Spinal, Epidural and Caudal Anesthesia

Question 1

Blockade of … is responsible for the decrease in arterial blood pressure (cardiac output and systemic vascular resistance) associated with neuraxial techniques

Answer 1

the peripheral (T1-L2) and cardiac (T1-T4) sympathetic fibers

Question 2

Which are the most important determinants for the spread (i.e., block height) of spinal anesthesia?

Answer 2

Cerebrospinal fluid volume and local anesthetic baricity

Question 3

The first case of spinal anesthesia in humans was performed by … in … using the local anesthetic …

Answer 3

August Bier

1898

cocaine

Question 4

Lumbar epidural anesthesia in humans was first described by … in …, the loss-of-resistance technique by …in the …, continuous caudal for obstetrics by Hingson in 1941, and lumbar epidural catheterization for surgery by … in …

Answer 4

Pagés

1921

Dogliotti

1930s

Curbelo

1947

Question 5

The spinal cord is continuous with the brainstem proximally and terminates distally in the … as the … (fibrous extension) and the … (neural extension). This distal termination varies from … in infants to the lower border of … in adults because of differential growth rates between the bony vertebral canal and the central nervous system

Answer 5

conus medullaris

filum terminale

cauda equina

L3

L1

Question 6

Which membrane functions as the principal barrier to drugs crossing into (and out of) the CSF?

Answer 6

The arachnoid mater is a delicate, nonvascular membrane that functions as the principal barrier to drugs crossing into (and out of) the CSF and is estimated to account for 90% of the resistance to drug migration

Question 7

Contents of the epidural space include the nerve roots and fat, areolar tissue, lymphatics, and blood vessels including the well-organized … venous plexus

Answer 7

Batson

Question 8

The sacral … the terminal portion of the dural sac, which typically ends at …

Variation is found in this feature as well, with the termination of the dural sac
being … in children

Answer 8

canal contains

S2

lower

Question 9

Describe the arterial vascularization of the spinal cord

Answer 9

Anterior spinal artery (ASA):
- Runs the length of the spinal cord longitudinally along the anterior median fissure;
- Primary blood supply of anterior two-thirds of the spinal cord;
- The diameter of the ASA through the thoracic spinal cord is notably narrower when compared to its size in the cervical and lumbar regions. Thus, much of the blood flow to the thoracic spine derives from segmental arteries branching from the dorsal aorta;
- The anterior artery supplies the motor tracts and forms from the fusion of the vertebral arteries and receives reinforcement of blood supply from 6 to 8 radicular arteries.

Posterior spinal artery (right and left):
- Run longitudinally on each side of the midline of the posterolateral sulcus consistently through the length of the spinal cord;
- The two posterior spinal arteries originate directly from the vertebral arteries and are the primary blood supply to the posterior columns, dorsal grey matter, dorsal sensory columns - these arteries are often found to be discontinuous, and occasionally one artery will move across to supply the opposite side;
It is useful to think of the posterior spinal artery as a plexus as it often anastomoses with the contralateral posterior spinal artery and may receive anastomoses with the anterior spinal artery via a plexus that encases the cord.

Artery of Adamkiewic:
- It is the largest anterior radiculomedullary artery of that individual, contributing to its significant variation of location - it is also the largest anterior segmental artery;
- It typically arises from the left posterior intercostal artery and is the only significant arterial supply feeding the anterior spinal artery along the lower thoracic, lumbar, and sacral spinal cord;
- Due to its atypical nature, the artery of Adamkiewicz typically arises from the left side of the aorta between T8 and L2 in 75% of people, although it is important to realize that the artery of Adamkiewicz can also be present above T8 in about 20% of people - other less common variations exist, and collateral circulation with lumbar arteries exist.

• Other unnamed radicular arteries exist that also supply an important collateral support network.

Question 10

Describe the venous vascularization of the spinal cord

Answer 10

Venous drainage of the spinal cord follows a similar distribution as the spinal arteries. There are three longitudinal anterior spinal veins and three posterior spinal veins
that communicate with the segmental anterior and posterior radicular veins before draining into the internal vertebral venous plexus in the medial and lateral components of the epidural space.

Question 11

There are no veins in the posterior epidural space except those caudal to the L5-S1 disk

T or F

Answer 11

T

Question 12

Lumbosacral CSF has a constant pressure of approximately … cm H2O, but its volume varies by patient, in part because of differences in body habitus and weight.
It is estimated that CSF volume accounts for …% of the variability in peak block height and regression of sensory and motor blockade. Nevertheless, except for body weight (…CSF in subjects with high body mass index [BMI]), the volume of CSF does not correlate with other anthropomorphic measurements available clinically

Answer 12

15

80

less

Question 13

Describe how the diferent fibers are clinically affected in the neuroaxis anesthesia

Answer 13

The small preganglionic sympathetic fibers (B fibers, 1-3 μm, minimally myelinated) are most sensitive to local anesthetic blockade.

Among the sensory nerves, the C fibers (0.3-1 μm, unmyelinated), which conduct cold temperature sensation, are blocked more readily or earlier than the A-delta fibers (1-4 μm, myelinated), which conduct pinprick sensation.

