Central Nerve Blocks

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Central Nerve Blocks : 

Central Nerve Blocks Hosam Atef, MD Lecturer Pain Management/Anesthesiology

Introduction : 

Introduction Targets Epidural Space Interlaminar (Cervical, Thoracic, Lumbar) Midline Paramedian Transforaminal (Cervical, Thoracic, Lumbar, Sacral) Caudal (Sacral) Subarachnoid Space Methods Block Catheter Lead Safety Issues

Anatomic Considerations : 

Anatomic Considerations Dural sac contiguous to cranium Dural sac bounds spinal structures Inside Spinal cord and nerve roots Subarachnoid space (pia, arachnoid mater, blood vessels, CSF) Outside Epidural space (ends at upper cervical spine) Subdural space (contiguous with tentorium)

Anatomic Considerations : 

Anatomic Considerations

Anatomic considerations : 

Anatomic considerations Epidural space: Boundaries Anterior: PLL Posterior: LF, lamina Lateral: pedicles, intervertebral foramina Distance skin to cervical epidural space (cm) (Han, et. al. RAPM) Distance skin to low thoracic epidural space (cm) is also about 5.5cm (Kao, et. al, BJA 2004) Distance skin to lumbar epidural space (cm) is also about 5.9cm +/- 1.2cm (Bevacqua, et. al, RAPM 1996, Hoffmann, Anaesthesia 1997)

Anatomic considerations : 

Anatomic considerations Cervical epidural space size (mm) MRI (Aldrete, et. al.) increases with flexion decrease with extension Lumbar epidural space size Distance from loss of resistance to dural puncture (Bevacqua) 6.9 mm +/- 4mm (Bevacqua) 7-8.9 mm ( Hoffmann) Contents Fat Veins Arteries Lymphatics

Anatomic Considerations : 

Anatomic Considerations Bony anatomy of the cervical spine

Anatomic considerations : 

Anatomic considerations Cervical spine radiographs

Anatomic Considerations : 

Anatomic Considerations Bony anatomy of C3-C7: AP: bifid spinous processes, lamina, waists of lateral masses, uncinate processes, vertebral bodies, intervertebral discs

Anatomic Considerations : 

Anatomic Considerations Bony anatomy of C3-C7: Lateral: spinous processes, lamina, lateral masses, vertebral bodies, intervertebral discs

Anatomic Considerations : 

Anatomic Considerations Left lateral oblique view Posterior View Bony anatomy of the lumbar spine

Anatomic considerations : 

Anatomic considerations Lumbar spine radiographs

Anatomic considerations : 

Anatomic considerations Lumbar spine radiographs

Neuraxial Procedures : 

Neuraxial Procedures Subarachnoid Procedures Indications Spinal anesthesia Spinal analgesia

Neuraxial Procedures : 

Neuraxial Procedures Subarachnoid Procedures Neuraxis medication issues Local anesthetic spread *Baricity >CSF= hyperbaric, lower lying areas =CSF=isobaric, tends to remain at injection point <CSF=hypobaric, higher lying areas *Patient position following injection Level of injection Speed of injection Dose and volume used Barbatoge *most important factors Local anesthetic duration Drug used Dose injected Spread achieved Vasoconstrictors Age and general condition of patient Lidocaine 50 mg to achieve T10 block, isobaric Duration approximately 60-90 minutes Bupivacaine 10 mg to achieve T10 block, isobaric Duration approximately 90-150 minutes

Neuraxial Procedures : 

