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Biomedical subjects

D W Johnston

Publications and source records attributed to D W Johnston.

At least 19 recordsLinked to original sources
PubMed2005

Acute toxicity of vanadium to the threespine stickleback, Gasterosteus aculeatus.

Vanadium is widely distributed, occurring in many types of minerals, coal, and petroleum. Anthropogenic sources of vanadium originate from the production, processing, and wastes of these materials. The aquatic toxicity of vanadium to fish species is not well characterized. This study focused on the three-spined stickleback, Gasterosteus aculeatus, a small and widely distributed euryhaline species of fish. The three-spined stickleback is used as an effluent-monitoring species in both Canada and the United States. Five 96-h static renewal acute toxicity tests were performed in moderately hard water with adult fish. The geometric mean and range of the five 96-h LC(50)s based on measured concentrations of total vanadium in the test solution were 3.17 and 2.35-4.07 mg V/L, respectively. A conservative estimation of a safe concentration of vanadium that would not affect survival of adult three-spined sticklebacks over a 96-h exposure period in moderately hard water is approximately 0.30 mg V/L. A comparison with other fish species previously tested suggests that the three-spined stickleback is intermediate in sensitivity to vanadium. Information reported from this study may be useful in effluent toxicity identification evaluations and ecological risk assessments related to vanadium.

Animals↗
PubMed2004

Maternal haemolysis, elevated liver enzymes and low platelets syndrome: perinatal and neurodevelopmental neonatal outcomes for infants weighing less than 1250 g.

OBJECTIVES: To study mortality and short-term morbidity of infants born to women with HELLP (haemolysis, elevated liver enzymes, and low platelets) syndrome and to compare the long-term neurodevelopmental morbidity of a subgroup with birth weight (BWT) less than 1250 g (study group) with weight matched controls. METHODS: Retrospective chart review and prospective neurodevelopmental follow-up through a Perinatal Follow-up clinic. Analysis of perinatal and neonatal data for women diagnosed with HELLP from 1993 to 1996. Neurodevelopmental outcome for the study group was compared to a group of weight matched controls. RESULTS: A total of 109 infants (mean gestational age 32.6 weeks, mean BWT 1766 g) were born to 104 women with HELLP syndrome. There was a significant decrease in mortality (P = 0.002) and morbidity (P < 0.05) with increasing gestational age and birthweight. No significant differences in neonatal mortality and morbidity were present between the infants weighing less than 1250 g study and weight matched control group. However, at 3 years, the study group had fewer children with cerebral palsy (P = 0.024) and mental disability (P trend = 0.07). Mean cognitive index was 99 versus 91 in the controls (P = 0.101). CONCLUSION: Improved health outcomes occur with increased gestational age. Infants with BWT less than 1250 g born to women with HELLP syndrome were not at risk of increased neurodevelopmental disability compared to controls.

Case-Control Studies↗
PubMed2001

The effect of age on pain, function, and quality of life after total hip and knee arthroplasty.

BACKGROUND: As utilization rates for total joint arthroplasty increase, there is a hesitancy to perform this surgery on very old patients. The objective of this prospective study was to compare pain, functional, and health-related quality-of-life outcomes after total hip and total knee arthroplasty in an older patient group (> or =80 years) and a representative younger patient group (55-79 years). METHODS: In an inception community-based cohort within a Canadian health care system, 454 patients who received primary total hip arthroplasty (n = 197) or total knee arthroplasty (n = 257) were evaluated within a month prior to surgery and 6 months postoperatively. Pain, function, and health-related quality of life were evaluated with the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index and the 36-Item Short-Form Health Survey (SF-36). RESULTS: There were no age-related differences in joint pain, function, or quality-of-life measures preoperatively or 6 months postoperatively. Furthermore, after adjusting for potential confounding effects, age was not a significant determinant of pain or function. Although those in the older and younger groups had comparable numbers of comorbid conditions and complications, those in the older group were more likely to be transferred to a rehabilitation facility than younger patients. Regardless of age, patients did not achieve comparable overall physical health when matched with the general population for age and sex. CONCLUSIONS: With increasing life expectancy and elective surgery improving quality of life, age alone is not a factor that affects the outcome of joint arthroplasty and should not be a limiting factor when considering who should receive this surgery.

Age Factors↗
PubMed2001

Total hip and knee replacement surgeries in Alberta utilization and associated outcomes.

