Word recall correlates with sleep cycles in elderly subjects.

Morning recall of words presented before sleep was studied in relation to intervening night sleep measures in elderly subjects. Night sleep of 30 elderly subjects aged 61-75 years was recorded. Before sleep, subjects were presented with a list of paired non-related words and cued recall was asked immediately after the morning awakening. Recall positively correlated with average duration of NREM/REM cycles, and with the proportion of time spent in cycles (TCT) over total sleep time (TST). No significant correlations were found with other sleep or wake measures. These results suggest the importance of sleep structure for sleep-related memory processes in elderly adults.

A new technique for total hepatectomy in the pig for testing liver support devices.

BACKGROUND: A large animal model of total hepatectomy is suitable to test the efficacy of any system designed to support patients in hepatic coma. The models previously described in the pig entail a significant degree of surgical trauma, which might alter the evolution of the ensuring hepatic failure and compromise the reproducibility of the model. METHODS: Twenty-eight pigs underwent a total hepatectomy according to a new technique. A model was considered satisfactory when it required no blood transfusions and when hematologic and hemodynamic parameters determined before, during, and until 4 hours after hepatectomy showed no significant variations. Moreover, to revive the pattern of hepatic coma produced in the anhepatic model, 7 pigs were monitored until brain death occurred. RESULTS: Twenty-five pigs (89%) underwent a smooth total hepatectomy with minimal variations of the selected parameters. They constituted a highly homogeneous group. Survival of the 7 pigs, followed up until brain death occurred, ranged from 625 to 1595 minutes (mean 1013.57 minutes). The animals remained stable until a few hours before brain death, an event heralded by a final sharp increase of the serum ammonia level and by a well-evident decline of both arterial pressure and liver-dependent clotting factors. CONCLUSIONS: This technique of total hepatectomy allows the construction of a reproducible model of anhepaty suitable to test the efficacy of any system conceived to temporarily replace hepatic functions.

Sleep stages preceding spontaneous awakenings in the elderly.

Spontaneous awakenings from sleep were studied in a group of 21 elderly subjects (mean age 69.29+/-3.02 years) free of neurological and somatic diseases. The prevalence of awakenings and the duration of waking bouts were analyzed with regard to the prior sleep state. The results showed an increased frequency of awakenings during Stage 2 NREM in the elderly, who wake out of Stage 2 NREM no less frequently than out of REM sleep. This trend is different from that observed in younger subjects (babies and young adults), where a clear prevalence of REM sleep awakenings has been reported. The duration of Stage 2 interrupted by awakening was shorter than Stage 2 followed by sleep. The duration of waking bouts did not differ according to the preceding sleep stage. It is suggested that the relative inability to sustain Stage 2 may be a mechanism which contributes to the difficulty of sleep maintenance in the elderly.

A simple method for the quantitative description of sleep microstructure.

A simple method for the quantitative description of sleep microstructure is proposed. This method is based on the computation of descriptors which provide a normalized measure of how the amplitude of the activity in a frequency band differs, at a given instant, from its background. The use of these descriptors makes it possible to identify epochs of transient increase in band activity, to measure their length, and to measure the time distance between two successive epochs.

Slow wave sleep (SWS) distribution across night sleep episode in the elderly.

Slow wave sleep (SWS) distribution across night sleep was shown to be different between infants and young adults. The present research aimed at studying the SWS distribution across night sleep in elderly subjects. Nine healthy elderly subjects, 61-71 years old, were submitted to nocturnal polygraphic sleep recording. Eleven young subjects, 21-23 years old, were the control group. Recordings were visually analyzed according to Rechtschaffen and Kales rules; the method proposed by Webb and Dreblow was used for scoring SWS. An NREM-REM cycle was defined as a sequence of NREM and REM sleep not interrupted by a waking period longer than 15 minutes. SWS percentage was calculated for each successive NREM episode. No significant association between SWS percentage and cycle rank was shown in elderly subjects, whereas a significant association was observed in the young ones. This kind of SWS distribution could be interpreted as reflecting the restructuring of internal organization of sleep in the elderly.

A quantitative study of daytime sleepiness induced by carbamazepine and add-on vigabatrin in epileptic patients.

INTRODUCTION: The clinical relevance of daytime sleepiness associated with carbamazepine (CBZ) and vigabatrin (VGB) was objectively assessed by the multiple sleep latency test (MSLT) and nocturnal sleep recordings. MATERIAL AND METHODS: Twenty-six patients with partial epilepsy and mean monthly seizure frequency of 4, aged 18 to 48 years, receiving chronic monotherapy with CBZ and subsequent VGB addition for 2 months (14 patients), were compared with a group of healthy subjects. Subjective daytime sleepiness was complained by 13 patients on CBZ monotherapy and 9 patients during VGB add-on treatment. RESULTS: No differences in nocturnal sleep parameters, but significantly shorter daytime sleep latencies at the MSLT, were detected in CBZ-treated patients as compared with healthy controls. Addition of VGB therapy did not further enhance objective daytime sleepiness. CONCLUSION: Some sleepiness occurs in chronically CBZ-treated epileptic patients, which can be objectively measured by the MSLT, but it is not aggravated by add-on VGB.

Alteration of cardiac function in patients with temporal lobe epilepsy: different roles of EEG-ECG monitoring and spectral analysis of RR variability.

PURPOSE: Because several reports have described the relation between epilepsy and cardiac arrhythmias and suggest that changes in autonomic neural control of the heart could be involved in the pathogenesis of sudden unexplained death in patients with epilepsy, the aim of this study was to evaluate cardiac function in patients with temporal lobe epilepsy. METHODS: Sixty-five patients with epilepsy were evaluated by simultaneous ambulatory 24-h EEG-ECG monitoring, and in 30 of these, power spectral analysis of relative-risk (RR) variability also was carried out, both in the supine position and in a passive tilt position at 60 degrees. The power spectrum of RR variability, the two major spectral components detectable at low frequency (LF) and at high frequency (HF), respectively, and the LF/HF ratio were calculated. RESULTS: By EEG-ECG monitoring, we recorded six partial seizures, and in four cases, discharges were associated with sinus tachycardia. However, interictally the occurrence of ventricular and supraventricular arrhythmias was not different from that in normal subjects. The spectral analysis of RR variability, on the other hand, demonstrated in patients with epilepsy a significant decrease in the total RR variability and in both of its components (LF and HF) in the supine position, and of the LF/HF ratio in orthostatic position. CONCLUSIONS: These findings suggest that the spectral analysis of RR variability may detect disorders of autonomic cardiac control in patients with epilepsy, even in the absence of abnormal findings during ECG monitoring. This alteration, which is more severe in cases with right EEG focus, could play a role in the pathogenesis of cardiac arrhythmias.