Neuraxial Anesthesia

Question 1

How many vertebrae in the spine? Categories of vertebrae?

Features?

Answer 1

• The building blocks of the spine are the individual bones called vertebrae.
  
  • Cervical (7)
  • Thoracic (12)
  • Lumbar (5)
  • Sacral (5) fused
  • Coccygeal (4)fused
• all vertebrae have a vertebral body (Except C1)
  
  • vertebral body increases in size as you go down the spinal column
• have 2 pedicles from the vertebral body which join together with lamina
  
  • transverse process for muscle attachmenet
  • spinous process also for muscle attachment
• pedicle with lamina and vertebral body make the vertebral foramen, which houses the spinal cord
  
  • superior and inferior articulating processes/facets
    
    • where adjoining vertebrae articulate
  • when 2 vertebral come together, intervertebral foramen is created
    
    • this is where spinal nerves exit the vertebral column
• spinous process shape changes down vertebral column
  
  • cervical region- spinous process short and bifid until C7 (vetebral prominent)
  • thoracic- spinous process elongated and inferior/posterior direction
    
    • spinous process overlay inferior body of next vertebrae
  • lumbar- spinous process is short and hatchet shaped

Question 2

What are the vertebral curves in the supine position?

Answer 2

• High
  
  • C5
  • L3
• Low
  
  • T5
  • S2

Question 3

What are the ligaments of the spinal column? Purpose?

Answer 3

• Purpose of ligaments (5 ligaments)
  
  • to Stabilize Vertebral body
• Supraspinous- runs C5-sacrum
• Interspinous- entire length
  
  • in between each spinous process
• Ligamentum flavum
• Posterior longitudinal ligament- posterior surface of vertebral bodies (C2-sacrum)
• Anterior longitudinal ligament- anterior surface of vertebral bodies (C1-sacrum)

Question 4

What are the spinal meninges?

Answer 4

Protective membranes continuous with cranial meninges:

• Dura mater
  
  • thickest meningeal tissue
  • Begins at foramen magnum and ends caudally at S2/Dural sac (posterior superior iliac spine); S3 in infants
  • Abuts the arachnoid mater (subdural space)
• Arachnoid mater
  
  • Principal physiologic barrier for drugs moving between the epidural space and the spinal cord
  • Pressure of CSF pushes arachnoid against Dura Mater
    
    • underneath arachnoid mater is subarachnoid space
  • Gives rise to the Subarachnoid space
    
    • house CSF
  • Ends at S2; delicate and nonvascular
• Pia mater
  
  • Adheres to the spinal cord

Question 5

Where does the dural sac end?

What composes the cauda equina?

What is the filum terminal internum? filum terminal externum?

Answer 5

S2

• Superficial landmark is posterior superior iliac spine (PSIS)
• cauda equina is ventral and dorsal roots of lumbar and sacral region of spinal cord
• filum terminal internum (pia mater) piereces dura sac and picks up arachnoid and dura mater which becomes flium terminal externum
  
  • anchors SC to coccyx

Question 6

Where does the dural sac end?

What composes the cauda equina?

What is the filum terminal internum? filum terminal externum?

Answer 6

S2

• Superficial landmark is posterior superior iliac spine (PSIS)
• cauda equina is ventral and dorsal roots of lumbar and sacral region of spinal cord
• filum terminal internum (pia mater) piereces dura sac and picks up arachnoid and dura mater which becomes flium terminal externum
  
  • anchors SC to coccyx

Question 7

Anatomy of spinal cord?

Answer 7

• Foramen magnum to conus medullaris (termination of the spinal cord)- L1-L2
  
  • Spinal cord ends at L1 in adults, L3 in pediatrics
• Gives rise to 31 pairs of spinal nerves
• Each with an anterior root (motor) and posterior root (sensory)
• Roots are in turn composed of rootlets.
• Conus medullaris ends L1 in adult
  
  • has cauda equina in area
    
    • Cauda equina (ventral/dorsal roots of lumbar and sacral region)
  • has filum terminal internum
    
    • comprised of pia mater
      
      • as pierces dural sac–> picks up arachnoid and dura mater form filum terminal externum (anchors SC to coccyx)
• Dural sac- ends at S2 (PSIS)

Question 8

What is a dermatome?

