NITRIC OXIDE (NO) BLOCKADE PRESERVES THE UPPER LIMIT OF CEREBRAL BLOOD FLOW(CBF) AUTOREGULATION IN THE NEWBORN PIGLETS WITH GROUP B STREPTOCOCCAL MENINGITIS. • 449

Abstract

Group B Streptococcus (GBS) meningitis in the neonate may cause early cerebral hyperemia possibly mediated by NO. We hypothesized that L-Nitroarginine (LNA), a nitric oxide synthase blocker may protect CBF autoregulation at the upper limit in GBS treated piglets. Two groups of sedated piglets (1-5 days old) were studied. The GBS group (n=7) had cerebrointraventricular injection of 0.5 ml heat killed, unencapsulated GBS(109cfu) whereas the GBS + LNA group (n=9) had GBS (109cfu) + 300 mg/kg of LNA. CBF was measured by radioactive microspheres over a range of normotension (MABP range = 50-90 mmHg) and hypertension (MABP range = 90 - 125 mmHg) induced by inflating balloon tipped catheters placed at the descending aorta, at 5 time points: 15 min pre- (baseline) and post injection of GBS with or without LNA and during normo- and hypertension. Using linear regression analysis of CBF (ml/min/100g) vs cerebral perfusion pressure (CPP), the GBS group showed a pressure passive CBF (p=0.0404, r=0.5167). In contrast, the GBS+ LNA group had CBF held constant at CPP 50-125 mmHg (r=0.16, p=0.4). Thus, NO inhibition restores CBF autoregulation at the upper limit and may reduce the amount of cerebral hyperemia in GBS meningitis.Figure