SPINAL & EPIDURAL

ANESTHESIA

Spinal Column Anatomy Vertebra

Vertebral Body Pedicles Anterior (2)

& Laminae Posterior (2)

Transverse Process – Junction of the Pedicles and Laminae

Spinous Processes – Joining of the Laminae

Intervertebral Disks

ADVANTAGES OF SPINAL/EPIDURAL ANESTHESIA

Avoids Hazards of General Anesthesia

Patient is Alert earlier postoperative

Lower incidence of Nausea/Vomiting

Better Pain Control/Less Narcotics

SPINAL ANESTHESIA Indications

Best reserved for operations below the level of the umbilicus R/LIH, GYN, Peroneal, Anal, LE’s C-sections

Preferable to Epidural & GA Risk/Benefit Ratio

Contraindications Refusal Infection Severe Neurological Disease Hypovolemia Coagulopathy

LMWH use?

LMWH & NEURAXIAL BLOCKADE Overall incidence of Spinal Hematoma

Estimated < 1/220,000 – SABEstimated < 1/150,000 - CLE

Benefit/Risk Ratio Recommendations

LMWH & NEURAXIAL BLOCKADE

RECOMMENDATIONS

*

SPINAL ANESTHESIA A single injection of a local anesthetic

solution into the subarachnoid space usually at the lumbar level Intrathecal Narcotics

Commonly at L3-L4 Largest Interspace

L5-S1

SPINAL NEEDLE CONSIDERATIONS Small needles PDPH Large needles improve

tactile sensations Pencil-point needles

PDPH riskFurther reduction with

addition of ITN Side injection needles

with large holes CSF but careful to have entire hole subarachnoid

MOST IMPORTANT FACTORS AFFECTING BLOCK HEIGHT - SAB Baricity of anesthetic solution Position of the patient

During injection Immediately after injection

Drug Dosage (mg)Concentration times volumeAddition of Opioids

Site of Injection

ADDITIONAL FACTORS TO CONSIDER WITH SAB HEIGHT Patient Age

Elderly patients > 80 yrs Patient Height Intra-abdominal Pressure

Pregnancy & Obesity Drug Volume

FACTORS UNRELATED TO SAB HEIGHT Added Vasoconstrictor Rate of Injection

Except for Hypobaric Gender

Females < Males Pregnant versus Non-pregnant

Weight Increased Weight

Lesser concentration needed?

DIFFERENTIAL BLOCK WITH SAB

Sympathetic Block2-6

dermatomes higher than the sensory block

Motor Block2 dermatomes

lower than sensory block

SensoryMotor

SympatheticT5

BARICITY OF LOCAL ANESTHETICS Isobaric – Stays where you put it

LA has the same density or specific gravity as CSF (1.003-1.008) – Normal Saline

Hypobaric – “Floats” up – Lighter than CSFLA has a density or specific gravity that is less than

CSF (<1.003) – Sterile Water Hyperbaric – Settles to Dependent aspect of the

subarachnoid space – Heavier than CSFLA has a density or specific gravity that is greater

than CSF (>1.008) - Dextrose

POSITIONING THE PATIENT

Sitting With Legs hanging over side of bed

Have the patient hug a pillow Put Feet up on a Stool (no wheels) Assistant MUST keep the patient from Swaying Curve her back like a “C”, Halloween Cat,

Shrimp, Cannon ball Up in the Bed (quicker but not optimal) Baricity?

Lateral Decubitus (Left or Right?) Needs to be Parallel to the Edge of the Bed Legs Flexed up to Abdomen Forehead Flexed down towards Knees

Jack-knife Position Chosen for ano-rectal surgery CSF will not drip from hub of needle Use hypobaric solution

Bupivacaine less run-off than lidocaine

PREPARATION FOR SAB

Identify Suitable Patients Equipment Required

Single-shot or Catheter Placement Continuous spinal with epidural catheter

Know your Spinal/Epidural Kit Determine Insertion Approach

MidlineParamedian

MIDLINE INSERTION APPROACH Midline

Most commonly used As needle passes thru the

dura mater a “pop” is often appreciated

CSF flows thru once stylet is used For small gauge needles

(26-29 g) this may take 5-10 seconds May take even longer in

dehydrated or elderly patients

If no CSF flow, needle can be obstructed by a nerve root (rotate 90 degrees)

