Epidural Anesthesia

Question 1

_{Epidural Anesthesia}

The epidural space is a collapsible, distensible reservoir through which drugs spread and are removed by

Answer 1

Diffusion

Vascular transport

Leakage

Question 2

_{Epidural Anesthesia}

Factors Affecting Epidural Block Height

Answer 2

Drug Factors

^{Volume - Dose > Concentration > Additives}

Patient Factors

^{Elderly age - Pregnancy > Weight - Height - Pressure in adjacent body cavities}

Procedure Factors

^{Level of injection > Patient position > Speed of injection<br></br>Needle orifice direction}

Question 3

_{Factors Affecting Epidural Block Height - Drug Factors}

The most important drug-related factors that affect block height after the administration of local anesthetic in the epidural space are:

Answer 3

Volume

^{(1 to 2 mL of solution should be injected per segment to be blocked)}

Total mass of injectate

Question 4

_{Factors Affecting Epidural Block Height - Drug Factors}

T/F: Additives such as bicarbonate, epinephrine, and opioids influence onset, quality, and duration of analgesia and anesthesia

Answer 4

True

Question 5

_{Factors Affecting Epidural Block Height - Drug Factors}

T/F: Additives such as bicarbonate, epinephrine, and opioids affect epidural spread

Answer 5

False

Additives such as bicarbonate, epinephrine, and opioids do not affect epidural spread

Rather, they influence onset, quality, and duration of analgesia and anesthesia

Question 6

_{Factors Affecting Epidural Block Height - Patient Factors}

Patient Factors that can influence epidural block height include:

Answer 6

Age - Height - Weight - Pregnancy - CPAP

Age

^{Age can influence epidural block height.}

^{There appears to be a stronger correlation with age and block height in thoracic epidurals, with one study suggesting that <em>40% less volume is required in the elderly</em>}

^{Possible reasons include decreased leakage of local anesthetic through intervertebral foramina, decreased compliance of the epidural space in the elderly resulting in greater spread, or an increased sensitivity of the nerves in the elderly.}

Height

^{As with spinal anesthesia, it appears that only the extremes of patient height influence local anesthetic spread in the epidural space.}

Weight

^{Weight is not well correlated with block height in the settings of either lumbar or thoracic epidural anesthesia.}

Pregnancy

^{Less local anesthetic is required to produce the same epidural spread of anesthesia in pregnant patients.}

^{Although this may be in part a result of engorgement of epidural veins secondary to increased abdominal pressure, the effect also occurs in early pregnancy.}

CPAP

^{Also, continuous positive airway pressure increases the height of a thoracic epidural block.}

Question 7

_{Factors Affecting Epidural Block Height - Procedure Factors}

Procedure Factors that can influence epidural block height include:

Answer 7

Level of injection

Patient position

Question 8

_{Factors Affecting Epidural Block Height - Procedure Factors}

Procedure Factors that can influence epidural block height include:

Answer 8

Level of injection

^{The level of injection is the most important procedural-related factor that affects epidural block height.}

^{In the upper cervical region, spread of injectate is mostly caudal, in the midthoracic region spread is equally cephalad and caudal, and in the low thoracic region spread is primarily cephalad.}

^{After a lumbar epidural, spread is more cephalad than caudal.}

^{Some studies suggest that the total number of segments blocked is less in the lumbar region compared with thoracic levels for a given volume of injectate.}

Patient position

^{Patient position has been shown to affect spread of lumbar epidural injections, with preferential spread and faster onset to the dependent side in the lateral decubitus position.}

^{The sitting and supine positions do not affect epidural block height. However, the head-down tilt position does increase spread in obstetric patients.}

Question 9

_{Factors Affecting Epidural Block Height - Procedure Factors}

T/F: Needle bevel direction and speed of injection appear to influence the spread of a bolus injection.

Answer 9

False

Needle bevel direction and speed of injection do not appear to influence the spread of a bolus injection.

Question 10

_{Pharmacology - Local anesthetics for epidural use}

Local anesthetics for epidural use may be classified into

Answer 10

short-, intermediate-, and long-acting drugs.

Question 11

_{Pharmacology - Local anesthetics for epidural use}

How long does a single bolus dose of local anesthetic in the epidural space provide surgical anesthesia?

