NEURAXIAL
ANESTHESIA:
SPINAL
EPIDURAL
CAUDAL
Rebecca Johnson, CA3 November 29, 2012
Outline
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Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
All of the following are true EXCEPT:
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A. The interspinous ligament attaches to the ligamentum flavum.
B. The ligamentum nuchae continues inferiorly as the supraspinous
ligament.
C. The ligamentum flavum is thickest in the midline and elastin is the
primary component.
D. The epidural space terminates cranially at C1.
E. The epidural space is bounded inferiorly by the sacrococcygeal
ligament.
Answer:

D.

Boundaries of Epidural Space:

Posterior:


Anterior:


vertebral pedicles/intervertebral foramina
Inferior:


posterior longitudinal ligament
Lateral:


ligamentum flavum/vertebral laminae
sacrococcygeal ligament covering sacral hiatus
Superior:

foramen magnum
Vertebral Column

7 cervical vertebrae

12 thoracic vertebrae

5 lumbar vertebrae

5 fused sacral vertebrae

Rudimentary coccygeal vertebrae

Paired spinal nerves exit at each level, C1 to S5

At cervical level
 nerves arise above respective vertebrae

Starting at T1
 nerves exit below their vertebrae

As a result…
 8 cervical nerve roots but only 7 cervical
vertebrae
Spinal Canal

Contains:
Spinal cord
 Meninges (3 layers)

Pia Mater
 Arachnoid Mater
 Dura Mater

Fatty tissue
 Venous plexus
 CSF


Subdural space

Poorly demarcated, potential space that exists between the
dura and arachnoid membranes
Anatomic features pertinent to the performance of
neuraxial blockade include all EXCEPT:


A. In adults, the spinal cord ends at L1-L2.
B. The angulation of the spinous process of the thoracic
vertebrae makes a paramedian approach preferable.

C. In adults the dural sac ends at S2.

D. The largest interspace in the vertebral column is L4-L5.

E. Midline insertion of an epidural needle is least likely to
result in unintended meningeal puncture.
Answer

D.
 The
largest interspace is L5-S1.
 The ligamentum flavum is farthest from the
spinal meninges in the midline, measuring 46mm at L2-L3 interspace.
Anatomy

The spinal cord extends from the
foramen magnum to the level of L1 in
adults

In infants, the spinal cord ends at L3
and moves up as they grow older

Lower nerve roots course some
distance before exiting the
intervertebral foramina


Forms the cauda equina

Pushing vs piercing the cord
The dural sac, subarachnoid and
subdural spaces usually extend to S2 in
adults

Often to S3 in children
Blood Supply

Anterior 2/3 of cord

Anterior spinal artery


Posterior 1/3 of cord

Two posterior spinal arteries



vertebral artery
posterior inferior cerebellar arteries
Radicular arteries

intercostal arteries in the thorax

lumbar arteries in the abdomen
The artery of Adamkiewicz

Aorta

Typically unilateral and on the ___ side?

Left

Major blood supply to the anterior, lower 2/3 of the spinal cord

Injury to this artery can result in …?

Anterior spinal artery syndrome
Outline
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Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
Mechanism of Action

Principal site of action - nerve root

Local anesthetic bathes the nerve root in the
subarachnoid space or epidural space

Spinal anesthesia:
 Direct injection of LA into CSF
 Relatively small dose and volume to achieve
dense sensory and motor blockade

Epidural/Caudal anesthesia:
 Same LA concentration is achieved at nerve roots only with much
higher volumes and quantities

Level for epidural anesthesia
 Must be close to the nerve roots that are to be anesthetized
Somatic Blockade


Sensory blockade interrupts both
somatic and visceral painful stimuli
Motor blockade produces skeletal
muscle relaxation


LA effect on nerve fibers varies
according to many factors:

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Provides excellent OR conditions
Size of the nerve fiber
Myelination
Concentration achieved
Duration of contact
Smaller and myelinated fibers are
more easily blocked
Somatic Blockade

Spinal nerve roots contain varying mixtures of these fiber types and
they vary in their sensitivity to the LA blockade

This results in a differential block

Which nerve fibers are blocked by the lowest sensitivity to LA?

