Chapter 17 Spinal And Epidural Anesthesia

Front 1

Spinal anesthesia is accomplished by

Back 1

injecting local anesthetic solution into the cerebrospinal fluid (CSF) contained within the subarachnoid (intrathecal) space.

Front 2

epidural anesthesia is achieved by injection of local anesthetic solution into the

Back 2

space that lies within the vertebral canal but outside or superficial to the dural sac.

Front 3

Caudal anesthesia represents a special type of epidural anesthesia in which local anesthetic solution is injected into the

Back 3

caudal epidural space through a needle introduced through the sacral hiatus.

Front 4

subarachnoid injections are limited to

Back 4

the lumbar region below the termination of the spinal cord.

Front 5

produces more intense sensory and motor block.

Back 5

spinal anesthesia

Front 6

Advantages of epidural anesthesia include a decreased risk for post-dural puncture headache (assuming a negligible incidence of inadvertent dural puncture), a lower incidence of systemic hypotension, the ability to produce segmental sensory block, and greater control over the intensity of sensory anesthesia and motor block achieved by adjustment of the local anesthetic concentration.,allowing titration of the block to the duration of surgery.

Back 6

1. decreased risk for post-dural puncture headache
2. a lower incidence of systemic hypotension
3. the ability to produce segmental sensory block,
4. greater control over the intensity of sensory anesthesia and motor block achieved by adjustment of the local anesthetic concentration
5. allowing titration of the block to the duration of surgery.

Front 7

Skeletal muscle relaxation is profound in the presence of neuraxial anesthesia and thus obviates the need for______________ .

Back 7

neuromuscular blocking drugs

Front 8

SACRAL HIATUS

Back 8

The sacrum is a large curved wedge-shaped bone whose dorsal surface is convex and gives rise to the powerful 1 · sacrospinalis muscle. The opening between the unfused lamina of the fourth and fifth sacral vertebrae is called the sacral hiatus.

Front 9

Surface landmarks are used to identify specific spinal interspaces (Fig. 17 -6).4 The most important of these landmarks is a line drawn between the iliac crests. This line generally traverses

Back 9

the body of the L4 vertebra and is the principal landmark used to determine the level for insertion of a needle intended to produce spinal anesthesia

Front 10

the C7 spinous process can be appreciated as

Back 10

a bony knob at the lower end of the neck.

Front 11

the terminal portion of the 12th rib intersects the

Back 11

L2 vertebral body,

Front 12

adjacent vertebral bodies are joined by .

Back 12

anterior and posterior spinal ligaments, the latter forming the anterior border of the vertebral canal

Front 13

The supraspinous ligament runs

Back 13

superficially along the spinous processes, which makes it the first ligament that a needle I will traverse when using a midline approach to the vertebral canal.

Front 14

The ligamentum flavum is composed of

Back 14

thick plates of elastic tissue that connect the lamina of adjacent vertebrae.

Front 15

the spinal core generally terminates around

Back 15

the third lumbar vertebra at birth and at the lower border of the first lumbar vertebra in adults.

Front 16

Meninges outer layer,

Back 16

DURA MATER

Front 17

Closely adherent to the inner surface of the dura lies the

Back 17

arachnoid membrane.

Front 18

serves as the major pharmacologic barrier preventing movement of drug from the epidural to the subarachnoid space.

Back 18

ARACHNOID MEMBRANE

Front 19

The innermost layer of the spinal meninges

Back 19

PIA

Front 20

spinal cord tapers to form the

Back 20

conus medullaris,

Front 21

# pairs of spinal nerves

Back 21

31

Front 22

onset of epidural block occurs by local anesthetics thus occurs by

Back 22

blockade of sodium ion conductance in this region.

Front 23

The area of skin innervated by each spinal nerve is called

Back 23

a dermatome

Front 24

The epidural space lies between the

Back 24

dura and the wall of the vertebral canal, an irregular column of fat, lymphatics, and blood vessels

Front 25

The blood supply of the spinal cord arises from

Back 25

a single anterior and two paired posterior spinal arteries

Front 26

Spinal anesthesia is generally used for

Back 26

surgical procedures involving the lower abdominal area, perineum, and lower extremities.

Front 27

4 Absolute contraindications to neuraxial anesthetic techniques include

Back 27

patient refusal,
infection at the site of planned needle puncture,
elevated intracranial pressure,
and bleeding diathesis.