Answer 11

45 minutes up to 4 hours

^{This depends on the type of local anesthetic administered and the use of any additives}

Question 12

_{Pharmacology - Local anesthetics for epidural use}

Most commonly, why is an epidural catheter left in situ?

Answer 12

To provide indefinite extension of local anesthetic–based anesthesia or regular analgesia

Question 13

Short-Acting and Intermediate-Acting Local Anesthetics

Answer 13

Procaine

Chloroprocaine

Articaine

Lidocaine

Prilocaine

Mepivacaine

Question 14

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Similar to spinal anesthesia, 5% procaine is Not commonly used for epidural anesthesia - why not?

Answer 14

Slow onset

Unreliable Block

Poor quality Block

Question 15

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Chloroprocaine is available preservative free in 2% and 3% concentrations for epidural injection - which concentration is preferable for surgical anesthesia?

Answer 15

Chloroprocaine 3%

Chloroprocaine 3% is preferable for surgical anesthesia because the former may not produce muscle relaxation

Question 16

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Chloroprocaine 3% preparation has an onset time of … and a duration of …

Answer 16

10 to 15 minutes (Onset time)

Up to 60 minutes (Duration)

Question 17

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Adding epinephrine to Chloroprocaine 3% preparation prolongs the block for …

Answer 17

up to 90 minutes

Question 18

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Before the development of preservative-free preparations, large volumes (>25 mL) of chloroprocaine had been associated with:

Answer 18

Deep, aching, burning Lumbar back pain

_{This was thought to be secondary to the <em><strong>ethylene-di-amine-tetra-acetic acid</strong></em> that chelated calcium and caused a localized <em><strong>hypocalcemia</strong></em>}

Question 19

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Chloroprocaine can antagonize the effects of epidural morphine - This may be a result of

Answer 19

Opioid receptor antagonism

by either the chloroprocaine or a metabolite

Antagonism of an intracellular messenger and decreased morphine availability caused by a reduction in perineural pH are also proposed mechanisms

Question 20

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Morphine and chloroprocaine seem like an illogical combination because

Answer 20

The beneficial ultra-short duration of action of chloroprocaine

is offset by the addition of morphine

Question 21

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Articaine is not widely used for epidural anesthesia and has not been studied extensively. How does 2% articaine compare with epidural lidocaine?

Answer 21

Similar latency, spread, duration, and motor block

It has also been used for obstetric epidural analgesia

Question 22

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Lidocaine is available in 1% and 2% solutions; it has an onset time of … and a duration of …

Answer 22

10 to 15 minutes (onset time)

up to 120 minutes (duration)

Question 23

_{Short-Acting and Intermediate-Acting Local Anesthetics}

Lidocaine is available in 1% and 2% solutions; it has an onset time of 10 to 15 minutes and a duration of up to 120 minutes, which can be extended to 180 minutes with the addition of

Answer 23

Epinephrine

Question 24

_{Short-Acting and Intermediate-Acting Local Anesthetics}

T/F: Transient neurologic symptoms (TNS) is commonly associated with epidural lidocaine.

Answer 24

False

Transient neurologic symptoms (TNS) is associated with spinal lidocaine

Question 25

_{Short-Acting and Intermediate-Acting Local Anesthetics} _Prilocaine_ is available in 2% and 3% solutions. The 2% solution produces a sensory block with minimal motor block. Onset time is approximately ... , with a duration of approximately ...

Answer 25

_Prilocaine_ **15 minutes (**Onset time) **100 minutes (**duration)

Question 26

_{Short-Acting and Intermediate-Acting Local Anesthetics} Which has a more marked sensory blockade and a longer duration? A. lidocaine B. prilocaine

Answer 26

A. lidocaine **B. prilocaine**

Question 27

_{Short-Acting and Intermediate-Acting Local Anesthetics} In large doses, prilocaine is associated with

Answer 27

**Methemoglobinemia**

Question 28

_{Short-Acting and Intermediate-Acting Local Anesthetics} _Mepivacaine_ is available as 1%, 1.5%, and 2% preservative-free solutions. The 2% preparation has an onset time similar to lidocaine of approximately ... but a slightly longer duration of ...