The A-beta fibers (5-12 μm, myelinated), which conduct touch sensation, are the last
to be affected among the sensory fibers.

The larger A-alpha motor fibers (12-20 μm, myelinated) are more resistant than any of the sensory fibers.

Regression of blockade (“recovery”) follows in the reverse order: motor function followed first by touch, then pinprick, and finally cold sensation

Question 13

There is evidence that adipose tissue in the epidural space … with age, and this … in epidural space in adipose tissue may dominate the age-related changes in epidural dose requirements

Answer 13

diminishes

decrease

Question 14

Another manifestation of relative sensitivity or susceptibility to the effects of local anesthetics in the neuroaxis anesthesia is the observed differences in the peak block height (highest or most cephalad level of anesthesia) according to each sensory modality, which is termed differential sensory block. Describe It

Answer 14

The level of anesthesia to cold sensation (also an approximate level of sympathetic blockade) is most cephalad and is on average one to two spinal segments higher than the level of pinprick anesthesia, which in turn is one to two segments higher than the level of touch anesthesia

Question 15

When local anesthetic is injected directly into the subarachnoid space during spinal anesthesia, it diffuses through the pia mater and penetrates through the … (…) to reach the deeper dorsal root ganglia.

Furthermore, a portion of the subarachnoid drug diffuses outward through the arachnoid and dura mater to enter the epidural space, whereas some is taken up by the blood vessels of the pia and dura maters

Answer 15

spaces of Virchow Robin

extensions of the subarachnoid space accompanying the blood vessels that invaginate the spinal cord from the pia mater

Question 16

In spinal anesthesia, drug penetration and uptake is directly proportionate to the …, but is inversely related to …

Answer 16

drug mass, CSF drug concentration, contact surface area, lipid content (high in spinal cord and myelinated nerves), and local tissue vascular supply

nerve root size

Question 17

The extent of the sympathectomy is typically described as extending for … above the sensory block level with spinal anesthesia and at the same level with epidural anesthesia

Answer 17

two to six dermatomes

Question 18

If normal cardiac output is main- tained, systemic vascular resistance should decrease only …% after neuraxial blockade in healthy normovolemic patients, even with nearly total sympathectomy. In elderly patients with cardiac disease, systemic vascular resistance may decrease almost …% after spinal anesthesia, whereas cardiac output decreases only ..%.

Answer 18

15% to 18

25

10

Question 19

Explain the possible correlation between the spinal anesthesia and the Bezold-Jarisch reflex

Answer 19

The Bezold-Jarisch reflex may be a possible cause of profound bradycardia and circulatory collapse after spinal anesthesia, especially in the presence of hypovolemia, when a small end-systolic left ventricular volume may trigger a mechanoreceptor-mediated bradycardia

Question 20

After spinal anesthesia, although hypotension will trigger a compensatory baroreceptor sympathetic response (vasoconstriction and increased heart rate) above the level of blockade, the reduction in venous return and right atrial filling causes a decrease in signal output from … , leading to a … increase in … .

The two opposing responses are usually in check with a minimal change in heart rate (or a slight reduction). However, when neuraxial anesthesia is extended to the … level, blockade of the … fibers in addition to a marked reduction in venous return may result in severe bradycardia and even asystole because of unopposed parpsympathetic activity

Answer 20

intrinsic chronotropic stretch receptors located in the right atrium and great veins

parasympathetic activity (vagal tone)

T1

cardioaccelerator

Question 21

A high thoracic block in patients with ischemic heart disease is harmful because it,s associated with increase global and regional myocardial function and oxygen consumption

T or F

Answer 21

F

A high thoracic block in patients with ischemic heart disease can be beneficial, with improvement in global and regional myocardial function and reversal of ischemic changes likely a result of reduced myocardial oxygen demand and left ventricular afterload.

Both infarction size and ischemia-induced arrhythmias improved in coronary occlusion experiments in animals, with no apparent vasodilatory effect on the coronary vessels

Question 22

Describe the mechanism of respiratory arrest caused by spinal anesthesia

Answer 22

However rare, respiratory arrest associated with spinal anesthesia is often unrelated to phrenic or inspiratory dysfunction but rather to hypoperfusion of the respiratory centers in the brainstem

Question 23

Neuraxial blockade from … disrupts splanchnic sympathetic innervation to the gastrointestinal tract, resulting in a contracted gut and hyperperistalsis. Nausea and vomiting may be associated with neuraxial block in as much as …% of patients and they are primarily related to gastrointestinal hyperperistalsis caused by unopposed parasympathetic (vagal) activity.
… is effective in treating nausea associated with high (T5) subarachnoid anesthesia

Answer 23

T6 to L1

20

Atropine

Question 24

Despite a predictable decrease in renal blood flow accompanying neuraxial blockade, this decrease is of little physiologic importance

T or F

Answer 24

T

Question 25

Absoluto contraindications to neuraxial anesthesia

Answer 25

Some of the most important include patient refusal, localized sepsis, and an allergy to any of the drugs planned for administration. A patient’s inability to maintain stillness during needle puncture, which can expose the neural structures to traumatic injury, as well as raised intracranial pressure, which may theoretically predispose to brainstem herniation, should also be considered absolute contraindications to a neuraxial technique

Question 26

Relative contraindications to a neuraxial anesthesia

Answer 26

Neurologic
1) Myelopathy or Peripheral Neuropathy
Preexisting neurologic deficit can in theory worsen the extent of any injury in this group of patients (so-called double-crush phenomenon). While many reports suggest central neuraxial techniques may be used safely, there is no definitive evidence.

