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Biomedical subjects

C Guse

Publications and source records attributed to C Guse.

At least 19 recordsLinked to original sources
PubMed2006

Programmable implants--from pulsatile to controlled release.

The aim of this study was to develop programmable implants with a reproducible delayed onset of release followed by several weeks of controlled release. For this purpose, a drug-loaded core was embedded into a drug-free bulk-eroding poly(D,L lactic-co-glycolic acid) or poly(D,L lactic acid) mantle. The manufacturing procedure was established and optimized for three mantle materials, which showed delay times ranging from 7 to 83 days. Triglycerides with fatty acid chain lengths from C12 to C18 were investigated as core materials, producing release periods from 2 to 16 weeks. Concomitantly, applying a convolution/deconvolution model showed the possibility of theoretical prediction of the resulting release profiles.

Arylsulfonates↗
PubMed2006

Biocompatibility and erosion behavior of implants made of triglycerides and blends with cholesterol and phospholipids.

Triglycerides are a promising class of material for the parenteral delivery of drugs and have become the focus of tremendous research efforts in recent years. The aim of this study was to investigate the biocompatibility of glyceroltripalmitate as well as the influence of cholesterol and distearoyl-phosphatidyl-choline (DSPC) on the erosion behavior of the lipid. For these investigations, two in vivo studies were carried out, in which cylindrical matrices of 2 mm diameter were manufactured and subcutaneously implanted in immunocompetent NMRI-mice. After excision of the implants, tissue reactions of the animals as well as changes in the weight, shape and microstructure of the implants were investigated. The triglyceride and cholesterol showed good biocompatibility, as indicated by their minimal encapsulation in connective tissue and the absence of inflammatory reactions. Increasing the levels of phospholipid in the implants, however, led to an increased inflammatory reaction. In contrast to cholesterol, which did not affect erosion, the incorporation of DSPC into the triglyceride matrices led to clearly visible signs of degradation.

Animals↗
PubMed2006

Drug release from lipid-based implants: elucidation of the underlying mass transport mechanisms.

The aim of this study was to better understand the mass transport mechanisms involved in the control of drug release from lipid-based implants. Different types of triglyceride-based cylinders were prepared by compression. Glycerol-trilaurate, -trimyristate, -tripalmitate and -tristearate were used as model lipids, lysozyme and pyranine as model drugs. The effects of several formulation and processing parameters on the resulting drug release kinetics in phosphate buffer pH 7.4 were studied and the obtained results analyzed using Fick's second law of diffusion. Interestingly, lysozyme release from implants prepared by compression of a lyophilized emulsion (containing dissolved drug and lipid) was found to be purely diffusion-controlled, irrespective of the type of triglyceride. In contrast, the dominating release mechanism depended on the type of lipid in the case of pyranine-loaded implants prepared by compression of a lyophilized lipid-drug solution: with glycerol-trilaurate and -tristearate the systems were found to be purely diffusion-controlled, whereas also other mass transport phenomena are of importance in glycerol-trimyristate and -tripalmitate-based devices. Similarly, changes in the size of the compressed lipid-drug particles, drug loading and compression force significantly affected the underlying release mechanisms. The addition of a drug-free, poly(lactic-co-glycolic acid) (PLGA)-based coating around the implants delayed the onset of pyranine release for about 20 days. Interestingly, the subsequent drug release was purely diffusion-controlled, irrespective of the type of triglyceride. Also the addition of different amounts (and particle size fractions) of saccharose to pyranine-loaded implants led to purely diffusion-controlled drug release.

Arylsulfonates↗
PubMed2006

Paclitaxel-loaded microparticles and implants for the treatment of brain cancer: preparation and physicochemical characterization.

