Renal and electrolyte effects of total parenteral nutrition

Effects of short-term (4-14 days) total parenteral nutrition on renal handling of water and electrolytes were studied retrospectively in 24 patients and prospectively in eight patients. There was 33% incidence of hyponatremia and significant reductions in serum creatinine (from 1.03 +/- 0.06 to 0.88 +/- 0.06 mg/dl, p less than 0.001), phosphorus (from 3.2 +/- 0.14 to 2.5 +/- 0.17 mg/dl, p less than 0.005) and uric acid (from 6.09 +/- 0.38 to 3.66 +/- 0.24 mg/dl, p less than 0.001) were observed. Hypouricemia correlated with increased fractional excretion of urate (r = 0.81, p less than 0.05). Hypophosphatemia was associated with increased tubular reabsorption of phosphate. Clearance studies in eight patients showed high urine flow rate (1.7 +/- 0.2 ml/min), osmolar clearance (3.2 +/- 0.7 ml/min), urinary nonelectrolyte, nonurea solute excretion (0.23 +/- 0.14 mmol/min), and negative free water clearance (TcH2O = 1.5 +/- 0.6 ml/min). These data suggest presence of compartmental shifts, expanded extracellular fluid volume, and possible direct effects on renal tubular transport functions during total parenteral nutrition.