REGIONAL (spinal, epidural, caudal); Ann

152 terms by Twilightintn

Create a new folder

Advertisement Upgrade to remove ads

CRNA Boards Comprehensive flashcards from Valley Sweat Book. This is not Memory Master. Detailed

33 Vertebrae

O 7 cervical
O 12 thoracic
O 5 lumbar
O 5 sacral
O 4 coccygeal
Note: Dorsal is to the left and ventral is to the right in the above drawing

High points - supine

High points = C3 and L3
"High CL
Low TS"

Low points

Low points = T6 and S2
"High CL
Low TS"

Spinal cord extends ?

Extends from foramen magnum to lumbar level one (L,) in the adult (42-45 cm) and to L₃ in the newborn

When does the spinal begin to move up?

20-24 months

Where does the cord terminate?

Cord terminates at conus medullaris and the filum terminale
extends down and anchors in the lower
sacral region

How many spinal nerves?

Thirty one pairs of spinal nerves

What is the nerve group called in the lower dural sac?

Cauda equina (horses tail) is the nerve group in lower dural sac

Layers of the spinal cord:
SSSILEA

1. Supraspinous ligament
-Strong fibrous cord
-Sacrum to C7
-Thickest and broadest in lumbar region (like Burlap)
2. Interspinous ligament (like cotton)
-Thin membranous ligament
-Thickest and broadest in lumbar region - Full length of column
3. Ligamentum Flavum (yellow ligament)
-Short segments between spinous processes
4. Epidural space (potential space)
-Space that surrounds the spinal meninges
- Extends from foramen magnum to sacral hiatus
5. Spinal meninges( DURA)
(Dura mater)
-Outermost, tough, fibrous tube of fibers; runs longitudinally
-Extends from foramen magnum to S2_3 vertebrae
6. Arachnoid mater
-Middle layer
-Delicate, nonvascular
-Ends at S2
7. subarachnoid space (CSF here)
8. Pia
-Delicate, ( highly vascular)
CSF is contained between the pia and the arachnoid maters in the subarachnoid space.
Arachnoid space = SAB

Which ligament binds the epidural space posteriorly?

Ligamentum Flavum

Epidural space is widest and narrowest at which spaces?

O Widest at level L2 (5-6 mm)
O Narrowest at level C5 (1.0 - 1.5 mm)

Name the space between the arachnoid and pia layers?

Subarachnoid space lies between the arachnoid and pia mater; this is where CSF is found. It is site of SAB.

What protects the spinal cord?

The pia mater; the arachnoid mater and the CSF

What is the medium for drugs during spinal anesthesia?

The pia mater; the arachnoid mater and the CSF

The epidural space is a potential space that is bound by the ____ and the _______.

The dura and the ligamentum flavum

Blood supply to the spinal cord cord and nerve roots is derived from ?

Blood supply to the spinal cord and nerve roots is derived from a single anterior spinal artery and paired posterior spinal arteries.

The principle site of action for neuraxial blockade is the ______.

The principle site of action for neuraxial blockade is the nerve root.

Sensory level of block is assessed by _________

pinprick;

The level of sympathectomy is assessed by ___________.

The level of sympathectomy is assessed by temperature.

Vasoconstrictors do what to spinal block ?

Prolong duration of spinal block
1. decrease surface area
2. decrease rate of elimination of drug (absorbtion)
3. increases the duration of action.

Factors with proven effects on distribution of spinal :

Site of injection
Anatomical shape of spinal column
Patient height
Angulation of needle
Volume of CSF (e.g., pregnancy) Characteristics of local anesthetic
■ Density
■ Specific gravity
■ Baracity
Dose
Volume of local anesthetic
Position of patient during injection
Position of patient after injection

Where is the Uptake of local anesthetic the greatest in a spinal.

Uptake of local anesthetic is greatest where the concentration of the local anesthetic is the greatest

What is the mechanism for uptake in a spinal?

Usually uptake occurs by diffusion down a concentration gradient

What determines the duration of spinal anesthesia?

