spinal anaesthesia

1. ZIKRULLAH

2. INTRODUCTION
 The bony vertebral column
provides
 Structural support
 Protection of the spinal cord and
nerves
 Provides Mobility

3. The Vertebral Column
33 vertebrae
7 Cervical
12 Thoracic
5 Lumbar
5 Sacral (fused)
4 Coccygeal
(usually)

4. Cervical Vertebrae (C1 – C 7)
 First cervical vertebrae(C1 ) = Atlas(BODY
ABSENT)
 The 1st cervical vertebrae has unique
articulations that allow it to articulate to the base
of the skull and the 2nd cervical vertebrae.
 Second cervical vertebrae (C2 ) = Axis
 Vertebrae C3 - C6 are similar
 Transverse foramina in each cervical vertebra
 C7 has the vertebra prominens

6. Thoracic Vertebrae (T1 - T12)
 T1 – T12
 Larger than cervical vertebrae
 Large Spinous Processes
 Articulations for ribs are present

7. Lumbar Vertebrae (L1 - L5)
 L1-L5
 Massive block-like body
 Long hatchet shaped
spinous process
 bulkiest

8. Sacrum (5 fused)
Coccyx (3-5 fused)
 Sacral vertebrae are fused into one bone. In most
individuals the lamina portion of S4 and S5 do not
fuse. This allows for the formation of the sacral
hiatus. This ‘anatomical fact’ becomes important
for the administration of caudal anesthesia.

10.  Each vertebra consists of a pedicle, transverse process,
superior and inferior articular processes, and a spinous
process.
 Each vertebra is connected to the next by intervertebral
discs.
 There are 2 superior and inferior articular processes
(synovial joints) on each vertebra that allows for articulation.
 Pedicles contain a notch superiorly and inferiorly to allow
the spinal nerve root to exit the vertebral column.

11. Superior Articular Process
Spinous
Process
Inferior Articular Process

12. Spinous
Process
Lamina
Transvers
e Process
Vertebral
Body
Spinal
Canal

13. Intervertebral
ForaminaSpinal Nerve
Root
s
The intervertebral discs
make up one fourth of the
spinal column's length.
There are no discs
between the Atlas (C1),
Axis (C2), and Coccyx.
Discs are not vascular and
therefore depend on the
end plates for diffusion of
needed nutrients.
Each pair of spinal
nerves passes through
a pair of intervertebral
foramina located
between two
successive vertebrae
Intervertebral Disc

14. Posterior Boundary:
Spinous Process and
Laminae
Anterior
Boundary:
Vertebral Body
Lateral
Boundary:
Transvers
e process,
pedicle

15. Angle of Transverse Process
and Size of Interlaminar
Spaces

16. Thoracic
Vertebrae
Lumbar
Vertebrae
Angle of transverse
process will affect how
the needle is orientated
for epidural anesthesia
or analgesia.
With flexion the spinous
process in the lumbar
region is almost
horizontal. In the
thoracic region the
spinous process is
angled in a slight caudal
angle.

17.  Interlaminar spaces
are larger in the
lower lumbar region.
 If an anesthesia
provider finds it
challenging at one
level , moving down
one level may
provide a larger
space.
L 2
L 5

18. Ventral
side:
Anterior and
posterior
longitudinal
ligaments
Dorsal side:
Important
since these
are the
structures
our needle
will pass
through!

19. Dorsal ligaments transversed
during neuraxial blockade.
With experience the
anesthesia provider will be
able to identify anatomical
structures by “feel”.

20.  It is posterior to the epidural space
 Extends from the foramen magnum to the
sacral hiatus
 It is not one continuous ligament but
composed of right and left ligamenta flava
which meet in the middle

21.  May or may not be fused in the middle
 Varies in respect to thickness, distance to
dura, skin to surface distance, and varies
with the area of the vertebral canal

22. Site Skin to
ligament (cm)
Thickness
(mm)
Cervical - 1.5 -3.0
Thoracic - 3.0 – 5.0
Lumbar 3.0 – 8.0 5.0 – 6.0
Caudal variable 2.0 – 6.0

23.  Lamina and spinous processes
 Interspinous ligament
 Supraspinous ligament which extends
from the occipital protuberance to the
coccyx and functions to join the
vertebral spines together

25.  Extends from foramen
magnum to second
lumbar vertebra
 Segmented
◦ Cervical
◦ Thoracic
◦ Lumbar
◦ Sacral
 Gives rise to 31 pairs of
spinal nerves
 Not uniform in diameter
throughout length

26.  There are 31 segments in the spinal
cord:
◦ 8 cervical (C1 - C8)
◦ 12 Thoracic (T1 - T12)
◦ 5 Lumbar (L1 - L5)
◦ 5 Sacral (S1 - S5)
◦ 1 Coccygeal

27.  The spinal cord is located within the vertebral
column

28.  Each cord segment
has a corresponding
vertebra of the same
name (e.g., C3).
 Spinal nerves
enter/exit
underneath their
corresponding
vertebral segment.

29.  The spinal cord is with
two enlargements-
cervical and lumbar
 The cervical
enlargement supplies
nerves to the pectoral
girdle and upper limbs
 The lumbar
enlargement supplies
nerves to the pelvis and
lower limbs.
Cervical
enlargement
C5 - T1
Lumbar enlargeme
L2 - S3

30. In adults usually ends at
L1.
Infants L3
There are anatomical
deformity
For most adults it is
generally safe to place a
spinal needle below L2
unless there is a known
anatomic variation.
Be careful where you place your needle!

