29204136 epidural and spinal anesthesia

7/31/2019 29204136 Epidural and Spinal Anesthesia

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DEPARTMENT OF ANESTHESIA

OSPITAL NG MAYNILA MEDICAL CENTER


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EPIDURAL AND SPINAL

ANESTHESIA

No absolute indications

Clinical situations, patientphysiology, surgical procedure:

makes central neuraxial block

the technique of choice


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EPIDURAL AND SPINAL

ANESTHESIA

Blunt the stress response tosurgery

decrease intraoperative blood loss

lower the incidence ofpostoperative thromboembolic

eventsdecrease morbidity and mortality

in high-risk surgical patients


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extend analgesia into thepostoperative period

(provide better analgesia thancan be achieved with parenteral

opioids)

provide analgesia to non-

surgical patients


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VERTEBRAE

The spine consistsof 33 vertebrae

7 cervical

12 thoracic

5 lumbar

5 fused sacral

4 fused coccygeal


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Cervical (except C1),thoracic, and lumbarvertebrae: bodyanteriorly, twopedicles that projectposteriorly from thebody, and two laminaethat connect thepedicles ----form the

vertebral canal, whichcontains the spinalcord, spinal nerves,and epidural space


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Lamina: give rise to the

transverse processes (laterally);

spinous process (posteriorly) ---sites for muscle and ligament

attachments

Pedicles: contain a superior and

inferior vertebral notch through

which the spinal nerves exit the

vertebral canal


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5 sacralvertebrae fused

to form the

wedge-shapedsacrum (connectsthe spine with the

iliac wings of the

pelvis)

5th l


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5th sacralvertebra (not fusedposteriorly) give riseto a variablyshaped opening ---- sacral hiatusopening into thesacral canal(caudaltermination of theepidural space)

Sacral cornu

bony prominences on either side of thehiatus

aid in identification of sacral hiatus


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Coccyx fused 4 rudimentary coccygeal vertebrae

a narrow triangular bone that abuts the

sacral hiatus


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Tip of the coccyxcan often be

palpated in the

proximal gluteal

cleft and by runningones finger

cephalad along its

smooth surface, the

sacral cornu can beidentified at the 1st

bony prominence

encountered


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C7: 1st prominentspinous processencountered whilerunning the hand downthe back of the neck

T1 : most

prominentspinous process

T12 : can beidentified by

palpating the12th rib andtracing it back toits attachementto T12

Line drawn betweenthe iliac crests:

body ofL5 or the 4-5inters ace


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LIGAMENTS

Vertebralbodies arestabilizedby 5ligaments

thatincreasein sizebetweenthecervicalandlumbarvertebrae


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EPIDURAL SPACE

Space that lies between the spinal

meninges and the sides of thevertebral canal

Boundaries:

Cranially: foramen magnum

Caudally: sacrococcygeal ligament

covering the sacral hiatus

Anteriorly: posterior longitudinal ligamentLaterally: vertebral pedicles

Posteriorly: ligamentum flavum and

vertebral lamina


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Not a closed space butcommunicates with the

paravertebral space by way of the

intervertebral foramina Shallowest anteriorly where the

dura may in some places fuse with

the posterior longitudinal ligament Deepest posteriorly


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Composed of a series ofdiscontinuous compartments that

become continuous when the

potential space separating thecompartments is opened up by

injection of air or liquid


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MENINGES

Spinal meninges consist of 3protective membranes :

Dura mater

Arachnoid materPia mater


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Dura mater

Outermost and thickest meningeal

tissue

Begins at the foramen magnum;ends at approx S2 where it fuses

with the filum terminale

Inner surface abuts the arachnoidmater


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Arachnoid mater

Delicate, avascular membranecomposed of overlapping layers offlattened cells with connective

tissue fibers running between thecellular layers

Specialized connections (tight

junctions and occluding junctions)account for the fact that it is thephysiologic barrier for drugs movingbetween the epidural space and the

spinal cord


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Subarachnoid space lies betweenthe arachnoid mater and the piamater and contains the CSF

Spinal CSF is in continuity with thecranial CSF and provides an avenuefor drugs in the spinal CSF to reach

the brain Spinal nerve roots and rootlets runin the subarachnoid space


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Pia mater Adherent to the spinal cord and is

composed of a thin layer of

connective tissue cells interspersed

with collagen

Extends to the tip of the spinal cord

where it becomes the filum

terminale, which anchors the spinal

cord to the sacrum

Gives rise to the dentate ligaments


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NEEDLES


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NEEDLES

Spinal NeedlesWhitacre and

Sprotte:

pencil-point tip needle hole on the

side of the shaft

Greene and Quincke:

beveled tips with

cutting edges


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Spinal Needles

* pencil-point

needles requiremore force to insert

than the bevel-tip

needles but provide

better tactile feel;

not deflected* Size: 22-29 gauge larger

gauge smaller diameter

Epidural Needles


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Epidural Needles

Touhy: curved tip to

help control the

direction that the

catheter moves in

the epidural space

Hustead: lesscurved tip

Crawford: straight;

less suitable forcatheter insertion

*sizes: 16-19 gauge


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SEDATION Light sedation before placement of block

