Regional Anesthesia Central Blocks

Front 1

Central blocks……why

Back 1

Decr. incidence of DVT, PE, bleeding, pneumonia/resp. depression
Decr. incidence of cardiac complications, vascular graft occlusions
Decr. stress response
Sympathectomy= decr. SNS output
Earlier return of gastric function
Decr in PONV
Decr incidence of post-op ileus
Decr need for post-op narcotics

Front 2

Anatomy

Back 2

33 vertebrae
31 paired spinal nerves
Cervical and Lumbar regions convex ventrally
Lumbar region is the highest point when lying flat (L3)
Thoracic and Sacral regions convex dorsally
Lowest point T5-T6
Vertebral column 26-27 inches long
Spinal cord 17-18 inches long

Front 3

Anatomy

Back 3

C1=atlas; lacks a body and attaches to skull
C2=Axis, is felt just below the occipital protuberance.
C7 = cervicothoracic junction
Most prominent midline structure at base of neck
A line drawn between the lower borders of the scapula crosses the vertebral axis of approx. T7
A line drawn between both iliac crests usually represents L4-L5.

Front 4

Vertebral body

Back 4

structural base of the vertebra

Front 5

Paired pedicules

Back 5

Attached directly to the vertebral body dorsally

Front 6

Laminae:

Back 6

Join the pedicules to form an oval space called the vertebral foramen

Front 7

Vertebral foramen

Back 7

Creates the spinal canal which houses the spinal cord, its covering and vascular supply

Front 8

Intervertebral foramen

Back 8

Created by the notching of 2 adjacent pedicles. Corresponding spinal nerve travel through each foramen

Front 9

Midline spinous process

Back 9

(arises b/t laminae) marks the midline of the spine’s surface (posteriorly)

Front 10

Transverse spinous process

Back 10

@ junction of lamina and pedicle
Processes serves as area of attachment for muscles/ligaments

Front 11

Supraspinous ligament

Back 11

Most posterior(closest to skin) ligament. Connects vertebral spines

Front 12

Epidural space

Back 12

Potential space between the ligamentum flavum and the dura mater.
Starts at the foramen magnum ends at the sacrococcygeal membrane of the sacral hiatus.
Contains nerve roots that exit from intervertebral foramina to peripheral locations
Also contains fat, lymphatics and large network of veins (Batson’s plexus) much easier to get toxicity because of all the vasculature (especially really lipid soluble drugs)

Front 13

Dura mater

Back 13

tough outermost layer; extension of cranial dura ends @ S2 where it fuses with filum terminale
“Sub” dural space (not clinically useful…however

Front 14

Arachnoid mater

Back 14

delicate non-vascular layer closely attaching to dura mater
“Sub” arachnoid space is b/t here and pia

Front 15

Pia mater

Back 15

immediately overlaying the spinal cord
Highly vascular layer
Ends at filum terminale which anchors cord to the sacrum

Front 16

Spinal canal is the widest here and the vertebrae body is the smallest. The spinal processes are horizontal.

Back 16

Cervical vertebrae

Front 17

Sacral Hiatus

Back 17

Defect in the roof of the dorsal aspect of the caudal end.

Front 18

Coccyx

Back 18

Represents fusion of three or four rudimentary vertebrae and has no anesthetic significance.

Front 19

Spinal cord Extends from

Back 19

foramen magnum to L3 in the newborn and moves up with age to ~L1.

Front 20

The terminal end of the spinal cord

Back 20

conus medullaris.

Front 21

Dura mater

Back 21

Outermost layer; dural sac extends to S2

Front 22

Arachnoid

Back 22

middle layer; also ends at S2

Front 23

Pia mater

Back 23

clings to spinal cord; ends at filum terminale

Front 24

nerve roots.
31 pairs

Back 24

Each nerve root is composed of multiple rootlets
Area that a group of rootlets comes out to form a single spinal nerve is called a cord segment
The area of skin (periphery) the spinal nerve and cord segment innervate is called a dermatome

Front 25

Cauda equina

Back 25

Distal end of the spinal cord (below L1) where it branches off into terminal strands. These strands are bathed in CSF and enclosed within the dural sac.

Front 26

BLOOD SUPPLY TO SPINAL CORD

Back 26

2 posterior spinal Arteries
Responsible for ~ 25% of blood supply to the cord
Primarily supply posterior portion of cord
Receive chief blood supply from cerebral arterial system and many collaterals. Segmental arterial injury is unlikely because of collaterals.
Filum is what anchors the cord.
1 anterior spinal artery:
Responsible for ~75% of total blood supply to cord
Primary supplier of anterolateral cord
Supplied by many radicular arteries; poor collaterals
Artery of Adamkiewicz or arteria radicularis magna.
Single segmental branch of the aorta that supplies nearly all of the flow to the lower thoracic and lumbar segments.
Injury renders this entire section at risk for ischemia.
Artery of Adamkiewicz is typically unilateral and most often occurs near T8-T12 on the left side.

