O. Ruthmann

Risk factors and complications following percutaneous endoscopic gastrostomy: a case series of 1041 patients.

BACKGROUND Most studies exclude patients with severe coagulation disorders or those taking anticoagulants when evaluating the outcomes of percutaneous endoscopic gastrostomy (PEG). OBJECTIVE To investigate complications and risk factors of PEG in a large clinical series including patients undergoing antiplatelet and anticoagulant therapy. METHODS During a six-year period, 1057 patients referred for PEG placement were prospectively audited for clinical outcome. Exclusion criteria and follow-up care were defined. Complications were defined as minor or severe. Uni- and multivariate analyses were used to evaluate 14 risk factors. No standardized antibiotic prophylaxis was given. RESULTS A total of 1041 patients (66% male, 34% female) with the following conditions underwent PEG: neurogenic dysphagia (n=450), cancer (n=385) and others (n=206). No anticoagulants were administered to 351 patients, thrombosis prophylaxis was given to 348 while full therapeutic anticoagulation was received by 313. No increased bleeding risk was associated with patients who had above-normal international normalized ratio values (OR 0.79 [95% CI 0.08 to 7.64]; P=1.00). The total infection rate was 20.5% in patients with malignant disease, and 5.5% in those with nonmalignant disease. Severe complications occurred in 19 patients (bleeding 0.5%, peritonitis 1.3%). Cirrhosis (OR 2.91 [95% CI 1.31 to 6.54]; P=0.008), cancer (OR 2.34 [95% CI 1.33 to 4.12]; P=0.003) and radiation therapy (OR 2.34 [95% CI 1.35 to 4.05]; P=0.002) were significant predictors of post-PEG infection. The 30-day mortality rate was 5.8%. There were no procedure-related deaths. CONCLUSIONS Cancer, cirrhosis and radiation therapy were predictors of infection. Post-PEG bleeding and other complications were rare events. Collectively, the data suggested that patients taking concurrent anticoagulants had no elevated risk of post-PEG bleeding.

The first teleautomatic low-voltage prosthesis with multiple therapeutic applications: a new version of the German artificial sphincter system.

To date, there are no artificial sphincter prostheses for urinary or fecal incontinence that may be implemented elsewhere instead, for example, in the upper gastrointestinal tract. Conventional systems are conceptually similar but are constructed specifically for distinct applications and are manual in operation. The German Artificial Sphincter System (GASS) II is the evolution of a highly integrative, modular, telemetric sphincter prosthesis with more than one application. Redesigning and integrating multilayer actuators into the pump allows us to reduce the input voltage to -10 to +20 V (V(PP) = 30 V). This provides for a flow rate of 2.23 mL/min and a counterpressure stability of 260 mbar. Furthermore, multiple applications have become feasible due to our standardized connection system, therapy-specific compression units, and application-specific software. These innovations allow us to integrate not only severe fecal and urinary incontinence, erectile dysfunction, and therapy-resistant reflux disease, but also morbid adiposity into the gamut of therapeutic GASS applications.

Percutaneous endoscopic gastrostomy. Complications with and without anticoagulation

BACKGROUND Percutaneous endoscopic gastrostomy (PEG) has been classified to date as a high-risk procedure (ASGE guidelines). Coagulopathies, thrombocyte aggregation inhibitors (Aspirin, clopidogrel etc.) and phenprocoumone or warfarin are considered to be contraindications. The study examined for the first time the risk factors in patients with and without concurrent anticoagulation. METHODS Between 2001 and 2007 PEGs were placed in 450 patients with neurological diseases at the University Hospital for General and Visceral Surgery in Freiburg and studied prospectively during hospitalization. The patients were divided into 3 groups: group 1 controls (n=50, no anticoagulation), group 2 low-molecular-weight heparin (LMWH) prophylaxis (n=152) and group 3 therapeutic anticoagulation (unfractionated heparin, phenprocoumone, therapeutic LMWH, aspirin, clopidorel and combinations, n=248). Univariate analyses were performed to determine risk factors for the occurrence of infection, bleeding and peritonitis. The p-values (p), odds ratios (OR) and 95% confidence intervals (CI) are given. RESULTS The average hospitalization time was 27.4 days (range 1-268 days) and hospital mortality was 6%. There were no cases of death due to the PEG. Complications included peristomal infections (n=30, 6.6%) and peritonitis (n=6, 1.3%). Post-PEG bleeding did not occur either with or without anticoagulation. The investigated risk factors showed no statistically significant values with respect to prognosis for these complications. Multivariate testing could not be carried out due to the low number of complications. CONCLUSION Complications of PEG placement with the method used here are rare. An increased risk of bleeding during therapeutic anticoagulation was not observed. In our opinion the present data indicate that PEG placement can be carried out in selected patients with increased risk of thromboembolism without discontinuation of anticoagulation.

