Insomnia on dialysis nights: the beneficial effects of cool dialysate.

Background: Hemodialysis (HD) induces physiological changes that may affect the ability to dissipate heat and adversely affect sleep on the nights following treatment. We studied the effects of altering dialysate temperature on polysomnographic measures of nocturnal sleep and the time course of proximal skin temperature.

Methods: The sample included seven stable HD patients. The three-phase randomized trial was conducted in a research facility. After one acclimatization night, subjects were readmitted in the evening on two additional occasions for 42 hours and received HD the next morning in the warm condition (dialysate--37 degrees C) and cool condition (dialysate--35 degrees C) in random order. Continuous proximal skin temperature (axillary, Tax) and polysomnographic measures of sleep were recorded the nights before and after HD was administered.

Results: Highly significant findings included that the course of Tax was markedly affected by the interaction of time and condition. In addition, there was a greater drop of Tax in the early morning following the warm condition than during the baseline nights or in the cool condition. Logistic regression indicated that the odds for the occurrence of sleep and its deeper stages were strongly and positively associated with Tax. Time of sleep onset was earlier in the cool condition (p = 0.032) with trends toward longer total sleep times (p = 0.090) and shorter REM latencies (p = 0.088).

Conclusions: These observations suggest that the use of cool dialysate during HD may improve nocturnal sleep the night following treatment by decreasing sympathetic activation and sustaining the normally elevated nocturnal skin temperature until later into the morning hours.