Subarachnoid Block Flashcards
How many pairs of spinal nerves are there and how
are they grouped anatomically?
There are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5
lumbar, 5 sacral, and 1 coccygeal.
Wong, CA. Spinal and Epidural Anesthesia. New York:
McGraw-Hill; 2007: 9.
What is the only absolute contraindications to spinal
anesthesia?
Patient refusal
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 929.
From exterior to interior, name the structures the
spinal needle passes through when performing a
subarachnoid block via the midline approach.
Skin, subcutaneous tissue, supraspinous ligament, interspinous
ligament, ligamentum flavum, dura mater, arachnoid mater, and
subarachnoid space.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 791.
From exterior to interior, what structures will the
needle traverse when performing a subarachnoid
block using a paramedian approach?
Skin, subcutaneous tissue, paraspinous muscle, ligamentum
flavum, dura mater, arachnoid mater, and subarachnoid space.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 792.
Where is cerebrospinal fluid created and absorbed?
CSF is created in the choroid plexus and absorbed in the
arachnoid granulations (remember C for Create and Choroid
and A for Absorb and Arachnoid)
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1081
What are some of the relative contraindications to
spinal anesthetic?
Hypovolemia, sepsis, increased intracranial pressure,
coagulopathy or thrombocytopenia, and infection at the
puncture site. Other major contraindications include:
conditions resulting in left ventricular outflow obstruction such
as aortic stenosis or hypertrophic subaortic stenosis restrict the
ability of the heart to increase cardiac output as compensation
for hypotension due to the sympathectomy induced by neuraxial
anesthesia.
Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC,
Ortega R. Clinical Anesthesia. 7th ed. Philadelphia, PA:
Lippincott Williams and Wilkins; 2013: 929.
What are the major potential complications arising
from a spinal anesthetic?
Neurologic dysfunction, allergic reaction, anterior spinal artery
syndrome, trauma, drug toxicity, infection, hematoma, and total
spinal blockade.
Wong, CA. Spinal and Epidural Anesthesia. New York:
McGraw-Hill; 2007: 166.
How far does the subarachnoid space extend
caudally in adults?
The subarachnoid space extends from the foramen magnum to
S2 in adults.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 943
How far does the subarachnoid space extend
caudally in children?
The subarachnoid space extends from the foramen magnum to
S3 in children.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 943.
How far does the spinal cord extend caudally in
children?
The spinal cord extends to L3 in children.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 943.
How far does the spinal cord extend caudally in
adults?
The spinal cord extends to L2 in adults.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1071.
Where are the most dependent portions of the spinal
column in the supine position?
Normally, in the supine position, the most dependent portion of
the spinal column occurs at T4-T8 with the peak of the
thoracolumbar curvature occurring at T4. This is important in
relation to hyperbaric spinal solutions which will tend to pool in
the T4-T8 curvature but limit their ascent above T4 in the supine
position.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 956-957.
Where are the two enlargements in the spinal cord
and what causes them?
The cervical enlargement occurs at C4-T1 and the lumbar
enlargement which occurs from L2-S3. The cervical
enlargement is due to the nerve roots that produce the brachial
plexus and the lumbar enlargement produces the lumbar plexus.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1072.
What external anatomic landmark can be used to
identify the L4 interspace?
The superior aspect of the iliac crest can be palpated at the
level of the L4 interspace.
Wong, CA. Spinal and Epidural Anesthesia. New York:
McGraw-Hill; 2007: 1.
What spinal landmark corresponds with the level of
the posterior superior iliac spine?
S2
Wong, CA. Spinal and Epidural Anesthesia. New York:
McGraw-Hill; 2007: 1.
What spinal landmark corresponds with the level of
the posterior superior iliac spine?
S2
Wong, CA. Spinal and Epidural Anesthesia. New York:
McGraw-Hill; 2007: 1.
In what positions can a subarachnoid block be
performed?
A subarachnoid block can be performed in the sitting, lateral, or
prone positions.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1079.
For what procedures is the sitting position for
subarachnoid block advantageous?
The sitting position is advantageous for vaginal or urologic
procedures where a ‘saddle’ block is preferable.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1079.
For what procedures would it be advantageous to
perform a subarachnoid block in the prone position?
The prone position is advantageous for rectal procedures
because the patient can be placed into position for the surgery
before the block is performed.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1079.
For what procedures is it advantageous to perform a
subarachnoid block in the lateral position?
The lateral position is advantageous for surgeries where you
would prefer that the drug be concentrated on one side more
than the other, such as hip surgery.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1079.
How should the patient be instructed to change their
posture to make performing a spinal anesthetic
easier?
