LOCAL ANAESTHETICS

•LOCAL ANAESTHETICS

• • DR. SHITAL

DALAL•

LECTURER

• HISTORY : Ist Local anaesthetic used was COCAINE by CARRRL KOLLAR in ophthalmic patient for anaesthetising cornea.

• CLASSIFICATION

• AMINOESTERS AMINOAMIDES

• Procaine Lignocaine

• Chloroprocaine Mepivacaine• Tetracaine Prilocaine• Benzocaine Bupivacaine

• Cocaine Ethidocaine Ropivacaine

Based on duration , action & potency

• Short duration , low potency• CHLOROPROCAINE• PROCAINE

• Intermediate duration & intermediate potency• LIGNOCAINE• MEPIVACAINE• PRILOCAINE• COCAINE

• Long duration , high potency• BUPIVACAINE• TETRACAINE• ETHIDOCAINE• DIBUCAINE [ Longest duration]• ROPIVACAINE

•

MECHANISM OF ACTION•

Drug undissociated [ nonionised ] form penetrates axonal membrane & inside gets dissociated [ ionised]

• Ionised form binds recepter situated in Na channel in inactivated state from inner side ,blocking channel & prevents depolarization & hence action potential

• GENERAL CONSIDERATION• POTENCY depends on lipid solubility • ONSET OF ACTION depends on PKa closer to body

PH rapid action Addition of Sodabicarb -- rapid action• TYPE OF NERVE FIBRE• Myelinated > sensitive than non-myelinated • B fibre block rapidly than C --- AUTONOMIC [ C &

B] –SENSORY [ C & A ] ---MOTOR

IN RECOVERY –MOTOR -- SENSORY -- AUTONOMIC IN SENSORY --TEMP [COLD > HOT ] –PAIN --TOUCH –DEEP PRESSURE ---PROPIOCEPTION

• DURATION OF ACTION depends on − DOSE

− PLASMA PROTIEN BINDING

− METABOLISM− ADDITION OF VOSOCONSTRICTERS− ADRENALINE − SODABICARBONATE

• SYSTEMIC ABSORPTION depends on − SITE OF INJECTION− ADDITION OF VASOCONSTRICTERS

METABOLISM

• ESTERS are metabolised by pseudocholinesterase [ except COCAINE]

• AMIDES metabolised by hepatic microsomal ENZYMES

• Significant amount of prilocaine by lungs

SYSTEMIC EFFECTS & TOXICITY

• CVS

− Vasodilaters except COCAINE − LIGNOCAINE & PROCAINE have stabilizing

effect on cell membrane of cardiac tissue

− Negative inotropic action on myocardium

− Depresses conduction system

− Bradycardia , decraeses myocardial contractility, hypotention , vetricular arrhythmias causes cardiac arrest

− Cardiotoxic potential is much higher with bupivacaine

CENTRAL NERVOUS SYSTEM

• Exitation followed by depression of cerebral tissue leading to

− Circumoral numbness

− Dizziness

−Tongue parasthesia

− Visual and auditory disturbanses

−Muscle twiching , tremors , convulsion, followed by coma and death.

RESPIRATORY SYSTEM

• LIGNOCAINE depresses hypoxic drive . Direct depression of medullary respiratory center can occur at high doses

IMMUNOLOGIC • Allergic reaction are very common with esters but

rare with amides .The reaction with amides is due to preservative [ Methyl paraben ] Cross sensitivity does not exist between classes but exist between agents of

same class .

LOCAL TOXICITY• NEUROTOXIC when directly injected into nerve

• MYOTOXIC when directly injected into muscle

• CHLOROPROCAINE can cause neurological defecits

• Cauda equina syndrome seen with repeated doses of 5% LIGNOCAINE & 0.5% TETRACAINE

• Local anaesthetic with ADRENALINE can cause necrosis & gangrene if used in ring block

• Methaehaemoglobinemia seen with PRILOCAINE , BENZOCAINE & very rarely with LIGNOCAINE

• LIGNOCAINE can cause Malignant hyperthermia in susceptible individual .

METHODS OF LOCAL ANALGESIA

• Topical application EMLA [ Euethetic mixure of PRILOCAINE 5% & LIGNOCAINE 5% ] IN EQUAL amount.

