briefly reviews the anatomy, surface anatomy, and ... · epidural space the dura mater is indented...
Transcript of briefly reviews the anatomy, surface anatomy, and ... · epidural space the dura mater is indented...
Spinal anesthesia
Rahmeh Alsukkar
Anatomy
The vertebral column consists of 33 vertebrae: 7 cervical,
12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal
segments. The vertebral column usually contains three
curves. The cervical and lumbar curves are convex
anteriorly, and the thoracic curve is convex posteriorly
Five ligaments hold the spinal column together. The supraspinous
ligaments connect the apices of the spinous processes from the
seventh cervical vertebra (C7) to the sacrum. The supraspinous
ligament is known as the ligamentum nuchae in the area
above C7. The interspinous ligaments
connect the spinous processes together.
The ligamentum flavum, or yellow ligament, connects the laminae
above and below together. Finally, the posterior and anterior longitudinal ligaments bind the
vertebral bodies together.
The three membranes that protect the spinal cord are the dura
mater, arachnoid mater, and pia mater.
The dura mater, or tough mother, is the outermost layer.
The dural sac extends to the second sacral vertebra (S2). The arachnoid mater is the
middle layer, and the subdural space lies between the dural
mater and arachnoid mater. The arachnoid mater, or cobweb
mother, also ends at S2, like the dural sac. The pia mater, or soft mother, clings to the surface of the spinal cord and ends in the filum terminale, which helps to
hold the spinal cord to the sacrum.
The space between the arachnoid and pia mater is known as the
subarachnoid space, and spinal nerves run in this space, as does
CSF
Spinal Cord Extends from foramen magnum to
/upper in 1L of border lower : dultA
border of L2
Infants/children : L3
It is about 45 cm long
Duramater, Subarachnoid space &
subdural space: S2 in adults( S3 in
children)
S. C gives 31 pairs of spinal nerve
FILUM the , piamater of extension An
attach and dura the penetrate TERMINALE
the terminal end of spinal cord [conus
medullaris]to the periosteum of the coccyx
When preparing for spinal anesthetic blockade, it is important to accurately identify
landmarks on the patient
Derma
tomal
Level
Surface Landmark
C8 Little finger
T1,T2 Inner aspect of the arm
T4 Nipple line, root of
scapula
T7 Inferior border of
scapula ,Tip of xiphoid
T10 Umbilicus
L2 to
L3
Anterior thigh
S1 Heel of foot
Dermatomes
SURFACE ANATOMY
Anatomic Landmarks to Identify Vertebral
Levels
Anatomic
Landmark
Features
C7 Vertebral prominence, the most
prominent process in the neck
T7 Inferior angle of the scapula
L4 Line connecting iliac crests
S2 Line connecting the posterior
superior iliac spines
Sacral
hiatus
Groove or depression just above
or between the gluteal clefts
above the coccyx
Positions
Lateral Decubitus Position
A commonly used position for placing a spinal anesthetic is the lateral decubitus position.
Ideal positioning consists of having the back of the patient parallel to the edge of the bed
closest to the anesthesiologist, with the patient’s knees flexed to the abdomen and
neck flexed It is beneficial to have an assistant to help
hold and encourage the patient to stay in this position.
Sitting Position
The sitting position is utilized for low lumbar or sacral anesthesia and in instances when the
patient is obese and there is difficulty in finding the midline in the lateral position.
When performing a saddle block, the patient should remain in the sitting position for at
least 5 min after a hyperbaric spinal anesthetic is placed to allow the spinal to
settle into that region.
Prone Position
The prone position is utilized for spinal anesthesia if the patient needs to be in this position for the surgery, such as for rectal,
perineal, or lumbar procedures.
When performing a spinal anesthetic, appropriate
monitors should be placed, and airway and
resuscitation equipment should be readily available.
All equipment for the spinal blockade should be ready
for use, and all necessary medications should be drawn
up prior to positioning the patient for spinal anesthesia.
Adequate preparation for the spinal reduces the
amount of time needed to perform the block and assists
with making the patient comfortable.
Proper positioning is the key to making the spinal
anesthetic quick and successful.
