DR I Noeth Department Anaesthesiology - PowerPoint Presentation

Slide1

DR I NoethDepartment AnaesthesiologySteve Biko Academic Hospital

REGIONAL ANAESTESIASlide2

KEYPOINTS:Spinal, epidural and caudal blocks are known as the neuraxial blocksPrincipal site of action of neuraxial

blocks is the spinal nerve roots

Sensory, motor and to some degree sympathetic block is achieved with

neuraxial

techniques

Level is below L1/2 in adults and L3 in children

Nb

definite contra- indications to

neuraxial

techniquesSlide3

ANATOMYSlide4

AnatomySpine is composed of vertebral bones and cartilaginous intervertebral discs7cervical, 12 thoracic, 5 lumbar vertebrae

The 5 sacral vertebrae is fused and there is small rudimentary

coccygeal

vertebra

Vertebral structure:

body

anteriorly

, connected via 2 pedicles to transverse processes that in turn is connected

posteriorly

to the

spinous

process via 2 lamina. Each vertebral has 4 small synovial joints connecting it to the vertebra above and below it allowing movement of the spinal columnSlide5

ANATOMYSlide6

ANATOMYLamina of S5 and S4 normally doesn’t fuse, leaving small caudal opening to the spinal canal called the sacral meatusEach vertebral body is separated by an

intervertebral

disc

Spinal column has double-C shape: convex

anteriorly

in the cervical and lumbar areas

Ligament provide (together with muscles) structural support and help maintain unique shape.

Vertebral body and discs are connected and supported by ant and post longitudinal ligaments and dorsally the

ligamentum

flavum

,

interspinous

and

supraspinous

ligaments provide additional stabilitySlide7

ANATOMYSlide8

ANATOMYSlide9

ANATOMYSpinal canal contains spinal cord, it’s coverings (meninges) fatty tissue and an venous plexusMeninges: 3 layers:

pia

mater – closely adhered to spinal cord

arachnoid

losely

adherent to thicker and denser

dural

mater

CSF

containe

between

arachnoid

and

pia

mater

Spinal subdural space – potential space between

dura

and

arachnoid

Epidural space – between

dura

mater and

ligamentum

flavumSlide10

ANATOMYSpinal cord extends from the foramem magnum to L1 in adults and L3 in childrenAnt and post nerve roots join each other forming spinal nerves exiting through

intervertebral

foramina on each level

From L1 down lower spinal nerves travel some distance before exiting through

intervertebral

foramina, forming the

cauda

equina

Safe level for

neuraxial

techniques – below L1 in adult and L3 in children to avoid direct cord damage Slide11

ANATOMYSlide12

Mechanism of action Principle site of action of neuraxial techniques is nerve rootBlocking post nerve roots interrupts somatic and visceral sensation

Blocking anterior nerve root prevent motor and autonomic outflow

Differential blockade:

sympathetic blockade 2 levels above sensory block which in turn is 2 levels above motor blockSlide13

AUTONOMIC BLOCKSympathetic plexus from T1 to L1Blocking anything from T5 downwards result in decreased vasomotor tone, pooling of blood in lower limbs and decrease in blood pressure... Normally with compensatory tachycardiaBlocking T1-T4 blocks cardiac

accelaratory

fibres leading to

bradycardia

and decreased cardiac contractility

Deleterious CVS effects must be countered by volume loading pt with 10-20ml/kg IVI fluid and early administration of

vasopressors

Bradycardia

should be treated with atropineSlide14

AUTONOMIC BLOCKGIT- Sympathetic block leads to vagal predominance leading to small contracted gut with active peristalsis. Hepatic bloodflow

reduction mirrors drop in BP

Urinary Tract – lumbar and sacral level blocks block both sympathetic and parasympathetic bladder control leading to urinary retention till block wears off

Neuraxial

techniques partially or totally block the

neuro

-endocrine stress response induced by surgerySlide15

CONTRAINDICATIONS TO NEURAXIAL TECHNIQUESAbsolute:Infection at site of injectionPatient refusalCoagulopathy

or bleeding diathesis

Severe mitral or aortic

stenosis

Severe

hypovolemia

Increased intracranial pressureSlide16

CONTRAINDICATIONS cont’dRELATIVESepsisPreexisting neurological deficitsSevere spinal deformity

