[Assessment of the benefit of medical devices in surgical practice. Problems and possible solutions]. / Nutzenbewertung von Medizinprodukten in der chirurgischen Praxis. Probleme und Lösungsmöglichkeiten.

The market approval of medical devices in Germany does not yet require a benefit assessment. Thus, there is a lack of high quality studies that clearly prove the benefit of medical innovations. In the past, the Federal Joint Committee in Germany (G-BA) did not have the opportunity to adequately address this issue of lacking evidence. A law for the improvement of the care structure in the statutory health insurance offers the possibility for the G-BA to obtain evidence for the benefit of medical practice. With an integrated regulation for testing of medical devices the manufacturers have the option to apply for an assessment of new and established treatment methods and to provide scientific evidence for the benefit of medical devices as a requirement for inclusion in the catalogue of services of the statutory health insurance. However, this expanded scope of action is also a challenge for clinicians. The already existing problem of integrating multicenter clinical trials in the surgical routine will remain. The Surgical Study Network Germany (CHIR-Net) offers an ideal way to cope with the increased requirements on studies in the field of medical devices through established partnerships with methodological institutions and practitioners in clinical settings.

Access technique and its problems in parenteral nutrition - Guidelines on Parenteral Nutrition, Chapter 9.

Catheter type, access technique, and the catheter position should be selected considering to the anticipated duration of PN aiming at the lowest complication risks (infectious and non-infectious). Long-term (>7-10 days) parenteral nutrition (PN) requires central venous access whereas for PN <3 weeks percutaneously inserted catheters and for PN >3 weeks subcutaneous tunnelled catheters or port systems are appropriate. CVC (central venous catheter) should be flushed with isotonic NaCl solution before and after PN application and during CVC occlusions. Strict indications are required for central venous access placement and the catheter should be removed as soon as possible if not required any more. Blood samples should not to be taken from the CVC. If catheter infection is suspected, peripheral blood-culture samples and culture samples from each catheter lumen should be taken simultaneously. Removal of the CVC should be carried out immediately if there are pronounced signs of local infection at the insertion site and/or clinical suspicion of catheter-induced sepsis. In case PN is indicated for a short period (max. 7-10 days), a peripheral venous access can be used if no hyperosmolar solutions (>800 mosm/L) or solutions with a high titration acidity or alkalinity are used. A peripheral venous catheter (PVC) can remain in situ for as long as it is clinically required unless there are signs of inflammation at the insertion site.

[Detection of air embolism by a re-usable Doppler probe integrated in a central venous line--application in-vivo]. / Wiederverwendbare, in einen Zentralvenenkatheter integrierbare Dopplersonde zur Detektion von Luftembolien Anwendung in-vivo.

PROBLEM: Air embolism frequently occurs under neurosurgical operations performed in the sitting position. Recently we reported the idea of inserting a re-usable doppler probe into a blind-ending lumen of a central venous catheter (Schregel-Volk-Catheter, SVC). In vitro testing in a circulation model showed a high sensitivity: air bubbles as small as 0.5 microliter were reliably detected at a distance up to 4 cm from the tip of the SVC. METHOD: After approval by the local ethics committee pigs were anaesthetised and a cardiopulmonary bypass was connected. During the bypass period a 12 F SVC (Medex Medical, Germany) with one blind-ending lumen was positioned into the proximal vena cava cranialis or vena cava caudalis. An 8 MHz doppler probe (MTB Basler, Suisse) was introduced into the SVC and connected with the doppler device Multi-Dop T (DWL, Germany). Well defined air bubbles (3-6 microliter) were generated by a bubble generator and injected into the right femoral vein or the left vena jugularis interna. RESULTS: All bubbles were reliably detected by the re-usable doppler probe. Embolic events can be documented, counted and quantified by the Multi-Dop T. CONCLUSION: Using SVC's with a blind-ending lumen could improve and simplify the detection of air embolism. We see several advantages (e.g. sensitivity, costs) compared with established methods (precordial doppler, TEE) for detection of air embolism.

[Detection of air embolism by a re-usable doppler probe integrated in a central venous line]. / Wiederverwendbare, in einen Zentralvenenkatheter integrierbare Dopplersonde zur Detektion von Luftembolien.

PROBLEM: Air embolisms frequently occur during neurosurgical operations. For detection of air embolisms, a re-usable doppler probe, integrated in a central venous line, is described. In an in-vitro test series the measuring sector as well as the function of a 8 MHz doppler probe are presented. METHOD: The 8 MHz doppler probe is a 1.1 mm diameter cable, into the distal end of which a cylindrical doppler crystal from lead-circonate-titanate (PZT5) of 2 x 1.7 mm is integrated and connected with a doppler unit. The detection of micro bubbles with a volume of 0.4-5 microliters was effected in still liquid for simple measuring of the spatial characteristics of the probe as well as in flowing liquid for simulation of a blood circulation system. RESULTS: The doppler probe detected qualitatively and reproducibly all gas bubbles offered up to 4 cm around the tip of the probe. CONCLUSION: A reliable detection of micro-bubbles in this test model is possible by means of a 8 Mhz doppler probe. Further animal and clinical studies are planned.

[Central venous cannulation - always with ultrasound support?]. / Zentralvenöse Punktion - nur noch mit Ultraschall?

Central Venous Cannulation - Always with Ultrasound Support?.Ultrasound guided puncture (UGP) improves success and complication rates of central venous cannulation. By some authors UGP with imaging devices are strongly recommended for all cannulations of subclavian or internal jugular veins. In order to review the current literature a computer based abstract search in Medline was performed for the period from January 1972 to May 2000 limited by the key words "catheterization, central venous catheter, internal jugular vein, subclavian vein, axillary vein, femoral vein, ultrasound, ultrasonography, Site-Rite und Smart Needle". UGP of the internal jugular vein was recommended in 29 prospective randomized studies, 21 prospective and three retrospective studies as well as in several clinical reports. UGP of the subclavian vein was supported by only 4 studies, whereas two studies did not show any improvement of puncture results with UGP. Due to the visualisation of the vessel and the cannula imaging techniques represent the "gold standard". However, with conventional Doppler devices nearly the same success rates can be obtained. It does not seem to be justified to perform every central venous cannulation with Doppler or ultrasound support. Each anaesthetist and intensive care physician should be able to perform central venous cannulation without a Doppler or ultrasound device. However, in cases of abnormal anatomy UGP can be helpful to prevent complications. Especially children, patients with coagulation disorders and physicians with limited experience in central venous cannulation can benefit from UGP.