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June 1964

Acute Encephalopathy Occurring During Hemodialysis: The Reverse Urea Effect

Arch Intern Med. 1964;113(6):877-880. doi:10.1001/archinte.1964.00280120077014

Although hemodialysis is generally safe and effective in treating acute renal failure, symptoms of headache, agitation, and confusion occasionally develop.1 We have recently observed three patients who developed a severe encephalopathy during hemodialysis. In all three cases neurological deterioration coincided with rapid reduction of blood urea, and we postulate that the blood-brain barrier prevented a parallel and equally rapid reduction of brain urea. This produced an osmotic differential between brain and blood causing movement of water into brain with resultant water intoxication and brain swelling.

Report of Cases 

Case 1.  —A 14-year-old boy (UWH 151-157) with a three-year history of chronic renal failure was referred to the University of Washington Hospital for hemodialysis.On admission he appeared chronically ill. Funduscopic examination revealed arteriovenous nicking, tortuous vessels, and arteriolar narrowing. He had a rachitic rosary, and his heart was enlarged to percussion. His blood pressure was 150/110 mm Hg, and