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Biomedical subjects

P D Schneider

Publications and source records attributed to P D Schneider.

At least 19 recordsLinked to original sources
PubMed2001

Resident experience and opinions about physician-assisted death for cancer patients.

HYPOTHESIS: Surgical residents and staff oncologists (surgical, medical, and radiation therapy) have similar opinions on participation in physician-assisted death for patients with terminal cancer. DESIGN: Prospective survey. SETTING: Tertiary care referral center. PARTICIPANTS: Residents undergoing surgical training (n = 56) and faculty oncologists (n = 24) of all specialties (surgical, medical, and radiation therapy). MAIN OUTCOME MEASURES: Subjects were queried regarding previous experience and willingness to participate (either directly or indirectly) in assisted death for terminal cancer patients. RESULTS: Response rates were 39% (22 of 56) for the residents and 87% (21 of 24) for the oncologists. Of those who responded, 86% (19 of 22) of the residents would aid any of the hypothetical patients with assisted death, whereas only 19% (4 of 21) of the staff oncologists expressed willingness to perform the same service. Furthermore, 32% (7 of 22) of the residents reported previous involvement in a case of assisted death from any disease, whereas only 19% (4 of 21) of the staff oncologists reported previous direct experience with assisted death in the terminal cancer patient. CONCLUSIONS: Surgical residents tend to have more experience with assisted death and are much more willing than staff oncologists to aid terminal cancer patients with this procedure. These opinions and practices are probably not the result of medical education but are developed from personal values.

Adult↗
PubMed2001

Cost-benefit analysis of biopsy methods for suspicious mammographic lesions; discussion 994-5.

HYPOTHESIS: Stereotactic core biopsy (SCB) is more cost-effective than needle-localized biopsy (NLB) for evaluation and treatment of mammographic lesions. DESIGN: A computer-generated mathematical model was developed based on clinical outcome modeling to estimate costs accrued during evaluation and treatment of suspicious mammographic lesions. Total costs were determined for evaluation and subsequent treatment of cancer when either SCB or NLB was used as the initial biopsy method. Cost was estimated by the cumulative work relative value units accrued. The risk of malignancy based on the Breast Imaging Reporting Data System (BIRADS) score and mammographic suspicion of ductal carcinoma in situ were varied to simulate common clinical scenarios. MAIN OUTCOME MEASURES: Total cost accumulated during evaluation and subsequent surgical therapy (if required). RESULTS: Evaluation of BIRADS 5 lesions (highly suggestive, risk of malignancy = 90%) resulted in equivalent relative value units for both techniques (SCB, 15.54; NLB, 15.47). Evaluation of lesions highly suspicious for ductal carcinoma in situ yielded similar total treatment relative value units (SCB, 11.49; NLB, 10.17). Only for evaluation of BIRADS 4 lesions (suspicious abnormality, risk of malignancy = 34%) was SCB more cost-effective than NLB (SCB, 7.65 vs. NLB, 15.66). CONCLUSIONS: No difference in cost-benefit was found when lesions highly suggestive of malignancy (BIRADS 5) or those suspicious for ductal carcinoma in situ were evaluated initially with SCB vs. NLB, thereby disproving the hypothesis. Only for intermediate-risk lesions (BIRADS 4) did initial evaluation with SCB yield a greater cost savings than with NLB.

Biopsy↗
PubMed2001

Posthysterectomy vault eversion with a large retroperitoneal mass.

A woman with complete vaginal eversion was found to have a large pelvic mass, extending from the rectovaginal septum to the presacral space. This 66-year-old woman with posthysterectomy vaginal eversion complained of pelvic fullness. A pessary provided relief of the prolapse, but the symptom of fullness persisted. Physical examination did not identify a pelvic mass. Computed tomography (CT) and magnetic resonance imaging (MRI) demonstrated a 9 cm tumor of the rectovaginal septum, extending to the presacral space. At laparotomy the patient had a massive neurofibroma arising from the anterior rectal wall. This case is of interest because the complete vaginal prolapse obscured the diagnosis of this large pelvic tumor. CT and MRI were useful in identifying and characterizing the mass. To our knowledge, this is the first reported case of vaginal prolapse with a large pelvic mass.

