Abstract 340: Recombinant Soluble Apyrase Inhibits Vascular Smooth Muscle Cell Migration

Background: Purinergic receptor activation by extracellular nucleotides is involved in thrombosis and neointimal hyperplasia that accompany atherosclerosis and postangioplasty restenosis. Human apyrases [ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDases)] are membrane bound enzymes that hydrolyze extracellular nucleotides, thereby inhibiting purinergic receptor activation. CD39, the first identified human apyrase, is constitutively expressed on endothelial cell (EC) and vascular smooth muscle cell (VSMC) surfaces. APT102, a recombinant soluble form of CD39L3, has been shown to reduce platelet activation through its ADPase activity, but its effects on VSMC and EC function are yet to be established. We tested the hypothesis that APT102 will inhibit migration of VSMCs and ECs.

Methods: We studied cell migration using a modified Boyden chamber assay in which 5x10 4 cells suspended in 0.2% FBS/DMEMF12 were added to the upper chamber of transwells separated from the lower chamber medium by a microporous membrane through which VSMCs and ECs can migrate. APT102 (100 nM) or vehicle control was added to the upper chamber; lower chamber contained 2.5% FBS/DMEMF12 and either ATP (10 μM) or vehicle control. Transwells were incubated at 37 0 C for 6 h, after which cells that migrated through pores and adhered to the lower chamber side of the membrane were fixed, stained and counted.

Results: ATP (10μM) significantly enhanced migration of both VSMCs and ECs. APT102 significantly inhibited VSMC migration and completely abrogated the pro-migratory effect of ATP. In contrast, APT102 had no inhibitory effect on EC migration, either spontaneous or ATP-enhanced.

Conclusion: APT102 inhibits VSMC but not EC migration. These results suggest that pharmacological targeting of extracellular nucleotides may provide a safe and effective therapeutic strategy to inhibit neointimal hyperplasia and restenosis after angioplasty, without delaying endothelial cell recovery, which is a significant limitation of drug-eluting stents. Further studies are needed to clarify the mechanism(s) underlying the differential effect of extracellular nucleotide degradation by APT102 on VSMC and EC migration.

Testing internal consistency and construct validity during evaluation of performance in a patient simulator

The primary goal of this study was to test the items in a rating system developed to evaluate anesthesiologists' performance in a simulated patient environment. A secondary goal was to determine whether the test scores could discriminate between resident and staff anesthesiologists. Two 5-item clinical scenarios included patient evaluation and induction and maintenance of anesthesia. Rating scales were no response to the problem (score = 0), compensating intervention (score = 1), and corrective treatment (score = 2). Internal consistency was estimated using Cronbach's coefficient alpha. Scores between groups were compared using the Cochran-Mantel-Haenszel test. Subjects consisted of 8 anesthesiology residents and 17 university clinical faculty. The Cronbach's coefficient alpha was 0.27 for Scenario A and 0.28 for Scenario B. Two items in each scenario markedly decreased internal consistency. When these four items were eliminated, Cronbach's coefficient alpha for the remaining six items was 0.66. Faculty anesthesiologists scored higher than residents on all six items (P < 0.001). A patient simulator-based evaluation process with acceptable reliability was developed.

IMPLICATIONS

The reliability of anesthesia clinical performance in a patient simulation environment was assessed in this study. Of 10 items, 4 were poor in the evaluation process. When these items were removed, the reliability of the instrument improved to a level consistent with other studies. Because faculty scored higher than resident anesthesiologists, the instrument also showed discriminant validity.

Development of an example flow test object and comparison of five of these test objects, constructed in various laboratories

Doppler test objects are used to characterise Doppler systems, both stand-alone systems and the Doppler part of so-called duplex scanners. The aim of the project partially presented here is the development and validation of an example of a Doppler test object fulfilling the requirements of the IEC 1685. The project has been carried out by nine partners of five European countries and has been funded by the European Commission. The flow Doppler test object is composed of: tissue mimicking material (TMM), blood mimicking fluid (BMF), tube (embedded in the TMM and carrying the BMF), tank flow system, including a pump and a flow meter. In the normative part of the IEC 1685, requirements are given for the values of acoustical parameters of TMM and BMF such as sound velocity, attenuation and backscattering. For BMF, requirements are given also for values of density and viscosity. In an informative (but not compulsory) annex, a description is given of a flow test object meeting these requirements as an example. 'example test object' developed during the project is composed of TMM based on agar and including SiC- and Al2O3-powders, BMF based on nylon particles suspended in water and glycerine, and a tube of c-flex, a silicon copolymer. Two tube sizes are used: 4.0 mm ID and 8.0 mm ID. During the project, very precise recipes have been developed for the composition and preparation of both TMM and BMF. Based on these recipes and a description of the construction in a design five flow test objects have been constructed in the laboratories of five participants. The test objects have been compared by measurements of the physical parameters and by Doppler measurements of the five test objects with the Doppler system. The measurements have been carried out by five observers. Inter-test object and inter-observer variabilities are determined, yielding information about usefulness of the parameters.

Testing the raters: inter-rater reliability of standardized anaesthesia simulator performance

PURPOSE

Assessment of physician performance has been a subjective process. An anaesthesia simulator could be used for a more structured and standardized evaluation but its reliability for this purpose is not known. We sought to determine if observers witnessing the same event in an anaesthesia simulator would agree on their rating of anaesthetist performance.

METHODS

The study had the approval of the research ethics board. Two one-hour clinical scenarios were developed, each containing five anaesthetic problems. For each problem, a rating scale defined the appropriate score (no response to the situation: score = 0; compensating intervention defined as physiological correction: score = 1; corrective treatment: defined as definitive therapy score = 2). Video tape recordings, for assessment of inter-rater reliability, were generated through role-playing with recording of the two scenarios three times each resulting in a total of 30 events to be evaluated. Two clinical anaesthetists, uninvolved in the development of the study and the clinical scenarios, reviewed and scored each of the 30 problems independently. The scores produced by the two observers were compared using the kappa statistic of agreement.

RESULTS

The raters were in complete agreement on 29 of the 30 items. There was excellent inter-rater reliability (= 0.96, P < 0.001).

CONCLUSIONS

The use of videotapes allowed the scenarios to be scored by reproducing the same event for each observer. There was excellent inter-rater agreement within the confines of the study. Rating of video recordings of anaesthetist performance in a simulation setting can be used for scoring of performance. The validity of the scenarios and the scoring system for assessing clinician performance have yet to be determined.

Optimal electrical stimulus for prevention of deep vein thrombosis

The most effective electrical stimulus to the calf muscles which prevents stasis in the soleal veins during operation was determined. This was subsequently used in a clinical trial and was shown to produce a 92% relative reduction in the incidence of deep vein thrombosis as determined by the (125)I-fibrinogen test.

Venous stasis and deep-vein thrombosis

A venographic technique for studying stasis in the deep veins of the legs of conscious patients is described. A second technique involving the clearance of radioactive material from the veins has been developed for use during operation. The results of the two methods correlate closely.

There is considerable stasis of the blood, particularly in the soleal veins, in conscious patients with the legs horizontal, and it is prolonged considerably during surgery. Using these new techniques the effectiveness of various methods said to prevent stasis has been assessed.