To compare
phosphorus intake and renal
phosphorus regulation between thermally injured patients and
multiple trauma patients, 40 consecutive
critically ill patients, 20 with thermal injury and 20 with
multiple trauma, who required enteral
tube feeding were evaluated.
Phosphorus intakes were recorded for 14 days from the initiation of
tube feeding which was started 1 to 3 days postinjury. Serum for determination of
phosphorus concentrations was collected at days 1, 3, 7, and 14 of the study period. A 24-hour urine collection was obtained during the first and second weeks of nutrition support for urinary
phosphorus excretion, fractional excretion of
phosphorus, renal threshold
phosphate concentration, and
phosphorus clearance. Average total daily
phosphorus intake during the 14-day study for thermally injured patients and
multiple trauma patients was 0.99+/-0.26 mmol/kg/d vs 0.58+/-0.21 mmol/kg/d, respectively, p < .001. Serum
phosphorus concentration on the third day of observation was significantly lower in the thermally injured group than those with
multiple trauma (1.9+/-0.8 mg/dL vs 3.0+/-0.8 mg/dL, p < or = .01). A trend toward
hypophosphatemia in the thermally injured group persisted by the seventh day of feeding (2.7+/-1.2 mg/dL vs 3.3+/-0.6 mg/dL, p < or = .04). Differences in urinary
phosphorus excretion was not statistically significant between the thermally injured and
multiple trauma groups (271+/-213 mg/d vs 171+/-181 mg/d for week 1, and 320+/-289 mg/d vs 258+/-184 mg/d for week 2, respectively). Urinary
phosphorus clearance, fractional excretion of
phosphorus, or renal threshold
phosphate concentrations were also not significantly different between thermally injured and
multiple trauma patients. During nutrition support, serum
phosphorus concentrations are lower in thermally injured patients compared with
multiple trauma patients despite receiving a significantly greater intake of
phosphorus. Renal
phosphorus regulation does not significantly contribute to the profound
hypophosphatemia observed in thermally injured patients when compared with
multiple trauma patients during nutrition support.