epidural 3/18

Question 1

what structures do you pass thru while doing an epidural (starting with skin…)?

Answer 1

skin→subQ→supraspinous lig.→interspinous lig→ligamentum

flavum→epidural space

Question 2

1. where does the epidural space (and dura mater) extend?
2. what type of pressure is in the space?
3. where is the epidural space widest?
4. where is the epidural space most narrow?

Answer 2

1. Extends from the skull to the sacral hiatus
2. usually has negative pressure
3. widest at L2 (5-6 mm)
4. narrowest at C5 (1-1.5 mm)

Question 3

what is contained in the epidural space (6 things)?

Answer 3

1. Spinal Cord with dural and arachnoid sac
2. Nerve Roots
3. Adipose Tissue
4. Connective tissue
5. Lymphatic vessles
6. Blood Vessels
   a) Small arteries and veins (together these form a plexus)
   b) Can be enlarged, making placement of catheter more difficult

Question 4

what structures surround the epidural space:

1. dorsal (posterior) side?
2. ventral (anterior) side
3. bi-laterally?
4. rostral
5. caudal

Answer 4

1. Dorsal/posterior- Ligamentum Flavum
2. Ventral/anterior - posterior longitudinal ligament and pedicles
3. Lateral- pedicle of vertebrae and
   intervertebral foramina
4. Rostral- Foramen Magnum
5. Caudal- Sacral Hiatus

Question 5

1. what do local anesthetics do when they come in contact with nerves?
2. what channels do they work on (& in what state)and what do they do?

Answer 5

1. ”Local anesthetic solution injected blocks conduction of impulses along all nerves (motor, sensory and autonomic) with which it comes in contact.”
2. ”local anesthetics bind to sodium channels, primarily in the inactivated state, preventing further channel activation. Sodium ion movement into the cell is prevented, effectively blocking the development of the action potential. “

Question 6

why is the exact site of action of an epidural is not known?

Answer 6

Because LA in the epidural space must diffuse. The possible sites of action are:

Question 7

Spinal vs. Epidural: how do we decide?

Answer 7

Determine: area to be blocked and duration needed for pain control

Question 8

comparison between epidural and spinal?

1. epidural:
2. SAB (spinal):

Answer 8

1. epidural:
pros:
	-less hypotension
	-can "top off" or re-dose block during surgery
	-can be used post op for pain control
cons:
	-higher risk of post dural puncture headache (PDPH)
2. SAB
pros:
	-takes less time to perform
	-rapid onset
	-better quality sensory and motor block
	-denser block
cons:
	-shorter duration

Question 9

Indications for an Epidural: similar to a SAB, but different too!

1. which uses of an epidural are the same as a spinal?
2. what 2 aspects are different?
3. how do different stages of labor dictate different areas of pain and what kind of spinal analgesia to use?

Answer 9

1. uses that are the same:
surgical anesthesia:
	-abdomen surgery
	-pelvic and perineum surgery
	-lower extremities
	-thoracic
-labor and delivery (c-section or labor pain mgmt).
-cancer pain
-trauma
-sciatica
2. different:
	-chronic pain vs acute uses
	-location along spine (cant do spinal above L2)
	-
3. 	blockage of T10-L1 dermatomes is for first stage of labor (pain is more abdominal)
	blockage of S2-S4  dermatomes is for second stage (pain is more vaginal and perineal)

Question 10

what concentrations of each would be used for an epidural? what is onset and duration?

1. 2-chloroprocaine:
2. lidocaine:
3. mepivicaine:
4. bupivicaine:
5. etidocaine:
6. ropivacaine:
7. levobupivacaine:

Answer 10

1. 2-chloroprocaine: 3%; 10-15 min onset; 45-60 min without epi; 60-90 min with epi.
2. lidocaine: 2%; 10-15 min onset; 80-120 min without epi; 1020-180 min with epi
3. mepivicaine: 1-2%; 15 min onset; 60-160 min without epi; 160-200 min with epi
4. bupivicaine; 0.25-0.50%; 15-20 min onset; 160-220 min without epi; 180+ min with epi
5. etidocaine: 1%; 15-20 min onset; 120-200 min without epi; 150+ with epi
6. ropivacaine: 0.5-0.75%; 15-20 min onset; 140-180 min without epi; 150+ min with epi
7. levobupivacaine: 0.5%; 15-20 min onset; 160-220 min duration without epi; 180+ with epi

Question 11

1. what kind of compartment is the epidural space and where is it?
2. What are the structures around epidural space?
   