Front 27

Signs of absorption

Back 27

one of first signs are confusion from the hyponatremia

Front 28

Bladder perforation

Back 28

one of the signs for that is excruciating shoulder pain

Front 29

Contraindications
Controversial
Absolute

Back 29

Pt refusal
Infection at site of puncture
Hypovolemic shock
Severe hemorrhage
Severe idiopathic coagulopathy
^ ICP
Indeterminate neurologic disease
Aortic stenosis

Front 30

RELATIVE C/I FOR EPIDURAL SPINAL

Back 30

Pre-existing neuropathies
Medical anticoagulation
Heart valve dx (other than AS)
Dementia
Demyelinating dx (MS)
Previous major spinal surgery

Front 31

NYSORA guidelines

Back 31

NSAIDS (including ASA) are not contraindications
LMWH: hold 12hr. Before & 2 hr after catheter removal
if epidural vein punctured: hold heparin for 2 hr. and LMWH for 24 hr
GIIa/IIIb inhibitors held for 4 weeks post epidural
Stop clopidogrel 7 days pre and ticlopidine 14 days pre

Front 32

Needles

Back 32

Needles are either sharp or blunt at the tip, with either end injection or side injection.

Front 33

Quincke-Babcock

Back 33

It has a med bevel length with sharp edges, a sharp point and end injection. Usually typical 22g. This is a cutting needle. (turn bevel to the side) it will spread instead of cut.

Front 34

Whitacre, Sprotte needle

Back 34

“pencil point” rounded bevel, no cutting edges and side injection. Typical 24g needle in kits.

Front 35

Tuohy needle

Back 35

epidural needle 16-18g, 3 inches long, bevel tip and gentle curve to prevent dura puncture.

Front 36

Paramedian approach

Back 36

Useful in elderly or others with calcified interspinous ligament or difficulty flexing spine
Identify correct level as before
Palpate spinous process
Insert needle 1 cm lateral to this point and direct toward middle of interspace
Ligamentum flavum is usually 1st ligament encountered using this technique

Front 37

Specific Gravity

Back 37

Frame of reference for specific gravity is CSF 1.003-1.008.
Hyperbaric agent= Heavier than CSF SG > 1.008
Hypobaric agent=Lighter CSF SG < 1.003
Isobaric agent= Close to CSF stays where injected

Front 38

Hyperbaric Technique

Back 38

Outcome is dependent on position of patient during and immediately after injection. Saddle block vs supine vs lateral. 3-5 minutes.
Cephalad spread can increase with raising the patients legs or trendelenburg position.
Neck flexion can somewhat protect progression into cervical levels.

Front 39

Isobaric Technique

Back 39

Tetracaine, lidocaine, bupivacaine can all be mixed with CSF.
Can also use lower conc. Of local which will make isobaric
Solution remains near injection site decreasing high blocks and sympathetic block.

Front 40

Intra-abdominal pressure

Back 40

Indirect affect on final level of local injected.
Causes changes in the contour of the subarachnoid space and total volume of CSF.
Ex. Ascites, obesity, tumors, pregnancy. Changes from direct pressure in addition to decrease venous return and “backflow” into epidural veins. Large epidural veins occupy space. All of this can cause a more proximal spread.

Front 41

Pregnancy

Back 41

Uterus causes increased intra-abdominal pressure and increased volume in the epidural venous plexus.
This results in smaller and tighter epidural and subarachnoid spaces.
Higher spread

Front 42

Obesity

Back 42

Overlying adipose tissue. Difficult to identify landmarks.
May need longer needle. 4” or 6”
Paramedian approach is difficult.
Increased intra-abdominal pressure.

Front 43

Age

Back 43

Spinal and epidural spaces are thought to become smaller and less compliant.
Stenosis, scarring and calcification of tissues
Require decreased dosages.

Front 44

Physiologic changes associated with spinal anesthesia:
Cardiovascular

Back 44

Sympathetic denervation results in cardiovascular changes based on the degree of sympathetomy.
Block height determines extent of sympathetic blockade
Sympathetic chain originates from the thoracic and lumbar spinal cord.
Arterial and venodilation BOTH occur to produce hypotension

Front 45

Total sympathectom

Back 45

: increase in volume of the capacitance vessels, and a decrease in venous return to the heart. Decrease in preload equals hypotension.

