As with any neuraxial blockade, the risks and benefits of epidural
placement need to be discussed with the patient. These should be explained
in a thorough but appropriate manner in order to provide informed consent.
The inability of the patient to speak English should not be a barrier to
providing epidural placement as long as there is a mechanism in place for
obtaining informed consent either through translation services in the
hospital or through telephone systems.
Patients (particularly older patients) occasionally have misconceptions
about epidural placement, such as:
- Permanent paralysis from the block
- Being awake during the operation
- Big needles puncturing the back while awake
- Epidural injection leads to back pain
These issues as well as any other concerns of the patient should be
discussed prior to premedication. The level of awareness during the epidural
placement and during the operation can be tailored to the patient's
desires. The patient, as well as the surgical staff need to understand that
the patient will have absent or reduced motor function after the block is
placed until the block resolves.
The patient's medical history and medications should be evaluated to
determine the presence of any condition that may increase the risks involved
with epidural placement (ie, clotting abnormalities, platelet count, recent
administration of anticoagulants).23 Drug therapy that may
influence the patient's physiologic response to epidural blockade should be
noted to prepare the clinician for altered or exaggerated responses to
dosing or test dosing (eg, beta-blockers, alpha-blockers). Medical
conditions that may become more severe with reducing afterload or preload
should be evaluated (eg, severe aortic stenosis, mitral stenosis,
hypertrophic cardiomyopathy, congenital conditions requiring stable systemic
vascular resistance such as ventricular septal defects). Other medical
conditions that may become more severe with motor blockade (eg, myasthenia
gravis, pulmonary fibrosis, severe chronic obstructive disease) require
careful review of the patient's history, prior medical evaluations and
testing, as well as a thorough physical examination. History of sensitivity
to local anesthetics, adverse drug reactions, or prior history of
complications related to epidural placement should be reviewed. Rather than
eliminate these patients from receiving epidural anesthesia, a well-planned
procedure with controlled initiation of the block can provide excellent
Physical examination should include an evaluation of the spine for evidence
of scoliosis, focal infection or pain, scars, severely limited range of
motion, or other findings that may make epidural placement more challenging
or impossible. Obesity, especially central obesity, may obscure physical
landmarks, making placement more difficult.
Baseline laboratory assessment of the patient's coagulation status and
platelet count should be obtained when the patient has a history of
coagulopathy or has recently received anticoagulants or any medications
known to influence platelet quality or function. This includes an
internationalized ration (INR) (or prothrombin time), activated partial
thromboplastin time (aPTT), platelet count, and bleeding time (only if there
is a specific concern). Many clinicians choose to obtain a hematocrit at the
same time, especially when appreciable blood loss is expected.
The final consideration before placing the epidural is to determine the goal
of the block. Epidural placement can be used for surgical anesthesia, as an
adjunct to general anesthesia, or for postoperative analgesia. The advantage
of epidural placement is the ability to provide segmental
blockade, meaning that the block can cover as many or as few
dermatomal levels as is clinically desired to meet the needs of the patient.
Once the decision has been made as to the purpose and levels to be blocked,
patient preparation can be initiated (Table 14–10).
Table 14-10. Segmental Level for Epidural Block for Various Surgeries ||Download (.pdf)
Table 14-10. Segmental Level for Epidural Block for Various Surgeries
|Function||Type of Surgery (example)||Suggested Levelof Entry|
|Surgical anesthesia||Hip surgery||L2-3 or L3-4 interspace|
|Lower extremity surgery|
|Adjunct to general anesthesia||Lower abdominal surgery||Catheter should be placed at the intervertebral space corresponding to the middle of the planned surgical incision|
|Upper abdominal surgery|
|Postoperative analgesia||Varied||Catheter should be placed at the midpoint of the surgical incision for thoracic or upper abdominal surgery, lumbar region for lower abdomen/LE surgery|
- Patient evaluation includes review of medications, medical conditions,
- Pay attention to drug therapy that may obscure physiologic effects of block.
- Provide information appropriate to patient's ability to understand.
- Clear up common misconceptions about epidural anesthesia.
- Be prepared for airway management at a minimum.
- Do a quick spine examination to prepare you to make adjustments for
potential problems with placement—scars, scoliosis, obesity-obscuring
The key to providing safe epidural anesthesia is proper
preparation. Intravenous access with a catheter large enough to administer fluids or
emergency drugs should be in place (ie, 18- to 20-gauge). Reversible
conditions such as severe hypovolemia should be managed prior to block
placement. However, routine fluid preloading of patients with
crystalloids has been questioned and may prove to be harmful in patients with
decreased serum colloid oncotic pressure (eg, those with burns, preeclamptic
patients, patients on tocolytic therapy).104,105 The type
of monitoring and resuscitative equipment available depends on the purpose
of the epidural block. Epidural blocks for analgesia, such as for labor or
postoperative analgesia, require blood pressure and pulse oximetry
ready access to vasopressors and positive pressure ventilation at a minimum. Drugs and equipment for life support, including airway management,
must be readily available if the block is to be performed for surgical
anesthesia or as an adjunct to general anesthesia (ASA Standard Monitors).
Controversies about placing the epidural block while the patient is
awake or asleep continue to be addressed in the literature. The advantages
to having the patient sedated or asleep are avoiding movement that could
lead to injury to the spinal cord or neural tissue and alleviating the
stress response associated with fear of pain or needles. The disadvantages
are similar in that the patient is unable to verbalize when neural
structures are encountered. For years, neuraxial blocks have been placed in
children with heavy sedation or under general anesthesia without a
preponderance of case reports on neural structure damage. Horlocker and
colleagues at the Mayo Clinic recently published a report of over 4000
patients undergoing lumbar epidural placement under general anesthesia
without any neurologic complications.106 Sedating the
patient with a benzodiazepam (eg, midazolam) and a narcotic (ie,
alfentanil/fentanyl) allows the clinician to safely place the epidural
catheter without undue stress to the patient. The choice of drugs for
sedation depends on the patient's overall medical condition and age. An
exception to the use of sedation is in the pregnant patient (potential of
harming the fetus).
