Increased asymmetric dimethylarginine levels in severe transient tachypnea of the newborn.

Objective: Nitric oxide (NO) is synthesized by NO synthase (NOS), and asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of NOS. We aimed to investigate l-arginine and ADMA levels in transient tachypnea of the newborn (TTN) and their relationship with systolic pulmonary artery pressure (PAP) and disease severity.

Study Design: Infants born at ⩾35 weeks gestational age with clinical signs and chest X-ray findings consistent with TTN were enrolled; controls were recruited at the same time. l-arginine and ADMA levels were measured at 12 to 24 h (first samples) and at 48 to 72 h (second samples). Systolic PAP was evaluated on the second day. Patients were divided according to the duration of tachypnea and designated as group A (duration ⩽72 h) and group B (duration >72 h).

Results: In the first samples, the ADMA levels were significantly higher in patients with TTN compared with controls (P<0.001). In the second samples, the ADMA levels were significantly higher in group B compared with that in group A (P=0.019). In group A patients, the second ADMA levels were significantly lower compared with that in the first samples (P<0.001), whereas the second ADMA levels remained unchanged compared with the first samples in group B. Systolic PAP values were significantly higher in group B compared with that in group A patients (P=0.033).

Conclusion: Increased ADMA concentration may reduce NO synthesis, leading to increased PAP and thus longer duration of tachypnea.