Neuraxial Blocks Flashcards
Superior articular process
The vertebral column is formed by ____ vertebrae?
33
Cervical = 7
Thoracic = 12
Lumbar = 5
Sacral = 5-fused
Coccygeal = 4-fused
What does letter D represent?
Spinous process
What does A represent?
Transverse process
What does C represent?
Lamina
Cervical and thoracic spinous processes angle in a ____ direction. This requires a more ____ approach with the needle.
Caudal; cephalad
Vertebra prominent C7
Spine of scapula T3
Inferior angle of scapula T7
Rib margin 10cm from midline L1
Superior aspect of iliac crest L4
Posterior superior iliac spine S2
The intercristal line (aka ________) is a horizontal line drawn across the superior aspects of the iliac crests that correlates with the ____ vertebra.
Tuffier’s line; L4
In infants up to 1 year, the intercristal line (Tuffier’s line) correlates with the ____ interspace.
L5-S1
Pedicle
What does A represent?
Superior articular process
What does B represent?
Transverse process
What does C represent?
Lamina
What does D represent?
Inferior articular process
What does E represent?
Spinous process
In the adult, which anatomic structure correlates with the termination of the dural sac?
Superior iliac spines (S2)
Conus medullaris is at which vertebral level?
L1
The sacral hiatus and sacrococcygeal ligament is at which level?
S5
Cauda equina is comprised of nerves and nerve roots from the ____ nerve pairs and the ____ nerve.
L2-S5;
Coccygeal
The subarachnoid space terminates at the ______ in an adult _____ & infant ____
Dural sac
S2
S3
Anchors the spinal cord to the coccyx
Filum terminale
The filum terminale is fixated at which two points?
- Conus medullaris
- Coccyx
Order the spinal ligaments from superficial to deep
1.Supraspinous ligament
2. Interspinous ligament
3. Ligamentum flavum
4. Posterior longitudinal ligament
5. Anterior longitudinal ligament
What does A represent?
Supraspinatus ligament
What does B represent?
Interspinous ligament
What does C represent?
Ligamentum flavum
What does D represent?
Posterior longitudinal ligament
What does E represent?
Anterior longitudinal ligament
What does A represent?
Supraspinous ligament
What does B represent?
Interspinous ligament
What does C represent?
Ligamentum flavum
What does D represent?
Posterior longitudinal ligament
What does E represent?
Anterior longitudinal ligament
Piercing the ______ contributes to the loss of resistance when the needle enters the epidural space.
Ligamentum flavum
The needle passes through what 3 ligaments during the midline approach?
- Supraspinous ligament
- Interspinous ligament
- Ligamentum flavum
What ligament does the needle pass through during the paramedian or Taylor approach?
Ligamentum flavum
The paramedian approach involves inserting the needle ____ degrees off the midline or _________ to the interspace
15 degrees;
1cm lateral and 1cm inferior
Which statements about the epidural space are true?
A. Batson’s plexus passes through the lateral region.
B. Its volume is increased during the third stage of pregnancy
C. It neighbors the pia mater
D. It ends at the sacrococcygeal ligament
A & D
_______ is the network of epidural veins that drain the spinal cord and the meninges. It typically passes through the lateral and anterior regions of the epidural space
Batson’s plexus
Transection of the C6 posterior nerve root will cause?
Sensory block of the thumb
The ____ roots are sensory, and the _____ roots are motor and autonomic.
Posterior (dorsal); anterior (ventral)
Diaphragmatic paralysis occurs with injury to ______
C3-5
What dermatome block height level is required for upper abdominal surgery, cesarean section, & cystectomy?
T4 nipple line
What dermatome block height level is required for lower abdominal surgery and appendectomy?
T6-T7 (xiphoid process)
What dermatome block height level is required for total hip arthroplasty, vaginal delivery, & TURP?
T10 (umbilicus)
What dermatome block height level is required for lower extremity surgery?
L1-L3 (inguinal ligament)
What dermatome block height level is required for foot surgery?
L2-L3
What dermatome block level is required for Hemorrhoidectomy?
S2-S5
Blockade of cardio accelerator nerves occurs at which levels?
T1-T4
In the ______ space, the primary site of local anesthetic action is not eh myelinated preganglionic fibers of the spinal nerve roots
Subarachnoid
What is the most reliable determinant of intrathecal spread when using hypo- or isotonic solution?
Dose
What is the most reliable determinant of intrathecal spread when using a hyperbaric solution?
Baricity
Sensory blockade is ___ dermatomes above the motor block. (Spinal)
2
Autonomic blockage is ___ dermatomes above the sensory block. (Spinal)
2-6
What are the primary determinants of spread in epidural anesthesia?
