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Sponsored by: |
Medical University of Vienna |
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Information provided by: | Medical University of Vienna |
ClinicalTrials.gov Identifier: | NCT00914394 |
Autoregulation is defined as the ability of a vascular bed to adapt its vascular resistance to changes in perfusion pressure. In the eye, several studies have reported that retinal blood flow is autoregulated over a wide range of ocular perfusion pressures. Large scale studies have shown that reduced ocular perfusion pressure is an important risk factor for the prevalence, the incidence and the progression of primary open angle glaucoma. Former studies that investigated ocular blood flow autoregulation focused mainly on choroidal blood flow. For the optic nerve head only few data are available, although it seems likely that it underlies similar autoregulatory mechanisms. A previous study investigating choroidal blood flow has shown that nitric oxide (NO) plays a key role in choroidal autoregulation. The present study is designed to test the hypothesis that NO plays a role in optic nerve head autoregulation during increased intraocular pressure (IOP). Therefore, IOP will be experimentally increased using a suction cup device in the absence of presence of either a nitric oxide synthase inhibitor (L-NMMA), an α-receptor agonist (phenylephrine) or placebo. Optic nerve head blood flow will be continuously measured during the procedure.
Condition | Intervention |
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Healthy |
Drug: NG-monomethyl-L-arginine (L-NMMA) Drug: Phenylephrine Drug: Physiological saline solution (as placebo) Device: Laser Doppler Flowmetry Device: Goldmann applanation tonometer Device: Suction cup |
Study Type: | Interventional |
Study Design: | Basic Science, Randomized, Double Blind (Subject, Investigator, Outcomes Assessor), Placebo Control, Crossover Assignment, Safety/Efficacy Study |
Official Title: | Role of Nitric Oxide in Optic Nerve Head Blood Flow Regulation During Experimental Increase of Intraocular Pressure in Healthy Humans |
Estimated Enrollment: | 24 |
Study Start Date: | July 2009 |
Estimated Primary Completion Date: | July 2010 (Final data collection date for primary outcome measure) |
Arms | Assigned Interventions |
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NG-monomethyl-L-arginine (L-NMMA): Active Comparator |
Drug: NG-monomethyl-L-arginine (L-NMMA)
bolus 6mg/kg over 5 minutes followed by a continuous infusion of 60µg/kg/min over 15 minutes
Drug: Phenylephrine
1µg/kg/min, infusion period 20 minutes
Drug: Physiological saline solution (as placebo)
infusion period 20 minutes
Device: Laser Doppler Flowmetry
Measurements will be performed at the neuroretinal rim to assess ONH blood flow.
Device: Goldmann applanation tonometer
intraocular pressure measurements
Device: Suction cup
Experimental stepwise increase of intraocular pressure while measurement of optic nerve head blood flow.
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Phenylephrine: Active Comparator |
Drug: NG-monomethyl-L-arginine (L-NMMA)
bolus 6mg/kg over 5 minutes followed by a continuous infusion of 60µg/kg/min over 15 minutes
Drug: Phenylephrine
1µg/kg/min, infusion period 20 minutes
Drug: Physiological saline solution (as placebo)
infusion period 20 minutes
Device: Laser Doppler Flowmetry
Measurements will be performed at the neuroretinal rim to assess ONH blood flow.
Device: Goldmann applanation tonometer
intraocular pressure measurements
Device: Suction cup
Experimental stepwise increase of intraocular pressure while measurement of optic nerve head blood flow.
|
Physiological saline solution: Placebo Comparator |
Drug: NG-monomethyl-L-arginine (L-NMMA)
bolus 6mg/kg over 5 minutes followed by a continuous infusion of 60µg/kg/min over 15 minutes
Drug: Phenylephrine
1µg/kg/min, infusion period 20 minutes
Drug: Physiological saline solution (as placebo)
infusion period 20 minutes
Device: Laser Doppler Flowmetry
Measurements will be performed at the neuroretinal rim to assess ONH blood flow.
Device: Goldmann applanation tonometer
intraocular pressure measurements
Device: Suction cup
Experimental stepwise increase of intraocular pressure while measurement of optic nerve head blood flow.
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Ages Eligible for Study: | 18 Years to 35 Years |
Genders Eligible for Study: | Both |
Accepts Healthy Volunteers: | Yes |
Inclusion Criteria:
Exclusion Criteria:
Contact: Gerhard Garhoefer, MD, Priv-Doz | 0043 1 40400 ext 2981 | gerhard.garhoefer@meduniwien.ac.at |
Austria | |
Department of Clinical Pharmacology, Medical University of Vienna | |
Vienna, Austria, 1090 |
Principal Investigator: | Gabriele Fuchsjaeger-Mayrl, MD, Univ.Doz. | Department of Clinical Pharmacology, Medical University of Vienna |
Responsible Party: | Department of Clinical Pharmacology, Medical University of Vienna ( Gabriele Fuchsjaeger-Mayrl, MD ) |
Study ID Numbers: | OPHT-310708 |
Study First Received: | June 1, 2009 |
Last Updated: | June 4, 2009 |
ClinicalTrials.gov Identifier: | NCT00914394 History of Changes |
Health Authority: | Austria: Agency for Health and Food Safety |
L-NG-Monomethyl Arginine Optic Nerve Head Blood Flow Intraocular Pressure |
Regional Blood Flow Ocular Physiology Optic Disk |
Pseudoephedrine Neurotransmitter Agents Vasodilator Agents Adrenergic alpha-Agonists Antioxidants Adrenergic Agents Arginine Anti-Asthmatic Agents Healthy Cardiovascular Agents Adrenergic Agonists |
Nasal Decongestants Nitric Oxide Oxymetazoline Mydriatics Phenylephrine Omega-N-Methylarginine Vasoconstrictor Agents Ephedrine Peripheral Nervous System Agents Bronchodilator Agents |
Respiratory System Agents Neurotransmitter Agents Vasodilator Agents Antioxidants Molecular Mechanisms of Pharmacological Action Adrenergic Agents Cardiotonic Agents Physiological Effects of Drugs Adrenergic Agonists Nasal Decongestants Phenylephrine Therapeutic Uses Free Radical Scavengers Vasoconstrictor Agents |
Endothelium-Dependent Relaxing Factors Adrenergic alpha-Agonists Sympathomimetics Anti-Asthmatic Agents Enzyme Inhibitors Cardiovascular Agents Protective Agents Pharmacologic Actions Nitric Oxide Mydriatics Autonomic Agents Omega-N-Methylarginine Peripheral Nervous System Agents Bronchodilator Agents |