- Adequate sedation is key to successful block placement.
- A combination of midazolam with fentanyl or alfentanil in a monitored
patient is effective in allowing proper positioning and placement of the
epidural catheter without undue stress to the patient.
Communication with the Surgical Staff
A discussion with the surgical staff to understand the operative
approach, the desired positioning of the patient, and an estimated length of
the surgical procedure is important for the anesthesiologist to determine
the best choice of anesthetic. The anesthesiologist can decide if a simple
epidural or a combined spinal-epidural with an initial more intense and faster onset motor
block is indicated. Postoperative analgesia can be determined at the same
time. Communicating with the nursing staff leads to better cooperation and
assistance with the epidural block. If feasible, turnover time can be
reduced by performing the block in the preoperative area or bringing the patient into the operating room and placing the
epidural block while the nursing staff is still setting up the surgical equipment. Cooperation with
the surgical staff improves when delays are not attributed to “anesthetic
Commercially prepared, sterile disposable epidural trays are available
and used by most institutions (Figure 14–11). All of the drugs
included in the tray are preservative-free. A standard kit typically includes the
- Drapes: Paper towel, fenestrated plastic drape, one paper drape
- Small tray with prep sponges, 4 × 4 gauze sponges, packet of
- Drugs: 10-mL ampule of 0.9% sodium chloride; 5-mL ampule of 1.5%
lidocaine with epinephrine 1:200,000; 5-ml ampule of 1% lidocaine; 1-mL
ampule of epinephrine 1:1000
- One filter straw
- Needles/Syringes: 25-gauge 1.5-in. needle, 18-gauge 1.5-in. needle, 18-gauge
3.5-in. Tuohy epidural needle with stylet, 3 mL/20 mL plastic syringes; 5-mL
glass Luer Lok syringe
20-gauge calibrated epidural catheter
Prepared epidural tray. 1. Solution of antiseptic, 2.
Syringe/needle for skin localization, 3. Epidural needle, 4. Glass syringe,
5. Epidural catheter, 6. Luer Lok attachment, 7. Glass filter, 8. Dosing
syringe, 9. Local anesthetic, 10. Saline.
A styletted Tuohy epidural needle is typically 16 to 18 gauge, 8–10 cm in
length, with surface markings at 1-cm intervals. It has a 15- to 30-degree
curve at the tip with a blunt bevel. The curved tip is designed to
prevent accidental dural puncture and to facilitate passage of the epidural
catheter (Figure 14–12). At the junction of the needle shaft and
hub are wings to allow better control as the needle is passed through
tissue. Longer needles up to 10 cm in length are available for obese
patients. A variety of needles are used for single-shot epidural blocks, but this
practice is less common in modern anesthesia because of the inability to
redose if the initial block wears off.
Common designs of epidural needles.
A: Hustead 17-gauge, B: Hustead 18-gauge, C: Crawford, D: Tuohy.
Epidural catheters made of a durable, flexible plastic are designed to
pass through the lumen of the Tuohy needle. They have either a single end
hole or a number of side holes at the distal end. The 20-gauge catheters are
calibrated for ease of determining the depth on insertion. The calibration
markings, openings, and the flexibility of the catheter depend on the
manufacturer. A more flexible catheter is designed to prevent forcing the
catheter into a space other than the epidural space, but it can be more
difficult to handle. The stiffer catheter is easier to pass, but can be
forced into spaces or structures other than the epidural space. Some catheters include a
reinforced, spring-loaded tip to prevent kinking. It is prudent for the
clinician to become familiar with all of the trays and catheters used by the
institution in the event that one particular tray is not available.
The only additional equipment needed for placement is a dressing for the
puncture site and tape to secure the catheter on the patient's back. Usually
a large clear dressing with silk or cloth adhesive tape is sufficient to
prevent catheter dislodgement and to keep the site clean. The tray should be
prepared while an assistant is positioning the patient or prior to
positioning out of sight of the patient to prevent increased anxiety
especially for needle-phobic patients. The prep solution should not
contaminate the epidural needles to prevent the rare possibility of chemical
- Completely preparing the tray out of the patients sight and before
positioning the patient reduces anxiety, saves time, and promotes efficient
placement of the epidural catheter.
The skin prep solution should be kept separate from the tray so as not to
contaminate the needles with prep solution.
Careful attention to the patient's position is essential to successful
placement of the epidural needle and catheter. Depending on the patient's
medical status, weight, and ability to cooperate, the sitting or lateral
decubitus position can be used. In general, it is technically easier to
identify the midline in an obese patient in the sitting position, but this
requires the assistance of a trained assistant to maintain the correct
posture. Improper positioning can turn an otherwise easy epidural placement
into a needlessly challenging one.
Monitoring equipment and oxygen can be attached to the patient before or
after the patient is positioned. The operating table should be at a
comfortable height for the clinician, blankets or covers should be available
for the patient's comfort and privacy, a stool for the patient's feet to
rest on (if sitting), and an assistant to support the patient in the correct
posture should be ready prior to beginning the block. Intravenous sedation
should be given to alleviate anxiety early in the preparation for the block.
