Biologic Effects of Nitrous Oxide

Abstract

Nitrous oxide is the longest serving member of the anesthesiologist's pharmacologic armamentarium but remains a source of controversy because of fears over its adverse effects. Recently, the Evaluation of Nitrous oxide In a Gas Mixture for Anaesthesia (ENIGMA) trial reported that nitrous oxide use increases postoperative complications; further preclinical reports have suggested that nitrous oxide may contribute to neurocognitive dysfunction in the young and elderly. Therefore, nitrous oxide's longevity in anesthetic practice is under threat. In this article, the authors discuss the evidence for the putative toxicity of nitrous oxide, from either patient or occupational exposure, within the context of the mechanism of nitrous oxide's action. Although it would seem prudent to avoid nitrous oxide in certain vulnerable populations, current evidence in support of a more widespread prescription from clinical practice is unconvincing.

Effects of Midazolam and Nitrous Oxide on Endocrine and Metabolic Measurements in Children

“…In these studies, midazolam reduced the autonomic and hormonal responses measured as a reduction in catecholamine, cortisol, and insulin levels [30,31,32]. In contrast, N 2 O is known to have a symphaticomimetic effect [19], which could explain the significantly higher norepinephrine levels found as compared to midazolam.…”

“…N 2 O primarily affects the central nervous system, and its analgesic action is dependent on the inhibition of supraspinal GABA receptors and the activation of spinal GABA receptors [19]. N 2 O is known to have a symphaticomimetic effect releasing norepinephrine and epinephrine [19]. …”

Managing Painful Procedures in Children With Cancer

“…40,41 More serious complications such as inhibition of the methionine pathway, hematological, neurological, and/or myocardial injury were associated with prolonged N 2 O use (>6 h) and higher concentrations (>70% N 2 O in oxygen). 43 Serious side effects are not found in the review of studies using N 2 O for procedures that involve short-term sedation. Adequate room ventilation and effective scavenging systems are required when using N 2 O to reduce exposure to ambient gas.…”

Health hazard evaluation report: evaluation of nitrous oxide exposure at a dental center.

“…The animal data suggests that doses of 500 ppm are a threshold for this toxicity (i.e., 10 times the United States' OELs). Most of the occupational exposure studies regarding anesthetic waste gases were performed in the prescavenging era in operating rooms [Sanders et al 2008]. In this center, employees reported always using scavenging equipment and followed safe work practices to reduce their N 2 O exposure.…”