• XYLOCAINE SPRAY 4% , TETRACAINE & BENZOCAINE LOZENGES for mucous membrane of mouth pharynx & larynx

• XYLOCAINE JELLY 2% for catheterization and proctoscopies

• LIGNOCAINE 4% , DIBUCAINE 1% & BENZOCAINE 5% for anal fissure and painful piles

• OXETHAZAINE [ mucaine gel ] 0.2% for gastritis

• INFILTRATION ANAESTHESIA

• NERVE BLOCKS

• INTRAVENOUS REGIONAL ANAESTHESIA [ BIERS BLOCK]

• CENTRAL NEURAXIAL BLOCK [ SPINAL , EPIDURAL]

• REFRIGERATION ANEASTHESIA [ CO2 snow , ice cooling ,ethyl chloride spray ]

COCAINE

• Extracted from Erythexylon Coca

• CNS – Euphoria , Agitation , Hyperexcitation , Violence convulsion , apnea & death

• CVS—Potent vasoconstricter

• Metabolised in liver. Metabolite ecognine is CNS stimulant

• USES—Only for surface analgesia 1% solution for cornea. Never use intravenously .

PROCAINE

• Agent of choice in pt of malignant hyperthermia

CHLOROPROCAINE • Shortest acting ,most acidic• Contraindicated in spinal anaesthesia

• Max safe dose of both -- 1,000mg

TETRACAINE• IT can cause ventricular fibrillation• A lozenges containing tetracaine available• Duration of action > cocaine & lignocaine

MEPIVACAINE• Same as lignocaine PRILOCAINE• Methaemoglobinemia occurs at higher doses

DIBUCAINE• Longest acting , most potent ,most toxic

LIGNOCAINE

• Ist synthesised in 1943 in Sweden by LOFGREN of AB astra . Used in clinical practice in 1948

• Solution stable , contains preservative methyl paraben . PKa--- 7.8 .

• Concentration used • SURFACE ANAESTHESIA 4 %. 10% 15%

• GARGLING 2% VISCOUS• NERVE BLOCKS 1 -- 2%• URETHRAL PROCEDURE 2% Jelly

• SPINAL --- 5% Heavy

• EPIDURAL ---1 to 2% WITH Adrenaline

• CARDIAC ARRYTHMIAS --- 2% XYLOCARD

• IV BIERS BLOCK --- 0.5 %

• INFILTRATION BLOCK --- 1 to 2%

PREPARATIONS OF LIGNOCAINE

METABOLISM –In liver . Excreted by kidney half life –6 hrs

• DURATION OF ACTION

• With ADRENALINE --- 2 – 3 hrs

• Without ADRENALINE --- 45 – 60 mins

• Max safe dose ----3mg/ kg plain

---7 mg / kg with ADRENALINE

• EFFECTS -- CNS effects occur at much lesser dose than CVS .Systemic toxicity is more than Bupivacaine

LIGNOCAINE releases calcium from sarcoplasmic reticulum so should not be used in pt with malignant hyperthermia

• Can cause cauda equina syndrome after continuous spinal

• OTHER USES -- CARDIAC ARRHYTHMIAS

• Blunting response to laryngoscopy & intubation

LIGNOCAINE SENSITIVITY

BUPIVACAINE

• 4 times potent than xylocaine 0.5% solution available ie more stable

• Highly cardiotoxic . It increases in pregnancy , hypoxia & acidosis High degree of tissue and protein binding makes resuscitation prolonged and difficult

• Should not be used in BIERS block• Metabolised in liver t1/2 – 3.5 hrs

PREPARATIONS OF BUPIVACAINE

DURATION OF EFFECT without adrenaline --2– 3hrs with adrenaline -- 3—5 hrs

• Max safe dose –2mg / kg [with /without adrenaline]• CONCENTRATION USED

• For nerve block -- 0.5%

• Epidural -- 0.5% [ ANAESTHESIA]

-- 0.25% [ ANALGESIA]

-0.125% [ POST OP ANALGSIA]

• SPINAL -- 0.5% [heavy ]

• Labour analgesia – 0.125% to 0.0625 %

ROPIVACAINE

• ROPIVACAINE consists of single enantiomer /the S isomer [ levo isomer ]

