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Biomedical subjects

R S Dixon

Publications and source records attributed to R S Dixon.

At least 19 recordsLinked to original sources
PubMed2001

Adolescents' perceptions of a health survey using multimedia computer-assisted self-administered interview.

OBJECTIVE: To ascertain young people's perceptions of an adolescent health survey when administered by multimedia computer assisted self-administered Interview (M-CASI) through analysis of (1) questionnaire item responses and (2) focus group interviews. METHODOLOGY SETTING: Auckland, New Zealand, 1999. STUDY TYPE: Pilot testing of a 488-item branching questionnaire delivered using a youth-oriented and user-friendly M-CASI interface in a variety of settings using both desktop and laptop computers. Post pilot focus groups of participants identifying their perceptions and experiences of the survey. SAMPLE: 110 school students aged 12 to 18 years. RESULTS: The mean number of questions answered by participants was 316 with the median time to completion being 48 minutes. On average 65% of the total number of questions were seen and of these 1.5% were deliberately not answered. A high level of acceptability and enjoyment of M-CASI was found in the analysis of focus group responses and agreed with the item responses relating to M-CASI within the questionnaire itself. Participants identified privacy and confidentiality as being particularly important for the honesty of their responses. The passive matrix screens of the computers were popular as they could only be viewed from in front. CONCLUSIONS: M-CASI is an acceptable instrument for the administration of a youth health survey. Laptop computers with passive matrix screens are able to enhance perceptions of privacy and confidentiality, which may improve honesty of responses. IMPLICATIONS: M-CASI is now feasible and offers advantages in health surveying.

Adolescent↗
PubMed2000

Extracorporeal liver perfusion using human and pig livers for acute liver failure.

BACKGROUND: Patients with fulminant hepatic failure (FHF) often die awaiting liver transplantation. Extracorporeal liver perfusion (ECLP) has been proposed as a method of "bridging" such patients to transplantation. We report the largest experience to date of ECLP using human and porcine livers in patients with acute liver failure. METHODS: Patients with FHF unlikely to survive without liver transplantation were identified. ECLP was performed with human or porcine livers. Patients underwent continuous perfusion until liver transplantation or withdrawal of support. Two perfusion circuits were used: direct perfusion of patient blood through the extracorporeal liver and indirect perfusion with a plasma filter between the patient and the liver. FINDINGS: Fourteen patients were treated with 16 livers in 18 perfusion circuits. Nine patients were successfully "bridged" to transplantation. ECLP stabilized intracranial pressure (ICP) and cerebral perfusion pressure (CPP). Arterial ammonia levels fell from a median of 146 to 83 micromol/liter within 12 hr and this reduction was maintained at least 48 hr. Pig and human ECLP lowered ammonia levels equally. Serum bilirubin levels also fell from a median of 385 to 198 micromol/liter over the first 12 hr but the response was not sustained as well with porcine livers. There was no immunological benefit to using the the filtered perfusion circuit. INTERPRETATION: These data demonstrate that ECLP is safe and can provide metabolic support for comatose patients with fulminant hepatic failure for up to 5 days. While labor and resource intensive, this technology is available to centers caring for patients with acute liver failure and deserves wider evaluation and application.

Adolescent↗
PubMed1999

Transmission of live laparoscopic surgery over the Internet2.

BACKGROUND: Video broadcasting of surgical procedures is an important tool for education, training, and consultation. Current video conferencing systems are expensive and time-consuming and require preplanning. Real-time Internet video is known for its poor quality and relies on the equipment and the speed of the connection. The Internet2, a new high-speed (up to 2,048 Mbps), large bandwidth data network presently connects more than 100 universities and corporations. We have successfully used the Internet2 to broadcast the first real-time, high-quality audio/video program from a live laparoscopic operation to distant points. METHODS: Video output of the laparoscopic camera and audio from a wireless microphone were broadcast to distant sites using a proprietary, PC-based implementation of H.320 video conferencing over a TCP/IP network connected to the Internet2. The receiving sites participated in two-way, real-time video and audio communications and graded the quality of the signal they received. RESULTS: On August 25, 1998, a laparoscopic Nissen fundoplication was transmitted to Internet2 stations in Colorado, Pennsylvania, and to an Internet station in New York. On September 28 and 29, 1998, we broadcast laparoscopic operations throughout both days to the Internet2 Fall Conference in San Francisco, California. Most recently, on February 24, 1999, we transmitted a laparoscopic Heller myotomy to the Abilene Network Launch Event in Washington, DC. CONCLUSIONS: The Internet2 is currently able to provide the bandwidth needed for a turn-key video conferencing system with high-resolution, real-time transmission. The system could be used for a variety of teaching and educational programs for experienced surgeons, residents, and medical students.