Successful spinal and epidural anesthesiarequires patient participation to:

maintain good position

evaluate block height

indicate paresthesias if needlecontacts neural elements

properly evaluate an epidural test

Once the block is placed and adequateblock height assured, patient can besedated as deemed appropriate


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SPINAL ANESTHESIA

POSITION

Patient positioning is critical to

successful spinal puncture

lateral decubitus

sitting position

prone jackknife position


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POSITION

Lateral decubitus

patient lies with the operative side

down (hyperbaric LA)

or with operative side up (hypobaric

LA) ---most dense block occurs on

the operative side


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POSITION

back at the edge of the table

patients shoulders and hips

positioned perpendicular to the bed

knees drawn to the chest; neck

flexed; patient instructed to curve

the back outward


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MIDLINE APPROACH

Skin overlying the desired

interspace is infiltrated with a small

amount of LA (1-2 ml) to a depth of1-2 inches to prevent pain when

inserting the spinal needle

Slight cephalad angulation (10-15degrees)


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MIDLINE APPROACH

Needle is then advanced subcutaneous tissue

supraspinous ligament interspinous ligament

ligamentum flavum

epidural space

dura mater

arachnoid mater


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MIDLINE APPROACH


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MIDLINE APPROACH

Penetration of the dura mater produces

a subtle pop

detection of dural penetration

prevent inserting the needle all the way

through the subarachnoid space and

contacting the vertebral body;

insert spinal needle quickly withouthaving to stop every few mm and remove

the stylet to look for CSF at the needle


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MIDLINE APPROACH

Once the needle tip is believed to be in

the subarachnoid space, stylet is

removed to see if CSF appears at the

needle hub

Small diameter needles (26-29 gauge)

requires 5-10 sec or >/= 1 minute

Failure to obtain CSF suggests thatthe needle orifice is not in the

subarachnoid space and must be

reinserted


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MIDLINE APPROACH

Once the needle is correctly inserted

into the subarachnoid space, it is

fixed in position and the syringe

containing LA is attached

CSF is gently aspirated to confirm that

the needle tip remained in the

subarachnoid space and LA slowlyinjected (


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MIDLINE APPROACH

After completing the injection, a

small volume of CSF is again

aspirated to confirm that the needletip remained in the subarachnoid

space while the LA was deposited

This CSF is then reinjected and theneedle, syringe, and any introducer

removed together as a unit


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MIDLINE APPROACH

strict attention to patients

hemodynamic status with BP and/or

HR supportedblock height should also be assessed

early

pin pricktemperature sensation

Table may be tilted as appropriate toinfluence further spread of localanesthetics


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PARAMEDIAN APPROACH

useful in situations where the

patients anatomy does not favor

the midline approachinability to flex the spine

heavily calcified interspinous ligaments

Patient in any position; bestapproach for the patient in the

prone jackknife position


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PARAMEDIAN APPROACH Identify the spinous process forming

the lower border of the desired

interspace Needle inserted

~1 cm lateral

directed toward middle of the

interspace ~45 degrees cephalad

medial angulation (~15 degrees) tocompensate for the lateral insertionpoint


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PARAMEDIAN APPROACH

Needle inserted ~1 cm lateral, directed toward middle of theinterspace ~45 degrees cephalad with just enough medial angulation(~15 degrees) to compensate for the lateral insertion point


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PARAMEDIAN APPROACH1st significant resistance encountered:

ligamentum flavum

Alternative method:

insert needle perpendicular to the skin in all

planes until the lamina is contacted; needle is

then walked off the superior edge of the lamina

and into the subarachnoid space

**Lamina provides a valuable landmark that

facilitates correct needle placement

EPIDURAL ANESTHESIA


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EPIDURAL ANESTHESIA

May be performed at

any intervertebral

space

LA skin wheal is

raised to the point ofneedle insertion

Pierce the skin with a

>/=18 G hypodermicneedle


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Epidural needle

inserted through

the subcutaneous

tissue and into the

interspinousligament gritty

feel

Needle is advanced

slowly until an

increase in

resistance is felt :


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Techniques toidentify epidural

space:Loss of resistance

technique(fluid/air)

