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Biomedical subjects

L Roy

Publications and source records attributed to L Roy.

At least 55 records · Page 3Linked to original sources
PubMed1997

Radiation safety in the cardiac catheterization laboratory.

Over the years, permissible radiation exposure of operators working with x-ray equipment has become progressively reduced. The number of cardiac catheterizations and related interventional procedures has increased and the procedures have become more prolonged. The patient receives relatively infrequent primary radiation while the operator receives frequent but mainly secondary radiation. The operator uses protective barriers, correct positioning of the patient and careful techniques to reduce radiation exposure. The effects of radiation are cumulative and permanent. They may be stochastic or nonstochastic, and somatic and/or genetic, and onset may be delayed for many years. To minimize exposure of patient and operator, cardiologists need a better understanding of radiation physics and of cardiac x-ray equipment. Technical breakthroughs such as digital imaging, pulse fluoroscopy, reduction of frame rates from 60 or 30 frames/s to 15 frames/s, and progression to the filmless laboratory will substantially reduce radiation. This review discusses current cardiac x-ray equipment, possible future developments, radiation, and techniques for reducing radiation and improving safety in the cardiac catheterization laboratory.

Cardiac Catheterization↗
PubMed1996

Platelet membrane receptor glycoprotein IIb/IIIa antagonism in unstable angina. The Canadian Lamifiban Study.

BACKGROUND: Ligand binding to the platelet membrane receptor glycoprotein (GP) IIb/IIIa, the final and obligatory step to platelet aggregation, can now be inhibited by pharmacological agents. This study was designed to evaluate the potential of lamifiban, a novel nonpeptide antagonist of GP IIb/IIIa, for the management of unstable angina. METHODS AND RESULTS: In a prospective, dose-ranging, double-blind study, 365 patients with unstable angina were randomized to an infusion of 1, 2, 4, or 5 micrograms/min of lamifiban or of placebo. Treatment was administered for 72 to 120 hours. Outcome events were measured during the infusion period and after 1 month. Concomitant aspirin was administered to all patients and heparin to 28% of patients. Lamifiban, all doses combined, reduced the risk of death, nonfatal myocardial infarction, or the need for an urgent revascularization during the infusion period from 8.1% to 3.3% (P = .04). The rates were 2.5%, 4.9%, 3.3%, and 2.4% with increasing doses. At 1 month, death or nonfatal infarction occurred in 8.1% of patients with placebo and in 2.5% of patients with the two high doses (P = .03). The highest dose of lamifiban additionally prevented the need for an urgent intervention. Lamifiban dose-dependently inhibited platelet aggregation. Bleeding times were significantly prolonged with platelet inhibition of > 80%. Major (but neither life-threatening nor intracranial) bleedings occurred in 0.8% of patients with placebo and 2.9% with lamifiban. CONCLUSIONS: The nonpeptide GP IIb/IIIa antagonist lamifiban protected patients with unstable angina from severe ischemic events during a 3- to 5-day infusion and reduced the incidence of death and infarction at 1 month, suggesting considerable promise for this new therapeutic approach.

Acetates↗
PubMed1996

Pressure support improves efficiency of spontaneous breathing during inhalation anesthesia.

