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Canadian Journal of Anesthesia, Vol 15, 172-183, Copyright © 1968 by Canadian Anesthesiologists' Society

Effect of Methoxyflurane Anaesthesia on Intraocular Pressure

ALFONSO SCHETTINI M.D.1, E. STEWART OWRE M.D.1, and AUSTIN I. FINK M.D.1

1 Long Island College Hospital, Brooklyn, N.Y.

The effect of methoxyflurane anaesthesia on intraocular pressure was investigated in 30 patients. This inhalant agent effectively reduced the intraocular pressure throughout the first 30 minutes of the arousal period, as well as during light and moderate anaesthesia. Although a further decrease in pressure occurred with increasing depth of anaesthesia, this reduction was not as significant as the initial one from control value to light anaesthesia.

Analyses of variances failed to demonstrate any statistical difference between the various methods investigated: assisted ventilation, controlled ventilation by IPPB and by PNPB, light and moderate anaesthesia. Similarly, hyperventilation did not differ significantly from the other methods studied. The order of fall in intraocular pressure under these conditions, however, is maintained, with the greatest falls occurring during moderately deep anaesthesia and during hyperventilation, and the smallest during light anaesthesia. In all the methods investigated, the ventilatory parameters were kept within or above normal limits.

Selection of a particular method of ventilation is influenced by its concomitant side-effects which may tend to cancel out the desired lower ocular tension. The use of vasopressors to correct arterial hypotension leads to a rise in intraocular pressure; an excessive rise in venous pressure could increase intraocular pressure by impairing the outflow or by elevating the intraocular vascular content.

Our conclusion, that all six methods employed clinically are effective in lowering intraocular pressure during methoxyflurane anaesthesia, is soundly supported by statistical evidence, provided that ventilation is maintained within or above normal limits, that the venous pressure is not unduly increased, and that the steady state of anaesthesia is achieved without respiratory difficulties.

Note:
This research was supported in part by a grant from Abbott Laboratories, Chicago, Illinois, and by the NIH grant #FR00291 to the Computing Center of the Downstate Medical Center, New York, N.Y.






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Copyright © 1968 by the Canadian Anesthesiologists' Society.