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Biomedical subjects

P Demers

Publications and source records attributed to P Demers.

At least 19 recordsLinked to original sources

Effects of de-industrialization on unemployment, re-employment, and work conditions in a manufacturing workforce.

BACKGROUND: The purpose of this study was to investigate the impact of a 20-year process of de-industrialization in the British Columbia (BC) sawmill industry on labour force trajectories, unemployment history, and physical and psychosocial work conditions as these are important determinants of health in workforces. METHODS: The study is based on a sample of 1,885 respondents all of whom were sawmill workers in 1979, a year prior to commencement of de-industrialization and who were followed up and interviewed approximately 20 years later. RESULTS: Forty percent of workers, 64 years and under, were employed outside the sawmill sector at time of interview. Approximately one third of workers, aged 64 and under, experienced 25 months of more of unemployment during the study period. Only, 1.5% of workers were identified as a "hard core" group of long-term unemployed. Workers re-employed outside the sawmill sector experienced improved physical and psychosocial work conditions relative to those employed in sawmills during the study period. This benefit was greatest for workers originally in unskilled and semi-skilled jobs in sawmills. CONCLUSIONS: This study shows that future health studies should pay particular attention to long-term employees in manufacturing who may have gone through de-industrialization resulting in exposures to a combination of sustained job insecurity, cyclical unemployment, and adverse physical and psychosocial work conditions.

Adult↗

Coronary artery endothelial dysfunction after ischemia-reperfusion and acute untreated rejection in a canine heterotopic heart transplantation model.

BACKGROUND: Acute rejection is a common problem in heart transplantation and may contribute to the development of cardiac allograft vasculopathy. This study was designed to evaluate the mechanisms of coronary endothelial dysfunction associated with ischemia-reperfusion and acute untreated rejection. METHODS: Two groups of mongrel dogs (n=7 per group) underwent heterotopic cervical heart transplantation without immunosuppression. Allografts were harvested on posttransplant day 1 (group 1) and day 5 (group 2). A third group of unoperated dogs served as control (group 3). After harvesting, epicardial coronary arteries were studied in organ chamber for endothelium-dependent and independent reactivity. RESULTS: Group 1 displayed multifocal ischemic damage without any rejection while hearts from group 2 reached grade IV rejection. Immunohistochemical studies for von Willebrand factor showed expression on coronary endothelial cells in all animals with scattered areas of denudation in transplanted groups. Endothelium-dependent responses to acetylcholine, calcium ionophore A23147, and bradykinin were unaffected in groups 1 and 2. Endothelial relaxations to sodium fluoride (Gi-protein activator) was significantly reduced in group 1 and significantly increased in group 2 compared with control. Responses to serotonin and UK14304 (receptors linked to Gi-protein) were significantly increased in group 2. Responses to thrombin were decreased in both groups. Endothelium-independent responses were unaffected. CONCLUSIONS: In the canine model of heterotopic heart transplantation, the early (24 hr) endothelial dysfunction seen after transplantation is specific to the thrombin receptor and the Gi-protein signaling pathway. Acute untreated rejection did not modify the alteration in endothelial reactivity to thrombin but enhanced the sensibility of the Gi-protein signaling pathways.

Animals↗

Multivessel off-pump coronary artery bypass surgery in the elderly.

OBJECTIVE: Coronary artery bypass grafting in the elderly patient is associated with increased perioperative morbidity and mortality. The avoidance of cardiopulmonary bypass (CPB) in this population is potentially beneficial. We examined our initial experience with off-pump multivessel coronary artery revascularization in patients aged 70 years and older. METHODS: In a consecutive series of 300 off-pump coronary artery bypass (OPCAB) operations performed by a single surgeon between 1996 and 1999, 98 patients were aged 70 years and older. These patients were compared with a consecutive cohort of 497 patients aged 70 years and older operated on with CPB in the same institution from 1995 to 1996, period where OPCAB surgery was not performed in our institution. RESULTS: Patients in the beating heart group were older (75+/-4 vs. 74+/-3 years; P=0.001). Gender distribution and other preoperative risk factors were comparable for the two groups. On average, 3.0+/-0.8 and 2.8+/-0.7 grafts per patient were completed in the OPCAB and the CPB groups, respectively (P=0.007). Perioperative mortality rates (OPCAB group, 3.1%; CPB group, 3.6%), perioperative myocardial infarction (OPCAB, 2.0%; CPB, 5.1%) and neurologic events (OPCAB, 1.0%; CPB, 3.2%) were comparable for the two groups. The incidence of postoperative atrial fibrillation was lower in the OPCAB group (42 vs. 54%; P=0.05). The need for allogenic blood transfusions was significantly less in the OPCAB group (53 vs. 82%; P=0.001). CONCLUSIONS: In patients aged 70 years and older, multivessel OPCAB surgery is associated with lower rates of postoperative atrial fibrillation and reduced transfusion requirements. Multivessel OPCAB in the elderly patient is an acceptable alternative to procedures performed with CPB.