   • dorsal
   • ventral
   • lateral
   • rostral
   • caudal

Answer 11

1. Consider it a “closed compartment.” The space between the dura and the ligaments of the vertebrae that “close” it in.
2. structures around epidural space:
   = Dorsal/posterior- Ligamentum Flavum
   = Ventral/anterior - posterior longitudinal ligament, pedicles
   = Lateral- pedicle of vertebrae and intervertebral foramina
   = Rostral- Foramen Magnum
   = Caudal- Sacral Hiatus

Question 12

epidura blood patch:

1. how is it done?
2. what is it for?

Answer 12

1. blood is drawn and injected into the epidural space

2. to repair dural tears

Question 13

Contraindications: epidural and SAB

• absolute-
• what are lab values that preclude you from epidural of SAB?
• how long should you be off your sq or oral antithrobics?
• relative-

Answer 13

Absolute
– Infection at placement site
– Hypovolemic shock
– Hemostatic alteration
	o Note: Epidural blocks can be placed 2 h after the last dose of subcutaneous heparin, 12 h after the last dose of LMWH.
	o INR must be 100,000
	o Plavix dc’d x 7 days, Ticlid dc’d x 14 days
– Patient refusal
– Lack of appropriate monitoring tools

Question 14

what is 2 dermatome regression?

Answer 14

two dermatome regression – a term used to describe the duration of epidural anesthetics. The amount of time it takes for a block to recede by two dermatomes from the block’s maximum extent.

Question 15

what is complete rosolution?

Answer 15

Complete resolution – the time it takes for the pt to recover completely from the sensory block. When the block has completely resolved, the pt is ready for discharge.

Question 16

1. what type of LA should be used (as far as pharmacutical preparation
2. how should they be chosen?

Answer 16

1. Only preservative free LAs should be used.

2. Chosen by their duration of action

Question 17

what is the short acting LA? what is the dose (%) onset and duration?

Answer 17

• Chloroprocaine 2 or 3%
o Fastest onset, shortest duration
o 45 – 60 minute duration for single dose

Question 18

what is the intermediate?

1. a) what drug and percent?
   b) what is duration
   c) what can happen from repeated doses?
2. drug & percent

Answer 18

1•a) Lidocaine 1.5 or 2%
	o 60 – 90 minute duration for single dose
	o Tachyphylaxis (decreased duration with repeated injections) can occur with repeated dosages
2• Mepivicaine 1 or 1.5%

Question 19

what are the long acting

1. a) drug and percent
   b) what type of block?
   c) risks with this LA?
2. a) drug and percent
   b) what is potency in comparison to drug 1?
   c) what is missing that is present with drug 1?

Answer 19

Long Acting
• Bupivicaine 0.5 or .75%
o 120 – 140 minute duration
o Denser sensory block than motor block, good for analgesia
o Risk of cardiovascular toxicity
• Ropivicaine 0.5-0.75%
o 40% less potent than bupivicaine but less cardiotoxic
o No “motor sparing” like bupivaine, otherwise similar profile

Question 20

Opioids:

1. what is their function in an epidural?
2. what are their side effects:

Answer 20

1. Increase the duration of the sensory block, but not the motor block
2. Can cause:

Question 21

Fentanyl in epidural or spinal:

1. hydrophobic or hydrophillic; what is result on duration?
2. duration:
3. blous:
4. how much is added to epidural solution (per mL)?

Answer 21

1. Fentanyl – hydrophobic, therefore shorter duration
2. Duration 2-6 hours
3. Bolus dose = 50 – 100 mcg
4. Can be added to continuous epidural solution, 1-2mcg/ml

Question 22

Morphine:

1. what type of morphine must it be? what is it called?
2. is it hydorphobic or hydrophillic? how does that change duration?
3. what is duration?
4. what is bolus dose?
5. what is the big risk with this medicine?

