What is the clinical evidence from this study?

Study design: Observational. Population: Healthy human pregnancy. Intervention: N(G)-monomethyl-L-arginine (L-NMMA) vs. Norepinephrine / Nonpregnant controls. Primary outcome: Reduction in hand blood flow (p=0.0003).

What does this research mean for the field?

Increased generation of nitric oxide contributes to the fall in peripheral vascular resistance and maternal vasodilation during healthy human pregnancy. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

February 1, 1997

Nitric oxide-mediated vasodilation in human pregnancy

Key Result

Brachial artery infusion of L-NMMA produced a significantly greater reduction in hand blood flow in pregnant women compared with nonpregnant controls (P=0.0003).

Study Design

Type

Observational

Structured PICO

Does nitric oxide synthase inhibition with L-NMMA affect hand blood flow differently in pregnant versus nonpregnant women?

Population

Three groups of women: nonpregnant, early pregnant (9-15 wk), and late pregnant (36-41 wk).

Intervention

Brachial artery infusion of the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA).

Comparator

Brachial artery infusion of norepinephrine.

Outcome

Change in hand blood flow measured by venous occlusion plethysmography.surrogate

Increased generation of nitric oxide contributes to the fall in peripheral vascular resistance and vasodilation during healthy human pregnancy.

Main Result

p-value: p=0.0003

Limitations

Assumes other vascular beds respond in the same way as the hand

Abstract

The maternal circulation vasodilates during pregnancy. We investigated the contribution of nitric oxide to this vasodilatation. Using venous occlusion plethysmography, we measured the effect of nitric oxide synthase inhibition on hand blood flow during human pregnancy. We compared the response to a brachial artery infusion of the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) with the response to norepinephrine in three groups of women: nonpregnant, early pregnant (9-15 wk), and late pregnant (36-41 wk). Basal hand blood flow increased significantly during late pregnancy compared with nonpregnant and early pregnant subjects (P = 0.007). L-NMMA produced a greater reduction in hand blood flow in both pregnant groups compared with nonpregnant controls (P = 0.0003). Norepinephrine produced an attenuated response in late pregnancy compared with nonpregnant and early pregnant women (P = 0.0029). If other vascular beds respond in the same way as the hand, the gestational increase in vasoconstrictor response to L-NMMA that we observed implicates increased generation of nitric oxide in the fall of peripheral vascular resistance during healthy human pregnancy.

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