Effect of fentanyl on awakening concentration of sevoflurane

This study was designed to determine if fentanyl altered MAC-awake(the end-tidal concentration of sevoflurane associated witheye opening to verbal command) in 30 healthy, ASA I patients.During anaesthesia, no other anaesthetics or drugs were givenwith the exception of sevoflurane. After surgery, end-tidalanaesthetic concentration was maintained constant for at least15 min. If patients failed to respond to command, the end-tidalconcentration was decreased and again maintained constant for15 min. The anaesthetic concentration midway between the valuepermitting the response and that just preventing the responsewas recorded as MAC-awake. Fentanyl was administered at predictedplasma concentrations of 1 and 2 ng mg^–1 using a computer-controlledcontinuous infusion and plasma concentrations of fentanyl weremeasured at the time of MAC-awake measurements. MAC-awake ofthe control group in which fentanyl was not administered wasmean 0.67 (SD 0.12)% or 0.36 (0.03) MAC, being significantlyhigher than that of the fentanyl 2-ng ml^–1 group (0.57(0.09)% or 0.30 (0.04) MAC). In the fentanyl 1 -ng ml^–1group, MAC-awake (0.65 (0.10)% or 0.34 (0.05) MAC) did not differfrom that in the control group. Logistic regression analysisshowed that increasing plasma concentration of fentanyl andincreasing age significantly reduced the MAC-awake of sevoflurane.Because the reduction was very small relative to the overallscatter of the MAC-awake, a low plasma concentration of fentanyldid not significantly reduce the MAC-awake of sevoflurane.     

Melatonin treatment for circadian rhythm sleep disorders

Abstract We administered 1–3 mg melatonin to 11 patients (eight men, three women, aged 16–46 years) with circadian rhythm sleep disorders; nine with delayed sleep phase syndrome and two with non-24-hour sleep-wake syndrome. Sleep logs were recorded throughout the study periods and actigraph and rectal temperature were monitored during treatment periods. Melatonin was administered 1–2 h before the desirable bedtime for expected phase-shifting, or 0.5-1 h before habitual bedtime for gradual advance expecting an hypnotic effect of the melatonin. Melatonin treatments were successful in 6/11 patients. Timing and dose of melatonin administration, together with its pharmacological properties for circadian rhythm sleep disorders, should be further studied.     

Continuous measurement of temperature in non-24 hour sleep-wake syndrome

Abstract The onset of the low temperature (LT) zone which was defined as a period when the rectal temperature was below its daily mean is a convenient circadian phase marker. In this study, we document three cases of non-24 h sleep-wake syndrome in which identification of the LT zone as an evening circadian phase marker contributed to clinical judgments. We found that the LT zone was correlated well with dim light melatonin onset. Moreover, calculating the LT zone was useful in determining phase position in irregular sleep pattern and in determining the timing of bright light therapy.     

Human time production under constant routine

Abstract Previous reports have suggested that human time production of several seconds fluctuates across the day. In order to test whether human time production was controlled by the circadian process or by the homeostatic process, we investigate diurnal fluctuation of human time production under constant routine conditions. We found a common circadian feature in time production tests of 10 s by calculating Z-score for each subject; afternoon troughs and morning peaks. These results may suggest that human time production was modulated by the circadian process.     

Twenty-four hour profiles of four hormones under constant routine

Abstract We studied the circadian features of melatonin, cortisol, thyroid stimulating hormone (TSH), and growth hormone (GH) together with rectal temperature during 36 h continuous forced wakefulness without physical exercise under dim light condition (constant routine). Subjects consisted of four healthy men aged 22–24 years. Blood sampling was conducted hourly, and food and water were supplied bi-hourly during the constant routine. Melatonin, TSH and cortisol displayed clear circadian rhythms under constant routine condition. While GH secretion was unlikely to be driven solely by the circadian pacemaker, its suppression round BT nadir may indicate that GH secretion was modulated to some extent by circadian rhythm.     

Alternation of QRS Morphology and Effect of Radiofrequency Ablation in Idiopathic Ventricular Tachycardia

We performed electrophysiological studies in 13 patients with idiopathic VT and attempted radiofrequency (RF) catheter ablation in 4 of them.Results: VT was induced by programmed stimulation in all patients and the mean cycle length was 363 ± 58 msec. In 8 of 13 patients (62%), alternation of either the cycle length and/or morphology of VT was observed. Transient entrainment was achieved in all patients by rapid pacing from the right ventricular outflow tract so reentry was considered the underlying mechanism of VT. The site of earliest activation (EAS) during VT was located at the apicoposterior portion of the left ventricular septum and used as the target site for RF catheter ablation. Spikelike presystolic activity was detected 20–40 msec prior to the large deflection of the local electrogram in four patients. VT was terminated by a few seconds of RF current in all four patients, but subsequently new VTs with a slightly different morphology were induced in three of them and re-mapping showed a shift of the EAS. After additional RF ablation at the new EAS, VT was no longer induced. No complication was noted and VT did not recur during a follow-up period for a mean of 9.3 ± 5.2 months.Conclusion: RF catheter ablation seems useful and safe for idiopathic VT. The alternation of QRS morphology and the findings at the time of catheter ablation suggest that an alternative pathway or multiple exits may be present in some patients with idiopathic VT, because the change in VT morphology was associated with a shift of the EAS.     

Azosemide-Induced Fetal Wavy Ribs and Their Disappearance after Birth in Rats

ABSTRACT Azosemide produced bent long bones such as wavy ribs in rat fetuses, but these abnormalities could not be found in the adult offspring. In the present study, the morphological sequence from appearance to disappearance of wavy ribs was examined in cartilage-bone double stained specimens of fetuses and pups from mothers treated with azosemide on day 16 of gestation. The first detected change of the skeletal abnormalities was inhibition of bone deposition in the ossification centers of fetuses on day 17 of gestation. A bend first appeared on day 18 of gestation, and consisted of cartilage and portion stained neither alcian blue nor alizarin red S. Ossification began at this stage. From day 19 of gestation onward, ossification progressed toward the ends of the cartilage model including the bent region. The bend disappeared in most pups as bone in the bent region grew on days 10–14 postpartum. The present findings imply that the bend may be caused by difference in growth between cartilaginous and unstained portions, and a surface remodeling of bones may straighten the bend in the subsequent bone growth.