Preliminary experience with medical applications of rapid prototyping by selective laser sintering

Rapid prototyping techniques, originally developed for building components from computer aided designs in the motor industry, are now being applied in medicine to build models of human anatomy from high resolution multiplanar imaging data such a computed tomography (CT). The established technique of stereolithography and the more recent selective laser sintering (SLS), both build up an object layer by layer. Models have applications in surgical planning, for the design of customised implants and for training. Preliminary experience of using the SLS technique for medical applications is described, addressing questions regarding image processing, data transfer and manufacture. Pilot models, built from nylon, included two skills (a child with craniosynoslosis and an adult with hypertetorism) and a normal femur which was modelled for use in a bioengineering test of an artificial hip. The dimensions of the models were found to be in good agreement with the CT data from which they were built-for the child's skull the difference between the model and the CT data was less than 1.0 +/- 0.5 mm in each direction. Our experience showed that, with care, a combination of existing software packages may be used for data conversion. Ideally, image data of high spatial resolution should be used. The pilot models generated sufficient clinical interest for the technique to be pursued in the orthopaedic field.     

Racial, ethnic, and cultural differences in dementia caregiving: review and analysis

Expectancy theory posits that anxiety sensitivity may serve as a premorbid risk factor for the development of anxiety pathology (S. Reiss, 1991). The principal aim of the present study was to determine whether anxiety sensitivity acts as a specific vulnerability factor in the pathogenesis of anxiety pathology. A large, nonclinical sample of young adults (N = 1,401) was prospectively followed over a 5-week highly stressful period of time (i.e., military basic training). Anxiety sensitivity was found to predict the development of spontaneous panic attacks after controlling for a history of panic attacks and trait anxiety. Approximately 20% of those scoring in the upper decile on the Anxiety Sensitivity Index (R. A. Peterson & S. Reiss, 1987) experienced a panic attack during the 5-week follow-up period compared with only 6% for the remainder of the sample. Anxiety sensitivity also predicted anxiety symptomatology, functional impairment created by anxiety, and disability. These data provide strong evidence for anxiety sensitivity as a risk factor in the development of panic attacks and other anxiety symptoms.     

Anger management style and the prediction of treatment outcome among male and female chronic pain patients

Anger is a prominent emotion experienced by chronic pain patients. Anecdotes suggest that anger predicts poor outcome following multidisciplinary pain programs, but no empirical evidence documents this link. We expected that patient anger expression or suppression would predict poor outcome following a pain program and that gender differences would emerge. Pre- to posttreatment measures of lifting capacity, walking endurance, depression, pain severity and activity level were collected from 101 chronic pain patients. An 'anger expression x gender' interaction was found such that anger expression among males was correlated negatively with lifting capacity improvements. 'Anger suppression x gender' interactions emerged such that anger suppression among males was correlated negatively with improvements in depression and general activities. These effects remained significant after controlling for trait anger. Thus, how anger is managed may exert unique influence on outcomes apart from the effects of mere anger proneness, at least among male pain patients.     

Ureteral Stones Clinical Guidelines Panel summary report on the management of ureteral calculi. The American Urological Association

PURPOSE: The American Urological Association convened the Ureteral Stones Clinical Guidelines Panel to analyze the literature regarding available methods for treating ureteral calculi and to make practice policy recommendations based on the treatment outcomes data. MATERIALS AND METHODS: The panel searched the MEDLINE data base for all articles related to ureteral calculi published from 1966 to January 1996. Outcomes data were extracted from articles accepted after panel review. The data were then meta-analyzed to produce outcome estimates for alternative treatments of ureteral calculi. RESULTS: The data indicate that up to 98% of stones less than 0.5 cm. in diameter, especially in the distal ureter, will pass spontaneously. Shock wave lithotripsy is recommended as first line treatment for most patients with stones 1 cm. or less in the proximal ureter. Shock wave lithotripsy and ureteroscopy are acceptable treatment choices for stones 1 cm. or less in the distal ureter. CONCLUSIONS: Most ureteral stones will pass spontaneously. Those that do not can be removed by either shock wave lithotripsy or ureteroscopy. Traditional blind basket extraction, without fluoroscopic control and guide wires, is not recommended. Open surgery is appropriate as a salvage procedure or in certain unusual circumstances.     