2) Spinal Stenosis
Patients with spinal stenosis appear to be at increased risk of neurologic complications after neuraxial blockade, but the relative contribution of surgical factors and natural history of the spinal pathology itself is unknown

3) Spine Surgery
Previous spine surgery does not predispose patients to an increased risk of neurologic complications after neuraxial blockade. However, depending on postsurgical anatomy and the presence of scar tissue, adhesions, hardware, and/or bone grafts, needle access to the CSF, or epidural space and/or epidural catheter insertion may be challenging or impossible. In addition, the resultant spread of local anesthetic in the CSF or epidural space can be unpredictable and incomplete

4) Multiple Sclerosis
Patients with multiple sclerosis (MS) may be more sensitive to neuraxial local anesthetics and thus exhibit a prolonged duration of motor and sensory blockade; however, any association between neuraxial anesthesia and exacerbation of MS symptoms is not based in evidence. Given that demyelinated fibers may be more prone to the toxic effects of local anesthetics, it is prudent to use a lower dose and concentration of spinal local anesthetic in this group of patients, or else consider epidural rather than spinal anesthesia.

4) Spina Bifida
Spina bifida comprises a wide spectrum of congenital spinal cord malformations. Depending on the severity of the neural tube defect, patients with spina bifida may have a tethered cord and the ligamentum flavum may be absent, thereby increasing the potential for traumatic needle injury to the spinal cord

Cardiac
1) Aortic Stenosis or Fixed Cardiac Output
The unpre- dictable speed and extent to which systemic vascular resistance is reduced after spinal anesthesia may cause many providers to avoid spinal anesthesia in preload- dependent patients and try to prevent a dangerous decrease in coronary perfusion. This concern is borne of theoretic risk and a great deal of caution rather than evidence

2) Hypovolemia
An extension of patients who are preload dependent, hypovolemic patients may exhibit an exaggerated hypotensive response to the vasodilatory effects of neuraxial blockade.

Hematologic
1) Thromboprophylaxis (tabela galeria)

2) Inherited Coagulopathy
The safety of neuraxial techniques in patients with common bleeding diatheses is not well documented. Hemorrhagic complications after neuraxial techniques in patients with known hemophilia, von Willebrand disease, or idiopathic thrombocytopenic purpura appear infrequently when factor levels are more than 0.5 IU/mL for factor VIII, von Willebrand factor, and ristocetin cofactor activity, or when the platelet count is greater than 50000/ml before block performance

Question 27

Describe the Dermatomal Level Required for the following Surgical Procedures

Upper abdominal surgery
Cesarean delivery
Transurethral resection of prostate
Hip surgery
Foot and ankle surgery

Answer 27

Upper abdominal surgery: T4
Cesarean delivery: T4
Transurethral resection of prostate: T10
Hip surgery: T10
Foot and ankle surgery: L2

Question 28

Describe the Factors Affecting Local Anesthetic Distribution and Block Height and classify in More Important, Less Important and Not Important

Answer 28

Drug factors
- More Important: Dose and Baricity
- Less important: Volume, Concentration, Temperature of injection and Viscosity
- Not Important: Additives other than opioids

Patient factors
- More Important: CSF volume, Advanced age e Pregnancy
- Less important: Weight, Height, Spinal anatomy and Intraabdominal pressure
- Not Important: Menopause and Gender

Procedure factors
- More Important: Patient position and Epidural injection post spinal
- Less important: Level of injection (hypobaric more than hyperbaric), Fluid currents, Needle orifice direction, Needle type

Question 29

Describe the spinal level tha need to be block to avoid nociception in the following structures: peritoneum, bladder, and uterus (T10)

Answer 29

peritoneum (T4)
bladder (T10)
uterus (T10)

Question 30

definition of baricity in the contex of neuraxial anesthesia

Answer 30

Baricity is the ratio of the density of a local anesthetic solution to the density of CSF

Question 31

How do the natural curvatures of the vertebral column can help predict local anesthetic spread in patients placed in the horizontal supine position immediately after intrathecal administration?

Answer 31

Hyperbaric local anesthetics injected, while sitting, at the L3-L4 or L4-L5 interspacewill spread with gravity from the height of the lumbar lordosis down toward the trough of the thoracic kyphosis in the horizontal supine position, resulting in a higher level of anesthetic effect than isobaric or hypobaric solutions

Question 32

Describe the relation between antropomorphic measurment, CSF volume and spinal anesthesia

Answer 32

CSF volume does not correlate well with anthropomorphic measurements available clinically other than body weight. In theory,
the increased abdominal mass in obese patients, and possible increased epidural fat, may decrease the CSF volume and therefore increase the spread of local anesthetic and block height. This has indeed been demonstrated using hypobaric solutions, which are characterized by more variable spread anyway, but not hyperbaric solutions

Question 33

Describe the differences in the CSF density between premenopausal e postmenopausal women, men and women, pregnant and non pregnant

Answer 33

The density of CSF is lower in women compared with men, premenopausal compared with postmenopausal women, and pregnant compared with nonpregnant women. Although this may affect relative baricity of local anesthetics, the clinical variation in spread is probably unimportant.