General Surgery↗
PubMed1997

Evaluation of hyperplastic goiter in a colony of Syrian hamsters (Mesocricetus auratus).

Hyperplastic goiter was diagnosed during routine health monitoring of a closed Syrian hamster colony (SG). Adult and juvenile hamsters were affected at a prevalence of 45%. Histologic examination of the enlarged thyroid gland revealed marked follicular cell hyperplasia. Because prevalence of thyroid hyperplasia in this colony exceeded the 6 to 7% prevalence expected in aged hamsters, additional studies were performed to investigate the pathogenesis of this condition. Juvenile male SG hamsters and age- and sex-matched Syrian hamsters that did not have increased prevalence of goiter were obtained from an unrelated source (Fredrick Cancer Research and Development Center [FCRDC]). The thyroid glands of hamsters were evaluated by 123I radionuclide imaging. Eight of 18 SG hamsters and none of the FCRDC hamsters had a diagnosis of enlarged thyroid gland. Serum baseline and post-thyrotropin thyroxine concentrations in SG hamsters were not statistically different from those in FCRDC hamsters. To investigate whether diet played a role in development of hyperplastic goiter, for 6 months 15 FCRDC hamsters were fed the diet that had been fed to SG hamsters (mouse breeder diet), and five were fed a control diet. To determine whether dietary change would result in resolution of goiter, affected SG hamsters were fed a control diet for 3 months. At the end of each feeding trial, thyroid gland uptake of 123I was reevaluated. The amount of 123I taken up by the thyroid glands of FCRDC hamsters fed the mouse breeder diet was not significantly different from that of controls. In contrast, thyroid gland uptake of 123I remained high for all affected SG hamsters fed the control diet. On the basis of results of these investigations, diet was ruled out as the cause of goiter. Also, a diagnosis of euthyroid hyperplastic goiter was made for the SG hamsters. A genetic cause is suspected to play a role in the increased prevalence of goiter in SG hamsters.

Animals↗
PubMed1981

Erythroplasia (Queyrat) of conjunctiva.

Erythroplasia of Queyrat (EQ) is an epidermoid carcinoma in situ which is histologically identical with Bowen's disease of the skin but involves mucosal surfaces. The lesion is known to occur on the glans penis, the vulva, and the oral mucosa. Two cases of EQ of the conjunctiva that developed several years after radiotherapy for basal cell carcinoma of the eyelids are here reported. The signs and symptoms closely mimicked those of chronic conjunctivitis. The lesions were excised by the microscopically controlled excision of Mohs. It is recommended that biopsy material be obtained in patients who develop a nonresolving chronic conjunctivitis, especially when there is history of radiotherapy of the eyelids.

Carcinoma in Situ↗
PubMed1980

Sebaceous carcinoma of the eyelid.

Meibomian carcinoma is rare but carries a grave prognosis. The lesion may be easily mistaken for inflammatory condition. Therefore, any nodular or recurrent lesion on the eyelid of an elderly person should be examined histologically. A case is presented in which the tumor was successfully treated by the Mohs microscopically controlled excision.

Adenocarcinoma↗
PubMed1979

The role of Whitnall's ligament in ptosis surgery.

Whitnall's ligament has been described functionally as a check ligament of the levator. Our anatomic dissections and operative findings indicate that this ligament is primarily a support for the upper eyelid and superior orbit. Whitnall's ligament is frequently confused with the levator horns and is unfortunately cut during many ptosis procedures. This is to be avoided because much larger levator resections are required when this ligament's support to the upper lid and the fulcrum effect for the levator are lost. Preserving and enhancing the function of Whitnall's ligament improves the efficiency of the levator, making large levator resections rarely necessary. We have noted no more lid lag than that seen with other forms of levator surgery.

Blepharoptosis↗
PubMed1979

Aponeurotic ptosis surgery.

The recognition of defects in the levator aponeurosis associated with a renewed interest in eyelid anatomy has led to a revival of aponeurotic surgery. We describe our approach with emphasis on techniques that help obtain and maintain avascular planes throughout surgery. The advantages of this approach include preservation of (1) tear-producing structures, (2) Müller's muscle and Whitnall's ligament, and (3) normal anatomical planes and structures of the eyelid. Our results indicate that this technique is the procedure of choice for acquired ptosis cases. It also gives good results in congenital ptosis cases with at least 5 mm of function. Overcorrection at surgery is necessary in all cases. Tucking of the aponeurosis is to be avoided as no raw healing surfaces are obtained. Results in 60 eyelids with a minimum follow-up of one year are presented.

