SummaryThe Pentax-AWS Ò airway scope system is a rigid indirect video laryngoscope with integrated tube guidance. Laryngoscopy and intubation are visualised using a built in LCD monitor which displays the view obtained by a CCD camera mounted in the tip of the laryngoscope. We describe its clinical performance in 320 patients. The Pentax-AWS significantly improved the laryngeal view compared to the Macintosh laryngoscope. Forty-six patients (14%) who were classified as Cormack Lehane glottic view grade 3 or 4 using the Macintosh laryngoscope were classified as grade 1 (45 cases) or 2a (1 case) using the Pentax-AWS airway scope. Laryngeal views measured by percentage of glottic opening score were improved significantly using the Pentax-AWS. Intubation using the Pentax-AWS was successful in all cases, 96% at the first and 4% at the second attempt. The mean (SD) time required to place the tracheal tube was 20 (10) s. The Cormack Lehane grade obtained with the Macintosh blade did not affect the total time to correctly position the tube using the Pentax-AWS. Intubation difficulty scale (score = 0 in 305 patients, score = 1 in 14 and score = 2 in one patient) indicates that tracheal intubation was performed easily in most cases. The Pentax-AWS not only improves the laryngeal view, but its tube guide also facilitates rapid, easy and reliable tracheal intubation under vision. It can be useful in routine anesthesia care and may be advantageous in the situation of unanticipated difficult intubation.
Volatile anesthetics modulate both excitatory and inhibitory synaptic transmission of in vitro rat hippocampal pathways, whereas i.v. anesthetics produce more specific actions on inhibitory synaptic events. These results provide further support the idea that general anesthetics produce drug-specific and distinctive effects on different pathways in the central nervous system.
It has been suggested that volatile anaesthetics enhance synaptic inhibition via gamma-aminobutyric acid (GABA) in the central nervous system. We have examined the effects of sevoflurane on GABAA and GABAB receptors in rat hippocampus in vitro. Extracellular recordings were used to record field potentials in rat CA1 pyramidal neurones of transverse hippocampal slices, stimulated electrically via stratum radiatum input. Sevoflurane 0.4-5.0 vol% decreased the amplitudes of population spikes (PS) of CA1 neurones in a concentration-dependent (calculated ED50 = 6.31 vol%) and reversible manner. The GABAA antagonist, bicuculline methiodide 5 x 10(-5) mol litre-1, induced oscillations (multiple spikes) and blocked the inhibitory actions of sevoflurane in the initial component (up to 24.8 ms) of the oscillation. The latter portion of the oscillation (greater than 24.8 ms) was depressed by sevoflurane. The GABAB antagonist, phaclofen 5 x 10(-4) mol litre-1 partially blocked the effects of sevoflurane on the latter portion of the bicuculline-induced oscillation. Sevoflurane 2.0 vol% significantly enhanced paired-pulse (PS2/PS1) facilitation (from 128.4% to 155.5% at an inter-stimulus interval of 37.9 ms); this enhancement was blocked by phaclofen. Stimulus-response relationships revealed that 2.0 vol% sevoflurane increased the intensity of threshold for PS generation to 109.8% of control. Both the GABAA agonist, muscimol 2 x 10(-5) mol litre-1 and the GABAB agonist, (+/-)-baclofen 10(-5) mol litre-1, potentiated the effects of sevoflurane. Sevoflurane enhanced thresholds by 137.1% and 138.5% of control in the presence of muscimol and (+/-)-baclofen, respectively. The results demonstrate that sevoflurane at clinical concentrations activated both GABAA- and GABAB-mediated inhibitions in area CA1 of the hippocampus, and that sevoflurane and GABA agonists (muscimol and baclofen) acted on different domains on the GABAA and GABAB receptors, respectively.
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