Aged↗
PubMed2000

Comparison of minimally invasive esophagectomy with transthoracic and transhiatal esophagectomy.

HYPOTHESIS: Minimally invasive esophagectomy can be performed as safely as conventional esophagectomy and has distinct perioperative outcome advantages. DESIGN: A retrospective comparison of 3 methods of esophagectomy: minimally invasive, transthoracic, and blunt transhiatal. SETTING: University medical center. PATIENTS: Eighteen consecutive patients underwent combined thoracoscopic and laparoscopic esophagectomy from October 9, 1998, through January 19, 2000. These patients were compared with 16 patients who underwent transthoracic esophagectomy and 20 patients who underwent blunt transhiatal esophagectomy from June 1, 1993, through August 5, 1998. MAIN OUTCOME MEASURES: Operative time, amount of blood loss, number of operative transfusions, length of intensive care and hospital stays, complications, and mortality. RESULTS: Patients who had minimally invasive esophagectomy had shorter operative times, less blood loss, fewer transfusions, and shortened intensive care unit and hospital courses than patients who underwent transthoracic or blunt transhiatal esophagectomy. There was no significant difference in the incidence of anastomotic leak or respiratory complications among the 3 groups. CONCLUSION: Minimally invasive esophagectomy is safe and provides clinical advantages compared with transthoracic and blunt transhiatal esophagectomy.

Aged↗
PubMed2000

Availability of content information does not improve performance on computerized case simulations.

BACKGROUND: A previous study evaluated repeated, serial administrations of computer-based simulations. The data demonstrated an increase in scores across rotations during the academic year, but no difference between scores in successive years. METHODS: The initial study only indirectly assessed the effect of information sharing on measured performance. To directly assess the effect of information transfer, 8 computer-based case simulations were administered over 2 consecutive years to 220 third-year students at the conclusion of 12 surgical clerkship rotations (6 per year). During the second year of administration information regarding content area, in the form of the case stem or introductory lead-in material, was provided to each rotation of students prior to the examination based on a sequential algorithm. RESULTS: The data demonstrate no increase in overall mean score for the examination over the 2 years. Scores were significantly different for 2 of the 8 cases, increasing in the one and decreasing in the other. CONCLUSIONS: The data demonstrate no evidence that prior knowledge of content area influences the scores of successive classes on computerized models of performance assessment.

Adult↗
PubMed2000

Radio-frequency electrocautery ablation of mammary tissue in swine.

PURPOSE: To establish the size, configuration, and histopathologic features of acute, subacute, and chronic radio-frequency (RF) electrocautery of mammary tissue in swine. MATERIALS AND METHODS: Eighteen RF treatments were performed in the mammary tissue of three domestic swine under ultrasonographic (US) guidance. Histopathologic examination was performed immediately after (acute animal); 2 weeks after (subacute animal); and 4 weeks after (chronic animal) treatment. RESULTS: In the acute animal, lesions were firm nodules on palpation and had a distinct line of demarcation between necrotic and viable mammary tissue (mean lesion volume, 14.24 cm(3); largest volume, 29.06 cm(3)). In the subacute animal, there was diffuse coagulation necrosis with neutrophilic infiltrates at the periphery (mean lesion volume, 6.46 cm(3); largest volume, 9.47 cm(3)), and two treatment areas had a secondary bacterial infection. In the chronic animal, lesions were still palpable and firm (mean lesion volume, 11.67 cm(3); largest volume, 25.5 cm(3)), and five of six treatment sites had an area of gray to white fibrotic tissue that blended with the surrounding tissue. However, one site had a pale yellow area of central necrosis surrounded by a fibrotic area. In both the subacute and chronic animals, two and one treatment site, respectively, had minimal areas of skin necrosis. CONCLUSION: RF ablation of breast tissue is feasible in this animal model. Problems included minimal skin erythema, residual firm treatment regions at 4 weeks, slightly variable margins of coagulation necrosis, and occasional bacterial infection.