Answer 22

Morphine
1. (duramorph is preservative free MS)
2. hydrophilic so longer duration
3. Duration 12 – 24 hours
4. Bolus dose = 2-5 mg
5. Caution should be exercised when morphine is administered epidurally (spinally, too), as it is associated with delayed biphasic respiratory depression.
o Early depression from systemic venous absorption.
o Late depression from CSF absorption and spread to
the medullary ventilation centers brain.

Question 23

1. Clonidine:
   
   • what is the dose; what does it do?
2. Epinephrine
   
   • dose; what does it do?
   • what does low dose cause (that you dont want)?
3. Bicarbonate
   
   • dose; what is the action

Answer 23

1. Clonidine
   
   • 150 – 300 mcg prolongs the sensory but NOT the motor block
2. Epinephrine
   
   • 5 mcg/ml (1:200,000 mg/mL) prolongs duration of sensory and motor blocks for short and intermediate acting LAs
   • (Epi added in low concentrations can cause more of a decrease in MAP due to the Beta 2 vasodilation)
3. Bicarbonate
   
   • 0.1 mEq/ml speeds the onset

Question 24

1. what determines density of block?

2. what determines how high the block goes?

Answer 24

1. the concentration

2. the volume the LA is in.

Question 25

Lumbar epidural advantages? disadvantages: example: how much LA would a T10 block require from L3-4 space?

Answer 25

1. Lumbar epidural is most common because it’s easy and the needle is inserted below the termination of the cord. Disadvantage: high volumes must be given to reach mid thoracic nerves -at 2 ml/ segment= 9–18 mL of local anesthetic.

Question 26

what are aspects to thoracic epidural? 1. spinous process angle (less or more than lumbar)? 2. deeper or more shallow? what are other factors that may affect thoracic epidurals?

Answer 26

o Thoracic epidural space:

Question 27

what other factors affect epidural onset?

Answer 27

• other factors (controversial): height, weight, age, pt position during injection, pregnancy, speed or mode of injection

Question 28

where to place the epidural based on surgey: 1. Lower abdominal procedures or labor - 2. Upper abdominal procedures – 3. Thoracic procedures – 4. Upper arm, shoulders, chest or chronic pain –

Answer 28

1. Lower abdominal procedures or labor - insert at L2 – L3 2. Upper abdominal procedures – insert at T8-T10 3. Thoracic procedures – insert at T4-T5 4. Upper arm, shoulders, chest or chronic pain – C7 – T1

Question 29

how do you decide how many mL of LA to bolus in the epidural? - how many mL per segment at lumbar level? - how many mL per segment at cervial and thoracic?

Answer 29

The guideline for dosing an epidural in adults is: - 1–2 mL per segment to be blocked at the lumbar level, - 0.7 – 1 mL per segment for the cervical and thoracic levels

Question 30

``` Initial dose based on location: 1. thoracic: how is it adjusted in short patients: tall patients: 2. Lumbar: T10: T4: ```

Answer 30

``` 1. Thoracic 6-8 ml(Short pts, reduce by 1-2 ml; Tall pts, increase by 1-6 ml) 2. Lumbar T10 = 10-12 ml; T4 = 20 – 25 ml 3. 1/3 to 1/2 the intitial dose ```

Question 31

Always administer a test dose prior to injecting the intended LA!!!! 1. what is in a test dose? 2. what is seen if the epidural has gone subarachnoid? 3. what if the epidural has gone intravascular? - what if the patient is beta blocked? - what other signs may be seen?

Answer 31

1. 3 ml of 1.5% lidocaine with 1:200,000 epinephrine 2. If subarachnoid: spinal anesthesia within 3 minutes, rapid ↓ in HR and BP 3. If in a blood vessel (intravascular) : 20% increase in HR and SBP within 30 seconds. - A change in systolic blood pressure of > 20 mm Hg in patients on beta-blocking agents is more indicative of an intravascular injection. - may also see signs of LA toxicity

Question 32

what are signs of LA toxicity?