Age Factors↗

Outcome with high blood lactate levels during cardiopulmonary bypass in adult cardiac operation.

BACKGROUND: High blood lactate levels during cardiopulmonary bypass (CPB) are associated with tissue hypoperfusion and may contribute to postoperative complications or death. The objective of this study was to determine an association between blood lactate levels during CPB and perioperative morbidity and mortality. METHODS: We reviewed 1,376 patients who underwent cardiac operation with CPB. Patients with abnormal preoperative blood lactate levels were excluded (n = 101). Blood lactate concentration during CPB, clinical data, and perioperative events were recorded. RESULTS: Peak blood lactate levels of 4.0 mmol/L or higher during CPB were present in 227 patients (18.0%). Postoperative mortality was higher in this group than in the patients who had peak blood lactate levels of less than 4.0 mmol/L during CPB (11.0% versus 1.4%; p < 0.001, relative risk [RR] = 9.0). Postoperative hemodynamic instability occurred in 29.5% of patients with elevated levels of lactate during CPB compared with 10.9% of patients with lower lactate levels (p < 0.001, RR = 3.4). Overall, major postoperative complications occurred in 43.2% and 21.8% of patients in each group, respectively (p < 0.001, RR = 2.7). Logistic regression analysis revealed that peak blood lactate levels of 4.0 mmol/L or higher during CPB were strongly associated with postoperative mortality (p = 0.0001) and morbidity (p = 0.013). CONCLUSIONS: Blood lactate concentration of 4.0 mmol/L or higher during CPB identifies a subgroup of patients with increased risk of postoperative morbidity and mortality.

Adult↗

Downsizing and industrial restructuring in related to changes in psychosocial conditions of work in British Columbia sawmills.

OBJECTIVES: This paper investigates changes in the psychosocial and physical work conditions of the sawmill industry in British Columbia, Canada, over the past 35 years. METHODS: Shifts in work conditions were examined within the context of historical changes in sawmill labor demography and job taxonomy as the industry was both downsized and restructured, largely in response to an economic recession in the early 1980s. RESULTS AND CONCLUSIONS: Downsizing eliminated approximately 60% of the work force and 1/4 of sawmill job titles. Although all the job categories in restructured sawmills showed increased levels of control, the gradient in control across job categories was steeper in 1997 than in 1965; this change may have important health implications particularly for the unskilled workers in the restructured mills.

British Columbia↗

Early and long-term results of percutaneous transluminal angioplasty of the lower abdominal aorta.

PURPOSE: The purpose of this study was to determine the early and long-term results of percutaneous transluminal angioplasty (PTA) of atherosclerotic lower abdominal aorta stenosis. METHODS: This study was performed as a retrospective study. From 1980 to 1997, 46 patients with chronic lower limb ischemia with moderate to severe claudication as the result of isolated infrarenal disease or aortoiliac disease underwent PTA. All patients underwent angiography before and after angioplasty and Doppler ultrasound scan examination with ankle-brachial index determination. No stents were used. RESULTS: The technical success rate was 96% (44 of 46 cases). Thirty-eight patients (83%) immediately showed clinical, hemodynamic, and angiographic improvement. The initial success rate for patients with isolated infrarenal or bifurcation disease was 92%, whereas it was 71% for aortoiliac disease. Among the eight patients with no initial improvement, four had clinical deterioration and two required emergency surgical revascularization. There were no other complications. Fifty-six percent of the patient conditions (95% confidence interval [CI], 38% to 74%) remained clinically improved at the 5-year follow-up examination. Recurrence of symptoms was caused by femoropopliteal disease in most patients. The primary patency rate assumed with maintenance of hemodynamic improvements was 70% (95% CI, 52% to 88%) and 64% (95% CI, 44% to 84%) at 4 and 5 years of follow-up, respectively. The primary patency rate at 4 years for patients with isolated infrarenal or bifurcation disease was 83% (95% CI, 64% to 100%), whereas it was 55% for aortoiliac disease (95% CI, 30% to 80%; P =.06) The variables that were statistically predictive of patency failure were poor runoff (P =. 01) and presence of aortoiliac atherosclerotic disease (P =.04). CONCLUSION: Our results suggest that PTA is an excellent treatment for chronic arterial insufficiency of the lower extremities as the result of isolated atherosclerotic lower abdominal aortic occlusive lesions because of good long-term patency. Aortic PTA for those patients with iliac involvement or with poor runoff gives acceptable results but carries lower patency and clinical success rates.