Segment?

Which dermatomes do we need to memorize?

Answer 8

• The portion of the spinal cord that gives rise to all the rootlets of a single spinal nerve is called a segment
• Dermatome is the skin area innervated by a spinal nerve and its segment
• Cutaneous distribution of spinal nerves
  
  • C6 (thumb)
  • C7 (2nd and 3rd finger)
  • C8 (4th and 5th finger)
  • T4 (nipple)
  • T6 (xiphoid)
  • T8 (last rib)
  • T10 (umbilicus).

Question 9

Goal of neuraxial anesthesia?

Answer 9

• Goal: Blockade of nociceptive impulses
  
  • Nociceptive impulse is a stimulus that causes pain or injury
• Blocks all impulses regardless of fiber type (also order of blockade. Return of sensation happens in REVERSE order)
  
  • Autonomic
  • Sensory
  • Proprioception
  • Motor
• Autonomic and motor function are also blocked !!
  
  • ​blocking both dorsal and ventral root
• Order of fibers blocked (this was not covered adv prin, but covered in previous classes? don’t know if we need this level of detail…)
  
  • B fibers – lightly myelinated, pre-ganglionic ANS fibers
  • C fibers – sympathetic, non-myelinated post ganglionic ANS fibers
  • C fibers – dorsal root, non-myelinated slow pain fibers – slow pain/ temperature / touch
  • A delta – medium myelination, fast pain, temperature touch
  • A gamma – medium myelinated, skeletal muscle tone
  • A beta – heavy myelinated touch/pressure
  • A alpha – heavy myelinated, skeletal muscle, motor, proprioception.

Question 10

What is a differential blockade?

Answer 10

Different nerve types have different sensitivities to local anesthetic (LA)

• Autonomic nerves highly sensitive with rapid onset of blockade
  
  • will see decrease in BP and hypotension before loss of sensory/motor
  • if blockade high enough, can see bradycardia
• Sensory nerve intermediate sensitivity
  
  • next modality blocked
• Motor nerves more resistant to LA and have slower onset of blockade
  
  • last modality to be blocked
  • patient may not be able to sense leg, but will be able to move it until motor is blocked

Question 11

How does the autonomic and motor blockade differ between SAB and Epidural blockade?

Answer 11

• Spinal (SAB) Blockade:
  
  • Autonomic blockade 2-6 levels above sensory blockade
  • Motor blockade 2 below sensory blockade
• Epidural Blockade:
  
  • Autonomic blockade same level as sensory blockade
    
    • because of diffusion required through dura/arachnoid mater
  • Motor blockade 2-4 levels below sensory blockade
    
    • iif patient says no feeling at nipple line (T4), autonomic blocked at same T4, cardiac accelerators still intact. not as much bradycardia
    • motor blockade at T6-T8
      
      • ​not as much of a respiratory blockade c/t spinal

Example

• if patient has SAB and says they can’t feel anything at nipple line, sensory blockade is T4
  
  • autonomic blockade will be 2-6 levels above that. T1-T4 is where cardiac accelerators are
    
    • ​so patient will lose ability to regulate heart rate in response to vasodilation that occurs with spinal, causing bradycardia/hypotension
• if same patient has sensory at T4, motor blockade is T6–> impairs accessory respiratory muscles
  
  • ​may not matter in young, healthy individual but may matter in pt with resp decline (copd etc)

Question 12

Advantages/disadvantages to neuraxial anesthesia

Answer 12

Advantages

• Decreased incidence of DVT, cardiac morbidity and death
• Decreased lower extremity vascular graft occlusion, due to vasodilationà increased tissue blood flow below level of blockade
• Decreased incidence of pneumonia
  
