Nils Siegenthaler

Validation of a new transpulmonary thermodilution system to assess global end-diastolic volume and extravascular lung water

IntroductionA new system has been developed to assess global end-diastolic volume (GEDV), a volumetric marker of cardiac preload, and extravascular lung water (EVLW) from a transpulmonary thermodilution curve. Our goal was to compare this new system with the system currently in clinical use.MethodsEleven anesthetized and mechanically ventilated pigs were instrumented with a central venous catheter and a right (PulsioCath; Pulsion, Munich, Germany) and a left (VolumeView™; Edwards Lifesciences, Irvine, CA, USA) thermistor-tipped femoral arterial catheter. The right femoral catheter was used to measure GEDV and EVLW using the PiCCO2™ (Pulsion) method (GEDV1 and EVLW1, respectively). The left femoral catheter was used to measure the same parameters using the new VolumeView™ (Edwards Lifesciences) method (GEDV2 and EVLW2, respectively). Measurements were made during inotropic stimulation (dobutamine), during hypovolemia (bleeding), during hypervolemia (fluid overload), and after inducing acute lung injury (intravenous oleic acid).ResultsOne hundred and thirty-seven paired measurements were analyzed. GEDV1 and GEDV2 ranged from 701 to 1,629 ml and from 774 to 1,645 ml, respectively. GEDV1 and GEDV2 were closely correlated (r2 = 0.79), with mean bias of -11 ± 80 ml and percentage error of 14%. EVLW1 and EVLW2 ranged from 507 to 2,379 ml and from 495 to 2,222 ml, respectively. EVLW1 and EVLW2 were closely correlated (r2 = 0.97), with mean bias of -5 ± 72 ml and percentage error of 15%.ConclusionsIn animals, and over a very wide range of values, a good agreement was found between the new VolumeView™ system and the PiCCO™ system to assess GEDV and EVLW.

Clinical validation of a new thermodilution system for the assessment of cardiac output and volumetric parameters

IntroductionTranspulmonary thermodilution is used to measure cardiac output (CO), global end-diastolic volume (GEDV) and extravascular lung water (EVLW). A system has been introduced (VolumeView/EV1000™ system, Edwards Lifesciences, Irvine CA, USA) that employs a novel algorithm for the mathematical analysis of the thermodilution curve. Our aim was to evaluate the agreement of this method with the established PiCCO™ method (Pulsion Medical Systems SE, Munich, Germany, clinicaltrials.gov identifier: NCT01405040)MethodsSeventy-two critically ill patients with clinical indication for advanced hemodynamic monitoring were included in this prospective, multicenter, observational study. During a 72-hour observation period, 443 sets of thermodilution measurements were performed with the new system. These measurements were electronically recorded, converted into an analog resistance signal and then re-analyzed by a PiCCO2™ device (Pulsion Medical Systems SE).ResultsFor CO, GEDV, and EVLW, the systems showed a high correlation (r2 = 0.981, 0.926 and 0.971, respectively), minimal bias (0.2 L/minute, 29.4 ml and 36.8 ml), and a low percentage error (9.7%, 11.5% and 12.2%). Changes in CO, GEDV and EVLW were tracked with a high concordance between the two systems, with a traditional concordance for CO, GEDV, and EVLW of 98.5%, 95.1%, and 97.7% and a polar plot concordance of 100%, 99.8% and 99.8% for CO, GEDV, and EVLW, respectively. Radial limits of agreement for CO, GEDV and EVLW were 0.31 ml/minute, 81 ml and 40 ml, respectively. The precision of GEDV measurements was significantly better using the VolumeView™ algorithm compared to the PiCCO™ algorithm (0.033 (0.03) versus 0.040 (0.03; median (interquartile range), P = 0.000049).ConclusionsFor CO, GEDV, and EVLW, the agreement of both the individual measurements as well as measurements of change showed the interchangeability of the two methods. For the VolumeView method, the higher precision may indicate a more robust GEDV algorithm.Trial registrationclinicaltrials.gov NCT01405040.