Glass syringe: 2-3ml saline + 0.1-0.3ml air bubble

Hanging drop

technique


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After entering the epidural space,stop advancing the needle

heightens the risk of meningeal

puncture wet tap LA test dose should be administered

to help rule out undectected

subarachoid or IV needle placement After a negative test dose, desired

volume should be administered in

small increments


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EPIDURAL TEST DOSETo identify epidural needles or

catheters that have entered an epiduralvein or the subarachnoid space

Failure to perform: IV injection or totalspinal block

3 ml of LA + 1:200,000 epinephrine IV: epinephrine

HR increases 20-40 sec after

BP increase of >/=20 mmHg

Subarachnoid: motor block ---LA


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Spinal anesthesia interrupts sensory,motor, and sympathetic nervous system

Classic concept:Conduction blockade through small diameter

unmyelinated (sympathetic) fibers beforeinterrupting conduction via large myelinated(sensory & motor) fibers


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Block of afferent impulses from thesurgical site leads to absence of

adrenocortical response to pain


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Vasodilatation of resistance and

capacitance vessels occurs:

hypovolaemia, tachycardia, drop in blood

pressure

exacerbated by blockade of the

sympathetic nerve supply to the

adrenal glands, preventing the releaseof catecholamines.

Bradycardia: If blockade is as high as T2,

sympathetic supply to the heart (T2-T5)


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overall result: inadequate perfusion ofvital organs

measures: restore blood pressure and

cardiac output (fluid administration,

vasoconstrictors)

Sympathetic outflow extends from T1 - L2

(blockade of nerve roots below this level,

knee surgery, is less likely to causesignificant sympathetic blockade,

compared with procedures requiring

blockade above the umbilicus)


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usually unaffected unless blockade is

high enough to affect intercostal muscle

nerve supply (thoracic nerve roots)

leading to reliance on diaphragmaticbreathing alone

distress to the patient, as they may feel

unable to breathe adequately

decreased ability to cough and expel

secretions

if patients cannot breathe, ventilate (face

mask and bag


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Blockade of sympathetic outflow (T5-L1),

leads to predominance of

parasympathetic (vagus and sacral

parasympathetic outflow)

leading to active peristalsis and relaxed

sphincters, and a small, contracted gut, which

enhances surgical access

Splenic enlargement (2-3 fold) occurs


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If above T5, inhibits sympatheticinnervation to the GIT, resulting in

unopposed parasympathetic nervous

system activity

Contracted intestines and relaxed sphincter;

if not on NPO, tendency to develop vomiting


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urinary retention is a common problem

severe drop in blood pressure may affect

glomerular filtration in the kidney (ifsympathetic blockade extends high

enough to cause significant

vasodilatation)

ureters are contracted and ureterovesicalorifice is relaxed


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Decreased bleeding may be areflection of decreased BP

Increased blood flow to lower

extremities ---- decreased incidenceof thromboembolism


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BLOCK HEIGHT

Perianal

Perirectal

L1-2 Hyperbaric/sitting pos

Hypobaric/jackknife pos

Lower extremity/

Hip

TURP

Vaginal/ cervical

T10 Isobaric

HerniorrhaphyPelvic procedures

Appendectomy

T6-8 Hyperbaric/ horizontal

Abdominal

Cesarean section

T4-6 Hyperbaric/ horizontal

FACTORS THAT AFFECT SPREAD OF


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LOCAL ANESTHETIC SOLUTIONS

Characteristics of the local anesthetic

solution ratio of density (mass/vol) of LA div

density of CSF

Local anesthetic dose

Local anesthetic concentration

Volume injected

Patient characteristics

Age

WeightHeight

Gender

Pregnancy

Patient position

FACTORS THAT AFFECT SPREAD OF


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LOCAL ANESTHETIC SOLUTIONS

Technique

Site of injection

Diffusion

Speed of injection

Barbotage

Direction of needle bevel

Addition of vasoconstrictors

LOCAL ANESTHETIC


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SOLUTION

HYPERBARIC: solution more dense thanCSF; >/=1.0015Add glucose (5-8% dextrose) of increase the

density

LA solution settles to dependent region HYPOBARIC: solution less dense than

CSF;


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Hypotension Postdural puncture headache

Hearing loss

Total spinal

Backache

nausea

Urinary retention

Systemic toxicity Neurologic injury

Spinal hematoma


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HypotensionDue to sympathetic nervous system

blockade

a.Decreased venous return to heart,decreased cardiac output

b.Decreased systemic vascular

resistance

c.Bradycardia due to blockade of

cardioaccelerator fibers (T1-3),

decreased cardiac output


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HypotensionTreatment: restore venous return to

incrase cardiac output

Position head-down: autotransfusionHydration before spinal anesthesia

Sympathomimetics


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Postdural puncture headacheFrontal/occipitalWorsened by sitting, improved by supine

position

Due to decreased CSF pressure and resulting

tension on meningeal vessels and nerves as aresult of leakage of CSF through the duralhole