  • minimal pain, get up, move, cough, prevent PNA
• Decreased stress response
  
  • decreased catechol release
  • beneficial for pt with CAD
• Avoids airway manipulation
  
  • caution neuraxial technique in those with known difficult airway
  • safest option for known difficult airway is to have control over airway throughout the procedure
    
    • ​if blockade goes high and limits respiratory drive, then have to deal with difficult airway in middle of sx.
• Decreased incidence of PONV
• Intra and postoperative pain relief

Disadvantages

• Hypotension
  
  • If pt can’t tolerate big drop in BP, may want GA
  • ex- pt withs severe aortic stenosis, CAD
    
    • ​epidural may be better option because hypotension is not as profoudn
    • may decide GA is safer
• Delayed case start
• Failure rate depends on experience
• Not a benign anesthetic

Question 13

CV effects of neuraxial block

Answer 13

• Loss of sympathetic activity results in vasodilation below level of blockade, decreasing SVR (15-20%)à decreased preload therefore CO (decrease 10-15%).
  
  • Venous dilation > arterial dilation
• If blockade is at or cephalad to T1-T4 the cardiac accelerators are blocked resulting in bradycardia.
• Results in profound hypotension
• Treatment includes: vasopressors, volume load (15ml/kg), +/- vagolytic drug to treat bradycardia

Question 14

Pulmonary effect of neuraxial blockade

Answer 14

• Low levels of blockade- minimal effect on MV/TV/RR/dead space
• As block ascends, accessory muscle paralysis occurs, a perception of ineffective breathing and decrease ability to cough develops/protect airway (T4-T6 rea)
  
  • even young healthy patients will not be able to feel themselves breath. need to reassure everything is ok
  • if history of asthma, may want to get lower blockade if possible
• No direct respiratory effects except those related to positioning unless high block (C3-5 phrenic nerve) …
• With profound hypotension, may see ischemia of the central respiratory centers causes respiratory arrest
  
  • will need respiratory support. have back up supplies ready!

Question 15

GI/Renal effects of neuraxial anesthesia?

Answer 15

• Nausea & vomiting (20%)
  
  • r/t hypoTN
  • OB complaining → give phenylephrine
• Hyperperistalsis d/t unopposed parasympathetic activity (cranial component & vagus nerve)
  
  • Vagus- innervation of abdomen to left colonic flexure → makes unopposed vagus = hyperparastalsis
• Flow to liver- BP dependent
  
  • Maintenance of MAP – NO untoward liver effects
• Renal blood flow is autoregulated therefore minimal effect
• Bladder dysfunction - Urinary retention
  
  • (sacral component of blocked PSNS)
  • If no catheter is present- avoid excessive IV fluids

Question 16

Metabolic and Endocrine effects of neuraxial anesthesia?

Answer 16

• Blocks the stress response to surgery (decrease catecholamine release) – bc nerves at surgical site are anesthetized
• Catecholamine release may be blocked from the adrenal medulla
  
  • good for pts with CAD as long as you maintain perfusion (DBP)
• Cortisol secretion is delayed
• Shivering – altered thermoregulation w/vasodilation
  
  • Don’t have thermoregulation after spinal (sometimes epidural) and they vasodilate (loss of autonomics) → unable to shiver!
    
    • Keep warm after receive spinal/epidural.

Question 17

Neurological effects of neuraxial anesthesia?

Answer 17

• CBF maintained unless MAP < 60 mmHg
  
  • S/S Low BP:
    
    • *N/V
    • Eventually leading to → apnea and hypoxia
• Decreased signals to Reticular Activating System (RAS)à drowsiness (normal)
  
  • Why need to know DAW

Question 18

Considerations for choosing neuraxial technique?

