Central Nerve Blocks

Mostafa Kamel

February 2010

Regional Anesthesia• Objectives

– History – Anatomy– Identify Anatomic Landmarks – Define Steps for spinal, epidural, or caudal needle– Distinguish level of anesthesia after administration of

regional– Factors affecting level and duration of block– Explain potential complications and treatments

Regional anesthesia - Definition

Rendering a specific area of the body, e.g. foot, arm, lower extremities, insensate to stimulus of surgery or other instrumentation

HistoryHistory

• 1860 - cocaine isolated from erythroxylum coca

• Koller - 1884 uses cocaine for topical anesthesia

• Halsted - 1885 performs peripheral nerve block with local

• Bier - 1899 first spinal anesthetic

Spinal Anatomy

• 33 Vertebrae– 7 Cervical

– 12 Thoracic

– 5 Lumbar

– 5 Sacral

– 4 Coccygeal

Anatomy Anatomy

Anatomy Anatomy

Anatomy Anatomy

• Spinal cordSpinal cord ends in ends in– Neonate L3-4Neonate L3-4

– Adult L1Adult L1

• DuralDural ends in ends in– Neonate S4Neonate S4

– Adult S2Adult S2

Epidural Space

• Space that surrounds the spinal meninges– Potential space

• Ligamentum Flavum– Binds epidural space posteriorly

• Widest at Level L2 (5-6mm)

• Narrowest at Level C5 (1-1.5mm)

Physiology Physiology

• Principle site of action : nerve rootPrinciple site of action : nerve root

• Anterior nerve rootAnterior nerve root::

efferent motor and autonomic outflowefferent motor and autonomic outflow

• Posterior nerve rootPosterior nerve root::

somatic & visceral sensationsomatic & visceral sensation

Spinal Anesthesia

• Indications & Advantages– Full stomach– Anatomic distortions of upper airway– TURP surgery– Obstetrical surgery (T4 Level)– Decreased post-operative pain– Continuous infusion

The Good

• Cheap

• High Patient Satisfaction

• Well Tolerated in Pulmonary Disease

• Maintain Patent Airway

• Selective Muscle Relaxation

• Decreased Blood Loss

• Decreased Incidence of DVT and PE

The Bad

• Difficult Placement in Elderly

• Hypotension

• Patient Can Talk

• Patient Anxiety

• Not Reliable for Surgery > 2 hours

The Ugly

• Bleeding

• Post-Dural Puncture Headache

• Transient Neurological Syndrome

• Total Spinal

Total Spinal

• Hypotension

• Bradycardia

• Arm involvement

• Shortness of Breath

• Patient Anxiety

• Loss of Consciousness

Epidural AnesthesiaIndications

Acute Pain SyndromesAcute Pain Syndromes Chronic Pain SyndromesChronic Pain Syndromes

Intra & post operatively Low Back Pain

AHZ PHN

Ischemic pain CRPS

Renal pain Spinal Cord Stimulators

Visceral Abdominal Pain Chronic Malignancy

Obstetric analgesia Epiduroscopy

The Good

• Cheap

• High Patient Satisfaction

• Well Tolerated in Pulmonary Disease

• Maintain Patent Airway

• Selective Muscle Relaxation

• Decreased Blood Loss

• Decreased Incidence of DVT and PE

The Bad

• Difficult Placement in Elderly

• Hypotension

• Patient Can Talk

• Patient Anxiety

The Ugly

• High Epidural

• Local Anesthetic Toxicity

• Total Spinal

• Accidental Dural Puncture

Contra-Indications for Regional Anesthesia

• Patient Refusal• Coagulopathy• Localized Skin Infection• Elevated ICP• Hypovolemia• Uncooperative Patient• Pre-Existing Neurological Disease• Spinal Column Abnormalities• Fixed Cardiac Output States

Spinal Technique

• Preparation & Monitoring– EKG

– NBP

– Pulse Oximeter

• Patient Positioning– Lateral decubitous

– Sitting

– Prone (hypobaric technique)

Landmark Landmark

• landmark:landmark:

iliac crest spinous iliac crest spinous

processprocessL4-5L4-5

Spinal Technique• Midline Approach

– Skin

– Subcutaneous tissue

– Supraspinous ligament

– Interspinous ligament

– Ligamentum flavum

– Epidural space

– Dura mater

– Arachnoid mater

• Paramedian or Lateral Approach– Same as midline excluding supraspinous &

interspinous ligaments

Spinal Anesthesia Levels

Spinal Anesthesia• Complications

– Failed block– Back pain (most common)– Spinal head ache

• More common in women ages 13-40

• Larger needle size increase severity

• Onset typically occurs first or second day post-op

• Treatment:– Bed rest

– Fluids

– Caffeine

– Blood patch

Epidural Anesthesia

• Order of Blockade– B fibers– C & A delta fibers

• Pain• Temperature• Proprioception

– A gamma fibers– A beta fibers– A alpha fibers

Epidural Anesthesia• Test Dose: 1.5% Lido with Epi 1:200,000

– Tachycardia (increase >30bpm over resting HR)