Diplopia due to traction on abducens nerve

Treatment: bed rest, analgesics

Hydration (>/= 3L/day) to increase CSF production Epidural patch (10-20 ml) to seal dura

Caffeine-sodium benzoate (by vasoconstriction)

Hearing loss


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High Spinal Undesired excessive level of sensory

and motor anesthesia associated with

difficulty of breathing or apnea ---arterial hypoxemia or hypercarbia

Apnea reflects ischemic paralysis of

medullary ventilatory centers due to

profound hypotension and associatedwith decreased cerebral blood flow


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High Spinal Treatment: support breathing and

circulationa.Positive pressure ventilation with face

maskb.IVF and sympathomimetics

c.Head down to increase venous return

(head up will jeopardize cerebral blood flow --

- medullary ischemiad. Intubation of trachea in those at risk for

aspiration


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rare complication

profound hypotension

apneaunconsciousness

dilated pupils as a result of the action

of local anesthetic on the brainstem


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Airwaysecure, administer 100% oxygen

Breathing - ventilate by facemask, intubate

Circulation - treat with iv fluids and

vasopressorContinue to ventilate until the block wears off

(2 - 4 hours)

As the block recedes the patient will begin

recovering consciousness followed bybreathing and then movement of the arms and

finally legs. Consider some sedation

(diazepam 5 - 10mg i/v) when the patient

begins to recover consciousness but is still

intubated and requiring ventilation


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Backache May be related to position required for

surgery

More likely due to ligamentous strainwhen in an uncomfortable position


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Nausea May be due to hypotension --- cerebral

ischemia; tx sympathomimetics

May be due to predominance ofparasympathetic nervous system

activity; tx atropine 0.4 mg IV


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Urinary RetentionBecause spinal anesthesia interferes

with innervation of the bladder

Administration of large amounts of fluid--- bladder distention requiring catheter

drainage

Systemic toxicity


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Neurologic injuryVery rare due to small dose of LA

employed

In the absence of hematoma orabscess, treatment is symptomatic

Spinal hematoma

Rare; present with numbness or LE

weakness

Risk factor: coagulation defects


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due to an excessively large dose of

local anesthetic

hypotension, nausea, sensory loss orparesthesia of high thoracic or even

cervical nerve roots (arms), or difficulty

breathing

most severe cases may requireinduction of GA with securing of the

airway, while treating hypotension


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If patient has a clear airway and isbreathing adequately: reassurance and

any hypotension immediately treated

Difficulty in talking (small tidal volumes

due to phrenic block) and drowsiness

are signs that the block is becoming

excessively high and should be

managed as an emergency


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excessive dose of local anaesthetic

moderate dose of LA, injected directly

into a blood vesselepidural catheter is inadvertently

advanced into one of the many epidural

veins. It is therefore vital to aspirate

from the epidural catheter prior toinjecting local anaesthetic


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symptoms: light-headedness, tinnitus,

circumoral tingling or numbness and a

feeling of anxiety or "impending doom",

followed by confusion, tremor,

convulsions, coma and CPR arrestearly recognition: discontinue further

administration of local anesthetic

drugs

treatment: supportive,sedative/anticonvulsants,

cardiopulmonary resuscitation if

required


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Patient refusal: only absolute contraindication Conditions that increase the apparentrisk of central neuraxial block- Hypovolemia or shock increase the risk of

hypotension

- Increased ICP increases the risk of brainherniation when CSF is lost through theneedle, or if a further increase in ICP followsinjection of large volumes of solution into theepidural or subarachnoid spaces

- Coagulopathy or thrombocytopenia increasethe risk of epidural hematoma

- Sepsis increases the risk of meningitis

- Infection at the puncture site increases therisk of meningitis


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Pre-existing neurologic disease(multiple sclerosis) : considered CI

No evidence to suggest that spinal or

epidural anesthesia alters the course ofany preexisting neurologic disease

Recommendations to avoid RA stem

largely from a medicolegal concern

that the anesthetic may be incorrectlyblamed for any subsequent worsening

of the patients preexisting condition

SPINAL OR EPIDURALANESTHESIA?


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ANESTHESIA?

Spinal AnesthesiaLess time to

perform

Produces morerapid onset of

better quality

sensorimotor

blockLess pain during

surgery

SPINAL OR EPIDURALANESTHESIA?


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ANESTHESIA?

Epidural Anesthesia

Lower risk of PDPH

Less hypotension if epinephrine is notadded to the LA

Ability to prolong or extend the block

via an indwelling catheter

Option of using an epidural catheter to

provide postoperative analgesia


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29204136 epidural and spinal anesthesia

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