Answer 18

1. Anatomy
2. Age
   
   • young female in 20s will be easier to place epidural/spinal c/t elder back with arthritic changes/osteoporosis
3. Pregnancy
4. Pathophysiology/Comorbidities
   
   • mild/mod aortic stenosis should do epidural instead of spinal (more controlled onset of autonomic blockade with epidural)
   • severe aortic stenosis- may not want neuraxial technique at all
5. Sensory level required vs adverse physiological effects
   
   • if need sensory up to T4, then you’re going to get autnomic blockade that blocks cardiac accelerators. can your pt tolerate that?
   • may want to do epidural instead of spinal, because autnomic blockade will also only be at T4 with epidural, leaving cardiac accelerators intact.
6. Length of procedure
   
   • a good spinal anesthetic lasts about 2 hours (can prolong)
     
     • ​if sx is longer, may need epidural with catheter so you can redose
7. Post-op analgesic needs
   
   • need one shot and done, or will you need the added analgesia postop?

Question 19

Contraindications to neuraxial anesthesia

Answer 19

• Patient Refusal<< only absolute C/I
• Infection at injection site
  
  • may need to go to diff level
• Increased ICP
• Clotting defects/anticoagulant therapy
  
  • know pt PLT level
  • need >100 k PLT
  • know site protocol
• Severe hemorrhage or hypovolemia
• CNS disease/meningitis
  
  • MS or meningitis for example
• Hysteria/inability to remain still for block placement
• Bacteremia
• Septicemia
• Valvular lesions with fixed stroke volume
  
  • severe AS/MS - maybe just use epidural
  • hypertrophic cardiomyopathy
• Difficult airway
• Full stomach- relative
• Peripheral neuropathies- relative. need thorough documentation of baseline abnormalities

Question 20

Pre-procedure preparaiton for SAB/Epidural insertion?

Answer 20

• Appropriate monitors
• Suction (@HOB)
• Oxygen delivery (nasal cannula/face mask)
• Fluid Bolus
  
  • *15mL/kg or 500-1000 ml – if pt can tolerate.
    
    • 15-20 min before block** (don’t wait too long)
  • Prevent hypoTN (esp SA)
• Equipment for airway management and resuscitation are available
• Emergency drugs drawn and available
  
  • ~Lipids
• Consider sedation prior to procedure
• Identify landmarks – before prep or drape.
  
  • if obese, fill where hips are and ask the patient if your hands are on their hip
    
    • ask patient if you’re in the midline of their back
    • can be difficult to find spinous processes
  • feel where back is located, feel spinous processes

Question 21

What are common landmarks for an epidural?

Answer 21

• C7 – vertebra prominens
• T3- scapular spine
• T7 - inferior angle of scapula
• T12- last rib
• L4- Intercristal line or Tuffiers line = iliac crest
  
  • Lumbar epidural/SA block
  • Stay below level of conus medullaris (L1) → SC ends at L1
• S2- posterior superior iliac spine- for caudal epidural

Question 22

Landmarks for SAB?

Answer 22

• Below level of spinal cord – conus medullaris @L1-L2 (L2-L5 interspaces)
• Spinal cord typically ends at L1 (in adults)

Question 23

Describe the median approach for SAB/Epidural?

Answer 23

• The most common approach
  
  • the needle or introducer is placed midline, perpendicular to two spinous processes, aiming slightly cephalad.
    
    • Landmark: Spinous process
• With median/midline approach will go through: “triple S I LoveEpidurals”
  
  • Skin
  • Subq tissue
  • Supraspinous
  • Interspinous
  • Ligamentum flavum
  • Epidural space

Question 24

Describe the paramedian approach?

Answer 24

• Indicated in patients who cannot adequately flex because of pain or whose ligaments are ossified
• Spinal needle placed 1.5 cm laterally and with a slight cephalad direction to the center of the selected interspace (toward midline)
• Initially angle needle towards midline, but then place it 1-2 cm off midline and then go in a cephalad direction, find the transverse process, adjust angle more cephalad and work more midline.
  
