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
History
• 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
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7 Cervical
12 Thoracic
5 Lumbar
5 Sacral
4 Coccygeal
Anatomy
Anatomy
Anatomy
• Spinal cord ends in
– Neonate L3-4
– Adult L1
• Dural ends in
– Neonate S4
– Adult 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
• Principle site of action : nerve root
• Anterior nerve root:
efferent motor and autonomic
outflow
• Posterior nerve root:
somatic & visceral sensation
Spinal Anesthesia
• Indications & Advantages
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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 Anesthesia
Indications
Acute Pain Syndromes
Chronic 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:
iliac crest spinous
processL4-5
Spinal Technique
• Midline Approach
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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
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More common in women ages 13-40
Larger needle size increase severity
Onset typically occurs first or second day post-op
Treatment:
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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
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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:
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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 Blockade
• Spinal nerve roots : mixtures of
fiber types
• Concentration gradients
• Typically results in sympathetic
blockade 2 segments higher than
sensory block
Autonomic Blockade
• Cardiovascular effect
– Typically, ↓BP
– May be ↓HR and cardiac contractility
 degree (level) of sympathectomy
– Venodilation : sympathetic block
– Venous return & SVR 
– HR : sympathetic cardiac accelerator fiber T1-4
Autonomic Blockade
• Cardiovascular effect
– Minimize degree of hypotension
• Volume loading 10-20 mL/kg
• Head-down position
• Vasopressor drug
• Left uterine displacement
Autonomic Blockade
• Respiratory effects
High spinal block : intercostal, abdominal m.
paralysis
– Caution in patients severe lung disease
block T7
Autonomic Blockade
• Gastrointestinal function
– Vagal tone dominant → contracted gut
with active peristalsis
• Urinary tract
– renal function
– Loss of autonomic bladder
control→urinary retention
• Metabolic & endocrine
Resuscitation
• Vasopressor
• resuscitation
Needles
Drug Doses & Block Levels
LEVEL
0.5% Heavy
bupivacaine
0.5% Isobaric
bupivacaine
Time
L4
T10
T4
4-8 mg
8-12 mg
14-20 mg
90-110
mins
10-15 mg
15-20 mg
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180 mins
Factors affecting level of SB
• Baricity of anesthetic solution
• Position of patient
• Drug dosage
• Site of injection
Complication
Acute
Late
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