OBJECTIVE: Between 1994/95 and 1996/7, the healthcare system in Alberta underwent a radical transformation that saw the regionalization of service delivery and a reduction in overall healthcare funding. The aim of this study is to examine trends in utilization and associated post-operative complications and readmissions for two procedures, total hip arthroplasty (THA) and total knee arthroplasty (TKA) during this period of restructuring. METHODS: This is a six-year retrospective analysis using hospital separation and healthcare insurance plan registry databases. During the study period, we looked at trends in inpatient procedure volumes, average lengths of stay, post-operative complications during the index hospital stay and readmissions within one year. RESULTS: Over a six-year period, the age-sex standardized provincial rate of THAs increased by 18% while the rate of TKAs increased by 73%. Average lengths of stay decreased for both procedures by over 50%. The rate of procedures with at least one post-operative complication within the index episode of care decreased over the study period by 19% for THA and 21% for TKA. Readmissions due to complications of surgery increased overall by 32% for THA and 2% for TKA. Regional and sex differences were observed throughout the period. CONCLUSIONS: While the overall rate of hospitalizations has decreased in Alberta, the rates of THA and TKA procedures have increased. The lengths of stay following these procedures have, at the same time, reduced dramatically. Adverse outcomes as measured by complication rates associated with these procedures have decreased, though readmissions due to complications after surgery have increased.

Alberta↗
PubMed2001

Change in pain and function while waiting for major joint arthroplasty.

The objective of this study was to examine the change in pain and physical function that occurs while waiting for major arthroplasty. Data were collected prospectively from a cohort of 313 patients who were waiting > 1 month for total hip arthroplasty or total knee arthroplasty. The WOMAC and the SF-36 health status instruments were administered at the time the patient was placed on the waiting list and again just before surgery. Minimal amounts of change in pain and physical and psychosocial function occurred for hip and knee arthroplasty patients while they waited. Overall, waiting time did not appear to have a negative impact on the amount of pain and dysfunction experienced.

Adult↗
PubMed2001

Standard anatomical medullary locking (AML) versus tricalcium phosphate-coated AML femoral prostheses.

OBJECTIVES: To compare the preliminary rate and amount of bony ingrowth and calcar resorption between patients receiving either a standard anatomical medullary locking (AML) or a tricalcium phosphate (TCP)-coated AML femoral prosthesis and to compare preliminary clinical results. DESIGN: A prospective, randomized, double-blind clinical trial. SETTING: An acute care tertiary institution. PATIENTS: Between January 1993 and March 1995, 92 patients underwent primary total hip arthroplasty (THA). They were randomized to 2 groups of 46--a control group or a treatment group. Of the 46 subjects enrolled in each group, no significant differences were seen preoperatively with respect to age, sex, diagnosis, clinical and radiographic assessment. Seventy-one patients were followed up for 24 months. INTERVENTIONS: Insertion of either a standard AML femoral implant (control group) or a TCP-coated AML femoral implant (treatment group). OUTCOME MEASURES: The degree of hypertrophy, calcar atrophy and the number of spot welds on standard postoperative radiographs at 6, 12 and 24 months. Clinically, assessment according to the Société internationale de chirurgie orthopédique et de traumatologie (SICOT) scale and a 100-point visual analogue scale (VAS) for pain. RESULTS: There were no prosthetic stem revisions in either group at the 24-month follow-up. Radiographically, bony ingrowth was not significantly different in the TCP-coated stem, by chi2 analysis of the degree of hypertrophy and number of spot welds present. Also by chi2 analysis, the degree of calcar atrophy was not significantly different between groups. The mean VAS score for pain at 24 months was 12.5 for the control and 12.1 for the treatment group. No significant differences were seen in any of the clinical categories of the SICOT Scale over the 24-month interval. CONCLUSION: The objective of TCP-coating--to increase the rate and amount of bony ingrowth while reducing the rate of calcar resorption in non-cemented THA--was not achieved by 24 months postoperatively in our study.

Arthroplasty, Replacement, Hip↗
PubMed2000

Erythropoietin with iron supplementation to prevent allogeneic blood transfusion in total hip joint arthroplasty. A randomized, controlled trial.