  • Landmark: Lamina (gives good direction on where need to be)
• Good USES:
  
  • Older- interspaces small
  • arthritis – cant push out back
  • Thoracic blocks
    
    • Thoracic spinous processes – go in inferior/posterior direction (in the way of midline approach)
• With paramediam approach will go through:
  
  • Skin
  • subQ
  • LIGAMENTUM FLAVUM

Question 25

Which needle reduces the occurence of post dural puncture headaches?

Answer 25

Pencil Point Needles (Sprotte/Whitacre/Pencan)<newer></newer>

<ul>
<li>Designed to spread the dural fibers → help <strong>reduce</strong> the occurrence of <strong>post dural puncture headache </strong>

<ul>
<li>Do not cut dura fibers (move dural fibers out of way)</li>
</ul>
</li>
<li>Yields a distinct "pop"
<ul>
<li>as the pencil point <strong>penetrates the </strong><strong>ligamentum flavum </strong><strong>&amp; additional pop when going through </strong><strong>dura matter</strong>
</li>
</ul>
</li>
<li>Offers increased "tip strength" to minimize bending or breakage</li>
<li>Precision-formed side hole enables directional flow of anesthetic and reduces the possibility</li>
</ul>

<p>of straddling the dura</p>

<ul>
<li>Tracks straight when advancing through ligaments toward the dura</li>
<li>Less likely to injure cauda equina</li>
<li>Does require more force</li>
</ul>

</newer>

Question 26

Which type of spinal needle has increased risk of PDPH?

What is important about the bevel position with this needle?

Answer 26

Cutting Needle (Quincke/Pitkin) (usually not used anymore) – in NM maybe.

• Cutting needles actually cut, so it cuts through the fibers
  
  • Increased risk of PDPH due to increased trauma to the dura
    
    • CSF lost: Cutting > Pencil point
• Dural “pop” is less likely to be appreciated due to the sharper tip -> “less tactile”
• Introducer may not be necessary depending on patient size
• Bevel position important!
  
  • Bevel must be parallel to dural fibers → decreases incidence of PDPH (less fibers cut)

​Bevel Position:

• Sitting: bevel facing left/right
  
  • Ex: Dural fibers run longitudinally (head to coccyx)
• Lateral: bevel up/down
  
  • Ex: longitudinal fibers are running horizontally
• Less force
• More likely to injure cauda equina

Question 27

Procedure steps for SAB?

Answer 27

• Anatomic landmarks for the block are identified.
  
  • L2-3, L3-4, L4-5 interspace identified (Superior Iliac Crests is L4 Spinous Process)
• A sterile field is established with prep solution is applied with three basic sponges, the solution is (applied starting from the injection site moving outward in a circular fashion.
  
  • In → out
• A fenestrated drape is applied, and using a sterile gauze, wipe the iodine from the injection site to avoid initiation into the subarachnoid space.
  
  • make sure no cleaning solution gets into your actual SA space.
• A skin wheal is raised with 2cc of 1% lidocaine using a 25G needle to the selected space.
  
  • As you inject lidocaine, you use this needle to find your spinous processes.
  • The patient does not feel you hitting the bone, there is no pain with that.
  • Once you know where the spinous processes are and how they are angled, you get come out with local and get introducer.
• A 17G introducer is passed through the skin wheal, angled slightly cephalad through the epidermis/dermis, sub Q, supraspinous ligament, interspinous ligament, stopping in the ligamentum flavum.

Ensure bevel (of needle) is parallel to longitudinal fibers.

• A 25G choice needle is inserted into the introducer, passing through the epidural space, dura, and arachnoid to the sub arachnoid space stopping when the presence of CSF is determined.
  