Neuraxial Procedures Subarachnoid Technique Needle Variable diameter and length Impacts size of hole and rapidity with which CSF appears at the hub Post-dural puncture headache may be minimized A pencil point: Whitacre, Sprotte, Gertie Marx A cutting needle that runs parallel to the dural fibers: Quincke Smaller diameter Position Lateral decubitus Prone Sitting Chin to chest Knee to chest Slight flexion reduces lumbar lordosis Easier to identify free flow of CSF Interspace selection Identify superior portion of iliac crests and connect them Intercristal line or Truffer’s line crosses L4 spinous process or L4-5 interspace Sterile preparation Midline approach Introducer followed by 25-27 gauge needle Needle is aimed parallel to floor or slightly cephalad Skin  supraspinous ligament  interspinous lig.  ligamentum flavum  epidural space  dural space  subarachnoid ‘Pop’ with CSF filling the needle hub Bone contact requires redirection: lamina or spinous process

Neuraxial Procedures : 

Neuraxial Procedures

Neuraxial Procedures : 

Neuraxial Procedures Subarachnoid Problems Direct consequence of neural blockade physiology: high spinal Nausea Vomiting Hypotension Bradycardia Post-dural puncture headache Spontaneous intracranial hypotension Intracranial subdural hematoma Back ache Urinary retention Transient radicular irritation Cauda equina Infection

Neuraxial Procedures : 

Neuraxial Procedures Epidural Indications Epidural anesthesia Radicular pain syndromes Acute pain General anatomy: already reviewed Relevant Anatomy C7- most prominent spinous process T7 vertebral body is at the line connecting the inferior poles of the scapula L1 vertebral body is at the line connection the 12th ribs L4 vertebral body is at the intercristal line S2 is at the level of the postero-superior iliac spines (PSIS) Relevant structures Midline: skin, supraspinous ligament, interspinous ligament ligamentum flavum Approach Cervical: midline or paramedian or transforaminal Thoracic: paramedian or transforaminal Lumbar: midline or paramedian or transforaminal Sacral: caudal or transforaminal Patient positioning: lateral decubitus, prone, and seated (except sacral)

Neuraxial Procedures : 

Neuraxial Procedures Epidural Cervical Flex spine Lateral C7-T1 is most common entry…but wait Ligamentum flavum may be absent in the cervical levels Lirk, et. al., Anesthesiology 2003 52 cadavers Midline gaps C3–C4: 66% C4–C5: 58% C5–C6: 74% C6–C7: 64% C7–T1: 51% Th1–Th2: 21% Th2–Th3: 11% Th3–Th4: 4% Th4–Th5: 2% Th5–Th6: 2% Mean width of mid-line gaps was 1.0 ± 0.3 mm.

Neuraxial Procedures : 

Neuraxial Procedures

Neuraxial Procedures : 

Neuraxial Procedures Epidural Technique Cervical Loss of resistance or hanging drop Bromage technique for needle advancement Skin wheal Epidural needle 14g (spinal cord stimulator) to 20g (steroids) Insert needle 3-4 cm Remove stylet and advance needle cephalad or caudally, if bony structures are encountered at 2-4 cm Paramedian approach is easier in lateral decubitus Skin wheal is 1cm lateral to midline Aim medially at a 15-20 degree in sagittal plane Fluoroscopy with non-ionic dyes are preferred 53% failure of initial loss of resistance to access the epidural space Only 28% demonstrated ventral epidural spread

Neuraxial Procedures : 

Neuraxial Procedures Cervical epidural injections Interlaminar Ideally under fluoroscopy due to high false positive rate when blind (53%) Can provide long term pain control if inflammation is a significant component Rare but serious complications Cord injury Vascular uptake Subarachnoid injection

Neuraxial Procedures : 

Neuraxial Procedures Cervical epidural injections Selective nerve root block (transforaminal) Precise symptomatic nerve identification Mix with a short and long acting local anesthetic to improve diagnostic sensitivity Blunt curved RF needle reduces risk of nerve injury and vascular uptake ?DSA Additionally, the latter can be coupled to use electro-localization to improve sensitivity Pulsed mode EMF of the DRG can be used to reduce radicular pain

Neuraxial Procedures : 

Neuraxial Procedures Cervical epidural injections Selective nerve root block (transforaminal)

Neuraxial Procedures : 

