August 1995
Volume 36, Issue 9
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Articles  |   August 1995
Retinal tissue oxygen tension in normoxic cats under enflurane anesthesia.
Author Affiliations
  • K A Neely
    Duke University Eye Center, Durham, North Carolina, USA.
  • J T Ernest
    Duke University Eye Center, Durham, North Carolina, USA.
  • T K Goldstick
    Duke University Eye Center, Durham, North Carolina, USA.
Investigative Ophthalmology & Visual Science August 1995, Vol.36, 1943-1946. doi:
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      K A Neely, J T Ernest, T K Goldstick; Retinal tissue oxygen tension in normoxic cats under enflurane anesthesia.. Invest. Ophthalmol. Vis. Sci. 1995;36(9):1943-1946.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

PURPOSE: General anesthesia reduces systemic blood pressure and, thus, ocular perfusion pressure (at constant intraocular pressure). Whether this reduction in ocular perfusion pressure produces retinal hypoxia is unknown. To answer this question, the authors measured inner retinal oxygen tension in cats under general enflurane anesthesia at three clinically relevant levels of anesthesia under normoxic conditions. METHODS: Polarographic oxygen microelectrodes were used to measure inner retinal oxygen tension in cats under enflurane anesthesia at 21% inspired oxygen tension. Measurements were made in the preretinal vitreous body within 100 to 200 microns of the internal limiting membrane of the retina. Three levels of enflurane anesthesia were used: 1.2%, 2.4%, and 3.6%, corresponding to 0.5, 1.0, and 1.5 minimal alveolar concentration. Intraocular pressure of the cats was maintained at a constant normal level throughout the experiments. RESULTS: Under normoxic conditions, inner retinal oxygen tension remained unchanged or increased slightly as ocular perfusion pressure decreased with deeper levels of enflurane anesthesia. CONCLUSION: Commonly used surgical levels of enflurane general anesthesia do not cause hypoxia of the inner retina in cats breathing 21% inspired oxygen. This may be the result of preservation of retinal vascular autoregulation under enflurane anesthesia, retinal vasodilatation secondary to a direct smooth muscle relaxing effect of enflurane, or decreased retinal oxygen use under enflurane anesthesia.

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