Are volatile anesthetics neuroprotective or neurotoxic?

More than 20 millions of patients each year have surgeries in the USA. The majority of these surgeries are performed under general anesthesia. About 80% of them receive volatile anesthetics as their primary anesthetics [1]. Since the first use of ether, a volatile anesthetic, in 1842, volatile anesthetics have be the major class of general anesthetics used in the clinical practice for near 160 years.Although it is still controversial among the experts, it is generally accepted that general anesthesia minimally includes the following components: unconsciousness, insensateness, analgesia and amnesia. Many experts will also add muscle relaxation and bluntness of cardiovascular response to surgical stimulation into the components of general anesthesia. Volatile anesthetics, unlike most intravenous anesthetics, have pharmacological properties to provide all components of general anesthesia [2]. Thus, volatile anesthetics are full general anesthetics and, theoretically, single volatile anesthetic can be used to provide a patient with full general anesthesia for surgery. In addition, volatile anesthetics take effects very quickly. Most patients anesthetized by these drugs recover smoothly and quickly. With the aid of modern equipment, their use is very easy and their concentrations can be accurately monitored. For these reasons, volatile anesthetics have been popular drugs used in clinical practice. Modern volatile anesthetics that are used in the USA include isoflurane (CHF2-O-CHCl-CF3), sevoflurane (CH2F-O-CH-(CF3)2) and desflurane (CHF2-O-CHF-CF3). Halothane (CF3-CHBrCl) was used clinically for more than 40 years and started to be phased out during 1990s as newer volatile anesthetics become popular. All of these volatile anesthetics are halogenated hydrocarbons.In addition to the anesthetic properties, volatile anesthetics have been thought to have neuroprotective effects for a long time [3,4]. Although the potential for volatile anesthetics to induce cell injury has be