STUDY OBJECTIVE: To determine if reducing respiratory muscle load or increasing tidal volume (VT) with pressure support (PS) would improve ventilatory efficiency by reducing respiratory rate (RR) and resting PaCO2. DESIGN: Prospective, and patient-controlled, with randomized treatment crossover. SETTING: University cancer center and research institute. PATIENTS: ASA status I and II patients scheduled to undergo inhalation anesthesia for operations in which neuromuscular relaxation is undesirable. INTERVENTIONS: Propofol and succinylcholine were used to induce anesthesia and facilitate tracheal intubation. General anesthesia was maintained with desflurane, nitrous oxide, and oxygen. Patients breathed spontaneously at atmospheric pressure for 15 minutes and then randomly received alternate 15-minute trials of PS adjusted to provide either 5 cmH2O or a level titrated to produce VT of 8 ml/kg body weight. Then patients breathed spontaneously at atmospheric pressure for 15 minutes. MEASUREMENTS AND MAIN RESULTS: In 20 patients aged 52 +/- 11 years and weighing 72 +/- 18 kg, airway gas flow and pressure, esophageal pressure, arterial blood gas tensions and pH, and mean arterial pressure (MAP) were measured. Heart rate (HR), VT, RR, minute ventilation (VE), carbon dioxide production (VCO2), ratio of dead space to VT (VD/VT), and inspiratory work of breathing (WI) were calculated. End-tidal desflurane (6.7 +/- 0.4%), VCO2 (142 +/- 39 ml/min), HR, and MAP were unchanged throughout the study. WI, RR, VE, VD/VT, and PaCO2 were reduced significantly when PS was titrated to produce a VT of 8 ml/kg and spontaneous breathing before and after PS trials (p < 0.05). CONCLUSIONS: PS titrated to produce a near normal VT improves the efficiency of spontaneous breathing by lowering RR and PaCO2 while preserving hemodynamic homeostasis in patients undergoing inhalation anesthesia. Lesser PS levels will unload the respiratory muscles, but have no effect on RR or PaCO2.

Anesthesia, Inhalation↗
PubMed1996

Changes in plasma endothelin-1 and Big endothelin-1 induced by transjugular intrahepatic portosystemic shunts in patients with cirrhosis and refractory ascites.

BACKGROUND/AIMS: Endothelin-1 (ET-1) is a potent vasoconstrictor that may be involved in the pathogenesis of splanchnic and renal hemodynamic changes associated with portal hypertension. The aim of this study was to measure the concentration of ET-1 and of its precursor Big endothelin-1 (Big ET-1) in the systemic circulation as well as in the splanchnic and renal venous beds and to evaluate changes after the relief of portal hypertension following transjugular intrahepatic portosystemic shunt placement. METHODS: Plasma concentrations of ET-1 and of Big ET-1 were measured in the vena cava, renal vein, hepatic vein and portal vein in ten patients with cirrhosis and refractory ascites before and 1-2 months after transjugular intrahepatic portosystemic shunt. The porto-caval gradient, creatinine clearance, plasma aldosterone and renin activity, as well as daily urinary sodium excretion were measured at the same time. RESULTS: The plasma concentration of ET-1 and Big ET-1, respectively, in peripheral blood of normal volunteers were 0.28 +/- 03 and 3.95 +/- 0.34 pg/ml; the concentrations of both peptides were higher in patients with cirrhosis, both in vena cava (0.61 +/- 0.14 and 10.01 +/- 1.47 pg/ml), hepatic vein (0.62 +/- 0.13 and 13.93 +/- 1.77 pg/ml), portal vein (1.21 +/- 0.12 and 17.84 +/- 1.98 pg/ml) and renal vein (0.76 +/- 0.12 and 14.21 +/- 1.55 pg/ml). Moreover ET-1 and Big ET-1 concentrations were more elevated in the portal vein than in the vena cava (+98% and +70%) and slightly higher in the renal vein as compared to the vena cava (+25% and +42%). After transjugular intrahepatic portosystemic shunt, a rise in creatinine clearance and urinary sodium excretion (+49%; and +53%) was observed together with a marked reduction in plasma aldosterone and renin activity (-59% and -49%). ET-1 and Big ET-1 concentrations remained unchanged in the vena cava whereas a significant reduction of ET-1 and Big ET-1 occurred both in the portal vein (-43% and -44%) and in the renal vein (-53% and -29%). Portal vein and renal vein concentrations of both peptides became similar to vena cava levels. CONCLUSIONS: Splanchnic and renal hemodynamic changes occurring in patients with cirrhosis and refractory ascites could be related to the production of ET-1 by splanchnic and renal vascular beds. This was abolished by transjugular intrahepatic portosystemic shunt, which could explain the exacerbation of systemic vasodilation and the improvement in renal perfusion observed after the procedure.

Aged↗
PubMed1996

Comparison between fluorescence in situ hybridization and conventional cytogenetics for dicentric scoring: a first-step validation for the use of FISH in biological dosimetry.