Technique of Lumbar Puncture
Once the patient is correctly positioned, the midline
should be palpated. The iliac crests are palpated, and a
line is drawn between them in order to find the body of L4
or the L4-5 interspace.
Other interspaces can be identified, depending on where
the needle is to be inserted.
The skin should be cleaned with sterile cleaning solution,
and the area should be draped in a sterile fashion.
A small wheal of local anesthetic is injected into the skin
at the site of insertion.
More local anesthetic is then administered along the
intended path of the spinal needle insertion to a depth of 1
to 2 in.
1. MIDLINE APPROACH
2. PARAMEDIAN APPROACH
Midline Approach Paramedian
approach
Skin Skin
Subcutaneous fat Subcutaneous fat
Supraspinous ligament
Interspinous ligament
Ligamentum flavum Ligmentum flavum
Dura mater Dura mater
Subdural space Subdural space
Arachnoid mater Arachnoid mater
Subarachnoid space Subarachnoid space
Spinal : approaches
Structure Pierced
Midline Approach
The back should be draped in a sterile fashion.
The .felt are “pops” Two needle of advancement With
the is second & flavum .L the of penetration is first
penetration of dura-arachnoid membrane.
The stylet is then removed, and CSF should appear
at the needle hub.
For spinal needles of small gauge (26-29 gauge), this
usually takes 5-10 sec
Paramedian Approach
•Calcified interspinous ligament or difficulty in flexing the
spine
•The needle should be inserted 1 cm lateral and 1 cm
inferior of the superior spinous process of desired level.
Angle should be 10-25 toward midline
•The ligamentum flavum is usually the first resistance
identified.
SPINAL NEEDLE
QUINCKE WHITACRE SPROTEE
two Spinal needles fall into
main categories:
: duracut the ) those that i(
Quincke- Babcock
needle, the traditional
disposable spinal needle
(iI) those with a conical
tip(Pencil tip) : Whitacre
and Sprotte needles
If a continuous spinal
technique is chosen, use of
a Tuohy or Hustead needle
can facilitate passage of the
catheter
Blunt tip (pencil-point)
needle decreased the
incidence of PDPH
Sprotte is a side-
injection needle with a
long opening.
It has the advantage of
more vigorous CSF flow
compared with similar
gauge needles.
epidural anesthesia
Anatomy
Epidural Space
The epidural space is the area between the dura mater (a membrane) and the vertebral wall, containing fat and small blood vessels. The space is located just outside the dural sac which surrounds the nerve roots and is
filled with cerebrospinal fluid. •
Patient Positioning There are three positions used for the
administration of epidural anesthesia: sitting , lateral decubitus , and prone.
Sitting Position
1. Easier to identify midline, particularly in obese and scoliotic patients 2. Practitioners more experienced in sitting position 3. Shorter procedure time 4. Shorter distance from skin to epidural space 5. Greater cephalad spread of hypobaric solution
Advantages of sitting position
Lateral Decubitus Position
1. Sedation can be used more liberally Reduced patient movement 2. Increased patient comfort 3. Improved patient cooperation 4. Improved patient satisfaction 5. Reduced catheter displacementDecreased incidence of epidural vein cannulation 6. Attenuation of vagal reflexes 7. Hemodynamic changes better tolerated Bedside assistance may not be 8. required Intentional unilateral block for surgical procedures feasible
Using local anaesthetic raise a subcutaneous wheal at the midpoint between two adjacent vertebrae.
Inflitrate deeper in the midline and paraspinously to anaesthetise the posterior structures.
Insert epidural needle to the skin at this point, and advance through the supraspinous ligament, with the needle pointing in a slightly cephalad direction. Then advance the needle into the interspinous ligament,
which is encountered at a depth of 2-3 cm.until distinct sensation of increased resistance is felt as the
needle passes .
Technique of Epidural Anaesthesia
* With 5-10ml of air in the syringe, attach it to the hub of the needle once it has entered the interspinous ligament. The plunger is gently
pressed, and if there is resistance ("bounce"), the needle is very carefully advanced, with the dorsum of both hands resting against
the back to provide stability. * After 2-3mm, the plunger is again gently pressed, and this
procedure is repeated as the needle is carefully advanced through the tissues.
