Epidural & Spinal Flashcards
Epidural Anesthetic
Reversible neuronal transmission chemical blockade produced via LA injection into the EPIDURAL space (above the dura)
Local anesthetic leaks into intravertebral foramen & paravertebral spaces
Medication spread = diffusion dependent
Longer onset 15-20min
Temporary interruption autonomic, sensory, & motor nerve fiber transmission r/t drug concentration & volume
Epidural Advantages
↓surgical stress (therefore opioid consumption)
Blunts SNS response
↓blood loss - controversial d/t hypotension
↓DVT risk r/t coagulation cascade
Titratable, able to re-dose w/ catheter, convert from pain management to 1° anesthetic (labor epidural)
Versatility to control the sensory & motor blockade extent
Used w/ or w/o adjunct medications
Epidural & Spinal Disadvantages
Post-dural puncture headache
Sympathetic blockade → hypotension & bradycardia
Block lasts much longer than the procedure +/-
Urinary retention (more common spinal side effect)
Regional takes too much time - more difficult than a spinal
Epidural/Spinal ABSOLUTE Contraindications
Patient refusal ↑ICP (herniation risk) Severe aortic or mitral valve stenosis ↓SNS → relative Coagulopathy or bleeding diathesis Severe hypovolemia Infection at injection site
Epidural/Spinal Relative Contraindications
Uncooperative patient Local anesthetic allergy Anticoagulant or thrombolytic therapy Pre-existing neurologic deficit Chronic headache or backache (document baseline) Severe spinal deformity Valvular stenosis
Epidural/Spinal Pre-Procedure Monitoring
Patent large bore PIV Suction Airway supplies Difficult airway equipment EKG, BP, SpO2, ETCO2 Oxygen Medications - induction, paralytic, atropine, vasoactive Support person
C7
Most prominent cervical process
T7
Scapula inferior tip
L4
Tuffier’s line
Superior iliac crest aspect
Epidural/Spinal Positioning
Sitting, lateral decubitus (hip fracture), prone
Needle approaches - midline or paramedian
Placement - thoracic, lumbar, or caudal
Assistant/support person
Patient hold pillow or blanket or lean over table
- Drop head down & roll his/her back
- Push out against hand on back to ensure correct position
Proper positioning = key to successful procedure
Spine flexion → increases interspinous spaces
Flex at neck & back not only hips to optimize the interspinous space
Epidural Procedure
- Proper positioning
- Palpate landmarks
- STERILE procedure (hat, mask, & sterile gloves)
- Open tray
- Cleanse injection site & allow to dry completely
- Set-up tray & draw up meds
- Apply sterile drape
- Re-position patient & identify injection site
- Inject local anesthetic 25-27G
- Place epidural Tuohy needle
- Attach normal saline syringe
- Advance 1mm until lose resistance
- Removed syringe & thread the catheter 3-5cm past the needle hub
- Remove needle PRIOR to pulling the catheter back
- Test dose
- Secure the catheter
Tuohy Needle
Pronounced curve Orient bevel up Blunt tip to help prevent damage to structures Marked at 1cm increments Standard = 9cm Longer & more rigid needles
Crawford Needle
Epidural needle Not curved Easier to insert ↑dural puncture rate Requires more skilled clinician
Standard Depth at Lumbar Level
5cm (2.5-8cm) to the ligamentum flavum
Depth & needle angle changes based on vertebral level
Bromage Grip
One-hand grip firm support to stabilize the needle
Attach & secure the syringe (filled w/ air or saline)
Pass the catheter through the needle
Alternative - stabilize needle on both sides (two-handed)
More stability as advancing needle
Hanging Drop Method
Less common
Epidural needle hub filled w/ saline until small drop visible
Negative pressure created as needle passes into epidural space “sucks” the drop in
More pronounced at thoracic levels
Epidural Space Dilation
Loss resistance noted when needle passes through the epidural space Syringe contents (air or saline) injected into the epidural space When syringe removed common to see small amount clear fluid Puncturing the dura results in profuse CSF return
Epidural Catheters
Typically 2 gauges smaller than the needle Open-ended or multiport Dashed lines = 1cm Two-dashed lines = 10cm Thick line = 12cm
Parethesia
Inform/prepare the patient prior to procedure about the steps & what to expect
When to notify provider (i.e. parethesia or pins & needles sensation)
Catheter has entered the nerve root
Withdraw the catheter
Catheter Advancement
Noted needle location at the skin
Advance catheter 3-5cm past needle hub
Ensure adequate catheter available to hold securely when removing needle
Unable to pull back catheter while needle in & unable to re-advance once needle removed
Shallow Placement
Potential to results in dislodgement from the epidural space
Deep Placement