• Cardiotoxicity & CNS toxicity is much less than bupivacaine.so cardiac arrest following ropivacaine has much better prognosis due

• To Rapid reversal of sodium channel Rapid clearance from circulation

• Motor & sensory block is similar to bupivacaine

• SAFE DOSE – 3mg/kg

INFILTRATION BLOCK

• Managing interacting pain by injecting 0.5% lignocaine or 0.25% bupivacaine in to painful tissue

• Leads to disappearance of referred pain ,muscle spasm

• Mostly used in sprains ,strains ,painful undisplaced fracture , low back pain , burcitis ,tendinitis ,artritis ,myalgia torticolitis

• Painful scars following surgery

DIGITAL NERVE BLOCK

• The digital nerves to a fingre or toe can be blocked by infiltration of local anaesthetic solution on either side of base of proximal phalynx

• .Lignocaine 0.5% shoud be used

but remember without adrenaline.

• Adrenaline causes marked vasoconstriction of digital vessels leading to gangrene

ANKLE BLOCK

• Deep peroneal , superficial peroneal and sephanous nerve blocked along with subcutaneous infiltration at the dorsum of foot , posterior tibial posterior to medial malleolus and sural laterally between lateral malleolus and Achillis tendon

PARACERVICAL BLOCK

• Injection of 8-10 ml 1% Lignocaine into each fornix blocks afferent supply of uterus & produces adequete Ist stage pain relief in 80% of pt.

• Disadvantage –Foetal bradycardia [20—30%] due to decrease in placental flow resulting from uterine artery vasoconstriction .

PUDENDAL NERVE BLOCK

• Indications• surgery of lower vagina & perineum• midcavity forcep delivery & episeotomy

repair• Not for MRP

• METHODS *Transperineal approach

*Transvaginal approach

TRANSPERINEAL PUDENDAL NERVE BLOCK

• Skin wheal over ischial tuberocity . 10 cm needle inserted & guided until point lies above and behind ischial spine with free hand in vagina .10 ml 1% lignocaine hydrocloride injected on both side

TRANSVAGINAL PUDENDAL NERVE BLOCK

• Guarded needle , tip inserted just above &behind ischial spine 20ml 1% lignocaine

hydrocloride.Needle first passes through sacrospinous ligament .Simpler , less painful ,higher success rate , less damage to foetus

DR. S. DALAL LECTURER

DEPTT OF ANAESTHESIA GMC NAGPUR

HISTORY

ANATOMY OF VERTEBRAL COLUNM

• 33 VERTIBRAS

7 cervical

12 thoracic

5 lumber

5 sacral

4 coccegeal

• 31 PAIRS OF SPINAL NERVES

• 4 curves -- Thoracic and sacral are convex posteriorly [ khyphotic] while cervical and lumber spine are convex anteriorly [ lordotic]

ANATOMY OF SPINAL CORD• Medula oblongeta to

lower border of L1 vertebra .In infants & neonates, lower border of L3

• Meninges –inside to outside piamater --- arachnoid mater – duramater

• Duramater extends to S2 & S4 in infants

BLOOD SUPPLY OF SPINAL CORD

• 2 Posterier spinal arteries from post inferier cerebellar artery and 1 anterier spinal artery formed by branch of vertebral artery

• Artery of adamkiewisz [arteria radiculari magna]

SRUCTURES ENCOUNTERED DURING SPINAL

• SKIN• SUBCUTANOUS

TISSUE• SUPRASPINOUS

LIGAMENT• INTERSPINOUS LIG

• LIGAMENTUM FLAVEM

• DURA • ARACHNOID

• DERMATOLOGICAL SEGMENTAL LEVEL

• NIPPLES T4• XIPHISTERNUM T6• UMBILICUS T10

• PUBIC SYMPHYSIS L1

• PERINEUM S1 TO S4

• SEGMENTAL LEVEL OF SPINAL REFLEXES

• EPIGASTRIUM T7 , T8• ABDOMINAL T9 T12• CREMASTRIC L1,2

• KNEE JERK L2,3,4• ANKLE JERK S1,2• ANAL SPHINCTER

S4,5• PLANTER S1,S2

CEREBROSPINAL FLUID

• Present between pia & aracnoid mater i.e. subaracnoid space

• 500ml secreted per 24 hrs

• Volume 135 ml , 75ml in subaracnoid space

• Specific gravity – 1.0003 g/ml

• CSF pressure 70 to 120mm of H2O in lateral position , 375 to 550 in vertical position