Answer 28

**_Mepivacaine_** **15 minutes (**onset time) a slightly **longer duration** vs Lidocaine (up to **200 minutes** with epinephrine), Making it a _preferred option_ by some centers for _surgery_ of an _intermediate duration_

Question 29

Long-Acting Local Anesthetics

Answer 29

Ropivacaine Bupivacaine Levobupivacaine Tetracaine _R-BLT

Question 30

_{Long-Acting Local Anesthetics} **_Tetracaine_** is not widely used for epidural anesthesia because of:

Answer 30

**Unreliable block height** **Systemic toxicity** (in larger doses)

Question 31

_{Long-Acting Local Anesthetics} **_Bupivacaine_** is available in 0.25%, 0.5%, or 0.75% preservative-free solutions. The onset time is around ... with a duration of ...

Answer 31

**_Bupivacaine_** **20 minutes (**onset time) up to **225 minutes** (duration)

Question 32

_{Long-Acting Local Anesthetics} Bupivacaine duration is prolonged only slightly by the addition of ... to .... minutes.

Answer 32

**Epinephrine** | (to **240** minutes)

Question 33

_{Long-Acting Local Anesthetics} More dilute concentrations of Bupivacaine such as 0.125% to 0.25% can be used for

Answer 33

**Analgesia**

Question 34

_{Long-Acting Local Anesthetics} Long-Acting Local Anesthetics complications from using more diluted concentrations of _Bupivacaine_ such as 0.125% to 0.25% include:

Answer 34

_Cardiac_ and _central nervous system_ **toxicity** Potential for **motor block** (larger doses)

Question 35

_{Long-Acting Local Anesthetics} _Bupivacaine_ solutions of 0.5% and 0.75% are used to provide

Answer 35

**Surgical anesthesia**

Question 36

_{Long-Acting Local Anesthetics} Which version of _bupivacaine_ is currently under investigation for epidural use?

Answer 36

**Liposomal Bupivacaine** An epidural bolus of liposomal 0.5% bupivacaine provided similar onset but longer-lasting analgesia to boluses of plain bupivacaine

Question 37

_{Long-Acting Local Anesthetics} T/F: Liposomal Bupivacaine appears to be more toxic than plain bupivacaine or to have a differing cardiac safety profile

Answer 37

**False** Liposomal Bupivacaine _does not appear to be more toxic_ than plain bupivacaine or to have a differing cardiac safety profile

Question 38

_{Long-Acting Local Anesthetics} The benefit of Liposomal Bupivacaine, as with extended-release morphine is

Answer 38

_Lack of need for an epidural catheter_ **Conversely**, such extended-release boluses are _less titratable_ if for any reason the epidural needs to be terminated early

Question 39

_{Long-Acting Local Anesthetics} Which concentrations of _Levobupivacaine_ can be used as an epidural local anesthetic for surgical anesthesia?

Answer 39

_Levobupivacaine_ **0.5%** to **0.75%** concentrations (for **surgical anesthesia**)

Question 40

_{Long-Acting Local Anesthetics} Which concentrations of _Levobupivacaine_ can be used as an epidural local anesthetic for analgesia ?

Answer 40

_Levobupivacaine_ Concentrations of **0.125%** to **0.25%** (for **analgesia**)

Question 41

_{Long-Acting Local Anesthetics} Levobupivacaine administered epidurally has the same clinical characteristics as bupivacaine. The advantage of levobupivacaine over bupivacaine is that:

Answer 41

**_levobupivacaine_** is *less cardiotoxic* compared with bupivacaine

Question 42

_{Long-Acting Local Anesthetics} _Ropivacaine_ is available in 0.2%, 0.5%, 0.75%, and 1.0% preservative-free preparations - Which concentration are used for surgical anesthesia?

Answer 42

_Ropivacaine_ 0.5% to 1.0% (for surgical anesthesia)

Question 43

_{Long-Acting Local Anesthetics} _Ropivacaine_ is available in 0.2%, 0.5%, 0.75%, and 1.0% preservative-free preparations - Which concentration are used for analgesia?

Answer 43

_Ropivacaine_ **0.1%** to **0.2 %** (for **analgesia**)

Question 44

_{Long-Acting Local Anesthetics} Which is associated with a superior safety profile? A. Ropivacaine B. Bupivacaine

Answer 44

**A. _Ropivacaine_** ^{(Ropivacaine is also less cardiotoxic)} B. Bupivacaine ^{Data from animal models suggest that Bupivacaine has a 1.5 to 2.5 lower seizure threshold than Ropivacaine}

Question 45

_{Long-Acting Local Anesthetics​} T/F: When compared with bupivacaine and levobupivacaine, ropivacaine at equivalent concentrations has a relatively similar clinical profile

Answer 45

**True** ^{Ropivacaine has a slightly shorter duration of action and less motor block, although the reduced motor block may in fact reflect different potencies of the drugs rather than a true motor-sparing effect of ropivacaine} Epidurally administered ropivacaine is 40% less potent than bupivacaine.

