Epidural Anesthesia Flashcards

Question 1

Q

_{Epidural Anesthesia}

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

Answer

A

Diffusion

Vascular transport

Leakage

Question 2

Q

_{Epidural Anesthesia}

Factors Affecting Epidural Block Height

Answer

A

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 Needle orifice direction}

Question 3

Q

_{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

A

Volume

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

Total mass of injectate

Question 4

Q

_{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

Question 5

Q

_{Factors Affecting Epidural Block Height - Drug Factors}

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

Answer

A

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

Q

_{Factors Affecting Epidural Block Height - Patient Factors}

Patient Factors that can influence epidural block height include:

Answer

A

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 40% less volume is required in the elderly}

^{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

Q

_{Factors Affecting Epidural Block Height - Procedure Factors}

Procedure Factors that can influence epidural block height include:

Answer

A

Level of injection

Patient position

Question 8

Q

_{Factors Affecting Epidural Block Height - Procedure Factors}

Procedure Factors that can influence epidural block height include:

Answer

A

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

Q

_{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

A

False

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

Question 10

Q

_{Pharmacology - Local anesthetics for epidural use}

Local anesthetics for epidural use may be classified into

Answer

A

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

Question 11

Q

_{Pharmacology - Local anesthetics for epidural use}

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

Answer

A

45 minutes up to 4 hours

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

Question 12

Q

_{Pharmacology - Local anesthetics for epidural use}

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

Answer

A

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

Question 13

Q

Short-Acting and Intermediate-Acting Local Anesthetics

Answer

A

Procaine

Chloroprocaine

Articaine

Lidocaine

Prilocaine

Mepivacaine

Question 14

Q

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

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

Answer

A

Slow onset

Unreliable Block

Poor quality Block

Question 15

Q

_{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

A

Chloroprocaine 3%

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

Question 16

Q

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

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

Answer

A

10 to 15 minutes (Onset time)

Up to 60 minutes (Duration)

Question 17

Q

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

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

Answer

A

up to 90 minutes

Question 18

Q

_{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

A

Deep, aching, burning Lumbar back pain

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

Question 19

Q

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

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

Answer

A

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

Q

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

Morphine and chloroprocaine seem like an illogical combination because

Answer

A

The beneficial ultra-short duration of action of chloroprocaine

is offset by the addition of morphine

Question 21

Q

_{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

A

Similar latency, spread, duration, and motor block

It has also been used for obstetric epidural analgesia

Question 22

Q

_{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

A

10 to 15 minutes (onset time)

up to 120 minutes (duration)

Question 23

Q

_{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

A

Epinephrine

Question 24

Q

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

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

Answer

A

False

Transient neurologic symptoms (TNS) is associated with spinal lidocaine

Question 25

Q

_{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

A

Prilocaine

15 minutes (Onset time)

100 minutes (duration)

Question 26

Q

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

Which has a more marked sensory blockade and a longer duration?

A. lidocaine

B. prilocaine

Answer

A

A. lidocaine

B. prilocaine

Question 27

Q

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

In large doses, prilocaine is associated with

Answer

A

Methemoglobinemia

Question 28

Q

_{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

A

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

Q

Long-Acting Local Anesthetics

Answer

A

Ropivacaine

Bupivacaine

Levobupivacaine

Tetracaine

_R-BLT

Question 30

Q

_{Long-Acting Local Anesthetics}

Tetracaine is not widely used for epidural anesthesia because of:

Answer

A

Unreliable block height

Systemic toxicity (in larger doses)

Question 31

Q

_{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

A

Bupivacaine

20 minutes (onset time)

up to 225 minutes (duration)

Question 32

Q

_{Long-Acting Local Anesthetics}

Bupivacaine duration is prolonged only slightly by the addition of … to …. minutes.