The aim of this study was to prepare different types of paclitaxel-loaded, PLGA-based microparticles and lipidic implants, which can directly be injected into the brain tissue. Releasing the drug in a time-controlled manner over several weeks, these systems are intended to optimize the treatment of brain tumors. The latter is particularly difficult because of the blood-brain barrier (BBB), hindering most drugs to reach the target tissue upon systemic administration. Especially paclitaxel (being effective for the treatment of ovarian, breast, lung and other cancers) is not able to cross the BBB to a notable extent since it is a substrate of the efflux transporter P-glycoprotein. Both, biodegradable microparticles as well as small, cylindrical, glycerol tripalmitate-based implants (which can be injected using standard needles) were prepared with different paclitaxel loadings. The effects of several formulation and processing parameters on the resulting drug release kinetics were investigated in phosphate buffer pH 7.4 as well as in a diethylnicotinamide (DENA)/phosphate buffer mixture. Using DSC, SEM, SEC and optical microscopy deeper insight into the underlying drug release mechanisms could be gained. The presence of DENA in the release medium significantly increased the solubility of paclitaxel, accelerated PLGA degradation, increased the mobility of the polymer and drug molecules and fundamentally altered the geometry of the systems, resulting in increased paclitaxel release rates.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Monolithic triglyceride matrices: a controlled-release system for proteins.

Matrices made of glyceryl trimyristate as a bioerodible and biocompatible material were manufactured by compression in dimensions that would still allow an application via injection. Pyranine, as a low molecular hydrophilic compound with a low detection limit, and tetramethylrhodamine labeled bovine serum albumin (TAMRA-BSA), as a high molecular weight (66 kDa) protein compound, served as model drugs for release investigations. In vitro studies with pyranine revealed that release depends substantially on the gelatin content of the matrices, which proved to be a useful tool as a release modifier. The duration of the drug release period can be adjusted to a desired time interval ranging from days to weeks by choosing the right gelatin content. Moreover, results illustrated the importance of the molecular weight and the nature of the compound to be incorporated into such matrices, since investigations with TAMRA-BSA showed a more pronounced burst release and altered release profiles and periods. Experiments with hyaluronidase, which served as a model enzyme to assess the problem of protein integrity in such matrices, suggested that proteins may display sufficient stability during the manufacturing procedure of the cylinders or while in contact with the triglyceride matrices. In addition to in vitro investigations, a study in mice revealed that after 15 days of subcutaneous implantation the matrices showed a good in vivo stability. The main conclusion that could be drawn from these results was that triglycerides are a promising alternative to biodegradable polymers for the development of parenteral release systems for protein and peptide drugs.

Animals↗
PubMed2000

Personal values of family physicians, practice satisfaction, and service to the underserved.

BACKGROUND: Personal values are defined as "desirable goals varying in importance that serve as guiding principles in people's lives," and have been shown to influence specialty choice and relate to practice satisfaction. We wished to examine further the relationship of personal values to practice satisfaction and also to a physician's willingness to care for the underserved. We also wished to study associations that might exist among personal values, practice satisfaction, and a variety of practice characteristics. METHODOLOGY: We randomly surveyed a stratified probability sample of 1224 practicing family physicians about their personal values (using the Schwartz values questionnaire), practice satisfaction, practice location, breadth of practice, demographics, board certification status, teaching involvement, and the payor mix of the practice. RESULTS: Family physicians rated the benevolence (motivation to help those close to you) value type highest, and the ratings of the benevolence value type were positively associated with practice satisfaction (correlation coefficient = 0.14, P = .002). Those involved in teaching medical trainees were more satisfied than those who were not involved (P = .009). Some value-type ratings were found to be positively associated with caring for the underserved. Those whose practices consisted of more than 40% underserved (underserved defined as Medicare, Medicaid, and indigent populations) rated the tradition (motivation to maintain customs of traditional culture and religion) value type significantly higher (P = .02). Those whose practices consisted of more than 30% indigent care rated the universalism (motivation to enhance and protect the well-being of all people) value type significantly higher (P = .03). CONCLUSIONS: Family physicians who viewed benevolence as a guiding principle in their lives reported a higher level of professional satisfaction. Likewise, physicians involved in the teaching of medical trainees were more satisfied with their profession. Family physicians who rate the universalism values highly are more likely to provide care to the indigent.

Adult↗
PubMed2000

Conference formats in family practice residencies.