Question 34

How does advanced age affect spinal anesthesia

Answer 34

Advanced age is associated with increased block height. In older patients, CSF volume decreases, whereas its specific gravity increases. Further, the nerve roots appear more sensitive to local anesthetic in the aged population.

Question 35

Intrathecal local anesthetic appears to stop spreading … after injection

Answer 35

20 to 25 minutes

Question 36

Marked changes in patient posture up to two hours after injection do not result in significant changes in the block level

T or F

Answer 36

F

marked changes in patient posture up to two hours after injection can still result in significant changes in the block level, probably because of bulk movement of CSF

Question 37

A “saddle block” where only the sacral nerve roots are anesthetized
can be achieved by …

Answer 37

using a small dose of hyperbaric local anesthetic while the patient remains in the sitting position for up to 30 minutes

Question 38

Injection rate and barbotage (repeated aspiration and reinjection of CSF) of isobaric and hyperbaric solutions have been shown to increase block height

T or F

Answer 38

F

Injection rate and barbotage (repeated aspiration and reinjection of CSF) of isobaric and hyperbaric solutions have not consistently been shown to affect block height

• A slower injection may actually increase spread, and this is perhaps also safer because forceful injection may cause the syringe to disconnect from the needle

Question 39

The injection of local anesthetic or even saline into the epidural space after a spinal anesthetic decreases the block height

T or F

Answer 39

F

The injection of local anesthetic or even saline into the epidural space
after a spinal anesthetic increases the block height

Question 40

Onset time and duration of action of intrathecal administration of 10 - 30 mcg fentanyl

Answer 40

onset time of 10 to 20 minutes and duration of 4 to 6 hours

Question 41

How does intrathecal α2 agonist prolong the duration of sensory and motor blockade?

Answer 41

Clonidine, dexmedetomidine, and epinephrine all act on prejunctional and postjunctional α2 receptors in the dorsal horn of the spinal cord. Activation of
presynaptic receptors reduces neurotransmitter release, whereas postjunctional receptor activation results in hyperpolarization and reduction of pulse transmission

Question 42

Dose, pros and cons of intrathecal clonidine

Answer 42

In doses of 15 to 225 μg, clonidine prolongs the duration of sensory and motor blockade by approximately 1 hour and improves analgesia, reducing morphine consumption by up to 40%.
It appears to cause less urinary retention than morphine but, as with intravenous clonidine administration, spinal clonidine can also cause hypotension. A systematic
review concluded that the hypotension associated with spinal clonidine was not dose-related and that the risk of bradycardia with clonidine was not increased. Sedation
can also occur with spinal clonidine, peaking within 1 to 2 hours and lasting up to 8 hours

Question 43

As little as …of intrathecal administration of dexmedetomidine can prolongmotor and sensory block without hemodynamic compromise

Answer 43

3 μg

Question 44

Intrathecal neostigmine in doses of … μg has analgesic effects after intrathecal administration.

Intrathecal neostigmine has been shown to prolong motor and sensory blockade and reduce postoperative analgesic requirements.

Neostigmine acts by …

It also appears to …

Its benefits, however, are limited by … and is therefore not in widespread use

Answer 44

10 to 50

inhibiting the breakdown of acetylcholine, therefore increasing acetylcholine concentration, which itself is antinociceptive

stimulate the release of nitric oxide in the spinal cord

nausea, vomiting, bradycardia, and, in higher doses, lower extremity weakness,

Question 45

Four Ps of spinal anesthesia technique

Answer 45

preparation, position, projection, and puncture

Question 46

Describe the spinal needles that cut the dura and the ones with a conical, pencil-point tip

Answer 46

Cut the dura: Pitkin and the Quincke-Babcock needle

Pencil-point: Whitacre and Sprotte needles

Question 47

One of the most common organisms responsible for postspinal bacterial
meningitis is …

Answer 47

Streptococcus viridans

Question 48

The intercristal line is the line drawn between the two iliac crests and traditionally corresponds to the level of the … vertebral body or the … interspace, but the reliability of this landmark is questionable as demonstrated by recent
ultrasonography studies

Answer 48

L4

L4-L5

Question 49

Duraing a spinal anesthesia, on passing through the …, there is often a
slight “click” or “pop” sensation

Answer 49

dura

Question 50

After CSF is freely obtained, the dorsum of the anesthesiologist’s nondominant hand steadies the spinal needle against the patient’s back while the syringe containing the therapeutic dose is attached to the needle. CSF is again freely aspirated into the syringe, and the anesthetic dose is injected at a rate of approximately… .
After completion of the injection, … mL of CSF can be aspirated into the syringe and reinjected into the subarachnoid space to reconfirm location and clear the needle of the remaining local anesthetic