Neuraxial Procedures Cervical epidural injections DRG RF (Yin and Kline)

Neuraxial Procedures : 

Neuraxial Procedures Cervical epidural adhesiolysis and three-stage decompressive neuroplasty (Cervical 3-D) HNP, DDD, stenosis are frequently associated with epidural scarring, which can irritate or compress exiting nerve roots Epidurography coupled with nerve stimulation can identify the most symptomatic root Local anesthetic, steroids, hyaluronidase, and hypertonic saline are all used to help alleviate symptoms, reduce inflammation, break up scar and improve neural function

Cervical 3-D : 

Cervical 3-D Technique Guiding principles Plan to place catheter at target level based on clinical evaluation, imaging, and physiologic studies Needle entry at T1-2 to avoid dural puncture Shallow paramedian approach 3-D approach: ‘direction-depth-direction’ Good fluoroscopic imaging Interpretation of the epidurogram Bimanual catheter steering

Cervical 3-D : 

Cervical 3-D Position Lateral decubitus-preferred Non-involved side down for comfort Pillow under head to level out C-spine If bilateral symptoms, then position patient based on dominant hand of operator Prone and sitting- less desirable ensure that patient does not move Operating room Sterile preparation Pressure points padded Monitored anesthetic care

Cervical 3-D : 

Cervical 3-D AP fluoro view spinous processes should be dead center accept no compromise Skin entry point radiopaque pointer 1-1 ½ segments below T1-2 start on CONTRALATERAL SIDE approximately 1 cm paramedian to spinous process skin wheal with 25 or 27 gauge needle and 1.5% lidocaine 18 gauge needle to puncture skin in order to facilitate passage of larger epidural needle

Cervical 3-D : 

Cervical 3-D Epidural needle RX Coude´ TM needle, 16 gauge Bent at its distal tip to allow easier steerability RK TM needle, 16 gauge

Cervical 3-D : 

Cervical 3-D Insert through skin entry point (RX coude) concave side (bevel) initially pointing caudad (downward) Needle should aim for the midline (DIRECTION) shallow paramedian approach, 70-80 degrees to skin Intermittently advance but stop before reaching interlaminar window stop at superior aspect of inferior laminar edge stop at base of spinous process

Cervical 3-D : 

Cervical 3-D Switch to lateral fluoro view (DEPTH) Needle tip is parallel to the dura

Cervical 3-D : 

Cervical 3-D Lateral view visualize anterior portion of spinous processes… like a ‘dash’ connect the ‘dashes’… like an imaginary ’straight line’ Switch back to the AP to confirm final position, before reaching this ‘straight line’ (DIRECTION) Then switch to a lateral view and access the epidural space with loss of plunger bounce pulsator syringe 4 cc preservative free normal saline 2 cc air

Cervical 3-D : 

Cervical 3-D Rotate needle bevel cephalad Needle tip is now parallel to the dura

Cervical 3-D : 

Cervical 3-D Epidurogram 3-4 cc, iodinated nonionic contrast (OmnipaqueTM 240 mg/dl) to ensure that the spread is epidural Confirms absence of subarachnoid, vascular, or subdural spread

Cervical 3-D : 

Cervical 3-D TunL-XL 24™ or Brevi-XL™ catheters 19 gauge 24” (TunL-XL 24) or 12” (Brevi-XL) radio-opaque steerable round, deflective atraumatic tip stainless steel coils, spring wound fluoropolymer coated styletted

Cervical 3-D : 

Cervical 3-D Needle tip can be rotated to enhance directional steering of catheter

Cervical 3-D : 

Cervical 3-D Catheter is bent 10 degrees at its terminal 2-3cm portion Catheter is steered to area corresponding to cervical pathology or epidural scarring

Cervical 3-D : 

Cervical 3-D Ideally catheter placement should be near lateral gutter Monopolar electrical stimulation is used to identify symptomatic spinal nerve

Cervical 3-D : 

