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Nitrous oxide depresses spinal F waves in rats
Y Friedman1, B S King, I J Rampil
1Department of Anesthesia, University of California, San Francisco 94143-0648, USA.
Anesthesiology
|July 1, 1996
Summary
Nitrous oxide, alone or with isoflurane, depresses F-wave activity in rats, indicating a central nervous system effect. This depression correlates with reduced movement, suggesting F-waves could predict anesthetic-induced immobility.
Area of Science:
- Anesthesiology
- Neurophysiology
Background:
- Evoked, recurrent electromyographic activity (F waves) are indicators of alpha-motor neuron excitability.
- Inhaled anesthetics are known to affect motor neuron excitability.
Purpose of the Study:
- To investigate the effect of nitrous oxide, alone and with isoflurane, on F-wave activity in rats.
- To determine if F-wave depression correlates with anesthetic-induced immobility.
Main Methods:
- Rats were anesthetized with isoflurane and received varying concentrations of nitrous oxide.
- Electromyographic activity (M and F waves) and motor response to stimuli were recorded.
- F-wave amplitude to M-wave amplitude ratio (F/M) was analyzed in relation to immobility.
Main Results:
- Nitrous oxide caused a dose-dependent decrease in the F/M ratio.
- Both combined isoflurane/nitrous oxide and hyperbaric nitrous oxide significantly reduced F/M.
- Depressed F/M correlated with suppressed movement response to stimuli.
Conclusions:
- Nitrous oxide's effect on F-waves suggests a central (spinal) mechanism of action.
- F-wave activity may serve as a predictor for anesthetic-induced immobility.
- Nitrous oxide's mechanism may differ from potent inhaled anesthetics.