Neuraxial blocks section 2 Flashcards
Transection of the C6 posterior nerve root will cause:
A. diaphragmatic paralysis
B. impaired sympathetic outflow to the C6 distribution
C. Sensory block of the thumb
D. Motor deficit of the middle finger
C. sensory block of the thumb
Posterior nerve roots are
sensory
Anterior nerve roots are
motor and autonomic
_______ is an area of skin that’s innervated by a dorsal nerve root (sensory) from the spinal cord
A dermatome
Key dermatome: C6
thumb
Key dermatome: C7
2nd and 3rd digits
Key dermatome: C8
4th and 5th digits
Key dermatomes: T4
nipple line
Key dermatomes: T6
Xiphoid process
Key dermatomes: T10
umbilicus
Key dermatomes: L4
anterior knee
The spinal cord has ____ paired spinal nerves
31
A sensory level of T4 is needed for the following surgical procedures:
upper abdominal surgery
C-section
cystectomy
A sensory level of T6-T7 is needed for the following surgical procedures:
lower abdominal surgery
appendectomy
A sensory level of T10 is needed for the following surgical procedures:
Total hip arthroplasty, vaginal delivery, TURP
A sensory level of L1-L3 (inguinal ligament) is needed for the following surgical procedures:
lower extremity surgery
A sensory level of L2-L3 is needed for the following surgical procedures:
foot surgery
A sensory level of S2-S5 is needed for the following surgical procedures:
hemorrhoidectomy
Describe the dosing guidelines for a epidural catheter placed at T2-T6 (upper thoracic).
5-10 mL local anesthetic
Describe the dosing guidelines for an epidural catheter placed at T6-L1 (lower thoracic)
10-20 mL
Describe the dosing guidelines for an epidural catheter placed at L2-L5
20 mL local
Key benefits of a well-executed thoracic epidural technique (compared to a lumbar epidural) include:
superior analgesia
minimizes the surgical stress response
reduces the incidence of postoperative pulmonary complications
can spare the nerves that innervate the legs, which will allow for postoperative ambulation
When a thoracic epidural is combined with GA, cardiopulmonary considerations include a higher risk of:
bradycardia (blockade of cardioaccelerator nerves T1-T4)
Hypotension (decreased cardiac output & vasodilation)
changes in airway resistance (increased vagal influence on airways)
In the subarachnoid space, the primary site of local anesthetic action is on the
myelinated preganglionic fibers of the spinal nerve roots
Describe the order in which fibers are blocked.
Autonomic, then sensory, then motor neurons last
Autonomic blockade is __________ than sensory blockade, and sensory blockade is _______ than motor blockade
2-6 dermatomes higher than sensory and sensory is 2 dermatomes higher than motor blockade
Controllable factors that meaningfully affect spread of local anesthetic include
the dose and baricity of the local anesthetic, site of injection, and patient position
Factors that don’t meaningfully affect the spread include
barbotage, speed of injection, bevel orientation, body habitus, and gender
Local anesthetics in the epidural space must first diffuse through _________ before they can block the nerve roots
dural cuff
The primary determinants of spread for epidural anesthesia are
volume and level of injection
Describe the autonomic, sensory, and motor block with epidural anesthesia
Sensory blockade is 2-4 dermatomes higher than the motor block; there’s no autonomic differential blockade with epidural anesthesia
__________ is the most reliable determinant of intrathecal spread when using a hypo- or isobaric solution
Dose
______ is the most reliable determinant of intrathecal spread when using a hyperbaric solution
Baricity
Describe how the level of injection affects spread in the epidural space of the lumbar region
spread is mostly cephalad
Describe how the level of injection affects spread in the epidural space of the midthoracic region
spread is equally cephalad and caudad
Describe how the level of injection affects spread in the epidural space of the cervical region
spread is mostly caudad
Describe the order in which we can test a differential blockade
first- sense of temperature
second- pain
third- sense of light touch or pressure
The _______ can be used to assess the degree of motor block
Modified Bromage Scale
The Modified Bromage Scale can only evaluate the
lumbosacral nerves (nothing more cephalad)
Describe the degrees (0-3) of the Modified Bromage Scale
0= no motor block
1= patient cannot raise an extended leg but can move the knees and feet
2= patient cannot raise an extended leg or move the knee but can move the feet
3= complete motor block
Describe the block onset for peripheral nerves
B- first
C- second
A gamma & delta- third
A alpha & beta- fourth
What is the MOST appropriate spinal dose of 3% 2-chloroprocaine to achieve for a T10 level?
a. 5 mg
b. 20 mg
c. 30 mg
d. 50 mg
c. 30 mg
the dose range needed to achieve a T10 level is 30-40 mg
When dosing a spinal anesthetic, the most important controllable factors affecting block height include
dose, baricity, and patient postion
When dosing an epidural anesthetic, the primary drug-related determinant of block height is
LA volume
When dosing an epidural anesthetic, the primary procedure-related determinant of block height is
the level of injection
When dosing an epidural anesthetic, the primary determinant of block density is
local anesthetic concentration
Describe the necessary dosing for spinal anesthesia using Bupivacaine 0.5-0.75% for a T10 and T4 level to be achieved
T10: 10-15 mg
T4: 12-20 mg
Describe the onset of action of spinal anesthesia for bupivacaine 0.5-0.75%
4-8 min
Describe the dosing for a T10 & T4 level of levobupivacaine 0.5% for spinal anesthesia
T10- 10-15 mg
T4- 12-20 mg
Describe the onset of action for spinal anesthesia of levobupivacaine 0.5%
4-8 min.
Describe the duration of action of bupivacaine 0.5-0.75%
130-220 min.
Describe the dosing needed to achieve spinal anesthesia of T10 & T4 using ropivacaine 0.5-1%
T10- 12 -18 mg
T4- 18-25 mg
Describe the onset of action of ropivacaine 0.5-1%
3-8 min
Describe the duration of action of 0.5-1% ropivacaine
80-210 min.
Describe the needed dosing for T10 & T4 spinal anesthesia using 2-chloroprocaine 3%
T10- 30-40 mg
T4- 40-60 mg
Describe the onset of action of 2-chloroprocaine 3%.
2-4 min.
Describe the duration of action of 2-chloroprocaine 3%.
40-90 min.
Describe the dosing of 0.5-1% tetracaine for T10 and T4 spinal anesthesia
T10- 6-10 mg
T4- 12- 16 mg
Describe the onset of action for tetracaine 0.5-1%
3-5 minutes