Front 46

Partial sympathectomy

Back 46

T8 block usually allows physiologic compensation with vasoconstriction, mediated by sympathetic fibers above the block.

Front 47

Cardiac accelerator fibers

Back 47

sympathetic efferents (T1-T4). Increase heartrate when stimulated. High central blockade, unopposed vagal activity leads to bradycardia.

Front 48

PULMONARY COMPLICATIONS TO CENTRAL BLOCK

Back 48

Primary influence secondary to motor blockage of intercostal muscles and abdominal muscles.
TV is unchanged
Phrenic (diaphragm) block is rare. C3-C5. Concentration is usually not enough to fully block A alpha nerves. (BIG). Apnea is usually related to hypoperfusion of brainstem resp centers from hypotension

Front 49

URINARY COMPLICATIONS FROM CENTRAL BLOCKS

Back 49

Renal blood flow is maintained due to autoregulation
Muscle tone in the bladder is eliminated and urinary retention is common.
S2-4 blockage is often last to resolve.

Front 50

GI COMPLICATIONS FROM CENTRAL BLOCKS

Back 50

N/V
Unopposed parasympathetic activity
Hypotension

Front 51

METABOLIC AND ENDOCRINE COMPLICATIONS FROM CENTRAL BLOCKS

Back 51

Sympathetic activation from pain and surgery leads to many hormonal and metabolic responses.
Regional anesthesia can block the sympathetic responses that cause hypertension, myocardial stress and hyperglycemia.

Front 52

Complications

Back 52

Pain with injection
Backache
Headache
Urinary retention
Meningitis
Vascular injury
Nerve injury (cauda equina syndrome; TNS)
High spinal
If there is vascular injury is what would cause paralysis, they were anticoagulated, bleeding causes a hematoma and causes ischemia and the spinal nerves die. Emergent situation, immediate surgery to evacuate that hematoma. Key here is identification. You will see decreased sensory and motor function won’t return normally. Loss of bowel or organ ability to urinate.

Front 53

Backache

Back 53

Needle insertion can cause hyperemia, local tissue irritation, reflex spasm of muscles.
Soreness can last for 10-14 days
Patients with herniated disks or chronic back pain may have concerns.

Front 54

Headache

Back 54

Spinal headache related to dural puncture and leakage of CSF leading to a decrease in CSF pressure.
This causes a downward traction on the structures of the CNS.
Headache is postural. Worse when upright.
Typically starting within 6-12 hours after puncture.
Higher incidence in females, skinnier, and younger people

Front 55

Postdural puncture headachePDPH
Treatment includes

Back 55

Fluids/hydration
Oral analgesics
Abdominal binder
Caffeine (oral or intravenous)
Bedrest/supine
Try to treat medically first. Caffeine increases the production of CSF. You can’t do a spinal on a patient with an infection. You need to treat them medically. So if they have a temp you can’t do a spinal.

Front 56

Urinary retention

Back 56

Blockage of S2-4 is associated with loss of bladder tone and inhibition of the voiding reflex.
Common in males.
Long cases may need foley or straight cath at the end of case to prevent neurogenic bladder.
Bladder distension can cause hypertension and tachycardia.

Front 57

Meningitis

Back 57

Chemical (aseptic) Used to be a problem when needles were reused and cleansed with caustic substances.
Can be a problem if betadine is not removed from back before dural puncture

Front 58

Vascular injury

Back 58

Epidural hematoma: Bleeding from epidural venous plexus.
Any spinal anesthetic that does not resolve within a reasonable amt of time or suddenly progresses after initial affects have worn off should be investigated.
Early diagnosis is key.
CT or MRI
Emergency decompressive laminectomy.

Front 59

High spinal anesthesia

Back 59

Severe hypotension
Profound bradycardia (Cardioaccelerators T1-T4)
Respiratory insufficiency
Hypoperfusion to medulla

Front 60

TREATMENT OF HIGH SPINAL

Back 60

Support airway and circulation
Assist ventilation with 100% O2.
Intubation to protect airway
Fluids, pressors
Head up does not decrease spinal at this point and can increase hypotension.
Ephedrine is a good choice
May need epinephrine

Front 61

Epidural anesthesia

Back 61

Local diffuses through the intervertebral foramen to nerve roots and through meninges to CSF
Require diffusion from site of injection need more volume
Unlike spinal anesthesia, which is all or none block, epidurals can provide analgesia with minimal block or full motor block

Front 62

ANATOMY OF THE EPIDURAL SPACE

Back 62

Epidural space is bounded by the dura ventrally and the ligamentum flavum dorsally.
It extends from the foramen magnum to the sacral hiatus. Widest point at L2
The space is filled with loose connective tissue that surrounds the epidural veins.
Epidural venous plexus
Obstruction to venous return involving the vena cava will cause engorgement of the azygos system and enlargement of epidural venous system (OB pt during contraction)
Stay midline
No arteries in the epidural space, but main collateral flow to the anterior spinal artery crosses close to lateral area.
Diffusion of meds from point of injection produces epidural anesthesia.
Large spinal nerves L5 and S1 are the most difficult nerves to block in the epidural space.

