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Biomedical subjects

J Fortin

Publications and source records attributed to J Fortin.

At least 19 recordsLinked to original sources
PubMed1999

beta-2 Adrenergic receptor variants affect resting blood pressure and agonist-induced vasodilation in young adult Caucasians.

Recent evidence suggests that the prodownregulatory Gly16 allele of the beta-2 adrenergic receptor (beta-2 AR) is associated with essential hypertension in African Caribbeans. To further investigate the effect of the glycine (Gly)16 and arginine (Arg)16 beta-2 AR variants on hemodynamics, we investigated the agonist-mediated in vivo vasodilation in normotensive Austrian Caucasians and analyzed the results with respect to the Gly16/Arg16 polymorphism. Fifty-seven normotensive men, 20 to 32 years of age with body mass index of 18.7 to 29.9 kg/m2, were genotyped for the Arg16/Gly16 beta-2 AR alleles. All 15 Gly16/Gly16 subjects, all 12 Arg16/Arg/16 subjects, and 27 of 30 heterozygous subjects underwent hemodynamic measurements while supine after an overnight fast. The observers were unaware of the subjects' genotypes. The subjects received a graded infusion of the selective beta-2 AR agonist salbutamol (0.07, 0.14, and 0.21 microgram/kg per minute, respectively), each dose over 8 minutes. Stroke volume and blood pressure were determined continuously by means of impedance cardiography and oscillometry, respectively. The last 4 minutes of each infusion were evaluated statistically. Basal mean blood pressure was higher in the Gly16/Gly16 subjects compared with Arg16/Arg16 subjects (mean+/-SD: 81.6+/-6.14 versus 75.2+/-4.93 mm Hg, P<0.01). Homozygous Gly16 subjects showed a significantly decreased vasodilation during the first dose of salbutamol infusion compared with Arg16/Arg16 subjects (Deltatotal peripheral resistance index -17.9+/-14.4 versus -30. 6+/-8.3%, P<0.01) despite increased sympathetic counterregulation in the Arg16/Arg16 group (Deltaheart rate +16.9+/-7.0% versus +8.6+/-7. 0%, P<0.01; Deltacardiac index +39.5+/-18.5% versus 21.4+/-18.8%, P<0.05). Our results provide additional evidence that the Gly16/Arg16 alleles of the beta-2 AR are intimately related to blood pressure regulation and deserve further studies in the pathogenesis of essential hypertension.

Adrenergic beta-Agonists↗
PubMed1998

A software package for non-invasive, real-time beat-to-beat monitoring of stroke volume, blood pressure, total peripheral resistance and for assessment of autonomic function.

The goal of the present study was to develop and evaluate algorithms for non-invasive, real-time, beat-to-beat monitoring of stroke index (SI), blood pressure (BP) and total peripheral resistance index (TPRI) which has a menu-driven interface, suitable for routine use by unskilled staff. In addition, it was our aim to include a meta-analysis for the evaluation of autonomic function derived from the above haemodynamic data. This includes spectral analysis of heart rate (HR), BP, SI and TPRI and the automatic calculation of baroreceptor reflex sensitivity. Impedance cardiography was used for beat-to-beat SI determination, Finapres corrected by an oscillometric blood pressure measurement (Dinamap) on the upper arm for beat-to-beat BP measurement. We demonstrate noise free recordings during physiological (head up tilt) and pharmacological intervention (alpha 1-, beta 2-adrenoreceptor agonists, insulin induced hypoglycemia). The newly developed software should prove valuable for physiological, pharmacological and clinical studies.

Adult↗
PubMed1995

The prevalence and clinical features of internal disc disruption in patients with chronic low back pain.

STUDY DESIGN: This was a cross-sectional analytic study of patients with chronic low back pain. OBJECTIVE: To investigate whether the criteria for internal disc disruption, as adopted by the International Association for the Study of Pain, could be satisfied in patients with chronic low back pain and to test whether there were any conventional clinical features that could identify this condition. SUMMARY OF BACKGROUND DATA: Internal disc disruption has been postulated as an important cause of low back pain. To diagnose this condition, the International Association for the Study of Pain taxonomy requires that pain be reproduced on provocation discography and that computed tomography discography reveal internal disc disruption, provided that as a control, stimulation of at least one other disc fails to reproduce pain. METHODS: Ninety-two consecutive patients with chronic low back pain and no history of previous lumbar surgery were studied. Each patient underwent a standard physical examination. Computed tomography discography was performed at a minimum of two levels. RESULTS: The diagnostic criteria for internal disc disruption were fully satisfied in 39% of patients, most commonly at L5-S1 and L4-L5. None of the clinical tests used could differentiate between those patients with internal disc disruption and other patients. CONCLUSIONS: A diagnosis of internal disc disruption can be made in a significant proportion of patients with chronic low back pain, but no conventional clinical test can discriminate patients with internal disc disruption from patients with other conditions.

Adult↗
PubMed1994

Clinical features of patients with pain stemming from the lumbar zygapophysial joints. Is the lumbar facet syndrome a clinical entity?