Rate of elimination determines the duration of spinal anesthesia

How does elimination of local anesthetic occur?

Elimination is by vascular absorption via subarachnoid and epidural blood vessels

What other things affect the rate of elimination for local anesthetics?

Lipid solubility - the more the local anesthetic is bound to lipids, the less chance there is for vascular absorption; i.e., the local anesthetic, if bound to lipids, is not as susceptible to be removed and eimi-nated.
O Decreases in spinal cord blood flow will decrease the rate of elimination; i.e., will prolong the duration of spinal anesthesia
O Vasoconstriction causes decreased rate of elimination.

How does Lipid solubility affect the rate of elimination?

- the more the local anesthetic is bound to lipids, the less chance there is for vascular absorption; i.e., the local anesthetic, if bound to lipids, is not as susceptible to be removed and eimi-nated.

How does Vasoconstriction affect rate of elimination? of local anesthetics

O Vasoconstriction causes decreased rate of elimination.

Cardiovascular Effects of Sympathetic Blockade

Although sympathetic preganglionic neurons send signals to smooth muscle of both arteries and
veins, the predominant action of sympathetic blockade due to local anesthetics is venodilation. Ven¬
odilation reduces venous return, stroke volume, cardiac output and blood pressure.

What happens if If the sympathetic outflow from Tl to T4 is blocked by local anesthetics.

Bradycardia
If the sympathetic outflow from Tl to T4 is blocked by local anesthetic, unopposed vagal stimulation will produce bradycardia.
Bradycardia is associated not only with blockade of cardioaccelerator fibers, but also with decreased venous return.
With a decrease in venous return and a corresponding reduction in right atrial filling, the frequency of action potentials from stretch receptors to the right atrium and
great veins is diminished, which leads to a reflex decrease in heart rate.

When will you see bradycardia with spinal?

In neonates and elderly
Block T1 - T4;
Decrease stretch; decrease atrial filling;
Will see decrease in HR in elderly and neonates;
Can not compensate;
We will increase our heart rate but they can not.

What is the best means for treating hypotension during spinal anesthesia ?

The best means for treating hypotension during spinal anesthesia is physiologic, not pharmacologic
Give Fluids if dry.
Give volume first then ephedrine.

If pt is dry how would you tx hypotension?
If pt is normovolemic, how do you treat BP.

give fluids - (balanced salt solutions that do not contain glucose)
give ephedrine

Why no glucose?

Glucose can act as a diuretic and worsen hypotension.

If HR is normal or elevated, what can you give?
In pts with symtomatic bradycardia what can you give?

Neo
Ephedrine

As the block moves cephalad what happens?

As the block moves cephalad, the abd muscles, followed by the intercostal, becomes paralyzed. If block is at C2-C3, phrenic nerve paralysis and loss of accessory muscles increase potential for hypoxia.

In pts with symtomatic bradycardia, the drug of choice is ___________

Mixed alpha and beta agonist Ephedrine will increase heart rate and peripheral resistance.

• Pulmonary alterations in healthy patients during subarachnoid or epidural block are usually of little clinical significance.

usually of little clinical significance.

Several ventilatory changes during high spinal are possible:

O Decreased functional residual capacity due to paralysis of abdominal muscles.
O Patient's complaints of dyspnea are most often related to loss of chest wall sensation and are not the result of significantly decreased inspiratory capacity.
O Intercostal muscle paralysis interferes with the ability of the patient to cough and clear secretions
Do you ask your pt to cough?
No, drives block up.
O Apnea, if it occurs, is due not only from upward drift of block to C3 it can occur from hypoperfusion of the respiratory centers in the medulla secondary to severe hypotension

At a T-10 level in the elderly what happens?

Increase paralysis, decrease FRC (Their little O2 Tank)

How would you use A pencil-point needle and cut-bevel needle in a spinal pt who is sitting? Lateral position?