31.  Anterior and posterior nerve roots join each other
and exit intervertebral foramina forming spinal
nerves from C1-S5.
 At the Cervical level-nerve root arises above the
foramina resulting in 8 cervical spinal nerves but
only 7 cervical vertebrae.
 At the Thoracic level- exit below the foramina.
 At the Lumbar level- form cauda equina and course
down the spinal canal. Dural sheath covers the
nerve roots for a small distance after they exit.

32.  Vary in size and structure from patient to patient
 Dorsal (posterior) roots are responsible for somatic
and visceral sensation.
 Anterior (ventral) roots are responsible for motor
and autonomic outflow.
 Dorsal roots (sensory), though larger, are blocked
easier due to a large surface area being exposed to
local anesthetic solution

33. Dorsal root
Ventral
root
Spinal
nerve

34. Anterior Spinal Artery Posterior Spinal Artery
 A single anterior spinal
artery.
 Formed by the vertebral
artery at the base of the
skull.
 It supplies 2/3rds of the
anterior spinal cord.
 Paired posterior arteries
 Formed by posterior
cerebellar arteries and
travel down the dorsal
surface of the spinal cord
just medial to the dorsal
nerve roots.
 They supply 1/3rd of the
posterior cord.
Additional blood flow is received by the anterior and
posterior spinal arteries from the intercostal and lumbar
arteries.

36. Artery of Adamkiewicz
 Radicular artery arising from the aorta.
 It is large and unilateral (found on the left side).
 It supplies the lower anterior 2/3rds of the
spinal cord.
 Injury results in anterior spinal artery syndrome.

38.  Dura Mater
◦ Outer most layer & fibrous
◦ Ends at approx S2, where it
fuses with filum terminale
 Arachnoid
◦ Middle layer & non-vascular
◦ Have principal anatomic
barrier for drugs
 Pia Mater
◦ Inner most layer & vascular
◦ Also give rise to Dentate
ligament
38

40.  An extension of the pia mater to the spinal
cord that attaches to the periosteum of the
coccyx.

42.  Potential space between the ligamentum flavum
and duramater
 Extends from the formen magnum to the sacral
hiatus
 It is segmented and not uniform in distribution
 The epidural space surrounds the dura mater
anteriorly, laterally, and most importantly to us
posteriorly.

43.  Safest point of entry
is midline lumbar
 Spread of epidural
anaesthesia parallels
spinal anaesthesia
 Widest at Level L2
(5-6mm)
 Narrowest at Level
C5 (1-1.5mm)
43

44.  Cranially –foramen magnum
 Caudally –sacrococcygeal ligament covering the
sacral hiatus
 Anterior- posterior longitudinal ligament
 Posterior- ligamentum flavum & lamina
 Lateral- pedicles and intervertebral ligaments

45.  Fat
 Areolar tissue
 Nerves
 Lymphatics
 Blood vessels including the Bateson’s venous plexus
{ valveless veins}

46.  With age, the adipose tissue in the epidural space
decreases as does the intervertebral foramina size.
 A dorsomedian band in the midline of the epidural
space, presence of septa, presence of a midline
epidural fat pad may be associated with unilateral
anaesthesia with epidural block .

48.  Space between the arachnoid mater and piamater
 Contents:
 CSF
 Spinal nerve roots
 Trabecular network
 Blood vessels

49.  It is in direct communication with the Brain Stem via
the foramen magnum.
 Terminate in the conus medullaris at the sacral
hiatus.
 In effect the subarachnoid space extends from the
cerebral ventricles down to S2.

51.  Clear fluid (99% water) that fills the subarachnoid space
 Provides mechanical and immunological protection to
Brain, Spinal cord and Thecal sac
 Total volume in adults is 120-160 ml
 Volume found in the subarachnoid space is 25-35 ml
 Produced at a rate of 600 ml per 24 hour period &
replacing itself 3-4 times(aprox 6hr)

52.  Reabsorbed into the blood stream by arachnoid villi
and granulations
 Specific gravity is between 1.003-1.008 (this will
play a crucial role in the baracity of local
anesthetic that one chooses)

53. Generally are palpable to help identify the midline

54.  In the cervical and lumbar areas the spinous processes
are nearly horizontal so with flexion we would only
need to angle the needle slightly cephalad
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

55.  In the thoracic area the spinous processes are
slanted in a caudal direction and so we need to
angle the needle more cephalad

56.  C2 is the first palpable vertebrae
 C7 is the most prominent cervical vertebrae
 With the patients arms at the side the inferior angle
of the scapula generally corresponds with T7

57.  Knowing these landmarks it is important for the
administration of thoracic epidurals
 It is helpful to counts up and down to help ensure
we are placing the thoracic epidural in the
appropriate area for postoperative analgesia

59.  A line drawn between the highest points of both iliac
crests will yield either the body of L4 or the L4-L5
interspace.

60.  Anatomical variations
 Abnormal conditions (tethered cord)
 Inaccurate vertebral level assessment
 Cephalad angulation of the needle
 Performing a dural puncture at an high vertebral
level

61.  Spinal flexion confers NO protection against
spinal cord damage when performing a spinal
anesthesia (especially at higher levels)
THANK YOU