BACKGROUND: This study was intended to establish national baseline data of the current structure of conferences at family practice residencies and to determine if there are differences in conference formats among types of residencies. METHODS: An author-developed survey was mailed to 331 programs stratified by type and randomly selected. Statistical analysis included chi-square tests and non-parametric tests. RESULTS: The response rate was 84%. The average time devoted to lectures was 4.5 hours a week, with the noon hour the most common time. Most speakers were from within the program, and community-based family physicians were rarely present. Structural changes were frequent. CONCLUSIONS: Results indicate that a variety of formats are implemented for meeting Residency Review Committee requirements in the structure of family practice residencies' conferences. Program settings do influence how conferences are structured. More research is needed on this neglected area of formal resident education.

Chi-Square Distribution↗
PubMed1998

Long-term follow-up of iatrogenic phototoxicity.

OBJECTIVE: To evaluate the outcomes of a group of patients who suffered iatrogenic phototoxic injury. METHODS: The medical records of 24 patients (24 eyes) with iatrogenic phototoxicity from 3 medical centers were reviewed. We report the findings from long-term follow-up of these patients with particular attention to visual outcome, type and duration of procedure, and location of the phototoxic lesion. RESULTS: Phototoxic injury occurred after anterior segment surgery in 20 eyes and after vitrectomy in 4 eyes. The mean duration of surgery was 109 minutes; there was no statistically significant difference in duration between the anterior segment procedures and the vitrectomies. Mean final visual acuity was 20/40 for all cases (range, 20/15 to counting fingers) and 20/25 for all anterior segment cases. In vitrectomized eyes, the mean final visual acuity was 20/900. Phototoxic lesions tended to spare the fovea after anterior segment surgery and involve the foveal center after vitrectomy. CONCLUSIONS: In general, patients who suffer phototoxicity do well, and the prognosis is good for extrafoveal lesions. Foveal injury, which often occurs with vitrectomy, usually leads to a worse visual outcome. The development of choroidal neovascularization may have an effect on the ultimate visual outcome as well.

Aged↗
PubMed1998

Improvement in resource utilization after development of a clinical pathway for patients with pressure ulcers.

Clinical pathways are interdisciplinary patient care plans intended to reduce variance and improve quality of care while lowering health care cost. This study was undertaken to determine whether the development of a clinical pathway for care of patients with pressure ulcers can indeed decrease health care costs while preserving quality of care. A clinical pathway for surgical reconstruction of pressure ulcers was developed by standardizing the current practices of our plastic surgeon group. The pathway provided direction in optimal scheduling of physician interventions along with nursing, physical and occupational therapies, and spinal cord rehabilitation interventions. It covered all potential elements of patient care, including laboratory, radiology, dietary services, intravenous fluids, and use of specialty beds. It defined patient outcomes and outlined discharge planning. Pathways were distributed throughout all services caring for patients with pressure ulcers. Patient charts and billing data were reviewed for the 16-month periods before and after initiation of the pathway. No other significant changes in treatment occurred during this time frame. Ninety-seven patient charts were examined (54 before pathway and 43 after pathway implementation). Parameters evaluated included length of stay and total charges (including bed use, medications, laboratory tests, and radiology). Patient readmission rate was also examined. A significant reduction in patient length of stay and total charges was achieved after implementation of the clinical pathway. Reduction was seen not only for patients treated with flaps by plastic surgery but also for patients with pressure ulcers who were not specifically targeted such as those from other services. The readmission rate decreased slightly, although not significantly, after the pathway inception. Total cost saving was almost $11,000 per patient (23 percent). In conclusion, implementation of a clinical pathway, because it standardizes care and reduces variations and duplication of care, can reduce health care cost without impairing quality of care in the treatment of decubitus ulcer patients.

Costs and Cost Analysis↗
PubMed1998

Residents find clinical practice guidelines valuable as educational and clinical tools.