Front 28

The distribution of local anesthetic solution in CSF is influenced principally by (I) the baricity of the solution, (2) the contour of the spinal canal, and (3) the position of the patient in the first few minutes after injection of local anesthetic solution into the subarachnoid space.

Back 28

(I) the baricity of the solution,
(2) the contour of the spinal canal, and
(3) the position of the patient in the first few minutes after injection of local anesthetic solution into the subarachnoid space.

Front 29

the duration of spinal anesthesia depends on 2x

Back 29

the drug selected and the presence or absence of a vasoconstrictor

Front 30

Local anesthetic solutions are classified as _________________________ based on their density relative to the density of CSF.

Back 30

hypobaric, isobaric, and hyperbaric

Front 31

predicts the direction that local anesthetic solution will move after injection into CSF.

Back 31

Baricity

Front 32

The most commonly selected local anesthetic solutions for spinal anesthesia are

advantage is

Back 32

hyperbaric (achieved by the addition of glucose [dextrose]), and their principal advantage is the ability to achieve greater cephalad spread of anesthesia.

Front 33

2 Commercially available hyperbaric local anesthetic solunons include

Back 33

0.75% bupivacaine with 8.25% glucose and 5% lidocaine with 7.5% glucose.

Front 34

a potential advantage of isobaric local anesthetic solutions is a more

Back 34

profound motor block and more prolonged duration of action than that achieved with equivalent hyperbaric local anesthetic solutions

Front 35

_________ are frequently added to local anesthetic solutions to increase the duration of spinal anesthesia.

Back 35

Vasoconstrictors

Front 36

Vasoconstrictors are frequently added to local anesthetic solutions to increase the duration of spinal anesthesia. This is most commonly achieved by the addition of

Back 36

This is most commonly achieved by the addition of epinephrine (0.1 to 0.2 mg, which is 0.1 to 0.2 mL of a 1:1000 ' solution) or phenylephrine (2 to 5 mg, which is 0.2 to : 0.5 mL of a 1% solution).

Front 37

bs been the most popular short-acting local anesthetic for spinal anesthesia.

Back 37

Lidocaine

Front 38

Lidocaine duration of action

Back 38

of 60 to 90 minutes

Front 39

2 local anesthetics most frequently used for long-duration spinal anesthesia.

Back 39

Bupivacaine and tetracaine

Front 40

Within _____ seconds after subarachnoid injection of local anesthetic solutions, an attempt should be made to determine the developing level of spinal anesthesia. '

Back 40

30 to 60

Front 41

Sensory level Necessary for Surgical Procedures

Hemorrhoidectomy

Back 41

s2-s5

Front 42

Sensory level Necessary for Surgical Procedures

Foot surgery

Back 42

L2-L3 (knee)

Front 43

Sensory level Necessary for Surgical Procedures

Lower extremity

Back 43

Ll-L3 (inguinal ligament)

Front 44

Sensory level Necessary for Surgical Procedures

Hip surgery
TransurethraL resection of I the prostate
Vaginal delivery

Back 44

T10 (umbilicus)

Front 45

Sensory level Necessary for Surgical Procedures

Lower abdominal surgery .
Appendectomy

Back 45

T6-T7 (xiphoid process)

Front 46

Sensory level Necessary for Surgical Procedures

Upper abdominal surgery Cesarean section

Back 46

T4 (nipple)

Front 47

The ____________ block typically exceeds the____________by two dermatomes.

Back 47

sympathetic nervous system

somatic sensory block

Front 48

Hypotension (systolic blood pressure <90 rum Hg) is estimated to occur in about ____________ of patients receiving spinal anesthesia.

Back 48

a third

Front 49

The heart rate does not change signific.antly in most patients during spinal anesthesia. However, in an estimated _______ of patients, significant bradycardia occurs.

Speculated mechanisms for this are 2X

Back 49

10% to 15%

bradycardia include block of cardioaccelerator fibers originating from Tl through T4 and decreased venous return (Bezold-Jarisch reflex).

Front 50

BRADYCARDIA AN) ASYSTOLE

This catastrophic event can probably be prevented through

Back 50

maintenance of preload and reversal of bradycardia

aggressive stepwise escalation of treatment (ephedrine, 5 to 50 mg IV; atropine, 0.4 to 1.0 mg IV; epinephrine, 0.05 to 0.25 mg IV), whereas the development of profound : bradycardia or asystole mandates immediate treatment with full resuscitation doses of epinephrine (1.0 mg IV)

Front 51

Postdural puncture headache is a direct consequence of

Back 51

the puncture hole in the dura, which results in loss of CSF at a rate exceeding production.

