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Biomedical subjects

A Versluis

Publications and source records attributed to A Versluis.

32 records · Page 2Linked to original sources

Towards understanding treatment preferences of hospital physicians.

Seventy-two physicians working in a university hospital in The Netherlands were interviewed to clarify their decision-making process when choosing drugs of preference. Each physician was questioned about the treatment choices for either one or two general case descriptions. The physicians considered only a limited set of different treatment options, on an average 1.7-5.0. Further, the physicians expressed their expectancies as regards various treatment alternatives, and the value or weight they attached to the principle aspects of a treatment. An analytical decision model was used as a reference to gain insight into the extent to which the physicians make decisions based on their own subjective expectancies and values. This model assumes that physicians follow a maximizing strategy by choosing the treatment they personally assess as optimal. It was found that a model including only biomedical expectancies and values predicted the preferred treatment correctly in no more than 53% of the cases. Sometimes, biomedical aspects were disregarded that should have been relevant according to the physicians themselves. Adding aspects of the social environment and experiences improved the prediction of the model substantially; 3 out of 4 treatment preferences could be understood by following an analytical maximizing strategy including biomedical aspects and social aspects and experiences. In the remaining cases, the physicians were not able to describe their decision in terms of this maximizing strategy, which points at the use of alternative decision strategies. One alternative decision strategy mentioned by the physicians was a 'follow-the-routine' decision rule.

Adult↗

Drug expectations and drug choices of hospital physicians.

OBJECTIVES: To assess whether differences in drug choices of hospital physicians are related to differences in the underlying decision-making process. DESIGN: A survey study was conducted addressing drug choices in six therapeutic fields with existing interprescriber variations; prescribers and non-prescribers of drugs of which the merits were not sufficiently proven (i.e. the 'target drugs') were compared. SETTING: A 1000-bed university hospital in The Netherlands. SUBJECTS: All 85 hospital physicians working in specialities involving one of the selected fields were asked to participate; 72 physicians completed the interviews. MAIN OUTCOME MEASURES: Comparisons were made regarding three elements of the decision-making process: (1) the physicians' expectations of the target drugs and frequently used alternatives, (2) the weights attached to the principal treatment aspects, and (3) the extent to which their actual choice is based on these expectations and weights. RESULTS: In three fields, i.e. anti-emetics, vasodilators, and platelet inhibitors, the prescribers of the less desirable target drugs had higher expectations of these drugs in comparison to the non-prescribers. In the other therapeutic fields, choosing target drugs was related either to attaching less importance to side-effects and costs, or to attaching less importance to reports from clinical trials. Twenty of the 46 treatment choices of the prescribers of target drugs could not be predicted from their expressed views as opposed to 5 of the 36 choices of the non-prescribers (P < 0.05). CONCLUSIONS: Choosing less desirable drugs is not always related to having too high expectations of the drug. Assigning a different importance to certain aspects of the drug and resorting to decision strategies that do not include the weighing of all pros and cons provide alternative explanations for such treatment choices.

Decision Making↗

Secretion of lipoprotein cholesterol by perfused livers from rabbits hypo- or hyperresponsive to dietary cholesterol: greater dietary cholesterol-induced secretion in hyperresponsive rabbits.

In two inbred strains of rabbits with high or low response of plasma cholesterol to dietary cholesterol, secretion of lipoprotein cholesterol by perfused livers was determined. The perfused rabbit livers secreted cholesterol into the perfusate at essentially constant rates between 30 and 120 min of perfusion. Most of the secreted cholesterol resided in VLDL. Addition of cholesterol to the diet of the donor rabbits caused a higher cholesterol:triglyceride ratio of lipoproteins secreted by the perfused liver. Such a rise was also seen in the plasma lipoproteins of cholesterol-fed rabbits. Plasma and perfusate lipoproteins differed in that the former had a higher cholesterol:triglyceride ratio. Cholesterol feeding produced a higher output of lipoprotein cholesterol by the perfused liver, the increment being greater in hyper- than in hyporesponders. Cholesterol-fed hyperresponders had higher liver cholesterol concentrations than their hyporesponsive counterparts. There was a direct relationship between the rise of liver cholesterol concentrations and the rise of hepatic secretion of lipoprotein cholesterol; this relationship was identical for hypo- and hyperresponders. We conclude that the higher cholesterolemic response to cholesterol feeding in the hyperresponders, when compared with the hyporesponders, can be explained, at least partly, by a greater cholesterol-induced hepatic secretion of lipoprotein cholesterol.