Question 46

Epidural Additives

Answer 46

Vasoconstrictors Opioids α2-Agonists Other Drugs Carbonation and Bicarbonate

Question 47

Epidural Additives - Vasoconstrictors

Answer 47

**Epinephrine** ^{Epinephrine reduces vascular absorption of local anesthetics in the epidural space The local anesthetics vary in their responsiveness to epinephrine The effect is the most with lidocaine, mepivacaine, and chloroprocaine (up to 50% prolongation), with a lesser effect with bupivacaine, levobupivacaine, and etidocaine, and a limited effect with ropivacaine, which already has intrinsic vasoconstrictive properties Epinephrine itself may also have some analgesic benefits because it is absorbed into the CSF, where it can act on dorsal horn α2 receptors} **Phenylephrine** ^{Phenylephrine has been used in epidural anesthesia less widely than in spinal anesthesia, perhaps because it does not reduce peak blood levels of local anesthetic as effectively as epinephrine does during epidural use}

Question 48

_{Epidural Additives - Opioids} Benefit of opioids:

Answer 48

Synergistically **enhance the analgesic effects** of epidural local anesthetics, _without prolonging motor block_ A combination of local anesthetic and opioid _reduces the dose-related adverse effects_ of each drug independently The analgesic benefits of neuraxial opioids must be balanced against the dose-dependent side effects

Question 49

_{Epidural Additives - Opioids} _Ceiling effect_ of epidural opioids

Answer 49

As with intrathecal opioids, there appears to be a therapeutic ceiling effect _above which only side effects increase_

Question 50

_{Epidural Additives - Opioids} Opioids may also be used alone, particularly when there are concerns regarding

Answer 50

**Hemodynamic instability**

Question 51

_{Epidural Additives - Opioids​} How do Epidural opioids work?

Answer 51

By crossing the dura and arachnoid membrane to reach the CSF and spinal cord dorsal horn

Question 52

_{Epidural Additives - Opioids​} Why are Lipophilic opioids, such as fentanyl and sufentanil found in lower concentrations in CSF than hydrophilic opioids, such as morphine and hydromorphone?

Answer 52

They **partition into epidural fat**

Question 53

_{Epidural Additives - Opioids​} What's the principal analgesic mechanism of Fentanyl and sufentanil (Lipophilic opioids)?

Answer 53

Readily **absorbed into the systemic circulation**

Question 54

_{Epidural Additives - Opioids​​} _Epidural morphine_ is administered as a bolus of ..., with an onset time of ... and duration of ...

Answer 54

**_Epidural morphine_** 1 to 5 mg (bolus dose) 30 to 60 minutes (onset time) up to 24 hours (duration)

Question 55

_{Epidural Additives - Opioids​​} The optimal dose of _Epidural morphine_ that balances analgesia while minimizing side effects is

Answer 55

_Epidural morphine_ 2.5 to 3.75 mg ^{(Optimal dose that balances analgesia while minimizing side effects)}

Question 56

_{Epidural Additives - Opioids​​} At what dose can morphine be administered continuously through an epidural catheter?

Answer 56

_Morphine epidural catheter infusion_ **0.1 to 0.4 mg/hr**

Question 57

_{Epidural Additives - Opioids​​} Which is more hydrophilic? A. Hydromorphone B. Fentanyl

Answer 57

A. **_Hydromorphone_** B. Fentanyl

Question 58

_{Epidural Additives - Opioids​​} Which is more lipophilic? A. Hydromorphone B. Morphine

Answer 58

A. **_Hydromorphone_** B. Morphine

Question 59

_{Epidural Additives - Opioids​​} _Hydromorphone_ can be administered as a bolus of ..., with onset at .... minutes and a duration of ....