Animals↗
PubMed2000

Long-term kinetic study of beta-carotene, using accelerator mass spectrometry in an adult volunteer.

We present a sensitive tracer method, suitable for in vivo human research, that uses beta-[(14)C]carotene coupled with accelerator mass spectrometry (AMS) detection. Using this approach, the concentration-time course of a physiological (306 microgram 200 nCi) oral dose of beta-[(14)C]carotene was determined for 209 days in plasma. Analytes included beta-[(14)C]carotene, [(14)C]retinyl esters, [(14)C]retinol, and several [(14)C]retinoic acids. There was a 5.5-h lag between dosing and the appearance of (14)C in plasma. Labeled beta-carotene and [(14)C]retinyl esters rose and displayed several maxima with virtually identical kinetic profiles over the first 24-h period; elevated [(14)C]retinyl ester concentrations were sustained in the plasma compartment for >21 h postdosing. The appearance of [(14)C]retinol in plasma was also delayed 5.5 h postdosing and its concentration rose linearly for 28 h before declining. Cumulative urine and stool were collected for 17 and 10 days, respectively, and 57.4% of the dose was recovered in the stool within 48 h postdosing. The stool was the major excretion route for the absorbed dose. The turnover times (1/k(el)) for beta-carotene and retinol were 58 and 302 days, respectively. Area under the curve analysis of the plasma response curves suggested a molar vitamin A value of 0.53 for beta-carotene, with a minimum of 62% of the absorbed beta-carotene being cleaved to vitamin A.In summary, AMS is an excellent tool for defining the in vivo metabolic behavior of beta-carotene and related compounds at physiological concentrations. Further, our data suggest that retinyl esters derived from beta-carotene may undergo hepatic resecretion with VLDL in a process similar to that observed for beta-carotene.

Adult↗
PubMed1999

Intrinsic erythrocyte labeling and attomole pharmacokinetic tracing of 14C-labeled folic acid with accelerator mass spectrometry.

Long-term physiologic tracing of nutrients, toxins, and drugs in healthy subjects is not possible using traditional decay counting of radioisotopes or stable isotope mass spectrometry due to radiation exposure and limited sensitivity, respectively. A physiologic dose of 14C-labeled folic acid (35 microg, 100 nCi) was ingested by a healthy adult male and followed for 202 days in plasma, erythrocytes, urine, and feces using accelerator mass spectrometry. All samples and generated wastes were classified nonradioactive and the subject received a lifetime-integrated radiological effective dose of only 11 microSv. Radiolabeled folate appeared in plasma 10 min after ingestion but did not appear in erythrocytes until 5 days later. Approximately 0.4% of the erythrocytes were intrinsically labeled with an average of 130 (14)C atoms during erythropoiesis from the pulse of plasma [14C]folate. An appropriate radiocarbon-labeled precursor can intrinsically label DNA or a specific protein during synthesis and obtain limits of quantitation several orders of magnitude below that of stable isotope methods.

Adult↗
PubMed1999

Repeated use of computerized case simulations in a test format does not present a security risk.

BACKGROUND: Computer-based examination formats permit evaluation of patient care strategies in a realistic context. Because such examinations are complex and difficult to develop, the same case simulations must often be used on multiple occasions. METHODS: To determine if repeated, serial administration of computerized case simulations influences performance, 8 simulations were administered over 2 consecutive years to 252 third-year medical students at the conclusion of 16 surgical clerkship rotations (8 per year). One-way analyses of variance were used to compare scores across rotations during the year and to compare scores between 2 consecutive academic years. Scheffe pairwise comparisons were used to identify trends within each academic year. RESULTS: The data demonstrate an increase in scores across rotations during the year. There is, however, no difference between scores in successive years. CONCLUSIONS: The data are consistent with an increase in knowledge during the course of the year, without evidence that test information transfer influences the performance of successive classes.

Clinical Clerkship↗
PubMed1998

The dynamics of folic acid metabolism in an adult given a small tracer dose of 14C-folic acid.

