Transcript file

Epidural Anaesthesia
Dr. Hadab Ahmed Mohamed
Associate Professor of Anaesthesia, Faculty of Medicine,
University of Khartoum
Epidural Anesthesia

1)
2)
3)
Objectives:
Introduction
Anatomy and Physiology
Techniques
Introduction

Epidural is a neuraxial technique that offers a wider
range of applications than spinal anaesthesia in terms
of site, uses& administration
Sites: Can be performed at the cervical, thoracic,
lumbar and sacral level
Uses: Operative anaesthesia, labor analgesia,
postoperative pain control and chronic pain
management
Administration: It can be used as a “Single Shot” or
with a catheter that allows intermittent boluses or a
continuous infusion
Introduction


1)
2)
One advantage of an epidural is that the
muscle blockade can range from none to
complete
This can be regulated by:
Choice of drug
Concentration of LA
Anatomy

The epidural space
surrounds the dura mater
posteriorly, laterally and
anteriorly
Anatomy

1)
2)
3)
4)
5)
The contents of the epidural space are:
Spinal nerve roots
Fatty tissues
Lymphatics
Venous plexus.
Septa and connective tissue bands
Anatomy

Bounderies:
Superior: Fusion of the dura with the
foramine magnum.
Inferior: Sacroccygeal membrane.
Lateral: Pedicles & intervertebral foraminae.
Anterior: Posterior longitudinal ligament,
vertebral bodies& intervertebral discs.
Posterior: Laminae& ligamentum flavum.
Physiology



A solution injected into the epidural space
spreads horizotally& longitudinally.
Horizontal spread is to the region
surrounding the dura, with diffusion into
the CSF and leakage through the
intervertebral foramen into paravertebral
spaces
Longitudinal spread is in cranial and
caudal directions from the level at which
the drug is administered.
Physiology

1)
2)
3)
4)
5)
6)
Possible sites of anaesthetic action
include:
Subdural& epidural spinal nerve roots
Paravertebral nerve roots
Dorsal and ventral spinal nerve roots
Dorsal root ganglia
The spinal cord
The brain itself
Physiology


The higher& lower levels of the block are
regulated by the volume of LA; relatively
LARGE volumes of LA are needed to
achieve a block that spans several
dermatomes
Where spinal anaesthesia affects
EVERYTHING distal to the level of the
block; epidural is a DIFFERENTIAL
(DERMATOMAL) block dependent on the
volume and site of injection
Advantages over spinal A.


1)
2)
3)
4)
Better control of anaesthetic level (and also of
sympathetic blockade)
Epidural techniques allow for the placement of
a continuous catheter which is especially useful
for:
Cases of unpredictable duration of surgery
Prolonged postoperative analgesia
Chronic pain control
Labor analgesia
Spread of Anaesthesia

Baricity plays a VERY small factor when
dealing with epidurals, whereas in a
spinal, baricity is a KEY factor in spread
and distribution of the block
Spread of Anaesthesia

1)
2)
3)
4)
5)
6)
7)
8)
9)
The factors that affect the level of the Epidural block
are:
Injection site
Dose
Volume
Concentration
Position
Age
Height and weight (?)
Pregnancy (?)
Speed of injection (?)
Injection Site



Injection site is the most important determinant
of the spread of an epidural block
Unlike spinal anaesthesia, epidural anaesthesia
produces a segmental block that spreads both
caudally and cranially
The injection site should be in the MIDDLE of
the range of dermatomes that needs to be
blocked and closest to the main nerve roots
involved
Recommended doses& injection site
Procedure
Catheter position
Dose (ml)
Chest
T12-L2
8-12
Upper abdomen
Cholecystectomy
L2
12-16
Gastric resection
L2
12-16
Incisional pain
L2
7-10
Lower abdomen
Colon resection
L2
12-16
Repair of aortic aneurysm
L2
12-16
Herniorrhaphy
L3
8-12
Prostatectomy
L3
12-16
Hysterectomy
L3
10-14
Lower extremities
L4
10-14
Perineum
L4
8-12
Back& flanks
L2
10-14
Vaginal delivery
1st stage
2ond stage
L3
L3
5-7
10-12
Injection Site


Thoracic epidural is ideally suited for
procedures of the chest and upper
abdomen or for relief of postoperative
thoracotomy pain with a catheter being
placed for intermittent dosing or
continuous infusions
When using a thoracic approach, smaller
volumes are selected to prevent cranially
spread
Injection Site


Caudal epidural blocks are largely restricted
to sacral and low lumbar dermatomes
Lumbar epidural injections of 10cc tend to
spread caudad to include all the sacral
dermatomes; if increased to 20cc volumes, it
will produce much better quality sacral
blocks and can also extend cranially to
include the midthoracic levels
Concentration

Within the range typically used for surgical
anaesthesia, drug CONCENTRATION is
relatively unimportant in determining
block spread, but only affects the
DENSITY of the block
Dose & Volume


