Neuraxial Principles Flashcards
ASRA
normal PT (prothrombin time)
What pathway does it measure?
12-14 seconds
* extrinsic pathway
ASRA
Normal International normalized ratio (INR)
What pathway does it measure?
0.8-0.11
- extrinsic pathway
ASRA
Normal Activated Partial Thromboplastin Time (aPTT)
What pathway does it measure?
25-32 seconds
- extrinsic pathway
ASRA
Normal Bleeding Time
what is it related to?
3-7 minutes
- r/t platelet aggregation/activation/adhesion
ASRA
Normal Platelet Levels
150,000 - 300,000 mm3
Intrinsic Pathway Factors
“if you can’t buy the intrinsic pathway for $12, you can buy it for $11.98
- XII, XI, IX, VIII
Extrinsic Pathway Factors
“For 37 cents, you can purchase the extrinsic pathway”
- III, VII
Final Common Pathway Factors
“The final common pathway can be purchased at the five (V) and dime (X) for 1 (I) or 2 (II) dollars on the 13th (XIII) of the month”
- V, X, I, II, XIII
Spine Landmarks
C7
Vertebra Prominens
Spine Landmarks
T3
Root of Spine of Scapula
Spine Landmarks
T7
Inferior Angle of Scapula
- good place to do a thoracic epidural
Spine Landmarks
What is the rib margin from midline @ L1?
10cm
Spine Landmark
L4
Superior Aspect of Iliac Crest
- important for central neuraxial
Spine Landmark
S2
Posterior Superior Iliac Spine
Spine Landmarks
What is the Intercristal line (Tuffier’s Line)?
- A horizontal line that runs across the top edges of the hip bones (iliac crests)
- matches the L4 vertebra
- helps identify spaces b/w vertebra for inserting spinal anesthesia needles
Spine Landmarks
What does the space above Tuffier’s Line align with?
L3-L4 vertebrae
Spine Landmarks
What does the space below Tuffier’s line align with?
L4-L5
Where does the spinal cord end?
- Adults - L1
- Peds - L3
Spine Landmarks
What area does the intercristal line correspond to in infants up to 1 yr old?
L5-S1 intervertebral space
Spine Landmarks
What are the landmarks for caudal anesthesia?
Sacral Cornu
- LA goes in the sacral hiatus that is covered by the sacrococcygeal ligament
Where does the spinal cord start & end?
Starts - Medulla Oblongota (rostral region)
Ends - Conus Medullaris (L1)
*b/w L1-L2 in adults
Where does the cauda equina extend from?
conus medullaris — dural sac
* nerve roots from L2-S5 vertebrae & coccygeal nerve
Where does the dural sac end?
S2 in adults, S3 in infants
Where does the filum terminale extend from?
What is its purpose?
- extends from conus medullaris to coccyx (continuation of pia mater)
- function is to anchor spinal cord to coccyx
Internal Filum Terminale Location
Extends from conus medullaris to dural sac (L1-S2)
External Filum Terminale Location
Extends from dural sac into the sacrum (S2-S5)
What signal does the anterior spinal cord take care of?
Motor
What signal does the posterior spinal cord take care of?
Sensory (S after M - so sensory in the back)
- PS - i love neuraxials
Is the afferent nerve sensory or motor?
sensory - toward the brain (ascending limb)
Is efferent sensory or motor?
motor - away from the brain (descending)
Order of Meningeal layers from outer to inner
- Dura Mater: outermost
- Arachnoid Mater: middle layer
- Pia Mater: innermost (covers the spinal cord)
Where is the epidural space located? What does it contain?
- located outside the dura mater (before the dura)
- contains fat and small epidural veins
Where is the subdural space located?
- potential space b/w dura mater & arachnoid mater
Where is the subarachnoid space located? What does it contain?
- b/w the arachnoid mater and pia mater
- contains CSF - cushions/protects the cord
What is the cranial border of the epidural space?
Foramen Magnum
What is the caudal border of the epidural space?
Sacrococcygeal ligament (S5 - coccyx)
What is the anterior border of the epidural space?
posterior longitudinal ligament
What are the lateral borders of the epidural space?
vertebral pedicles
What are the posterior borders of the epidural space?
ligamentum flavum & vertebral lamina
What are the contents of the epidural space?
- nerves, fatty tissue, lymphatics, blood vessels
What is Batson’s Plexus?
- plexus formed by valveless epidural veins that drain blood from the cord and its linings