Objective: Plasma soluble thrombomodulin level reflects endothelial damage. The plasma thrombomodulin level at birth is increased in asphyxiated full-term infants. There is no report of plasma thrombomodulin level in premature infants. To determine the thrombomodulin level in premature infants and whether it might reflect endothelial damage, we examined the plasma thrombomodulin level in very low birthweight (VLBW) infants at birth.
Methods: Forty-five VLBW infants, of whom 14 had perinatal asphyxia complications, were recruited. As a control, 50 full-term infants without complications were also studied. Plasma thrombomodulin concentration, pH, base deficit, serum creatinine and D-dimer concentration, platelet count and fibrinogen concentration were measured within 1 hour after birth.
Results: There were significant differences in plasma pH, creatinine concentration, platelet count, antithrombin III activity and D-dimer concentration between VLBW infants and full-term infants. Plasma thrombomodulin concentration (39.0 (16.6-93.7) vs 27.0 (16.6-39.1) microg/L, p < 0.0001) and plasma thrombomodulin-to-serum creatinine ratio (0.82 (0.19-2.65) vs 0.47 (0.24-0.70) microg/micromol, p < 0.0001) were significantly higher in VLBW infants than those in full-term infants. By univariate analyses for all neonates, there were significant relations between plasma thrombomodulin concentration and gestational age, birthweight, plasma pH, creatinine concentration, platelet count and antithrombin III activity. A stepwise multiple linear regression model using the above variables as dependent factors showed only birthweight contributed significantly to plasma thrombomodulin concentration (plasma thrombomodulin concentration (microg/l) = 45.677-0.006 (birthweight; g), r2 = 0.323, p < 0.0001, n = 94). Plasma thrombomodulin concentration and plasma thrombomodulin-to -serum creatinine ratio in VLBW infants with asphyxia were higher than in those without asphyxia, but not significantly different (43.2 +/- 17.7 vs 38.3 +/- 8.5 microg/l and 0.92 +/- 0.60 vs 0.83 +/- 0.37 microg/micromol).
Conclusion: Plasma thrombomodulin level in VLBW infants shows a high value at birth, and we consider the main factor responsible for this elevation may be endothelial damage or low clearance rate of thrombomodulin, which may be related to early gestational age.