Uncooperative patient

Stenotic

valve lesionsSlide17

CONTRAINDICATIONS cont’dCONTROVERSIALPrior back surgery at site of injectionInability to communicate with patientComplicated surgery – major

bloodloss

expectedSlide18

Patients with coagulopathy – Excepted preoperative valuesINR - < 1,5 ( <1.75 if experienced anaestetist)

PTT – upper limit of normal ( < 35s)

Platelet count - >80 000

Bleeding time - <10 min

Ureum

- > 12 ( > 15 in experienced hands)Slide19

Strategies for discontinuation of anticoagulation in peri-op period

Minimum delay pre-op or prior to placement or removal of epidural catheter

Mimimum delay post op or after removal of neuraxial catheters

UFH

4h

1h

LMWH prophylaxis

12h

4h

LMWH treatment

24h

6-8h

Aspirin

0h

0h

Warfarin

3-5days

Immediately

But controversial

Fondaparinux

36 hours but epidural catheter not recommended

Epidural not recommended

Dosing not recommended <6h

Clopidogrel (Plavix)

5-7days

immediatelySlide20

NEURAXIAL TECHNIQUES –anatomic approachSlide21

NEURAXIAL TECHNIQUESanatomic approachIdentify spinous processes

Spinous

processes almost horizontal in cervical and lumbar area where in thoracic area they slant in caudal direction and can overlap

Direct needle slightly

cephalad

angle for cervical and lumbar blocks, and significantly

cephalad

for thoracic blocksSlide22

PATIENT POSITIONINGSlide23

SPINAL ANAESTHESIASterile technique with handwashing, sterile gowning of doctor, then cleaning block field with alcohol and water solution, wiping it off, then draping with surgical drapesMidline or

paramedian

approach used

Injection area localized with local anaesthetic

Spinal needle advanced through skin

Further advanced until two “pops” are felt. 1

st

is penetration of

liagmentum

flavum

and 2

nd

penetration of

dura-arachnoid

membrane.Slide24

SPINAL ANAESTHESIARemove styletSuccessful dural puncture confirmed by free flow of CSF

Persistent

parasthesia

or pain on injection –indicate direct nerve root contact. Needle should be withdrawn and redirected.

Needle bevel should be turned to side, this ensure that nerve fibres are

seperated

and not cut on

dural

punctureSlide25

SPINAL ANAESTHESIASlide26

SPINAL ANAESTHESIA Slide27

SPINAL ANAESTHESIA factors influencing level of blockBaricity of solution hyperbaric solutions is denser than CSF, therefore spreading downward with gravity,

wherease

hypobaric is less dense and will spread more

cephalad

.

Positioning of patient

Head down position – hyperbaric solution spreads

cephalad

Head up – hyperbaric solution spreads

caudad

Lateral position – Hyperbaric solution will have greater spread on dependent sideSlide28

SPINAL ANAESTHESIA factors influencing level of blockDrug dosageSite of injectionAge ( decreased volume of CSF – higher level for same dosage)Drug volume

Intra- abdominal pressure and pregnancy

Patient heightSlide29

SPINAL ANAESTHESIA different agents used

DRUG

PREPARATION

DOSE

LOWER LIMBS (mg)

DOSE LOWER AB DOMEN (mg)

DOSE UPPER AB DOMEN (mg)

DURATION

MIN

PLAIN

DURATION MIN

ADREN.

Procaine

10%

75

125

200

45

60

Bupivacaine

+/- dextrose

5%

4-10

12-14

12-18

90-120

100-150

Tetracaine

1%

4-8

10-12

10-16

90-120

120-140

Ropivacaine

0.2 -1%

8-12

12-16

16-18

90-120

90-120Slide30

EPIDURALSSingle shot or indwelling catheter techniquesBoluses or constant infusionWider scope of out of theatre use , for example labour epiduralsMotor block can range from absent to complete