It is our practice to provide the patient with 2 mg of midazolam and 100 mcg
of fentanyl IV for sedation purposes in most adult patients just prior to
Exceptions are pregnant mothers for labor and delivery or caesarian section.
Administer oxygen via a face mask at 6 L/min in all patients.
Likewise, pulse oximetry, and often, capnography are used during the
If the sitting position is chosen, the patient should be assisted to
sit on the table or bed with feet resting on a stool (or
touching the floor if very tall). The patient should lean forward with
elbows resting on a pillow or on the thighs. The back should be maximally
flexed to open up the lumbar vertebral spaces. Flexing the neck will help
the patient to flex the lower spine (Figure 14–13). The assistant
should help the patient to hold this position during the entire procedure.
Special positioning devices also are available to
maintain the position without assistants.
Patient in sitting position in preparation for
epidural placement. Note the outward back-curving leg flexion and feet
resting on the stool.
Lateral Decubitus Position
In the lateral decubitus position, the patient is placed on the side
with the back at the edge of the operating table that is closest to the
anesthesiologist. The spinous processes should be oriented parallel to the
floor to prevent rotation of the spine. The thighs should be flexed on the
abdomen with the knees drawn to the chest and the neck flexed so that the
chin rests on the chest. Asking the patient to “assume the fetal position”
or “touch your knees with your chin” may help with positioning during
lumbar epidural placement. An assistant should be available to
help with both positioning and maintenance of the proper position. Benefits
of the lateral decubitus position are that sedation can be more liberally
used, and that dependence on a well-trained assistant is not as important as
for the sitting position.32 Successful block placement
depends on keeping the spine parallel to the floor (Figure 14–14).
Obese patients or those with larger hips may require additional pillows to
maintain proper alignment of the spine.
Patient positioning in lateral decubitus position.
- Improper positioning can make simple epidural placement difficult.
- If a well-trained assistant is not available, the lateral position requires
less dependability on the assistant.
- For the obese patient, the midline sitting approach is easier as midline structures
are more easily estimated.
The level of insertion and dosing of the epidural needle or catheter
depends on the purpose of the epidural block. In pediatric cases, a
single-shot caudal block is sometimes used, but in most adult cases, a
catheter is placed so that either bolus dosing or a continuous infusion can
be instituted. Preparation of the epidural tray and medications to be
administered should be completed prior to positioning the patient. For
epidural anesthesia, the same monitors required for general anesthesia
should be applied. Oxygen by nasal cannula or mask should be in place prior
to sedation. For epidural analgesia, blood pressure and pulse oximetry
monitoring are the minimum requirements. There is a wide variation in
practice with regard to the extent of aseptic precautions prior to epidural
placement. Most clinicians agree that at a minimum, head covering, mask, and
sterile gloves should be in place.109–111
Four common approaches to the epidural space are possible: midline,
paramedian, Taylor (modified paramedian), and caudal. Each will be described
in the following paragraphs. Clinical expertise in each of these techniques
gives the anesthesiologist more flexibility when using an epidural block.
This approach is most commonly used for
epidural placement in the sitting position. After appropriate monitors are
attached and the patient is positioned, the lumbar spine is prepped and
draped in a sterile fashion (Figure 14–15A).
1. A fully prepared epidural tray should be placed to anesthesiologist's right for
right-handed, left for left-handed clinician.
2. Identify the vertebral level to be entered by surface landmarks (eg,
crest of iliac spines L4 to L5, entry level usually L2-3 or L3-4).
3. Infiltrate skin with local anesthetic using 25-gauge 1½-in.
needle at midpoint between two adjacent vertebrae to raise a large skin
wheel (Figure 14–15B).
4. Without removing needle, infiltrate deeper tissues to alleviate pain and
to assist with locating midline.
5. Insert epidural needle with stylet through same skin puncture. The dorsum
of the anesthesiologist's noninjecting hand rests on the patient's back with the thumb and
index finger holding the hub of the epidural needle (Bromage
6. Advance the needle through the supraspinous ligament and into the
interspinous ligament (approximately 2–3 cm depth) at which point the needle
should sit firmly in the midline (see Figure 14–15C).
7. After the ligaments are penetrated, it is no longer possible to change
the direction of the needle tip.113 Without withdrawing the needle to the skin level.
8. Remove the stylet and attach the glass syringe to the hub of the needle.
Lock it on firmly so that a false loss of resistance is not encountered
A: Lumbar epidural block
through the midline approach: Positioning and draping for midline approach. B: Lumbar epidural block
through the midline approach: Administration of local anesthesia to reduce pain during consequent epidural needle entry through the skin and
subcutaneous tissues. C: Lumbar epidural block through the midline approach: Tuohy needle lodged in the interspinous ligament. D: Lumbar epidural block through the midline approach: Tuohy needle with glass syringe attached for testing the loss of resistance to air. E: Lumbar epidural block through the midline approach: After the loss of resistance to air is documented, indicating the proper position of the needle in the epidural space, the catheter is threaded while observing depth marks.
As a review, there are three alternative techniques to identify the
epidural space: loss of resistance (LOR), hanging drop, and ultrasonography.
Dogliotti described the first, using LOR to fluid.12 This
technique is based on the different densities of tissues as one passes a
needle through the thickness of the ligamentum flavum into the epidural
The technique has been modified so that both fluid and air are
recognized as acceptable media for determining the LOR, with saline solution
and air being the two most frequently used. We will limit the discussion to
the advantages and disadvantages between saline and air for the loss of
resistance. Controversy has been growing controversy regarding the use of
air as the only medium to find the epidural space. First, air is
compressible, thus the feeling in the plunger of the syringe might result in
a false loss of resistance. Advocates of using air feel that it is easier to
verify if the needle went too far and pierced the dura, in which case the
practitioner could easily see cerebrospinal fluid (CSF) coming out. The use
of air has come under scrutiny lately, by several authors who question its safety.