Answer 59

_Hydromorphone_ 0.4 to 1.5 mg (bolus dose) 15 to 30 minutes (onset time) 18 hours (duration)

Question 60

_{Epidural Additives - Opioids​​} _Hydromorphone_ used as an infusion is delivered at what rate?

Answer 60

_Hydromorphone_ 5 and 20 μg/hr (infusion rate)

Question 61

_{Epidural Additives - Opioids​​} The onset of _epidural fentanyl and sufentanil_ is ... and lasts only...

Answer 61

_Epidural fentanyl & sufentanil_ 5 to 15 minutes (onset) 2 to 3 hours (duration)

Question 62

_{Epidural Additives - Opioids​​} Which bolus doses of _Epidural fentanyl & sufentanil_ may be used to provide analgesia?

Answer 62

_Epidural fentanyl & sufentanil_ Bolus doses of **10 to 100 μg** (analgesia)

Question 63

_{Epidural Additives - Opioids​​} _Diamorphine_ is available in the United Kingdom and used in doses of ... as epidural boluses, or approximately ... in an infusion

Answer 63

_Diamorphine_ 2 to 3 mg (epidural bolus) 0.05 mg/mL (infusion)

Question 64

_{Epidural Additives - Opioids​​} The extended-release liposomal formulation of morphine used as a single-shot lumbar epidural dose, thereby avoiding issues and side effects of a continuous local anesthetic infusion and indwelling catheters, particularly in patients receiving anticoagulants is also known as:

Answer 64

**_Depodur_**

Question 65

_{Epidural Additives - Opioids​​} ## Footnote When administered before surgery (or after clamping of the cord in cesarean deliveries), _Depodur_ can provide pain relief for how long?

Answer 65

up to **48 hours**

Question 66

_{Epidural Additives - Opioids​​} What dose of _Depodur_ is recommended for lower abdominal surgery

Answer 66

_Depodur_ 10 to 15 mg ^{(lower abdominal surgery)}

Question 67

_{Epidural Additives - Opioids​​} What dose of _Depodur_ is recommendedfor major lower limb orthopedic surgery?

Answer 67

_Depodur_ 15 mg ^{(major lower limb orthopedic surgery)}

Question 68

Epidural Additives - α2-Agonists

Answer 68

**Clonidine** ^{Epidural clonidine can prolong sensory block to a greater extent than motor block The mechanism appears to be mediated by the opening of potassium channels and subsequent membrane hyperpolarization rather than an α2-agonist effect The addition of clonidine reduces both epidural local anesthetic and opioid requirements Other benefits of clonidine may include a reduced immune stress and cytokine response Epidural clonidine does have a variety of side effects including hypotension, bradycardia, dry mouth, and sedation The cardiovascular effects may be greatest when clonidine is administered in the epidural space at the thoracic level} **Dexmedetomidine** ^{In preliminary studies, epidural dexmedetomidine has also been shown to reduce intraoperative anesthetic requirements, improve postoperative analgesia, and prolong both sensory and motor block}

Question 69

Epidural Additives - Other Drugs

Answer 69

**Ketamine** ^{Conflicting reports exist regarding the benefit of epidural ketamine and whether it is neurotoxic} **Neostigmine** ^{Epidural neostigmine provides labor analgesia before local anesthetic infusion without causing respiratory depression, hypotension, or motor impairment} **Midazolam - Tramadol - Dexamethasone - Droperidol** ^Have also been studied but are not commonly used

Question 70

Epidural Additives - Carbonation and Bicarbonate

Answer 70

Many local anesthetic preparations have a pH between 3.5 and 5.5 for chemical stability and bacteriostasis At these low pHs, a higher proportion of the drug is in the ionized form and is therefore unable to cross nerve membranes to reach the internal binding site on sodium channels Both carbonation of the solution and adding bicarbonate have been used in an attempt to _increase the solution pH_, and therefore the _non-ionized free-base proportion of local anesthetic_ Although carbonation may theoretically increase the speed of onset and quality of the block by producing more rapid intraneural diffusion and more rapid penetration of connective tissue surrounding the nerve trunk, available data suggest that there are no clinical advantages for carbonated solutions