  • (will feel a “pop” with a pencil point needle punches through dura mater)
  • in very young pts you could even hear the pop.
• Once you’re there you are in the SA space, there will be a little cap you can take off, once you take that off, you’ll see the CSF drop out.
• CSF is aspirated and mixing lines are identified as a change in baricity and temperature as the local anesthetic and CSF mix in the syringe.
• The dose is slowly injected, aspirating after instillation of half the amount of LA.
  
  • Aspirate again after some injecting.
  • After injection aspiration is making sure you’re not in the vasculature somewhere.
• All needles are removed intact (at the same time) and the patient is positioned.
• If you have a problem with good CSF flow and you know you’re in the right spot, try rotating your needle 90 degrees, you can do this up to 4 times, just keep going in the same direction. – increase in PDPHA with this rotation? No. If you use a pencil point needle, you’re probably going to be fine.

Question 28

Describe how to perform SAB with paramedian approach

Answer 28

• Identify caudad edge of superior spinous process
  
  • Skin wheel 1 cm lateral and 1 cm caudad to that point (angle up)
• Needle aimed 10-15 degrees medial and slightly cephalad
• If lamina contacted needle walked off in a medial and cephalad direction
• After CSF obtained same technique as midline – skipping supraspinous and interspinous ligaments, will go from skin/subq to ligamentum flavum

Question 29

What are some factors affecting spread of local anesthetic in SAB?

Answer 29

(Ones in BOLD are most important with SAB)

• A number of factors affect the spread of the injected local anesthetic solution within the CSF and the ultimate level of the block obtained.

Among these are:

• Baricity of the LA solution
  
  • How heavy is the LA compared to CSF
• Position of the patient
• Concentration and volume injected
• Level of injection (L2 vs L4)
• Barbotage/Rate of injection
  
  • Very quickly → Will have a wider spread (higher block height)
  • Slowly – preferred, will help autonomics
• Direction of needle & bevel
  
  • Bevel should be parallel to dura fibers
  • Pencil point- ok to have bevel perpendicular to dura
    
    • If bevel up → higher spread
    • If down → lower spread

Question 30

Decisions to consider when dosing SAB?

Answer 30

1. Surgical site – spinal only reliably lasts up to 2 hrs, with decadron and vasopressors.
   
   • Decadron is effective in improving spinal anesthesia duration – no one knows why
   • C/S- need to cover T4 nipple line
   • Cerclage only needs T10/T12
2. Length of procedure
   
   • spinal only reliably lasts up to 2 hrs
3. Body size (height/weight)
   
   • Morbidly obese individual – go slower on dosing, weight will compress that space, so if you dose (inject?) as normal you’ll get a big spread bc of the pressure of the body habitus.
   • Different heights need different amt spinal anesthetic
4. Physiology

Question 31

Characteristics of epidural space?

Answer 31

• L2 = widest point
  
  • 5 mm
• Contains fat and blood vessels (Batson’s plexus)
  
  • Batson’s plexus – valveless veins, will aid systemic absorption
  • Fat – will absorb some of the lipophilic medicines
• Closed space
• Medication and catheter deposited into potential space
  
  • Epidural space is potential space- make exist when air/saline injected!

Question 32

What type of needle is used with epidurals?

Techniques used for epidurals?

Answer 32

• Continuous catheter technique – Tuohy needle (slight curve with nice big open bevel at end)
  
  • Entire length = 10 cm
    
    • As you go through skin, subq, supra, intra, LIGAMENTUM flavum, this is where you stop with the needle, once its in there, stop.
    • Just like with spinal needle, you want your Touhy bevel to be either left or right while sitting. Because if you go too far and give your patient a “wet tap,” the bevel angle will help you decrease risk of PDPH.
• Loss of resistance technique
  
  • Air or saline filled glass syringe
    
    • ~ once reached epidural space → fluid is released
    • ~ If tapping and no loss of resistance → not in epidural space
    • research has shown air increases risk for PDPH. Saline has less risk

Question 33

Technique for lumbar/thoracic epidural placement?