Volume and level of injection
What structure must be traversed by epidural LAs and what is their primary target?
LA in the epidural space must first diffuse through the dural cuff before they can anesthetize the nerve roots
What type of fiber is blocked first after a spinal anesthetic?
Type B- preganglionic ANS fibers
Skeletal muscle- motor
Proprioception
A alpha
Touch
Pressure
A beta
Skeletal muscle- tone
A Gamma
Fast pain
Temperature
Touch
A delta
Preganglionic ANS fibers
B
Postganglionic ANS fibers
C (sympathetic)
Slow pain
Temperature
Touch
C (dorsal root)
_____ is the determinant of epidural block height
Volume
____ is the primary determinant of epidural block density
Concentration
What are the 3 most important factors that determine local anesthetic spread in the subarachnoid space?
Baricity, patient position, & LA dose
In the supine position:
The greatest points of lordosis are ___ & ___
The greatest points of kyphosis are ___ & ___
C5 & L3;
T5-T7 & S2
In the supine position, how will a hypobaric solution spread in the intrathecal space?
It will concentrate in the lower lumbar region
After administering a hyperbaric solution, the block is not as high as expected. What can you do?
If the block hasn’t set, you can place the pt in the trendelenburg position
Define baricity
The ratio is the density of local anesthetic solution to the density of CSF
The gut receives parasympathetic innervation from ____ and sympathetic innervation from ____
Vagus nerve (CN 10);
Sympathetic chain (T5-L2)
What reflex contributes to asystole that occurs with spinal anesthesia?
Bezold-Jarisch reflex. The heart slows to allow it adequate time to fill
What is the most likely cause of apnea due to spinal anesthesia?
Brainstem hypoperfusion
Neuraxial opioids inhibit afferent pain transmission in the ______ (lamina _ of the dorsal horn)
Substantia gelatinosa; 2
List 3 valvular lesions that are generally regarded as contraindications for neuraxial anesthesia
AS, MS, hypertrophic cardiomyopathy
For a T10 sensory caudal block, how much LA should be administered?
1ml/kg
What are absolute C/I to caudal anesthesia?
Spina bifida
Meningomyelocele
Meningitis
What are the relative C/I to caudal anesthesia?
Pilonidal cyst
Abnormal superficial landmarks
Hydrocephalus
Intracranial tumor
Progressive degenerative neuropathy
What ligament is punctured when performing a caudal block?
Sacrococcygeal ligament
To remove an epidural catheter, hold lovenox for ___ and restart in ____
12 hrs; 4 hrs
Surgical decompression of epidural hematoma within ___ offers the best chance of recovery
8 hours
A patient presents with lower extremity weakness, numbness, low back pain, and bowel and bladder dysfunction after neuraxial anesthesia. What is the most likely cause?
Epidural hematoma
How long must clopidogrel be discontinued before doing a neuraxial block?
7 days
How long must Enoxaparin be discontinued before performing a neuraxial block
Prophylactic dosing = 12 hrs
Therapeutic dosing = 24 hrs
What are the most common side effects of an epidural blood patch?
Backache & radicular pain
Transient neurological symptoms respond to what?
NSAIDs, opioids, trigger point injection
______ is the most common cause of TNS
Lidocaine
What medication can be given to prevent the Bezold-Jarisch reflex during spinal anesthesia?
Ondansetron (5-HT3 receptor antagonists)
What factors increase risk of cauda equina syndrome? Why?
5% lidocaine & microcatheters.
Microcatheters focus LA on a small area of the cord, exposing this region to a high concentration of LA
Neurotoxicity is the result of exposure to high concentrations of LA leading to?
Cauda equina syndrome
Bowel and bladder dysfunction, sensory deficits, weakness, & paralysis are symptoms of what?
Cauda equina syndrome
Patient positioning, stretching of the sciatic nerve, myofascial strain, and muscle spasm can lead to what?
Transient neurologic symptoms
What factors increase the risk of TNS?
Lidocaine, lithotomy position, ambulatory surgery, & knee arthroscopy
Sever back & butt pain that radiates to both legs. Usually within 6 - 36 hrs of neuraxial anesthesia and persists for 1 - 7 days
TNS (transient neurologic symptoms)
What is the BEST course of action when an epidural catheter breaks during its removal?
Leave it inside the patient
How does neuronal anesthesia cause hypotension?
The primary mechanism is anesthetic blockade of the preganglionic B fibers in the sympathetic chain (sympathectomy)