Air has been found to be less reliable than a combination of air and
lidocaine to find the epidural space.114 However, some
argue that the use of air alone may cause pneumocephalus, which results in
severe headaches, and it can cause venous air
embolism.115,116 The use of the loss of resistance to air technique to identify the epidural space has also been associated with an
increased incidence of unblocked segments, and even persistent neurologic
deficits when air bubbles were expanded by the use of nitrous oxide, causing
either nerve root or, even worse, spinal cord compression.117–119 It has also been suggested that the incidence of intravascular
placement of epidural catheters is greater when air is used for LOR, but
other researchers have not confirmed these claims.114
Few negative reports can be found in the literature related to the use of a
fluid for LOR, one being the difficulty to verify if fluid obtained
after placement of a catheter is either saline or CSF. To differentiate
this, some practitioners check the contents of glucose and protein with a
urine reagent strip, and if positive the diagnosis of CSF can be
made.120 Moreover, if a large volume of saline is used for
LOR, this could produce an inadequate sensory block, probably due to
dilution of the injected local anesthetic and a delay in the onset of the
block supposedly due to the same reason.
Trainees learn different techniques from our preceptors during training. Under
optimal conditions, trainees should be exposed to all the different
techniques and then be able to choose the one they feel most comfortable
with and which has less chance of negative side effects based on their
experience and suggestions from the literature. Although the literature is
supportive of the use of a fluid or a combination of a fluid and a small
amount of air, there are limitations in the majority of studies that have
evaluated this issue, namely sample size, and with it, the possibility of
type I and type II errors. Thus, the best advice is to limit the volume of
injected fluid and air in the epidural space to less than 2–3 mL to avoid
the aforementioned problems.
Lastly, evidence in the literature is lacking concerning the best method to
identify the epidural space in children. Recently, the use of
ultrasound for the placement of epidural catheters in children has been
advocated. However, the technique is somewhat cumbersome and requires
significant expertise with ultrasound imaging as well as additional
personnel to hold the probe and operate the ultrasound equipment.
Nevertheless, with refinements in ultrasound technology, developments of
better imaging probes may aid in the correct placement of epidural catheters
in this population.
Loss of Resistance to Air
1. Continue to hold the needle at the hub with the noninjecting hand.
2. Using the thumb of the injecting hand, lightly tap the end of the plunger of the
needle while advancing the needle in a slightly cephalad direction.
3. Advance the needle slowly with controlled motion until the needle passes through the ligamentum
flavum. As the needle enters the ligamentum flavum, there is usually a
distinct sensation of increased resistance followed by a sudden loss of
resistance to pressure exerted on the plunger. Avoid injecting greater than
1 mL of air.
4. Once the loss of resistance occurs, do not advance the needle further without testing placement as there is an increased risk of
dural puncture. Experienced clinicians may elect to exert continuous
pressure on the epidural needle plunger while advancing the needle until
loss of resistance is noted. For the novice, the incidence of dural puncture
is higher with this technique because of a lack of familiarity with
Loss of Resistance to Saline with or Without Air Bubble
1. Instead of filling the glass syringe with 2 to 3 mL of air, the
syringe is filled with saline, or with saline and a small air bubble
2. The needle is advanced in the same fashion as with air. Continuous
pressure is exerted on the plunger of the needle. When using the combination
of air and saline, if the air bubble cannot be compressed without injecting
the saline, then the needle tip is probably not engaged in the ligamentum
flavum (Table 14–11).
3. Once a loss of resistance to air or saline has occurred, the glass
syringe is removed, and depth at which the epidural space was entered is
noted. The noninjecting hand should continue to hold the needle in place.
4. For single-injection epidurals, local
anesthetic can be injected through the needle.
5. For continuous epidurals, a small volume of sterile saline can be injected
into the epidural space to dilate the space.
6. Note the depth of the needle at the skin. The marking on the needle at
the skin is the depth from the skin to the epidural space.
7. Thread the catheter gently through the needle into the epidural space to
approximately the 15–17 cm mark, then remove the needle without dislodging
the catheter (Figure 14–15E).
8. Add the skin-to-epidural depth plus 3–5 cm. Withdraw the catheter to
that point and secure. No more than 5 cm of catheter should be left in the
epidural space to prevent displacement of the catheter laterally or into
Example: Needle entered epidural space at 7 cm, the catheter should be withdrawn
to 12-cm mark at the skin. This would allow 5 cm of the catheter in the
9. Gently flush the catheter with a small amount of saline to ensure
patency and aspirate to rule out intravascular (blood) or intrathecal (fluid) placement of the catheter.
10. A clear, occlusive dressing should be applied over the insertion site to
allow inspection of the catheter. The catheter should be secured to the
patient's back with the end at the shoulder for access in dosing. (See the
section Activating the Thoracic Epidural—Intraoperative Management for testing and dosing.)
Table 14‐11. Comparison of “Loss‐of-Resistance” Techniques ||Download (.pdf)
Table 14‐11. Comparison of “Loss‐of-Resistance” Techniques
|LOR to air||Theoretically, more obvious identification of epidural space by “feeling” LOR. Not dependent on visual sign||During shock wave lithotripsy, may cause tissue damage at air–tissue interface.|
|No timing with respiratory cycle required||Literature suggests several complications associated with its use|
|LOR to saline or hanging drip||Visual sign on entry into epidural space—not as dependent on “feel”||Plugged needle tip = low or no negative pressure|
|Difficult to time advancement with inspiration (epidural space negative pressure maximal)|
- Use the needle for skin infiltration to identify the midline structures (bone contact 1–2 cm from the skin-spinous process).
