Spinal Anesthesia Flashcards
Cephalad
continuous with brainstem through the foramen magnum
Spinal cord terminates as the
conus medullaris are the level of the lower border of the first lumbar vertebral body
Conus medullaris attached by means of
Filum terminale
Filum terminale surrounded by the nerves of the lower lumbar and sacral roots known as
Cauda Equina
Hyperbaric
Heavier than CSF
Pregnancy
Decrease Dose (Cm is decrease) Specific gravity is lower
3 membranes
Pia mater
Arachnoid
Dura
‘Know diagram
Pia mater
Very vascular and close to SC
Arachnoid mater
Delicate, non vascular , adherent to the third and outermost layer, the dura
Dura Mater
Close to the subarachnoid space
Spinal aka
Subarachonoid Block (SAB)
Subarachnoid space located
between pia mater and arachnoid mater
Components of Subarachnoid
CSF Spinal nerves A trabecular network between 2 membranes Blood vessels that supply SC Later extensions of the pia mater - the dentate ligaments
Inability to drain CSF
Hydrocephalus
Multiple puncture
Post Dural puncture headache
Overproduction of CSF leads to (compensatory mechanism)
vasodilation –> Headaches
Blood patach
Tuohy
sit patient up
Access epidural space
20 cc of blood( obtained from venous) injected to the epidural space until pt feel pressure (forms clot)
Blood supply of SC
One anterior
2 posterior
Sharp needles
Unable to feel layers and structures
Type of needle use is
Pencil point needle (NOT a cutting needle)
is thought to be the widest part of the epidural space, measuring 5 to 6 mm at this level
L2
The spinal cord begins at the______and ends where?
level of the foramen magnum and ends at the conus medullaris
Apply lidocaine
Go all the way in then inject while removing the needle
When you arrive to ligamentum FLAVUM
Lose resistance
When you are in ligmentum Flavum
You are in the epidural SPACE
When you perform an SAB (Sub-Arachnoid Block, or Spinal), at L-3-4, 4-5, or L5/S-1, you are injecting into
the Cauda Equina and not into the actual spinal cord,
so there is no risk of damage to the spinal cord!
CSF total volume between the brain and the spinal cord is about
150ml.
CSF volume itself at any given time.
Between 30-50ml in the spinal cord
The pH of CSF is approximately
7.32
CSF is secreted by the________ of the within the_________ ventricular system at a rate of approximately________
Ependymal cells; Choroid Plexus; 30ml/hr.
Iliac crest
Tuffer’s line
The entire CSF volume in the brain and spinal cord is replace every
3-4 hours.
Primarily pain stimuli
Post central gyrus of the parietal lobe
They are responsible for motor-function and
movement away from the
painful stimulus is the
“Precentral-Gyrus” of the
parietal lobe.
31 pairs of spinal
C8 T12 Lum 5 Sa 5 coccygel 1
Gray
neuronal cells and unmyelinated fibers
The Lateral and Ventral White Matter contains the
Descending Motor Tracts.
Dorsal Root carries afferent (ascending) signals heading into the spinal cord and brain
SENSORY Afferent (ascending) Posterior
Ventral Root carries efferent (descending) signals heading out to the periphery
MOTOR efferent (descending)
White matter contains the various tracts,
both ascending and descending, with the Dorsal White Matter containing the ascending sensory tracts.
0.75% bupivacaine
7.5mg/ml
How much bupivacaine to gie
10-15mg (2cc)
How much bupivacaine to give
10-15mg (2cc)
The Somatic contains
sensory neurons for the control of skin, muscle, and joint movement
Primary neurotransmitters are
Norepinephrine and Dopamine
Systolic 110 preop
25 mg of ephedrine with skin wheal lidocaine
Systolic <110 preop TIPS
25 mg of ephedrine with skin wheal lidocaine
Expect sympathectomy what do you have present
NEO or EPHEDRINE
Parasympathetics The primary neurotransmitter is
acetylcholine
Spinal anesthesia interrupts sensory, motor, and sympathetic nervous system innervation.
As LA is injected, it blocks the
small “c” fibers of the sympathetic
nervous system 1st, and gradually diffuses into the interior of the nerve where the larger fibers are for sensory and then, motor!
SNS blockade exceeds somatic (sensory)
blockade by 2 dermatomes, perhaps more.This explains why hypotension often accompanies even low sensory
blocks
C8 landmark
Fifth digit
T10 landmark
Umbilicus
T7 landmark
Tip of xiphoid/ inferior border of scapula
T12 landmark
Inguinal ligament
S1 landmark
Outer side of foot
Being heavier than CSF, the LA will settle in
the most dependent aspect of the subarachnoid space.
When placed supine, the LA tends to gravitate to the
thoracic kyphosis, the average position being T-6.
If SAB performed in the sitting position, and then patient allowed tonremain sitting, what happens
The LA will settle to the lowest point, providing what is
known as a “saddle block
Scoliosis=alters
the “LOW” point.
Kyphosis/Kyphoscoliosis=alters the
“LOW” point.
Pregnancy=may have decreased SG of CSF allowing for
decreased dosage of LA (r/t changes in pH).
Previous back surgery may alter anatomy so levels may
be different than normal.
Elderly=r/t
lower levels of CSF
