NCT00406731

Role of Endothelin- and Nitric Oxide-system in the Regulation of Optic Nerve Head Blood Flow During Changes in Ocular Perfusion Pressure

Role of endothelin-and Nitric Oxide-system in the Regulation of Optic Nerve Head Blood Flow During Changes in Ocular Perfusion Pressure

• Status: Withdrawn
• Phase: Phase 2
• Study type: Interventional
• Enrollment: 0 (actual)
• Sponsor: Medical University of Vienna · Academic / Other
• Sex: Male
• Age: 18 Years – 35 Years
• Healthy volunteers: Accepted

Summary

Autoregulation is the ability of a vascular bed to maintain blood flow despite changes in perfusion pressure. The existence of an effective autoregulation in the optic nerve circulation has been shown in animals and humans. The exact mechanism behind this autoregulation is still unknown. The motive for the investigation of optic nerve head (ONH) blood flow autoregulation is to enhance the understanding of pathologic eye conditions associated with ocular vascular disorders. To clarify the regulatory mechanisms of ONH microcirculation is of critical importance to understand the pathophysiology of glaucoma because there is evidence that glaucoma is associated with optic nerve head ischemia. Several studies indicate that a disturbed autoregulation might contribute to glaucomatous optic neuropathy. Previous findings suggest endothelial dysfunction in glaucomatous optic neuropathy, in particular alterations in endothelin- and nitric oxide- system, which both play an important role in local regulation of vascular tone. In the present study, changes in ocular perfusion pressure will be performed during administration of drugs, which may potentially alter the pressure-flow relationship. These drugs include endothelin-1 and the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA).

Conditions

• Ocular Physiology
• Optic Disk
• Regional Blood Flow

Interventions

Type	Name	Description
DRUG	NG-monomethyl-L-arginine (L-NMMA)	bolus 6 mg/kg over 5 minutes followed by a continuous intravenous infusion of 60 µg/kg/min over 12 minutes; twice on 1 study day
DRUG	Endothelin-1 (ET-1)	5 ng/kg/min intravenous infusion over 17 minutes; twice on 1 study day
DRUG	Physiologic saline solution (placebo control)	intravenous infusion over 20 minutes; twice on 1 study day
DEVICE	Laser Doppler flowmetry	blood flow measurements at the temporal neuroretinal rim of the optic nerve head
DEVICE	Goldmann applanation tonometer	Intraocular pressure measurements
DEVICE	HP-CMS patient monitor	blood pressure and pulse rate measurements
PROCEDURE	Suction cup method	The IOP will be raised by an 11 mm diameter, standardized suction cup placed on the temporal sclera with the anterior edge at least 1 mm from the limbus.

Timeline

• Start date: 2008-01-01
• Primary completion: 2014-11-01
• Completion: 2014-11-01
• First posted: 2006-12-04
• Last updated: 2019-08-15

Locations

1 site across 1 country: Austria