- Spinal, epidural, and caudal blocks are also
known as neuraxial anesthesia. Each of these blocks can be performed
as a single injection or with a catheter to allow intermittent boluses
or continuous infusions.
- Performing a lumbar (subarachnoid) puncture below
L1 in an adult (L3 in a child) avoids potential needle trauma to
- The principal site of action for neuraxial blockade
is the nerve root.
- Differential blockade typically results in sympathetic
blockade (judged by temperature sensitivity) that may be two segments
higher than the sensory block (pain, light touch), which in turn
is usually two segments higher than the motor blockade.
- Interruption of efferent autonomic transmission at the spinal
nerve roots can produce sympathetic and some parasympathetic blockade.
- Neuraxial blocks typically produce variable decreases
in blood pressure that may be accompanied by a decrease in heart
rate and cardiac contractility.
- Deleterious cardiovascular effects should be
anticipated and steps undertaken to minimize the degree of hypotension.
Volume loading with 10–20 mL/kg of intravenous
fluid for a healthy patient will partially compensate for the venous
- Excessive or symptomatic bradycardia should be
treated with atropine, and hypotension should be treated with vasopressors.
- Major contraindications to neuraxial anesthesia
are patient refusal, bleeding diathesis, severe hypovolemia, elevated
intracranial pressure, infection at the site of injection, and severe
stenotic valvular heart disease or ventricular outflow obstruction.
- For epidural anesthesia, a sudden loss of resistance
is encountered as the needle penetrates the ligamentum flavum and
enters the epidural space. For spinal anesthesia, the needle is
advanced further through the epidural space and penetrates the dura–subarachnoid
membranes as signaled by free flowing cerebrospinal fluid.
- Epidural anesthesia is a neuraxial technique
offering a range of applications wider than the typical all-or-nothing
spinal anesthetic. An epidural block can be performed at the lumbar,
thoracic, or cervical level.
- Epidural techniques are widely used for operative
anesthesia, obstetric analgesia, postoperative pain control, and
chronic pain management.
- Epidural anesthesia is slower in onset (10–20
min) and may not be as dense as spinal anesthesia.
- The quantity (volume and concentration) of local
anesthetic needed for epidural anesthesia is very large compared
with spinal anesthesia. Significant toxicity can occur if this amount
is injected intrathecally or intravascularly. Safeguards against
this include the epidural test dose and incremental dosing.
- Caudal epidural anesthesia is one of the most
commonly used regional techniques in pediatric patients.
Wayne Kleinman is the Director of Obstetric Anesthesia, Encino-Tarzana Regional Medical Center, Los Angeles, California.
Spinal, caudal, and epidural blocks were first used for surgical
procedures at the turn of the twentieth century (see Chapter
1). These central blocks were widely used prior to the 1940s
until increasing reports of permanent neurological injury appeared.
However, a large-scale epidemiological study conducted in the 1950s
indicated that complications were rare when these blocks were performed
skillfully with attention to asepsis and when newer, safer local
anesthetics were used. A resurgence in the use of central blocks
ensued, and today they are once ...