Calciuretic effect of cyclic versus continuous total parenteral nutrition.
Metabolic bone disease has been reported in patients receiving long-term cyclic administration of total parenteral nutrition (TPN). The exact etiology of this disturbance in mineral homeostasis has not been identified, however many of these patients are markedly hypercalciuric and in negative calcium balance. We have studied the effects of cyclical versus continuous infusion of nutrients on urinary calcium losses in a group of patients beginning a program of long-term home TPN. Cyclic TPN, when administered over either 18 or 12 hours, significantly increased daily urinary calcium excretion compared to continuous 24-h TPN infusion by 19 and 28%, respectively. During cyclic TPN, frank negative calcium balance was observed in 3 of 5 patients studied compared to 2 of 5 patients during continuous TPN. The pattern of urinary calcium loss during cyclic TPN was such that approximately 80% of the daily urinary calcium losses occurred during the 12 hours of TPN infusion. Cyclic administration of TPN increased the urinary calcium losses in all patients suggesting that an intermittent TPN infusion schedule, as typically utilized in home TPN programs, increases the risk of developing negative calcium balance, at least during the early phase of cyclic TPN administration.