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A. pain

B. motor

C. sympathetic

D. touch
Order of sensitivity:

Sympathetic > pain > touch > motor
Somatic Blockade
Sympathetic block is highest,
generally 2 (up to 6) segments
higher than the sensory block
(pain, light touch)
 Which in turn is usually 2-3
segments higher than the
motor blockade
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Autonomic Blockade

Block of efferent autonomic transmission


sympathetic and some parasympathetic blockade
Sympathetic outflow from the spinal cord


Thoracolumbar
Sympathetic preganglionic nerve fibers



Parasympathetic outflow

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
exit the spinal cord with the spinal nerves from T1 to the L2 level and
may course many levels along sympathetic chain before synapsing with a
postganglionic cell in a sympathetic ganglia
Craniosacral
Parasympathetic preganglionic fibers exit the spinal cord with the
cranial and sacral nerves
Neuraxial anesthesia does not block the vagus nerve

decreased sympathetic tone and/or unopposed parasympathetic tone
Outline
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Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
A pt receives a spinal anesthetic with a sensory
level of T5. Which of the following is likely to occur?
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
A. The small bowel will be dilated and relaxed.
B. Glomerular filtration will be decreased by one
third.

C. Tidal volume will be reduced by one third.

D. The cardioaccelerator nerves will be unaffected.

E. Blood pressure will lower predominantly by
decreasing venous return.
Answer


E
Level of sympathetic block can be 2-6 levels
higher than sensory block.
Cardiovascular Manifestations
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Variable decreases in blood pressure



+/- decrease in heart rate and cardiac contractility
Generally proportional to degree of the sympathectomy
Arterial and venous smooth muscle vasomotor tone:


Innervated by sympathetic fibers from T5 to L1
Blocking these nerves causes:

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vasodilation of the venous capacitance vessels
pooling of blood
decreased venous return to the heart
Arterial vasodilation may also decrease SVR

May be minimized by compensatory vasoconstriction above the
level of the block
Cardiovascular Manifestations

A high sympathetic block


prevents compensatory vasoconstriction
blocks the sympathetic cardiac accelerator fibers
that arise at …?


Profound hypotension may occur

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Vasodilation combined with bradycardia and decreased
contractility
Exaggerated if venous return is further compromised


T1–T4
head-up position or gravid uterus
Sudden cardiac arrest sometimes seen with spinal anesthesia

Unopposed vagal tone
Cardiovascular Manifestations

Steps to minimize the degree of hypotension:

Volume loading with 10–20 mL/kg of IVF

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LUD in the third trimester of pregnancy




Increase IVFs
Autotransfusion - head-down position
Vasopressors (phenylephrine/ephedrine)
Excessive or symptomatic bradycardia


minimizes obstruction to venous return
Hypotension may still occur


partially compensates for the venous pooling
Atropine
If profound hypotension and/or bradycardia persist

Epinephrine (5–10 mcg)
Pulmonary Manifestations

Usually are minimal


diaphragm innervated by the phrenic nerve
with fibers originating from C3–C5
Even with high thoracic levels…


tidal volume is unchanged
only a small decrease in vital capacity


from loss of abdominal muscles' contribution to forced expiration
Phrenic nerve block may not occur even with total spinal
anesthesia

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apnea often resolves with hemodynamic resuscitation
suggests that brain stem hypoperfusion is responsible
Pulmonary Manifestations

Severe chronic lung disease patients
Rely upon accessory muscles of respiration
 Coughing and clearing of secretions require these muscles
 High levels of neural blockade impair these muscles

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

Use caution in patients with limited respiratory reserve
Must weigh against the advantages of avoiding airway
instrumentation and PPV
Surgery above the umbilicus

