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Biomedical subjects

D C Smith

Publications and source records attributed to D C Smith.

At least 505 records · Page 28Linked to original sources
PubMedDate not supplied

Threaded versus porous-surfaced designs for implant stabilization in bone-endodontic implant model.

An endodontic implant model system was used to compare the effect of implant design on stabilization in bone. Specifically a porous-surfaced design was compared to conventional threaded and smooth-tapered endodontic implant designs. All implants were placed in immediate function thereby assessing the effect of early limited movement on the fixation achieved. A total of eighty-three endodontic implants were inserted in the mandibles of six adult mongrel dogs. Animals were sacrificed immediately after implantation and after 3, 6, and 12 months. Implants were evaluated by clinical and radiographic examination and after animal sacrifice by pull-out tests of the implant from the tissues, SEM examination of the pulled-out implants and, finally, histology. The pull-out test results indicated increasing shear strength with implantation time for the porous-surfaced implants in contrast to the gradual loss of fixation for the threaded implants and the continuous low shear strength for the smooth implants. Histological studies and SEM examination indicated the reason for these changes. Smooth implants became encapsulated by fibrous connective tissue from early post-implantation time periods. Threaded implants, although initially mechanically interlocked with bone, developed a fibrous connective tissue capsule that gradually thickened with time until, by 6 months, little mechanical interlock of bone and implant was present. It was assumed that this fibrous capsule thickening was caused by implant movement. The porous-surfaced implants, however, became stabilized by bone ingrowth and showed more extensive bone formation within the surface pores with time. It is concluded that for implants that are made functional immediately after implantation, as in this study, porous-surfaced implants can become strongly fixed by bone ingrowth, in contrast to conventional threaded or smooth-surfaced designs, thus presenting a more favourable long term prognosis.

Alloys↗
PubMedDate not supplied

Angiographic demonstration of bleeding in a unusually located Meckel's diverticulum simulating colonic bleeding.

A case is reported in which bleeding from a Meckel's diverticulum was mistakenly localized to the hepatic flexure of the colon on superior mesenteric angiography. An unusually long and mobile mesentery, allowing the bleeding Meckel's diverticulum to be positioned high in the right upper quadrant, led to this misdiagnosis. The case illustrates several fundamental principles about the technique and interpretation of mesenteric angiograms.

Adult↗
PubMedDate not supplied

Percutaneous transluminal angioplasty of tibial arteries for limb salvage.

Percutaneous transluminal balloon angioplasty (PTA) was performed in 17 tibial arteries with an average cross-sectional area stenosis of 92% (range 75-99%) in 13 patients (14 limbs) for limb salvage. In 4 of 14 lower extremities, PTA of femoropopliteal arteries was also performed. Technical success with 50% or less residual stenosis was achieved in all 17 tibial vessels. At approximately 2 months after PTA, clinical improvement had occurred in 10 of 14 limbs; no patient was made worse. Most recent follow-up (mean 19 months, range 8-34 months) revealed continued satisfactory clinical success with no further vascular intervention in 9 of these 10 limbs (one patient died). Short segmental stenoses, residual stenoses less than 40% following PTA, and absence of diabetes or gangrene appear to be predictors of favorable clinical outcomes. Our results suggest that PTA of focal tibial stenosis is an effective and safe treatment modality in properly selected patients and that wider use of PTA may be justified.

Aged↗
PubMedDate not supplied

Balloon occlusion versus wedged hepatic venography using carbon dioxide for portal vein opacification during TIPS.

Balloon occlusion hepatic venography using carbon dioxide (CO2) is proposed as a safer yet simpler alternative to wedged catheter techniques that have caused hepatic lacerations during the transjugular intrahepatic portosystemic shunt (TIPS) procedure. The image quality of CO2 wedged catheter and balloon occlusion venograms was comparable in our small series, with no venographic-related complications occurring in the balloon occlusion group.

Adult↗
PubMedDate not supplied

Atlanto-occipital dislocation.

Reported is the case of a 29-year-old woman who sustained an atlanto-occipital dislocation (AOD). This patient survived the initial resuscitation to expire some 72 hours later. Survival of patients with AOD is being reported with increasing frequency and with good neurologic recovery in many cases. Emergency physicians should be aware of this injury and the methods of initial evaluation and stabilization in order to maximize the potential for patients with these serious injuries. Radiographic features of AOD are outlined and the potential hazards of longitudinal traction are emphasized.

Adult↗
PubMedDate not supplied

Pulmonary embolism presenting as an acute surgical abdomen.

Pulmonary embolism remains a serious cause of morbidity and mortality. Diagnosis based on clinical manifestations remains difficult. Prior reviews have rarely noted the potential for patients to present with abdominal complaints. Presented here is the case of a 28-yr-old woman who had signs and symptoms of an intra-abdominal catastrophe. The patient underwent laparotomy and at surgery had findings suggesting primary intra-abdominal pathology. Autopsy results indicated that pulmonary embolism was responsible for the patient's presentation and death.

Abdomen, Acute↗
PubMedDate not supplied

A review of etomidate for rapid sequence intubation in the emergency department.

