In:
Anesthesiology, Ovid Technologies (Wolters Kluwer Health), Vol. 93, No. 3 ( 2000-09-01), p. 699-707
Abstract:
The authors hypothesized that if nitric oxide (NO) was a determinant of background cerebrovascular tone, intracarotid infusion of NG-monomethyl-L-arginine (L-NMMA), a NO synthase (NOS) inhibitor, would decrease cerebral blood flow (CBF) and intracarotid L-arginine would reverse its effect. Methods In angiographically normal cerebral hemispheres, after the initial dose-escalation studies (protocol 1), the authors determined the effect of intracarotid L-NMMA (50 mg/min for 5 min) on CBF and mean arterial pressure (MAP) over time (protocol 2). Changes in CBF and MAP were then determined at baseline, during L-NMMA infusion, and after L-NMMA during L-arginine infusion (protocol 3). To investigate effects of higher arterial blood concentrations of L-NMMA, changes in CBF and MAP were assessed at baseline and after a bolus dose of L-NMMA (250 mg/1 min), and vascular reactivity was tested by intracarotid verapamil (1 mg/min, protocol 4). CBF changes were also assessed during induced hypertension with intravenous phenylephrine (protocol 5). Results Infusion of L-NMMA (50 mg/min for 5 min, n = 7, protocol 2) increased MAP by 17% (86 +/- 8 to 100 +/- 11 mmHg; P & lt; 0.0001) and decreased CBF by 20% (45 +/- 8 to 36 +/- 6 ml. 100 g-1. min-1; P & lt; 0.005) for 10 min. Intracarotid l-arginine infusion after L-NMMA (protocol 3) reversed the effect of L-NMMA. Bolus L-NMMA (protocol 4) increased MAP by 20% (80 +/- 11 to 96+/-13 mmHg; P & lt; 0.005), but there was no significant decrease in CBF. Intracarotid verapamil increased CBF by 41% (44+/- 8 to 62 +/- 9 ml. 100 g-1. min-1; P & lt; 0.005). Phenylephrine-induced hypertension increased MAP by 20% (79 +/- 9 to 95 +/- 6 mmHg; P = 0.001) but did not affect CBF. Conclusions The results suggest that intracarotid L-NMMA modestly decreases CBF, and the background tone of cerebral resistance vessels may be relatively insensitive to NOS inhibition by the intraarterial route.
Type of Medium:
Online Resource
ISSN:
0003-3022
DOI:
10.1097/00000542-200009000-00019
Language:
English
Publisher:
Ovid Technologies (Wolters Kluwer Health)
Publication Date:
2000
detail.hit.zdb_id:
2016092-6
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