BACKGROUND AND OBJECTIVES: Information regarding clinical practice guideline (CPG) use in residency education is limited. We surveyed a regional population of family practice residents to determine use, attitudes, and curricular needs for practice guidelines. METHODS: A written survey was developed that measured residents' exposure to, frequency of use, attitudes, access, and knowledge about use of CPGs. The survey was mailed to 114 family practice residents. RESULTS: The response rate was 75%. The most frequently seen guidelines were immunization schedules, cancer screening, hyperlipidemia, and hypertension management. The residents reported positive attitudes toward CPGs; 75% thought CPGs were easy to use, 80% thought they improved their efficiency, 78% thought they improved their residency education, and 75% thought they improved patient care. Barriers to effective use of practice guidelines were also identified; 20% knew where to find guidelines in their clinic, 35% had faculty modeling, and 22% knew how to evaluate the validity of a guideline. Eighty-nine percent of respondents desired instruction on CPG use and interpretation. CONCLUSIONS: The surveyed family practice residents have similar usage rates for CPGs as the literature reports for practicing physicians, but residents report more positive attitudes. Barriers that prevent effective use of CPGs in training environments include lack of critical appraisal abilities and faculty role modeling.

Curriculum↗
PubMed1997

Identification of heavy drinkers using a combination of laboratory tests.

OBJECTIVE: This study derived and evaluated a model that used results of commonly performed laboratory tests to identify men who are heavy drinkers. METHOD: The results of 40 commonly available laboratory tests were obtained on a diverse sample of 426 heavy drinkers and 188 light drinkers. A logistic regression equation for identifying heavy drinkers was derived in a training data set of 411 subjects and tested in a validation data set of 203 subjects. RESULTS: Ten laboratory measurements were included in the final regression equation: chloride, sodium, ratio of direct to total bilirubin level, blood urea nitrogen, high density lipoproteins, monocyte count, phosphorus, platelets, aspartate aminotransferase, and mean corpuscular hemoglobin. In the validation data this model correctly identified 98% of the 161 heavy drinkers and 95% of the 42 light drinkers. Other models reported in previous literature were applied to these subjects and did not perform as well. The model performed better for subjects of lower socioeconomic status. CONCLUSIONS: The laboratory tests in our model may help identify heavy drinkers. The performance of models to identify heavy drinkers depends on the demographic characteristics of the subjects.

Adult↗
PubMed1996

The evaluation of screening methods to identify medically unnecessary hospital stay for patients with pneumonia.

OBJECTIVES: This study compared three methods to screen charts of pneumonia patients for excess days. METHODS: A derivation data set was used to statistically derive a severity measure to predict length of stay for pneumonia patients and to refine a clinical algorithm for identifying excess stay. A validation data set was used to compare three computerized methods to screen for unnecessary hospital days: (1) an observed length of stay greater than a target value; (2) an observed stay greater than predicted for the specific patient; and (3) an algorithm that tested whether there were clinical justifications for the entire hospital stay. RESULTS: The sensitivity and specificity for detecting excess stay for the three methods were (1) 0.48 and 0.85 for the observed stay greater than the target value; (2) 0.56 and 0.73 for observed stay greater than predicted; and (3) 0.83 and 0.85 for the algorithm. CONCLUSIONS: These results suggest that computerized clinical algorithms may provide a useful method to detect unnecessary hospital stay.

Adult↗
PubMed1994

The value of the Uniform Clinical Data Set System (UCDSS) in a hospital setting.

BACKGROUND: The Health Care Financing Administration designed the Uniform Clinical Data Set System (UCDSS) to help peer review organizations (PROs) identify problems with patient care. The system currently is being piloted in five states and may be used for the PRO review of Medicare patients from all states by January 1995. This study tested whether UCDSS could be used with modifications for effective internal hospital quality review. METHODS: The UCDSS includes a computer program for collecting information from the medical record and 359 computerized algorithms that evaluate quality of care. For this study, 2,313 randomly chosen medical records from a tertiary care teaching hospital were abstracted with the UCDSS at the time of discharge. Cases flagged by the UCDSS algorithms as having potential quality-of-care problems were referred to a clinical reviewer to evaluate whether the flag was a true positive and to identify reasons for false-positive flags. The algorithms were modified based on this hospital's experience by adding the reasons for false-positive flags as exceptions to the algorithm rules. RESULTS: To abstract the data with the UCDSS required a median time of 45 minutes and a mean time of 55 minutes per medical record. The percentages of algorithm flags that were confirmed upon physician review to have a quality problem were estimated to be 21% for the UCDSS and 43% for the modified UCDSS. The confirmed problem rate varied substantially by algorithm. Confirmed problems were the source of numerous departmental and individual discussions and led to changes in five departmental procedures. CONCLUSIONS: Although the results of this study are preliminary and require further verification, they suggest that with modifications and careful attention to implementation, the UCDSS may be an expensive but potentially useful tool for in-hospital quality review. In-hospital employment of the UCDSS offers more opportunities for practical use of algorithms for continuous quality improvement rather than the sometimes punitive use of system findings by PROs.

