Neuraxial Flashcards
Vertebral column
7 Cervical
12 thoracic
5 lumbar
5 fused sacrum
Anterior - longitudinal ligaments
Posterior - ligamentum flavum
End of spinal cord
Adults - L1
Kid - L2-3
End of dural sac
Adults - S1-2
Kids - S3-4
Blood supply to SC
Anterior spinal artery (2/3 of supply) from vertebral artery
Posterior spinal arteries (1/3 supply) from PICA
Artery of Adamkiewicz
collateral from aorta
~T9-12 –> usually L-sided
Site of action for local/pain control of neuraxial
primarily the nerve roots
Anterior cord block effects?
motor and autonomic
Posterior cord block effects?
somatic and visceral sensors
Somatic blockade
interrupts afferent transmission
- sympathetic = 2 segments cephalad higher than sensory
- Sensory = 2 segments more cephalad than motor blockade
CV effects of autonomic blockade
drop in venous return and BP - proportional to dermatomal level and sympathectomy
*both arterial and venous relaxation
Bezold-Jarisch Reflex
drop in venous return –> less filling of heart –> less cardiac stretch –> increased parasympathetic tone –> bradycardia
Pulmonary effects of blockade
C3-5 = phrenic (diaphragm) not really touched
- can get some accessory and intercostal muscle weakness
GI effects of blockade
vagal tone predominance –> increased peristalsis
What affects spinal anesthetic spread?
- Baricity
- Position
- Dose
- Site of injection
- Height?
Hyperbaric solution
heavy –> steer with gravity
Isobaric solution
equal to CSF –> stays at level of injection
Hypobaric solution
less than CSF –> rises against gravity
Apex of thoracolumbar curve?
T4 –> limits spread of hyperbaric solution in supine position
How does CSF volume affect spread?
Lower CSF volume = more spread
*Pregs, ascites, tumors
Infant spinals
rapid onset, short duration due to more volume per kg and higher CO and vascular pia matter
Epidural space surrounds what of SC?
dura matter posteriorly and nerve roots
Factors affecting level of epidural block?
Mass = volume x [ ]
- volume matters most
opioids augment quality of block