* The distinctive decrease in resistance when the needle enters the ligamentum flavum is felt, and the process is continued in 2mm
increments. * There is usually a distinctive "click" when the needle enters the
epidural space, and provided great care is taken, and the needle only advanced in 2mm increments, the needle should stop before it
reaches the dura. * At this point air can be injected into the epidural space very easily.
The syringe is removed and the catheter threaded as below.
* Remove the syringe and thread the catheter gently via the needle into the epidural space.
* The catheter has markings showing the distance from its tip, and should be advanced to 15-18cm at the hub of the needle, to ensure that a sufficient length of catheter has
entered the epidural space. * Remove the needle carefully, ensuring that the catheter is
not drawn back with it. * The markings on the needle will show the depth of the
needle from the skin to the epidural space, and this distance will help determine the depth to which the
catheter should be inserted at the skin. * For example, if the needle entered the epidural space at a
depth of 5cm, the catheter should be withdrawn so that the 10cm mark is at the skin, thus leaving approximately
5cm of the catheter inside the epidural space, which is an appropriate length.
There are four common approaches to the epidural space: midline, paramedian, Taylor
(modified paramedian), and caudal
approaches
With the midline technique, a Tuohy needle is introduced, directed slightly cephalad, through the skin in the midline
between the two spinous processes at the level of the desired block. The needle passes through the supraspinous ligament, the interspinous ligament and the fused pair of ligamentum flavae before it enters the epidural space. A
sudden ‘give’ may be felt as the needle tip exits the ligamentum flavum and enters the epidural space
Lateral deviation or a “wobbly” needle indicates that the needle is not properly engaged in ligament, necessitating
withdrawal and re-direction toward midline.
Midline and paramedian approaches
If a paramedian approach is chosen, the Tuohy needle is inserted through the skin at a point about 1.5 cm
lateral to the mid point of the spinous process immediately below the level of the desired block. The needle is advanced perpendicular to the skin, through
the underlying fat and muscle, until it strikes the vertebral lamina. It is then withdrawn slightly,
redirected cephalad and medially, and walked off the lamina until it pierces the ligamentum flavum and
enters the epidural space. The dura mater is held against the posterior wall of the vertebral canal by the pressure of the CSF inside the dura. Regardless of approach, on cannulation of the
epidural space the dura mater is indented by the tip of the Tuohy needle.
Epidural needle engaged in midline ligament
Paramedian epidural technique
Caudal technique
For regional blockade of the caudal epidural space the patient is usually
positioned in a lateral or prone position. The caudal space is approached through the tough sacrococcygeal ligament that covers the sacral hiatus. It is identified as a midline indentation in the sacrum at a point forming the
apex of an equilateral triangle made with the posterior superior iliac spines. For the caudal epidural technique a 23 or 21 G needle is placed
over the sacrococcygeal membrane at an angle of about 60o to the coronal plane and perpendicular to the other planes, with the bevel facing anteriorly to allow it to pass along the anterior sacral wall without piercing
it. There is usually a loss of resistance as the membrane is pierced. The needle should then be lowered to an angle of about 20o and advanced a short distance. The dura is not approximated to the point of needle entry
into the epidural space (as it is at other spinal levels), but is always at least 34 mm away in adults. Therefore a needle up to 25 mm long can be used safely without risk of dural puncture. In children, the dural sac is closer
and the needle should be advanced only a short distance
Taylor Approach
The Taylor approach is a modified paramedian approach utilizing the large L5–S1 interspace. It is an excellent approach for hip surgery or for any lower
extremity surgery in trauma patients who cannot tolerate the sitting position.
This approach may provide the only available access to the epidural space patients with ossified ligaments.in
1. With the patient in the sitting or lateral position, a skin wheal is placed
1 cm medial and 1 cm caudad to the posterior superior iliac spine. 2. The epidural needle is inserted into this site in a medial and cephalad
direction at a 45° to 55° angle. 3. As in the classic paramedian approach, the first resistance felt before
entry to the epidural space is on entry into the ligamentum flavum. 4. If the needle contacts bone (usually the sacrum), the needle should be walked off the bone into the ligament and then into the epidural space in progressively more medial and cephalad directions.patients with ossified
ligaments.