NEURAXIAL BLOKADE
O’Donnell, JM
Buckling
SURFACE ANATOMY AND LANDMARKS
LOCATING PROMINENT CERVICAL AND THORACIC VERTEBRAE
- C2 is the first palpable vertebrae
- C7 is the most prominent cervical vertebrae
- With the patients arms at the side the tip of the scapula generally corresponds with T7
PALPATION OF SPINOUS PROCESS
SPINOUS PROCESSES
- Generally
are palpable to
help identify the midline - If unable to palpate
the spinous process one can
look at the upper crease of the
buttocks and line up the midline as
long as there is no scoliosis or other
deformities of the spine.
WHAT IS TUFFIER’S LINE?
- A line drawn between the highest points of both iliac crests will yield either the body of L4 or the L4-L5 interspace.
ANATOMICAL CONSIDERATIONS OF THE SPINAL CORD AND NEURAXIAL BLOCKADE.
THE SUBARACHNOID SPACE IS A CONTINUOUS SPACE THAT CONTAINS
- CSF
- Spinal cord & nerves
CSF
- Clear fluid that fills the subarachnoid space
- Total volume in adults is ~100-150 ml (2 ml/kg)
- Volume found in the subarachnoid space is ~35-45 ml
- Continually produced at a rate of 450 ml per 24 hour period replacing itself 3-4 times
CSF
- Reabsorbed into the blood stream by arachnoid villi.
- Specific gravity is between 1.003-1.007 (this will play a crucial role in the baracity of local anesthetic that one chooses).
- CSF plays a role in the patient to patient variability in relation to block height and sensory/motor regression (80% of the patient to patient variability).
MEMBRANES THAT SURROUND THE SPINAL CORD
- Pia mater
- highly vascular
- covers the spinal cord and brain, attaches to the periosteum of the coccyx (filum terminalis)
- Arachnoid mater
- non-vascular
- attached to the dura mater
- Principal barrier to the migration of medications in and out of the CSF.
- Dura mater (“to toughen”)
- extends from the cranial dura mater, extends from the foramen magnum to S2.