PARAMEDIAN (LATERAL) APPROACH After identifying the

proper interspace palpate the spinous process

Insert needle 1 cm lateral and 1 cm inferior to this point and direct needle towards interspace May need to walk medially

off of transverse process Ligamentum flavum is

usually the first resistance indentified Bypasses supraspinous

and intraspinous ligaments

Traditional

Taylor (L5-S1)

PREPARATION CONTINUED

GIVE INTRAVENOUS FLUID BOLUS OF 500 CC PRIOR TO SAB/EPIDURAL DOSE.

If it is not a labor epidural/c-section, give versed, fentanyl and oxygen prior to neuraxial anesthesia.Local Anesthetics to the skin, deep tissues?

Skin wheal should be performed at vertebral interspace (1-2 ml) and to adjacent sides (.5ml) with 1% Lidocaine

MOST COMMON CAUSES OF INADEQUATE SPINAL

ANESTHESIAUnable to locate CSF

Inability to enter SA space If bone (os) encountered superficially redirect needle cephalad If bone (os) encountered deep redirect needle caudally

Inability to aspirate CSF before injectionEnsure that you have CSF in all 4 planes

Surgery outlasting the drug selectedShort, intermediate & long term local anesthetics

Can increase duration & efficacy with opioids/LA admixture5-10 mcg fentanyl or 1-2 mcg sufentanil

Dose (mg) Duration T-10 T-4 Plain w/epi (0.2 mg)Lidocaine 30-50 mg 75-100 mg 45-60 min 60-90 minTetracaine 6-10 mg 12-15 mg 60-90 min 120-180 minBupivacaine 6-10 mg 12-15 mg 90 min 140 minRopivacaine 6-10 mg 12-15 mg 90 min 140 min

INTRATHECAL ANALGESIA

Drug DoseOnset (min)

Peak effect (min)

Duration (hrs) Advantage

sDisadvantag

es

Morphine 0.1-0.25 mg 30 60 12-24 Long

duration

Significant side effects; delayed respiratory depression; biphasic modality

Fentanyl 10-25 mcg 5 10 2-3 Rapid onset Short duration

Sufentanil 5-10 mcg

5 10 2-4Rapid onset; few side effects

Short duration; can see sinusoidal fetal HR; respiratory depression > fentanyl

Meperidine

10 mg 10 15 4-5Rapid onset; potentiation of spinal anesthesia

Nausea and vomiting; pruritis significant

METHODS OF DETERMINING SPINAL LEVEL

Definition of determining level: analgesia versus anesthesia

Alcohol skin wipe Pinch “toothpick” skin test Nerve stimulator Etc., etc., etc. Beware: break no skin, use no needles

STRATEGIES TO INCREASE THE LEVEL OF SPINAL ANESTHSIA IN THE PERI-

BLOCK FRAME

Work fast after local anesthetic injected Assess early and frequently Augment position changes to maximize spread

hyper / hypo baric solutions earlyCo-administration of IT Opioids

? Make patient cough several timesMore effective with lidocaine

ACTIONS TO DEAL WITH INADEQUATE LEVEL

Use previously discussed strategies Re-do spinal anesthetic Supplementation with local anesthetic per

surgeon Analgesic intravenous supplements Dissociative intravenous supplements General Anesthesia

A COMPARISON OF THREE ANESTHETIC TECHNIQUES FOR OUTPATIENT KNEE ARTHROSCOPY: GENERAL ANESTHESIA, SPINAL ANESTHESIA AND INTRAARTICULAR INFILTRATION OF LOCAL ANESTHETIC (2008)LT RILEY WILLIAMS, SRNA, LT ROBERT HAAG, SRNA, LT RODRIGO LOPEZ, SRNA, LT WILLIAM BAKER, SRNA, CDR LISA OSBORNE, CRNA, PHD AND CAPT (RET) JOSEPH PELLEGRINI, CRNA, PHD