Dura puncture risk
Passage into the epidural vein
Migration through the intervertebral foramen
Test Dose
1.5% Lidocaine w/ Epi 1:200,000 or 5mcg/mL
Inject 3mL = 45mg Lidocaine & 15mcg Epi
Subarachnoid space → spinal anesthetic
Intravascular → >20% increase HR & BP
Note vital signs before test dose & ask patient about last contraction
Paramedian Approach
Patient unable to flex spine - previous spine surgery, rheumatoid arthritis, or hip/upper leg trauma
Skin wheal 1cm lateral & 1cm caudal to spinous process
Advance needle toward midline
- Needle passes through paraspinous muscles to ligamentum
- Does NOT pas through supraspinous or interspinous ligaments
Trouble Shooting
Contacting Bone
Withdraw the needle & stylet to subcutaneous fat
Reposition the introducer & reinsert the needle
- Needle touching the spinous process superior crest below the interspace → redirect cephalad
- Needle touching the spinous process inferior surface process above the interspace → redirect caudal
- Repeatedly encounter bone → remove the needle & reassess landmarks
Trouble Shooting
Paresthesia
Patient experiences paresthesia during catheter insertion
Sharp, shooting pain indicates needle w/in nerve root
STOP
- Resolves → continue w/ procedure
- Persistent → withdrawal & reposition
Trouble Shooting
Blood in Catheter
Frank blood vs. blood-tinged
Continuous blood - withdraw the catheter & replace
Blood-tinged that clears up continue
Caudal Anesthesia
Distal approach to the epidural space Indications: - Hemorrhoidectomy - Chronic pain patients - Pediatric analgesia (inguinal herniorrhaphy, circumcision, & perineal procedures)
Caudal Dosing
0.5-1mL/kg
2.5mg/kg
Adult test dose 12-15mL sacral anesthesia
Lower extremity procedures 20-30mL
Combined Spinal-Epidural
CSE
Offers advantages of both spinal & epidural anesthesia w/ reducing the disadvantages
One-Level CSE
Place epidural needle
Spinal needle passed through
Small intrathecal dose injected
Epidural catheter place
Two-Level CSE
Spinal placed first
Epidural catheter placed 1-2 levels above
Parasagittal U/S
Low frequency curvilinear transducer
Paramedian (off midline)
Longitudinal view
Located sacrum 1st = fused (hyperechoic line)
Axial U/S
Low frequency curvilinear transducer
Transverse (horizontal)
Midline view
Identify spinous processes “unicorn or traffic cone”
Then move up to down to locate BATMAN sign
Measure distance (depth) to ligamentum flavum
Esters
Procaine
Chloroprocaine
Tetracaine
Amides
Lidocaine
Mepivacaine
Ropivacaine
Bupivacaine
How to administer neuraxial injection?
Only after negative aspiration
NEVER MORE THAN 3-5mL
Local Anesthetic Dosing
Based on Spinal Levels
Caudal 2mL/segment
Lumbar 1mL/segment
Thoracic 0.7mL/segment
Epinephrine
α1 agonist
1:200,000 (indicates gram per mL = 5mcg/mL)
Prolongs DOA w/ short-acting LAs
Greatest effect w/ Tetracaine
Clonidine
NOT vasoconstrictor
Selective α2 agonist
Used when Epi contraindicated
Synergistic effects when mixed w/ Lidocaine or Bupivacaine (labor analgesia)
Central action appears to help w/ tourniquet pain (ortho surgeries)
Epidural Fentanyl
High lipid solubility
PK/PD similar to systemic administration
Provides profound analgesia
Dose: 50-100mcg
Onset: 3-5min
DOA: 1-2hrs
Epidural Morphine
Highly polarized, not very lipid soluble
PK/PD similar to systemic admin
Provides profound analgesia
Dose: 2-4mg
Onset: 10-15min
DOA: 8-10hrs
Adverse effects - itching & urinary retention
Patient Controlled Epidural
Low concentration infusion + additive
Able to inject additional LA
GOAL
Block A delta & C fibers
Nerve Block Onset
B → A delta & C → A gamma → A beta → A alpha
B Fiber Block
Pre-ganglionic autonomic vasomotor
Diameter < 3μm
Light myelination
Onset = early
Rapid 1st sympathetic Hypotension r/t level T4 = cardiac accelerator fibers 1st sign ↓BP followed by N/V Typically N/V 1st patient noted sign → cycle BP cuff
A Delta & C Fibers
Pain & temperature
Unable to discriminate light touch or temperature
Temperature discrimination mirrors sensory loss
A Delta
- Pain, cold temperature, touch
- 1-5μm
- Heavy myelination
- Intermediate block onset
C Fibers
Sympathetic:
- Post-ganglionic vasomotor
- 03-1.3μm
Dorsal root:
- Pain, warm & cold temperature, touch
- 0.4-1.2μm
Both:
- No myelination
- Early block onset
A Fibers
Alpha, Beta, & Gamma
Last fibers to be blocked
- Touch & proprioception
- Surgical muscle relaxation
- Able to feel pressure
A Alpha
Proprioception, motor
6-22μm
Heavy myelination
Onset = last
A Beta
Touch, pressure
6-22μm
Heavy myelination
Intermediate onset
A Gamma
Muscle tone
3-6μm
Heavy myelination
Intermediate onset
Evaluation
Assess the block every ___ minutes
2-3 minutes
Vital signs & blood pressure
How to manipulate the LA spread?