Answer

A

Epinephrine

(to 240 minutes)

Question 33

Q

_{Long-Acting Local Anesthetics}

More dilute concentrations of Bupivacaine such as 0.125% to 0.25% can be used for

Answer

A

Analgesia

Question 34

Q

_{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

A

Cardiac and central nervous system toxicity

Potential for motor block (larger doses)

Question 35

Q

_{Long-Acting Local Anesthetics}

Bupivacaine solutions of 0.5% and 0.75% are used to provide

Answer

A

Surgical anesthesia

Question 36

Q

_{Long-Acting Local Anesthetics}

Which version of bupivacaine is currently under investigation for epidural use?

Answer

A

Liposomal Bupivacaine

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

Question 37

Q

_{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

A

False

Liposomal Bupivacaine does not appear to be more toxic than plain bupivacaine or to have a differing cardiac safety profile

Question 38

Q

_{Long-Acting Local Anesthetics}

The benefit of Liposomal Bupivacaine, as with extended-release morphine is

Answer

A

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

Q

_{Long-Acting Local Anesthetics}

Which concentrations of Levobupivacaine can be used as an epidural local anesthetic for surgical anesthesia?

Answer

A

Levobupivacaine

0.5% to 0.75% concentrations

(for surgical anesthesia)

Question 40

Q

_{Long-Acting Local Anesthetics}

Which concentrations of Levobupivacaine can be used as an epidural local anesthetic for analgesia ?

Answer

A

Levobupivacaine

Concentrations of 0.125% to 0.25%

(for analgesia)

Question 41

Q

_{Long-Acting Local Anesthetics}

Levobupivacaine administered epidurally has the same clinical characteristics as bupivacaine. The advantage of levobupivacaine over bupivacaine is that:

Answer

A

levobupivacaine is less cardiotoxic compared with bupivacaine

Question 42

Q

_{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

A

Ropivacaine

0.5% to 1.0%

(for surgical anesthesia)

Question 43

Q

_{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

A

Ropivacaine

0.1% to 0.2 %

(for analgesia)

Question 44

Q

_{Long-Acting Local Anesthetics}

Which is associated with a superior safety profile?

A. Ropivacaine

B. Bupivacaine

Answer

A

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

Q

_{Long-Acting Local Anesthetics}

T/F: When compared with bupivacaine and levobupivacaine, ropivacaine at equivalent concentrations has a relatively similar clinical profile

Answer

A

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

Q

Epidural Additives

Answer

A

Vasoconstrictors

Opioids

α2-Agonists

Other Drugs

Carbonation and Bicarbonate

Question 47

Q

Epidural Additives - Vasoconstrictors

Answer

A

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

Q

_{Epidural Additives - Opioids}

Benefit of opioids:

Answer

A

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

Q

_{Epidural Additives - Opioids}

Ceiling effect of epidural opioids

Answer

A

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

Question 50

Q

_{Epidural Additives - Opioids}

Opioids may also be used alone, particularly when there are concerns regarding

Answer

A

Hemodynamic instability

Question 51

Q

_{Epidural Additives - Opioids}

How do Epidural opioids work?

Answer

A

By crossing the dura and arachnoid membrane

to reach the CSF and spinal cord dorsal horn

Question 52

Q

_{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

A

They partition into epidural fat

Question 53

Q

_{Epidural Additives - Opioids}

What’s the principal analgesic mechanism of Fentanyl and sufentanil (Lipophilic opioids)?

Answer

A

Readily absorbed into the systemic circulation

Question 54

Q

_{Epidural Additives - Opioids}

Epidural morphine is administered as a bolus of …, with an onset time of … and duration of …

Answer

A

Epidural morphine

1 to 5 mg (bolus dose)

30 to 60 minutes (onset time)

up to 24 hours (duration)

Question 55

Q

_{Epidural Additives - Opioids}

The optimal dose of Epidural morphine that balances analgesia while minimizing side effects is

Answer

A

Epidural morphine

2.5 to 3.75 mg

^{(Optimal dose that balances analgesia while minimizing side effects)}

Question 56

Q

_{Epidural Additives - Opioids}

At what dose can morphine be administered continuously through an epidural catheter?