INDICATIONS & CONTRAINDICATIONS

• Orthopaedic surgeries [ lower limb & pelvic ]

• General surgeries [lower abdominal , pelvic perineal, bladder, ureteric & prostetic surgeries

• Gynaecological & obstretic surgery

• Bleeding disorders

• Infection at site

• Pt with CNS abnormality & CVS problems

• Spine deformity

• Pts refusal

POSITION FOR SPINAL

• Either left or right lateral .

• Flexion – hip & knee so knee touch to abdomen

• Flexion – neck so chin touch to sternum

• Sitting –leg should rest on stool & pillow below shoulder

SPINAL NEEDLES

Adv over GA

* Cheaper

* Less pulmonary aspiration

*Less respiratory complications

* Less drugs

* Bleeding less

* Decrease thromboembolism

• DRUGS USED 5% Lignocaine [ heavy]

• 0.5% Bupivacaine [ heavy ]

• Opiods ,ketamine midazolam

SYSTEMIC EFFECTS

• CVS : * Venodilatation due to sympathetic block

* Dilatation of post arteriolar capillaries * Decreases cardiac output

* Decreases venous return Bradycardia ( Bainbridge reflex ) - Inhibition of cardioaccelator fibers[T1-T4] - Paralysis of nerve supply to adrenal gland

with decrease catecholamine supply *Supine hypotention syndrome

* Systemic direct drug absorption

CENTRAL NERVOUS SYSTEM

• Sequence of block * Autonomic Sensory

-- Motor and recovery is reverse . Hence autonomic level is 2 seg higher than sensory level which is 2 seg higher than motor block

-- Ist -- Temp ( cold – hot ) –pinprick –motor ---touch -- propioception

RESPIRATORY SYSTEM

• Tidal volume , minute volume , PaO2 well maintained

• In higher blocks impairment of respiratory function to paralysis of abdominal & lower intercostal occures

• Apnea only in total spinal due to severe hypotention causing medullary ischemia.

GASTROINTESTINAL SYSTEM

• Contracted gut with relaxed spinctures due to sympathetic block & parasympathetic overactivity . Peristalsis increased.

LIVER• Minimal effect

RENAL• Impaired only if critical pressure of kidney for

autoregulation falls below 55 mm of hg

GENITAL SYSTEM

• Flaacid and enlarged penis is one of the sign of successful block.

ENDOCRINAL

* Stess response to surgery ( adrenals) inhibited

* Respose to insulin is augmented & there can be hypoglycemia

* Increase in ADH during surgery suppresed.

THERMOREGULATION

• Venodilatation causes heat loss .Compenseted vasoconstriction & shivering .

SITE OF ACTION ( LOCAL ANAESTHETICS)

* Acts on spinal nerves & dorsal ganglion

FACTERS AFFECTING HEIGHT OF BLOCK

• Volume - more --- increase block• Baricity

Hyperbaric –fixation of drug

Hypobaric – drug cranially

Isobaric - same level

• Intraabdominal pressure• Spinal curvature• Age , obesity , height

DURATION -- Dose , conc ,addition of opoids or vasoconstricters

COMPLICATIONS

* Hypotention

* Bradycardia

* Respiratory paralysis

* Nausea & vomiting

* Difficulty in phonation

* Cardiac arrest

* High spinal / total spinal

POST OPERATIVE COMPLICATION

• POST-SPINAL HEADACHE mainly occipital ,increases in sitting position ,decrease in lying down .Ocurrs in 3-30% pts last for 7-10 days

• T/t H– Head low tilt E- Epidural saline A- Analgesics D- Demopressin A- Abdominal binders C – Caffine H – Hydration E - Epidural blood patch