Question 71

Epidural Technique

Answer 71

Preparation Position Projection and Puncture Paramedian Approach

Question 72

Epidural Technique - Preparation

Answer 72

**Patient preparation** ^{Patient preparation as previously described for spinal anesthesia must equally be applied to epidural anesthesia, namely consent, monitoring, and resuscitation equipment, intravenous access, and choosing the patient and drugs appropriately depending on comorbidities and the nature of surgery} **Sterility** ^{Sterility is arguably even more important than spinal anesthesia because a catheter is often left in situ} **Surgical field** ^{The extent of the surgical field must be understood so that the epidural may be inserted at the appropriate level—that is, the lumbar, low-, mid-, or high-thoracic, or less commonly, cervical} **Epidural needles** ^{A variety of epidural needles have been used for epidural anesthesia, but Tuohy needles are most common These needles are usually 16 to 18 g in size and have a 15- to 30-degree curved, blunt “Huber” tip designed to both reduce the risk of accidental dural puncture and guide the catheter cephalad The needle shaft is marked in 1-cm intervals so that depth of insertion can be identified} **Epidural catheter** ^{The catheter is made of a flexible, calibrated, durable, radiopaque plastic with either a single end hole or multiple side orifices near the tip Several investigators have found that multiple-orifice catheters are superior, with a reduced incidence of inadequate analgesia However, the use of multiorifice catheters in pregnant women resulted in a more frequent incidence of epidural vein cannulation} **Method identifying the epidural space** ^{The method of identifying the epidural space must also be predetermined Most practitioners use a loss-of-resistance technique to either air or saline, rather than the hanging drop technique, both of which are described later If a loss-of-resistance technique is used, an additional decision about the type of syringe (i.e., glass versus low-resistance plastic and Luer-Lok versus friction hub) is required}

Question 73

Epidural Technique - Position

Answer 73

The **sitting** and **lateral decubitus** positions necessary for epidural puncture are the same as those for spinal anesthesia As before, inadequate positioning of the patient can complicate an otherwise meticulous technique Shorter insertion times occur in the sitting position for thoracic epidurals compared with the lateral decubitus position, but ultimately, success rates are comparable As with spinal anesthesia, epidurals are performed with the **patient awake**

Question 74

_{Epidural Technique - Projection and Puncture} The level of needle insertion depends on:

Answer 74

Location of surgery

Question 75

_{Epidural Technique - Projection and Puncture} Important surface landmarks needle insertion include:

Answer 75

**Vertebra prominens** ^(C7) **Root of the scapular spine** ^(T3) **Inferior angle of the scapula** ^{(corresponding to the T7 vertebral body)} **Intercristal line** ^{(corresponding to the L4-L5 interspace)}

Question 76

_{Epidural Technique - Projection and Puncture} Ultrasonography may be useful to identify the correct thoracic space; it is less commonly used for thoracic epidural insertion, however, because

Answer 76

_Acoustic shadows_ make visualization of landmarks such as the ligamentum flavum and intrathecal space more difficult

Question 77

_{Epidural Technique - Projection and Puncture} A variety of different needle approaches exist, including:

Answer 77

Midline Paramedian Modified paramedian (Taylor approach) Caudal

Question 78

_{Epidural Technique - Projection and Puncture} Suggested Epidural Insertion Sites for Hip surgery, Lower extremity, Obstetric analgesia:

Answer 78

Lumbar L2-L5

Question 79

_{Epidural Technique - Projection and Puncture} Suggested Epidural Insertion Sites for Colectomy, Anterior resection Upper abdominal surgery:

Answer 79

**T6-T8** **Lower thoracic** Spread more cranial than caudal

Question 80

_{Epidural Technique - Projection and Puncture} Suggested Epidural Insertion Sites for Thoracic Surgical Procedures

Answer 80

T2-T6 Midpoint of surgical incision

Question 81

_{Epidural Technique - Projection and Puncture} Which needle approch approach is commonly chosen for lumbar and low thoracic approaches

Answer 81

**Midline approach**

Question 82

_{Epidural Technique - Projection and Puncture} Describe the Midline approach?

Answer 82

After local anesthetic infiltration of the skin, the nondominant hand can be rested on the back of the patient, with the thumb and index finger holding the needle hub or wing The angle of approach should be only slightly cephalad in the lumbar and low-thoracic regions, whereas in the midthoracic region, the approach should be more cephalad because of the significant downward angulation of the spinous processes In a controlled fashion, the needle should be advanced with the stylet in place through the supraspinous ligament and into the interspinous ligament, at which point the stylet can be removed and the syringe attached Needle should rest firmly in the tissues if in the correct place

Question 83

_{Epidural Technique - Projection and Puncture} Which methods could be used to confirm needle placement in the ligamentum of flavum?