Answer 33

• Pre-procedure considerations (same as SA)
  
  • Identify app level
    
    • Ex: Lumbar- Tuffiers line
• At the desired spinous process, the Tuohy needle is advanced into skin, with the needle bevel parallel to longitudinal fibers:
  
  • Skin
  • Subcutaneous tissue
  • Supraspinous ligament
  • Interspinous ligament
  • Ligamentum flavum – there is often a “pop” as the needle pierces the Ligamentum flavum
    
    • Needle anchors there
    • (place glass syringe on bc next place is epidural space)
  • Epidural space
• Need needle placement into ligamentum flavum
• Ligamentum flavum depth from the skin is 4 cm (80% of patients between 3.5-6 cm)
  
  • Tuohy needle 10 cm long (pay atten when around 3 cm mark)
  • Feel anchoring (place glass syringe)
    
    • Thumb bounce on glass syringe
  • Keep at least one hand at ALL times to anchor self to back
    
    • Advance little at a time and “tap” until resistance is lost
• 5-6 mm thick at midline in lumbar region
• LOR technique - Steady pressure on plunger compress air bubble while advancing the needle – when epidural space entered resistance is gone and air (fluid) is easily injected
  
  • Ensure NO CSF after taking off syringe (if did→ wet tapped) → need to pull back needle and try again
• Epidural Catheter Placement (no CSF should be coming out)
  
  • Note needle depth when LOR noted
  • Advance catheter after LOR cm amount:
    
    • Normal Pts: 2-3 cm advance
      
      • Ex: if LOR at 5 cm → advance catheter to 8 cm
    • PARTURIENTS: 4-6 cm advance
      
      • Ex: if LOR at 5 cm → 9-11 cm of cath in pts back
  • Remove Tuohy needle WITHOUT removing catheter . DO NOT PULL CATHETER BACK WITH TUOHY NEEDLE IN PATIENT- can shear off catheter
  • Instead “push-pull” action
    
    • Push catheter as you remove the Tuohy needle
  • Ensure tip of catheter remains sterile

Question 34

Purpose of test dose?

What should you always do before a test dose?

Answer 34

• Always aspirate!!! and give a test dose prior to injection/use incremental dosing- note baseline HR and BP
  
  • aspirate before injecting LA. (before test dose or when increasing dose)
  • Only inject a small amount at a time
    
    • ~ 5 mL max, then aspirate again and inject another fine.

Traditional test dose: 3ml

• Lidocaine 1.5% w epinephrine
  
  • Epinephrine 1:200,000 dilution
• 45 mg lidocaine and 15 mcg epinephrine
  
  • Helps detect → accidental intravascular & subarachnoid injection
    
    1. Intravascular injection: HR increase w/in 30 sec (~15-20 points)
    2. Subarachnoid injection: (“wet-tap” block)
       
       • Ask pt if they have numbness or tingling
       • Epidural block normally takes a few minutes
       • If saying lost sensory and motor quickly w/in 1 min of test dose → in subarachnoid space
       • If it takes 5 minutes for that onset of can’t feel legs – probably epidural.
         
         • You should NOT be expecting a quick acting epidural

Prior to test dose: note HR and BP!!

• Always give test does with epidural, test dose has 2 points
• After you give a test dose you really should wait 5 minutes before epidural.

Question 35

What determines the spread of epidural block?

Answer 35

• Volume and Concentration of LA (helps det. Level of spread)
  
  • Large volume of a dilute solution
    
    • Decreased sensory and motor blockade with wide segmental spread.
    • The quality and extent of the epidural block is dependent upon volume and concentration of the LA
• For induction of epidural blockade:
• 1.25 - 1.6 ml of LA per segment you need.
  
  • Ex: epidural placement at L3-4 interspace and need T4 level sensory blockade
    
    • Count up to T4 level and give 1.25-1.6 ml PER segment
    • Look at Bowman lecture examples for doses!