Spinal Anesthesia Group 10-12 mg Hyperbaric Bupivacaine Supplemental Anxiolysis & fentanyl

Intraarticular Group IA Injection 15 min before incision by

anesthesia in holding Followed customized format

2-injection technique 20 ml Bupivacaine 0.5% with

epinephrine (1:200,000) Propofol Infusion

50-100 mg/kg/hr Fentanyl supplementation

50-100 mcg during injection with 2 mg midazolam

General Anesthesia Group Standardized Induction Desflurane or Sevoflurane

Time Requirements between Groups

Surgica

l Tim

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Anesth

esia

Time

TOTA

L Hospita

l Tim

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100

200

300

400

500

600SpinalIntraarticularGeneral

*Sig p < .05

*

Tim

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Min

utes

(Mea

n

SD

)

Time from Surgical Start toFirst Postoperative Analgesic Request

0100200300400500600700800

SpinalIntraarticularGeneral

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EPIDURAL ANESTHESIA Placement of Local Anesthetic into

epidural space

Dural Rent

EPIDURAL ANESTHESIA Indications

Contraindications Same as SAB ( ? Tattoos

Epidural blocks can be placed 4 hrs after last dose of SQ Heparin, 12 hrs after last dose of LMWH NSAIDS (including ASA) not contraindicated

Placement relatively safe with INR < 1.5

Orthopedic Major hip/knee surgery, pelvic fractures

OB/GYN C-section; laboring analgesia/female pelvic organs

Urology Prostate, bladder procedures

General Surgery*Thoracic vs Lumbar)

Upper & lower abdominal procedures* (height of block) Postoperative analgesia, combination with GA to reduce requirements

Pediatric Procedures(*usually through caudal)

Penile procedures, IHR, Ortho procedures; Postoperative analgesia, combination with GA to reduce requirements

Vascular Surgery Vascular reconstruction, amputations

Thoracic Surgery(*Thoracic epidural)

Postoperative analgesia, combination with GA to reduce requirements

Medical Conditions Known/suspected MH

EPIDURAL PLACEMENT Typically use Loss of Resistance Technique

Routinely placed in Lumbar region Use the needle for skin infiltration to identify

midline structures Insert the needle in a slightly cephalad direction

Dorsum of non-injecting hand rests on patient’s back

Thumb and index finger grasp hub of needle Seat needle into intraspinous ligament and

advance in slightly cephalad direction with continuous pressure on plunger of syringe and when the needle exits ligamentum flavum feel sudden loss of resistance The distance from skin to epidural space is

4-6 cm in 90% of the population Never change the direction of the needle tip

after it passes through the ligamentum flavum Do not advance the needle

Air versus Normal Saline Missed dermatomes Presence of parasthesias?

EPIDURAL PLACEMENT Thread catheter 3-5 cm

Check position Presence of parasthesias?

Remove needle while keeping positive pressure on catheter (thread concurrently) Check position

Secure catheter Check position

Test dose Aspirate for Blood or CSF

Off midline insertion usually results in higher blood vessel puncture A change of 20% or greater in HR after test dose indicates intravascular

injection (replace catheter) A dense motor block within 5 minutes after test dose indicates spinal block

(if positive either replace catheter or convert to continuous spinal technique)

Only give test dose after contraction is over in pregnant women If patient on beta blocker a change in systolic pressure > 20 mm Hg

indicates intravascular injection

1.5 % Lidocaine with epinephrine vs 2% Lidocaine

PROBLEM SOLVING WITH EPIDURAL PLACEMENTProblem Interpretation Reason Action

Needle floppy, angles laterally

Missed intraspinous ligament Entry off midline Reassess and redirect needle

Hit bone < 2 cm on insertion Hit spinous process Missed interspace; spine flexion inadequate

Identify interspace; redirect needle more caudal

Hit bone > 4cm or > Contacted lamina Needle entry too lateral Redirect more midline or use paramedian approach

Bony resistance all approaches

Arthritic spine & ligaments Ossification of ligaments Use paramedian approach

Cannot thread catheter Narrow epidural space; Missed epidural space, false loss of resistance