Cervical 3-D Catheter can be easily steered cephalad

Cervical 3-D : 

Cervical 3-D …or caudad contrast spread through catheter is lateral due to patient positioning

Neuraxial Techniques : 

Neuraxial Techniques Thoracic Similar principles to cervical Paramedian technique Identify the space between two spinous processes Skin wheal 1-1.5 cm lateral to this midline Epidural needle is entered perpendicularly Advance till lamina encountered Pull needle back 0.5 cm and re-directed at 15-20 angle in axial plane and 45 degrees in sagittal plane Walk off lamina

Neuraxial Techniques : 

Neuraxial Techniques Thoracic Left paramedian approach T4-5 Enter 1-1.5 cm lateral to the interspinous process of T4 and T5 Advance sagittally till bony contact is made with lamina Withdraw needle approximately 2cm Redirect at 45 degree sagitally and 15 degree medially Repeat bony contact implies lamina or spinous process Loss of resistance

Neuraxial Techniques : 

Neuraxial Techniques

Neuraxial Procedures : 

Neuraxial Procedures Epidural Technique Lumbar Similar principles as cervical spine Lateral decubitus, prone, sitting If sitting: Chin to chest Knee to chest Slight flexion reduces lumbar lordosis If prone Pillow under the belly Facilitates fluoroscopy Skin wheal in the midline between spinous processes The skin wheal needle can be used to identify the caudal spinous process Advance the epidural needle, approximately 3-3.5 cm When anchored in the interspinous ligament, switch to loss of resistance technique Confirm negative aspiration In paramedian technique 1.5 cm lateral to inferior edge of caudal spinous process Advance 15 degrees in sagittal plane

Neuraxial Blocks : 

Neuraxial Blocks Epidural Lumbar Bromage grip Continued pressure on the syringe as needle is advanced

Epidural analgesia : 

Epidural analgesia Versatile Provides analgesia from upper chest to toes Prolong duration of effect with use of catheter Improves physiology Pulmonary function Increased lower limb blood flow Decreased incidence of thromboembolic complications Attenuates neuroendocrine response to surgery Decreased myocardial demand Increased GI motility Barriers Technical considerations Close monitoring

Epidural analgesia : 

Epidural analgesia Local anesthetics Sensory, motor, sympathetic blockade Block intensity dependent on concentration and total dose used Catheter placed to approximate the location of the surgery Low concentrations are used in post-operative period Combination with opioid can provide better analgesia while avoiding some side effects and permitting ambulation Ropivacaine can provide less and shorter duration motor block compared to equal concentrations of bupivicaine Ropivacaine can provide less adverse CNS and CVS effects Ropivacaine has a better dose dependent dissociation between sensory and motor block at low concentrations Usual doses are 0.1% ropivacaine or 0.0625% bupivacaine

Epidural analgesia : 

Epidural analgesia Opioids Initial clinical use in 1979 Provide significant post-operative analgesia with fewer side effects compared to systemic administration Absence of sensory, motor, sympathetic block Pharmacokinetics are influenced by Epidural vascularity Epidural fat Penetration of dura Lipophillicity: facilitates systemic absorption

Epidural Analgesia : 

Epidural Analgesia Opioids Lipophillic agents (fentanyl, sufentanil) Rapid onset Shorter duration Segmental analgesic effect, hence greater dependence on location of catheter Better suited for continuous infusion Hydrophillic agents (morphine) Slower onset Longer duration Slow clearance, hence facilitating greater rostral spread Caudal or lumbar administered morphine can provide analgesia for upper abdominal or thoracic surgery Better suited for intermittent bolusing (2/day)

Epidural Analgesia : 

Epidural Analgesia Adverse reaction Pruritis: central mu receptor mediated and abolished by small doses of naloxone Urinary retention: weakens strength of detrusor muscle and thus increase in size of bladder volume Respiratory depression: particularly with large doses, age, high risk, opioid naïve, concomitant administering of other agent