Pure regional technique may not be
the best choice
Pulmonary Manifestations

Thoracic or upper abdominal surgery
Decreased diaphragmatic function postop
 Decreased FRC
 Atelectasis and hypoxia via V/P mismatch


Postop thoracic epidural analgesia may improve
pulmonary outcome
decrease the incidence of
pneumonia and respiratory failure
 improve oxygenation
 decrease duration of vent
support

GI Manifestations
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Sympathetic outflow originates at T5–L1
Sympathectomy - vagal tone dominance

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

small, contracted gut with active peristalsis
Excellent operative conditions for lap procedures when
used as an adjunct to GENA
Postoperative epidural analgesia has been shown to hasten
return of GI function
Hepatic blood flow will decrease with reductions
in MAP from any anesthetic technique

Intraabdominal surgery - decrease in hepatic
perfusion related more to surgical manipulation
than to anesthetic technique.
Urinary Tract Manifestations

Renal blood flow – maintained through autoregulation

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Neuraxial anesthesia at the lumbar and sacral levels blocks both
sympathetic and parasympathetic control of bladder function
Loss of autonomic bladder control results in urinary
retention until the block wears off
If no urinary catheter is anticipated perioperatively:

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
little clinical effect upon renal function
use the shortest acting and smallest amount of
LA necessary for the procedure
limit the amount of IVF as much as possible
Monitored pt for urinary retention to avoid
bladder distention following neuraxial anesthesia
Metabolic & Endocrine Manifestations
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Surgical trauma produces a neuroendocrine response
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Clinical manifestations:
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HTN, tachycardia, hyperglycemia, protein catabolism, suppressed immune
responses, and altered renal function
Neuraxial blockade can partially suppress (during major invasive
surgery) or totally block (during lower extremity surgery) this stress
response
Reduction in catecholamine release


localized inflammatory response
activation of somatic and visceral afferent nerve fibers
increases in ACTH, cortisol, epinephrine, NE, and vasopressin
activation of the renin–angiotensin–aldosterone system
may decrease perioperative arrhythmias and reduce the incidence of
ischemia
Neuraxial block should precede incision and extend postop
Outline
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Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
Indications for Neuraxial


Used alone or in conjunction with GENA for most
procedures below the neck
Most useful for:

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Lumbar spinal surgery may also be performed
under spinal anesthesia
Upper abdominal procedures


lower abdominal
inguinal
urogenital
rectal
lower extremity surgery
difficult to achieve a sensory level adequate for patient comfort yet avoid the
complications of a high block
Spinal anesthesia for neonatal surgery
Contrandications
Absolute
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Patient refusal
Infection at the site of
injection
Coagulopathy or other
bleeding diathesis
Severe hypovolemia
Increased intracranial
pressure
Severe aortic stenosis
Severe mitral stenosis
Coagulopathy
Inability
Infection
Preexisting
or
to
Patient
atother
communicate
the
neurological
Sepsis
refusal
site
bleeding
of injection
with
deficits
diathesis
pt
Relative
Controversial

Preexisting
neurological deficits

Inability to
communicate with pt

Sepsis


Uncooperative patient
Prior back surgery at
site of injection

Demyelinating lesions

Complicated surgery

Stenotic valvular heart
lesions

Prolonged operation

Major blood loss
Severe spinal
deformity

Maneuvers that
compromise
respiration

Outline
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Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
Oral Anticoagulants

Long-term warfarin therapy
Must be stopped
 Need PT/INR to be normalized


Perioperative thromboembolic prophylaxis

If initial dose given > 24 h prior to the block or if more than
one dose was given


If only one dose given within 24 h


PT and INR need to be checked
Safe
Removing an epidural catheter from patients receiving lowdose warfarin (5 mg/d)

Safe
Antiplatelets

Aspirin and NSAIDs


Alone don’t appear to increase risk of spinal hematoma
More potent agents

Ticlopidine (Ticlid)


Clopidogrel (Plavix)