• Urinary retention

• Paraplegia

• Paralysis of 6 th cranial nerve

• Aracnoiditis

• spinal cord ischemia

• Anterior artery syndrome

• Backache

• Meningeal irritation

• Cauda equina syndrome

DR.S.DALAL

LECTURER

HISTORY 1st epidural was given by CORNING in 1885

• What is epidural space?• Lies within body cavity of

spinal canal & outside dural sac

• Ant-body of vertebra & post longitudinal ligament

• Post-ligamentum flavem

Epidural space contains-fat & venous plexes• Negative pressure in space due to

* negative pressure is transmitted from pleural cavity via thoracic paravertebral space

* negative pressure created by flexion of spine

* created by identing the dura with needle point

• TWO TYPES Single shot epidural continous with catheter

WHY EPIDURAL ?

• Early ambulation of patient possible• Better wound healing

• Less respiratory discomfort• Less abdominal discomfort • Psycological stability

• Economic , less hospital stay• Mothers & baby outcome well in labour analgesia

INDICATIONS

• LUMBAR EPIDURAL – all lower abdominal surgeries

• THORACIC EPIDURAL – upper abdominal , thoracic surgeries

• CERVICAL EPIDURAL –neck surgeries by CONTINOUS EPIDURAL CATHETER – postoperative pain relief

• LABOUR ANALGESIA –mother is delivering baby with a smile on her face

• CHRONIC PAIN RELIEF --CANCER PTS• ACUTE OCCLUSIVE VASCULAR CONDITIONS• BLOOD PATCH – for postspinal headache

• BETTER in ASA grade 3 & 4 pts

CONTRAINDICATIONS• SAME as spinal• Coagulation disorders, septicemia ,infection at site,

pts refusal ,aortic stenosis , critical mitral stenosis

EPIDURAL TRAY

• Touhy epidural needle with stelyet

• 10 cc syringe for air or saline

• Epidural catheter with introducer & adapter

• 2 cc / 5 cc syringe for local

• Stickings

POSITION FOR EPIDURAL

METHODS OF IDENTIFYING EPIDURAL SPACE

• Loss of resistance technique [ piercing ligamentum flavem ]

• Hanging drop technique [ drop of saline sucked]

• Air injection / saline injection technique

• Machtosh extradural space indicater• Odoms indicater • Saline drip technique

Test dose – 3cc lignocaine with adrenaline

• Effect – WITHIN 15 -- 20 MINS motor effect less as compare to spinal

SITE OF ACTION• Anterior & posterior nerve roots• Mixed spinal nerves• Drug diffuses through dura & aracnoid & inhibits

descending pathways in spinal cord.

DRUGS -- Volume is more imp than concentration

• LIGNOCAINE [ with or without adrenaline ]2%

• BUPIVACAINE Anaesthesia -- 0.5% Analgesia -- 0.25%

post op analgesia– 0.125% along with opoids [ opiods act by binding the opoid receptor in substansia gelatinosa of dorsal horn cell]

• DISADVANTAGES Respiratory depression ,urinary retention ,vomiting, itching

OPIODS USED IN EPIDURAL

• MORPHINE ----12—16 hrs

• TRAMADOL --- 8 hrs – 100 mg 8 hrly

• BUPREGESIC– 12 hrs – 100-150 ug 12 hrly

• BUTRUM ------- 3 hrs – 1-2 mg

• MIDAZOLAM --- 4 hrs – 2mg 4 hrly

COMPLICATIONS

• Patchy effect • Surgical relaxation not good• Hypotention less as in spinal• Apnea occurs with higher blocks• Chances of total spinal is more• Dural puncture• Subdural block• Intravascular injection • Horners syndrome

– Epidural abscess

– Backache

– Broken catheter

– Meningitis

– Epidural haematoma

HISTORY – Ist given by SORIESI in 1937

ADVANTAGES : Both spinal & epidural

* Early & reliable onset

* Fast tracking of pt saving ot time

* Good surgical relaxation

* Facility for extended anaesthesia

* Provision for postop analgesia

* Less dose requirement of local anaesthetics

* Less post-spinal headache

CAUDAL BLOCK• Type of epidural block

INDICATIONS• IN children for anaes or

postop anaelgesia like perianal , genital urethral surgeries

• Lat or prone position

• DOSE -0.5 to 1ml/kg