Nerve blocks consist of injecting the agent
into the region of a nerve trunk or other
large nerve branches. This form of
anesthesia blocks all impulses to and from
the injected nerves.
Spinal anesthesia consists of injecting the
agent into the subarachnoid space of the
spinal canal between the third and fourth
lumbar space or between the fifth lumbar
and first sacral space of the spinal column.
This form of anesthesia blocks all impulses
to and from the entire area below the point
of insertion, provided the patients posi-
tion is not changed following injection of
the agent. If the patients position is
changed, for example, from dorsal recum-
bent to Trendelenburgs, the anesthetic
agent will move up the spinal column and
the level of the anesthesia will also move
up. Because of this, care must be exercised
in positioning the patients head and chest
above the level of insertion to prevent
paralysis (by anesthesia) of the respiratory
muscles. In general, spinal anesthesia is
considered the safest for most routine ma-
Epidural blocks consist of injecting the
agent into the epidural space of the spinal
canal at any level of the spinal column. The
area of anesthesia obtained is similar to
that of the subarachnoid spinal method.
The epidural method is frequently used
when continuous anesthesia is desired for
a prolonged period. In these cases, a cathe-
ter is inserted into the epidural space
through a spinal needle. The needle is
removed, but the catheter is left in place.
This provides for continuous access to the
Saddle blocks consist of injecting the agent
into the dural sac at the third and fourth
lumbar space. This form of anesthesia
blocks all impulses to and from the
perineal area of the body.
Caudal blocks consist of injecting the
agent into the sacral canal. With this
method, anesthesia is obtained from the
umbilicus to the toes.
GENERAL ANESTHESIA. General anes-
thetics cause total loss of sensation and complete
loss of consciousness in the patient. They are ad-
ministered by inhalation of certain gases or
vaporized liquids, intravenous infusion, or rec-
The induction of inhalation
anesthesia is divided into four stages. These stages
and the bodys main physiological reaction in each
phase are explained below and depicted in figure
Stage 1 is called the stage of analgesia or
induction. During this period, the patient
experiences dizziness, a sense of unreality,
and a lessening sensitivity to touch and
pain. At this stage, the patients sense of
hearing is increased and responses to noises
are intensified (fig. 5-3).
Stage 2 is the stage of excitement. During
this period, there is a variety of reactions
involving muscular activity and delirium.
At this stage, the vital signs show evidence
of physiological stimulation. It is impor-
tant to remember that during this stage the
patient may respond violently to very lit-
tle stimulation (fig. 5-3).
Stage 3 is called the surgical or operative
stage. There are four planes to this stage.
Figure 5-3.Stages of anesthesia.