Epidural anesthesia requires a tenfold increase in dose of local anesthesic to fill the potential epidural space.
Onset is slower secondary to diffusion across membranes.
Segmental anesthesia: A band of anesthesia is produced, extending upward and downward from the injection point.

Front 63

Segmental spread depends largely on the volume of the local.

Back 63

5ml may produce a narrow band of 3-5 dermatomes where 20ml volume will produce anesthesia from upper thoracic area to sacrum.

Front 64

MARKS ON THE TOUHY

Back 64

9 marks. Each one alternating is 1 cm. So 9 cm. You see 5 spaces, then you will say that you have loss of resistance at 4. (9-5 = 4). The longer fatter mark is 12, you need 12 before the catheter even leaves the needle. So add the 4 to 5 and that is where you want to leave the catheter against the skin.

Front 65

Test dose

Back 65

3 ml 1.5% Lido with epinephrine 1:200,000 (5 mcg per cc of epinephrine)
Intravascular injection will cause heart rate to increase by 20% within 30-60 seconds, circumoral numbness, ringing in ears
Subarachnoid injection produces signs of spinal anesthesia within 3 minutes

Front 66

EPIDURAL ANESTHESIA EFFECTS THE

Back 66

nerve roots and dorsal ganglia outside the dura. Also diffuse across the dura to the spinal cord

Front 67

The dose of the local anesthetic is a function of the

Back 67

volume injected and the conc of the solution
Ex. A higher volume of a lower concentration will result in a higher sensory level with less motor block.
A lower volume of a higher concentration will result in a lower but denser sensory and motor block.

Front 68

EPIDURAL COMPLICATIONS

Back 68

Similar to spinal complications
Wet tap: Epidural needle punctures the dura. 17g needle makes a big hole. HA in 40%-80% of patients
Infection: Sterile tech. Signs of meningitis( Nuchal rigidity, fever, chilling)
Epidural abscess or hematoma- requires immediate surgical intervention.

Front 69

Neuraxial opioids

Back 69

Opioid receptors present in spinal cord
Modulate A-delta & C-fibers
Improves perioperative analgesia
Works synergistically with local; enhances analgesia without increasing motor or sympathetic blockade
Reduces supraspinal effects of systemic opioids
Causes dose dependent pruritis, nausea & urinary retention

Front 70

Morphine
(EPIDURAL)

Back 70

H2O soluble
Delayed onset; won’t see immediate effect
Look for delayed respiratory depression 6-12hrs post injmorphine is more of a rostral spread. ection

Front 71

Fentanyl
(EPIDURAL)

Back 71

See more immediate effect; decr intraoperative need for opioids/volatile agent
Early respiratory depression 2-4 hours
Absorption into nerve rootlets; vascular system, cord
. The fentanyl doesn’t spread as much because it is lipid soluble

Front 72

Spinal opioids:
Morphine

Back 72

Prolonged spinal analgesia 6-18 hrs
Not useful for intraoperative relief due to hydrophilic nature
Late onset of respiratory depression

Front 73

Spinal opioids
Fentanyl

Back 73

Useful for analgesia after injection
More rapid uptake
With appropriate dose (10-25 mcq’s) little incidence of resp depression (if seen is early not delayed

Front 74

Caudal anesthesia

Back 74

Most common regional in pediatrics
Most commonly used for surg of the lower extremities, perineum and lower abdomen.

Front 75

CAUDAL ANESTHESIA PROCEDURE

Back 75

Patient is placed lateral or prone. Watch airway.
Identify landmarks.
Sacral cornua should be easily palpable just above gluteal crease
Feel for sacral hiatus. (located about 5 cm from the tip of the coccyx between the sacral cornua.)
Feels like soft area between sacral cornua
Sterile prep and remove betadine.
Skin wheel if awake
22g jelco needle
Introduce needle ~ 70 degrees angle to skin through the sacrococcygeal ligament. You do have to put a little pressure on this it’s tough.
Firm but non vigorous pressure needed
Once through ligament drop needle to 45 degree angle and advance slightly < 4 cm
Remove needle , aspirate and inject.
Often confirm with injection of small amount of air
1cc/kg (0.175-0.25% bupivacaine)