Monitoring Microvascular Reactivity: (II) - Short-Term Effect of Nitrous-Oxide on the Peripheral Microcirculation in Humans.

A study was carried out to monitor directly the short-term effects of N(2)O/O(2) inhalation-sedation on the peripheral microcirculation in healthy human subjects in a simulated dental setting. The inhalation of 40% N(2)O and 60% O(2) led to a small but significant mean percent decrease (-6.89 +/- 1.2 SEM) in relative vessel diameter in the nailfold capillaries, for the entire N(2)O-breathing period. Individual vessels showed a marked constriction (-31.7% +/- 4.4 SEM, mean maximal decrease); the time to this maximum constriction varied with the individual vessels. This constriction could not be attributed to changes in oxygen or carbon dioxide levels in the alveolar gas, or to changes in heart rate, systolic blood pressure, respiratory rate or temperature. Further studies are indicated to determine whether this effect is sustained with long term administration, and whether it is clinically significant, especially in those patients with acquired cardiac disease or those taking vasoactive drugs.