In this study the suitability of fluorescence in situ hybridization (FISH) for dicentric detection using a commercially available alpha-satellite probe (Oncor) to label centromeres was compared with the conventional technique for the detection of unstable aberrations. A standard FISH protocol was applied for centromere labelling. Dose-response curves using blood samples irradiated in vitro with gamma-rays (60Co) at a dose-rate of 0.1 Gy/min were established using both techniques and compared. No statistical difference was observed between either method. The FISH technique thus allows a correct detection of unstable aberrations when an alpha-satellite DNA probe is used.

Centromere↗
PubMed1996

Minimal change glomerulonephritis in a 90-year-old patient: what is the ideal approach?

We report the case of a 90-year-old lady who presented with full-blown nephrotic syndrome. Percutaneous renal biopsy allowed us to confirm the diagnosis of minimal change glomerulopathy; she entered a 2-year period of remission after a 6-month course of prednisone (starting dose 1.5 mg/kg). The patient sustained minor effects of both renal biopsy and corticotherapy. Percutaneous renal biopsy is justified in the very elderly because the risk of mortality and morbidity related to corticotherapy outweigh the risk related to percutaneous renal biopsy, providing high-risk patients are excluded, such as amyloidosis or abnormal coagulation or uncontrolled arterial hypertension.

Aged↗
PubMed1996

Accumulation of a non-(1-84) molecular form of parathyroid hormone (PTH) detected by intact PTH assay in renal failure: importance in the interpretation of PTH values.

A molecular form of PTH different from PTH-(1-84) and present in normal serum is recognized by two-site intact (I-) PTH assays; it responds to Ca2+ changes in the same way that PTH carboxyl-terminal fragments do. To evaluate the impact of this finding, we have compared basal, stimulated, and nonsuppressible I-PTH values in 14 normal subjects and 15 renal failure patients, subdivided into 8 patients with low (< 12 pmol/L; LBI) and 7 with high (> 12 pmol/L; HBI) basal I-PTH. Samples obtained under various calcemic conditions in these 3 groups were further fractionated by high performance liquid chromatography (HPLC) and assayed for I-PTH, and the various peaks observed were quantitated by planimetry. Differences among the 3 groups were reinterpreted knowing the exact composition of I-PTH. Basal I-PTH was greatly increased in HBI (mean +/- SD, 44.1 +/- 38.6 pmol/L) compared to that in normal subjects (2.5 +/- 0.8 pmol/L; P < 0.001) or LBI (6.1 +/- 2.4 pmol/L; P < 0.001); the difference was less in these last 2 groups (P < 0.01). Similar differences were observed for stimulated and nonsuppressible I-PTH, except for stimulated I-PTH, which was similar in normal and LBI subjects. Two I-PTH HPLC molecular forms accounted for I-PTH immunoreactivity in the 3 groups. In normal subjects, PTH-(1-84) accounted for 74.9 +/- 4.3%, 79.0 +/- 3.0%, and 87.2 +/- 1.0% of I-PTH in hyper-, normo-, and hypocalcemia, respectively, but only for 44.6 +/- 2.5%, 50.5 +/- 0.7%, and 63.6 +/- 0.1% in renal failure patients, with similar results in HBI and LBI. The accumulation of a non-(1-84) PTH peak accounted for the difference between normal subjects and renal failure patients. When basal, stimulated, and nonsuppressible I-PTH values were separated into their 2 components, prior differences between HBI and LBI or normal subjects remained unchanged because of very high I-PTH values in HBI, but differences between normal and LBI subjects were entirely explained by the accumulation of the non-(1-84) PTH peak [basal, 3.0 +/- 1.2 vs. 0.5 +/- 0.2 pmol/L (P < 0.001); stimulated, 6.8 +/- 2.3 vs. 2.3 +/- 1.0 pmol/L (P < 0.001); nonsuppressible, 1.3 +/- 0.7 vs. 0.2 +/- 0.08 pmol/L (P < 0.001)]; PTH-(1-84) values were similar (basal, 3.1 +/- 1.2 vs. 2.0 +/- 0.6 pmol/L; stimulated, 12.0 +/- 3.9 vs. 15.5 +/- 6.6 pmol/L; nonsuppressible, 1.1 +/- 0.6 vs. 0.52 +/- 0.22 pmol/L). Thus, a non-(1-84) PTH molecular form detected by two-site I-PTH assays accumulates in renal failure and accounts for a larger proportion of I-PTH than that in normal subjects. Levels of I-PTH 1.57 times higher than those in normocalcemic subjects are thus required in renal failure to achieve similar PTH-(1-84) concentrations. The composition of I-PTH is also identical in all hemodialyzed patients.