Performance of a new pulse contour method for continuous cardiac output monitoring: validation in critically ill patients

BACKGROUND A new calibrated pulse wave analysis method (VolumeView™/EV1000™, Edwards Lifesciences, Irvine, CA, USA) has been developed to continuously monitor cardiac output (CO). The aim of this study was to compare the performance of the VolumeView method, and of the PiCCO2™ pulse contour method (Pulsion Medical Systems, Munich, Germany), with reference transpulmonary thermodilution (TPTD) CO measurements. METHODS This was a prospective, multicentre observational study performed in the surgical and interdisciplinary intensive care units of four tertiary hospitals. Seventy-two critically ill patients were monitored with a central venous catheter, and a thermistor-tipped femoral arterial VolumeView™ catheter connected to the EV1000™ monitor. After initial calibration by TPTD CO was continuously assessed using the VolumeView-CCO software (CCO(VolumeView)) during a 72 h period. TPTD was performed in order to obtain reference CO values (COREF). TPTD and arterial wave signals were transmitted to a PiCCO2™ monitor in order to obtain CCO(PiCCO) values. CCO(VolumeView) and CCO(PiCCO) were recorded over a 5 min interval before assessment of CO(TPTD). Bland-Altman analysis, %(errors), and concordance (trend analysis) were calculated. RESULTS A total of 338 matched sets of data were available for comparison. Bias for CCO(VolumeView)-CO(REF) was -0.07 litre min(-1) and for CCO(PiCCO)-CO(REF) +0.03 litre min(-1). Corresponding limits of agreement were 2.00 and 2.48 litre min(-1) (P<0.01), %(errors) 29 and 37%, respectively. Trending capabilities were comparable for both techniques. CONCLUSIONS The performance of the new VolumeView™-CCO method is as reliable as the PiCCO2™-CCO pulse wave analysis in critically ill patients. However, an improved precision was observed with the VolumeView™ technique. CLINICALTRIALS.GOV IDENTIFIER: NCT01405040.

Transpulmonary thermodilution curves for detection of shunt

PurposeMonitoring using transpulmonary thermodilution (TPTD) via a single thermal indicator technique allows measurement of cardiac output, extravascular lung water (EVLW) and volumetric variables.Methods and resultsThis report describes two cases of systemic-venous circulation shunt generating early recirculation of thermal indicator with overestimation of EVLW.ConclusionIn the case of recirculation of thermal indicator, the observed overestimated EVLW in absence of gas exchanges abnormality could be an indicator suggesting the search for a circulatory shunt.

ScvO(2) as a marker to define fluid responsiveness

BACKGROUND Definition of the hemodynamic response to volume expansion (VE) could be useful in shocked critically ill patients in absence of cardiac index (CI) measurements. The aim of this study is to evaluate whether central venous oxygen saturation variations (ΔScvO(2)) after VE could be an alternative to classify responders (R) and nonresponders (NR) to volume therapy. METHODS A total of 30 patients requiring VE were included in this prospective cohort study, all equipped with radial arterial line and pulmonary artery catheters. CI, mixed venous oxygen saturation (SvO(2)) and ScvO(2) were measured before and after VE. CI, SvO(2), and ScvO(2) changes after volume were analyzed using linear regression. Receiver operating characteristics curve analysis was used to test their ability to distinguish R and NR. RESULTS ΔScvO(2) and SvO(2) variations after VE (ΔSvO(2)) were significantly correlated with CI changes (ΔCI) after VE (r = 0.67 and r = 0.49, p < 0.001, respectively). A ΔScvO(2) threshold value of 4% allowed the definition of R and NR patients with 86% sensitivity (95%CI; 57-98%) and 81% specificity (95%CI; 54-96%). CONCLUSIONS ScvO2 variations after VE was able to categorize VE efficiently and could be suggested as an alternative marker to define fluid responsiveness in absence of invasive CI measurement.

Pulmonary fluid status monitoring with intrathoracic impedance

Various pacemakers can now track diverse hemodynamic parameters that are useful in the management of patients with heart failure. Among these indicators, pulmonary fluid status can be monitored. To the best of our knowledge, this is the first case describing an agreement between a simultaneous detection of an increase in lung water by transthoracic impedance monitoring (OptiVolTM (Medtronic, Inc., Minneapolis, MN), and the transpulmonary thermodilution method (PiCCOTM, Pulsion Medical Systems, Munich, Germany) in a patient with acute pulmonary oedema. The present case suggests that transthoracic impedance monitoring could be a useful tool to guide therapy in critically ill patients with implanted devices and lung fluid congestion.

Cardiac index during therapeutic hypothermia: which target value is optimal?