- In the lumbar area, insert the needle in a slightly cephalad direction.
- The needle will sit firmly in the midline once through the supraspinous
ligament. If it does not, the insertion is most likely off-midline.
- Once the needle passes through the ligaments, the direction of the tip
cannot be changed.
- The catheter should not be inserted >5 cm in the epidural space to
prevent displacement of the catheter into other structures.
It is essential for the anesthesiologist to become proficient with the
paramedian approach to epidural placement as there are situations when
it is the only technique feasible for epidural placement. This approach
offers a much larger opening into the epidural space than the midline
approach. Indications for this approach are:
- Patients who cannot be positioned easily or cannot flex the spine
(trauma/arthritic) when inserting the needle into the lumbar epidural space
- Calcified interspinous ligament
- Spine deformities: kyphoscoliosis, prior lumbar surgery
- Entry level at T3 to T7: In the midthoracic spine, the angulation of the
spinous processes is more oblique, the space between spinous processes is
narrower, and the ligaments are less dense. False loss of resistance is much
more common. Thus, the midline approach often proves difficult if not
1. The skin wheal is placed 1.5–2.0 cm lateral to the midline
opposite the center of the selected interspace in the lumbar and lower
thoracic levels (Figure 14–16A).
2. The epidural needle is advanced at that site perpendicular or slightly cephalad to the skin
until the lamina is encountered (Figure 14–16B).
3. The needle is redirected and advanced at a 10–20-degree angle toward
the midline and cephalad (Figure 14–16C).
4. If bone is encountered, the needle is “walked off” the bone into the
5. The supraspinous and interspinous ligaments are midline structures. The
paramedian approach is lateral to these ligaments. The epidural needle
penetrates paraspinous muscles with little resistance before entering the
6. The “feel” of the paramedian approach is completely different from that
of the midline approach because of the difference in tissues penetrated.
- Insert the needle 1.5–2.0 cm lateral to the midline of the center of
- Advance the needle perpendicular or slightly cephalad to the skin until bone is encountered.
- “Walk off” the bone, advancing the needle at a 10 to 25-degree angle
toward the midline and cephalad.
- The first resistance felt will be that of the ligamentum flavum.
Midthoracic Epidural Paramedian Approach
The T4-5 interspace is the injection site.
1. In the midthoracic level, the skin wheal is placed 1.5 to 2.0 cm lateral and
inferior to the superior spinous process (Figure 14–17A). A
22-gauge “spinal needle” can be used to infiltrate the skin to lamina.
Depth is noted to gauge the depth of epidural needle insertion.
2. Epidural needle is advanced perpendicularly and slightly cephalad through the skin at the same
location until the lamina is contacted.
3. The needle is withdrawn approximately 2 cm, redirected at a 15- to
20-degree angle toward the midline cephalad.
4. Each time bone is contacted, the needle is withdrawn 0.5 cm, then walked
off the bone in a medial/cephalad direction113 until the
ligamentum flavum is entered (Figure 14–17B).
A: Thoracic paramedian approach: Landmarks/initial needle insertion. Note the approximately 45-degree cephalad and medial needle angulation. B: Thoracic paramedian approach: Needle angle 55–60 degrees to the skin surface.
The Taylor approach113,121 is a modified paramedian
approach utilizing the large L5-S1 interspace. It is an excellent approach
for patients needing hip surgery or for trauma patients needing lower
extremity surgery who cannot tolerate the sitting position. Sometimes, it can provide the only available access to the epidural space in patients with ossified ligaments.
1. The skin wheal is placed 1 cm medial and 1 cm inferior to the
posterior superior iliac spine (Figure 14–18).
2. The epidural needle is inserted into this site in a medial and cephalad
direction at a 45- to 55-degree angle.
3. As in the classic paramedian approach, the first resistance felt is on
entry to the ligamentum flavum.
4. If the needle contacts bone (usually the sacrum), the needle should be
walked off the bone into the ligament, then into the epidural space using progressively more medial and cephalad redirections of the needle.
Taylor approach—landmarks: 1 = posterosuperior
iliac spine, 2 = iliac crest (corresponds approximately to the L3-4 level).
The caudal approach is commonly used in pediatrics for epidural
catheter placement for postoperative analgesia. In adults, it is usually
reserved for procedures requiring blockage of the sacral and lumbar nerves
(eg, inguinal herniorrhaphy, cystoscopy), epidurography, and for lysis of
adhesions in patients with low back pain with radiculopathy after spinal
surgery.122 Considering that the sacral hiatus is ossified
in some patients, the use of fluoroscopy guidance is useful to decrease
the incidence of needle and catheter malposition.
The sacrum is a triangular-shaped bone formed by the fusion of the five
sacral vertebral. Nonfusion of the fifth sacral vertebral arch creates the
structure known as the sacral hiatus. The hiatus is covered by the
sacrococcygeal ligament (an extension of the ligamentum flavum). On its
borders are the bony prominences known as the sacral cornu. The sacral
hiatus is the point of access to the sacral epidural space. It is usually
identified as a groove above the coccyx (Figure 14–19). If
fluoroscopy is not used, there are two methods for identifying the hiatus:
(1) Locate the posterior superior iliac spines. A line drawn between them
becomes one side of a equilateral triangle. At the apex of the triangle is
the sacral hiatus. (2) With firm pressure, identify the coccyx with the index
finger. As the finger moves cephalad, the first pair of bony protuberances
are the cornu, which surrounds the hiatus.