In sitting position has dura running parallel to the spinal column. This means the dura runs cephalad to caudal.
A pencil-point needle will "separate" the dura, whereas a cut-bevel needle will need to face either right or left to "separate" (rather than tear) the dura, minimizing trauma to the dura

Lateral position—no change for pencil-point needle; but, the cut-bevel needle will need to be face up or down to minimize trauma to the dura

What is pencil point spinal needle called?

sprott

What is all cutting bevel spinal needle called?

A. Quinke Badcock

What is rounded non-cutting bevel spinal needle called?

Greene

Pts recieving NSAIDs, including aspirin may or may not receive neuraxial anesthesia

Pts recieving NSAIDs, including aspirin may receive neuraxial anesthesia regardless of when they had last dose.

Pts recieving sub-q or minidose heparin may or may not receive neuraxial anesthesia

Pts recieving sub-q or minidose heparin may receive neuraxial anesthesia

Pts receiving intravenous heparin may or may not receive neuraxial anesthesia.

Pts receiving intravenous heparin should not receive neuraxial anesthesia until a normal Ptt can be documented. .

When a central block is used and intraoperative anticoagulation is initiated, when can heparin dosing start?

When a central block is used and intraoperative anticoagulation is initiated, recommended that heparin dosing be held for at least 1 hour after placement.

Indwelling catheters should be removed how long after last heparin dose. After removal when can heparinization occur?

Indwelling catheters should be removed 2-4 hours after last heparin dose and the pts heparin status is known.
After removal, heparinization can occur one hour later.

Pts receiving chronic warfarin (Coumadin) should discontinue medication how many days before surgery?

Pts receiving chronic warfarin (Coumadin) should discontinue medication at least 4 days before surgery.

If a patient receive a dose of Warfarin within 24 hours of surgery, what do you do?

If a patient receive a dose of Warfarin within 24 hours of surgery, INR is checked immediately before scheduled procedure. If INR is less than 1.5 Neuraxial block may be administered.
The catheter should not be removed until the INR is < 1.5

The pt and INR values should be evaluated how often in the pt receiving continuous postoperative epidural analgesia.

The pt and INR values should be evaluated daily in the pt receiving continuous postoperative epidural analgesia.

If a patient receive thrombolytic or fibrinolytic drug therapy what do you do?

Pt should not recieve neuraxial for 10 days. If this tx is anticipated postop then neuraxial should be avoided.

What is the dosing and precautions If a patient is to receive post op Low molecular weight heparin therapy when neuraxial anesthesia is involved?

Twice daily dosing:
-1st dose no earlier than 24 hours regardless of technique and only in the presence of adequate hemostasis.
-Remove indwelling before initiation of LMWH.
-Continuous indwelling may be left overnight and removed the next day, however first dose of heparin should be given two hours after catheter removal.
Once daily dosing:
-First dose 6-8 hours post-op and administer second dose no sooner than 24 hours after first dose
-Indwelling catheters should be removed at a minimum of 10-12 hours after last heparin dose.
-Initiate any subsequent LMWH dosing a minimum of 2 hours after catheter removal.

Spinal Anesthesia Levels (You must know dermatomes)

Dermatome Application
C4 (clavicle) Chest surgery
C7 the most prominent cervical process (This is posterior dermatone)
T4 - T5 (nipples) upper abd. surgery
T6 - T8 (xiphoid) intestinal surgery, appendectomy, gynecologic pelvic surgery, and ureter and renal pelvic surgery
T7 inferior border of scapula (lower "tip) (This is posterior dermatone)
T8 (lower edge ribcage) Abd. surgery
TI0 (umbilicus) transurethral resection, obstetric vaginal delivery, and hip surgery
L1 (inguinal ligament) transurethral resection, if no bladder distension, thigh surgery, lower limb amputation
L2 - L3 (knee and below) foot surgery
L4 Iliac crest (superior) (This is posterior dermatone)
S2 posterior superior illiac spine (This is posterior dermatone)
S2 - S5 (perineal) perineal surgery, hemorrhoidectomy, anal dilation)

