Regional Anesthesia

PHYSIOLOGY OF NERVE CONDUCTION Nerve Fiber – impulse – transmitting unit Membrane 90% of lipids 10% protein Channels guarded by “gates” K+ pass freely in and out Na+ barred outside Negative resting potential -70 to -90 mV

PHYSIOLOGY OF NERVE CONDUCTION Nerve Stimulation Gates open Na+ rushing in Shifting of polarity Depolarization

Classification of Regional Anesthesia (according to SITE of application) I. TOPICAL – skin or mucous membrane spray – refrigeration (e.g. boils / abcess) ointment – insect bites instillation – urethral meatus contact – cotton pledgets in nasal mucosa II. INFILTRATION – incision site / tissue to be cut (e.g. sebaceous cyst) III. FIELD BLOCK – around tissue to be cut (e.g. breast mass)

IV. INTRAVENOUS REGIONAL (Bier Block) Peripheral vein of upper / lower extremity I.V. catheter inserted Desanguinated extremity Esmarch elastic bandage

2 tourniquets (BP cuffs) bandage removed LA injected over 2-3 minutes Distal tourniquet inflated after 20-30 minutes Proximal tourniquet deflated Slow release of tourniquet after at least 15-20 minutes Use: short surgical procedure < 45 minutes in upper / lower extremity

V. CONDUCTION BLOCK – along nerve or course of nerves A. Peripheral Nerve Blocks B. Central Blocks

Peripheral Nerve Blocks RETROBULBAR NERVE BLOCK (ciliary ganglion) Indications Cataract surgery Corneal transplant Enucleation Complications Retrobulbar hemorrhage Globe perforation Contraindications Bleeding disorders Extreme myopia Open-eye injury

Peripheral Nerve Blocks GASSERIAN GANGLION BLOCK Branches of trigeminal nerve (ophthalmic, maxillary, mandibular) Indications Trigeminal neuralgia Cancer pain in face Operations in face teeth, gum, mandible, etc. Technique: LA injected into respective foramen of nerve branches

Peripheral Nerve Blocks CERVICAL PLEXUS BLOCK Anterior rami of C1-C4 spinal nerve roots Sensory supply to jaw, a neck, occiput, chest-shoulders, clavicle, upper border of scapula Indications Operations in the neck Cervical lymph node biopsy Carotid endarterectomy Thyroid operations

Peripheral Nerve Blocks BRACHIAL PLEXUS BLOCK Anterior rami of C4-T2 spinal nerve roots Entire motor supply of upper extremity Almost entire sensory supply – except over shoulder and medial arm

Major Peripheral Branches a. Axillary N – shoulder abduction b. Musculocutaneous – elbow flexion c. Radial – elbow, wrist, and finger extensions d. Median – wrist and finger flexion e. Ulnar – wrist and finger flexion

Peripheral Nerve Blocks BRACHIAL PLEXUS BLOCK Indication: operations of upper extremity Approaches to Brachial Plexus Block 1. interscalene approach 2. Supraclavicular 3. Infraclavicular 4. axillary

BRACHIAL PLEXUS BLOCK Interscalene approach

BRACHIAL PLEXUS BLOCK Axillary approach

Peripheral Nerve Blocks INTERCOSTAL NERVE BLOCK Anterior rami of 1st eleven spinal nerves At inferior surface of ribs Indications Post-op analgesia of thoracic and upper abdomen surgeries Relief of pain from rib fractures, herpes zoster, pleurisy Complications: pneumothorax

INTERCOSTAL NERVE BLOCK

INTERCOSTAL NERVE BLOCK

INTERCOSTAL NERVE BLOCK

Peripheral Nerve Blocks WRIST BLOCK Ulnar nerve Median Radial Indications: surgery or analgesia distal to metacarpophalangeal joints suture of lacerations paronychia, abcess

Peripheral Nerve Blocks DIGITAL NERVE BLOCK Digital branches of ulnar, median, radial Indications: minor procedure in fingers Reminder: avoid using large volume of LA do not add vasoconstrictors

Proximal nerve blocks on lower extremity Femoral nerve block Sciatic nerve block Obturatory nerve block Lateral cutaneous femoral nerve block Lumbar plexus Lumbar paravertebral block Psoas compartment block

Distal Nerve Blocks on the leg ANKLE BLOCK Blocks five nerves supplying foot a. Deep peroneal b. Superficial peroneal c. Saphenous d. Posterior tibial e. Sural Indications Surgery of foot and toes in frail patients who cannot tolerate hemodynamic effects of GA or neuraxial block

Distal Nerve Blocks on the leg ANKLE BLOCK Precaution Avoid epinephrine to reduce risk of ischemia Complication Intravascular injection

Peripheral Nerve Blocks PUDENDAL NERVE BLOCK sacral plexus (S2 – S3 – S4) Indications perineal surgery hemorrhoids lacerations obstetric vaginal delivery Complications puncture of fetal head inadvertent IV infection

Peripheral Nerve Blocks DORSAL PENILE BLOCK Base of penis at symphysis pubis Blocks dorsal nerve Fan-shaped injection at the base blocks dorsal and ventral branches Indications Penile surgery Post-op pain relief

Peripheral Nerve Blocks DORSAL PENILE BLOCK Precautions Avoid big volume of solution Avoid epinephrine or any vasoconstrictor Complication Artery spasm – ischemic injury to penis

