[Application of B type natriuretic peptide in fluid therapy after major abdominal operations].

Objective: To evaluate the values of serum level of B type natriuretic peptide level (BNP) in the prediction of fluid overloading after major abdominal operations.

Methods: The levels of BNP were dynamically monitored in 105 patients during peri-operative period from February 2009 to November 2010. Then comparisons were made with age and the volume of positive fluid balance.

Results: A post-operative elevation of BNP was observed in all cases. Among them, the peak level of BNP exceeded 100 ng/L in 32 patients while a normal peak level of BNP was found in 73 patients. Congestive heart failure (CHF) was diagnosed in 5 patients. At every single time point, the volume of positive fluid balance showed no significant difference among the peak level of BNP < 100 ng/L, ≥ 100 ng/L and CHF patients (all P > 0.05). In the group of peak level of BNP ≥ 100 ng/L, the patients received post-operative diuretic and the urine volume increased significantly [(280 ± 55) ml/h vs (82 ± 22) ml/h, P < 0.05]. However, in the group of the peak level of BNP < 100 ng/L, the urine volume showed no difference after dosing of diuretic [(95 ± 18) ml/h vs (89 ± 24) ml/h, P > 0.05]. Single variance analysis showed that the elevated level of BNP was associated with age and concurrent cardiopulmonary diseases (R = 0.87, P = 0.006) but not with the volume of positive fluid balance (R = 0.43, P = 0.080). And multiple variance analysis showed the similar results (R = 0.59, P = 0.020, R = 0.38, P = 0.120). In all cases, the levels of BNP peaked at 12 hours post-operation. However, body weight and the volume of positive fluid balance peaked at 18 - 24 hours post-operation.

Conclusion: The post-operative level of BNP is associated with age. And a highly elevated level of BNP may predict the occurrence of fluid overloading. An early peak of BNP value may be used as a cut-off point of positive and negative fluid balances.