Slower in onset ( 10-20min) and less dense block than spinalsSlide31

EPIDURALSTuohy needle most commonly usedThe blunt curved tip push away the dura after passing through the

ligamentum

flavum

instead of penetrating it.Slide32

EPIDURALSSlide33

EPIDURALSEpidural catheters is useful for intraop and post op pain controlMidline of paramedian

approach can be used

Passes from skin through to space between

dura

and

ligamentum

flavum

2 techniques for identifying whether needle/catheter tip in epidural space: the “loss of resistance

technque

” and the “hanging drop” techniqueSlide34

EPIDURALSLoss of resistance technique is preferredThe needle is advanced through subcut. tissue with stylet

in place for about 2 centimetres

Stylet

removed and needle connected to a syringe

According to physician preference the syringe can be filled with air or saline

The needle is slowly advanced millimetre by millimetre

with rapidly repeated attempts at injectionSlide35

EPIDURALSAs the tip enters epidural space there is a sudden loss of resistance and injection is easy.The hanging drop technique requires that the hub of the needle be filled with saline so that a drop hangs from its outside opening.As the tip enters the epidural space a negative pressure is created that sucks the drop of fluid into the needle.Slide36

EPIDURALSSlide37

EPIDURALSThe quantity of local anaesthetic is large compared to that used in spinal and will result in significant toxicity if injected intrathecally or intravascularly

Test dose designed to detect

intrathecal

or

intravasc

injection

Lignocaine

40mg and 15ug of Adrenaline

In case of

intrathecal

injection

lignocaine

will result in immediate spinal anaesthesia

The adrenalin will cause tachycardia and increase in BP on

intravasc

injectionSlide38

EPIDURAL AGENTSAGENT

CONCENTR

ONSET

SENSORY BLOCK

MOTOR BLOCK

Ligno

caine

<1%

1.5%

2%

Intermediate

Intermediate

Intermediate

Anagesic

Dense

Dense

Minimal

Mild

–mod

Dense

Mepivacaine

1%

2-3%

Intermediate

intermediate

Analgesic

Dense

Minimal

Dense

Bupivacaine

<0.25%

0.5%

0.75%

Slow

Slow

Slow

Analgesic

Dense

Dense

Minimal

Mild –mod

Mod

- dense

Ropivacaine

0.2%

0.5%

0.75-1%

Slow

Slow

Slow

Analgesic

Dense

Dense

Minimal

Mild – mod

Mod - denseSlide39

CAUDAL ANAESTHESIAForm of epidural anaesthesiaCommonly use in pediatric populationInvolves needle/catheter penetration of

sacrococcygeal

ligament covering the sacral hiatus

Calcification of this ligament in adults makes

caudals

difficult or impossible in adultsSlide40

CAUDAL ANAESTHESIASlide41

COMPLICATIONS OF NEURAXIAL TECHNIQUESADVERSE OR EXAGGERATED PHYSIOLOGICAL RESPONSESUrinary retentionHigh blockCardiac arrest

Anterior spinal artery syndrome

Horner’s syndromeSlide42

COMPLICATIONS cont’dCOMPLICATIONS RELATED TO NEEDLE/CATHETER PLACEMENTTrauma – backache - postdural

puncture headache

-

diplopia

- tinnitus

Neural injury – nerve root damage

- spinal cord damage

-

cauda

equina

syndrome

Bleeding – spinal or epidural haematomaSlide43

COMPLICATIONS cont’dMisplacement –no/inadequate anaesthesia - subdural block - inadvertent spinal block

- inadvertent

intravasc

injection

Catheter shearing/retention

Inflammation –

arachnoiditis

Infection – meningitis or epidural abscessSlide44

COMPLICATIONS cont’dRELATED TO DRUG TOXICITYSystemic local anaesthetic toxicityTransient neurological symptomsCauda

equina

syndromeSlide45

INCIDENCE OF SERIOUS COMPLICATIONS

SPINAL ( n=40 640)

EPIDURAL (n=30

413)

Cardiac arrest

26

3

Death

6

0

Seizure

0

4

Cauda

equina

syndrome

5

0

Paraplegia

0

1

Radiculopathy

19

5Slide46

COMPLICATIONS cont’dCARDIAC ARREST - 1:1500 spinals - preceded by bradicardia and decreased preload

