Role of Nitrogen Oxide (NO) in the Control of Choroidal Blood Flow During a Decrease in Ocular Perfusion Pressure

This study has been completed.
Sponsor:
Information provided by:
Medical University of Vienna
ClinicalTrials.gov Identifier:
NCT00810927
First received: December 17, 2008
Last updated: NA
Last verified: December 2008
History: No changes posted

December 17, 2008
December 17, 2008
September 2003
February 2004   (final data collection date for primary outcome measure)
ocular perfusion pressure - choroidal blood flow relationship
Same as current
No Changes Posted
Not Provided
Not Provided
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Role of Nitrogen Oxide (NO) in the Control of Choroidal Blood Flow During a Decrease in Ocular Perfusion Pressure
Role of NO in the Control of Choroidal Blood Flow During a Decrease in Ocular Perfusion Pressure

Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. For a long time it had been assumed that the choroid is a strictly passive vascular bed, which shows no autoregulation. However, recently several groups have identified some autoregulatory capacity of the human choroid. In the brain and the retina the mechanism behind autoregulation is most likely linked to changes in transmural pressure. In this model arterioles change their vascular tone depending on the pressure inside the vessel and outside the vessel. In the choroid, several observations argue against a direct involvement of arterioles. However, the mechanism behind choroidal autoregulation remains unclear.

In the present study autoregulation of the choroid will be investigated during a decrease in ocular perfusion pressure, which will be achieved by an increase in intraocular pressure. Pressure/flow relationships will be investigated in the absence or presence of a NO synthase inhibitor. As a control substance the alpha-receptor agonist phenylephrine will be used.

Not Provided
Interventional
Phase 2
Allocation: Randomized
Endpoint Classification: Safety/Efficacy Study
Intervention Model: Crossover Assignment
Masking: Double Blind (Subject, Investigator, Outcomes Assessor)
Primary Purpose: Treatment
  • Physiology, Ocular
  • Microcirculation
  • Regional Blood Flow
  • Autoregulation
  • Procedure: Suction cup application
    he IOP will be raised by a 11 mm diameter, standardized suction cup placed on the temporal sclera with the anterior edge at least 1 mm from the limbus.
  • Procedure: Laser Doppler flowmetry
    Measurement of choroidal blood flow
  • Procedure: Measurement of intraocular pressure
  • Active Comparator: 1
    Phenylephrine (Neosynephrine®, Abbott Laboratories, North Chicago, IL, USA) dose: 1µg/(kg.min), infusion period 20 minutes
    Interventions:
    • Procedure: Suction cup application
    • Procedure: Laser Doppler flowmetry
    • Procedure: Measurement of intraocular pressure
  • Active Comparator: 2
    NG-monomethyl-L-arginine (L-NMMA, Clinalfa, Läufelfingen, Switzerland) dose: bolus 6mg/kg over 5 minutes followed by a continuous infusion of 60µg/(kg.min) over 15 minutes
    Interventions:
    • Procedure: Suction cup application
    • Procedure: Laser Doppler flowmetry
    • Procedure: Measurement of intraocular pressure
  • Placebo Comparator: 3
    Physiologic saline solution
    Interventions:
    • Procedure: Suction cup application
    • Procedure: Laser Doppler flowmetry
    • Procedure: Measurement of intraocular pressure
Not Provided

*   Includes publications given by the data provider as well as publications identified by ClinicalTrials.gov Identifier (NCT Number) in Medline.
 
Completed
22
August 2005
February 2004   (final data collection date for primary outcome measure)

Inclusion Criteria:

  • Men aged between 19 and 35 years, nonsmokers
  • Body mass index between 15th and 85th percentile (Must et al. 1991)
  • Normal findings in the medical history and physical examination unless the investigator considers an abnormality to be clinically irrelevant
  • Normal laboratory values unless the investigator considers an abnormality to be clinically irrelevant
  • Normal ophthalmic findings, ametropia < 3 Dpt.

Exclusion Criteria:

  • Regular use of medication, abuse of alcoholic beverages, participation in a clinical trial in the 3 weeks preceding the study
  • Treatment in the previous 3 weeks with any drug
  • Symptoms of a clinically relevant illness in the 3 weeks before the first study day
  • History of hypersensitivity to the trial drug or to drugs with a similar chemical structure
  • History or presence of gastrointestinal, liver or kidney disease, or other conditions known to interfere with, distribution, metabolism or excretion of study drugs
  • Blood donation during the previous 3 weeks
Male
19 Years to 35 Years
Yes
Contact information is only displayed when the study is recruiting subjects
Austria
 
NCT00810927
OPHT-270602
Yes
Gabriele Fuchsjaeger-Mayrl, MD, Department of Clinical Pharmacology, Medical University of Vienna
Medical University of Vienna
Not Provided
Principal Investigator: Gabriele Fuchsjäger-Mayrl, MD Department of Clinical Pharmacology, Medical University of Vienna
Medical University of Vienna
December 2008

ICMJE     Data element required by the International Committee of Medical Journal Editors and the World Health Organization ICTRP