Name the 4 posterior dermatones

C7 the most prominent cervical process (This is posterior dermatone)
T7 inferior border of scapula (lower "tip) (This is posterior dermatone)
L4 Iliac crest (superior) (This is posterior dermatone)
S2 posterior superior illiac spine (This is posterior dermatone)

Indications/Advantages of Spinal Anesthesia

Indications/Advantages
O Full stomach
O Anatomic distortions of the upper airway
O TURP
O Obstetrics
O May be simpler and faster
O Decreased postoperative pain
O Continuous infusion

Contraindications to neuraxial anesthesia

Contraindications
O Absolute
■ Infection at site of injection
■ Dermatologic conditions (psoriasis)
■ Septicemia or bacteremia
■ Shock or severe hypovolemia
■ Pre-existing disease involving spinal cord
■ Increased ICP **** Brain tumor
■ Gross abnormality of blood clotting mechanism
■ Patient refusal or psychologically or psychiatrically unsuited
■ Lack of skill or experience of provider
■ Operation taking longer than block will last.
■ Uncertainty about extent or duration of operation
O Relative
■ Major surgical procedure above umbilicus
■ Deformity of spinal column
■ Chronic headache or backache
■ Blood in CSF that does not clear
■ Inability to achieve spinal tap after three attempts
■ Failure to obtain free flow of CSF through the lumbar puncture needle
■ Minor abnormalities of blood clotting; i.e., minidose heparin up to time of surgery
■ preexisting neurological deficit
■ Sepsis
■ uncooperative patient
■ stenotic valvular heart lesion
■ Extreme pt age
■ Mobitz type 1 or 2
■ 3rd degree heatblock without a pacemaker
O Controversial
■prior back surgery at the site of injection
■ inability to communicate with pt.
■ complicated surgery
■ prolonged procedure
■ major blood loss
■ maneuvers that compromise respiration.

Which type tattoos are an absolute contraindication?

acrylic dye (metal in dye)
vegetable dye older than 6 months you can put a needle in it.

What are the indications for Cardiac disease and spinal anesthesia?

Cardiac disease, whether myocardial, valvular or ischemic, is considered a major contraindication to spinal anesthesia if sensory levels of T6 or above are required. Spinal anesthesia is indicated in patients with even severe cardiac disease if only perineal levels of anesthesia are required.

The primary target for spinal is ?

1. Primary nerve root
2. secondary rootlets
3 spinal cord (will get up to the cord)
Spread of local anesthetic when injected into the subarachnoid space. The local anesthetic spreads to tie nerves of the cauda equina and laterally to the nerve rootlets and nerve roots. The local anesthetic may also diffuse into the spinal cord.

Spinal
When you pierce the the __________ you are in the ___________ space. This is where you inject your medicine.

Arachnoid dura,
you are in the sub-archnoid (subdural) space. This is where you inject your medicine

What are Structures needle pass through for subarachnoid block (midline)

• Skin
• Subcutaneous tissue
• Supraspinous ligament
• Interspinous ligament
• Ligamentum flavum
• Epidural space
• Dura mater
• Arachnoid mater or dura
When you pierce the the Arachnoid dura, you are in the sub-archnoid (sub-dural) space. This is where you inject your medicine
"SSSILEA"
skin
subq
supraspinious lig
Interspinous lig
epidural space
arachnoid mater

Lateral approach for block will not pass through which two structures?

O Supraspinous ligament
O Interspinous ligament

What is the last anatomy for spinal?

Arachnoid dura

What is the last anatomy for epidural?

• Ligamentum flavum

What is neuraxial anesthesia

a spinal, an epidural or a caudal block

The principl site of action for neraxial blocks is?

nerve root

Spinal infections-
etiology ?
predisposing factors?
Classic symptoms?
Infectous agents?

1. infections
Etiology:
----body's physiologic protective mechanism disrupted
----needle deposits of infectious or noxious agents
----sterile technique broken
----psoriasis, underlying sepsis, diabetes, steroid therapy, preexisting condition (HIV), immunological compromise

Predisposing factors to infection:
----advanced age
----diabetes,
----alchoholism,
----cancer,
----aids

Classic symptoms:
----high fever,
----nuchal rigidity
severe headache

Infectous agents:
alpha hemolytic streptococci is commonly seen in spinal menigitis
staphylococcus aureus is most common causative organism in epidural abscess
and iatrogenic methicillin-resistant S Aureus is a growing concern.