Perkutane endoskopische Gastrostomie

BACKGROUND Percutaneous endoscopic gastrostomy (PEG) has been classified to date as a high-risk procedure (ASGE guidelines). Coagulopathies, thrombocyte aggregation inhibitors (Aspirin, clopidogrel etc.) and phenprocoumone or warfarin are considered to be contraindications. The study examined for the first time the risk factors in patients with and without concurrent anticoagulation. METHODS Between 2001 and 2007 PEGs were placed in 450 patients with neurological diseases at the University Hospital for General and Visceral Surgery in Freiburg and studied prospectively during hospitalization. The patients were divided into 3 groups: group 1 controls (n=50, no anticoagulation), group 2 low-molecular-weight heparin (LMWH) prophylaxis (n=152) and group 3 therapeutic anticoagulation (unfractionated heparin, phenprocoumone, therapeutic LMWH, aspirin, clopidorel and combinations, n=248). Univariate analyses were performed to determine risk factors for the occurrence of infection, bleeding and peritonitis. The p-values (p), odds ratios (OR) and 95% confidence intervals (CI) are given. RESULTS The average hospitalization time was 27.4 days (range 1-268 days) and hospital mortality was 6%. There were no cases of death due to the PEG. Complications included peristomal infections (n=30, 6.6%) and peritonitis (n=6, 1.3%). Post-PEG bleeding did not occur either with or without anticoagulation. The investigated risk factors showed no statistically significant values with respect to prognosis for these complications. Multivariate testing could not be carried out due to the low number of complications. CONCLUSION Complications of PEG placement with the method used here are rare. An increased risk of bleeding during therapeutic anticoagulation was not observed. In our opinion the present data indicate that PEG placement can be carried out in selected patients with increased risk of thromboembolism without discontinuation of anticoagulation.

Design and simulation of advanced charge recovery piezoactuator drivers

The German Artificial Sphincter System project aims at the development of an implantable sphincter prosthesis driven by a piezoelectrically actuated micropump. The system has been designed to be fully implantable, i.e. the power supply is provided by a rechargeable lithium polymer battery. In order to provide sufficient battery duration and to limit battery dimensions, special effort has to be made to minimize power consumption of the whole system and, in particular, of the piezoactuator driver circuitry. Inductive charge recovery can be used to recover part of the charge stored within the actuator. We are going to present a simplified inductor-based circuit capable of voltage inversion across the actuator without the need of an additional negative voltage source. The dimension of the inductors required for such a concept is nevertheless significant. We therefore present a novel alternative concept, called direct switching, where the equivalent capacitance of the actuator is charged directly by a step-up converter and discharged by a step-down converter. We achieved superior performance compared to a simple inductor-based driver with the advantage of using small-size chip inductors. As a term of comparison, the performance of the aforementioned drivers is compared to a conventional driver that does not implement any charge recovery technique. With our design we have been able to achieve more than 50% reduction in power consumption compared to the simplest conventional driver. The new direct switching driver performs 15% better than an inductor-based driver. A novel, whole-system SPICE simulation is presented, where both the driving circuit and the piezoactuator are modeled making use of advanced nonlinear models. Such a simulation is a precious tool to design and optimize piezoactuator drivers.

An Efficient Low-voltage Micropump For An Implantable Sphincter System

We present our current developments in the GASS project. GASS is an implantable sphincter prosthesis driven by a micropump. The aim of the previous stages of this project was to demonstrate the feasibility of the approach. Currently we focus on the safety and efficiency of the micropump. A low-voltage multilayer actuator was developed to reduce the driving voltage of the micropump from approximately 300 Vpp to 30 Vpp. A miniaturized driving circuit with charge recovery is currently developed. The overall efficiency of the micropump system is in the range of 2% depending on the hydraulic conditions. Different approaches for the energy management of the prosthesis and the resulting size, weight and lifetime are presented.

