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Chronically administered progesterone decreases halothane requirements in rabbits.
S Datta1, R P Migliozzi, H L Flanagan
1Department of Anesthesia Research Laboratories, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115.
Anesthesia and Analgesia
|January 1, 1989
Summary
Progesterone administration significantly reduced the minimal alveolar concentration (MAC) of halothane in rabbits. This finding suggests progesterone may explain the lower anesthetic requirements observed during pregnancy.
Area of Science:
- Anesthesiology
- Reproductive Endocrinology
Background:
- Pregnant ewes exhibit a 25% lower MAC for halothane compared to nonpregnant ewes.
- Steroidal hormones and endogenous opiates are suspected factors influencing anesthetic requirements during pregnancy.
Purpose of the Study:
- To investigate the impact of exogenous progesterone on the MAC of halothane.
- To determine if progesterone administration can lower halothane MAC in ovariectomized rabbits.
Main Methods:
- Determined halothane MAC in three groups of female rabbits: intact (Group A), ovariectomized with carrier (Group B), and ovariectomized with progesterone (Group C).
- Measured plasma progesterone concentrations in all groups.
Main Results:
- No significant difference in halothane MAC was observed between intact (1.68 ± 0.06%) and ovariectomized control rabbits (1.77 ± 0.06%).
- Progesterone-treated rabbits (Group C) showed a significantly lower halothane MAC (1.48 ± 0.06%) compared to control groups (P < 0.01).
- Plasma progesterone levels were significantly elevated in Group C (37.33 ± 4.25 ng/ml) compared to Groups A and B.
Conclusions:
- Experimental administration of progesterone effectively reduces the MAC of halothane in rabbits.
- These findings support the hypothesis that progesterone contributes to the decreased need for inhalation anesthetics during human parturition.