Adult↗

Characterization of the natural history of cervical heterotopic heart transplantation with echocardiography.

BACKGROUND: Limitations of the dog model of orthotopic heart transplantation to study rejection include the need for extracorporeal circulation and transfusions. Heterotopic cervical heart transplantation may improve on these limitations. It is not known whether the natural history after heterotopic transplant is similar to that after orthotopic grafting. METHODS: Twenty-one dogs underwent cervical heterotopic heart transplantation. Serial echocardiographic studies were performed 1 to 3 hours after surgery, at 24 hours, 48 hours later, and immediately before killing (5 to 7 days). RESULTS: LV diastolic and systolic areas were elevated immediately after transplantation (4.95+/- 1.49 cm2 and 3.36+/-1.18 cm2 respectively) but decreased at 24 hours (3.93+/-1.20 cm2, p = 0.0003 and 2.44+/-0.96 cm2, p = 0.16). Thereafter, a progressive increase in LV diastolic and systolic areas was observed until sacrifice (5.53+/-2.20 cm2 and 4.59 +/-2.14 cm2, p < 0.001 vs 24 hours). LV fractional area shortening (FAS) and fractional volume change were depressed immediately after transplantation (28.2+/- 12.8% and 40.4+/-12.3%, respectively), but increased at 24 hours (35.7+/-10.0%,p = 0.11 and 50.3+/-4.0%,p = 0.02). FAS decreased at 48 hours to 19.6+/-11.1% (p = 0.01 vs 24 hours). The centractility indexes were markedly reduced before killing (FAS = 14.0+/-8.2% and LVEF = 18.4+/-1.3%, p < 0.0005 vs 24 hours). The thickness of the interventricular septum increased from 11.9+/-2.0 mm at baseline to 14.4+/-4.2 mm before sacrifice (p = 0.007). CONCLUSION: The evolution of dogs after heterotopic cervical heart transplant is comparable to that after the more standard orthotopic graft. Considering its multiple practical advantages including the easy echocardiographic follow-up, heterotopic transplantation may become a very practical model to use for the study of rejection after heart transplantation.

Animals↗

[Hypertrichosis and gingival hypertrophy regression in renal transplants following the substitution of cyclosporin by tacrolimus].

Gingival Hyperplasia (GH) and hypertrichosis (HT) are two sides effects associated with the usage of cyclosporine (CyA) but not with tacrolimus (FK 506). The aim of this study is to evaluate the efficacy and security of the conversion from CsA to FK 506 to treat those two complications. From August 1996 to May 1997, 15 patients (9 males, 6 females) aged from 23 to 63 years old (38 +/- 14, mean +/- SD) were switched from CsA to FK 506, 12 for GH, 2 for HT and one for combined presentation. FK 506 was first initiated at a dose of 0.15 mg/kg/day and then adjusted to a level target of 8 ng/ml. The conversion was done on an out patient basis at average 35 (5-83) months after transplantation. Patients were followed prospectively for 12 months. There was a significant reduction in GH in all patients within 3 months. Five out 13 patients had a complete resolution of GH within three months of conversion, 9/12 within 6 months and all by 12 months. HT resolved completely within 6 months. No rejection episode occurred and the serum creatinin remain stable over one year post conversion. Conversion from CsA to FK 506 is thus a safe and valid option to treat CsA induced GH and HT.

Adult↗

Endotoxin exposure among softwood lumber mill workers in the Canadian province of British Columbia.

An increased prevalence of respiratory problems among softwood lumber mill workers has been observed in a number of studies. These workers are potentially exposed to a variety of respiratory hazards including wood dust, abietic or other resin acids, monoterpenes, and fungi, as well as endotoxins. The objectives of this study were to determine if lumber mill workers were exposed to hazardous levels of airborne endotoxin and to identify the factors contributing to high exposures. Personal endotoxin samples (n = 216) were collected in four lumber mills in the Canadian province of British Columbia. The mean personal exposure concentration was 2.09 ng/m.(3) and 9% of the samples were above 5 ng/m.(3). Factors related to the personal endotoxin exposure were type of job, use of compressed air, the percentage of time spent in a booth or cab during a shift, and dust concentration. Log storage practices were also suspected of playing a role. The levels of exposure observed in this study were low compared to the levels reported for populations with respiratory problems attributed to endotoxins.