Infectous agents of spinals

Alpha hemolytic streptococci is commonly seen in spinal meningitis
Staphylococcus aureus is most common causative organism in epidural abscess
and iatrogenic methicillin-resistant S Aureus is a growing concern.

______________ (organism) is commonly seen in spinal meningitis

Alpha hemolytic streptococci is commonly seen in spinal meningitis

____________ is most common causative organism in epidural abscess and ____________ is a growing concern.

Staphylococcus aureus is most common causative organism in epidural abscess
and iatrogenic methicillin-resistant S Aureus is a growing concern.

Complications of spinals:

1. Respiratory system (note nausea and vomiting should be identified as signs of central hypoxia until proven otherwise.)
2. Cardiovascular system
3. Failure of block: due to patient movement or needle movement
4. Backache: most common complication. Stretching of muscles and ligaments of the back beyond their normal range.
5. Headache: second most common complication

What is the second most common complication with a spinal?

Headache: second most common complication
a. frequency 0.2%-24%
b. highest incidence is in obstetrics
c. occurs within several hours, but usually in the first or second day post-puncture.
d. headache is bifrontal and occipital, often involving head, neck, and shoulders.
e. aggravated in upright position, and with coughing or straining.
f. signs and symptoms include nausea and loss of appetite, photophobia, changes in auditory acuity, tinnitus, depression, feel miserable, tearful, bed-ridden, dependent, diplopia and cranial nerve palsies.
Most common pathophysiology is loss of CSF through the puncture site with resultant intracranial tension on meningeal vessels and nerves
i.e. caused by a decrease in the amount of CSF in the subarachnoid space. This decrease in CSF causes the medulla and brainstem to drop into the foramen magnum, stretching the meninges, vessels and nerves, leading to a headache. An additional complication of decreased CSF volumes is cranial nerve palsy which leads to decreased blood supply to the nerves.
Blood patch of 10-30 cc of aseptically-drawn blood. If patient is volume-depleted, it is desirable to infuse 1000 cc IV.
i. first blood patch injection resolves 89-95% of headaches; may repeat in 24 hours;
Touy needle; place first. two people.
ii. reported complications:
□ backache: 35% J D
□ neckache: 0.9%
□ temperature elevation: 5%
□ radicular pain

What is most common complication of a spinal?

Backache: most common complication. Stretching of muscles and ligaments of the back beyond their normal range.

What is 2nd most common complication of a spinal?

Headache: second most common complication

What is most common complication of a spinal in obstetrics ?

In Obstetrics, HA is number 1 complication.

When does a spinal headache occur?
Describe the headache?

Occurs within several hours, but usually in the first or second day post-puncture.
Headache is bifrontal and occipital, often involving head, neck, and shoulders.
Aggravated in upright position, and with coughing or straining.

What are signs and symptoms of spinal H/A?

signs and symptoms include nausea and loss of appetite, photophobia, changes in auditory acuity, tinnitus, depression, feel miserable, tearful, bed-ridden, dependent, diplopia and cranial nerve palsies.

What are complications from a blood patch?
What percentage does the blood patch help?

Reported complications:
□ backache: 35%
□ neckache: 0.9%
□ temperature elevation: 5%
□ radicular pain
First blood patch injection resolves 89-95% of headaches;

How long do you rest after blood patch? What is the volume you inject?

2 hours
15-25cc

If blood patch does not work ?

May repeat then neuro consult.
May give 2 blood patches.

If spinal was done at L 2-3, where do you put blood patch?
What if three holes are there?
Where do you place blood patch?

Same level,
Go in at lowest hole.
epidual space.
Inject slowly. If pt says at 13cc headache is gone, do not stop injection.

How does blood patch work?