Adjust the OR table level
Trendelenburg or reverse
Local anesthetic baricity impact compared to CSF specific gravity
Physiologic Alterations
Dependent on block level
Assess dermatomes & sensory changes
Manipulation to LA spread via positioning
Elevate HOB to prevent cephalad spread & post-dural puncture headache
Autonomic blockade usually 2 dermatome levels higher than sensory block level
Motor block upper limit usually 2 levels below the sensory block
Epidural/Spinal Complications
Hypotension Intercostal muscle paralysis Apnea/phrenic nerve paralysis Paresthesias Subarachnoid or epidural hematoma Infections: - Meningitis/epidural abscess - Chemical meningitis - Prevention = proper sterile technique Cauda equina syndrome Transient neurological symptoms New nervous system lesion Exacerbation pre-existing neurological disease N/V Urinary retention Post-dural puncture headache
Post-Dural Puncture Headache
Results d/t dura compromise
Obvious or following uncomplicated procedure
Risk factors - needle size/type & patient population (younger, female, & pregnancy)
PDPH S/S
Bilateral frontal or retroorbital or occipital headache
Extends into neck
Photophobia
Nausea
Positional - headache relieved when supine
S/S exacerbated when upright
PDPH Treatment
1st 12-24hrs conservative
- Recumbent position (supine)
- Analgesics
- Fluid admin
- Caffeine
- Stool softeners & soft diet (to prevent straining)
Epidural blood patch
- Inject 15-20mL autologous blood (obtain simultaneously w/ sterile procedure)
- Admin 1-2 levels below initial puncture site
- 90% respond to initial therapy
Cauda Equina Syndrome
PERMANENT neurological deficits
Results in bowel and/or bladder dysfunction, perineal sensory loss, & variable extremity paresis
Onset usually immediate after causative injury
1991 microcatheters r/t large amounts concentrated LA pooling at the lumbosacral roots → excessive exposure & toxic effects
Treatment = supportive
TNS
Transient neurologic symptoms
1993 after single-dose spinal anesthesia
NOT permanent deficit (transient)
Temporary symptoms appear 1-24hrs after spinal anesthesia resolution
Disappears w/in 10 days
Pain syndrome (no bowel or bladder dysfunction)
Back pain, weakness/numbness radiating one or both buttocks or legs, & thighs
Lidocaine more neurotoxic than Bupivacaine or Tetracaine
Contributing factors - lithotomy position or hip/knee bent (thought to be r/t LAs pooling & lumbosacral nerve roots stretching)
Spinal Anesthetic
REVERSIBLE neuronal transmission blockade produced via LA injection into the CSF
Subarachnoid or intrathecal block
Temporary interruption autonomic, sensory, & motor nerve fiber transmission (ventral & dorsal nerve roots)
August Bier
Performed the first spinal anesthetic 1898
Injected 15mg cocaine intrathecally
Spinal Advantages
Ideal technique for lower abdomen & caudal procedures
Simple & versatile
- Able to control block distribution
- Use w/ or w/o adjunct anesthesia
↓surgical stress
↓blood loss - controversial d/t hypotension
↓DVT risk r/t coagulation cascade
Postop analgesia
Awake patient - no LOC
Full stomach (non-compliant NPO or delayed gastric emptying)
↓PONV, sedation, cognitive impairment, & surgical pain
Spinal Technique Selection
Indications & Patient Considerations
Procedures involving lower extremities or lower abdomen
Patients with pulmonary disease (avoid negative pulmonary effects associated w/ general anesthesia)
Preop assessment
Address any patient concerns
Plan B = general anesthesia
Spinal Indications
Full stomach Difficult airway Minimal metabolic impact - liver or kidney disease or diabetes ↓systemic blood pressure - Risk venous thrombosis & blood loss
Aortic Valve Stenosis
MILD