-

occures

in young

healthe

patients

- pt’s with high basal

vagal

tone at riskSlide47

COMPLICATIONS cont’dHIGH NEURAL BLOCK - pt often complain of dyspnoea or inability to cough - numbness or weakness in upper extremities

- nausea with or without vomiting precedes hypotension

- unconsciousness,

apnea

and hypotension are referred to as high or total spinals

Pt should be reassured, given O2 supplementation and

bradycardia

and hypotension treated. Once unconsciousness or apnoea occurs pt should be

intubated

and ventilatedSlide48

COMPLICATIONS cont’dPOST DURAL PUNCTURE HEADACHETypically bilateral, frontal or retro orbital and extends into the neckThrobbing or constantAssociated with photophobia and nausea

Hallmark = associated with position

Pain

aggrevates

by sitting or standing, improves by lying down

Onset normally 12-72 h after puncture, but may even be seen immediately after punctureSlide49

Post puncture headachesUntreated pain may last for weeksBelieved to be caused by CSF leakage from dural defectLoss of CSF cause traction on structures supporting the brain, particularly the

dura

Increased traction on

bloodvessels

also contribute to pain

Blood vessel dilation to compensate for central volume loss may also contribute to painSlide50

Post puncture headachesIncidence strongly related to needle type, needle size and pt populationCutting point needles higher incidence than pencil pointsFactors that increase risk: young pt, female and pregnancy

Conservative Rx:

bedrest

, hydration, analgesics and caffeine

Epidural

bloodpatch

is very effective. It involves injecting 10-20ml of the patients blood into epidural space at the level or 1 level below previous punctureSlide51

Complications cont’d: Spinal or epidural haematomaIncidence 1: 150 000 for epidurals and 1:220 000 for spinalsMostly occur in pt with abn

coagulation

Pathological insult results from mass effect compressing neural tissue and causing direct pressure injury and

ischaemia

Rapid diagnosis is paramount otherwise injury will be permanent, may result in paraplegia

Symptoms: sharp back and leg pain with progressive numbness and motor weakness and sphincter dysfunction

Rx: evacuation by neurosurgeons

Good results if done within 8-12hSlide52

Complications cont’d:Epidural abscessRare but devastating4 classical clinical stages1: back or vertebral pain, intensified by percussion of vertebrae

2: nerve root or

radicular

pain

developes

3: marked by motor or sensory

defecits

or sphincter dysfunction

4: paralysis or paraplegia

Rx early recognition, antibiotics, surgical decompression and evacuation

NB aseptic technique during catheter placement!Slide53

Complications cont’d:Transient neurological symptomsAlso called transient radicular irritation

Back pain radiation to the legs without sensory or motor

defecits

,

occuring

after resolution of spinal block and resolving spontaneously within days

Associated with: hyperbaric

lignocaine

, outpatient procedures, pt in

lithotomy

position

Appears to be concentration-related neurotoxicity of local anaestheticsSlide54

Complications cont’d:Cauda equina syndromeAssociated with use of continuous spinal catheters

and 5%

lignocaine

Bowel and bladder dysfunction together with evidence of multiple nerve root injury

Neurotoxicity following repeat

intrathecal

injection is higher with

lignocaine

>

tetracaine

>

bupivacaine

>

ropivacaineSlide55

Other regional techniquesA nerve can be block anywhere along its courseRegional techniques avoid some of the complications associated with neuraxial techniques

Contra- indications:

Uncooperative patient

Bleeding diathesis

Infection

Peripheral neuropathySlide56

Regional techniquesSlide57

Regional techniquesSlide58

Regional techniquesNormally done with nerve stimulator to identify correct nerves to be blockedSlide59

Regional techniques: Biers blockIntravenous regional techniqueNormally of the forearmShort procedures (45-60min)Jelco

/ IV access established

on dorsum of hand

Double pneumatic tourniquet is placed on upper arm

The extremity is elevated and

exsanguinated

by tightly wrapped

Eschmark

bandages

Upper tourniquet is inflated

0.5%

lignocaine

injected – 25ml for forearm, 50ml for whole armSlide60

Bier’s BlockAnaesthesia normally established in 5-10minPt often complain of tourniquet pain after 20-30minWhen this occurs the lower tourniquet is inflated and the proximal one deflated.Slide61

THE END