ANP and BNP have been thoroughly investigated in patients with critical illness. A direct comparison of their dynamics in severe burn injuries has so far not been undertaken. Their amino-terminal biologically inactive fragments (NT-proANP and NT-proBNP) in serum (S-) or in plasma (P-) were assessed daily for 14 days in 50 patients treated in Burn Intensive Care. Their mean age was 41.0 years (range 19-60) and their mean burn size was 30.5 % (range 10-95.5).
Both analytes showed a time dependent pattern with an increase followed by a plateau phase. S-NT-proANP exhibited less variability and reached its maximum days later than P-NT-proBNP. The absolute values and the day-to-day changes for the two NPs correlated only moderately well, suggesting that they are controlled and expressed differently. There was a temporary decrease in the S-NT-proANP/P-NT-proBNP ratio that was most pronounced at days 4 and 5, a considerable inter- and intra-individual variability, and substantial day-to-day fluctuations. P-CRP was a better predictor for P-NT-proBNP than for S-NT-proANP. Both NPs were predicted by Cardiovascular, Respiratory and Renal SOFA scores, although with some differences.
In conclusion, S-NT-proANP and P-NT-proBNP reflect severity of illness similarly in terms of Cardiovascular, Respiratory and Renal SOFA scores, notwithstanding a significantly larger intra-individual variability for P-NT-proBNP. An important difference between the two analytes is that P-NT-proBNP also reflects the systemic trauma response per se.