Comparison of an automated respiratory systolic variation test with dynamic preload indicators to predict fluid responsiveness after major surgery.

BACKGROUND: Predicting the response of cardiac output to volume administration remains an ongoing clinical challenge. The objective of our study was to compare the ability to predict volume responsiveness of various functional measures of cardiac preload. These included pulse pressure variation (PPV), stroke volume variation (SVV), and the recently launched automated respiratory systolic variation test (RSVT) in patients after major surgery. METHODS: In this prospective study, 24 mechanically ventilated patients after major surgery were enrolled. Three consecutive volume loading steps consisting of 300 ml 6% hydroxyethylstarch 130/0.4 were performed and cardiac index (CI) was assessed by transpulmonary thermodilution. Volume responsiveness was considered as positive if CI increased by >10%. RESULTS: In total 72 volume loading steps were analysed, of which 41 showed a positive volume response. Receiver operating characteristic (ROC) curve analysis revealed an area under the curve (AUC) of 0.70 for PPV, 0.72 for SVV and 0.77 for RSVT. Areas under the curves of all variables did not differ significantly from each other (P>0.05). Suggested cut-off values were 9.9% for SVV, 10.1% for PPV, and 19.7° for RSVT as calculated by the Youden Index. CONCLUSION: In predicting fluid responsiveness the new automated RSVT appears to be as accurate as established dynamic indicators of preload PPV and SVV in patients after major surgery. The automated RSVT is clinically easy to use and may be useful in guiding fluid therapy in ventilated patients.

Comparison of values in critically ill patients for global end-diastolic volume and extravascular lung water measured by transcardiopulmonary thermodilution: A metaanalysis of the literature

Introduction: Hemodynamic parameters such as the global end-diastolic volume index (GEDVI) and extravascular lung water index (EVLWI), derived by transpulmonary thermodilution, have gained increasing interest for guiding fluid therapy in critically ill patients. The proposed normal values (680-800ml/m2 for GEDVI and 3-7ml/kg for EVLWI) are based on measurements in healthy individuals and on expert opinion, and are assumed to be suitable for all patients. We analyzed the published data for GEDVI and EVLWI, and investigated the differences between a cohort of septic patients (SEP) and patients undergoing major surgery (SURG), respectively. Methods: A PubMed literature search for GEDVI, EVLWI or transcardiopulmonary single/double indicator thermodilution was carried out, covering the period from 1990 to 2010. Intervention: Meta-regression analysis was performed to identify any differences between the surgical (SURG) and non-surgical septic groups (SEP). Results: Data from 1925 patients corresponding to 64 studies were included. On comparing both groups, mean GEDVI was significantly higher by 94ml/m2 (95%CI: [54; 134]) in SEP compared to SURG patients (788ml/m2 95%CI: [762; 816], vs. 694ml/m2, 95%CI: [678; 711], p<0.001). Mean EVLWI also differed significantly by 3.3ml/kg (95%CI: [1.4; 5.2], SURG 7.2ml/kg, 95%CI: [6.9; 7.6] vs. SEP 11.0ml/kg, 95%CI: [9.1; 13.0], p=0.001).Conclusions: The published data for GEDVI and EVLWI are heterogeneous, particularly in critically ill patients, and often exceed the proposed normal values derived from healthy individuals. In the group of septic patients, GEDVI and EVLWI were significantly higher than in the group of patients undergoing major surgery. This points to the need for defining different therapeutic targets for different patient populations (AU)

Introducción: Parámetros hemodinámicos como el índice de volumen diastólico final global (GEDVI) y el índice de agua pulmonar extravascular (EVLWI), obtenidos mediante termodilución transpulmonar, suscitan un interés creciente como guía de la terapia de fluidos en pacientes críticamente enfermos. Los valores normales propuestos (680-800ml/m2 para el GEDVI y 3-7ml/kg para el EVLWI) se basan en mediciones realizadas a individuos sanos y en la opinión de expertos, y se asume que son adecuados para todos los pacientes. Analizamos los datos publicados sobre el GEDVI y el EVLWI e investigamos las diferencias entre una cohorte de pacientes septicémicos (SEP) y pacientes sometidos a cirugía mayor (SURG) respectivamente. Métodos: Se realizó una búsqueda bibliográfica en PubMed de GEDVI, EVLWI o termodilución trasncardiopulmonar de indicador único/doble referida al periodo comprendido entre 1990 y 2010. Intervenciones: Se realizó un análisis de metarregresión para identificar las diferencias entre los grupos quirúrgico (SURG) y no quirúrgico septicémico (SEP). Resultados: Se incluyeron los datos de 1925 pacientes correspondientes a 64 estudios. Al comparar ambos grupos, el GEDVI medio resultó ser significativamente (..) (AU)

Comparison of values in critically ill patients for global end-diastolic volume and extravascular lung water measured by transcardiopulmonary thermodilution: a meta-analysis of the literature.