Abstracting and Indexing↗
PubMed1994

Severity of illness measures derived from the Uniform Clinical Data Set (UCDSS).

The Health Care Financing Administration (HCFA) plans to use the Uniform Clinical Data Set System (UCDSS) to collect data on hospitalized Medicare patients. This study examined the value of UCDSS data for creating severity of illness measures. UCDSS data were obtained from a study hospital and from a national data set for patients with pneumonia (n = 528) and stroke (n = 565). Models to predict length of stay or an adverse event were derived for each condition using HCFA claims data alone, UCDSS data alone, and UCDSS data supplemented with additional information also abstracted from charts. The models were derived from one set of patients and validated on another. The R2 for predicting length of stay in the validation data for the UCDSS model was 0.29 for pneumonia and 0.19 for stroke compared to R2 values from the claims model of 0.09 for stroke and 0.06 for pneumonia. UCDSS models also were better than claims models for predicting adverse events. The best UCDSS models included International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes and other information requiring clinical judgment, and were improved by adding more information on patient functional status. Some findings were more strongly associated with outcome for the study hospital than for the national data. These results suggest that UCDSS models will predict outcome much better than the claims based models currently used by HCFA for the analysis of hospitalization-related mortality; more functional status information should be added to UCDSS; and despite an extensive objective database, the most predictive UCDSS models require clinician-assigned diagnostic codes.

Aged↗
PubMed1991

Prognostic factors in unresectable hepatocellular cancer: Radiation Therapy Oncology Group Study 83-01.

The Radiation Therapy Oncology Group (RTOG) conducted a Phase I/II study in hepatocellular cancer that closed on September 9, 1987 and some results presented previously. Here, 17 patient characteristics are evaluated to identify any of prognostic significance. Two hundred sixteen patients were entered and 198 (74% with metastases and/or previous chemotherapy) were evaluable. Treatment began with an induction regimen of external beam radiotherapy to the liver (21.0 Gy, 3.0 Gy/Fx, 10 MV photons, 4 days per week) with low-dose chemotherapy (5-Fluorouracil (FU), 500 mg, i.v.; Doxorubicin, 15 mg, i.v.) on treatment Days 1, 3, 5 and 7. In the later stages of these studies, 56 patients received external beam radiotherapy as hyperfractionated treatment (1.2 Gy twice daily, 4 hours separation, 5 days per week, 24.0 Gy total) with similar chemotherapy. One month following induction therapy, cycles of radiolabeled antibody therapy were given every 2 months. Each cycle was derived from a different species of animal and consisted of 30 mCi I-131 antiferritin, Day 0, and 20 mCi, Day 5. On Day -1, 5-FU, 500 mg, and Adriamycin, 15 mg, were administered. The overall median survival for the entire group, including previously treated patients, was 4.9 months. The median survival for alpha-fetoprotein (AFP) - patients not previously treated was 10.5 months. Median survival for all AFP - patients was 8.5 months and for all AFP + patients was 4.6 months (p = 0.006). Of the 17 pretreatment characteristics investigated for prognostic value Karnofsky Performance Score (KPS) (80-100 vs. less than 80) (p = 0.0001), presence/absence of ascites (p = 0.0002), bilirubin level (less than 1.5 vs. greater than or equal to 1.5) (p = 0.018), SGOT (less than or equal to 35 vs. greater than 35) (p = 0.001); alkaline phosphatase (less than or equal to 95 vs. greater than 95) (p = 0.008) were found to be significant independently using a multivariant regression model. The relative risk of dying for the unfavorable component of each of these characteristics was 2.2, 2.0, 1.5, 1.9 and 1.7, respectively. Good and poor prognostic groups were then defined and compared to a similar patient population (RTOG study 83-19) with confirmation of the validity of the model. When stratification for these overpowering clinical factors was incorporated, AFP status was again significant with a relative death rate 1.80 times higher for AFP+ patients. Our recommendations for structuring future prospective randomized trials are discussed and include stratification by AFP status.