Air Microbiology↗

Fertility among a cohort of male sawmill workers exposed to chlorophenate fungicides.

The purpose of this study was to determine whether exposure to chlorophenate fungicides and their dioxin contaminants is associated with male infertility among sawmill workers. The study was conducted using fertility data compiled from 26,487 sawmill workers in 14 British Columbian sawmills. Our analysis was restricted to workers who had been employed for at least 1 continuous year between 1950 and 1985 and to live-births born at least 1 year after the initiation of employment in the period 1955-1988. We assessed fertility trends by internal comparison using Mantel-Haenszel rate ratios and by calculating standardized fertility ratios using an external and an internal reference population. We identified 19,684 births in the study period. Initially, both external and internal analyses showed that sawmill workers from mills using chlorophenates had lower fertility than workers employed in mills not using chlorophenates. After controlling for time since first hire, however, we found no inverse relation between cumulative exposure to chlorophenate fungicides and fertility. Based on the results of our study, there is little evidence for a reduction in fertility among chlorophenate-exposed sawmill workers in British Columbia. The analyses indicate the importance of time since hire as a potentially strong confounder in this type of investigation.

Adult↗

[Comparison of endothelial reactivity of infrarenal and suprarenal aortic segments in rodents].

OBJECT: Human infrarenal aorta is prone to develop atherosclerotic lesions. Infrarenal aortic blood flow depends on lower limb muscular activity. Blood flow variations cause shear stress variations known to influence endothelial reactivity. The purpose of this study is to compare vascular reactivity of the suprarenal and infrarenal aorta. MATERIAL AND METHODS: Endothelium-dependent relaxation to acetylcholine (ACH) and calcium ionophore (Cal), and endothelium-independent relaxation to sodium nitroprussiate (SNP) in 3 aortic segments (thoracic, abdominal suprarenal and infrarenal) harvested from Sprague-Dawley rats (n = 12) were studied in organ chambers. RESULTS: Endothelium-dependent relaxations to ACH were similar for the 3 aortic segments. However, infrarenal aorta endothelial response to Cal was decreased compared to other segments whereas response to SNP was enhanced. Contractility to vasoconstrictor agonist (phenylephrine and KCl) was diminished compared to the suprarenal segments. CONCLUSION: Endothelial reactivity is not homogeneous throughout the rat aorta. Endothelial reactivity to Cal seems decreased in the infrarenal aorta which suggests a diminished nitric oxide synthase activity. The increased sensitivity of the infrarenal aorta to nitric oxide donor such as SNP suggests a compensatory mechanism.

Acetylcholine↗

[The vasoconstrictor effect of cyclosporine on the pulmonary vein is mediated by its vehicle: the cremophor].

OBJECT: Cyclosporin A (CyA) induced vasoconstriction and impaired relaxation to agonists has been related in some models to its vehicle: the cremophor (CRE). There is no data concerning the effect of CyA and its vehicle CRE on the pulmonary veins. Therefore, the present study was designed to characterize the effect of CyA and CRE on isolated pulmonary veins. MATERIAL AND METHODS: Third-order canine pulmonary veins (n = 6) were suspended in organ chambers for measurement of isometric force. Segments were exposed to cumulative doses (10(-9) to 10(-4) M) of CyA in its vehicle CRE, and to CRE alone. RESULTS: CyA induced an ehdothelium-independent vaasoconstriction similar to CRE, maximal constriction (Emax) were: 1.8 +/- 0.3 g versus 2.1 +/- 0.4 g respectively (p = NS). This vasoconstriction observed with CRE was not affected by indomethacine (a cyclooxygenase inhibitor), and by pinane thromboxane (a thromboxane antagonist). However, the vasoconstriction was decreased by diltiazem (10(-5) M), a calcium channel blocker, Emax were: 2.1 +/- 0.4 g and 0.8 +/- 0.04 g respectively for CRE and CRE with diltiazem (p < 0.05). CONCLUSION: CyA vehicle CRE induces an endothelium-independent vasoconstriction in isolated third order pulmonary veins in the dog. This vasoconstriction is not related to a cyclooxygenase product, but is partially mediated by a calcium channel activation in vascular smooth muscle.

Animals↗

Management of silicone-induced cataract in AIDS patients treated for viral retinitis-associated retinal detachment.