Answer 83

**Loss-of-resistance** method **Hanging-drop** method _{Recommended before attaching the syringe, but this may be difficult, particularly for novices; however, this may allow an improved appreciation of epidural anatomy for the operator}

Question 84

_{Epidural Technique - Projection and Puncture} If the needle is merely inserted into the supraspinous ligament and then loss-of-resistance or hanging-drop insertion is begun, there is an increased chance of

Answer 84

**False loss-of-resistance** Possibly because of defects in the interspinous ligament Such false-positive rates can be as high as 30%.

Question 85

_{Epidural Technique - Projection and Puncture} Two most non-compressible media used to detect lost of resistance when identigying the epidural space

Answer 85

**Air** or **saline** ^{Each involves intermittent (for air) or constant (for saline) gentle pressure applied to the bulb of the syringe with the dominant thumb while the needle is advanced with the nondominant hand A combination of air and saline may also be used, incorporating 2 mL of saline and a small (0.25 mL) air bubble}

Question 86

_{Epidural Technique - Projection and Puncture​} Which structure is usually identified as a tougher structure with increased resistance, and when the epidural space is subsequently entered, the pressure applied to the syringe plunger allows the solution to flow without resistance into the epidural space

Answer 86

**Ligamentum flavum**

Question 87

_{Epidural Technique - Projection and Puncture​} There are reports that air is less reliable in identifying the epidural space - Why?

Answer 87

Results in a higher chance of **Incomplete block** May also cause both **Pneumocephalus** ^{(which can result in headaches)} **Venous air embolism** in rare cases ^{If air is chosen, the amount of air injected after loss-of-resistance should therefore be minimized}

Question 88

_{Epidural Technique - Projection and Puncture​} T/F: A recent meta-analysis suggested that there was no difference in adverse outcome in the obstetric population when air or saline was used to confirm needle placement

Answer 88

**True**

Question 89

_{Epidural Technique - Projection and Puncture​} T/F: Fluid inserted through the epidural needle before catheter insertion reduces the risk of epidural vein cannulation by the catheter

Answer 89

**True**

Question 90

_{Epidural Technique - Projection and Puncture​} What's a disadvantage of using saline to identify the epidural space?

Answer 90

More difficult to readily detect an _accidental dural puncture_

Question 91

_{Epidural Technique - Projection and Puncture​} An alternative method of identifying the epidural space whereby After the needle is placed into the ligamentum flavum, a drop of solution such as saline is placed within the hub of the needle. When the needle is advanced into the epidural space, the solution should be “sucked in.” This method is known as:

Answer 91

**Hanging-drop technique** ^{The theory behind this maneuver has traditionally been attributed to subatmospheric pressure in the epidural space, although recent experimental evidence in the cervical region suggests that using negative-pressure methods are poorly reliable and only useful in the sitting position The subatmospheric pressure has been related to expansion of the epidural space as the needle pushes the dura away from the ligamentum flavum The negative intrathoracic pressure may influence the pressure in the epidural space in the thoracic region and should be maximal during inspiration Timing needle advancement to coincide with inspiration may be difficult, however.}

Question 92

_{Epidural Technique - Projection and Puncture​} When a lumbar **midline approach** is used, the depth from skin to the ligamentum flavum commonly reaches

Answer 92

**4 cm** with the depth in most (80%) patients being between 3.5 and 6 cm; it can be longer or shorter in obese or very thin patients, respectively Ultrasonography may be useful to predict the depth before needle insertion In the lumbar region, the ligamentum flavum is 5 to 6 mm thick in the midline

Question 93

_{Epidural Technique - Projection and Puncture​} When a thoracic approach is chosen, needle control is of equal or greater importance because

Answer 93

injury to the spinal cord is possible if the needle is advanced too far

Question 94

_{Epidural Technique - Projection and Puncture​} T/F: There are no data to suggest that approaching the epidural space at the lumbar level is any more or less safe than at the thoracic level

Answer 94

**True** This may be partly because those using the thoracic technique are most often anesthesiologists with considerable experience in lumbar epidural anesthesia In addition, the increased angle of needle insertion in the thoracic region may theoretically provide an element of safety in that the more acute angle necessary to gain access to the epidural space provides some margin of safety

Question 95

_{Epidural Technique - Projection and Puncture​} When the epidural space is identified, the depth of the needle at the skin should be noted - How should the syringe and the catheter be then manipulated?