Jet velocity <3m/sec
Mean gradient <25mmHg
Valve area >1.5cm^2
Aortic Valve Stenosis
MODERATE
Jet velocity 3-4m/sec
Mean gradient 25-40mmHg
Valve area 1-1.5cm^2
Aortic Valve Stenosis
SEVERE
Jet velocity >4m/sec
Mean gradient >40mmHg
Valve area <1cm^2
Aortic Valve Stenosis
CRITICAL
Jet velocity >5m/sec
Mean gradient >80mmHg
Valve area <0.7cm^2
Other Epidural/Spinal Considerations
Previous back surgery
Inability to communicate w/ patient
Complicated surgical procedures - long duration, major blood loss, or respiratory compromise
Local anesthetic allergy (amide vs. ester)
Untreated HTN
Major surgery above the umbilicus d/t blockade level (motor vs. sensory)
Dural Puncture (Spinal) Location
Anywhere from L2 → S1
Spinal cord ends at L1 in adults
Most common location L3-L4 interspace
Procaine
Ester pKa 8.9 Ionized 97% Protein binding 6% Onset - slow DOA 60-90min
Chloroprocaine
Ester
Onset - fast
DOA 30-60min
Tetracaine
Ester pKa 8.5 Ionized 93% Protein binding 94% Onset - slow DOA 180-600min
Lidocaine
Amide pKa 7.9 Ionized 76% Protein binding 64% Onset - fast DOA 90-120min
Mepivacaine
Amide
Onset - fast
DOA 120-240min
Ropivacaine
Amide
Onset - slow
DOA 180-600min
Bupivacaine
Amide pKa 8.1 Ionized 83% Protein binding 95% Onset - slow DOA 180-600min
Baricity
Resting position of two fluids w/ different specific gravities when mixed in single container
Pertaining to spinal anesthetics & baricity hyper/iso/hypo vs. CSF
CSF Specific Gravity
1.003-1.009
Denser than water
Isobaric
LA = baricity as CSF
Normal saline or CSF
Hyperbaric
LA heavier (more dense) than CSF Dextrose
Hypobaric
LA lighter (less dense) than CSF Sterile water
Anesthetic Level Factors
BARICITY *spinal only* Patient position Drug dosage Injection site Patient height - Short ↓LA dose/volume - Tall ↑dose/volume Pregnancy - epidural vein engorgement CSF volume Spine curvature Drug volume Intra-abdominal pressure Needle direction
Most Dependent Spinal Area
T4-T8
Hyperbaric solutions mitigate here most when patient supine
Spinal Procedure
- Verify patient, patent IV, monitors attached & functioning, resuscitation equipment available
- Inform patient about procedure & steps involved
- Properly position patient at comfortable level
- Palpate & identify landmarks
- STERILE procedure (hat, mask, & sterile gloves)
- Open tray
- Cleanse injection site & allow to dry completely
- Set-up tray & draw up meds
- Apply sterile drape
- Re-position patient & identify injection site
- Inject local anesthetic 25-27G
- Place introducer needle
- Pass spinal needle through the introducer
- Advance through posterior ligaments
- Utilize non-dominant hand to stabilize needle
- Remove stylet & observe clear CSF flow
- Connect LA syringe, aspirate to confirm CSF (distinct swirl noted), inject LA
- Removed syringe, needle, & introducer together in one smooth motion
- POSITION
Spinal Bilateral Block
Return patient to supine position immediately
Slightly elevate HOB to prevent PDPH
Spinal Unilateral Block
Leave patient in lateral position at least 3 MIN prior to returning to supine position
Slightly elevate HOB to prevent PDPH
Spinal Needles
Cutting vs. pencil point
Quincke 25G (cutting)
- Orient bevel to the side ↓tissue trauma
- Dural trauma more common
Sprotte 25G or Whitacre 25G (pencil point or blunt tip)
- Separates the tissues
SPINAL Trouble Shooting
Absence CSF
Reinsert stylet
Slowly advance needle 1-2mm
Attempt to aspirate CSF
Repeat steps until obtain CSF
Advance needle additional mm after puncture to ensure complete dura puncture (especially w/ pencil point needles)
Traverse the dura - remove stylet & attach syringe, gently aspirate as withdraw needle, as needle tip withdrawn into subarachnoid space may obtain CSF
