LA - Neuraxial/Subarachnoid Flashcards
Total number of vertebrae
33
Types of vertebrae
- Cervical (7)
- Thoracic (12)
- Lumbar (5)
- Sacral (5)
- Coccygeal (4)
How many pairs of spinal roots are there?
31
Spinal portions - convex anteriorly
Cervical + Lumbar
Spinal portions - convex posteriorly
Thoracic + Sacral
Spinal cord ends at
Adults - L1
Infants - L3
Conus medullaris
where SC terminates
Horses tail
cauda equina
-lumbar + sacral roots from L2-coccygeal region
end of epidural space
sacral hiatus
-5th sacral vertebra not fused dorsally
How to identify sacral hiatus?
Sacral cornu - 2 bony prominences on both sides of hiatus
All vertebrae except 1 have____
Which vertebrae does not have the above?
- anterior body
- 2 pedicles that project posteriorly
- 2 lamina that connect pedicles
- C1
Where is the spinal cord located?
spinal canal
what forms the spinal canal?
2 lamina that connect pedicles
Where is the supraspinous Ligament thickest and broadest?
Upper Lumbar region
What is after the Ligamentum flavum?
Epidural Space
What is the epidural space bound to posteriorly?
Ligamentum Flavum
Where is a spinal placed?
Subarachnoid
Where is CSF located?
Subarachnoid space
Where does SC end in adult?
L1
Arachnoid/subarachnoid space ends at
S2
Spinal nerves - how many pairs?
31
Where do spinal nerves exit the spine?
- C1-C7 exit above respective vertebra
- C8 exits below C7 vertebra
- All other spinal nerves (T1 and below) exit below respective vertebra
How many cervical spinal nerves are there?
8 pairs
despite only 7 cervical vertebra
Cervical spinal nerves exit
- C1-C7 nerves exit above body of corresponding vertebrae
- C8 nerve exits below C7 body
Blood supply to spinal cord is supplied via
1 anterior spinal artery
2 (paired) posterior artires
The anterior spinal artery supplies
anterior 2/3 of cord
The posterior spinal arteries supply
posterior 1/3 of cord
Additional blood supply to spinal cord is supplied via
radicular arteries
Biggest radicular artery
Artery of Adamkiewicz
arteria radicularis magna
Artery of Adamkiewicz
(arteria radicularis magna) supplies which portion of spinal cord?
anterior lower 2/3
injury or hypoperfusion of Artery of Adamkiewicz
(arteria radicularis magna) can result in
anterior spinal artery syndrome
principle site of action for neuraxial anesthesia
nerve root
During a spinal, where does sensory/autonomic blockade occur?
- Sympathetic fibers more easily blocked so segmental blockade occurs
- sympathectomy is 2 vertebral spaces above point where sensory blockade occurred
Diaphragm is innervated by which nerve?
C3, 4, 5 (phrenic nerve exits)
“keep the diaphragm alive”
Cardiac accelerator fibers are innervated by which nerve?
T1-T4
CVS side effects during spinal
- decreased BP (T5-L1) - peripheral pooling
2. decreased HR (T1-T4: cardioaccelerator fibers) - inhibits compensatory vasoconstriction above blockade
Tx: hypotension d/t spinal
- Fluids (peripheral pooling)
2. Phenylephrine (sympathectomy)
1st sign of hypotension
N/V
Neuroendocrine effects of neuraxial block
Blunts stress response (attenuates surgical stimulation)
-evidenced by cortisol levels
Spinal Blockade: Location of Sympathetic, motor, sensory
Motor block: T-8
Sensory: T-6
Sympathetic: T-4
Epidural Blockade: Location of Sympathetic, motor, sensory
Sympathetic/Sensory = same level
Motor block: T-10
Sensory + Sympathetic: T-6
Biggest hematologic risk of neuraxial anesthesia
epidural hematoma
Contraindications to neuraxial anesthesia
CHIN Coagulopathy Hypotension Infxn/Increased ICP No
Coagulopathic - contraindications
INR < 1.5
Platelets 50-100
Which anticoagulants should be held prior to neuraxial?
Heparin IV
Warfarin
Plavix
Eliquis
Which anticoagulants do not need to be held prior to neuraxial?
ASA, NSAIDs, Heparin SubQ
Heparin IV - how does this effect neuraxial?
hold 4-6h prior to insertion of catheter
Resume 1h after removal
Warfarin - how does this effect neuraxial?
INR < 1.5 prior to placement of catheter
Plavix - how does this effect neuraxial?
Clopidogrel
Hold 7d prior
Eliquis - how does this effect neuraxial?
Apixiban
Hold 26-30h prior
Resume 4-6h after
*monitor Anti-Factor Xa
What should be available prior to starting neuraxial?
Airway management
Resuscitation: IV, IVF, ACLS Rx, pressors
Hyperbaric LA
- depends on
- drug moves
Higher specific gravity (denser) than CSF
Drug moves caudad (to “down” side)
How to make LA hyperbaric
+ glucose/dextrose (8.25% dextrose)
Hypobaric LA
- depends on
- drug moves
Lower specific gravity than CSF (lighter)
Drug moves cephalad (“up” side)
How to make LA hypobaric
Add sterile H2O
Which baricity is preferred?
More common: hyperbaric
CSF specific gravity
1.003-1.008
Isobaric
same specific gravity as CSF
-stays where you inject
Pt laying down, hyperbaric neuraxial injected, where will LA go?
Cephalad because pt laying down, going “down” is actually towards head
Pt with broken hip - which hip is placed onto operating table?
broken hip down onto OR table
How to block unilaterally
Operative side down + hyperbaric LA
Midline approach for SA block passes thru
Skin SubQ Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space ** Dura Mater Arachnoid mater Subarachnoid Space**
Paramedium Approach
*miss supra/interspinous ligaments Skin SubQ Ligamentum flavum Epidural space ** Dura Mater Arachnoid mater Subarachnoid Space**
L4 anatomical landmark
iliac crest
1st resistance felt in paramedian approach
Ligamentum Flavum
PDPH is related to
larger needles
-also cutting needles, more common w/ epidural