Aged↗
PubMed1996

[Indications for the use of somatostatin and octreotide in digestive pathology].

The authors report their experience about the use of somatostatin (SST-14) (47 cases) and its analog octreotide (15 cases) in gastrointestinal diseases. On the basis of own clinical data and literature review, at present they think useful SST-14 employ in the upper gastrointestinal tract bleeding and acute pancreatitis. Out of the emergency, they consider favourable the use of octreotide, above all because of the easy subcutaneous administration's route.

Adult↗
PubMed1995

Maximizing the benefits of thrombolytic therapy for acute myocardial infarction.

Thrombolytic therapy is a huge advance in the management of acute myocardial infarction (AMI). The results of large clinical trials over the past 9 years have unequivocally demonstrated its benefit: of every 1000 patients treated 30 will be saved, at a cost of two cases of nonfatal cerebral hemorrhage and seven of noncerebral major hemorrhage. The concurrent use of acetylsalicylic acid increases the benefit of thrombolytic therapy. Sales figures for thrombolytic agents indicate that their use in Canada is less than optimal and lags behind that in several European countries. Major educational efforts are needed to promote awareness of the efficacy of thrombolytic therapy and of optimal approaches for maximizing its potential benefit for patients with AMI.

Clinical Trials as Topic↗
PubMed1995

Epidural blood patch in a seven-year-old child.

We present an unusual case of postoperative headache in a child after an epidural block. A seven-year-old girl (ASA 1) was scheduled to undergo a urological procedure under general anaesthesia combined with an epidural technique for intra- and postoperative analgesia. Although there was no evidence of dural puncture when the block was performed, the patient developed a headache postoperatively. The headache, which was accompanied by neck pain, appeared in the sitting or standing position and was relieved by decubitus. According to the mother, her child had never complained of those symptoms in the past. After independent evaluation by an anaesthetist and a neurologist, a postdural puncture headache (PDPH) was considered the most likely diagnosis. As oral analgesics failed to provide relief, and epidural blood patch (EBP) using 10 ml autologous blood was performed under light sedation. This was followed by resolution of the symptoms. Epidural injections of opioids and local anaesthetics are becoming increasingly popular for pain management in children. This implies that there may be an increasing number of unintentional dural punctures that may result in more PDPHs in children. Epidural blood patches are effective in treating PDPHs in adults but their use has been reported very rarely in children. Resolution of the patient's symptoms following EBP supported the diagnosis while illustrating that EBP can be useful in the treatment of PDPH in children.

Anesthesia, Epidural↗
PubMed1995

[Demography perspectives and forecasts of the demand for electricity].

"Demographic perspectives form an integral part in the development of electric load forecasts. These forecasts in turn are used to justify the addition and repair of generating facilities that will supply power in the coming decades. The goal of this article is to present how demographic perspectives are incorporated into the electric load forecasting in Quebec. The first part presents the methods, hypotheses and results of population and household projections used by Hydro-Quebec in updating its latest development plan. The second section demonstrates applications of such demographic projections for forecasting the electric load, with a focus on the residential sector." (SUMMARY IN ENG AND SPA)

Americas↗
PubMed1995

Improvement of hepatorenal syndrome by transjugular intrahepatic portosystemic shunt.