↑risk PDPH
SPINAL Trouble Shooting
Blood-Tinged CSF
FRANK blood - Does not clear - Needle tip likely w/in an epidural vein - Withdraw & reposition Blood-tinged CSF - Allow CSF to flow for several seconds - Inject medication when CSF clear
SPINAL Trouble Shooting
Paresthesia
STOP
Leave the needle & stylet in place
Paresthesia resolves then continue w/ the injection
Does not resolve then remove & reposition the needle
Sensory Blockade at T10
AUTONOMIC
Autonomic blockade 2 dermatome levels HIGHER
→ T8
Cardio-accelerator fibers at T4
Autonomic blockade >T4 → systemic hypotension
Sensory Blockade at T4
MOTOR
Motor blockade usually 2 levels BELOW the sensory block → T6
Saddle Block
S2-S5
Surgery limited to perineum, perianal region, or genitalia
Little autonomic effect
Low Spinal
T10
Low abdominal procedures & lower extremity vascular & orthopedic
Block lower lumbar & sacral roots
High Spinal
C8
Block higher than T2
Undesirable effect → unable to ventilate
Most Common Spinal
T4
Abdominal & lower extremity procedures
Obese Patients
Spinous processes more difficult to palpate
- Adipose tissue distorts anatomic landmarks
Sitting position provides more flexion
ULTRASOUND
Paramedian Approach
When patient unable to flex spine - previous spinal surgery, rheumatoid arthritis, or trauma to hip or upper leg
Place skin wheal 1cm lateral & 1cm caudal to spinous process
Advance needle toward midline
- Needle passes through paraspinous muscles to ligamentum
- Does NOT pass through supraspinous or interspinous ligaments
- Ligamentum flavum = 1st encountered ligament
Lumbosacral Approach
Modified paramedian approach
L5 → S1 interspace
Identify posterior superior iliac spine
Skin wheal 1cm medial & 1 cm caudal to the spine
Needle insertion 45-55° medial & cephalad to the dorsal sacrum surface toward the lumbosacral foramen midline
Continuous Spinal
Prolonged surgical anesthesia & postop pain
Dura punctured w/ 17G epidural needle
Epidural catheter passed through dura into subarachnoid space
Small, incremental doses LA admin until desired level achieved
- Slows hypotension onset
- Total dose to achieve the desired level = same
Consider using wet tap occurs when placing an epidural
LA Metabolism
Little to no metabolism in CSF
Absorbed into plasma & metabolized based on physiochemical properties (esters plasma esterases via hydrolysis; amides hepatic CYP require transport to liver)
+ vasoconstrictors slows the absorption & prolongs the block
Phenylephrine
Pure α adrenergic agonist
Slightly more effective than Epi
Greatest effect w/ Tetracaine
Intrathecal Opioids
PRESERVATIVE FREE
Synergism b/w opioids & local anesthetics
Provide better analgesia together rather than alone
Fentanyl & Morphine
Spinal Fentanyl
High lipid solubility
- Binds directly to spinal cord lipid elements
- Less drug available to diffuse systemically
Provides profound analgesia
Dose: 12.5-25mcg mixed w/ LA
Onset: 5-10min
DOA: 2-4hrs
Spinal Morphine
Highly polarized, not very lipid soluble
- Drifts feely in CSF
- Approximately 6-8hrs rises to respiratory center
Provides profound analgesia
Dose: 0.1-0.25mg
Onset: 60-90min
DOA: 24hrs
Adverse effects - itching, urinary retention, & delayed respiratory depression
Documentation
Informed consent
Oxygen & monitors applied
Baseline vital signs
Patient properly positioned
Prepping & draping performed in sterile fashion
Desired interspace identified
Skin wheal subcutaneous LA (amount mL)
Introducer placed w/ spinal needle passed through
Positive clear CSF noted (negative for blood or paresthesias)
Dose LA as well as any other adjuncts
Patient placed in desirable surgical position
Final dermatome level achieved
