Paravertebral Block
Clinical Applications
This block can be added to multiple intercostal or bilateral celiac
plexus blocks to provide anesthesia for thoracic, abdominal, pelvic, and upper leg
surgery. Bilateral and continuous applications have also been described. Paravertebral
block may be useful in the diagnosis and treatment of certain chronic pain disorders,
including postthoracotomy and postmastectomy pain.
Technique: Thoracic Paravertebral Block
Thoracic paravertebral blockade occurs as the spinal nerves emerge
from the vertebral foramina. This results in somatic and sympathetic block of multiple
contiguous thoracic dermatomes above and below the injection site.
Thoracic paravertebral block can be performed with the patient
in the sitting, lateral, or prone position; the sitting position allows easy identification
of landmarks. The thoracic spinous processes are identified, and the needle is inserted
2.5 to 3 cm lateral to the most cephalad aspect of the spinous process and advanced
perpendicular to the skin in all planes to contact the transverse process of the
vertebra below, typically at a depth of 2 to 4 cm. After the transverse process
has been identified, the needle is redicted cephalad and gradually advanced until
a loss of resistance is felt 1 to 1.5 cm past the superior edge. Although spread
of local anesthetic is variable, a single injection of 15 mL produces unilateral
somatic blockade over four or five dermatomes; there is a tendency for caudal (compared
with cephalad) spread.[71]
Alternatively, 3 to
4 mL of local anesthetic may be injected at each segment.
Technique: Lumbar Paravertebral Block
Lumbar nerves exit the vertebral foramina inferior to the caudad
edge of the transverse process. Each nerve divides into anterior and posterior branches;
the anterior branches of L1 through L4 (with a contribution from T12) form the lumbar
plexus.
The patient is placed in the prone position as described for intercostal
blockade. Lines are drawn across the cephalad edges of the lumbar vertebral spinous
processes. These lines lie opposite the caudad edges of the homologous transverse
processes ( Fig. 44-29A
;
see Plate 10A
in the color
atlas of this volume). A skin wheal is raised 3 cm lateral to the midline, and a
20-gauge, 8-cm needle is advanced perpendicularly until it contacts the transverse
process at a depth of 3 to 5 cm. The needle is then redirected to walk off the caudad
edge of the transverse process. At 1 to 2 cm (the thickness of the transverse process)
beyond this point, 6 to 10 mL of local anesthetic is injected (see Fig.
44-29B
; see Plate 10B
in the color atlas of this volume). Elicitation of a paresthesia or use of a nerve
stimulator is helpful in confirming correct needle placement.
Side Effects and Complications
Because of the proximity of the neuraxis, epidural or subarachnoid
injection of local anesthetic is a risk. Intravascular injection through the lumbar
vessels, vena cava, or aorta is possible. Pleural puncture and pneumothorax have
occurred with frequencies of 1.1% and 0.5%, respectively.
Figure 44-29
A, Patient positioning
and surface landmarks for a lumbar paravertebral nerve block (see Plate
10A
in the color atlas of this volume). B,
For a paravertebral nerve block, the needle is advanced perpendicularly until it
contacts the transverse process. It is redirected to walk off the caudad edge of
the transverse process and advanced 1 to 2 cm (see Plate
10B
in the color atlas of this volume).