The bood in the epidual space puts pressure on the dura mater which puts pressure on the Arachnoid mater and subarachnoid space and by doing so will increase circulating CSF pressure , which lifts the medulla and brainstem off of the foremen magnum.

1. How many vertebrae does this spinal column contain?

33

2. How many cervical, thoracic, lumbar, and sacral vertebrae are there?

C7 T12 L5 S5

3. State the high and low points of the spinal column in the supine position.

C3 L3 T S2

4. Discuss the anatomic relationships of the spinal cord and supraspinous, interspinous, and ligamentum flavum ligaments

...

5. Discuss and describe the epidural space

...

6. Describe the anatomic relationships and functions of the meninges—dura, pia, and arachnoid mater.

...

7. How do vasoconstrictors work?

...

8. Identify the factors that effect agent distribution during spinal anesthesia

...

9. What factor(s) determine duration of spinal anesthesia?

...

10. Describe how/why bradycardia may occur during spinal anesthesia

...

11. How would you treat hypotension during spinal anesthesia?

...

12. Discuss respiratory changes during spinal anesthesia; how/why does apnea occur?

...

13. Compare and contrast how cut-bevel and pencil-point needles should be used, with emphasis on penetrating the dura

...

14. Review and memorize the dermatome levels.

...

15. List the indications for a spinal block.

...

16. List the absolute and relative contraindications for a spinal block

...

17. Identify the target anatomy for both spinal and epidurals

...

18. Identify the structures—in sequential order—that the spinal needle passes through to place a spinal block

...

19. Identify and discuss the complications of a spinal block. Are there any cures? What are the cures?

...

What is the specific gravity of CSF?

1.003-1.008

What are the max spinal doses of Lidocaine, Bupivicaine, Ropivicaine, and Tetracaine

Lido--60mg
Bupiv-- 9-15
Ropiv-- 15-22.5
Tetracaine--10-15

How long does it take a spinal block to reach its most cephalad level?

20 min

Where is the level of sensory block compared to motor and autonomic with a spinal? With an epidural?

For spinals, the autonomic is 2 levels above the sensory, which is 2 levels above the motor. For epidurals, the sensory and autonomic are on the same level, while motor is 2-4 levels lower

How far is it from the skin to the epidural space?

Ranges from <3 to >8 cm....usually 4-6 cm

How far does the epidural space extend?

• Epidural space extends from base of skull to sacrococcygeal membrane

T or F • There is epidural space within the cranium.

False. There is no epidural space within the cranium

What is safest point of entry into epidural space ?

L2
Safest point of entry into epidural space is the midline lumbar region

How is the epidural dosage calculated?

In adults, 1-2 ml of local anesthetic per segment to be blocked.
Example: you want to block to a T4 sensory level from an L4_5 injection site. This is 12 segments to reach T4: 12 x 1-2 ml/segment = 12-24 ml of agent to get to T4. Note: this volume will decrease with increasing age of patient.
5cc test doses followed by 5cc doses.

Agents For Epidural Block
List shortest onset to fastest.

Agent Onset
Chloroprocaine Fast
Prilocaine Fast
Lidocaine Intermediate
Mepivacaine Intermediate
Bupivacaine Slow
Ropivacaine Slow
These are listed shortest to fastest.
Onset fast; duration short
Slow onset; longer block

Time To Two-Segment Regression
(How long will the drugs last?)

Agent Time Range (min) Duration of Action
Choloroprocaine 50-70 Shortest (60)
Prilocaine 90-130 (100)
Lidocaine 90-150 (110)
Mepivacaine 120-160 (140)
Bupivacaine 200-260 (230)
Ropivicaine 300-600 Longest

How to distinguish amides?

Amides have two i's.
Prilocaine
Lidocaine
Mepivacaine
Bupivacaine
Ropivacaine

What are the two mechanisms of epidurals spread of local anesthetic after injection into the epidural space.