Answer 95

The syringe can then be removed and a catheter gently threaded to approximately the **15- to 18-cm** mark to ensure a sufficient length has entered the _epidural space_ The needle can then be carefully withdrawn, and the catheter is withdrawn to leave 4 to 6 cm in the space

Question 96

_{Epidural Technique - Projection and Puncture​} What risks are associated with catheter space less than 4 cm in length in the epidural space?

Answer 96

Catheter **dislodgement** _Inadequate analgesia_

Question 97

_{Epidural Technique - Projection and Puncture​​} Threading more catheter may increase the likelihood of:

Answer 97

Catheter malposition or complications

Question 98

_{Epidural Technique - Projection and Puncture​​} What is one of the causes of a failed block

Answer 98

**False loss-of-resistance** ^{As described earlier, a false loss-of-resistance can occur and is one of the causes of a failed block}

Question 99

_{Epidural Technique - Projection and Puncture​​​} The test that stimulates the spinal nerve roots with a low electrical current conducted through normal saline in the epidural space and an electrically conducting catheter is also known as:

Answer 99

**Tsui test** The Tsui test may be used to confirm the epidural catheter position

Question 100

_{Epidural Technique - Projection and Puncture​​​} How is the Tsui test performed?

Answer 100

A metal-containing catheter must be used, with the cathode lead of the nerve stimulator connected to the catheter via an electrode adapter, whereas the anode lead is connected to an electrode on the patient’s skin At currents of approximately 1 to 10 mA, corresponding muscle twitches (i.e., intercostal or abdominal wall muscles for thoracic epidural catheters) can be used to identify catheter tip location Subarachnoid and subdurally positioned epidural catheters elicit motor responses at a much lower threshold current (\<1 mA), because the stimulating catheter is in very close or direct contact with highly conductive CSF

Question 101

_{Epidural Technique - Projection and Puncture​​​} When the catheter is positioned at the desired depth, it must be secured to the skin - How is this achieved?

Answer 101

**Commercial fixation devices** ^{Commercial fixation devices exist, and some are superior to tape alone} **Tunneling** ^{Tunneling can reduce catheter migration and improve lasting block success However, tunneling has not been compared with noninvasive catheter fixation devices in a welldesigned study}

Question 102

_{Epidural Technique} Which approach is particularly useful in the mid- to high thoracic region, where the angulation of the spine and the narrow spaces render the midline approach problematic

Answer 102

**Paramedian approach**

Question 103

_{Epidural Technique - Paramedian approach} Describe the Paramedian approach

Answer 103

The needle should be inserted 1 to 2 cm lateral to the inferior tip of the spinous process corresponding to the vertebra above the desired interspace The needle is then advanced horizontally until the lamina is reached and then redirected medially and cephalad to enter the epidural space

Question 104

_{Epidural Technique - Paramedian approach} The modified paramedian approach via the L5-S1 interspace, which may be useful in trauma patients who cannot tolerate or are not able to maintain a sitting position is also known as

Answer 104

**Taylor approach** The needle is inserted 1 cm medial and 1 cm inferior to the posterior superior iliac spine and is angled medially and cephalad at a 45- to 55-degree angle.

Question 105

_{Epidural Technique - Paramedian approach} Before initiating an epidural local anesthetic infusion, a _test dose_ may be administered - The purpose of this is:

Answer 105

_To Exclude intrathecal or intravascular catheter placement_ A small volume of lidocaine 1.5% with epinephrine is traditionally used for this purpose

Question 106

_{Epidural Technique - Paramedian approach} What's the best pharmacologic method of detecting intravascular placement of epidural catheter?

Answer 106

A recent systematic review found reasonable evidence that **10 to 15 μg of epinephrine alone** in _nonpregnant adult patients_ was the best pharmacologic method of detecting intravascular placement Endpoints of an increase in systolic blood pressure more than 15 mm Hg or an increase in heart rate more than 10 beats/min may be used

Question 107

_{Epidural Technique - Paramedian approach} What's the optimal method of detecting intrathecal or subdural catheter placement?

Answer 107

Could not be ascertained