INTRODUCTION: Hemodynamic parameters such as the global end-diastolic volume index (GEDVI) and extravascular lung water index (EVLWI), derived by transpulmonary thermodilution, have gained increasing interest for guiding fluid therapy in critically ill patients. The proposed normal values (680-800ml/m(2) for GEDVI and 3-7ml/kg for EVLWI) are based on measurements in healthy individuals and on expert opinion, and are assumed to be suitable for all patients. We analyzed the published data for GEDVI and EVLWI, and investigated the differences between a cohort of septic patients (SEP) and patients undergoing major surgery (SURG), respectively. METHODS: A PubMed literature search for GEDVI, EVLWI or transcardiopulmonary single/double indicator thermodilution was carried out, covering the period from 1990 to 2010. INTERVENTION: Meta-regression analysis was performed to identify any differences between the surgical (SURG) and non-surgical septic groups (SEP). RESULTS: Data from 1925 patients corresponding to 64 studies were included. On comparing both groups, mean GEDVI was significantly higher by 94ml/m(2) (95%CI: [54; 134]) in SEP compared to SURG patients (788ml/m(2) 95%CI: [762; 816], vs. 694ml/m(2), 95%CI: [678; 711], p<0.001). Mean EVLWI also differed significantly by 3.3ml/kg (95%CI: [1.4; 5.2], SURG 7.2ml/kg, 95%CI: [6.9; 7.6] vs. SEP 11.0ml/kg, 95%CI: [9.1; 13.0], p=0.001). CONCLUSIONS: The published data for GEDVI and EVLWI are heterogeneous, particularly in critically ill patients, and often exceed the proposed normal values derived from healthy individuals. In the group of septic patients, GEDVI and EVLWI were significantly higher than in the group of patients undergoing major surgery. This points to the need for defining different therapeutic targets for different patient populations.

Respiratory systolic variation test in acutely impaired cardiac function for predicting volume responsiveness in pigs.

BACKGROUND: Predicting the response of cardiac output (CO) to volume administration remains difficult, in particular in patients with acutely compromised cardiac function, where, even small amounts of i.v. fluids can lead to volume overload. We compared the ability to predict volume responsiveness of different functional haemodynamic parameters, such as pulse pressure variation (PPV), stroke volume variation (SVV), the static preload parameter right atrial pressure (RAP), and global end-diastolic volume (GEDV) with the recently proposed respiratory systolic variation test (RSVT) in acutely impaired cardiac function. METHODS: In 13 mechanically ventilated pigs, cardiac function was acutely reduced by continuous application of verapamil to reach a decrease in peak change of left ventricular pressure over time (dP/dt) of 50%. After withdrawal of 20 ml kg(-1) BW blood to establish hypovolaemia, four volume loading steps of 7 ml kg(-1) BW using the shed blood and 6% hydroxyethylstarch 130/0.4 were performed. Volume responsiveness was considered as positive, if CO increased more than 10%. RESULTS: Receiver operating characteristic curve analysis revealed an area under the curve (AUC) of 0.88 for the RSVT, 0.84 for PPV, 0.82 for SVV, 0.78 for RAP, and 0.77 for GEDV. CONCLUSIONS: Functional parameters of cardiac preload, including the RSVT, allow prediction of fluid responsiveness in an experimental model of acutely impaired cardiac function.

[Hemodynamic monitoring in one-lung ventilation]. / Hämodynamisches Monitoring bei Einlungenventilation.

One-lung ventilation causes adverse effects in pulmonary gas exchange and cardiocirculatory function. These adverse effects become particularly important for patients with underlying cardiopulmonary comorbidities. Alterations in pulmonary gas exchange have been investigated in several experimental and clinical trials. However, the hemodynamic consequences of one-lung ventilation are to a great extent unknown. Furthermore, no conclusive recommendations exist as to which kind of hemodynamic monitoring should be preferred in the situation of one-lung ventilation. Many issues regarding hemodynamic monitoring in one-lung ventilation remain unacknowledged. This article will review the current literature on hemodynamic monitoring in one-lung ventilation in order to derive recommendations for the application of hemodynamic monitoring in this specific peri-operative situation.

Nanobits: customizable scanning probe tips.

We present here a proof-of-principle study of scanning probe tips defined by planar nanolithography and integrated with AFM probes using nanomanipulation. The so-called 'nanobits' are 2-4 microm long and 120-150 nm thin flakes of Si(3)N(4) or SiO(2), fabricated by electron beam lithography and standard silicon processing. Using a microgripper they were detached from an array and fixed to a standard pyramidal AFM probe or alternatively inserted into a tipless cantilever equipped with a narrow slit. The nanobit-enhanced probes were used for imaging of deep trenches, without visible deformation, wear or dislocation of the tips of the nanobit after several scans. This approach allows an unprecedented freedom in adapting the shape and size of scanning probe tips to the surface topology or to the specific application.

Rapid prototyping of nanotube-based devices using topology-optimized microgrippers.

Nanorobotic handling of carbon nanotubes (CNTs) using microgrippers is one of the most promising approaches for the rapid characterization of the CNTs and also for the assembly of prototypic nanotube-based devices. In this paper, we present pick-and-place nanomanipulation of multi-walled CNTs in a rapid and a reproducible manner. We placed CNTs on copper TEM grids for structural analysis and on AFM probes for the assembly of AFM super-tips. We used electrothermally actuated polysilicon microgrippers designed using topology optimization in the experiments. The microgrippers are able to open as well as close. Topology optimization leads to a 10-100 times improvement of the gripping force compared to conventional designs of similar size. Furthermore, we improved our nanorobotic system to offer more degrees of freedom. TEM investigation of the CNTs shows that the multi-walled tubes are coated with an amorphous carbon layer, which is locally removed at the contact points with the microgripper. The assembled AFM super-tips are used for AFM measurements of microstructures with high aspect ratios.