7 days
Abciximab (Rheopro)


14 days
48 h
Eptifibatide (Integrilin)

8h
Unfractionated Heparin

Minidose subQ prophylaxis


OK to proceed
Patients to receive heparin intraoperatively


1 h or more before heparin administration
A bloody epidural or spinal does not necessarily require cancellation of surgery



Removal of an epidural catheter



1 h prior to dosing
or 4 h following dosing
Patients on therapeutic doses of heparin (elevated PTT)


discussion of the risks with the surgeon
careful postoperative monitoring needed
Avoid neuraxial
The risk of spinal hematoma is undetermined in the setting of full anticoagulation
for cardiac surgery
LMWH (Enoxaparin, Dalteparin, -parin)

Intro of Lovenox in the US in 1993
 Reports of spinal hematomas associated
with neuraxial anesthesia
 Many involved intraop or early postop use,
and several also taking antiplatelets

If bloody needle or catheter placement occurs
 Delay until 24 hrs postop

Postop LMWH thromboprophylaxis if epidural catheter in place
 Remove 2 hrs prior to the first dose
 Or 10 hrs after last dose and subsequent dosing should not
occur for another 2 hrs
Fibrinolytic or Thrombolytic Tx

Best to avoid neuraxial.
Please note…

Drugs/regimens not considered to put pts at
increased risk of neuraxial bleeding when
used alone (minidose subQ heparin,
NSAIDS) may in fact increase the risk when
combined.
Outline
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Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
Which of the following statements regarding spinal
needle insertion is TRUE?
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



A. The first significant resistance encountered when advancing a needle
using the paramedian approach is the interspinous ligament.
B. If bone is repeatedly encountered at the same depth when the needle
is advanced, the needle is likely walking down the inferior spinous
process.
C. The midline approach is preferred in patients with heavily calicified
interspinous ligaments.
D. Free flow of CSF after resolution of a paresthesia usually indicates that
the needle is in a good position.
E. Penetration of the dura mater is more easily detected with a beveled
needle.
Answer

D.
 If
a paresthesia occurs you should immediately
stop advancing the needle and check for CSF.
 Obtaining CSF after resolution of a paresthesia
indicates the needle encountered a cauda
equina nerve root in the subarachnoid space
and the needle tip is in a good position.
 DO NOT inject LA in presence of a persistent
paresthesia!
Anatomic Approaches

Spinous processes

Cervical and lumbar spine – horizontal


Thoracic spine – slant in a caudal direction and can overlap


Most prominent is…?

Body of L4 or the L4–L5 interspace
Posterior superior iliac spine


Spinous process of T7
Highest points of both iliac crests (Tuffier's line) ?


C7
Inferior tip of the scapula at level of …?


Needle angled significantly more cephalad
First palpable cervical spinous process is C2


Needle directed with only a slight cephalad angle
S2 posterior foramina
Sacral hiatus

Depression just above or between the gluteal clefts and above the coccyx
Midline Approach





Body positioned with the plane of the back perpendicular to the floor
Palpate for depression between the spinous processes of the vertebra above and
below the level to be used
Subcutaneous tissues offer little feeling of resistance
Supraspinous and interspinous ligaments felt as an increase in tissue density
If bone contacted superficially

needle is likely hitting..?


If bone contacted at a deeper depth

and needle is in the midline it is likely hitting…?



the upper spinous process
or if it is lateral to the midline it is likely hitting…?


the lower spinous process
a lamina
Ligamentum flavum - obvious increase in resistance
At this point, spinal and epidural anesthesia differ
Paramedian Approach

May be useful in certain patients

severe arthritis

kyphoscoliosis

prior lumbar spine surgery

2 cm lateral to the inferior aspect of
superior spinous process

Penetrates the paraspinous muscles

lateral to the interspinous ligaments

needle may encounter little resistance
initially and may not seem to be in firm
tissue