STUDY DESIGN: This study is a prospective cross-sectional analytic study. OBJECTIVES: The authors determined the prevalence and clinical features of patients with pain stemming from the lumbar zygapophysial joints. SUMMARY OF BACKGROUND DATA: Previous studies have demonstrated a wide range of prevalence for zygapophysial joint pain and conflicting results with regard to clinical signs. METHODS: One hundred and seventy-six consecutive patients with chronic low back pain were investigated with a series of screening zygapophysial joint blocks using lignocaine and confirmatory blocks using bupivacaine. RESULTS: Forty-seven percent of patients had a definite or greater response to the screening injection at one or more levels but only 15% had a 50% or greater response to a confirmatory block. Response to zygapophysial joint injection was not associated with any single clinical feature or set of clinical features. CONCLUSIONS: The zygapophysial joint is an important source of pain but the existence of a "facet syndrome" must be questioned.

Adult↗
PubMed1994

The relative contributions of the disc and zygapophyseal joint in chronic low back pain.

STUDY DESIGN: A prospective cross-sectional analytic approach was taken. OBJECTIVES: This study sought to determine the relative contribution of the disc and the zygapophyseal joint as a pain source in patients with chronic low back pain. SUMMARY OF BACKGROUND DATA: Previous studies have employed either zygapophyseal joint blocks or discography, but in no studies have both procedures been performed. METHODS: Ninety-two consecutive patients with chronic low back pain were studied using both discography and blocks of the zygapophyseal joints. RESULTS: Thirty-six patients (39%) had at least one positive discogram as defined by exact pain reproduction, an abnormal image, and a negative control. Eight patients responded to both a screening zygapophyseal joint block using lignocaine and a confirmatory block using bupivacaine. Only three patients had both a positive discogram and a symptomatic zygapophyseal joint. CONCLUSIONS: In patients with chronic low back pain, the combination of discogenic pain and zygapophyseal joint pain is uncommon.

Adult↗
PubMed1994

The false-positive rate of uncontrolled diagnostic blocks of the lumbar zygapophysial joints.

One hundred and seventy-six consecutive patients with chronic low back pain and no history of previous lumbar surgery were studied to determine the false-positive rate of single diagnostic blocks of the lumbar zygapophysial joints. All patients underwent diagnostic blocks using lignocaine. Those patients who obtained definite or complete relief from these blocks subsequently underwent confirmatory blocks using bupivacaine. Eighty-three patients (47%) had a definite or greater response to the initial, lignocaine injection at one or more levels but only 26 (15%) had a 50% or greater response to a confirmatory injection of 0.5% bupivacaine. Using the response to confirmatory blocks as the criterion standard, the false-positive rate of uncontrolled diagnostic blocks was 38% and the positive predictive value of these blocks was only 31%. Because the positive predictive value of a test is lower when the pre-test probability (prevalence) is low, and because the prevalence of lumbar zygapophysial joint pain is likely to be less than 50%, uncontrolled diagnostic blocks will always be associated with an unacceptably low positive predictive value. These features render uncontrolled diagnostic blocks unreliable for the diagnosis of lumbar zygapophysial joint pain not only in epidemiologic studies but also in any given patient.

Adult↗
PubMed1994

The value of the provocation response in lumbar zygapophyseal joint injections.

OBJECTIVE: To determine the relationship between pain provocation and the analgesic response in lumbar zygapophyseal joint blocks. DESIGN: Consecutive patients undergoing intraarticular zygapophyseal joint blocks for the investigation of low back pain were included in this prospective study. SETTING: The referred sample was from the metropolitan areas of New Orleans and San Francisco. PATIENTS: Ninety patients with low back pain of > 3 months' duration and no history of lumbar surgery. INTERVENTIONS: All patients underwent one or more intraarticular injections of radiographic contrast followed by lignocaine (lidocaine) 2% into zygapophyseal joints between L2-3 and L5-S1. Those with definite responses at one or more levels underwent confirmatory blocks using 0.5% bupivacaine. OUTCOME MEASURES: Provocation of familiar pain and relief of pain after the injection of local anesthetic. Patients were assessed by an independent observer. RESULTS: A total of 203 joints were studied. Adopting liberal criteria, either exact or similar reproduction of pain on the one hand correlated with either definite or complete relief of pain after a single, analgesic block on the other (p < 0.0001). However, when more stringent criteria were adopted, such as response to a confirmatory block using bupivacaine, there was no significant association. CONCLUSIONS: This study calls into question the validity of pain provocation alone as a criterion standard in patients undergoing diagnostic lumbar zygapophyseal joint blocks.

Adult↗
PubMed1994

Pain from the lumbar zygapophysial joints: a test of two models.

One hundred seventy-six consecutive patients with chronic low-back pain and no history of previous lumbar surgery were studied to test the clinical criteria of Fairbank et al. and Helbig and Lee for zygapophysial joint pain. All patients underwent a history, examination, and a series of zygapophysial joint injections or blocks of the medial branches of the dorsal ramus with lignocaine. Those patients responding to the first series of blocks were given confirmatory blocks using bupivacaine. None of the clinical features tested was found to be associated with response to the confirmatory block. The Fairbank et al. and Helbig and Lee criteria were shown to be unreliable in distinguishing pain of zygapophysial joint origin from pain of other origins.

Adult↗