Day or night administration of ketamine and pentobarbital differentially affect circadian rhythms of pineal melatonin secretion and locomotor activity in rats.

BACKGROUND: Surgery with general anesthesia disturbs circadian rhythms, which may lead to postoperative sleep disorders and delirium in patients. However, it is unclear how circadian rhythms are affected by different anesthetics administered at different times during the rest-activity cycle. We hypothesized that pentobarbital (an agonist at the γ-aminobutyric acid A receptors) and ketamine (an antagonist at the N-methyl-d-aspartate receptors) would have differential effects on circadian rhythms, and these effects would also be influenced by the time of their administration (the active versus resting phase). METHODS: Rats were divided into 4 groups according to the anesthetic administered (pentobarbital or ketamine) and the timing of intraperitoneal administration (active/night phase or resting/day phase). Using online pineal microdialysis, we analyzed pineal melatonin secretion and locomotor activity rhythms in rats under a light/dark (12/12-hour) cycle for 5 days after anesthesia and microdialysis catheter implantation. The data were analyzed for rhythmicity by cosinor analysis. RESULTS: Ketamine administered during the resting phase produced 65- and 153-minute phase advances, respectively, in melatonin secretion and locomotor activity rhythms on the first day after anesthesia. In contrast, ketamine administered during the active phase produced 43- and 235-minute phase delays. Pentobarbital had no effect on the phase of either melatonin secretion or locomotor activity, irrespective of the timing of administration. When administered during the active phase, both anesthetics decreased the amplitude of melatonin secretion on the day after anesthesia; when administered during the resting phase, however, neither anesthetic affected the amplitude. The amplitude of locomotor activity decreased in all animals for 3 days after anesthesia. CONCLUSION: Ketamine has opposite phase-shifting effects on circadian rhythms according to the time of administration, whereas pentobarbital has no effect. Furthermore, both anesthetics decrease the postoperative amplitude of pineal melatonin secretion if administered during the active, but not the resting, phase of the 24-hour rest-activity cycle.

Successful intubation using a simple fiberoptic assisted laryngoscope for Treacher Collins syndrome.

A fiberoptic-assisted laryngoscope (FLS) (Acoma Medical Industry Co. Ltd., Tokyo, Japan) is a modified Macintosh laryngoscope with a tubular holder into which a fiberoptic bronchoscope can be inserted. We present three cases of Treacher Collins syndrome whose tracheas were successfully intubated with the aid of the FLS. These cases suggest that the FLS may be a useful alternative in the case of difficult pediatric intubation.

Lidocaine concentration in cerebrospinal fluid after epidural administration: a comparison between epidural and combined spinal-epidural anesthesia.

BACKGROUND: In this study, lidocaine concentrations in cerebrospinal fluid (CSF) at different interspaces were measured with or without preceding spinal anesthesia, 10 min after epidural injection of lidocaine, to investigate the effects of preceding meningeal puncture on CSF concentrations of epidurally administered local anesthetic. METHODS: Sixty patients scheduled to receive combined spinal-epidural anesthesia were randomly allocated to receive either spinal anesthesia first (group CSEA) or epidural lidocaine first (group Epi). Each group was divided into three subgroups in which the site of epidural cannulation and spinal tap were separated by one, three, or five interspaces (sets I, II, and III, respectively). CSF was collected from the L4-L5 interspace 10 min after 10 ml lidocaine, 1%, was administered epidurally. In group Epi, CSF was collected after epidural administration of lidocaine and before spinal anesthesia. In group CSEA, spinal anesthesia was performed at the L3-L4 interspace after epidural cannulation and epidural lidocaine was administered postoperatively, after which CSF was sampled. RESULTS: Lidocaine concentrations in CSF were significantly higher with increasing proximity of epidural injection site to CSF collection site in both groups. There were no significant differences in CSF lidocaine concentrations between group CSEA and group Epi in set I, although lidocaine concentrations were significantly higher in group CSEA set II and III patients. CONCLUSION: Lidocaine concentration in CSF was similar with or without preceding meningeal puncture beneath the epidural administration site.

Randomized prospective study comparing the laryngeal tube suction II with the ProSeal laryngeal mask airway in anesthetized and paralyzed patients.

BACKGROUND: The Laryngeal Tube Suction II (LTSII; VBM, Medizintechnik, Sulz, Germany) is a recent revision of the Laryngeal Tube Suction. This study compared insertion and ventilation profiles of the LTSII and the ProSeal Laryngeal Mask Airway (PLMA; Laryngeal Mask Company, Henley-on-Thames, United Kingdom) in anesthetized and paralyzed patients. METHODS: One hundred adult male patients were randomly allocated to an LTSII or PLMArade mark group. The rate of successful insertion, insertion time, airway leak pressure at a cuff pressure of 60 cm H2O, tidal volume during pressure-controlled ventilation, incidence of gas leakage with cuff pressure reduced and with the shaft inclined, position of LTSII under fluoroscopic observation, and postoperative airway morbidity were determined. RESULTS: Insertion was successful in 37 and 48 of 50 patients with LTSII and PLMA, respectively (P = 0.002), with similar insertion times. Tidal volume was lower with LTSII than with PLMA. Median airway leak pressures of LTSII and PLMA were 16 and 21 cm H2O, respectively (P = 0.006). Gas leakage around the cuff was observed more frequently with LTSII than with PLMA when the cuff pressure was reduced or the shaft of the device inclined. The position of LTSII varied significantly and did not statistically correlate with patient height. Postoperative airway-related morbidity was not significantly different. Finally, tracheal misplacement of LTSII occurred in 5 of 50 patients (10%), but ventilation was possible in 4 of them, and misplacement was identified only after fluoroscopic examination was performed. CONCLUSION: Airway management with LTSII is inferior to that with PLMA.