Body sodium and potassium in men with spinal cord injury.

As part of a broad study on the body composition of patients with extensive muscular paralysis, total body water (TBW), extracellular fluid (ECF), exchangeable sodium (Nae), and exchangeable potassium (Ke) were measured in 22 paraplegic and 23 quadriplegic patients. These data were compared with similar measurements obtained on 12 healthy men. Patients with spinal cord injury (SCI) showed a drastic loss of K+, more pronounced in quadriplegic than in paraplegic patients. Sodium was retained and associated with a relatively increased ECF volume. The high correlation between TBW and total "exchangeable base" (Nae + Ke) reported in previous studies on healthy subjects and patients with varied diseases was also observed in SCI patients. Analysis of the present data suggests that the physiologic mechanism which maintains the tonicity of the body fluids is not affected in SCI. This analysis does not provide any clue as to the identification of the mechanism that might explain the relative expansion of the extracellular space in the presence of K+ depletion.