Birth asphyxia impairs brain blood flow autoregulation (BBF-A). Inappropriate NO-synthesis of vasodilator NO may be important in this respect. We investigated if NO-synthase-inhibition by N-ω-nitro-L-arginin (NLA) could restore BBF-A after HI. Severe HI was induced in 16 newborn lambs and brain blood flow (carotid flow [mL/min]: Qcar) and aortic blood pressure[mmHg]: Pao) were measured over a 30 min period before HI (pre-HI), 0-30 min after completion of HI (0-30 post-HI) and from 60 to 120 min post-HI (60-120 post-HI). Immediately after completion of HI, 5 lambs received a placebo(CONT), 6 a low dose NLA (10 mg/kg/iv: NLA-10) and 5 high dose NLA (40 mg/kg/iv: NLA-40).

Results: Pre-HI, all groups showed BBF-A (Fig). 0-30 post-HI, all groups lacked BBF-A. 60-120 post-HI BBF-A was restored in NLA-10 and NLA-40, but not in CONT (Fig). 60-120 post-HI Pao was higher in both NLA-groups than in CONT (74 ± 11 and 82 ± 14 vs 64 ± 10 mmHg, p<0.05), but blood gasses did not differ.

figure 1

Fig 1

Conclusions: Severe HI in newborn lambs induced impairment of BBF-A. Even low-dose NO-synthase inhibition post-HI restored BBF-A, suggesting a role for NO-induced vasodilation in the impairment of BBF-A after birth asphyxia.