1. Prep and drape the skin in sterile fashion.
2. Patient is placed in a lateral or prone position (pillow under pelvis if prone).
3. Either a smaller gauge IV catheter (18- to 23-gauge) or a 20-gauge
epidural needle is advanced at a 45-degree angle from the back with the
bevel up (to avoid penetrating the anterior sacral wall).
4. A distinct “pop” or “snap” is felt when the needle pierces the
5. The needle angle is lowered to 160 degrees (almost flat) toward the back.
It is advanced not more than 1.5 cm (usually between 5 and 7 mm) in adults
and not more than 0.5 cm in children.
6. Aspirate for blood or CSF before injecting local anesthetic.
7. The epidural catheter can then be inserted through the needle to the
A: Caudal approach: Angle
of needle insertion required to enter the caudal canal.
Implementing the Lumbar Epidural Block—Intraoperative Management
The volume and concentration of local anesthetic needed for epidural
anesthesia is larger than that required for spinal anesthesia, therefore the
catheter should be tested for evidence of proper placement in the epidural
space. The purpose of the “test dose” is to make sure that the catheter is
not in the subarachnoid, intravascular, or subdural space.
Although the validity of a test dose of local anesthetic with
epinephrine in obstetrics and pediatrics has been
questioned,123,124 it is still suggested by many to
decrease the risk of an intravascular injection.125,126
The “classic” test dose combines 3 mL of 1.5% lidocaine with 15 mcg of
epinephrine. The intrathecal injection of 45 mg of lidocaine will produce a
significant motor block consistent with spinal anesthesia. A change in heart
rate of 20% or greater is an indication of intravascular injection
warranting the removal and replacement of the catheter. If the heart rate
does not increase by 20% or greater, or if a significant motor block does
not develop within 5 min of administering the test dose, it is considered
negative. Exceptions to this rule have been observed in patients under
general anesthesia with isoflurane, patients receiving β-adrenergic
blocking agents with heart rates below 60 bpm, and obstetric patients in
In children and in obstetric patients, other methods of identifying
intravascular placement of the epidural catheter have been advocated.
Because children are anesthetized prior to epidural placement, interference
with response to epinephrine under volatile general anesthetics creates a
high percentage of false-negative test doses.127 In the
obstetric patient, if the test dose is injected during a contraction, the
change in heart rate may be related to pain and not to the epinephrine. In
this population, the test dose should be administered during uterine
diastole, soon after a uterine contraction.128 Changes in
the P or T wave on the electrocardiogram in pediatrics or the use of nerve
stimulators to confirm epidural placement in pregnant patients have been
In patients on β-adrenergic blocking agents, heart rate changes may
not be evident. Systolic blood pressure increases of greater than 20 mm Hg
have been used as an indicator of intravascular
- A change of 20% or greater in heart rate after the test dose
indicates a probable intravascular injection—replace the catheter.
- A dense motor block within 5 min of a test dose should prompt a suspicion of
a spinal block—monitor vital signs and block level repeatedly. Either
convert to a continuous spinal anesthesia or replace the catheter.
- Peaked P waves or changes in the T wave in children indicate a vascular
- Give the test dose to a pregnant patient after a contraction is over for a
more accurate response to test dosing.
- A change in systolic blood pressure of >20 mm Hg in patients on
beta-blocking agents is more indicative of an intravascular injection.
After the epidural catheter has been aspirated to check for blood or
CSF, and a negative test dose has been demonstrated, the catheter should be
dosed to provide the level of surgical anesthesia desired. The maintenance
of the desired level of anesthesia can be accomplished through intermittent
or continuous dosing after the initial loading dose provides the level of
anesthesia necessary for the surgical procedure.
As a general guideline, 1–2 mL per segment to be blocked in a lumbar
epidural, 0.7 mL per segment for a thoracic epidural, and 3 mL per segment
to be blocked for a sacral/caudal epidural is used as an initial loading
dose. The loading dose is given in 5-mL aliquots through the catheter, repeated at 3- to 5-min
intervals, giving the clinician time to assess the patient's response to
dosing. If at any time the patient demonstrates an exaggerated response,
further incremental doses should be withheld and the patient reassessed. The
catheter should be removed and replaced if the following occurs: a large
volume of local anesthetic is required to initiate the block or an
incomplete, unilateral, or inadequate block results. Wasting time
administering further doses of medication, repositioning the catheter, or
other time-consuming measures leads to frustration for the patient, the
surgical staff, and delays in the operative procedure. Moreover, these
maneuvers rarely result in a successful block.
After the initial dose, one quarter to one third of the amount can be
administered 10–15 min later to intensify the sensory block. The overall
level of the block will not be significantly increased with this
The level and duration of epidural anesthesia depends primarily on the
injection site, and the volume and concentration of the drug. Other factors
such as age, pregnancy, and sex are less important factors but need to be
considered. The addition of fresh epinephrine and 8.4% sodium bicarbonate
to lidocaine, mepivacaine, and chloroprocaine will decrease the latency,
improve the quality, and prolong the duration of the block. Epinephrine is
less effective with the long-acting local anesthetics. Adding bicarbonate to
ropivicaine and in a dose greater than 0.05 mL/10 mL of bupivacaine will
cause precipitation. The addition of opioids (eg, fentanyl) has been shown
to improve the quality of the block without any effect on
Repeat doses, commonly referred to as “top-ups,” need to be given
before the level of the block has receded by more than two dermatomes. One half to
two thirds of the original volume of local anesthetic should be given for
each repeat dose. The anesthesiologist must have a working knowledge of the
characteristics of the local anesthetic used to properly implement the
redosing protocol so that the sedated patient does not have to be disturbed
to check dermatomal levels for sensory block (Table 14–12).