They should be encouraged to arch their back in the shape of a
C which opens up the intervertebral spaces and makes
insertion of the needle easier.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1079.
Is it appropriate to wipe off excess Betadine with an
alcohol prep prior to inserting the spinal needle for a
subarachnoid block? Why or why not?
No, you should use a dry sterile gauze to wipe away excess
Betadine after prepping the skin. Alcohol neutralizes the iodine
solution and reduces its ability to function as an antiseptic.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1080.
If Betadine is used as the antiseptic to clean the skin
prior to performing a spinal anesthetic, how long
should you wait after applying the Betadine before
beginning the procedure and why?
You should wait at least 1 minute before beginning the spinal so
that the Betadine has ample opportunity to dry. Then, you
should wipe away any remaining liquid Betadine off of the skin.
If Betadine (or any povidone-iodine solution) is introduced into
the subarachnoid space, it can produce a chemical
arachnoiditis.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1080.
You are inserting a spinal needle during a
subarachnoid block and feel a ‘pop’. What might this
indicate and what should you do next?
The ‘pop’ could represent the loss of resistance sensation felt
as the needle penetrates beyond the ligamentum flavum and
through dura and enters the subarachnoid space. You should
withdraw the stylet and see if CSF flow is present.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 791.
During a subarachnoid block, you inserted the
needle, felt a ‘pop’, removed the stylet and see CSF
flow, what is the recommended step to take next?
It is recommended to rotate the needle 360 degrees in 90
degree increments to make sure that flow is constant in all four
quadrants to ensure proper needle placement. Once you have
verified the needle position, you can verify CSF flow by
aspirating with the spinal syringe and begin administering the
medication for the spinal anesthetic.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 791-
792.
How is a paramedian approach to a subarachnoid
block performed?
A skin wheal is raised 1 cm lateral to the superior tip of the
spinous process at the lumbar level you wish to access. The
tissue below the skin wheal is infiltrated with local anesthetic.
The introducer and needle are then inserted at a 10-15 degree
angle toward midline.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 791-
792
When performing spinal anesthesia, two ‘pops’ are
often felt. The first pop encountered is due to the
needle penetrating what structure?
The first ‘pop’ is the needle penetrating the ligamentum flavum
and the second is the needle penetrating the dura mater.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 955.
While inserting the spinal needle during a
subarachnoid block, you feel as if you have struck
bone. What should you do next?
Carefully check to see if the needle is midline. If the needle is
directed away from midline, withdraw it and reposition the
needle. If it appears to be in the midline, then ‘walk’ the needle
caudally until the subarachnoid space is encountered.
Longnecker DE, Newman MF, Brown DL, Zapol WM.
Anesthesiology. 2nd ed. New York: McGraw-Hill; 2012: 791.
What are the most important factors that determine
the spread of local anesthetics within the
cerebrospinal fluid during a subarachnoid block?
The total dose of anesthetic, the site of injection, the baricity of
the local anesthetic, and the position of the patient during and
immediately after injection.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1081.
What two factors determine the duration of action of
a spinal anesthetic?
The anesthetic drug used and the total dose given.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1081.
How does the volume of the local anesthetic injected
affect the duration and spinal level achieved with the
block?
Volumes between the ranges of 1 mL and 14 mL has been
thoroughly tested and has little effect on the duration of action
of the spinal anesthetic or the sensory level achieved.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1082.
How does the volume of the local anesthetic injected
affect the duration and spinal level achieved with the
block?
Volumes between the ranges of 1 mL and 14 mL has been
thoroughly tested and has little effect on the duration of action
of the spinal anesthetic or the sensory level achieved.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1082.
How does the addition of a vasoconstrictor to a local
anesthetic affect the duration of action of a spinal
anesthetic?
The addition of a vasoconstrictor to the local anesthetic used in
a subarachnoid block will prolong the duration of action of the
block.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1081.
What is the normal specific gravity of CSF?
1.004 to 1.009
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1081.
What is the difference between specific gravity and
baricity?
Specific gravity is the comparison between the density of a
solution (such as CSF) when compared to water, which is
assigned a value of 1. A solution that has a higher density than
water has a value higher than 1. A solution with a density lower
than water has a specific gravity less than 1. Baricity is the
relationship of one solution’s density to the density of another
solution. For example if one solution is more dense than
another, it is said to be hyperbaric in relation to that solution. If
the solution in question is less dense to another solution, it is
said to be hypobaric. If the two solutions have the same
density, they are said to be isobaric with respect to one another.
Nagelhout JJ, Plaus KL. Nurse Anesthesia. 5th ed. St. Louis,
MO: Elsevier Saunders Company; 2014: 1081