DOSE & VOLUME, however, are important
variables in determining both spread and
quality of the epidural block obtained.
Increasing the volume of LA (and thereby
increasing the DOSE) results in
significantly greater average spread.
Dose, Volume
Recommended volumes of LA differ as to
which level is being injected:
Cervical/Thoracic doses are 0.7 to 1cc per
segment with an initial volume of 10cc
Lumbar level doses are 1.25 – 1.5cc per
segment with an initial volume of 15-20cc
 This is due to the narrowing of the spinal
canal as it progresses cranially

Concentration and Differential
Block

Using a lower concentration anaesthetic
can sometimes give you a differential
block; blocking sensory and pain fibers
over larger muscle fibers in the center of
the nerves
Concentration and Differential
Block
An example of this is used in obstetrics:
Bupivicaine 0.25%, 20cc, usually ONLY
provides a sensory block but leaves the
motor fibers intact so the patient can push
when needed to
If bupivacaine 0.5% is given with the same
volume, then a sensory as well as motor
block is obtained, paralyzing the muscles
at the levels of the block so NO pushing is
going to be possible

Position

Studies have shown small to NO
differences in spread of block when
comparing the lateral& sitting positions;
it’s your preference which position to use
Age


Most studies that have examined the
effect of age on epidural blocks have
demonstrated a greater spread in older
patients
This is thought to be related to a less
compliant epidural space and dura mater
Height and Weight

The correlation between patient height or
weight and spread of epidural block is
very weak at best and seems to have no
clinical significance
Pregnancy




Studies are conflicting
Some have shown a greater spread at
TERM and early in pregnancy
Other studies have shown no significant
differences in level of spread between
pregnant and non-pregnant patients
?????????????
Speed of Injection


The speed of injection has NEVER been
shown to make any difference
The LA should be injected in increments of
3-5cc every 3 minutes and titrated to the
desired anaesthetic level
Onset of Blockade





The onset of an epidural block can usually be
detected within 5 minutes in the dermatomes
immediately surrounding the injection site
The time to PEAK effect differs somewhat
among different LA’s
Shorter acting drugs usually reach their
maximum spread in 15-20 minutes
Longer acting LA’s usually reach their maximum
spread in 20-25 minutes
Increasing the DOSE of LA SPEEDS the onset of
both motor and sensory block
Duration of Block

1)
2)
3)
4)
The DURATION of the epidural block
depends on:
The LA selected
Dose given
Patient age
Use of adrenergic agonists
Local Anaesthetics & Duration

Chlorprocaine is shortest, Lidocaine &
Mepivicaine are intermediate and
Bupivicaine and Ropivicaine produce the
longest lasting epidural blocks
Dose

DOSE: Increasing the DOSE of a LA
results in increased duration AND density
of the block
Age

AGE: For unknown causes the duration of
action of epidural is prolonged in the
elderly population
Adrenergic Agents and
Duration


Adrenaline in a concentration of 5
micrograms/cc (1:200,000) is the most
common adrenergic agent added to
epidural LA’s
It has been shown to prolong the blocks
of Lidocaine and Mepivicaine by as much
as 80%
Adrenergic Agents and
Duration


Adrenaline has been shown NOT to
significantly prolong the duration of
anaesthesia when added to concentrated
solutions of Bupivacaine and Ropivacaine
used for surgical anaesthesia
However, when added to more dilute
concentrations of Bupivacaine, as used for
obstetric analgesia, it has been shown to
increase the duration AND quality of the
block
Break Time!!
Technique



Patient preparation and positioning are
similar to spinal anaesthesia
Either the sitting or lateral decubitus
positions can be used
Emergency drugs, equipments and
monitors should be immediately available
and you need to be prepared to use them
if any thing goes wrong
Technique




The angles of approach for the
various levels are markedly different
The lumbar region is at or greater
than 90 degrees to the skin
The thoracic is at a much more
acute angle due to the anatomical
arrangement of the thoracic spinous
processes
Finally the cervical is at an angle in
between the previous two
Technique

1)
2)
3)
The lumbar region is by far the easiest due
to:
The angle of the spinous processes provides
a larger spaces BETWEEN adjacent spines
Easily identifiable location by using easy to
find landmarks (Iliac crests)
Width of epidural space is greatest at this
level
Technique

With spinal anaesthesia, the practitioner
seeks CSF by piercing the dura; while in
epidural anaesthesia, the negative
pressure in the epidural space is targeted
by using the loss of resistance technique.
Technique


Epidural is most often
performed with a 16, 17 or 18
gauge needle with a BLUNTED
tip designed to facilitate
passage& direction of a catheter
into the epidural space (Tuohy
or Crawford needles)
The blunted tip is designed
specially to just inwardly push
(tenting) the dura without
puncturing it
Technique





The procedure is begun by fixing a reliable IV
line for fluid loading& drug administration
Identify the anatomical landmarks& locate the
planned interspace of needle insertion
Then the patient is positioned similar to that of
spinal anaesthesia
A sterile preparation is performed to the
planned insertion site, including the anatomical
land mark
Epidural set is checked and drugs are prepared
Technique