Answer 32

1. circumoral numbness (mouth and tongue) 2. metalic taste 3. tinnitus 4. lightheaded, slurred speech, visual disturbances. muscle twitching, vertigo 5. seizures 6. cns depression/coma 7. resp arrest 8. cardiovascular collapse

Question 33

cook book for epidurals:

Answer 33

- 125% bupivicaine (1/8th%) + 2mcg/ml fentanyl, run at 7-10ml/hour Mix 25 ml .25% bupivicaine 25 ml .9NS Throw out 2 ml, then add 2 ml of fentanyl -.0625% bupivicaine (1/16th%) + 3mcg/ml fentenayl, run at 7-12 ml/hour Mix 13 ml .25% bupivicaine 28 ml .9NS 2 ml fentanyl -.065% bupivicaine + 2 mcg/ml fentanyl Mix 13 ml .25% bupivicaine 2cc fentanyl 35 ml .9NS -2% Lidocaine infusion (with or without epi) No need to dilute this. Just mix 2% lidocaine (48 ml) with 2 ml fentanyl and run at 7-10 ml/hour

Question 34

1. goal of spinal/epidural anesthesia? 2. blockade order... 3. where is sympathetic blockade in proximity to sensory? - what are the sympathetic side effects? - how do effects compare with SAB? - when will you see bradycardia? 4. what is the treatment for epidural symptoms?

Answer 34

1• Sensory Anesthesia (remember, this is our goal) 2• Sympathetic→Sensory→Motor 3• Sympathetic - 2 above sensory -Decreased SVR due to arterial and venous dilation. -Hypotension is less than a SAB. -Bradycardia. Usually only if level is T5 or higher, remember, cardiac accelerators are T1-4 4.Tx: same as SAB

Question 35

1. where is the motor block in proximity to sensory block? | 2. what is the LA used that spares motor block

Answer 35

1. motor is 2 below sensory (ex: if sensory is at L3 for a knee, motor is L5 (so patient may have ankle/calf weakness) 2. bupivicaine spares motor weakness especially at lower doses

Question 36

Expected “complications.” Commonly seen, depending on the level of the block and density: 1. cardiac: - tx: 2. respiratory: what are factors? - tx: 3. GI: what happens? what are side effects? - tx: 4. renal:

Answer 36

Complications • cardiac: Hypotension -tx: fluids, vasoactive drugs • resp: Respiratory depression -Depends on the height of the block or can be due to narcotic -If due to the height, talk to the patient and assist with respirations until the block recedes. -If due to narcotics, Give narcotic antagonists. • Gastrointestinal -the result of blockage of the sympathetic splanchnic fibers from the T5 through L1 level ends with unopposed vagal dominance -leads to an increase in secretions; peristalsis; and a small, contracted gut. -Nausea is a common problem (20%) following neuraxial anesthesia. Due to increased gastric peristalsis secondary to unopposed vagal activity. -- tx: prevent by promptly treating hypotension with a fluid bolus, ephedrine, or phenylephrine. • Renal/Genitourinary -Since renal blood flow is maintained through autoregulation, an epidural has very little effect on renal function.

Question 37

what are other side effects of epidural:

Answer 37

- back ache - PDPH - subdural injection - hematoma - epidural abcess - neurologic injury - pruritis d/t narcotic - n/v d/t narcotic - urinary retention - inadequate pain relief

Question 38

caudal epidural:

Answer 38

Common in pediatrics for epidural catheter placement or single injection for postoperative analgesia. Also used in adults for procedures requiring blockage of the sacral and lumbar nerves and for chronic pain tx.

Question 39

how is caudal epidural performed?

Answer 39

• It is usually identified as a groove above the coccyx, identify using the sacral cornu • Perform like a SAB. 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. -A distinct “pop” or “snap” is felt when the needle pierces the sacrococcygeal membrane. -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. -Aspirate for blood or CSF before injecting local anesthetic. -The epidural catheter can then be inserted through the needle to the desired level.