Answer 50

0.2 mL/s

0.2

Question 51

Describe the position of the needle in the paramedian technique

Answer 51

The paramedian needle is inserted 1 cm lateral and 1 cm caudad to the caudad edge of the more superior vertebral spinous process. The paramedian needle is inserted approximately 15 degrees off the sagittal plane

Question 52

Describe the Modified Bromage Scale

Answer 52

□ 0: No motor block
□ 1: Inability to raise extended leg; able to move knees and feet
□ 2: Inability to raise extended leg and move knee; able to move feet
□ 3: Complete block of motor limb

Question 53

Ensuring that the level of block using cold or pinprick is … segments
above the expected level of surgical stimulus is commonly considered adequate

Answer 53

two to three

Question 54

Describe the Factors Affecting Epidural Local Anesthetic Distribution and Block Height

Answer 54

Drug factors
- More Important: Volume and Dose
- Less important: Concentration
- Not Important: Additives

Patient factors
- More Important: Advanced age e Pregnancy
- Less important: Weight, Height, Pressure in adjacent body cavities

Procedure factors
- More Important: Level of injectional
- Less important: Patient position
- Not Important: Speed of injection and Needle orifice direction

Question 55

In epidural anesthesi, as a general principle, … mL of solution should be injected
per segment to be blocked

Answer 55

1 to 2

Question 56

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 …% less volume is required in the elderly

Answer 56

40%

Question 57

Describe the possible reasons associated with the small doses required for epidural anesthesia in elderly patients

Answer 57

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.

Question 58

The level of injection is the most important procedurerelated factor that affects epidural block height. In the upper cervical region, spread of injectate is mostly …, in the midthoracic region spread is …, and in the low thoracic region spread is primarily …

After a lumbar epidural, spread is …

Answer 58

caudal

equally cephalad and caudal

cephalad

more cephalad than caudal

Question 59

How can patient positioning affect the height of epidural anesthesia?

Answer 59

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 cephalad
spread in obstetric patients

Question 60

Describe the Onset Times and Analgesic Durations of the following Local Anesthetics Administered Epidurally in 20- to 30-mL Volumes
- 2-Chloroprocaine 3%
- Lidocaine 2%
- Bupivacaine 0,5 - 0,75%
- Ropivacaine 0,75 - 1%
- Levobupivacaine 0,5 - 0,75%

Answer 60

• 2-Chloroprocaine 3%:
  Onset: 10 - 15 min
  Duration: plain 45 - 60min; Epinephrine 60 - 90min
• Lidocaine 2%
  Onset: 15 min
  Duration: plain 80 - 120 min; Epinephrine 120 - 180min
• Bupivacaine 0,5 - 0,75%
  Onset: 20 min
  Duration: plain 165 - 265min; Epinephrine 180 - 240min
• Ropivacaine 0,75 - 1%
  Onset: 15 - 20 min
  Duration: plain 140 - 180min; Epinephrine 150 - 200min
• Levobupivacaine 0,5 - 0,75%
  Onset: 15 - 20 min
  Duration: plain 150 - 225min; Epinephrine 150 - 240min

Question 61

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

This was thought to be secondary to the … that … and caused a …

In addition, chloroprocaine can antagonize the effects of epidural …
This may be a result of … by either the chloroprocaine or a metabolite

Answer 61

deep, aching, burning lumbar back pain

ethylenediaminetetraacetic acid

chelated calcium

localized hypocalcemia

morphine

opioid receptor antagonism

Question 62

Lidocain use in lumbar epidural anesthesia is commonly associated with TNS symptons

T or F

Answer 62

F

Unlike spinal anesthesia, TNS are not commonly associated with epidural
lidocaine

Question 63

Ropivacaine is available in 0.2%, 0.5%, 0.75%, and 1.0% preservative-free preparations. For surgical anesthesia, …% is used, whereas …%
is used for analgesia.

Answer 63

0.5% to 1.0

0.1% to 0.2

Question 64

Epidural morphine is administered as a bolus of …, with an onset time of … minutes and duration of up to … hours. The optimal dose that balances analgesia
while minimizing side effects is … mg.

Alternatively, morphine can be administered continuously in doses of … through an epidural catheter

Answer 64

1 to 5 mg

30 to 60

24

2.5 to 3.75

0.1 to 0.4 mg/h

Question 65

Epidural clonidine can prolong sensory block to a greater extent than motor block. The mechanism appears to be mediated by … rather than an …

The addition of clonidine reduces both epidural local anesthetic and opioid requirements. Other benefits of clonidine may include a …

Epidural clonidine does have a variety of side effects including… . The cardiovascular effects may be greatest when clonidine is administered in the epidural space at the … level.