BACKGROUND: The optimum regimen of epoetin alfa for prevention of allogeneic blood transfusion is unknown. OBJECTIVE: To determine whether a modified regimen of epoetin alfa reduces allogeneic blood transfusion in patients undergoing hip arthroplasty. DESIGN: Randomized, double-blind, multicenter trial comparing two modified dose regimens of epoetin alfa with placebo. SETTING: 13 teaching hospitals and 4 community hospitals in Canada. PATIENTS: 201 patients undergoing primary hip arthroplasty who had a hemoglobin concentration of 98 to 137 g/L and did not predonate blood. INTERVENTION: Patients were assigned in a 3:5:5 ratio to receive four weekly doses of epoetin alfa, 40 000 U (high-dose; n = 44) or 20 000 U (low-dose; n = 79), or placebo (n = 78), starting 4 weeks before surgery. All patients received oral iron supplementation, 450 mg/d, for 42 or more days before surgery. MEASUREMENTS: The primary end point was allogeneic transfusion. Secondary end points were thromboembolic events and change in reticulocyte count and hemoglobin concentration. RESULTS: Both modified epoetin alfa regimens significantly reduced the need for allogeneic transfusion: Five (11.4%) patients in the high-dose group (P = 0.001) and 18 (22. 8%) patients in the low-dose group (P = 0.003) had transfusion, compared with 35 (44.9%) patients in the placebo group. The hematologic response was substantial in patients who received epoetin alfa. In the high-dose group, low-dose group, and placebo group, the preoperative increase in reticulocyte count was 58.8, 37. 0 and 1.8 x 10(9) cells/L (P < 0.001), respectively, and the increase in hemoglobin concentration was 19.5, 17.2, and 1.2 g/L (P < 0.001). The incidence of thromboembolic events did not differ among groups. CONCLUSIONS: Both modified epoetin alfa regimens were effective compared with placebo in reducing allogeneic transfusion in patients undergoing hip arthroplasty. Patients who received high-dose epoetin alfa had the lowest transfusion rate.

Aged↗
PubMed2000

Cognitive behaviour therapy for cardiovascular diseases.

Cognitive behaviour therapy (CBT) is the main empirically evaluated from of psychological therapy. When applied to cardiovascular disease it can be directed at preventing the occurrence or recurrence of disease or at altering the psychological consequences of disease. Prevention can be achieved through the modification of behavioural risk factors (e.g. smoking, diet) or by attempting to directly modify the psychological processes involved in atherogenesis and thrombogenesis. Successful applications of CBT in cardiovascular disease are described, some the remaining problems indicated and new directions for research pointed out.

Adult↗
PubMed2000

Reducing distress in first level and student nurses: a review of the applied stress management literature.

Following recent evidence of continuing high levels of distress in both trained and student nurses, a critical review of the stress reduction and stress management literature targeting both trained and student nurses is presented. Using a systematic approach, some 36 studies dating from 1980 until the present day were identified adopting either pre-experimental, quasi-experimental or experimental designs. While many work-site programmes in this series were successful in terms of adaptive changes in problem-solving, self-management skills including relaxation and interpersonal skills, affective well-being, and work performance, a number of design and evaluation inadequacies were identified. The relative lack of home-work interface or organizational level programmes to reduce work-related distress, and the scarcity of interventions targeting aspects of the work environment likely to contribute to such outcomes may have contributed to continuing high levels of distress in trained and student nurses. Recommendations regarding the future design, provision and evaluation of such work-site interventions include the further clarification of the structure of perceived stressors, and development of causal models of the stress process to identify the job characteristics 'causing' work-related distress. Such an approach would inform the design and implementation of evidence-based organizational level interventions augmenting strategies to target the health behaviour, lifestyle/risk factors and self-management skills of practitioners and students with attempts to amend problematic elements of the psychosocial work environment.

Adaptation, Psychological↗
PubMed2000

The impact of health status on waiting time for major joint arthroplasty.

This study was conducted to determine the impact of health status on waiting time for major joint arthroplasty in a universal publicly funded health system. Data were collected prospectively from a cohort of 553 patients waiting for total hip or total knee arthroplasty. The WOMAC and SF-36 health status instruments were administered at the time the patient was placed on the waiting list. The outcome measure was length of waiting time. Multivariate analyses found increased body mass index and decreased social function as the only determinants of waiting time. This model explained only 4% of the variance in waiting time. The association between health status and waiting time for arthroplasties appears to be small. These findings suggest that major joint arthroplasty is not prioritized on the basis of burden of illness.

Adult↗
PubMed2000

Intraoperative heparin in addition to postoperative low-molecular-weight heparin for thromboprophylaxis in total knee replacement.

The administration of heparin during operation has been reported to enhance the efficacy of thromboprophylaxis in patients undergoing total hip replacement. We have performed a small pilot study in which intraoperative doses of heparin were given in addition to the usual postoperative thromboprophylaxis with enoxaparin in 32 patients undergoing total knee replacement. The primary endpoint was deep-vein thrombosis (DVT) as demonstrated by bilateral venography on 6 +/- 2 days after operation. Sixteen patients developed DVT; in two the thrombosis was proximal as well as distal and in one the occurrence was bilateral. There was one major haemorrhage. These results are similar to those obtained with the use of postoperative thromboprophylaxis with enoxaparin alone. They do not provide support for the initiation of a larger randomised trial of this approach to management.