Table 14-12. Time to Two Dermatome Regression—Commonly Used Local Anesthetics
A continuous infusion through the lumbar epidural catheter can be
started after the initial bolus to maintain surgical anesthesia.
Continuous infusions require the same diligent
attention to the patient as any other anesthetic.134 The
usual infusion rate is between 4 and 15 mL/h. The wide range is usually
dependent on the age, weight, and extension of the block desired in a
particular patient. Thus, individualization is necessary, and a fixed
rule cannot be applied for this purpose.
|Dosing Regime: Lumbar Epidural|
- The loading dose for epidural anesthesia is between 10 and 20 mL,
given in increments of 5 mL. Wait 3–5 min between each increment to check
- If the block is incomplete, replace the catheter rather than waste time
trying to reposition it or give a larger dose of local anesthetic.
- Inject one quarter to one third the initial dose 15 min after initial bolus to
enhance the sensory block.
- Epinephrine and bicarbonate will speed up the onset and enhance the quality
and duration of the block. Fentanyl will improve the quality of the block.
- Give the “top-up” dose before two-segment regression has occurred to
maintain adequate anesthesia.
- A continuous infusion is an alternative to bolus dosing; it has the
advantage of hemodynamic stability and can be continued postoperatively for
Activating the Thoracic Epidural—Intraoperative Management
Epidural anesthesia is ideally suited for thoracic surgery. It is
considered the gold standard for postthoracotomy analgesia because it
produces better pain relief with fewer side effects than other commonly used
methods.135 When combined with general anesthesia, it
prevents vagal reflexes and pain from traction on the
Placement and activation are similar to lumbar epidural placement, with
a few modifications. An epidural block provides the most intense block at
the insertion site, so the tip of the catheter should be placed at
midincision level, usually above T8. This will provide the best segmental
analgesia. Because there is a greater incidence of false loss of resistance
in the midline thoracic approach, the paramedian approach is the best
technique to use for catheter placement.
The sharp angulation of the spinous processes especially in the midthoracic
area can make the midline approach challenging even for the experienced
1. Once the catheter is placed, it is aspirated for the presence of
blood or CSF.
2. A test dose of 3 mL of 1.5% lidocaine with epinephrine 1:200,000 is
given to (a) rule out intravascular catheter position and (b) provide a band
of anesthesia before inducing general anesthesia.
3. If no anesthesia can be appreciated, the catheter should be replaced.
4. The patient should receive only light sedation for placement to alert the
clinician to the development of paresthesias.
Dosing the Thoracic Epidural Catheter
Several dosing regimes have been suggested. All are effective means of
providing surgical analgesia, allowing a “light general anesthesia” to be
used and thereby reducing residual respiratory depressant effects.
After a negative aspiration and test dose.
1. An initial dose of 3 to 6 mL of dilute bupivacaine 0.125% to 0.25% or 0.1% to 0.2% ropivacaine with or without preservative-free morphine (1–2 mg) is
administered, followed by 3 mL of 0.25% to 0.5% bupivacaine every 30 min.137
2. Alternative regimen: Administer a loading dose with 3 to 6 mL of bupivacaine (0.125%)
or ropivacaine (0.1%–0.2%)
with an opioid (fentanyl 2 mcg/mL or hydromorphone 20 mcg/mL) at least 30
min as tolerated before the end of the case. Start an infusion of
bupivacaine 0.0625% or 0.1% ropivacaine with fentanyl or hydromorphone at 3 to 5 mL/h before
the patient leaves the operating room.138
- The paramedian approach is easier especially in the midthoracic
- Expect more frequent false loss of resistance, especially if the midline
approach is used.
- Lighter but adequate sedation should be given for placement because of the
greater risk of injury to neural tissue.
- The test dose not only identifies intravascular injection, but also serves
as a means of identifying placement as a band of anesthesia should develop
in the segment where the local anesthetic was injected.
- Because of the proximity to cardiac accelerator fibers, smaller bolus doses
of local anesthetic should be used and response checked carefully before
redosing to prevent large drops in heart rate or blood pressure.
- Remember that hypotension can occur in nearly all patients with a high
thoracic epidural blockade. In fact, it has been said that if there is no
hypotension after an initial bolus in the high thoracic epidural space, it
is likely that the epidural catheter is not in the epidural space.
Intraoperative sedation can be provided to the level of the patient's
comfort especially when the epidural is used as the primary anesthetic. If
the patient prefers to be kept aware, then light sedation with an initial
dose of a benzodiazepam and opioid on insertion can be effective. For those
who prefer to be “asleep,” a propofol infusion can be added to maintain
sedation without respiratory impairment.
- Appropriate sedation is the key to successful epidural placement and
- A great epidural anesthesia with poor sedation leads to an unpleasant operative
Problems with Epidural Placement
Epidural placement produces unique problems that are directly related
to experience, body habitus of the patient, or disease states affecting the
spine. Most of these problems can be overcome if the clinician recognizes
the problem and knows how to make adjustments in technique (Table 14–13).