Local anaesthetic (usually Lidocaine 1-2%
plain) is injected at the planned insertion
site and a skin wheal is raised using 25G
skin needle
The skin is punctured with the sharp
needle to facilitate the passage of the
blunt epidural needle
Technique



The epidural needle is placed
bevel up and introduced into
the skin
Firmly place the BACK of your
non-dominant hand against the
patient’s back and grasp the
epidural needle by the thumb&
index fingers
This stabilizes the needle and
prevents any unwanted
movement either in or out
which is especially critical once
you find the epidural space
Technique


The needle is passed slowly through
the supraspinous ligament and
seated in the interspinous ligament
before the stylet is removed
You can tell that the needle is
seated in the interspinous ligament
if it stays still without support
Technique




After the stylet is removed, the Loss Of Resistance
(LOR) syringe is attached to the needle which is
slowly advanced.
The LOR syringe is typically made of
glass and is filled with either 3-4cc of air,
normal saline, or a mixture of saline and
air. Newer, commercially available
disposable epidural packs contain a
plastic syringe with a plunger that has
very low resistance.
As the syringe/needle complex is
advanced, pressure is intermittently
applied to the plunger of the syringe
(Loss of Resistance technique)
The pattern is “move-bounce-move-bounce-movebounce” until a sudden LOR is obtained
Technique




The syringe/needle complex should only be
moved 0.5-1cm at a time and then tested for
resistance or LOR
The syringe/needle complex is advanced by
applying pressure to the NEEDLE (by the needle
supporting hand) and not the syringe
As the needle passes through the Ligamentum
Flavum, resistance increases and you may feel a
distinct “pop” as you pass through it
Once you pass through the LF, you will
experience an immediate LOR and then the tip
of the needle will be in the epidural Space
Technique



Once in the epidural space, begin first by
injecting a “TEST” dose of 3cc of LA ±
adrenaline.
Then check for inadvertent intravascular and
subarachnoid injection
If you are intravascular, you will see an
increase in heart rate within 30 seconds
Technique


With dural puncture by accident, the test
dose should produce numbness in the
lower extremities
This can take up to three minutes to
occur, so you need to wait at least three
minutes before continuing your injection
of LA
Technique

Then either a catheter is passed through
the needle, a bacterial filter fixed at its
end and the total dose injected via the
catheter, or the total dose is injected
through the needle ± catheter insertion
Technique



As you pass the catheter, you may initially
feel resistance at the tip of the needle
A slightly stronger push may be needed
and then you will feel the resistance drop
and the catheter will thread smoothly
It should be inserted between 3-5cm in
the epidural space and no more (3-5 little
black lines)
Technique


The catheter is then fixed to the back of
the patient, with adhesive plaster, with its
proximal end (containing the bacterial
filter) above the patient’s shoulder
The patient is then positioned supine
before testing for the intensity and level of
epidural block (timing varies with the drug
used).
CAUTION



NEVER pull the catheter back through
the needle once it has been inserted
It is possible to catch the catheter on the
needle tip and shear or cut the tip off
Then it becomes a permanent new
addition to the epidural space and will be
there for the rest of the patient’s life!!!!
Caudal Anaesthesia



An epidural technique used for anorectal
surgery in adults and for post operative
analgesia in pediatric lower abdominal&
pelvic surgeries
Technique is the same for both patient
populations
Difference lies with size of equipment and
dosage of anaesthetics
Caudal Anaesthesia



Caudal anaesthesia involves needle or
catheter penetration of the sacrococcygeal
membrane, covering the sacral hiatus to
reach the sacral epidural space
The hiatus is created by the unfused S4
and S5 laminae
The hiatus can be felt as a groove or
notch above the coccyx and between two
bony prominences, the sacral cornua
Caudal Anaesthesia





The posterior superior iliac spines and the sacral
hiatus form an equilateral triangle, with its tip
over the sacral hiatus
The patient is placed either prone or in lateral
decubitus position
A sterile preparation is done similar to an
epidural and the landmarks are again palpated
A needle or catheter is inserted at a 45 degree
angle to the skin until a “pop” is felt
Then the angle of the needle is dropped down
and advanced, aspirating for blood or CSF every
1-2cm
Caudal Anaesthesia

Repeated injections can be given or
a catheter can be placed for boluses or
a continuous infusion
Caudal Anaesthesia


A dose of 15-20cc of 1.5-2.0% Lidocaine±
adrenaline is usually effective for adults
undergoing anorectal procedures
This technique should be avoided in patients
with pilonidal cysts or any infection at the site of
injection because bacteria can be introduced
into the epidural space and lead to infection and
abscess formation
Complications
Immediate
 Hypotension
 Urinary retention
 Local anaesthetic toxicity
 Local anaestheticinduced cardiac arrest
Delayed
 Postdural puncture headache
 Transient backache
 Epidural abscess or meningitis
 Permanent neurologic deficit