Anticoagulants↗
PubMed2000

Health related quality of life outcomes after total hip and knee arthroplasties in a community based population.

OBJECTIVE: To quantify the magnitude of change seen with pain, function, and quality of life outcomes 6 months after total hip and knee arthroplasties (THA, TKA) within a community based cohort of a regional health district. METHODS: An inception cohort of 504 patients who received primary THA (228) or TKA (276) was prospectively followed. All patients resided in the community and were assessed within one month prior to surgery and 6 months postoperatively. Health related quality of life measures were evaluated with the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index and the Medical Outcome Survey Short Form SF-36. Perioperative factors were extracted from medical charts. Health services utilization data were collected from regional health databases. RESULTS: Over 75% of patients reported improvement in joint-specific pain and function, regardless of the type of joint replaced. Other health dimensions such as social function, bodily pain, physical function, vitality, and general health showed significant improvement after surgery. Those psychosocial dimensions with modest changes had baseline values comparable to age and sex adjusted normal values; whereas, bodily pain and physical function, which had large changes, had values lower than the normal values. Ninety-one percent of patients receiving THA were satisfied with their surgery, whereas 77% were satisfied with their TKA. The average length of stay was 7 days and the in-hospital complication rate was 0.34 per patient. CONCLUSION: Large improvements were reported for pain and function after joint arthroplasties, while small to moderate changes were seen in other areas related to quality of life. Patients with hip arthroplasties showed greater improvement in pain and function and were more satisfied with their outcomes than patients with knee arthroplasties. Although pain and function show large improvements, bodily pain and physical function were less than the values reported in the general population.

Aged↗
PubMed1999

The cost-effectiveness of magnetic resonance imaging for patients with internal derangement of the knee.

Magnetic resonance imaging (MRI) has excellent specificity and sensitivity for the diagnosis of internal derangement of the knee (IDK). The use of MRI to screen patients with suspected IDK could avoid unnecessary arthroscopies with a reduction in costs. The purpose of this study was to evaluate the use of arthroscopy among patients with IDK, and to estimate the potential cost-effectiveness of MRI in these patients to avoid unnecessary arthroscopies. The study was based on a retrospective cohort of all patients attending three orthopedic clinics between April and September 1993 with a new diagnosis of IDK. Charts were reviewed in 1994 to allow for a follow-up of more than 6 months. An economic evaluation was performed based on cost-effectiveness ratios (per averted arthroscopy), including direct and indirect costs. There were 241 patients with a new diagnosis of IDK (67% males, mean age 35 +/- 12 years), and 110 (46%) underwent arthroscopy. The remaining patients received conservative therapy and were not scheduled for arthroscopy within the period of observation. Using a priori established criteria, 10% of the arthroscopies could be considered diagnostic only (e.g., normal knee) and 27% were of doubtful efficacy from a therapeutic perspective (e.g., debridement alone). Many of these arthroscopies could have been avoided by performing a prior MRI. Using these findings, we conducted decision tree analyses of the use of MRI among patients requiring arthroscopy of the knee. A sensitivity analysis was performed to evaluate the various model assumptions. In general, MRI appeared to be a cost-effective diagnostic procedure for patients with IDK requiring arthroscopy of the knee, and there were cost savings associated with it in some of the models tested.

Adult↗
PubMed1999

Reducing arthroplasty costs via vendor contracts.

OBJECTIVE: To describe a method of reducing the costs of implants in hip and knee arthroplasty. DESIGN: Implant costs were compared before and after the implementation of a 2-year contract with implant vendors, providing increased volume for decreased implant cost. An additional 20% of arthroplasties could be done outside the contract for research or special purposes. SETTING: A regional health authority involving 2 acute care hospitals. METHOD: Costs were obtained for 942 hip and knee arthroplasties performed in 1993/94 and compared with costs of 1656 hip and knee arthroplasties performed in 1996/97. OUTCOME MEASURES: Implant cost and number of joint arthroplasty procedures performed. RESULTS: A 40% decrease in the cost per implant for primary knee arthroplasty and an 18% decrease in the cost per implant for primary hip arthroplasty were achieved. A rebate, calculated as a percentage of volume used, was received from the vendor to support general orthopedic research and education. A new contract for 3 years has recently been signed with 3 vendors designated as primary vendors for 80% of the volume. CONCLUSION: The vendor-contract economic strategy effectively reduced the cost of hip and knee arthroplasty and may be useful at other centres looking for cost reduction methods that maintain adequate patient care and support clinical research and education.

Arthroplasty, Replacement, Hip↗