Caudal analgesia reduces the sevoflurane requirement for LMA removal in anesthetized children

BACKGROUND: An anesthetic state can reduce adverse airway reaction during laryngeal mask airway (LMA) removal in children. However, the anesthetic state has risks of upper airway obstruction or delayed emergence; so possibly less anesthetic depth is advisable. Caudal analgesia reduces the requirement of anesthetic agents for sedation or anesthesia; it is expected to reduce the sevoflurane requirement for LMA removal. Therefore, we determined the EC(50) of sevoflurane for LMA removal with caudal analgesia and compared that to the EC(50) without caudal analgesia. METHODS: Forty-three unpremedicated children aged 1 to 6 yr were enrolled. They were allocated to receive or not to receive caudal block according to their parents' consent. General anesthesia were induced and maintained with sevoflurane and oxygen in air. EC(50) of sevoflurane for a smooth LMA removal with and without caudal analgesia were estimated by the Dixon up-and-down method. The LMA was removed when predetermined end-tidal sevoflurane concentration was achieved, and the sevoflurane concentration of a subsequent patient was determined by the success or failure of the previous patient with 0.2% as the step size; success was defined by the absence of an adverse airway reaction during and after LMA removal. EC(50) of sevoflurane with caudal block, and that without caudal block, were compared by a rank-sum test. RESULTS: The EC(50) of sevoflurane to achieve successful LMA removal in children with caudal block was 1.47%; 1.81% without caudal block. The EC(50) were significantly different between the two groups (P < 0.001). CONCLUSIONS: Caudal analgesia significantly reduced the sevoflurane concentration for a smooth LMA removal in anesthetized childrenope

Discharge patterning in rat olfactory bulb mitral cells in vivo

Here we present a detailed statistical analysis of the discharge characteristics of mitral cells of the main olfactory bulb of urethane‐anesthetized rats. Neurons were recorded from the mitral cell layer, and antidromically identified by stimuli applied to the lateral olfactory tract. All mitral cells displayed repeated, prolonged bursts of action potentials typically lasting >100 sec and separated by similarly long intervals; about half were completely silent between bursts. No such bursting was observed in nonmitral cells recorded in close proximity to mitral cells. Bursts were asynchronous among even adjacent mitral cells. The intraburst activity of most mitral cells showed strong entrainment to the spontaneous respiratory rhythm; similar entrainment was seen in some, but not all nonmitral cells. All mitral cells displayed a peak of excitability at ~25 msec after spikes, as reflected by a peak in the interspike interval distribution and in the corresponding hazard function. About half also showed a peak at about 6 msec, reflecting the common occurrence of doublet spikes. Nonmitral cells showed no such doublet spikes. Bursts typically increased in intensity over the first 20–30 sec of a burst, during which time doublets were rare or absent. After 20–30 sec (in cells that exhibited doublets), doublets occurred frequently for as long as the burst persisted, in trains of up to 10 doublets. The last doublet was followed by an extended relative refractory period the duration of which was independent of train length. In cells that were excited by application of a particular odor, responsiveness was apparently greater during silent periods between bursts than during bursts. Conversely in cells that were inhibited by a particular odor, responsiveness was only apparent when cells were active. Extensive raw (event timing) data from the cells, together with details of those analyses, are provided as supplementary material, freely available for secondary use by others