– High blood pressure

– Light headedness

– Metallic taste in mouth

– Ring in ears

– Facial numbness

– Note: if beta blocked will only see increase in BP not HR

• Bolus Dose: Preferred Local of Choice– 10 milliliters for labor pain

– 20-30 milliliters for C-section

Epidural Anesthesia

• Distances from Skin to Epidural Space– Average adult: 4-6cm– Obese adult: up to 8cm– Thin adult: 3cm

• Assessment of Sensory Blockade– Alcohol swab

• Most sensitive initial indicator to assess loss of temperature

– Pin prick• Most accurate assessment of overall sensory block

Caudal Anesthesia

• Anatomy– Sacrum

• Triangular bone

• 5 fused sacral vertebrae

• Needle Insertion– Sacrococcygeal membrane

– No subcutaneous bulge or crepitous at site of injection after 2-3ml

Caudal Anesthesia

• Post Operative Problems– Pain at injection site is most common– Slight risk of neurological complications– Risk of infection

• Dosages– S5-L2: 15-20ml– S5-T10: 25ml

Cardiovascular Effects

• Blockade of Sympathetic Preganglionic Neurons– Send signals to both arteries and veins– Predominant action is venodilation

• Reduces: – Venous return– Stroke volume– Cardiac output– Blood pressure

– T1-T4 Blockade• Causes unopposed vagal stimulation

– Bradycardia» Associated with decrease venous return & cardioaccelerator fibers

blockade» Decreased venous return to right atrium causes decreased stretch

receptor response

Hypotension

• Treatment– Best way to treat is physiologic not

pharmacologic– Primary Treatment

• Increase the cardiac preload– Large IV fluid bolus within 30 minutes prior to spinal

placement, minimum 1 liter of crystalloids

– Secondary Treatment• Pharmacologic

– Ephedrine is more effective than Phenylephrine

Respiratory System

• Healthy Patients– Appropriate spinal blockade has little effect on

ventilation

• High Spinal– Decrease functional residual capacity (FRC)

• Paralysis of abdominal muscles

• Intercostal muscle paralysis interferes with coughing and clearing secretions

• Apnea is due to hypoperfusion of respiratory center

Differential BlockadeDifferential Blockade

• Spinal nerve roots : mixtures of fiber Spinal nerve roots : mixtures of fiber typestypes

• Concentration gradientsConcentration gradients

• Typically results in sympathetic Typically results in sympathetic blockade 2 segments higher than blockade 2 segments higher than sensory blocksensory block

Autonomic Blockade Autonomic Blockade • Cardiovascular effectCardiovascular effect

– Typically, ↓BPTypically, ↓BP

– May be ↓HR and cardiac contractilityMay be ↓HR and cardiac contractility

degree (level) of sympathectomy degree (level) of sympathectomy

– Venodilation : sympathetic blockVenodilation : sympathetic block

– Venous return & SVR Venous return & SVR

– HR HR : sympathetic cardiac accelerator fiber T1-4: sympathetic cardiac accelerator fiber T1-4

Autonomic Blockade Autonomic Blockade • Cardiovascular effectCardiovascular effect

– Minimize degree of hypotensionMinimize degree of hypotension

• Volume loading 10-20 mL/kgVolume loading 10-20 mL/kg

• Head-down positionHead-down position

• Vasopressor drugVasopressor drug

• Left uterine displacementLeft uterine displacement

Autonomic BlockadeAutonomic Blockade • Respiratory effectsRespiratory effects

High spinal block : intercostal, abdominal m. High spinal block : intercostal, abdominal m.

paralysisparalysis

– Caution in patients severe lung disease Caution in patients severe lung disease

block T7block T7

Autonomic BlockadeAutonomic Blockade• Gastrointestinal functionGastrointestinal function

– Vagal tone dominant → contracted gut Vagal tone dominant → contracted gut with active peristalsiswith active peristalsis

• Urinary tractUrinary tract– renal functionrenal function

– Loss of autonomic bladder Loss of autonomic bladder controlcontrol→urinary retention→urinary retention

• Metabolic & endocrineMetabolic & endocrine

Resuscitation

• VasopressorVasopressor

• resuscitationresuscitation

Needles Needles

Drug Doses & Block LevelsDrug Doses & Block Levels

LEVEL Time

L4 T10 T4

0.5% Heavy bupivacaine

4-8 mg 8-12 mg 14-20 mg

90-110 mins

0.5% Isobaric bupivacaine

10-15 mg

15-20 mg

- 180 mins

Factors affecting level of SBFactors affecting level of SB

• Baricity of anesthetic solutionBaricity of anesthetic solution

• Position of patientPosition of patient

• Drug dosageDrug dosage

• Site of injectionSite of injection

Complication Complication

Acute Acute LateLate

Cardiac arrest Backache

High/Total spinal Urinary retention

Anaphylaxia Transient Neurologic Symptoms (TNS)

Systemic toxicity Postdural puncture headache (PDPH)

Hypotension Cauda Equina Syndrome

Meningitis & Arachnoiditis

Epidural abscess

Thank you

for your

attention