Sleep-apnea in patients with end-stage renal disease and objective results.

BACKGROUND: A high prevalence of sleep apnea syndrome (SAS) of 54%-80% has been reported in patients with end-stage renal disease (ESRD). However, these studies were either done in highly selected small patient groups or without objective data using questionnaires only. PATIENTS AND METHODS: We, therefore, studied the prevalence of SAS in a large, unselected group of patients with ESRD. During a 6-month period 77 out of 84 unselected patients with ESRD filled out the sleep apnea questionnaire of the University of Marburg and the Epworth Sleepiness Scale. In 55 of these patients, snoring sounds, heart rate, body position and transcapillary arterial oxygen saturation were recorded with an ambulatory device during the night after hemodialysis. RESULTS: In the questionnaires, 70.3% of the patients reported of an excessive day-time sleepiness, 40.5% of unwillingly falling asleep during the daytime and 35.2% rated their ability to concentrate as decreased. 30.9% (40% male/15% female) of the patients showed evidence of sleep-disordered breathing with an apnea-hypopnea-index (AHI) equal or more than 5/hour. 16.4% (20% male/10% female) of the patients met the diagnostic criteria of SAS. Neither dialysis and biochemical data nor anamnestic parameters measured by the questionnaires correlated significantly with sleep-disordered breathing. CONCLUSION: The prevalence of SAS in this large unselected patient group was not as high as previously reported, but it is still considerably higher than in the general population. Objective recordings are essential, as questionnaires overestimate the prevalence of SAS in patients with ESRD. As SAS promotes hypertension and impairs quality of life, ESRD patients might benefit from a treatment of concomitant SAS.

The vasodilator component of neurogenic inflammation is caused by a special subclass of heat-sensitive nociceptors in the skin of the pig.

1. Skin blood flow has been imaged during stimulation of fine nerve filaments containing small numbers of identified C fibre units. Filaments were dissected from the saphenous nerve of anaesthetized pigs. 2. Stimulation of filaments containing C heat nociceptor units gave small areas of elevated blood flow (average increase 96%, n = 11) restricted to the afferent receptive field. The extent of the areas of raised blood flow was imaged completely for 8 units. The average extent of vasodilatation in the direction of greatest spread was 8 mm and the maximum spread in any unit was 13 mm. 3. Stimulation of C polymodal nociceptor units never caused increases in blood flow in or near their receptive fields. 4. Localized noxious stimuli (55 degrees C or intradermal injection of capsaicin) caused flare extending 7-15 mm in the same skin region. 5. In agreement with the axon reflex model, spread of flare was restricted to the zone innervated by the terminals of single C fibre units. 6. It is concluded that the C heat nociceptor units are the major class of afferent involved in the flare reaction in the skin of the pig. C polymodal nociceptor units do not appear to be involved in flare in this species. The probable situation in human skin, which is also innervated by heat nociceptors, is discussed.