Table 14-13. Problem Solving: Epidural Placement ||Download (.pdf)
Table 14-13. Problem Solving: Epidural Placement
|Problem||Interpretation||Reason for Problem||Action|
|Needle floppy, angles laterally||Missed supraspinous ligament||Entry off midline||Reassess midline spinous processes, redirect needle|
|Contact hit bone at <2 cm||Contacted hit spinous process||Missed interspace; spine flexion inadequate||Identify interspace; needle entry should be more caudad|
|Contact hit bone 4 cm or >||Contacted hit lamina||Needle entry too lateral||Redirect needle to midline or use paramedian approach|
|Bony resistance in all midline approaches||Arthritic spine and ligaments||Ossification of ligaments||Use paramedian approach|
|Can't thread catheter||Narrow epidural space Missed epidural space, false loss of resistance|
1. Space not dilated
2. Epidural needle too close to dura
3. Catheter not in epidural space
1. Dilate space with 20 mL sterile saline
2. Try rotating needle slightly to change direction of bevel
3. Reassess loss of resistance with glass syringe, advance needle into epidural space
|Blood in catheter||Penetrated epidural vein||Possible too lateral entry (Hogan: epidural veins are scattered in the epidural space, not just laterally as commonly
taught); engorged epidural veins||Withdraw 1–2 cm; flush with saline. Aspirate again—if still bloody—replace. If clear, use catheter cautiously with frequent aspirations; small incremental doses|
|Resistance to LA injection, difficulty passing catheter, clear fluid in catheter, cold||Drip back of LA||Fluid cold = LA; May be in subdural space||Will get widespread patchy block w/hemodynamic instability—replace catheter|
|Catheter passes easily, clear fluid in catheter, warm||Subarachnoid placement||Warm fluid/+ BS = CSF; catheter in subarachnoid space; missed epidural space/pierced dura||Two options: |
1. Continuous spinal
2. Remove/replace at another interspace
|Pain, paresthesia w/ catheter insertion||Catheter near nerve root||Too lateral an approach; too much catheter left in epidural space||If pain persists, replace catheter. Don't leave >5 cm in space, withdraw catheter if >5 cm|
|Can't palpate spinous processes||Adipose tissue or arthritic changes obscuring spinous processes||Obesity; severe arthritis|
1. Try midline approach for obese
2. Use 5 cm, 22-gauge needle to find bony landmarks
3. If no luck with midline, try paramedian
|Can't flex spine||Arthritis||Ossification of bony processes and ligaments||Try paramedian approach|
|Scapular “winging” Bone contact in multiple planes||Scoliosis||Lateral curvature of the spine, more commonly in thoracic region, females||Paramedian approach with visualization of curvature to direct needle entry|
Problems with Epidural Function
An easily placed epidural catheter does not guarantee excellent function.
Inadequate blocks, partial blocks, and unilateral blocks are some of the
problems that can occur. Hypotension, often seen with epidural dosing, is a
relatively common side effect that is easily managed if the clinician is
prepared. Because of the discontinuous nature of the epidural space and
variations in anatomy, sometimes these problems cannot be overcome. In the
vast majority, careful evaluation of catheter placement, the dose and type
of medication given, or administration of sedation can resolve these
A decrease in blood pressure is common and expected with epidural
anesthesia secondarily to the sympathectomy caused by local anesthetic
action. The blood pressure should be maintained to within 20% of the
patient's resting baseline.
Bolus the patient with 500 to 1000 mL of a balanced salt
- If necessary, small doses of ephedrine (10–20 mg) can be used in the
pregnant or bradycardic patient after fluid bolus if the patient is still
- Phenylephrine (40–120 mcg) can be used to
constrict peripheral blood vessels, thereby increasing venous return and
After an epidural has been adequately dosed, the patient may complain
that one side is densely blocked, but pain and motor function is still
intact on the opposite side. Because of the segmental and possibly septated
nature of the epidural space, unilateral blocks can occur. The more common
explanation for a unilateral block is incorrect catheter placement. If the
catheter has been inserted >5 cm into the epidural space, the tip
of the catheter may have entered the intervertebral foramen, exited the
epidural space, or wrapped around a spinal nerve. The resultant block will
be inadequate or unilateral
Pull the catheter back 1–2 cm, leaving 3–4 cm in the
- Turn the patient with the unblocked side down and redose the catheter
with 3 to 5 mL of local anesthetic.
- If no effect, replace the catheter.
Inadequate Block: Breakthrough Pain Despite Adequate Block Height
This problem can be seen secondarily to inadequate sacral blockade. The
sacral segment is larger, dense, and difficult to block.
Raise the head of the bed and redose the catheter with a
higher concentration of local anesthetic.
- Administration of 50 mcg of fentanyl to improve the quality of the
Questionable Quality of Epidural Catheter Placed for Analgesia, Fully Dosed. Patient Has to Go to Surgery
This problem is often seen in obstetrics. An epidural is placed and
dosed, but the patient is not fully comfortable. More local anesthetic is
given with fair control of pain. Subsequently, the patient has to go urgently to the
operating room for a cesarean section requiring dense block to a T4 level.
The easiest way to prevent this problem is to replace a questionable
Take the patient to the operating room, remove the
- Do a combined spinal-epidural (CSE) using a lower spinal dose.
- Use the new epidural catheter to raise the level of the block if necessary.
- Use general anesthesia if time does not permit placing the CSE.
Block Is Dissipating Requiring Larger Doses of Local Anesthetic
This problem occurs for two potential reasons. If the epidural has been
used for analgesia and has been dosed frequently, tachyphylaxis to the local
anesthetic can occur. The other problem is catheter migration into a vessel.
Check catheter to ensure it has not migrated into a blood
vessel. If so, pull it back 1–2 cm, flush with saline. If no blood is
aspirated, cautiously rebolus with incremental doses, being vigilant for
systemic toxic signs.
- If blood is still in the catheter, replace.
- If the catheter has not migrated, rebolus the catheter with a higher
concentration of local anesthetic and increase the infusion rate (if
continuous). Add an opioid to enhance the quality of the block.