1. The Ames test, which identifies chemicals that act as mutagens and carcinogens, is negative for isoflurane, desflurane, sevoflurane, and nitrous oxide.
2. Volatile anesthetics can be teratogenic in animals, but none of them has been shown to be teratogenic in humans.
3. Nitrous oxide decreases the activity of vitamin B₁₂ –dependent enzymes (methionine synthetase, thymidylate synthetase) by irreversible oxidation of the cobalt atom of vitamin B₁₂ by nitrous oxide.
   1. Administration of 70% nitrous oxide results in 50% inactivation of methionine synthetase in 46 minutes.
   2. There is concern these changes might have an effect on a rapidly developing embryo or fetus because methionine synthetase and thymidylate synthetase are involved in the formation of myelin and DNA, respectively.
   3. A sensory neuropathy that is often combined with signs of posterior lateral spinal cord degenerations has been described in humans who chronically inhaled nitrous oxide for recreational use.
4. Uterine smooth muscle tone is diminished by volatile anesthetics in similar fashion (dose dependent) to the effects of volatile anesthetics on vascular smooth muscle.
   1. Uterine relaxation can be troubling at concentrations of volatile anesthetics above 1 MAC and may delay the onset time of newborn respiration. Consequently, for an urgent cesarean section, a common technique is general anesthesia with low concentrations of the volatile anesthetic (0.5–0.75 MAC) combined with nitrous oxide.
   2. Uterine relaxation may be desirable when it is necessary to remove a retained placenta.
5. No causal relationship has been shown between exposure to waste anesthetic gases regardless of the presence or absence of scavenging systems and adverse health effects. Despite the unproven influence of trace concentrations of volatile anesthetics on fetal development and spontaneous abortions, the use of scavengering systems is common. The National Institute for Occupational Safety and Health recommends exposure levels of 25 parts per million for nitrous oxide and 2 parts per million for halogenated anesthetics.

Inhaled Anesthetics

1. Pharmacokinetic Principles
2. Clinical Overview of Current Inhaled Anesthetics
3. Neuropharmacology of Inhaled Anesthetics
4. The Circulatory System
5. The Pulmonary System
6. Hepatic Effects
7. Neuromuscular System and Malignant Hyperthermia
8. Genetic Effects, Obstetric use, and Effects on Fetal Development
9. Anesthetic Degradation by Carbon Dioxide Absorbers
10. Anesthetic Metabolism
11. Clinical Utility of Volatile Anesthetics
12. Pharmacoeconomics and Value-Based Decisions