Encyclopedia of Health and Medicine

anesthesia 261
the site of the operation. Local anesthetic agents
block the ability of neurons (NERVE cells) to send
nerve signals, preventing the perception of pain.
Some local anesthetic agents contain EPINEPHRINE, a
vasoconstrictor that reduces bleeding.
The effect of a local anesthetic may last from 20
minutes to 12 hours or longer, depending on the
agent and the extent of infiltration of the area.
Surgeons sometimes use local anesthetic to infiltrate
the area of an operative site at the end of the
operation to provide extended pain relief. Surgeons
may combine local anesthesia and conscious
sedation to reduce anxiety and improve the person’s
level of comfort during and after the operation.
Some amount of a local anesthetic enters the
BLOOD circulation and can cause sensations such as
lightheadedness or a feeling that the lips are
buzzing.
COMMON LOCAL AND REGIONAL ANESTHETIC AGENTS
benzocaine bupivacaine chloroprocaine
etidocaine lidocain emepivacaine
prilocaine procaine ropivacaine
tetracaine
Regional Anesthesia
Regional anesthesia is an injection that infiltrates
nerves to blocks pain signals from a large area of
the body. An anesthesiologist or anesthetist
administers regional anesthesia. The most common
forms of regional anesthesia include
• regional nerve block, in which the anesthesiologist
or anesthetist administers a single injection
of the anesthetic agent into or around a
major nerve to block sensation from the fingers,
hand, arm, toes, foot, or leg
• caudal, in which the anesthesiologist or anesthetist
administers a single injection of the
anesthetic agent into the caudal canal in the
sacrococcygeal (tailbone) region of the spine to
block sensation in the pelvis and perineum
• epidural, in which the anesthesiologist or anesthetist
places a thin catheter into the space surrounding
the SPINAL CORD and injects the
anesthetic agent, potentially as a steady flow or
repeated times, to block sensation from the
point of injection downward for operations on
the lower abdomen and lower extremities
• spinal, in which the anesthesiologist or anesthetist
administers a single injection of the
anesthetic agent directly into the CEREBROSPINAL
FLUID around the spinal cord to block sensation
from the point of injection downward for operations
on the abdomen and lower extremities
Many of the anesthetic agents are the same for
regional anesthesia as for local anesthesia. As
occurs with local anesthetics, a small amount of
the anesthetic agent enters the blood circulation
and can cause mild effects such as HEADACHE or TIN-
NITUS (ringing in the ears). These effects generally
go away within an hour. Because caudal, epidural,
and spinal anesthesia affect the pelvic region and
the muscles of the BLADDER, the surgeon may
instruct placement of a urinary catheter until the
anesthetic wears off. The surgeon may sometimes
leave the epidural catheter in place for 24 to 48
hours for postoperative administration of light
anesthesia or ANALGESIC MEDICATIONS for pain relief.
Regional nerve blocks, caudal anesthesia, and
epidural anesthesia may take up to 20 minutes to
become effective. Spinal anesthesia takes effect
immediately. Though regional anesthesia blocks
only the sensory nerves, movement of the anesthetized
region is difficult because the lack of sensation
makes the affected body parts feel heavy
and uncontrollable. A person has adequately
recovered from regional anesthesia when he or
she can safely walk or regains preanesthesia sensation
or movement of the affected area.
Complications are rare with regional anesthesia
though may include prolonged labor during CHILD-
BIRTH, irritation or bleeding at the injection site,
drop in BLOOD PRESSURE, and post-anesthesia
headache (with epidural or spinal anesthesia).
Infection and injury to the nerves are possible
though extremely rare. Recovery from regional
anesthesia is generally uneventful and fairly rapid.
Conscious Sedation
Conscious sedation alters a person’s awareness of
pain and activities taking place to and around him
or her. With conscious sedation a person generally
can answer questions, respond to instructions, and
tell the doctor whether he or she is experiencing
pain or discomfort though has little or no memory
of the operation and events surrounding it when