central nerve blocks mostafa kamel february 2010
TRANSCRIPT
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Central Nerve Blocks
Mostafa Kamel
February 2010
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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
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Regional anesthesia - Definition
Rendering a specific area of the body, e.g. foot, arm, lower extremities, insensate to stimulus of surgery or other instrumentation
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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
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Spinal Anatomy
• 33 Vertebrae– 7 Cervical
– 12 Thoracic
– 5 Lumbar
– 5 Sacral
– 4 Coccygeal
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Anatomy Anatomy
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Anatomy Anatomy
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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
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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)
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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
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Spinal Anesthesia
• Indications & Advantages– Full stomach– Anatomic distortions of upper airway– TURP surgery– Obstetrical surgery (T4 Level)– Decreased post-operative pain– Continuous infusion
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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
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The Bad
• Difficult Placement in Elderly
• Hypotension
• Patient Can Talk
• Patient Anxiety
• Not Reliable for Surgery > 2 hours
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The Ugly
• Bleeding
• Post-Dural Puncture Headache
• Transient Neurological Syndrome
• Total Spinal
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Total Spinal
• Hypotension
• Bradycardia
• Arm involvement
• Shortness of Breath
• Patient Anxiety
• Loss of Consciousness
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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
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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
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The Bad
• Difficult Placement in Elderly
• Hypotension
• Patient Can Talk
• Patient Anxiety
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The Ugly
• High Epidural
• Local Anesthetic Toxicity
• Total Spinal
• Accidental Dural Puncture
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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
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Spinal Technique
• Preparation & Monitoring– EKG
– NBP
– Pulse Oximeter
• Patient Positioning– Lateral decubitous
– Sitting
– Prone (hypobaric technique)
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Landmark Landmark
• landmark:landmark:
iliac crest spinous iliac crest spinous
processprocessL4-5L4-5
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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
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Spinal Anesthesia Levels
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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
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Epidural Anesthesia
• Order of Blockade– B fibers– C & A delta fibers
• Pain• Temperature• Proprioception
– A gamma fibers– A beta fibers– A alpha fibers
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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Resuscitation
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• VasopressorVasopressor
• resuscitationresuscitation
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Needles Needles
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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
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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
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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
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