Answer 65

the opening of potassium channels and subsequent membrane hyperpolarization

α2-agonist effect

reduced immune stress and cytokine response

hypotension, bradycardia, dry mouth, and sedation

thoracic

Question 66

Several investigators have found that multiple-orifice epidural 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 dura perforation

T or F

Answer 66

F

Several investigators have found that multiple-orifice epidural 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

Question 67

Describe the suggested epidural insertion sites for the following common surgical procedures:
Hip surgery
Lower extremity
Obstetric analgesia
Colectomy, anterior resection
Upper abdominal surgery
Thoracic

Answer 67

Hip surgery / Lower extremity / Obstetric analgesia: Lumbar L2-L5

Colectomy, anterior resection / Upper abdominal surgery: Lower thoracic, T6-T8 (Spread more cranial than caudal)

Thoracic: T2-T6 (Midpoint of surgical incision)

Question 68

Describe important surface landmarks to identify the intervertebral space

Answer 68

• Intercristal line (corresponding to the L4-L5 interspace);
• Inferior angle of the scapula (corresponding to the T7 vertebral body);
• Root of the scapular spine (T3);
• Vertebra prominens (C7).

Question 69

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 false loss-of-resistance, possibly because of … .
Such false-positive rates can be as high as …%

Answer 69

defects in the interspinous ligament

30

Question 70

What is the diference in the loss of resistance technique for epidural anesthesia between air and saline as noncompressible media?

Answer 70

Air involves intermittent gentle pressure applied to the bulb of the syringe and saline involves constant gentle pressure

Question 71

Pros and cons between usign air or saline in the loss of resistance technique for epidural anesthesia

Answer 71

There are reports that air is less reliable in identifying the epidural space, results in a higher chance of incomplete block, and may also cause both pneumocephalus (which can result in headaches) and venous air embolism in rare cases.

If air is chosen, the amount of air injected after loss-of-resistance should therefore be minimized.

Evidence suggests that there is no difference in adverse outcome in the obstetric population when air or saline is used.

Another meta-analysis found that fluid inserted through the epidural needle before catheter insertion reduces the risk of epidural vein cannulation by the catheter.

One proposed disadvantage of using saline is that it may be more difficult to readily detect an accidental dural puncture

Question 72

When a lumbar midline approach is used, the depth from skin to the ligamentum flavum commonly reaches … cm, with the depth in most (80%) patients being between … cm

Answer 72

4

3.5 and 6

Question 73

Describe the Tsui test

Answer 73

The Tsui test may be used to confirm the epidural catheter position.
This test stimulates the spinal nerve roots with a low electrical current conducted through normal saline in the epidural space and an electrically conducting catheter. A metalcontaining 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 74

Describe the paramedian approach for epidural anesthesia

Answer 74

The paramedian 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.

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 75

Describe the Taylor approach for epidural anesthesia

Answer 75

The Taylor approach is a 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. 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 76

How to do the test dose in the epidural anesthesia?

Answer 76

A small volume of lidocaine 1.5% with epinephrine is traditionally used for this purpose. 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, using endpoints of an increase in systolic blood pressure more than 15 mm Hg or an increase in heart rate more than 10 beats/min

Question 77

Pros of combined spinal-epidural aneesthesia

Answer 77

• More rapid onset of spinal block compared with epidural anesthesia allows the operative procedure to begin earlier, whereas the epidural catheter still provides both effective postoperative analgesia and allows anesthesia to be extended as the spinal resolves;
• Possibility of using a low dose of intrathecal local anesthetic, with the knowledge that the epidural catheter may be used to extend the block if necessary (The addition of either local anesthetic or saline alone to the epidural space via the catheter compresses the dural sac and increases the block height. This latter technique is called
  epidural volume extension (EVE) and has been shown in cesarean delivery to provide a comparable sensory block to larger doses of intrathecal local anesthetic (with no EVE) but with significantly faster motor recovery);

Question 78

Describe the combined spinal-epidural anesthesia technique

Answer 78

The CSE technique most commonly involves placement of the epidural needle first, followed by either a “needle through needle” technique to reach the subarachnoid space or an altogether separate spinal needle insertion at either the same or different interspace.

Some but not all studies have demonstrated greater success and lower failure rates with the separate needle insertion technique. This method has the potential advantage of being able to confirm that the epidural catheter is functional before spinal anesthesia is administered, which, although it is time consuming, may be advantageous if the epidural catheter is to be relied upon for anesthesia when the spinal component resolves

Question 79

Resume of the occurence of paraplegia after a neuraxial anesthesia

Answer 79

The frequency of paraplegia related to neuraxial anesthesia is reported to be approximately and the mechanism of such a severe injury is likely multifactorial and difficult to identify for certain.

Although injury resulting from direct needle trauma to the spinal cord may be self-evident, historical cases highlight the fundamental danger that accompanies the injection of a foreign substance into the CSF.

Profound hypotension or ischemia of the spinal cord can be important contributing factors in cases of paraplegia associated with neuraxial anesthesia

Question 80

Describe the Anterior spinal artery syndrome

Answer 80

Anterior spinal artery syndrome, characterized by painless loss of motor and sensory function, is associated with anterior cord ischemia or infarction with sparing of proprioception, which is carried by the posterior column. The anterior cord is believed to be especially vulnerable to ischemic insult because of its single and tenuous source of arterial blood supply (the artery of Adamkiewicz). Ischemia caused by any one or a combination of profound hypotension, mechanical obstruction, vasculopathy, or hemorrhage can contribute to irreversible anterior cord damage

Question 81

Cauda Equina Syndrome in the contex of neuraxial anesthesia

Answer 81

The rate of cauda equina syndrome is approximately 0.1/10,000 and invariably results in permanent neurologic deficit.