Mild therapeutic hypothermia is now recognized as standard therapy in patients resuscitated from out-of-hospital cardiac arrest (OHCA), and is recommended in comatose patients suffering from cardiac arrest related to ventricular fibrillation (VF) [1]. In these patients, maintaining an adequate tissue oxygen delivery (DO2) is crucial. However, during hypothermia, clinical signs of hypoperfusion such as cold, clammy skin and delayed capillary refill are not reliable and monitoring devices must, therefore, be used to measure or estimate the cardiac index (CI). However, there are no recommendations regarding the target value of CI in the hypothermic patient. In this article, the authors attempt to provide clinicians with some rationale to guide their therapy for the management of CI in patients treated with mild therapeutic hypothermia.

Monitoring CO2 in shock states

The primary end point when treating acute shock is to restore blood circulation, mainly by reaching macrocirculatory parameters. However, even if global haemodynamic goals can be achieved, microcirculatory perfusion may remain impaired, leading to cellular hypoxia and organ damage. Interestingly, few methods are currently available to measure the adequacy of organ blood flow and tissue oxygenation. The rise in tissue partial pressure of carbon dioxide (CO2) has been observed when tissue perfusion is decreased. In this regard, tissue partial pressure of CO2 has been proposed as an early and reliable marker of tissue hypoxia even if the mechanisms of tissue partial pressure in CO2 rise during hypoperfusion remain unclear. Several technologies allow the estimation of CO2 content from different body sites: vascular, tissular (in hollow organs, mucosal or cutaneous), and airway. These tools remain poorly evaluated, and some are used but are not widely used in clinical practice. The present review clarifies the physiology of increasing tissue CO2 during hypoperfusion and underlines the specificities of the different technologies that allow bedside estimation of tissue CO2 content.

Impact of epinephrine and norepinephrine on two dynamic indices in a porcine hemorrhagic shock model.

BACKGROUND Pulse pressure variations (PPVs) and stroke volume variations (SVVs) are dynamic indices for predicting fluid responsiveness in intensive care unit patients. These hemodynamic markers underscore Frank-Starling law by which volume expansion increases cardiac output (CO). The aim of the present study was to evaluate the impact of the administration of catecholamines on PPV, SVV, and inferior vena cava flow (IVCF). METHODS In this prospective, physiologic, animal study, hemodynamic parameters were measured in deeply sedated and mechanically ventilated pigs. Systemic hemodynamic and pressure-volume loops obtained by inferior vena cava occlusion were recorded. Measurements were collected during two conditions, that is, normovolemia and hypovolemia, generated by blood removal to obtain a mean arterial pressure value lower than 60 mm Hg. At each condition, CO, IVCF, SVV, and PPV were assessed by catheters and flow meters. Data were compared between the conditions normovolemia and hypovolemia before and after intravenous administrations of norepinephrine and epinephrine using a nonparametric Wilcoxon test. RESULTS Eight pigs were anesthetized, mechanically ventilated, and equipped. Both norepinephrine and epinephrine significantly increased IVCF and decreased PPV and SVV, regardless of volemic conditions (p < 0.05). However, epinephrine was also able to significantly increase CO regardless of volemic conditions. CONCLUSION The present study demonstrates that intravenous administrations of norepinephrine and epinephrine increase IVCF, whatever the volemic conditions are. The concomitant decreases in PPV and SVV corroborate the fact that catecholamine administration recruits unstressed blood volume. In this regard, understanding a decrease in PPV and SVV values, after catecholamine administration, as an obvious indication of a restored volemia could be an outright misinterpretation.

Haemodynamic monitoring in the intensive care unit: results from a web-based Swiss survey.

Background. The aim of this survey was to describe, in a situation of growing availability of monitoring devices and parameters, the practices in haemodynamic monitoring at the bedside. Methods. We conducted a Web-based survey in Swiss adult ICUs (2009-2010). The questionnaire explored the kind of monitoring used and how the fluid management was addressed. Results. Our survey included 71% of Swiss ICUs. Echocardiography (95%), pulmonary artery catheter (PAC: 85%), and transpulmonary thermodilution (TPTD) (82%) were the most commonly used. TPTD and PAC were frequently both available, although TPTD was the preferred technique. Echocardiography was widely available (95%) but seems to be rarely performed by intensivists themselves. Guidelines for the management of fluid infusion were available in 45% of ICUs. For the prediction of fluid responsiveness, intensivists rely preferentially on dynamic indices or echocardiographic parameters, but static parameters, such as central venous pressure or pulmonary artery occlusion pressure, were still used. Conclusions. In most Swiss ICUs, multiple haemodynamic monitoring devices are available, although TPTD is most commonly used. Despite the usefulness of echocardiography and its large availability, it is not widely performed by Swiss intensivists themselves. Regarding fluid management, several parameters are used without a clear consensus for the optimal method.