Central Blocks = Neuroaxial anesthesia A. SPINAL ANESTHESIA Sub Arachnoid Block, Intrathecal Block Local anesthestic deposited at subarachnoid space Acts on spinal nerve roots, dorsal ganglia, not on substance of spinal cord Redistributed via vascular absorption Produces sympathetic block, sensory analgesia and motor block

Indications Surgery involving lower half of body Upper abdomen Lower abdomen Perineum Lower Extremity Obstetrics – vaginal delivery Caesarian section Painful diagnostic and therapeutic procedures below diaphragm

Contraindications Absolute Relative Bleeding disorders Septicemia Inc. intracranial pressure Chronic dermatitis or infection near puncture site Pre-existing spinal cord disease Hypotension Patient refusal Systemic disease with neurologic sequelae Relative Hemorrhage Back problem due to muscle strain, arthritis Extremely tense / psychotics Respiratory disease

Drugs Used Factors Determining Level of Anesthesia Tetracaine Lidocaine Bupivacaine Factors Determining Level of Anesthesia volume of solution concentration barbotage speed of injection patient position specific gravity of solution site of injection height of patient increased intra-abdominal pressure

Technique Interspaces between L2-L3, L3-:4, L4-L5 A. Position Lateral decubitus – knees flexed to chest hin put down on chest (nose-to-knee) Sitting – when lateral approach is difficult (e.g. obese patients) B. Puncture Sites Interspaces between L2-L3, L3-:4, L4-L5 Line joining highest points of iliac crests crosses either body of L4 or interspace between L3-L4

Structures Traversed By Spinal Needle a. Skin b. Subcutaneous Tissue c. Supraspinous ligament d. Interspinuous ligament e. ligamentum flavum f. Dura

PHYSIOLOGIC EFFECTS (Immediate Complications) A. Cardiovascular Sympathectomy  vasodilation   BP,  CR B. Respiratory Difficulty of breathing Apnea (high level) C. Gastrointestinal Nausea / vomiting in 20% DELAYED COMPLICATIONS Headache – leak of CSF Backache Urinary retention Paraplegia – hematoma

Levels of Spinal Anesthesia – Dermatomes Involved Saddle Block – sensory loss involves lowers lumbar and sacral segments. Area that “sits on the saddle”. Low Spinal – level of umbilicus (T10) lower thoracic lumbars and sacrals. Mid-Spinal – costal margin (T6) lower thoracic lumbars and sacrals High Spinal – nipple line (T4) thoracic segments (T4 – T12) lumbars and sacrals

Central Blocks B. EPIDURAL ANESTHESIA Anatomy Epidural space – base of skull (foramen magnum) to the coccyx (sacrococcygeal membrane) Distance from skin to epidural space – 4-5 cm Epidural space contains loose areolar tissue, fat, arterial and venous networks, lymphatics, spinal nerve roots LA deposited in epidural space Block spinal nerve roots that traverse peridural space Blocks sympathetic nerves traveling with the anterior roots Applications range from sensory analgesia, minimal motor block, or dense anesthesia and full motor block – controlled by drug choice, concentration, dosage

Types – selective blockade possible because it can be performed at any level of spine Cervical epidural Thoracic epidural Lumbar epidural Caudal epidural Factors Influencing Spread of Solution Height of patient Drugs used Volume Concentration Level of puncture and catheter insertion

Technique Lateral Decubitus, full flexion Method Position Single dose injection Fractional – continuous epidural – repeated injections of LA through catheter inserted into epidural space Position Cervical epidural – sitting (C7) Thoracic epidural (T7) Lumbar epidural (L1-L2, L2-L3, L3-L4, L4-L5) Lateral Decubitus, full flexion

Method of Identifying Epidural Space Principle: negative pressure in space Loss of resistance Plunger of syringe pushed without resistance once epidural needle is in Hanging Drop Drop of saline at hub of epidural needle is sucked in once it enters space

Indications All operations below diaphragm May be used in Poor risk patients Cardiac diseases Pulmonary diseases Metabolic disturbances When GA is contraindicated When spinal anesthesia is contraindicated Painful conditions including post-op pain relief

Contraindications – similar to spinal Severe hemorrhage Coagulation defects Previous laminectomy Uncooperative / apprehensive Local inflammation at site Patient refusal Advantages Well-defined area of anesthesia Longer duration More severe disturbances of spinal anesthesia minimized GI complaints minimized Catheterization minimized Less respiratory effects

Drugs: low-dose LA, opiods Disadvantages Technically more difficult Muscle relaxation not complete Large volume necessary Danger of dural puncture Incomplete / patchy block Physiologic Effects Similar to those observed in spinal anesthesia Slower onset Less intensity of motor and sensory block Drugs: low-dose LA, opiods

Central Blocks C. CAUDAL ANESTHESIA LA injected into the epidural space in the sacral canal through sacral hiatus Blocks lumbosacral plexus (T12, L1-5, S1-3) and coccygeal plexus (S4-5, coccygeal nerves) Indications OB – vaginal deliveries Surgery involving lower abdomen, perineum Post-op pain control following these surgeries especially pediatric patients

Technique Patient prone or lateral Needle inserted into sacral hiatus 15-20 ml Lidocaine Physiologic Effects Similar to lumbar epidural Related to level achieved – volume of drug

Complications Accidental Dural puncture General systemic reactions Infection at site of injection Disadvantages Difficult to obtain high level Needs big amount – systemic reactions possible Infection possible 5-10% failure – anatomic anomalies or incorrect method

THANK YOU