Antibodies↗
PubMed1990

Accelerated fractionation radiation therapy for liver metastases: selection of an optimal patient population for the evaluation of late hepatic injury in RTOG studies.

The palliation of hepatic metastases represents a major therapeutic problem in oncology. The generally unfavorable prognosis of patients with liver metastasis may complicate the evaluation of the efficacy and toxicity of various therapeutic modalities. The Radiation Therapy Oncology Group (RTOG) is evaluating new accelerated fractionation schemes for hepatic irradiation. In designing this study it became necessary to identify a favorable subpopulation of patients with an expected median survival of 6 months in whom the late effects of treatment could be evaluated. Data from two RTOG liver metastases studies (7605 and 8003) were analyzed using multi-variate techniques. Cases with a serum bilirubin level of greater than 1.5 mg%, performance score of less than 50, and gastric or pancreatic primary carcinomas were initially excluded because of the adverse influence of these factors on survival. One hundred and ninety cases met the criteria for inclusion in this analysis. A loglinear model was used to identify the patient characteristics associated with a favorable prognosis for survival. These included a performance score of 80-100, colorectal carcinoma primary, and no extrahepatic metastases. A logistic regression equation was derived and confirmed that the probability of surviving at least 6 months depended on the effects of performance score, primary site and the presence or absence of extra-hepatic metastases. Patients with all three favorable factors constituted 30% of the evaluable study population and had a predicted survival of 50% at 6 months. A patient population with these characteristics will be used to study the late effects of accelerated fractionated radiation therapy on the liver.

Breast Neoplasms↗
PubMed1990

Prophylactic irradiation of the para-aortic lymph node chain in stage IIB and bulky stage IB carcinoma of the cervix, initial treatment results of RTOG 7920.

From November 1979 to October 1986, 367 patients were entered onto RTOG 7920 and randomized to receive either pelvic irradiation alone or pelvic plus para-aortic radiation. Patients with Stage IIB cervical carcinoma who had not undergone curative surgery and patients with Stages IB and IIA cervical carcinoma who were determined by digital exam to have primary tumors measuring 4 cm or greater in lateral dimension were eligible for this study. Clinically apparent or surgically involved para-aortic nodes were reason for exclusion from the study. Pelvic irradiation consisted of 1.6-1.8 Gy per day for 5 days per week to a total of 40-50 Gy. Para-aortic irradiation delivered 44 to 45 Gy in 1.6-1.8 Gy per day, 5 days per week. Pelvic irradiation was to be completed in 4 1/2 to 6 1/2 weeks and para-aortic irradiation in 4 1/2 to 5 1/2 weeks. Intracavitary brachytherapy delivered a total of 4000-5000 mg hr of radium-equivalents or 30-40 Gy to point A. Patients were stratified prior to random treatment assignment by histology, para-aortic nodal status (negative vs. unevaluated), and FIGO stage. As of June 1, 1989, 30 cases were excluded, including five patients who were inevaluable. Two patients who refused the assigned treatment were also excluded. Therefore, a total of 330 cases were analyzable. At 5 years the estimates of survival, the primary endpoint, for the pelvic only and pelvic plus para-aortic irradiation arms are 55% and 65%, respectively (p = 0.043). Several secondary endpoints were also analyzed. Estimates for loco-regional control at 5 years are, for pelvic irradiation only, 66%, and for pelvic plus para-aortic irradiation, 75% (p = 0.21). Distant metastases are estimated in 32% of pelvic irradiation only patients and 25% of pelvic plus para-aortic irradiation patients at 5 years (p = 0.17). When the first disease failure patterns are examined, more patients fail distally when treated only with pelvic radiation than when using pelvic plus para-aortic fields (p = .04). In analysis of patients with grade 3 (severe), grade 4 (life-threatening), and grade 5 (fatal complications), 8% of the patients in both groups had grade 3 severe complications. In the pelvic plus para-aortic group, 11 patients had grade 4 and 2 had grade 5 complications, whereas 6 had grade 4 and none had grade 5 in the pelvic only treatment group.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenocarcinoma↗