Improvement of Sleep Apnea in Patients with Chronic Renal Failure Who Undergo Nocturnal Hemodialysis

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Abstract
Sleep apnea is common in patients with chronic renal failure and is not improved by either conventional hemodialysis or peritoneal dialysis. With nocturnal hemodialysis, patients undergo hemodialysis seven nights per week at home, while sleeping. We hypothesized that nocturnal hemodialysis would correct sleep apnea in patients with chronic renal failure because of its greater effectiveness. Fourteen patients who were undergoing conventional hemodialysis for four hours on each of three days per week underwent overnight polysomnography. The patients were then switched to nocturnal hemodialysis for eight hours during each of six or seven nights a week. They underwent polysomnography again 6 to 15 months later on one night when they were undergoing nocturnal hemodialysis and on another night when they were not. The mean (±SD) serum creatinine concentration was significantly lower during the period when the patients were undergoing nocturnal hemodialysis than during the period when they were undergoing conventional hemodialysis (3.9±1.1 vs. 12.8±3.2 mg per deciliter [342±101 vs. 1131±287 μmol per liter], P<0.001). The conversion from conventional hemodialysis to nocturnal hemodialysis was associated with a reduction in the frequency of apnea and hypopnea from 25±25 to 8±8 episodes per hour of sleep (P=0.03). This reduction occurred predominantly in seven patients with sleep apnea, in whom the frequency of episodes fell from 46±19 to 9±9 per hour (P= 0.006), accompanied by increases in the minimal oxygen saturation (from 89.2±1.8 to 94.1±1.6 percent, P=0.005), transcutaneous partial pressure of carbon dioxide (from 38.5±4.3 to 48.3±4.9 mm Hg, P=0.006), and serum bicarbonate concentration (from 23.2±1.8 to 27.8±0.8 mmol per liter, P<0.001). During the period when these seven patients were undergoing nocturnal hemodialysis, the apnea–hypopnea index measured on nights when they were not undergoing nocturnal hemodialysis was greater than that on nights when they were undergoing nocturnal hemodialysis, but it still remained lower than it had been during the period when they were undergoing conventional hemodialysis (P=0.05). Nocturnal hemodialysis corrects sleep apnea associated with chronic renal failure.