Spread of local anesthetic after injection into the epidural space.
There are two mechanisms of epidually-produced conduction block:
(1) the local anesthetic acts directly at the nerve roots and dorsal ganglia beyond the dura after diffusing through the intervertebral foramen (A in figure); 2. the local anesthetic acts on dorsal and ventral rootlets and spinal cord after diffusing across the dura and arachnoid or perhaps across the dural cuff (root sleeve) into the cerebrospinal fluid.
The local anesthetic also diffuses through the cerebrospinal fluid and into the spinal cord.

What is the target anatomy of an epidural?

same as for a spinal:
1. Primary nerve root
2. secondary rootlets
3 spinal cord (will get up to the cord)

For intrathecal (spinal) or epidural anesthesia), local anesthetics acts on ____________?

For intrathecal (spinal) or epidural anesthesia), local anesthetics acts on nerve rootlets, nerve roots, and the spinal cord

Name the Order of Nerve Blockade for Spinal or Epidural Anesthesia

Order of Nerve Blockade for Spinal or Epidural Anesthesia
The order in which nerves are blocked following epidural administration of a local anesthetic are:
1. B fibers (preganglionic sympathetic efferents) Know this alternate name: ***vasodilation, hypotention
2. C and A-delta fibers (pain, temperature and touch afferents: postganglionic sympathetic and)
3. A-gamma fibers (motor)
4. A-beta fibers (touch pressure proprioception)
5. A-alpha fibers (motor)

Explanation of Differential Nerve Blockade {You must know this!!)

Large myelinated fibers are more sensitive to local anesthetic blockade than the smaller myelinated and unmyelinated fibers.
The anatomy of the nerve root explains the differential sensitivity of nerve types to local anesthetic.
Small-diameter nerve fibers are found close to the nerve root surface, thereby shortening the diffusion path of local anesthetic injected into the spinal subarachnoid space.
The diffusion path to the large-diameter fibers, which are situated deep to the nerve bundle, is longer. Therefore, as local anesthetic diffuses into the nerve root, B fibers are blocked first followed by C (the tiny ones) and A-delta (the ones beside tiny ones) fibers.
The larger A-gamma, A-beta, and A-alpha fibers are blocked last they are large ones in the middle).
At the outside of the root are the B fibers (large myelinated). Immediately interior to the B fibers are the C (dull pain; poorly localized) and A-delta (fast, pain) fibers. The larger A fibers (A-gamma, A-beta, (quick, large mylenated) and A-alpha fibers) are located at the core of the nerve bundle. As local anesthetic diffuses into the nerve bundle, it first encounters B fibers, then C and A-delta fibers, then larger A fibers (A-gamma, A-beta, and A-alpha fibers).

T or F Large myelinated fibers are more sensitive to local anesthetic blockade than the smaller myelinated and unmyelinated fibers

True
Large myelenated (B, A-Beta, A-delta, A∝) > smaller myelinated >unmylenated (C fibers)

__________ nerve fibers are most sensitive to local anesthetic block

Large myelinated fibers are most sensitive to local anesthetic block.

What is the order of sensitivity to anesthetic block?

Large myelinated > smaller myelinated > unmyelinated. Different than order of nerve blockade question above. It means it takes very little to block it.

Choice of Spinal or epidural Anesthesia. Give advantages of each:

Spinal
Takes less time to perform.
Rapid onset
Sensory and motor block is better
Pain during surgery is less.
Epidural
Less risk of post-dural puncture headache
Less hypotension
Can prolong block with catheter
Catheter can be used for post-op pain management.

Structures needle passes through for epidural block:

Structures needle passes through for epidural block:
1. Skin
2. Subcutaneous tissue
3. Supraspinous ligament
4. Interspinous ligament
5. Ligamentum flavum
6. Epidural space

Distance from skin to epidural space:

Average adult, 4-6 cm
Obese individual, up to 8 cm
Thin person, 3 cm

How to Assess sensory block

Assessment of sensory block
O Alcohol swab to assess loss of temperature sensation is the most sensitive indicator of initial onset of sensory block
O Pinprick is most accurate assessment of overall sensory block

_____________ is the most sensitive indicator of initial onset of sensory block.

Alcohol swab to assess loss of temperature sensation is the most sensitive indicator of initial onset of sensory block

_________ is most accurate assessment of overall sensory block.

Pinprick is most accurate assessment of overall sensory block

What are the two main factors affecting sensory block?

