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Titolo:
NITROUS-OXIDE DEPRESSES SPINAL F-WAVE IN RATS
Autore:
FRIEDMAN Y; KING BS; RAMPIL IJ;
Indirizzi:
UNIV CALIF SAN FRANCISCO,DEPT ANESTHESIA,ROOM C-450 SAN FRANCISCO CA 94143 UNIV CALIF SAN FRANCISCO,DEPT ANESTHESIA SAN FRANCISCO CA 94143
Titolo Testata:
Anesthesiology
fascicolo: 1, volume: 85, anno: 1996,
pagine: 135 - 141
SICI:
0003-3022(1996)85:1<135:NDSFIR>2.0.ZU;2-1
Fonte:
ISI
Lingua:
ENG
Soggetto:
MINIMUM ALVEOLAR CONCENTRATION; SYNAPTIC TRANSMISSION; ANESTHETIC POTENCY; HUMANS; CORD; NEURONS; MOTONEURONS; MECHANISMS; ISOFLURANE; HALOTHANE;
Keywords:
ANESTHETIC MECHANISMS; ANESTHETIC POTENCY; ANESTHETICS, INHALED, NITROUS OXIDE; ANESTHETICS, VOLATILE, ISOFLURANE; MEASUREMENT TECHNIQUES, ELECTROMYOGRAPHY; SPINAL CORD, MOTOR NEURONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
30
Recensione:
Indirizzi per estratti:
Citazione:
Y. Friedman et al., "NITROUS-OXIDE DEPRESSES SPINAL F-WAVE IN RATS", Anesthesiology, 85(1), 1996, pp. 135-141

Abstract

Background: Evoked, recurrent electromyographic activity (F waves) reflect alpha-motor neuron excitability. Based on observations that other inhaled anesthetics do so, we hypothesized that nitrous oxide, aloneor in combination with isoflurane, would depress F-wave activity and correlate with depression of movement response to tail clamp or electric stimulation. Methods: In study 1, the authors examined the effect of nitrous oxide in combination with isoflurane in 13 normocapnic Sprague-Dawley rats anesthetized with 1.0% isoflurane (0.7 minimum alveolarconcentration) in oxygen. The tibial nerve was stimulated at the popliteal fossa, and evoked electromyographic activity [M (direct neuromuscular junctional response) and F waves] were recorded from ipsilateralfoot muscles. The effect of the addition of 30% or 70% nitrous oxide was measured. F-wave amplitude/M-wave amplitude ratio (F/M) was determined from each stimulus-electromyographic response pair. F/M vs. movement response to 60-s tail clamp was assessed after each recording session. F-wave amplitude/M-wave amplitude ratio at adjacent doses that permitted and prevented movement were compared. In study 2, the authors examined the effect of (hyperbaric) nitrous oxide as the sole anesthetic agent on F waves. In 11 rats anesthetized with isoflurane, stimulation and recording electrodes were placed as described above, with additional electrodes for stimulation placed in the tail. Rats were placedin a pressure chamber pressurized with nitrous oxide/oxygen to 3.4 atm. Thirty m were allowed for isoflurane washout, electromyographic activity was evoked and recorded at 1.0, 1.6, 2.2, and 2.7 atm N2O (random order). Movement in response to 60 s of 15 V, 50-Hz tail stimulationwas evaluated after each recording session. Results: Nitrous oxide with or without isoflurane produced a dose-dependent decrease in F/M. Byinterpolation of this data, the authors found that 2 atm N2O alone, or 44% N2O added to 1.0% isoflurane at 1.0 atm, produced 1.0 minimum alveolar concentration anesthesia. At the deepest level of isoflurane/ nitrous oxide that permitted movement, mean F/M was 20.6 +/- 17.5%; at the lowest concentration that blocked movement, rats had a mean F/M of13.7 +/- 13.9% (P = 0.01). At the minimal hyperbaric nitrous oxide blocking movement, rats had a mean F/M of 3.7 +/- 2.9%, whereas the F/M at the highest nitrous oxide dose that permitted movement was 4.4 +/- 2.7% (P < 0.04). Conclusions: Because nitrous oxide depressed F-wave but not M-wave activity, the data suggest a central (spinal) rather than neuromuscular junctional site of action of this agent. The direct correlation between nitrous oxide dose, F-wave amplitude depression, andsurgical immobility suggests the possibility of using F-wave activityto predict the likelihood of anesthetic-induced immobility. However, the mechanism of action of nitrous oxide may differ from that of the potent inhaled agents.

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Documento generato il 30/09/20 alle ore 09:11:16