Needle advanced at a 10–25° angle
toward the midline

LOR is often more subtle than with the
midline approach


Bone at a shallow
depth

medial part of the
lower lamina

redirect mostly
upward and slightly
more lateral
Bone encountered
deep

lateral part of the
lower lamina

redirected only
slightly upward,
more toward the
midline
Outline
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Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
Spinal Needles


Available in an array of sizes (16–30 gauge), lengths,
and bevel and tip designs
Tightly fitting removable stylet


avoids tracking epithelial cells into the subarachnoid space
2 broad groups
1. Sharp (cutting)-tipped

Quincke needle is a cutting needle with
end injection
2. Blunt tip (pencil-point) needles
Whitacre – rounded point with side injection
 Sprotte – rounded point with long side opening
 markedly decreased the incidence of PDPH

Spinal Catheters



Very small subarachnoid catheters are currently no
longer approved in the US
Association with cauda equina syndrome.
Larger catheters designed for epidural use are
associated with relatively high complication rates
when placed subarachnoid.
Spinal Anesthesia


Midline, paramedian, or
prone approach
Two "pops" are felt:
ligamentum flavum
 dura–arachnoid
membrane



Successful dural
puncture confirmed by
free flow of CSF
Persistent paresthesia
or pain upon injection

withdraw and redirect

Aspiration of CSF may
be necessary in certain
cases:
presence of low CSF
pressure (dehydrated
patient)
 prone position

Which of the following statements is FASLE?




A. A patient in the sitting position will have a higher
block if the solution is hypobaric and the patient
remains erect.
B. A patient placed supine and in the Trendelenburg
position is at high risk for developing a total spinal
block after injection of an isobaric solution.
C. A patient in the prone jackknife position should not
have a hyperbaric solution injected.
D. The normal lumbar lordosis limits the spread of
hyperbaric solution is a supine patient.
Answer


B.
An isobaric solution should not ascend to
cause a total spinal regardless of the patient’s
position.
Factors Affecting the Level of
Spinal Anesthesia
Most Important Factors




Baricity
Position of the patient
 During and
immediately after
injection
Dosage
Site of injection
Other Factors








Age
CSF
Curvature of the spine
Drug volume
Intraabdominal
pressure
Needle direction
Patient height
Pregnancy
Baricity 101

A hyperbaric solution of local anesthetic is denser (heavier) than CSF


Hypobaric solution is less dense (lighter) than CSF




Hyperbaric solution - settles caudad
Hypobaric solution - ascends cephalad
Lateral position



Hyperbaric solution - spreads cephalad
Hypobaric anesthetic solution - moves caudad
A head-up position


Addition of sterile water
Head-down position


Addition of glucose
Hyperbaric spinal solution - greater effect on dependent (down) side
Hypobaric solution - higher level on nondependent (up) side
Isobaric solution tends to remain at the level of injection
Baricity 101

Hyperbaric solutions tend to move to the most dependent area of the
spine
 T4–T8 in the supine position

Apex of the thoracolumbar curvature is T4
 In the supine position, this should limit a hyperbaric solution to
produce a level of anesthesia at or below T4

Abnormal curvatures of the spine, such as scoliosis and kyphoscoliosis,
have multiple effects on spinal anesthesia

Difficult landmarks

Decreased CSF
Baricity 101

CSF has a specific gravity of 1.003–1.008 at 37°C
Agent
Specific Gravity
Bupivacaine
0.5% in 8.25% dextrose
1.0227–1.0278
0.5% plain
0.9990–1.0058
Lidocaine
2% plain
1.0004–1.0066
5% in 7.5% dextrose
1.0262–1.0333
Procaine
10% plain
1.0104
2.5% in water
0.9983
Tetracaine
0.5% in water
0.9977–0.9997
0.5% in D5W
1.0133–1.0203
Spinal Anesthesia