Epidural Analgesia : 

Epidural Analgesia PCEA Usually with more lipophillic agents, i.e., rapid onset Shorter hospitalization Self-titration Standard mix is 0.1% ropivacaine with 5 mcg/cc fentanyl for a rate that varies from 6-12 cc/hour

Neuraxial Techniques : 

Neuraxial Techniques Epidural Lumbar Transforaminals or Selective Nerve Root Blocks First described by Macnab and Krempen in the 1970’s Identify the neuronal pathway mediating nociception Assess the patient’s pain reproduction during injection of medication Assess the patient’s pain relief during the anesthetic phase by attempting to reproduce provocative postures or movements Assess spread and washout of instilled contrast Diagnostic blocks can differentiate between central vs. peripheral pain, somatic vs. visceral, and sympathetic vs. somatic Addition of corticosteroid, renders these blocks as potentially therapeutic as well; usually used synonymously with transforaminal epidural injections Indicated for large disc protrusions, foraminal disk herniations, foraminal or lateral recess stenosis

Lumbar Transforaminal Epidural : 

Lumbar Transforaminal Epidural Botwin, et. al. Arch of PM&R 2000 No major complications 9.6% minor complication rate ‘safe’ triangle concept: needle lateral and above exiting spinal nerve

Lumbar Transforaminal Epidural : 

Lumbar Transforaminal Epidural Houten, Spine J 2002 3 cases of paraplegia following TFESIs ? Not –so safe triangle Low riding radiculomedullary artery and vascular injury …posterolateral approach and blunt needles

Lumbar Transforaminal Epidural : 

Lumbar Transforaminal Epidural Epidural Technique Lumbar transforaminal Align C-arm obliquely 15 degrees ipsilaterally to view the ‘Scotty’ dog Align C-arm cephalo-caudally 15 degrees so that the superior articular process of the inferior vertebral body, i.e., ear, is elongated A 16 gauge 3 ¼ in angiocath is advanced in a gun barrel fashion to the mid-portion of the elongated pars Through this, a 20 gauge curved RK needle is advanced towards a point just lateral to the superior pars; the bevel should initially aim laterally and then rotated back medially One will usually sense a pop (intertransverse ligament)

Lumbar Transforaminal Epidural : 

Lumbar Transforaminal Epidural Epidural Technique Lumbar transforaminal In an AP view, the needle should be just lateral to the pars interarticularis In the lateral view, the needle will be at the level of the foramen Injection of 2-3 cc of contrast will show the majority outlining the spinal nerve distally with some entering the epidural space Then instill a 1:1 mixture of .5% naropin and 2% lidocaine with 4mg of dexamethasone

Neuraxial Procedures : 

Neuraxial Procedures Epidural Technique Sacral transforaminal Prone C-arm obliqued ipsilaterally Cephalo-caudad tilt such that beam is in the direction of the exiting nerve root 16 g angio cath advanced in gun barrel fashion towards upper outer quadrant of sacral foramen This is followed by insertion of a curved blunt needle The procedure is then similar to that at the lumbar level

Radicular Pain: Selective Nerve Root Block : 

Radicular Pain: Selective Nerve Root Block Technique (S1 root) Prone C-arm obliqued ipsilaterally Cephalo-caudad tilt such that beam is in the direction of the exiting nerve root 16 g angio cath advanced in gun barrel fashion towards upper outer quadrant of sacral foramen This is followed by insertion of a curved blunt RK needle The procedure is then similar to that at the lumbar level

Epidural Adhesiolysis : 

Epidural Adhesiolysis

Epidural Adhesiolysis : 

Epidural Adhesiolysis

Epidural Adhesiolysis and Decompressive Neuroplasty : 