Front 52

The pain associated with postdural puncture headache generally begins

Back 52

12 to 48 hours after transgression of the it dura, but it can occur immediately and has been reported to occur up to several months after the event.

Front 53

The characteristic feature of post-dural puncture headache is its

Back 53

postural component: it appears or intensifies with sitting or standing and is partially or completely relieved by recumbency.

Front 54

Initial treatment of post-dural puncture headache is usually conservative and consists of

Back 54

bed rest, fluids, analgesics, and possibly caffeine (500 mg IV).

More definitively, a blood patch can be perfonned, in which 15 to 20 mL of the patient's blood, aseptically obtained, is injected into s the epidural space.

Front 55

Total spinal anesthesia is the term applied to

Back 55

excessive sensory and motor anesthesia associated with loss of consciousness ..

Front 56

LOSS-OF-RESISTANCE TECHNIQUE

Back 56

With the loss-of-resistance technique, a syringe containing saline, air, or both is attached to the needle, and the needle is slowly advanced while assessing resistance to injection
f the needle is properly seated in the ligamentum flavum, it will be difficult to inject the saline or the air bubble, and the plunger of the syringe will "spring back" to its original position.

An abrupt loss of resistance to InjectIon signals passage through the ligamentum flavum and into the epidural space, at which point the contents of the syringe are delivered.

Front 57

HANGING-DROP TECHNIQUE

Back 57

Mth this technique, a small drop of saline is placed at the hub of the epidural needle. As the needle passes through the ligamentum flavum into the epidural space, the saline drop is retracted into the needle by the negative pressure in the epidural space. Interestingly, the hanging-drop technique can be used in the lumbar region despite the lack of negative pressure in 6e lumbar epidural space

Front 58

With the continuous epidural technique,

Back 58

With the continuous epidural technique, a catheter is advanced 3 to 5 cm beyond the tip of the needle posihoned in the epidural space. Further advancement increases the risk that the catheter might enter an epidural vein, exit an intervertebral foramen, or wrap around a nerve root.l

Front 59

2 principal factors affecting the spread of epidural anesthesia

Back 59

are dose (volume times concentration) and site of injection.

Front 60

The duration of epidural anesthesia, as with spinal anesthesia, is principally affected by

Back 60

the choice of local anesthetic and whether a vasoconstrictor drug is added to the local anesthetic solution.

Front 61

why add epinephrine to local

Back 61

The addition of epinephrine (generally 1:200,OOO; 5 llg/mL) to local anesthetic solutions decreases vascular absorption of the local anesthetic from the epidural space, thus maintaining effective anesthetic concentrations at the nerve roots for more prolonged periods.

Front 62

Similar to spinal anesthesia, opioids are often administered with epidural local anesthetic solutions to

Back 62

enhance surgical anesthesia and to provide postoperative pain control.

Front 63

why SODIUM BICARBONATE

Back 63

Local anesthetic effect requires transfer across the nerve membrane. Because local anesthetics are weak bases, they exist largely in the ionic form in commercial preparations. Adding sodium bicarbonate to the solution favors ; the nonionized form of the local anesthetic and promotes j more rapid onset of epidural anesthesia. · Most commonly, 1 mL of 8.4% sodium bicarbonate is added to 10 mL of a solution containing lidocaine or chloroprocaine.

Front 64

The major site of actionoflocal anesthetic solutions placed in the epidural space appears to be the spinal nerve roots, where the dura is relatively thin.

Back 64

the spinal nerve roots, where the dura is relatively thin.

Front 65

As with spinal anesthesia, the most important physiologic alteration produced by an epidural block is

Back 65

sympathetic nervous system block leading to pooling of blood in the large capacitance venous system of the visceral compartment

Front 66

Diaphragm function is unaffected by epidural anesthesia unless

Back 66

unless the motor block rises into the upper cervical nerve roots.

Front 67

When an epidural hematoma is suspected,...

Back 67

urgent performance of magnetIc resonance imaging is needed because recovery of motor function correlates inversely with the time until surgical decompression of the epidural hematoma

Front 68

Combined spinal-epidural anesthesia is a technique in

Back 68

which a spinal anesthetic and an epidural catheter are placed concurrently.