Human plasma DNP level after severe brain injury.

Objective: To determine the relationship between DNP level after human severe brain injury and hyponatremia as well as isorrhea.

Methods: The peripheral venous plasma as control was collected from 8 volunteers. The peripheral venous plasma from 14 severe brain injury patients were collected in the 1, 3, 7 days after injury. Radioimmunoassay was used to detect the DNP concentration. Meanwhile, daily plasma and urine electrolytes, osmotic pressure as well as 24 h liquid intake and output volume were detected.

Results: The normal adult human plasma DNP level was 62.46 pg/ml+/-27.56 pg/ml. In the experimental group, the plasma DNP levels were higher from day 1 to day 3 in 8 of the 14 patients than those in the control group (P(1)=0.05, P(3)=0.03). Negative fluid balance occurred in 8 patients and hyponatremia in 7 patients. The increase of plasma DNP level was significantly correlated with the development of a negative fluid balance (r =-0.69, P<0.01) and hyponatremia (chi(2) =4.38, P<0.05).

Conclusions: The increase of plasma DNP level is accompanied by the enhancement of natriuretic and diuretic responses in severe brain-injured patients, which is associated with the development of a negative fluid balance and hyponatremia after brain injury.