Effects Of Nitrous Oxide Exposure Research Articles

Pro-Con Debate: Nitrous Oxide for Labor Analgesia.

This Pro-Con debate will provide the practitioner with an evidence-based knowledge approach to assist the clinician in determining whether to employ (Pro) or not to employ (Con) this technique in the obstetrical suite for labor analgesia. Nitrous oxide has been used safely in dentistry and medicine for many centuries. However, accumulating preclinical and clinical evidence increasingly suggests previously unrecognized adverse maternal and fetal effects of nitrous oxide, which warrants reconsideration of its use in pregnant women and a more detailed informed consent. Nitrous oxide is associated with metabolic, oxidative, genotoxic, and transgenerational epigenetic effects in animals and humans that may warrant limiting its usefulness in labor. This debate will discuss and review the clinical uses, advantages, and disadvantages of nitrous oxide on occupational effects of nitrous oxide exposure, neuroapoptosis, FDA warning on inhalational anesthetics and the developing brain, research limitations, occupational exposure safety limits, effects on global warming, and potential for diversion.

Effect of Nitrous Oxide Exposure During Surgery on the Homocysteine Concentrations of Children

BACKGROUND Nitrous oxide converts vitamin B12 to its nonmetabolically active form, inhibits methionine synthase, and results in an elevation of plasma total homocysteine (tHcy). The authors investigated the effect of nitrous oxide anesthesia on the plasma tHcy concentrations in children the morning after surgery and whether blood concentrations of folate and vitamins B12 and B6 were associated with any potential increase. METHODS The authors measured plasma tHcy concentrations in 32 children before and 24 h after initial exposure to nitrous oxide (≥ 2 h). Genotype for methylenetetrahydrofolate reductase C677T and blood concentrations of folate, vitamins B12 and B6, and methylmalonic acid were measured before surgery. RESULTS The median age of participants was 11 months (3-126 months). The median (first, third quartile) postoperative plasma tHcy concentration was significantly higher than the preoperative concentration (6.4 [4.7, 8.9] vs. 5.1[4.1, 6.4] μM, P < 0.0001), a 25% (2%, 42%) relative increase. Six of 28 (21%) children with normal, age-appropriate, preexposure plasma tHcy concentrations had postoperative plasma tHcy concentrations greater than the cutoff values. The duration of nitrous oxide exposure was associated positively with the rise in plasma tHcy concentration (R2 = 0.696, P = < 0.001). CONCLUSION Exposure to ≥ 2 h nitrous oxide is associated with a small, albeit statistically significant, increase in postoperative plasma tHcy concentrations the morning after surgery in young children. The clinical significance of this increase is unknown.

Effect of Nitrous Oxide Exposure during Surgery on the Homocysteine Concentrations of Children

Nitrous oxide converts vitamin B12 to its nonmetabolically active form, inhibits methionine synthase, and results in an elevation of plasma total homocysteine (tHcy). The authors investigated the effect of nitrous oxide anesthesia on the plasma tHcy concentrations in children the morning after surgery and whether blood concentrations of folate and vitamins B12 and B6 were associated with any potential increase. The authors measured plasma tHcy concentrations in 32 children before and 24 h after initial exposure to nitrous oxide (≥ 2 h). Genotype for methylenetetrahydrofolate reductase C677T and blood concentrations of folate, vitamins B12 and B6, and methylmalonic acid were measured before surgery. The median age of participants was 11 months (3-126 months). The median (first, third quartile) postoperative plasma tHcy concentration was significantly higher than the preoperative concentration (6.4 [4.7, 8.9] vs. 5.1[4.1, 6.4] μM, P < 0.0001), a 25% (2%, 42%) relative increase. Six of 28 (21%) children with normal, age-appropriate, preexposure plasma tHcy concentrations had postoperative plasma tHcy concentrations greater than the cutoff values. The duration of nitrous oxide exposure was associated positively with the rise in plasma tHcy concentration (R2 = 0.696, P = < 0.001). Exposure to ≥ 2 h nitrous oxide is associated with a small, albeit statistically significant, increase in postoperative plasma tHcy concentrations the morning after surgery in young children. The clinical significance of this increase is unknown.

Notorious Oxide

Notorious Oxide

Shift work, nitrous oxide exposure and subfertility among Swedish midwives.

Shift work and nitrous oxide exposure have both been suspected of having adverse influence on the reproductive performance of health workers. Time to pregnancy has been suggested as a sensitive measure of fecundity in occupationally exposed groups. We investigated the effects of shift work and nitrous oxide exposure on the fertility of Swedish midwives. A questionnaire was mailed to all members of the Swedish Midwives Association who were born 1940 or thereafter, 3985 in all. Eighty-four per cent responded. Detailed information on the number of menstrual cycles required to achieve pregnancy and the working conditions during that period were obtained concerning the most recent, planned pregnancy occurring after 1983. The per cycle probability of becoming pregnant was calculated for each exposure category, and the relation to the unexposed was expressed as fecundability ratios. Midwives who worked two-shift, three-shift rotas, or only nights had reduced fertility compared to those working in the day time. The fecundability ratios were 0.78 (95% confidence interval [CI]: 0.65-0.94), 0.77 (95% CI: 0.60-0.98), and 0.82 (95% CI: 0.64-1.03), respectively, after adjustment for covariates. No effect of nitrous oxide exposure was noted except in the small group reporting that they assisted at more than 30 deliveries per month when nitrous oxide was used (fecundability ratio = 0.64; 95% CI: 0.44-0.95). Shift work and frequent, high occupational exposure to nitrous oxide may have a negative influence on the ability of women to become pregnant.

Effect of nitrous oxide on nickel deprivation in rats.

Because nickel may have a biological function in a pathway in which vitamin B12 is important, an experiment was performed to determine the effects of nitrous oxide exposure in rats deprived of nickel. Exposure to nitrous oxide (N2O) causes inactivation of cobalamin and a subsequent decrease in the vitamin B12-dependent enzymes methionine synthase and methylmalonyl CoA mutase. Rats were assigned to dietary groups of 12 in a factorially arranged experiment with dietary variables of nickel (0 or 1 microgram/g) and vitamin B12 (0 or 50 ng/g). After 6 wk, one-half of the rats from each dietary group were exposed to 50% N2O/50% O2 for 90 min/d for the last 28 d of the experiment. Vitamin B12, N2O, or their interaction had numerous effects; classical findings included N2O-induced reduction in plasma vitamin B12 and decreases in the vitamin B12-dependent enzymes. Inactivation of vitamin B12 by N2O, however, did not exacerbate signs of nickel deprivation, possibly because the rats were able to metabolically compensate to N2O exposure.

Effects of nitrous oxide exposure on Met-enkephalin levels in discrete areas of rat brain

Rat were exposed to 80% nitrous oxide in oxygen for 1 and 18 h. Met-enkephalin levels in the dorsal raphé, medial thalamus, periaqueductal grey, raphé magnus and locus coeruleus were measured by radioimmunoassay in control and treated animals. There was no change in Met-enkephalin levels at either time point in any of the brain areas examined.