The lumbosacral roots of the spinal cord may be particularly vulnerable to direct exposure to large doses of local anesthetic, whether it is administered as a single injection of relatively highly concentrated local anesthetic (e.g., 5% lidocaine) or prolonged exposure to a local anesthetic through a continuous catheter.

Another risk factor for cauda equine syndrome may be spinal stenosis wherein local anesthetic distribution may be limited, thus exposing the cauda equine to higher concentrations of local anesthetic.

The etiology of CES is diverse, including but not limited to direct or indirect trauma after several puncture attempts, infection, ischemia or compression of spinal cord or nerve roots by a hematoma.

The syndrome is characterized by proximal weakness of LE, loss of sensitivity, lower back pain, and sciatica that can lead to different grades of sexual dysfunction and intestinal and/or vesical sphincter dysfunction, perineal numbness, and even paraplegias

Question 82

Many risk factors have been associated with the development of an epidural hematoma, including …

Answer 82

difficult or traumatic needle or catheter insertion, coagulopathy, elderly age, and female gender

Question 83

Incidence of epidural hematoma in anesthesia

Answer 83

The United Kingdom NHS audit arguably provides the most accurate rates of neurologic complications associated with neuraxial anesthesia in contemporary practice. This unique prospective nationwide audit found five cases of epidural hematoma among 707,455 neuraxial techniques (0.07/10,000), all of which occurred among 97,925 perioperative epidural techniques (0.5/10,000)
performed over the course of 1 year

Question 84

Epidural hematoma signs and symptoms

Answer 84

The patient may present with a severe, localized, constant back pain with or without a radicular component that may mimic disk herniation.
Associated symptoms may include weakness, numbness, and urinary or fecal incontinence.
Return of sensory or motor deficit several hours after spinal or epidural block has worn off (with or without back pain) is highly pathognomonic and should be considered and treated as spinal or epidural hematoma until proven otherwise.
Neurologic recovery after conservative management has been reported in patients with back pain and leg weakness without paralysis.
Neurologic recovery can occur if surgery and decompression is performed within 36 hours of a complete motor deficit and within 48 hours of a partial deficit.

Question 85

There are two possible explanations for the cause of the headache, neither of which has ever been proven. Describe them

Answer 85

First, the loss of CSF through the dura is proposed to cause traction on pain-sensitive intracranial structures as the brain loses support and sags.

Alternatively, the loss of CSF initiates compensatory yet painful intracerebral vasodilation to offset the reduction in intracranial pressure

Question 86

Clinical features of post-dural puncture headache

Answer 86

The characteristic feature of a post–dural puncture headache is a frontal or occipital headache that worsens with the upright or seated posture and is relieved by lying supine.
Associated symptoms can include nausea, vomiting, neck pain, dizziness, tinnitus, diplopia, hearing loss, cortical blindness, cranial nerve palsies, and even seizures.
In more than 90% of cases, the onset of characteristic post–dural puncture headache symptoms will begin within 3 days of the procedure, and 66% start within the first 48 hours.
Spontaneous resolution usually occurs within 7 days in the majority (72%) of cases, whereas 87% of cases resolve by 6 months

Question 87

Orienting a needle bevel parallel with the axis of the spine, such that the longitudinal fibers of the dura would more likely be separated than cut, doesn´t results in a lower incidence of postspinal puncture headache
T or F

Answer 87

F

Orienting a needle bevel parallel with the axis of the spine, such
that the longitudinal fibers of the dura would more likely be separated than cut, RESULTS in a lower incidence of postspinal
puncture headache

Question 88

Factors That Can Increase the Incidence of Headache After Spinal Puncture

Answer 88

□ Age: Younger, more frequent
□ Sex: Females > males
□ Needle size: Larger > smaller
□ Needle bevel: Less when the needle bevel is placed in the long axis of the neuraxis
□ Pregnancy: More when pregnant
□ Dural punctures: More with multiple punctures

Question 89

Conservative management for post–dural puncture headache includes supine positioning, hydration, caffeine, and oral
analgesics. Sumatriptan has also been used with varying effect but is not without side effects

Answer 89

Conservative management for post–dural puncture headache includes supine positioning, hydration, caffeine, and oral
analgesics.
Sumatriptan has also been used with varying effect but is not without side effects

Question 90

One multinational, multicenter, randomized, blinded trial suggested that … mL of blood is a reasonable starting target volume.