CSF volume inversely correlates with level of anesthesia
Increased intraabdominal pressure or conditions that cause
engorgement of the epidural veins, thus decreasing CSF
volume, are associated with higher blocks
 Pregnancy
 Ascites
 Large abdominal tumors
Conflicting opinion exists as to whether
increased CSF pressure caused by
coughing or straining, or turbulence
on injection has any effect on the spread of LA
Spinal Agents
Drug
Preparation
DOA (plain)
DOA (w/epi)
Procaine
10% solution
45
60
Bupivacaine
0.75% in 8.25%dextrose
90-120
100-150
Tetracaine
1% solution in 10%glucose
90-120
120-240
Lidocaine
5% in 7.5%glucose
(dilute to 2.5% or less)
60-75
60-90
Ropivacaine
0.2-1%solution
(Off-label use)
90-120
90-120

Only preservative-free solutions used

Addition of vasoconstrictors (epi or neo) and opioids may enhance the
quality and/or prolong the duration of spinal anesthesia
Spinal Agents

Hyperbaric bupivacaine and tetracaine are two of the most commonly
used agents for spinal








Relatively slow in onset (5–10 min)
Prolonged duration (90–120 min)
Similar sensory levels
Tetracaine more motor blockade
Addition of epi to bupivacaine prolongs its duration only modestly
In contrast, epi to tetracaine prolongs by more than 50%
Phenylephrine also prolongs tetracaine anesthesia but has no effect on
bupivacaine
Ropivacaine


Experience with spinals is more limited
A 12-mg intrathecal dose of ropivacaine is roughly equivalent to 8 mg of
bupivacaine, but it appears to have no particular advantages for spinal
anesthesia
Spinal Agents

Lidocaine and procaine
rapid onset (3–5 min) and short duration of action (60–90
min)
 modest if any prolonged effect with epi


Lidocaine associated with transient neurological
symptoms (TNS) and cauda equina syndrome

TNS: back pain radiating to the legs without sensory or motor
deficits after resolution of spinal


resolves spontaneously within several days
Some experts suggest that lidocaine can be safely used
as a spinal anesthetic if the total dose is limited to 60
mg and diluted to 2.5% or less
Outline










Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
Epidural Anesthesia

The epidural space surrounds the dura mater posteriorly, laterally, and anteriorly

Contents of Epidural Space:


Nerve roots

Fatty connective tissue

Lymphatics

Rich venous (Batson's) plexus

Septa or connective tissue bands
Epidural anesthesia is slower in onset (10–20 min) and may not be as dense as a spinal


Can cause a pronounced differential or segmental block that can be useful clinically
Relatively dilute concentrations of a LA combined with an opioid:

Block the smaller sympathetic and sensory fibers and spare the larger motor fibers


= analgesia without motor block
Segmental block – LA not readily spread by CSF so confined close to level it was injected

Characterized by a well-defined band of anesthesia at certain nerve roots

Nerve roots above and below are not blocked

Ex. thoracic epidural
Epidural Needles



Typically 17–18 gauge
9cm to hub
Tuohy needle most commonly used




Blunt bevel with a gentle curve of
15–30° at the tip
Pushes away the dura after passing
through the ligamentum flavum instead
of penetrating it
Straight needles without a curved tip
(Crawford needles) may have a higher
incidence of dural puncture but facilitate
passage of an epidural catheter.
Needle modifications include winged
tips and introducer devices set into the
hub designed for guiding catheter
placement.
Epidural Catheters






Continuous infusion or intermittent boluses
May allow a lower total dose of anesthetic to be used
Intraop and/or postop analgesia
19- or 20-gauge catheter is introduced through a 17- or 18-gauge epidural needle
Bevel opening directed either cephalad or caudad, and catheter advanced 2–6 cm
The shorter the distance advanced:


more likely it is to become dislodged
The further the catheter is advanced:

greater the chance of a unilateral block






exiting the epidural space via an intervertebral foramen
coursing into the anterolateral recesses
Single port at the distal end or multiple side ports close to a closed tip
Some have a stylet for easier insertion
Spiral wire-reinforced catheters are very resistant to kinking
The spiral or spring tip is associated with fewer, less intense paresthesias and may be
associated with a lower incidence of inadvertent intravascular insertion
Epidural Techniques