Question 40

Equipment for epidural:

Answer 40

An epidural tray • styletted Tuohy epidural -16 to 18 gauge, 8 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. • Epidural catheters -durable, flexible plastic -designed to pass through the lumen of the Tuohy needle. -Marking every 1 cm. • dressing for the puncture site and tape to secure the catheter on the patient’s back. Usually a large OpSite dressing with 2 inch silk or cloth adhesive

Question 41

insertion of epidural -midline approach:

Answer 41

Midline - This approach is most commonly used for lumbar or low thoracic 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 1.Identify the vertebral level to be entered by surface landmarks (e.g.,crest of iliac spines L4 to L5, entry level usually L2-3 or L3-4). 2. Infiltrate skin with local anesthetic using 25-gauge11/2-in.needle at midpoint between two adjacent vertebrae to raise a large skin wheel 3. Without removing needle, infiltrate deeper tissues to alleviate pain and to assist with locating midline. 4. Insert epidural needle with stylet through same skin puncture.The dorsum of the CRNA’s non injecting hand rests on the patient’s back with the thumb and index finger holding the hub of the epidural needle (Bromage grip). 5. Advance the needle through the supraspinous ligament and into the interspinous ligament (approximately 3 cm depth) at which point the needle should sit firmly in the midline • Loss of Resistance: once the needle is firmly in the interspinous ligament or ligamentum flava, the stylet is removed. A glass or plastic syringe filled with 2-3 mL of air or normal saline is firmly attached. The needle is slowly advanced by application of pressure on the needle. Once the bevel passes through the yellow ligament and enters the epidural space, an immediate loss of resistance occurs. -The catheter is threaded into the epidural space 3-5 cm -If a parasthesia is encountered, due nerve root stimulation

Question 42

epidural: paramedian approach:

Answer 42

Paramedian approach - This approach offers a much larger opening into the epidural space than the midline approach. For entry level at T3 to T7, the midline approach is difficult if not impossible to use due to angulation of the spinous processes. 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 2. The epidural needle is advanced at that site perpendicular to the skin until the lamina is encountered 3. The needle is redirected and advanced at a 10- to 25-degree angle toward the midline 4. If bone is encountered, the needle is “walked off” the bone into the ligamentum flavum. 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 ligamentum flavum

Question 43

lumbar vs. thoracic paramedian:

Answer 43

Lumbar vs. Thoracic • The paramedian approach is easier especially in the midthoracic region (there is a greater incidence of false loss of resistance in the midline thoracic approach). o 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. o hypotension can occur in nearly all patients with a high thoracic epidural blockade. • Epidural anesthesia is ideally suited for thoracic surgery. • Placement and activation are similar to lumbar epidural placement, o the tip of the catheter should be placed at midincision level, usually above T8. o The sharp angulation of the spinous processes especially in the midthoracic area can make the midline approach difficult.

Question 44

After a negative aspiration and test dose: 1. usual medication regimen: 2. alternate regimen:

Answer 44

1. An initial dose of 3 to 6 mL of dilute bupivacaine (0.25% to 0.5%) 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. 2. Alternative regimen: Administer a loading dose with 10 to 15 mL of bupivacaine (0.125%) 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% with fentanyl or hydromorphone at 3 to 5 mL/h before the patient leaves the operating room.138

Question 45

combiined spinal epidural (CSE) 1. what is it good for (works in 2 ways)? 2. where is the only region of the spine it can be done? why?

Answer 45

1. Allows rapid onset and a dense block of a spinal with the ability to extend the spread and duration of the block with an epidural catheter. Since the subarachnoid space is entered with the SAB needle, this technique is only good for lumbar sites (ex. Gyn, lower extremity, *obstetric, perineal surgery). In essence, it is a combination of an intrathecal injection and then a epidural catheter is placed concurrently. -- Allows immediate analgesia and anesthesia with the SAB, then the ability to extend the block with the epidural. In Stage 1 labor, intrathecal opioids (without local) provide quick pain relief lasting 70-90 minutes, without sympathetic or motor blockade. Pts can still ambulate. The epidural can be dosed whenever it is needed. Often just the intrathecal component is enough pain relief and the epidural extension of analgesia is not needed. If needed, the epidural component can be used for laboring and/or for a Ceasarean section. It can be left in for post op pain relief. 2. this technique is only good for lumbar sites