Currently, there is no one drug that is the agent of choice for induction in rapid sequence intubation in the emergency department (ED). All agents currently used as induction agents in the ED offer distinct advantages for various clinical conditions, but each has a significant side effect profile and specific contraindications that limit its use in many common clinical settings. A review of the data available from the anesthesia literature suggests that etomidate possesses many properties that may make it the agent of choice for rapid sequence intubations in the ED. These advantages include excellent pharmacodynamics, protection from myocardial and cerebral ischemia, minimal histamine release, and a hemodynamic profile that is uniquely stable. Disadvantages include a lack of blunting of sympathetic response to intubation, a high incidence of myoclonus, prominent nausea and vomiting, potential activation of seizures in patients with epileptogenic foci, and impaired glucocorticoid response to stress. Further studies are needed to evaluate the advantages and disadvantages of the use of etomidate for rapid sequence intubation in the ED.

Adolescent↗
PubMedDate not supplied

Quantification of the effects of respiration and parallax on inferior vena caval filter position.

PURPOSE: The change in inferior vena caval (IVC) filter position at follow-up relative to the filter position at implantation has been used as a criterion for evaluation and comparison of these devices. Perceived changes in filter position may be due to respiratory movement and/or changes in parallax between the initial and follow-up imaging studies. In this study the authors evaluated and attempted to quantify the effects of respiratory movement and parallax. PATIENTS AND METHODS: After placement of an IVC filter, radiographs of the abdomen were taken at maximum inspiration and maximum expiration in 30 patients. The effect of parallax on apparent filter movement was studied by using a phantom. RESULTS: The average filter movement on inspiration/expiration radiographs (corrected for magnification) was 3.6 mm +/- 2.2. An 8.5-mm maximal change secondary to parallax was seen in the phantom study. CONCLUSION: When follow-up images are obtained, efforts should be made to closely reproduce patient positioning and patient respiration to reduce errors in the interpretation of filter migration.

Follow-Up Studies↗
PubMedDate not supplied

Instrument for scanning the angular variation of irradiance in ultraviolet phototherapy cabinets.

An instrument is described that measures irradiance and the angular distribution of the intensity of ultraviolet radiation sources inside phototherapy cabinets. Failed lamps and lamps with higher or lower outputs are readily identified. The measurements are controlled from outside the cabinet, thus reducing the risk to staff from exposure to ultraviolet radiation.

Calibration↗
PubMedDate not supplied

An instrument to investigate temporal processing mechanisms with the multifocal ERG.

The multifocal ERG technique is a powerful method of studying the function of different areas of the retina. Display systems such as the CRT, which are commonly used for stimulation, are subject to limitations such as those imposed by the raster method of scanning. This work describes a novel stimulating display using LEDs that retains the established hexagonal areas but overcomes some of the limitations of the CRT display systems. The design and construction of the instrument is described together with some preliminary results.

Electroretinography↗
PubMedDate not supplied

A calibration service for biomedical instrumentation maintenance laboratories.

An in-house calibration laboratory for the Biomedical Instrumentation Maintenance Services of the hospitals in the West of Scotland was established in 1993. This paper describes the development of this calibration service in the context of an overall quality system and also estimates its costs. Not only does the in-house service have many advantages but it is shown to be cost effective for workloads exceeding 260 items per annum.

Biomedical Engineering↗
PubMedDate not supplied

Segregation and mapping of allozymes of the apple maggot fly.

The genetics of electrophoretic enzyme variants (allozymes) of 11 enzymes of the apple maggot, Rhagoletis pomonella, has been investigated by single-pair crosses. All allozymes segregated as simple Mendelian genes. Null alleles occur at two enzymes--phosphoglucomutase and alcohol dehydrogenase. Five linkage groups have been established.

Animals↗
PubMedDate not supplied

Rapid cessation of focally induced generalized seizures in rats through microinfusion of lidocaine hydrochloride into the focus.

An experimental animal model of complex partial seizures which become secondarily generalized is produced by microinfusion of the GABA antagonist bicuculline (BIC) into the deep prepiriform cortex (DPC) of rats. In the present study, we investigated the effects of microinfusion of the local anesthetic, lidocaine hydrochloride, directly into the BIC focus in the DPC and demonstrated that direct inactivation of the focus arrested a focal seizure that was in progress. A measure of the integrated amplitude of the electrocorticogram (ECoG) and behavioral seizure scores from unanesthetized and freely moving rats were used to address this question quantitatively. Microinfusion of 2% lidocaine hydrochloride into the BIC focus significantly reduced the integrated amplitude of the ECoG to levels that did not differ from baseline in either hemisphere (mean = 112% ipsilateral, 99% contralateral), whereas saline microinfusion had no effect (mean = 175% ipsilateral, 125% contralateral). Moreover, ECoG reductions after lidocaine were present as soon as the microinfusion was complete. Behaviorally, clonic seizure severity was assessed on a rating scale of 0-5. Lidocaine microinfusion significantly reduced the seizure scores to values not different from baseline during the first postinfusion measurement period (i.e., 30 s). Microinfusion of saline alone also significantly reduced behavioral seizure severity, although to a lesser degree and not as rapidly as lidocaine. This effect suggests the need for caution in interpretation and design of studies investigating the anticonvulsant effects of various pharmacologic agents when microinfusions are used.

Animals↗