Hepatorenal syndrome (HRS) is a functional renal failure occurring in advanced liver cirrhosis with ascites. It is due to renal cortical vasoconstriction resulting from complex hemodynamic disturbances related to cirrhosis and portal hypertension. There is no consistently effective therapy except for liver transplantation. We report a case of severe HRS in a patient with advanced liver cirrhosis and portal hypertension. Three sessions of hemodialysis were performed because of severe renal failure (serum urea 83 mg/dl, serum creatinine 6 mg/dl). Creation of an intrahepatic portosystemic shunt reduced the portocaval gradient from 18 to 7 mm Hg. Spectacular improvement of the renal function was observed soon after the procedure, with spontaneous recovery of diuresis and a return of serum urea and creatinine to baseline values. The patient unfortunately died 2 months later from adult respiratory distress syndrome post emergency surgery for a massive bleed related to a duodenal ulcer. Throughout this episode, the renal function remained stable. The postmortem examination showed histologically normal kidneys. We conclude that the intrahepatic portosystemic shunt can improve renal function in cirrhotic patients with HRS; it could be used in patients awaiting liver transplantation to reverse preoperative renal failure.

Hepatorenal Syndrome↗
PubMed1993

Induction of metaphase arrest in cleaving Xenopus embryos by MAP kinase.

The natural arrest of vertebrate unfertilized eggs in second meiotic metaphase results from the activity of cytostatic factor (CSF). The product of the c-mos(xe) proto-oncogene is thought to be a component of CSF and can induce metaphase arrest when injected into blastomeres of two-cell embryos. The c-Mos(xe) protein can directly activate the mitogen-activated protein kinase kinase (MAP kinase kinase) in vitro, leading to activation of MAP kinase. MAP kinase and c-Mos(xe) are active in unfertilized eggs and are rapidly inactivated after fertilization. Microinjection of thiophosphorylated MAP kinase into one blastomere of a two-cell embryo induced metaphase arrest similar to that induced by c-Mos(xe). However, only arrest with c-Mos(xe) was associated with activation of endogenous MAP kinase. These results indicate that active MAP kinase is a component of CSF in Xenopus and suggest that the CSF activity of c-Mos(xe) is mediated by MAP kinase.

Amino Acid Sequence↗
PubMed1993

A translation-based generation effect in bilingual recall and recognition.

Two experiments were performed with incidental study procedures in which generation effects were observed for relatively balanced French-English bilingual subjects on measures of both free recall and recognition. Experiment 1 used a within-subject design, and Experiment 2 used a between-subject design. In both experiments, reading translations and reading same-language repetitions generally resulted in similar amounts of retention. Experiment 2 and Experiment 3 also showed that the generation effect was abolished under intentional study procedures because of an enhancement of reading-based retention. The results suggested that previous failures to obtain a translation-based generation effect may have been due to the use of intentional study procedures. The pattern of effects was explained in terms of a single-code model of bilingual linguistic representation and an individual-item processing interpretation of the generation effect.

Adult↗
PubMed1993

Measurement errors in standard visual analysis of coronary angiograms: consequences on clinical trials.

OBJECTIVE: The usual assessment of coronary angiograms by standard visual analysis was compared with the assessment by quantitative computer analysis to provide evidence of the consequences of measurement errors attributable to visual assessment in the evaluation of coronary stenoses in clinical trials. METHODS: Angiograms obtained in 151 patients enrolled in a double-blind randomized controlled trial assessing the effect of fish oil supplementation on restenosis were evaluated by both visual and quantitative methods. Proportions of patients with unsuccessful angioplasty and proportions of patients with restenosis according to visual and quantitative methods were compared by standard statistical methods. RESULTS: Of the 151 patients who were considered successfully dilated by visual interpretation, 32 were not considered successfully dilated by quantitative analysis. With quantitative computer analysis, evaluation of restenosis on the 119 successfully dilated patients documented a protective effect of fish oil against restenosis (30.5% of treated patients versus 48.3% of control patients, P < 0.05). Visual evaluation of restenosis six months after angioplasty misclassified 10% of patients in each treatment group and failed to demonstrate a protective effect of fish oil against restenosis. CONCLUSIONS: Misclassification by visual assessment of both success and restenosis in the present trial led to underestimating the true effect of fish oil in the prevention of restenosis. Accurate and objective methods, such as quantitative computer analysis, are thus required for evaluating the effects of interventions on coronary arteries.

Angioplasty, Balloon, Coronary↗