title: Ocular oxygen consumption: estimates using vitreoperfusion in the cat.
abstract: OBJECTIVE
  Little is known about the ocular oxygen consumption rate (QO2) in human diseases. Alterations in QO2 must occur in many conditions, such as retinal ischemia. We present a method of estimating QO2 that eventually could be used in patients during vitrectomy surgery.
  
  
  METHODS
  We performed vitreoperfusion (i.e., perfusion of the vitreous cavity after vitrectomy) in 14 cat eyes with no ocular blood flow. The solution contained nutrients at a high partial pressure of oxygen (PO2). In eight eyes, the retinas were undisturbed (Group 1), and in six eyes, we excised the retinas (Group 2). We estimated QO2 in both groups on the basis of the temporal decline of PO2 in the vitreoperfusion solution according to a pharmacokinetic model.
  
  
  RESULTS
  The mean and standard deviation of QO2 was 3.2 +/- 0.8 microL/min in Group 1 and 0.4+/- 0.7 microL/min in Group 2, with the difference being the retinal contribution, 88%. In Group 1, metabolism, bulk flow, and diffusion accounted for 82, 13, and 5%, respectively, of the oxygen loss from the vitreoperfusion solution.
  
  
  CONCLUSIONS
  We estimated ocular oxygen consumption by means of vitreoperfusion. Eventually, the pathophysiology of human diseases may be clarified by similar measurements during vitrectomy.
authors.affiliation: Laboratory of Retinal Circulation and Metabolism, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, 2855 West Taylor Street, Chicago, IL 60612, USA. npblair@uic.edu
authors.forename: Norman P
authors.initials: NP
authors.lastname: Blair
authors.forename: Ting
authors.initials: T
authors.lastname: Liu
authors.forename: Keith A
authors.initials: KA
authors.lastname: Warren
authors.forename: David A
authors.initials: DA
authors.lastname: Glaser
authors.forename: Marc
authors.initials: M
authors.lastname: Kennedy
authors.forename: Huan
authors.initials: H
authors.lastname: Tran
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Larson
authors.forename: Prasant
authors.initials: P
authors.lastname: Atluri
authors.forename: Michael A
authors.initials: MA
authors.lastname: Saidel
authors.forename: Michael P
authors.initials: MP
authors.lastname: Blair
mesh_terms: D000818:Animals; D002404:Catheterization / Q000379:methods; D002415:Cats; D004734:Energy Metabolism; D005260:Female; D000860:Hypoxia / Q000378:metabolism*; D007511:Ischemia / Q000378:metabolism; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010477:Perfusion; D012160:Retina / Q000378:metabolism*; D014821:Vitrectomy