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

• Sponsor: Medical University of Vienna (Other)
• Overall Status: Completed
• CT.gov ID: NCT00810927
• Collaborator: (none)
• Enrollment: 22
• Location: 1
• Arms: 3
• Duration (Months): 23
• Patients Per Site Per Month: 1

Study Details

Study Description

Brief Summary

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.

Condition or Disease	Intervention/Treatment	Phase
Physiology, Ocular; Microcirculation; Regional Blood Flow; Autoregulation	Procedure: Suction cup application; Procedure: Laser Doppler flowmetry; Procedure: Measurement of intraocular pressure	Phase 2

Study Design

• Study Type: Interventional
• Actual Enrollment: 22 participants
• Allocation: Randomized
• Intervention Model: Crossover Assignment
• Masking: Triple (Participant, Investigator, Outcomes Assessor)
• Primary Purpose: Treatment
• Official Title: Role of NO in the Control of Choroidal Blood Flow During a Decrease in Ocular Perfusion Pressure
• Study Start Date: Sep 1, 2003
• Actual Primary Completion Date: Feb 1, 2004
• Actual Study Completion Date: Aug 1, 2005

Arms and Interventions

Arm	Intervention/Treatment
Active Comparator: 1 Phenylephrine (Neosynephrine®, Abbott Laboratories, North Chicago, IL, USA) dose: 1µg/(kg.min), infusion period 20 minutes	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: 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	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
Placebo Comparator: 3 Physiologic saline solution	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

Outcome Measures

Primary Outcome Measures

1. ocular perfusion pressure - choroidal blood flow relationship []

Eligibility Criteria

Criteria

• Ages Eligible for Study: 19 Years to 35 Years
• Sexes Eligible for Study: Male
• Accepts Healthy Volunteers: Yes

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

Contacts and Locations

Locations

	Site	City	State	Country	Postal Code
1	Department of Clinical Pharmacology, Medical University of Vienna	Vienna		Austria	1090

Sponsors and Collaborators

• Medical University of Vienna

Investigators

• Principal Investigator: Gabriele Fuchsjäger-Mayrl, MD, Department of Clinical Pharmacology, Medical University of Vienna

Study Documents (Full-Text)

None provided.

More Information

Publications

None provided.

• ClinicalTrials.gov Identifier: NCT00810927
• Other Study ID Numbers: OPHT-270602
• First Posted: Dec 18, 2008
• Last Update Posted: Dec 18, 2008
• Last Verified: Dec 1, 2008

Study Results

No Results Posted as of Dec 18, 2008