Animals↗

Impact of clinical trials on the adoption of new drugs within a university hospital.

To assess the influence that clinical trials may have on the introduction of new drugs into prescribing routines, the adoption of drugs has been studied in a university hospital in the Netherlands. A significant relation was found between the testing of semi-innovative drugs in clinical trials in the hospital and the introduction of these drugs into general use in the same hospital. No such relationship was found for innovative drugs. Employment in clinical trials only affected the frequency of adoption of semi-innovative drugs. It did not influence the quantity of their use once they had been adopted. The idea that the stimulating effect of clinical trials on the adoption of semi-innovative drugs is only due to acceleration of the adoption process was not confirmed. These findings support the idea that clinical trials can lower the barriers for adoption of semi-innovative drugs.

Clinical Trials as Topic↗

The hypercholesterolemic effect of dietary coconut fat versus corn oil in hypo- or hyperresponsive rabbits is not exerted through influencing cholesterol absorption.

In two inbred strains of rabbits with high or low response of plasma cholesterol to dietary saturated versus polyunsaturated fatty acids, the efficiency of intestinal cholesterol absorption was measured. The feeding of a cholesterol-free purified diet containing saturated fatty acids in the form of coconut fat, when compared with a diet containing corn oil as polyunsaturated fatty acids, did not influence the efficiency of cholesterol absorption in the two rabbit strains. Irrespective of the dietary fat source, the hyperresponsive rabbits absorbed cholesterol more efficiently. It is concluded that the hypercholesterolemic effect of dietary coconut fat versus corn oil is not exerted by influencing cholesterol absorption.

Animals↗

Prescribing pattern in a Dutch university hospital.

In many countries, including The Netherlands, little is known about the overall prescribing patterns within hospitals. While individual hospitals have some data available, these are not pooled on a regional or national level. The available data consist of dispensing data that are neither patient-linked nor diagnosis-linked. We report the results of a study in a Dutch university hospital which show that despite the limitations, such data can be used for a general evaluation of prescribing patterns. Using three categories of undesirable or irrational drug prescribing the dispensing data were screened. The categories were 'inferior or dubious' drugs, 'semi-innovative' drugs, and 'inappropriately used' drugs. The results show that most problems are seen with the use of new drugs. In the first instance, this involves the use of semi-innovative drugs whose adoption may be stimulated by clinical trials in the hospital concerned. Secondly, innovative drugs seem to be used on too large a scale, i.e., for indications for which their use is not warranted. Based on these findings, a follow-up study has been initiated to study some of these suboptimal drug choices in detail.

Drug Prescriptions↗

Sterol balance and cholesterol absorption in inbred strains of rabbits hypo- or hyperresponsive to dietary cholesterol.

In 2 inbred strains of rabbits with high or low response of plasma cholesterol to dietary cholesterol, excretion of steroids in the feces and efficiency of cholesterol absorption were determined. Rates of whole-body cholesterol synthesis, measured as fecal excretion of bile acids and neutral steroids minus cholesterol intake, were similar in hypo- and hyperresponders fed a low-cholesterol (8 mumol/100 g) diet. Transfer of the rabbits to a high-cholesterol (182 mumol/100 g) diet caused an increase in fecal bile acid excretion in hypo- but not in hyperresponders. Dietary cholesterol did not affect neutral steroid excretion in either rabbit strain. Hyperresponders tended to accumulate more cholesterol in their body than did hyporesponders. After the rabbits were switched back from the high- to the low-cholesterol diet, rates of whole-body cholesterol synthesis were significantly higher in the hypo- than in the hyperresponders. With the use of the simultaneous oral administration of [3H]cholesterol and beta-[14C]sitosterol, hyperresponders were found to absorb significantly higher percentages of cholesterol than hyporesponders. It is concluded that the differences in stimulation of bile acid excretion after cholesterol feeding and the efficiency of cholesterol absorption are important determinants of the phenomenon of hypo- and hyperresponsiveness in the 2 inbred rabbit strains.

Animals↗

Prolapsus vaginae in the IIIVO/JU rabbit.