Open-channel block of N-methyl-D-aspartate (NMDA) responses by memantine: therapeutic advantage against NMDA receptor-mediated neurotoxicity

Excessive activation of NMDA receptors is thought to mediate the calcium-dependent neurotoxicity associated with hypoxic-ischemic brain injury, trauma, epilepsy, and several neurodegenerative diseases. For this reason, various NMDA antagonists have been investigated for their therapeutic potential in these diseases, but heretofore none have proven to be both effective and safe. In the present study, memantine, an adamantane derivative similar to the antiviral drug amantadine, is shown to block the channels activated by NMDA receptor stimulation. From whole-cell and single-channel recording experiments, the mechanism of action of memantine is deduced to be open-channel block, similar to MK-801; however, unlike MK-801, memantine is well tolerated clinically. Compared to MK-801, memantine's safety may be related to its faster kinetics of action with rapid blocking and unblocking rates at low micromolar concentrations. Furthermore, at these levels memantine is an uncompetitive antagonist and should theoretically allow near-normal physiological NMDA activity throughout the brain even in the face of pathologically high focal concentrations of glutamate. These pharmacological properties confer upon memantine a therapeutic advantage against NMDA receptor-mediated neurotoxicity with few side effects compared with other organic NMDA open-channel blockers. Moreover, memantine is increasingly effective against escalating levels of glutamate, such as those observed during a stroke. Low micromolar concentrations of memantine, levels known to be tolerated by patients receiving the drug for the treatment of Parkinson's disease, prevent NMDA receptor-mediated neurotoxicity in cultures of rat cortical and retinal ganglion cell neurons; memantine also appears to be both safe and effective in a rat stroke model. These results suggest that memantine has considerable therapeutic potential for the myriad of clinical entities associated with NMDA receptor-mediated neurotoxicity.     

The effects of smoking on bone mass and the rates of bone loss among elderly Japanese-American men

Bone density and bone loss rates were examined among Japanese-American men categorized as current cigarette smokers, past smokers, and nonsmokers. The design included a retrospective study of smoking and bone density and a prospective study of current smoking and bone loss rates. The mean length of follow-up was 5 years; the setting was the island of Oahu. The subjects included 1303 men in the Hawaii Osteoporosis Study, 51-82 years old at their initial examination. Twenty percent were current smokers, 45% past smokers, and 35% had never smoked. Their bone density was measured at the distal and proximal radius and calcaneus using single photon absorptiometry. Compared with never smokers, current and past smokers had significantly lower bone density, especially in the predominantly cancellous calcaneus (4.8 and 4.3% lower, respectively) and partially trabecular distal radius (1.8 and 3.3% lower, respectively). The magnitude of the smoking effect was linked strongly to the duration of smoking and also to the number of cigarettes smoked. Bone loss rates subsequent to the initial measurement were greater in the current smokers than the never smokers (20.5, 27.2, and 9.7% greater at the calcaneus, distal, and proximal radius, respectively) but the differences did not achieve significance. Smokers of more than one pack per day had 32.0, 77.6, and 30.7% greater loss rates than never smokers in these same sites; the difference achieved significance at the distal radius. The results from the distal radius suggest that these smokers may increase their fracture risk 10-30% per decade of smoking. The adverse effects of smoking appeared to be greater in cancellous than cortical bone.     

Effect of pregnancy on maternal oxygen saturation values: use of reflectance pulse oximetry during pregnancy

Our objective was to evaluate the usefulness of pulse oximetry monitoring in a large population of pregnant patients. We designed our study to measure pulse oximetry saturation in a cross section of 952 obstetric inpatients and outpatients. A group of 366 patients identified as normal were compared with abnormal subgroups. A subgroup of 64 patients with saturation measurements less than 96% were further evaluated. Our results indicated that oxygen saturation values did not change appreciably during the course of pregnancy in normal patients. Hypoxemia (saturation measurement less than 96%) was associated with smoking, and hypoxemia with preterm labor occurred more frequently in patients who smoked. Obesity and magnesium sulfate use appeared to be synergistic in the presence of hypoxemia. We concluded that the routine use of pulse oximetry during pregnancy may not be justified. Smoking, obesity, and magnesium sulfate use have some effect on oximetry in pregnant patients.