Blepharoptosis↗
PubMed1979

Neuromyopathic ptosis: a new surgical approach.

Neuromyopathic ptosis is a progressive disorder frequently associated with other ocular abnormalities. These include dry eyes, absent Bell's phenomenon, protractor weakness, and heterotropia. Thus, correction of this ptosis has not been well described and is avoided by many surgeons. Since ptosis usually occurs early in life, correction is of functional, economic, and cosmetic importance. Clinical and histologic findings suggest that degeneration and defects of the levator aponeurosis contribute to the ptosis. During the past two years, we have used the aponeurotic approach to correct neuromyopathic ptosis. We describe 19 eyelids with a minimum one-year follow-up. Most eyelids were purposely undercorrected. A mean lid elevation of 3.3 mm with good symmetric results was obtained. Procedures were performed under local anesthesia. Advantages of this technique are (1) patient cooperation for adjustment of lid height and contour at surgery; (2) preservation of other suspensory structures (Müller's muscle and Whitnall's ligament); (3) easy adjustment of lid height postoperatively; (4) preservation of all tear-producing structures; (5) avoidance of corneal irritation from posterior sutures; and (6) maintenance of anatomic planes, which simplifies reoperation, if necessary. We believe this conservative approach corrects most eyelids with neuromyopathic ptosis.

Adult↗
PubMed1979

The use of thymoxamine in eyelid retraction.

We observed substantial narrowing in 75% of fissures in patients with various types of lid retraction after topical application of aqueous 0.5% thymoxamine (moxisylyte). Even contralateral normal-appearing fissures in thyroid patients responded in this manner. The nonresponders in the lid retraction group included a patient with an orbital pseudotumor and patients with long-standing and stable euthyroid eye disease. No normal subjects' fissures responded greatly to thymoxamine. A substantial reduction in palpebral fissures was seen in all patients with thick extraocular muscles and in 14 of 18 (78%) of all fissures of thyroid patients; the average response was 2.3 mm. This effect may last for five hours after thymoxamine administration. Thymoxamine may be of use as a diagnostic test for thyroid eye disease, and if it can be modified to cause less ocular irritation, it may be beneficial in the medical treatment of eyelid retraction.

Adult↗
PubMed1978

Blood clearance rates of technetium-99m albumin preparations: concise communication.

Technetium-labeled human serum albumin (HSA) is extensively used as a cardiac imaging agent. An evaluation of the blood-clearance rates of electrolytically reduced HSA (EHSA) and four stannous-reduced HSA (SnHSA) preparations was conducted in dogs, and was compared with that of radioiodinated HSA (IHSA). The EHSA was found to have a clearance rate only about 1.5 times that of IHSA, whereas the SnHSA agents were cleared at two to five times the rate of IHSA. Thus, EHSA has definite advantages over SnHSA preparations for the purposes of blood-volume determinations required in quantitative cardiac studies and for the reduction of extravascular background in the accurate delineation of cardiac boundaries.

Animals↗
PubMed1977

Monitoring resuscitation of the injured patient.

Physicians are being called on with increasing frequency to initiate resuscitation of the severely injured patient. The medical literature is confusing regarding the best way that this can be done. A study was undertaken to evaluate simultaneously four common, easily measured indexes--blood pressure, pulse rate, central venous pressure, and pulmonary artery pressure. A shock-trauma model employing laboratory-bred beagle dogs was developed. Results indicate that the best single index is pulmonary artery pressure. Certain physiologic principles make central venous pressure an unreliable index.

Animals↗
PubMed1977

Use of an in vivo oxygen electrode to determine the effect of hemorrhagic shock on liver oxygen tension.

Measurement of arterial and liver tissue oxygen tension (PO2) in animals subjected to hemorrhagic shock demonstrates a significant (p less than 0.001) decrease in tissue PO2 while PaO2 remains essentially unchanged. In fact, marked increase in PaO2 fail to increase tissue PO2 to control levels, demonstrating that the act of increasing FIO2 and/or PaO2 is inadequate treatment of decreased tissue oxygenation in marginal or low flow states. Measurement of tissue PO2 in a variety of clinical situations seems warranted to allow alterations of therapy to improve flow when indicated by inadequate tissue oxygenation. The application of this simple but extremely useful technic should result in improved survival rates in critically ill patients.

Animals↗
PubMed1976

The effect of hemorrhagic shock on disseminated intravascular coagulation.

Experiments tend to confirm the hypothesis that a thromboplastic substance in the blood stream causes little DIC if blood flow is normal. However, if the same quantity of thromboplastic material is present in a slow capillary flow, it will produce DIC and possible death, with a marked clotting defect.

Animals↗