Space not dilatedEpidural needle too close to dura; catheter not in epidural space

Dilates space with 20 ml NSTry rotating the needle slightly to change bevel direction

Resistance to LA injection, difficulty passing catheter, clear fluid in catheter, cold fluid in catheter

Drip back of LA Cold fluid = LA; may be in subdural space

Can be widespread patchy block with hemodynamic stability; replace catheter and wait for resolution

Pain (parasthesia) with catheter insertion

Catheter near nerve root Approach too lateral; too much catheter in epidural space

If pain persists replace catheter; withdraw catheter if > 5 cm and reassess

Can’t palpate spinous process

Obesity or arthritis (obscuring spinous processes)

Obesity; severe arthritis Try midline approach for obeseUse 22 g needle to identify bony landmarksUse paramedian approach

LOCAL ANESTHETICS FOR EPIDURAL BLOCKADE

Drug Concentration (%) Onset(min)

Duration Plain/Epi

(min)2-Chloroprocaine

3 10-15 45-60/60-90

Lidocaine 2 10-15 80-120/120-180

Mepivacaine 1-2 15 90-160/160-200

Bupivacaine 0.25-.375 (*not surgical suitable)

0.5-.75 (*.75 -Not on OB)

15-20+

160-220/180+

Etidocaine 15-20 15-20 120-200/150+

Ropivacaine 0.5 – 0.75 15-20+

140-180/150+

Levobupivacaine

0.5 15-20 160-220/180+

EPIDURAL DOSING Volume is the key factor in determining height of blockade Typical loading dose is 10-20 ml given in 5 ml increments

Wait about 2-3 minutes between increments Use of epinephrine and bicarbonate will speed up onset on anesthesia If block incomplete after bolus replace catheter rather than wasting time giving

larger dose or re-positioning catheter Inject one-quarter to one-third of initial dose about 15 minutes after initial

bolus to enhance sensory blockade Cookbook guideline

To determine volume you can use the 5-foot rule Example: For an individual who is 5 feet in height you administer 1 ml of local anesthetic solution

for each segment requiring blockade and increase the volume by 0.1 ml for every 2 inches above 5 feet.

Example: For someone 5’10” in height and you enter at L3-L4 Interspace and want a to block up to T-6. 8 ml for L3-S5 and 7 ml for L2-T6 = 15 ml (base amount) Additional amount is 0.1 ml times 5 (10 inches/2) = 0.5 times 15 segments = 7.5

(supplemental amount) Overall add the 15 ml plus the 7.5 ml to get a dose of 22.5 ml

Need a total of 22.5 ml to achieve a T-6 level on a 70” person

EPIDURAL ADDITIVES Opioids

Morphine, Fentanyl, Sufentanil, Depo-Dur Depo-Dur Considerations

Clonidine Hemodynamic Considerations

Sodium Bicarbonate Speeds onset & Prolongs duration

COMBINED-SPINAL EPIDURAL (CSE) TECHNIQUE

CSE technique Allows for immediate relief of pain (from SAB) &

subsequent administration of medications via CLE for prolonged anesthesia

Advantages Reported to decrease failure rates of CLE (confirmation of

epidural placement) Clinical uses:

General Surgery Laboring analgesia & Cesarean Section High risk patients

Slower onset of sympathetic blockade Careful positioning during SAB with subsequent titration of CLE Administration of intrathecal opioids with small amount of

bupivacaine (2.5-5 mg) decreases epidural dosing requirements and decreases degree of sympathectomy

CSE TECHNIQUE

CSE TECHNIQUE CSE offers the advantages of both spinal and

epidural anesthesia CSE provides rapid onset and careful titration

Can use doses as low as 40 mg lidocaine or 7.5 mg bupivacaine Additional Opioids

Sufentanil Fentanyl Morphine

Potential disadvantages PDPHA Catheter migration into SA space Test Dose Transient parasthesias

Ideal length of spinal needle beyond epidural needle is 12-13 mm Longer spinal needles associated with higher incidence