Answer

A

Morphine epidural catheter infusion

0.1 to 0.4 mg/hr

Question 57

Q

_{Epidural Additives - Opioids}

Which is more hydrophilic?

A. Hydromorphone

B. Fentanyl

Answer

A

A. Hydromorphone

B. Fentanyl

Question 58

Q

_{Epidural Additives - Opioids}

Which is more lipophilic?

A. Hydromorphone

B. Morphine

Answer

A

A. Hydromorphone

B. Morphine

Question 59

Q

_{Epidural Additives - Opioids}

Hydromorphone can be administered as a bolus of …, with onset at …. minutes and a duration of ….

Answer

A

Hydromorphone

0.4 to 1.5 mg (bolus dose)

15 to 30 minutes (onset time)

18 hours (duration)

Question 60

Q

_{Epidural Additives - Opioids}

Hydromorphone used as an infusion is delivered at what rate?

Answer

A

Hydromorphone

5 and 20 μg/hr (infusion rate)

Question 61

Q

_{Epidural Additives - Opioids}

The onset of epidural fentanyl and sufentanil is … and lasts only…

Answer

A

Epidural fentanyl & sufentanil

5 to 15 minutes (onset)

2 to 3 hours (duration)

Question 62

Q

_{Epidural Additives - Opioids}

Which bolus doses of Epidural fentanyl & sufentanil may be used to provide analgesia?

Answer

A

Epidural fentanyl & sufentanil

Bolus doses of 10 to 100 μg (analgesia)

Question 63

Q

_{Epidural Additives - Opioids}

Diamorphine is available in the United Kingdom and used in doses of … as epidural boluses, or approximately … in an infusion

Answer

A

Diamorphine

2 to 3 mg (epidural bolus)

0.05 mg/mL (infusion)

Question 64

Q

_{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

A

Depodur

Answer 64

A

up to 48 hours

Answer 65

A

Depodur

10 to 15 mg

^{(lower abdominal surgery)}

Answer 66

A

Depodur

15 mg

^{(major lower limb orthopedic surgery)}

Answer 67

A

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}

Answer 68

A

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

Answer 69

A

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

Answer 70

A

Preparation

Position

Projection and Puncture

Paramedian Approach

Answer 71

A

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}

Answer 72

A

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

Answer 73

A

Location of surgery

Answer 74

A

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)}

Answer 75

A

Acoustic shadows make visualization of landmarks such as the ligamentum flavum and intrathecal space more difficult

Answer 76

A

Midline

Paramedian

Modified paramedian (Taylor approach)

Caudal

Answer 77

A

Lumbar L2-L5

Answer 78

A

T6-T8

Lower thoracic

Spread more cranial than caudal

Answer 79

A

T2-T6

Midpoint of surgical incision

Answer 80

A

Midline approach

Answer 81

A

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

Answer 82

A

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}

Answer 83

A

False loss-of-resistance

Possibly because of defects in the interspinous ligament

Such false-positive rates can be as high as 30%.

Answer 84

A

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}

Answer 85

A

Ligamentum flavum

Answer 86

A

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}

Answer 87

A

More difficult to readily detect an accidental dural puncture

Answer 88

A

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.}

Answer 89

A

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

Answer 90

A

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

Answer 91

A

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

Answer 92

A

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

Answer 93

A

Catheter dislodgement

Inadequate analgesia

Answer 94

A

Catheter malposition or complications

Answer 95

A

False loss-of-resistance

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

Answer 96

A

Tsui test

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

Answer 97

A

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

Answer 98

A

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}

Answer 99

A

Paramedian approach

Answer 100

A

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

Answer 101

A

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.

Answer 102

A

To Exclude intrathecal or intravascular catheter placement

A small volume of lidocaine 1.5% with epinephrine is traditionally used for this purpose

Answer 103

A

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

Answer 104

A

Could not be ascertained

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Epidural Anesthesia Flashcards

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