Epidural Adhesiolysis and Decompressive Neuroplasty Epidural adhesiolysis protocol 1000-1500 units of hyaluronidase in 4-6 cc of PFNSS 6-10 cc (depending on level) 0.2% ropivacaine and 4 mg dexamethasone (non-particulate steroid) Initial test dose 2cc to ensure absence of subarachnoid spread Check neurological exam after a few minutes Incrementally instill remainder of solution Needle is removed under fluoroscopy Catheter fixation with 3-0 monofilament suture Antibacterial ointment, op-site, 4x4 dressing and hypofix tape Bacteriostatic filter Wrap up and transfer to PACU Wait a total of 30 minutes to ensure the absence of subdural spread

Epidural Adhesiolysis and Decompressive Neuroplasty : 

Epidural Adhesiolysis and Decompressive Neuroplasty Decompressive neuroplasty Stage 1 (PACU) 6-10 cc 10% hypertonic saline Stage 2 (postoperative day 2), Stage 3 (postoperative day 3) 6-10 cc 0.2% ropivacaine, incremental doses (no steroid) Hypertonic saline solution infusion

Epidural Adhesiolysis and Decompressive Neuroplasty : 

Epidural Adhesiolysis and Decompressive Neuroplasty Contraindications Local or systemic infection Coagulopathy Myelopathy Cervical spine fracture or unstable spine

Neuraxial Procedures : 

Neuraxial Procedures Epidural Technique Caudal Similar principles to cervical in terms of sterile preparation Identify sacral hiatus Firm pressure to identify the coccyx Role the finger from side to side to identify the sacral cornu Needle is inserted at a 120 degree angle to the back Bevel should be upwards to avoid piercing the anterior sacral wall A ‘snap’ may be felt: sacrococcygeal membrane The needle is then dropped to 160 degrees and advanced 5-7 mm In children the dural sac is lower than in adults Useful when sacral and lower lumbar roots require blockade

Neuraxial Procedures : 

Neuraxial Procedures Epidural Problems Local anesthetic toxicity CNS Early: light headed ness, perioral numbness, tingling of the tongue, blurred vision Later: shivering, muscular twitches, confusion, facial tremor Seizures and convulsions Latest: CNS depression characterized by unconsciousness and respiratory arrest TX: ABCs Cardiac Direct myocardial and peripheral vascular activity Potency for cardiac depression High: bupivacaine, tetracaine Moderate: mepivacaine, lidocaine, prilocaine Low: procaine and chloroprocaine Early: increased sympathetic activity Later: further increases in C.O., BP, SVR Latest: CV collapse Hematologic Methemoglobinemia with central cyanosis >600 mg of prilocaine Also possible with benzocaine, very rare Tx: methylene blue 1% Immune system Allergic reactions are rare with amide

Neuraxial Procedures : 

Neuraxial Procedures Epidural Problems Technique specific Spinal nerve neuropathy Anterior spinal artery syndrome: painless paraplegia Adhesive arachnoiditis Hematoma or abscess Meningitis PDPH Back pain

Neuraxial Procedures : 

Neuraxial Procedures Epidural Problems Technique specific Spinal nerve neuropathy Anterior spinal artery syndrome: painless paraplegia Adhesive arachnoiditis Hematoma or abscess Meningitis PDPH Back pain

Epiduroscopy : 

Epiduroscopy

Epiduroscopy : 

Epiduroscopy

Epiduroscopy : 

Epiduroscopy

Epiduroscopy : 

Epiduroscopy

Epiduroscopy : 

Epiduroscopy

Epiduroscopy : 

Epiduroscopy

Epiduroscopy : 

Epiduroscopy

Slide 80: 

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L5

Slide 82: 

C B A

Slide 83: 

L5

Spinal Cord Stimulation : 

Spinal Cord Stimulation

Intrathecal Pump : 

Intrathecal Pump

Intrathecal Pump : 

Intrathecal Pump

Intrathecal Pump : 

Intrathecal Pump

Intrathecal Pump : 

Intrathecal Pump

Intrathecal Pump : 

Intrathecal Pump

Conclusion : 

Conclusion Thank you

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