Folate is an essential nutrient that is involved in many metabolic pathways, including amino acid interconversions and nucleotide (DNA) synthesis. In genetically susceptible individuals and populations, dysfunction of folate metabolism is associated with severe illness. Despite the importance of folate, major gaps exist in our quantitative understanding of folate metabolism in humans. The gaps exist because folate metabolism is complex, a suitable animal model that mimics human folate metabolism has not been identified, and suitable experimental protocols for in vivo studies in humans are not developed. In general, previous studies of folate metabolism have used large doses of high specific activity tritium and 14C-labeled folates in clinical patients. While stable isotopes such as deuterium and 13C-labeled folate are viewed as ethical alternatives to radiolabeled folates for studying metabolism, the lack of sensitive mass spectrometry methods to quantify them has impeded advancement of the field using this approach. In this chapter, we describe a new approach that uses a major analytical breakthrough, Accelerator Mass Spectrometry (AMS). Because AMS can detect attomole concentrations of 14C, small radioactive dosages (nCi) can be safely administered to humans and traced over long periods of time. The needed dosages are sufficiently small that the total radiation exposure is only a fraction of the natural annual background radiation of Americans, and the generated laboratory waste may legally be classified non-radioactive in many cases. The availability of AMS has permitted the longest (202 d) and most detailed study to date of folate metabolism in a healthy adult human volunteer. Here we demonstrate the feasibility of our approach and illustrate its potential by determining empirical kinetic values of folate metabolism. Our data indicate that the mean sojourn time for folate is in the range of 93 to 120 d. It took > or = 350 d for the absorbed portion of small bolus dose of 14C-folic acid to be eliminated completely from the body.

Area Under Curve↗
PubMed1995

Laparoscopic gastrostomy: a safe method for obtaining enteral access.

Laparoscopic gastrostomy is a relatively new procedure which does not require a laparotomy but which allows direct visualization of the gastrostomy tube entering the stomach and the stomach-parietal peritoneum interface. The role of the laparoscopically placed gastrostomy for enteral access has yet to be defined. Our aim was to compare laparoscopic gastrostomy with open surgical gastrostomy to determine the effectiveness and safety of laparoscopic gastrostomy as a method for obtaining long term enteral access. We reviewed the records of 32 patients (December 1992 to April 1994) who had laparoscopic gastrostomy (group I) and 37 patients (January 1987 to December 1993) who had open gastrostomy (group II). The indications, length of operation, and morbidity and mortality rates in both groups were compared. The underlying diseases and indications for gastrostomy placement were similar in both groups. Both groups included primarily patients who were not candidates for upper endoscopy. Operative time was significantly shorter in the laparoscopic gastrostomy group (38 +/- 7 min) than in the open gastrostomy group (62 +/- 19), P < 0.0001. Major complication for laparoscopic gastrostomy was 6% and for open gastrostomy was 11%. There was no procedure-related mortality in group I and three patients in group II died in the immediate postoperative period. Major morbidity and mortality rates were not significantly different between the two groups. Laparoscopic gastrostomy is a safe and effective alternative to open gastrostomy, particularly in patients unable to undergo upper endoscopy or in patients undergoing a concomitant laparoscopic procedure.

Evaluation Studies as Topic↗
PubMed1993

Intraoperative autotransfusion in hepatic resection for malignancy. Is it safe?

To evaluate whether intraoperative autologous transfusion increases the risk of hematogenous dissemination of tumor we reviewed the risk of lung metastasis as well as disease-free and long-term survival of patients who underwent resection of malignant hepatic neoplasms with this technique. A retrospective review of patients undergoing liver resection for malignant disease revealed 39 patients in whom intraoperative autologous transfusion was used. The 2-year actuarial survival in the patients in this series, as calculated with the Kaplan-Meier method, was predicted to be 75%. Two-year actuarial disease-free survival was predicted to be 28%, and the risk of developing lung metastasis at 3 years was estimated to be 40%. The predicted overall survival and risk of recurrence in this series compare favorably with published data for patients in whom intraoperative autologous transfusion was not used.

Actuarial Analysis↗