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Anesth Analg 1988; 67:988-992
© 1988 International Anesthesia Research Society
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High Pressure and Anesthesia

Pressure Stimulates or Inhibits Bacterial Bioluminescence Depending upon Temperature

Shuichi Nosaka, MD, Hiroshi Kamaya, MD, and Issaku Ueda, MD

Department of Anesthesia, University of Utah School of Medicine, and Anesthesia Service, Veterans Administration Medical Center, Salt Lake City, Utah.

Although high pressure is often viewed as a nonspecific stimulus counteracting anesthesia, pressure can either ex-ate or inhibit biological activity depending on the temperature at application. Temperature and pressure are two independent variables that determine equilibrium quantity, e.g., the state of organisms in terms of activity and anesthesia depth. We used the light intensity of luminous bacteria (Vibrio fischeri) as an activity parameter, and studied the effects of pressure and anesthetics on the bacteria's light intensity at various temperatures. The light intensity was greatest at about 30°C at ambient pressure. When the system was, pressurized up to 204 atm, the temperature for maximum light intensity was shifted to higher temperatures. Above the optimal temperature for the maximal light intensity, high pressure increased the light intensity. Below the optimal temperature, pressure decreased light intensity. Pressure only shifts the reaction equilibrium to the lower volume state (Le Chatelier's principle). When the volume of the excited state is larger than the resting state, high pressure inhibits excitation, and vice verso.

Halothane 0.008 atm and isoflurane 0.022 atm inhibited the light intensity both above and below the optimal temperature. When pressurized, the light intensity increased in the high temperature range hit decreased in the low temperature range, as in the control. Thus, high pressure seemingly potentiated the anesthetic action at low temperatures. When the ratio of the light intensity in bacteria exposed to anesthesia and those not exposed to anesthesia was plotted against the pressure, however, the value approached unity in proportion to the pressure increase. Because the light intensity under anesthesia approaches the control value at higher pressures regardless of the temperature range, pressure antagonizes anesthesia despite the apparent decrease in the intensity.

We conclude that (i) pressure is not simply an excitatory stimuli but can be inhibitory too, depending upon the temperature; also, that (ii) despite this dual effect, pressures up to 204 atm reverse anesthesia in this model over the temperature range 15 to 40° C.

Key Words: HYPERBARIA, anesthesia reversal. • THEORIES OF ANESTHESIC ACTION—pressure reversal.






Lippincott, Williams & Wilkins Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999 HighWire Press
Copyright © 1988 by the International Anesthesia Research Society.