOT) min-1 and 5 to 161 DOT min-1, respectively. During exercise with and without beta blockade, MBF increased with work load to represent a larger proportion of CO. Also, NIRS could detect an attenuated increase in MBF manifest by the restrained CO during leg exercise after cardio-selective beta blockade. Both observations indicate that NIRS detection of indocyanine green provides an estimate of muscle blood flow over the range from rest to intense exercise.