LOR technique most commonly used
 Needle advanced through subQ tissues with the stylet in place
 Once interspinous ligament entered (increase in tissue resistance), stylet
removed
 Glass syringe filled with approximately 2 mL of fluid or air is attached
 If tip of needle is within the ligament, gentle attempts at injection are met
with resistance
 Needle slowly advanced, millimeter by millimeter, with either continuous or
rapidly repeating attempts
 As tip enters the epidural space there is a sudden LOR and injection is easy

Hanging Drop Technique
http://www.youtube.com/watch?v=7kDi47vqBis

Variation of Hanging Drop Technique
http://www.youtube.com/watch?v=TvCBDamF4jQ&feature=related
Activating an Epidural





Quantity LA for epidural anesthesia is very large compared to spinals
Significant toxicity can occur if injected intrathecally or intravascularly
Safeguards against this: epidural test dose and incremental dosing
Test dose detects both subarachnoid and IV injection
Classic test dose: 3mL of 1.5% lidocaine with 1:200,000 epinephrine (5mcg/mL)







45mg of lidocaine injected intrathecally – rapidly apparent spinal anesthesia
15 mcg of epinephrine injected intravascularly – noticeable increase in heart rate (20% or
more) with or without hypertension
False positives (uterine contraction causing pain or an increase in heart rate coincident to
test dosing)
False negatives (patients taking beta blockers)
25% or more increase in T-wave amplitude on EKG may be more reliable sign of IV injection
Both fentanyl and larger doses of local anesthetic without epinephrine have been
advocated as intravenous injection test doses
Simply aspirating prior to injection – insufficient to avoid inadvertent IV injection
Activating an Epidural

Incremental dosing is a very effective method of avoiding
serious complications



Fraction of the total intended LA dose, typically 5 mL
Should be large enough for mild symptoms of IV injection to occur but
small enough to avoid seizure or cardiovascular compromise.
If a clinician uses an initial test dose, is diligent about
aspirating prior to each injection, and always uses
incremental dosing, significant systemic toxicity or
inadvertent intrathecal injections are rare.
Outline










Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
When using a caudal approach to the epidural
space, which of the following is TRUE?





A. The patient must be prone.
B. An inadvertent subarachnoid block is much
less likely than when using the lumbar
approach.
C. The technique becomes relatively more
contraindicated as the patient’s age decreases.
D. Small volumes of agent are needed since the
volume of the canal is only 8-12ml.
E. The needle enters through the sacral hiatus.
Answer





E.
Canal is of low volume but there is leakage through
the foramina requiring injection of a larger volume
compared to the lumbar approach.
Pt can be prone or lateral decubitus.
Inadvertent dural puncture is very possible.
Caudal approach is technically easier than lumbar
approach in babies, and is becoming increasingly
more popular in pediatric anesthesia.
Caudal Anatomy
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
Caudal space is considered the sacral portion of the epidural space
Sacral vertebrae fuse into one large bone – the sacrum
Each one retains discrete anterior and posterior intervertebral foramina
Laminae of S5 and all or part of S4 normally do not fuse, leaving a
caudal opening to the spinal canal, the sacral hiatus
Sacrococcygeal ligament covers the sacral hiatus
Caudal Anatomy



Hiatus felt as a as a groove or notch above the coccyx
and between two bony prominences – the sacral cornua
More easily appreciated in infants and children
Posterior superior iliac spines and the sacral hiatus
define an equilateral triangle
Caudal Epidural Anesthesia






One of the most commonly used regional
techniques in pediatric patients
Used in anorectal surgery in adults
2nd stage of labor
In children - typically combined with GENA
for intraop supplementation and postop analgesia
Performed after induction
Commonly used for procedures below the diaphragm


