CHAPTER 15 Nervous System Drugs^277
general anesthetic needed, reduce possible post-anesthetic nausea and vomiting,
minimize the disturbance of organ function, and increase recovery from anes-
thesia with fewer adverse reactions.
The night before the surgery, the patient is given a hypnotic to assist with a
good night’s sleep. On the day of the surgery, premedication may be given to the
patient about one hour before surgery. Premedication typically consists of two
medications. One is a benzodiazepine such as lorazepan (Ativan). This medica-
tion sedates and decreases anxiety. The other is an anticholinergic such as
atropine to decrease secretions. A short-acting barbiturate such as thiopental
sodium (Pentothal) is then administered in the operating room to induce anes-
thesia. The patient is then given inhaled gas and oxygen to maintain anesthesia.
Sometimes the anesthetic is administered IV. Depending on the nature of the
operation, the patient may also receive a muscle relaxant.
The patient experiences four stages of anesthesia, some of which are not
observable because they occur rapidly. These stages are:
Stage one: analgesia
The patient experiences analgesia (a loss of pain sensation) but remains con-
scious and can carry on a conversation.
Stage two: excitement
The patient may experience delirium or become violent. Blood pressure rises and
becomes irregular, and breathing rate increases. This stage is typically bypassed
by administering a barbiturate such as sodium pentothal before the anesthesia.
Stage three: surgical anesthesia
Skeletal muscles relax. Breathing becomes regular. Eye movement slows then
stops. It is at this point when surgery begins.
Stage four: medullary paralysis
Breathing and other vital functions cease to function because the respiratory cen-
ter (medulla oblongata) is paralyzed. Death results if the patient is not revived
quickly. Careful administration of the anesthesia prevents reaching this stage.
A list of Anesthetic Drugs is provided in the Appendix. Detailed tables show
doses, recommendations, expectations, side effects, contraindications, and more;
available on the book’s Web site (see URL in Appendix).