A second epidural blood patch may be performed … hours after the first in the case of ineffective or incomplete relief of symptoms

Answer 90

20

24 to 48

Question 91

Clinical features of transient neurologic symptons after neuraxial anesthesia

Answer 91

TNS, previously known as transient radicular irritation, are usually characterized by bilateral or unilateral pain in the buttocks radiating to the legs or, less commonly, isolated buttock or leg pain. Symptoms occur within 24 hours of the resolution of an otherwise uneventful spinal anesthetic and are not associated with any neurologic deficits or laboratory abnormalities. The pain can range from mild to severe and typically resolves spontaneously in 1 week or less

Question 92

TNS occur more commonly in patients who are placed in the … position for surgery

Answer 92

lithotomy

Question 93

TNS is not related to the concentration of lidocaine, the addition of dextrose or epinephrine, or solution osmolarity

T or F

Answer 93

T

Question 94

The type of needle can influence the likelihood of TNS, with the rate reduced by a … needle, possibly because … needles increase the risk of injecting anesthetic caudally in the thecal sac

Answer 94

double-orifice

single-orifice

Question 95

In the setting of spinal anesthesia, hypotension (defined as systolic blood pressure <90 mm Hg) is more likely to occur with a variety of factors including peak block height greater than or equal to T5, age older than or equal to 40 years, baseline systolic blood pressure less than 120 mm Hg, combined spinal and general anesthesia, spinal puncture at or above the L2-L3 interspace, and the addition of phenylephrine to the local anesthetic

T or F

Answer 95

T

Question 96

Factors that may increase the likelihood of exaggerated bradycardia after spinal anesthesia (40–50 beats/min) include …

Answer 96

baseline heart rate less than 60 beats/min, age younger than 37 years, male gender, nonemergency status, β-adrenergic blockade, and prolonged case duration

Question 97

Neuraxial opioids are commonly added to local anesthetic solutions to improve the quality and duration of neuraxial anesthesia and analgesia. The risk of respiratory depression associated with neuraxial opioids is dose dependent, with a reported frequency that approaches 3% after the administration of 0.8 mg of intrathecal morphine. Respiratory depression may stem from

Answer 97

rostral spread of opioids within the CSF to the chemosensitive
respiratory centers in the brainstem

Question 98

Bacterial meningitis and epidural abscess are rare, but potentially catastrophic, infectious complications of all neuraxial techniques. Which bacteria are more associated whit infections after neuraxial anesthesia?

Answer 98

Staphylococcal infections arising from the patient’s skin are one of the most common epidural-related infections, whereas oral bacteria such as Streptococcus viridans are a common cause of infection after spinal anesthesia, underscoring the need for the clinician to wear a facemask when performing neuraxial procedures

Question 99

Factors associated with developing nausea or vomiting after spinal anesthesia include …

Answer 99

the addition of phenylephrine or epinephrine to the local anesthetic, peak block height greater than or equal to T5, baseline heart rate greater than 60 beats/min use of procaine, history of motion sickness, and the development of hypotension during spinal anesthesia.

Question 100

Among the opioids commonly added to intrathecal or epidural local anesthetics, … administration has the most frequent risk of nausea or vomiting, whereas … carry the least frequent risk

Answer 100

morphine

fentanyl and sufentanil

Question 101

Urinary retention can occur in as much as … of patients after neuraxial anesthesia. Local anesthetic blockade of the … nerve roots inhibits urinary function as the …

… can further complicate urinary function by suppressing detrusor contractility and reducing the sensation of urge

Answer 101

one third

S2, S3, and S4

detrusor muscle is weakened

Neuraxial opioids

Question 102

The rate of shivering related to neuraxial anesthesia is as frequent as … . The intensity of shivering is likely related more to … anesthesia than …

Although there are multiple possible explanations for the difference in shivering intensity, this observation may simply be related to ….

Another explanation may be the …

Answer 102

55%

epidural

spinal

the inability to shiver because of the profound motor block associated with spinal anesthesia compared with epidural
techniques

relatively cold temperature of the epidural injectate, which can affect the thermosensitive basal sinuses

Question 103

The addition of neuraxial opioids, specifically …, reduces the likelihood of shivering.

Answer 103

fentanyl and meperidine

Question 104

In obstetrics, the likelihood of intravascular injection is decreased by …

Answer 104

placing the patient in the lateral (as opposed to the sitting) position during needle and catheter insertion, administering fluid through the epidural needle before catheter insertion, using a single-orifice type rather than a multiorifice catheter or a wire-embedded polyurethane type compared with polyamide epidural catheter, and advancing the catheter less than 6 cm into the epidural space

Question 105

The epidural epinephrine test dose can be unreliable in …

Answer 105

patients receiving β-adrenergic blockers or if the test dose is administered during general anesthesia

Question 106

For cardiac surgery, meta-analyses have shown … in patients who received combined intraoperative general anesthesia and

Answer 106

a reduced risk of mortality and myocardial infarction (composite endpoint); a reduced risk for acute renal failure, pulmonary complications, and supraventricular arrhythmia; and reduced duration of postoperative controlled ventilation

Question 107

For major thoracic and abdominal surgery, thoracic epidural analgesia can reduce …

Answer 107

mortality, along with reductions in respiratory complications and opioid consumption, and improvements in cough and time to ambulation

Question 108

For bilateral total knee arthroplasty, neuraxial anesthesia decreases the rate of …

Answer 108

blood transfusion