In a specified pathogen free (SPF) breeding colony of IIIVO/JU rabbits 8 cases of prolapsus vaginae occurred in 5 years. Clinically the animals were in shock. Haematocrits ranged from 9 to 15%. The prolapses started from the submucosal layer of the proximal part of the vestibulum vaginae. The prolapsed tissue consisted of over-expanded blood-sinuses. Between the sinuses signs of an inflammatory reaction were present. All 8 animals were in a period of increasing sexual activity when the prolapse developed. The 8 rabbits were closely related, indicating a possible hereditary defect.

Animals↗

Pharmacokinetics of the oral narcotic analgesic bezitramide and preliminary observations on its effect on experimentally induced pain.

The oral absorption of bezitramide 5 mg was studied in 7 human volunteers, using a specific radioimmuno-assay which measured both bezitramide and its active metabolite R-4618. A lag time of 0.5-1.0 h and a Cmax of 5.4 ng/ml plasma were found, the latter occurring 2.5-3.5 h after administration. The apparent elimination half-life varied from 11 to 24 h. Less than 0.3% of the dose was excreted unchanged in the urine. High concentrations in the faeces of some individuals indicate incomplete absorption and/or biliary secretion. The analgesic effect, using a standardized superficial electrical stimulation method, reached its maximum between 2.5 and 3.5 h after dosing, in accordance with the absorption phase. The duration of the effect was highly variable. Experiments in rats (n = 6, 3H-bezitramide 2.5 micrograms), demonstrated extensive biliary excretion (up to 70% of total radioactivity) and less than 3% of the label was removed by urinary excretion.

Adult↗

Clinical evaluation of radio-labelled bleomycin for tumor detection.

Investigations with bleomycin labelled with radionuclides other than 57Co in patients with cancer and in tumor-bearing animals are described. In patients 57Co-bleo appears to be a better tumor-seeking radiopharmaceutical than 111In-bleo, 99mTc-bleo or 197Hg-bleo. This can be explained by a higher stability in vivo and a better tumor-seeking property of 57Co-bleo and less disturbing activity in the cardiac pool and in bone and other normal tissues when assessing the scintigram. Results with 111In-bleo labelled in acidic solution are not essentially different from those with 111In-bleo labelled in neutral solution. Results of 197Hg-bleo are almost identical with those of 197HgCl2 regarding the tumor-seeking effect as well as the distribution in normal tissues and organs. Probably the complex of 197Hg to bleomycin is not stable in vivo. The superiority of 57Co-bleo over 99mTc-bleo, 197Hg-bleo and also over 67Cu-bleo is confirmed by experiments on tumor bearing animals. We may conclude that the indication for use of bleomycin as a tumor-seeking pharmaceutical labelled with 111In, 99mTc, 197Hg or 67Cu seems to be very limited.

Animals↗

Labelling of bleomycin with cobalt-57, indium-111, technetium-99m, mercury-197, lead-203, and copper-67.

The radiochemical purity of the cobalt-57 complex of bleomycin could be enhanced by adjusting the pH of the final product to a value between 5 and 6. This radiopharmaceutical appeared to have better tumor visualizing properties compared to the not neutralized preparation. The clinical use of the cobalt-57 bleomycin complex is however limited by the long physical half-life of the label, causing a risk of radioactive contamination. It appeared to be possible to label bleomycin with radioactive cations (111In3+, 99mTc4+, 197Hg2+ and 67Cu2+) having suitable gamma ray energies and short half-lifes. These bleomycin complexes showed a high radio-chemical purity judged by their behaviour on thin layer chromatography, paper chromatography, and electrophoresis, but their application as tumor visualizing radiopharmaceutical turned out to be disappointing compared with cobalt-57 bleomycin.

Bleomycin↗

Numerical analysis of a dental implant system preloaded with a washer.

Gold screw loosening is a problem that frequently affects dental implants. The application of a preload has been the main means of preventing loosening. However, this measure has not been able to eliminate its occurrence. In this study the effect of a washer in a Brånemark-type implant on the loosening conditions of the retaining screw was investigated using a finite element simulation. The simulation indicated that a washer may significantly increase the tolerance of a screw against loosening. This is accomplished by increasing the tolerance of the implant against deformation. The addition of a customized washer to a dental implant system may offer a very simple and inexpensive solution for the persistent problem of screw loosening.

Dental Abutments↗