Within the sacral canal, the dural sac extends to…what level?



urogenital, rectal, inguinal, and lower extremity
S2 in adults
S3 in infants
Makes inadvertent intrathecal injection much more common in infants
Caudal Epidural Technique

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
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
Position lateral or prone with one
or both hips flexed
Palpate sacral hiatus
Sterile skin prep
Needle advanced at a 45° angle
cephalad until a pop is felt
(sacrococcygeal ligament)
Angle flattened and advanced
Aspirate for blood and CSF
If negative, proceed with injection
Test dose vs incremental dosing
with frequent aspiration
Caudal Anesthesia


Complication rate for "kiddie caudals" is very low
 Total spinal and IV injection causing seizure or cardiac
arrest
 Intraosseous injection has also been reported to cause
systemic toxicity
Calcification of the sacrococcygeal ligament may make caudal
anesthesia difficult or impossible
in older adults
Pediatric Caudal Anesthesia


Dose: 0.5–1.0 mL/kg of 0.125–0.25% bupivacaine
(or ropivacaine) +/- epi
Opioids may be added (ex 50–70 mcg/kg of morphine)



Duration can extend for hours into the postop period
Ok to d/c home even with mild residual motor block or
without urinating


not recommended for outpatients - delayed respiratory depression
most children will urinate within 8 h
Higher epidural levels can be accomplished with
catheters threaded cephalad into the lumbar or
even thoracic epidural space
Caudal in Adults




Dense sacral sensory blockade with limited
cephalad spread for anorectal procedures
Prone jackknife position
Dose 15–20 mL of 1.5–2.0% lidocaine +/- epi
Fentanyl 50–100 mcg may also be added
Outline










Anatomy
Mechanism of Action
Systemic Manifestations
Indications/Contrandications
Anticoagulants/Antiplatelets
Anatomic Approaches
Spinal Anesthesia
Epidural Anesthesia
Caudal Anesthesia
Complications
All of the following statements regarding complications associated
with epidural and spinal anesthesia are true EXCEPT:





A. Use of fluid instead of air for LOR during epidural
anesthesia reduces the risk of headache upon accidental
dural puncture.
B. An epidural blood patch immediately relieves PDPH
symptoms in 99% of pts.
C. Transient reduction in hearing acuity after spinal
anesthesia is more common in female than in male patients.
D. Back pain is more common after epidural anesthesia than
after spinal anesthesia.
E. Neurologic injury occurs in about 0.03% to 0.1% of all
central neuraxial blocks.
Answer

B

90% not 99%
All of the following statements regarding spinal or epidural
anesthesia and spinal hematoma are true EXCEPT:





A. Pts taking NSAIDS and receiving mini dose heparin are not
at increased risk.
B. Pts treated with enoxaparin are at increased risk.
C. Pts most commonly present with numbness or lower
extremity weakness.
D. Spinal hematoma occurs at an estimated incidence of less
than 1:150,000.
E. The removal of an epidural or an intrathecal catheter
presents nearly as great a risk for spinal hematoma as its
insertion.
Answer


A
Combination may put patients at increased
risk.
Complications related to
needle/catheter placement





Adverse or exaggerated
physiological responses






Urinary retention
High block
Total spinal anesthesia
Cardiac arrest
Anterior spinal artery syndrome
Horner's syndrome










Drug toxicity



Systemic local anesthetic toxicity


Transient neurological symptoms


Cauda equina syndrome




Trauma
Backache
Dural puncture/leak
Postdural puncture headache
Diplopia
Tinnitus
Neural injury
Nerve root damage
Spinal cord damage
Cauda equina syndrome
Bleeding
Intraspinal/epidural hematoma
Misplacement
No effect/inadequate anesthesia
Subdural block
Inadvertent subarachnoid block1
Inadvertent intravascular injection
Catheter shearing/retention
Inflammation
Arachnoiditis
Infection
Meningitis
Epidural abscess
THE END