NCT00810927

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.

Trial Health

87
On Track

Trial Health Score

Automated assessment based on enrollment pace, timeline, and geographic reach

Enrollment
22

participants targeted

Target at below P25 for phase_2

Timeline
Completed

Started Sep 2003

Geographic Reach
1 country

1 active site

Status
completed

Health score is calculated from publicly available data and should be used for screening purposes only.

Trial Relationships

Click on a node to explore related trials.

Study Timeline

Key milestones and dates

Study Start

First participant enrolled

September 1, 2003

Completed
5 months until next milestone

Primary Completion

Last participant's last visit for primary outcome

February 1, 2004

Completed
1.5 years until next milestone

Study Completion

Last participant's last visit for all outcomes

August 1, 2005

Completed
3.4 years until next milestone

First Submitted

Initial submission to the registry

December 17, 2008

Completed
1 day until next milestone

First Posted

Study publicly available on registry

December 18, 2008

Completed
Last Updated

December 18, 2008

Status Verified

December 1, 2008

Enrollment Period

5 months

First QC Date

December 17, 2008

Last Update Submit

December 17, 2008

Conditions

Physiology, OcularMicrocirculationRegional Blood FlowAutoregulation

Outcome Measures

Primary Outcomes (1)

  • ocular perfusion pressure - choroidal blood flow relationship

Study Arms (3)

1

ACTIVE COMPARATOR

Phenylephrine (Neosynephrine®, Abbott Laboratories, North Chicago, IL, USA) dose: 1µg/(kg.min), infusion period 20 minutes

Procedure: Suction cup applicationProcedure: Laser Doppler flowmetryProcedure: Measurement of intraocular pressure

2

ACTIVE COMPARATOR

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 applicationProcedure: Laser Doppler flowmetryProcedure: Measurement of intraocular pressure

3

PLACEBO COMPARATOR

Physiologic saline solution

Procedure: Suction cup applicationProcedure: Laser Doppler flowmetryProcedure: Measurement of intraocular pressure

Interventions

Suction cup applicationPROCEDURE

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.

123
Laser Doppler flowmetryPROCEDURE

Measurement of choroidal blood flow

123
Measurement of intraocular pressurePROCEDURE
123

Eligibility Criteria

Age19 Years - 35 Years
Sexmale
Healthy VolunteersYes
Age GroupsAdult (18-64)

You may qualify if:

  • 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.

You may not qualify if:

  • 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

Contact the study team to confirm eligibility.

Sponsors & Collaborators

Study Sites (1)

Department of Clinical Pharmacology, Medical University of Vienna

Vienna, 1090, Austria

Location

MeSH Terms

Interventions

Laser-Doppler Flowmetry

Intervention Hierarchy (Ancestors)

Diagnostic Techniques, CardiovascularDiagnostic Techniques and ProceduresDiagnosisRheologyInvestigative Techniques

Study Officials

  • Gabriele Fuchsjäger-Mayrl, MD

    Department of Clinical Pharmacology, Medical University of Vienna

    PRINCIPAL INVESTIGATOR

Study Design

Study Type
interventional
Phase
phase 2
Allocation
RANDOMIZED
Masking
TRIPLE
Who Masked
PARTICIPANT, INVESTIGATOR, OUTCOMES ASSESSOR
Purpose
TREATMENT
Intervention Model
CROSSOVER
Sponsor Type
OTHER

Study Record Dates

First Submitted

December 17, 2008

First Posted

December 18, 2008

Study Start

September 1, 2003

Primary Completion

February 1, 2004

Study Completion

August 1, 2005

Last Updated

December 18, 2008

Record last verified: 2008-12

Locations

AU(1)