Perkutane endoskopische Gastrostomie@@@Percutaneous endoscopic gastrostomy: Komplikationen mit und ohne Antikoagulation@@@Complications with and without anticoagulation

BACKGROUND Percutaneous endoscopic gastrostomy (PEG) has been classified to date as a high-risk procedure (ASGE guidelines). Coagulopathies, thrombocyte aggregation inhibitors (Aspirin, clopidogrel etc.) and phenprocoumone or warfarin are considered to be contraindications. The study examined for the first time the risk factors in patients with and without concurrent anticoagulation. METHODS Between 2001 and 2007 PEGs were placed in 450 patients with neurological diseases at the University Hospital for General and Visceral Surgery in Freiburg and studied prospectively during hospitalization. The patients were divided into 3 groups: group 1 controls (n=50, no anticoagulation), group 2 low-molecular-weight heparin (LMWH) prophylaxis (n=152) and group 3 therapeutic anticoagulation (unfractionated heparin, phenprocoumone, therapeutic LMWH, aspirin, clopidorel and combinations, n=248). Univariate analyses were performed to determine risk factors for the occurrence of infection, bleeding and peritonitis. The p-values (p), odds ratios (OR) and 95% confidence intervals (CI) are given. RESULTS The average hospitalization time was 27.4 days (range 1-268 days) and hospital mortality was 6%. There were no cases of death due to the PEG. Complications included peristomal infections (n=30, 6.6%) and peritonitis (n=6, 1.3%). Post-PEG bleeding did not occur either with or without anticoagulation. The investigated risk factors showed no statistically significant values with respect to prognosis for these complications. Multivariate testing could not be carried out due to the low number of complications. CONCLUSION Complications of PEG placement with the method used here are rare. An increased risk of bleeding during therapeutic anticoagulation was not observed. In our opinion the present data indicate that PEG placement can be carried out in selected patients with increased risk of thromboembolism without discontinuation of anticoagulation.

A high performance bidirectional micropump utilizing advanced low voltage piezo multilayer actuator technology for a novel artificial sphincter system

We present our latest developments for a novel artificial sphincter system. This system had been continuously developed over several years within the GASS project. Main part of the system is a high performance bidirectional silicon micropump driven by piezo actuators. The driving voltage of the newly developed system had been reduced from 300 V to 40 V peak-to-peak by using advanced multilayer piezo actuators. A peak flowrate of 4.36 ml/min had been measured at a driving frequency of 35 Hz. We have measured a maximum backpressure capability of 505 mbar with a square wave driving signal at Vpp=45 V. The whole system is designed to work as a self-sustaining battery driven, remote controlled system.

Low Power Electronics for Square-Wave Piezoactuator Driving

The German Artificial Sphincter System (GASS) project aims at the development of an implantable sphincter prosthesis driven by a micropump. During the last few years the feasibility of the concept has been proven. At present our team’s effort is focused on the compliance to safety regulations and on a very low power consumption of the system as a whole. Therefore a low-voltage multilayer piezoactuator has been developed to reduce the driving voltage of the micropump from approximately 300 Vpp to 40 Vpp. Doing so, the driving voltage is within the limits set by the regulations for active implants. The operation of the micropump at lower voltages, achieved using multilayer piezoactuators, has already resulted in a much better power efficiency. Nevertheless, in order to further reduce power consumption, we have also developed an innovative driving technique that we are going to describe and compare to other driving systems. A direct switching circuit has been developed where the buffer capacitor of the step-up converter has been replaced by the equivalent capacitance of the actuator itself. This avoids the switching of the buffer capacitor to the actuator, which would result in a very low efficiency. Usually, a piezoactuator needs a bipolar voltage drive to achieve maximum displacement. In our concept, the voltage inversion across the actuator is done using an h-bridge circuit, allowing the employment of one step-up converter only. The charge stored in the actuator is then partially recovered by means of a step-down converter which stores back the energy at the battery voltage level. The power consumption measurements of our concept are compared to a conventional driving output stage and also with inductive charge recovery circuits. In particular, the main advantage, compared to the latter systems, consists in the small inductors needed for the power converter. Other charge recovery techniques require very big inductors in order to have a significant power reduction with the capacitive loads we use in our application. With our design we will be able to achieve approximately 55% reduction in power consumption compared to the simplest conventional driver and 15% reduction compared to a charge recovery driver.Copyright