a. Inhalation Agents. Inhalation anesthetic agents are gases or volatile liquids.
These substances are often mixed with oxygen and the patient is allowed to breathe the
mixture. After a period, a sufficient level of the anesthetic agent is obtained in the blood
and anesthesia is produced. In general, anesthesia can be well controlled with these
agents because the concentration of the agent in the blood can be increased or
decreased easily by either increasing or decreasing the concentration of the agent in
the air the patient is breathing. It is relatively uncommon for a patient to have an allergic
reaction to one of the inhalation general anesthetic agents. However, the side effects of
some of these agents can be quite serious. There is rapid recovery for the patient when
this type of agent is used. That is, when the patient is no longer allowed to breathe the
agent, the depression of the central nervous system quickly disappears.
Nitrous oxide. Nitrous oxide is a gas supplied in blue metal cylinders.
Nitrous oxide is commonly referred to as laughing gas. Although nitrous oxide is a safe
general anesthetic, it is relatively weak in terms of producing anesthesia and muscle
relaxation. Consequently, nitrous oxide is often used in conjunction with other agents.
Nitrous oxide is often used in dental surgery and in obstetrical practice during delivery.
Halothane (Fluothane). Halothane is a volatile liquid inhalation
anesthetic. It is one of the most widely used general anesthetics. Since halothane
does not produce potent analgesia and muscle relaxation, other agents are sometimes
administered with halothane on an as-needed basis. Halothane has popularity because
it is nonexplosive, rapid acting, pleasant smelling, and is compatible with other drugs.
Enflurane (Erthrane. Enflurane is a volatile liquid inhalation
anesthetic with many of the properties of halothane. It produces greater muscle
relaxation than halothane, but like halothane, it is a poor analgesic.
b. Intravenous Agents. Intravenous general anesthetics are sterile solutions
intended to be administered into the patient's circulatory system. Intravenous
anesthetic agents do produce loss of consciousness; however, most of these agents
lack the ability to produce complete analgesia. In general, the level of anesthesia is
more difficult to control with intravenous anesthetics than with inhalation anesthetics.
Thiopental sodium (Pentothal) Thiopental sodium is an ultrashort
acting barbiturate. That is, this agent acts very quickly to produce anesthesia.
Sometimes this agent is used alone for minor surgical procedures. In other cases, the
drug is used to initiate anesthesia. Then, other anesthetic agents are used to maintain
the anesthesia. Thiopental sodium is a NOTE Q item. That is, it is a controlled
Fentanyl (Sublimaze) and droperidol (Innovar). This agent is an
intravenously administered product, which combines the narcotic analgesic effect of
fentanyl with the sedative and antiemetic effects of droperidol. This agent produces a
semiconscious state in the patient, and it is used in types of surgery in which the
surgeon needs the cooperation of the patient. Innovar is usually used in combination