Site of injection and nerve root size.
■ Most intense block and fastest onset at site of injection
■ A lumbar epidural injection is associated with greater cranial than caudal spread of local anesthetic; there may be a delay in onset in L5 and S^ segments due to the large size of the nerve roots
■ A midthoracic epidural is associated with uniform spread of local anesthetic; however, the upper thoracic and lower cervical segments are resistant to block because of the large size of the nerve roots and the large number of nerve fibers within them

Where do you find the most intense block and fastest onset with an epidural?

Most intense block and fastest onset at site of injection

What would you expect with spread and onset of a lumbar epidural injection?

A lumbar epidural injection is associated with greater cranial than caudal spread of local anesthetic; there may be a delay in onset in L5 and S1 segments due to the large size of the nerve roots

What would you expect with spread and onset of a midthoracic epidural injection?

A midthoracic epidural is associated with uniform spread of local anesthetic; however, the upper thoracic and lower cervical segments are resistant to block because of the large size of the nerve roots and the large number of nerve fibers within them.

Complications of epidural blockade:

• ***Penetration of a blood vessel
• Epidural hematoma
• Dural puncture
• Back pain
• Neural trauma
• Air embolism (children)
• Subdural catheterization
• ***Intravascular catheterization
• Infection
• Headache
• Hypotension
• Respiratory depression/respiratory failure
• Bradycardia
• Total spinal block secondary to subarachnoid injection
• Horner's syndrome
• Trigeminal nerve palsy

What are the two most common complications of epidural blockade?

***Penetration of a blood vessel
***Intravascular catheterization

Why do you perform a test dose after satisfactory placement of the epidural catheter? 2 things

A test dose is used to detect both subarachnoid and intravascular injection.

How long is an epidural needle (Touy) with in the catheter guide?

Needle is 12
12.5 in hub
first number that shows is "13"

How far is it from the skin to the epidural space?

Average adult, 4-6 cm
Obese individual, up to 8 cm
Thin person, 3 cm

How far would you thread the catheter into the epidural space?

4 cm

If your epidural needle was properly placed and threaded, what should the catheter "read" at the skin?

Average - 9cm 4 + 5
Obese - 12 4 + 8
thin 7 4 + 3

Describe the Sacrum.
What is a caudal block?

Sacrum: triangular bone consisting of 5 fused sacral vertebrae.
It is a volume directed epidural block.

Technique of caudal block

• Position patient for block
• Palpation of landmarks
• Needle insertion through sacrococcygeal membrane
• Correct needle placement
O Sacral bone is present on each side of, in front of, and behind the needle at its point of insertion
O CSF, air, or blood should not be aspirated
O No subcutaneous buldge or crepitus should occur after injection of 2 to 3 ml of air or anesthetic solution
O The injection should feel like an injection into the epidural space
O "Whoosh" test with air while listening with your stethoscope over midline lumbar spine
O If properly placed, the needle should move in the canal, pivoting at the point of penetration. You drop needle to thread catheter.
O There should be no local pain on injection; if the patient has pain, stop the injection
O Paresthesia or feeling of fullness from the sacrum to the soles of the feet occurs during injection and
ceases upon completion
O Feeling of grating as needle moves along the anterior wall of the sacral canal; do not do this just to verify placement
O Ease of epidural catheter placement

Plasma levels of local anesthetic are high or low after caudal administration compared to lumbar epidural?

high

What is the volume of local anesthetic required to get a sensory level block at T10 to T12 with a caudal?

25 to 35 ml

Onset time after caudal block is longer or shorter compared with lumbar epidurals?

longer

Distribution times of a local anesthetic with a caudal is longer or shorter than with lumbar epidurals?

longer

What is the most common postoperative complaint with caudal?

Pain at injection site is the most common postoperative complaint

See More

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set