BACKGROUND AND OBJECTIVE: To evaluate the outcome of cataract surgery for patients with acquired immunodeficiency syndrome (AIDS) who underwent vitrectomy and silicone tamponade for viral retinitis-associated retinal detachment. PATIENTS AND METHODS: The authors retrospectively reviewed the data of five AIDS patients (five eyes) who had cataract within a mean period of 4 months following vitrectomy and silicone oil tamponade for viral retinitis-associated retinal detachment. Phacoemulsification and implantation of a poly-methylmethacrylate posterior chamber intraocular lens were performed. The mean postoperative follow-up was 3 months. RESULTS: Neither silicone oil loss nor retinal redetachment were reported postoperatively. Visual acuity improved in two eyes and remained unchanged in one eye. Total blindness occurred in two eyes. CONCLUSION: Although cataract surgery in these eyes is a relative easy procedure and does not interfere with the retinal status, visual outcome remains poor because of possible postoperative optic atrophy.

AIDS-Related Opportunistic Infections↗

[Comparison of hemodynamic and ventilatory effects of pneumoperitoneum using carbon dioxide or abdominal suspension during laparoscopic cholecystectomy].

This study compares the cardio-respiratory effects of CO2 pneumoperitoneum to those of abdominal suspension (or laparolift) in laparoscopic cholecystectomy. Between september 1993 et may 1995, 31 patients participated in this non-randomized prospective trial. They consisted of 9 males et 22 females, with a mean age of 47.0 +/- 14 years. Sixteen patients were included in the CO2 group and 15 in the laparolift group. Both groups were comparable for age and gender. All patients were submitted to the same anaesthetic protocol. Repeated measurements of the respiratory and cardiovascular function were made during the intervention. End tidal CO2, minute ventilation, peak inspiratory pressure showed superior elevations in the CO2 group. And for the hemodynamic parameters, only the mean arterial pressure and cardiac frequency differed between the two groups, other hemodynamic parameters including left ventricular ejection fraction were comparable. Also, postoperatory hospital stay, OR time, per and postoperatory complications were comparable. With its stable hemodynamic and ventilatory pattern, abdominal suspension can constitute a safe and secure alternative to CO2 pneumoperitoneum in patients with respiratory dysfunction.

Adult↗

Translation of clinical and neuropsychological instruments into French: the CERAD experience.

The increasing number of international and epidemiological studies of Alzheimer's disease points to the need for linguistically equivalent translations of measures for identifying the presence, types, and severity of dementia in cross-cultural populations. In translating the CERAD (Consortium to Establish a Registry for Alzheimer's Disease) neuropsychological instruments into French, several linguistic issues have emerged such as semantic, phonetic, and word-frequency equivalences. In verbal memory tests, these problems, though minor in appearance, can be major pitfalls in studies comparing cognitive function in populations differing in language. Description of the translation procedure and examples of problems encountered are presented, with measures taken to resolve them.

Aged↗

Neuropsychological performance among agricultural pesticide applicators.

To assess the potential effects on neuropsychiatric performance of chronic occupational exposure to organophosphate insecticides, we performed a prospective longitudinal study of a cohort of apple orchard pesticide applicators and a comparison cohort of beef slaughter-house workers. The study group consisted of 49 applicators and 40 comparison subjects who completed both an initial evaluation (preseason) prior to the onset of the approximately 6-month pesticide spraying season and a follow-up evaluation (postseason) about 1 month following the end of spraying season. The applicator cohort had a greater number (n = 22, 45%) of individuals who identified primary preference for Spanish-language testing than did the comparison cohort (n = 5, 13%). Stratification by language preference revealed no significant differences in background characteristics between the two cohorts, except for fewer years of education in the Spanish-language preference applicators versus control subgroups (5.0 +/- 3.1 vs 7.8 +/- 3.7 years, respectively). After controlling for language preference, there were no statistically significant differences between the applicators and control cohorts on neuropsychological subtests of the computerized test battery. Preseason baseline performance on individual tests was a significant predictor of postseason test performance. After controlling for baseline performance, the only statistically significant exposure related across-season changes in neuropsychological performance was for one subtest (Symbol Digit Substitution) and was confined to the Spanish language preference subgroups, with worse adjusted postseason performance among applicators versus controls (P = 0.001). This study found no clear evidence of clinically significant decrements in neuropsychological performance following one 6-month season of pesticide exposure in a cohort of applicators who were felt to have generally low, intermittent, and well-controlled organophosphate exposures.

Adult↗