Question 36

Common complications and management of spinal/epidural/caudal

Answer 36

1. Hypotension
   
   • Tx:
     
     • 1. Prevention → fluid
     • 2. Vasopressors or vagolitic drugs if blocked at T1-4 level
2. Bradycardia
3. Sudden cardiac arrest
4. N/V
   
   • From unopposed GI PSNS activity
   • But most likely caused by HYPOTN → tx
5. Unintentional Intravascular Injections
   
   • Epidural
     
     • use test dosing
     • note VS BEFORE/AFTER injection of test
   • KNOW:
     
     • s/s of LA toxicity
       
       • numbness lips, ears ringing, coma
     • tx of LA toxicity (BOWMAN LECTURE)
6. Unintentional Intrathecal Injection
   
   • TEST DOSE important → identify quick sensory blockade (= intrathecal)
7. Catheter shearing
   
   • Do not remove catheter within Tuohy needle
   • Catheter shearing as you try and advance it, the needle can shear it off in the body.
8. Post-dural Puncture Headache → wet tap, may happen.
9. High Blockade
   
   • Prepare for AW management
   • Symptomatic support (vasopressors/vagolytic tx)
10. Inadequate Blockade
    
    • Ex: one side might be better blocked than the other, when this happens have the pt lie on the side that is not well blocked. Should help some. GRAVITY
      
      • If completely inadequate, remove block and try again.
11. Neurologic Complications
12. Backache
13. Infections – septic meningitis
14. Urinary Retention
15. Epidural hematoma

Question 37

Incidence of PDP/H? What causes a PDPH?

S/S? Treatment?

Answer 37

Incidence: 1 – 4 %

• Increased incidence:
  
  • Younger female patients
  • Larger needle size
  • Pregnancy
  • Air for LOR (instead of saline)
  • Cutting tipped needles perpendicular to meninges
  • Multiple puncture attempts

Causes:

• CSF leaking out of subarachnoid space
• As CSF leaks → decrease intracranial pressure with compensatory cerebral vasodilatation → brainstem sags which stretches meninges and pulls on the tentorium
• S/S:
  
  • Frontal to occipital area (Fronto-occipital)
  • Postural
    
    • Sit up/stand → PAIN
    • Lay down → immediate relief
  • Occurs within 1 day to 1 wk of spinal/epidural anesthesia

Treatment

• Bedrest, hydration, oral analgesics (NSAIDs), caffeine, abdominal binder, epidural saline injection
• Epidural Blood Patch

Question 38

What is associated with increased incidence of PDPH>

Answer 38

• Younger female patients
• Larger needle size
• Pregnancy
• Air for LOR (instead of saline)
• Cutting tipped needles perpendicular to meninges
• Multiple puncture attempts

Question 39

Primary cause of epidural hematoma?

s/s?

treatment?

Answer 39

• Primary cause: coagulation defect
  
  • Plt req_:_ > 100,000
  • Check bleeding time
• Presents with numbness or lower extremity weakness greater than expected from spinal anesthesia
• Consult neurosurgery immediately if a hematoma is suspected
  
  • 6-8 hrs before permanent injury
• Greater than 8 hours makes the odds of decompression less successful

Question 40

Recommendations for anticoag with neuraxial technique?

(LMWH prophylactic, LMWH therapeutic, heparin, warfarin)

Answer 40

• LMWH – Prophylactic dosing
  
  • hold 10-12 hours pre-placement of epidural
  • hold 10-12 hours post surgical procedure (apex says 6-8)
• LMWH – Therapeutic dosing:
  
  • Hold 24 hrs before block
  • Hold 24 hours after block
• Heparin
  
  • Can be given 1-2 hours post SAB/epidural (dvt prevention)
  • Hold 2-4 before block placement
• Warfarin
  
  • Before block hold 5 days