Neuraxial Anesthesia Flashcards Preview

Advanced Principles- Fall 2018 > Neuraxial Anesthesia > Flashcards

Flashcards in Neuraxial Anesthesia Deck (17)
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How many of each kind of vertebrae are there?

  • Cervical (7)
  • Thoracic (12)
  • Lumbar (5)
  • Sacral (5) fused
  • Coccygeal (4) fused


Where are the high curves and the low curves in the spine?

  • High
    • C5
    • L3
  • Low 
    • T5
    • S2


What are the 5 ligaments of the spine?

Where are they located?

What is their purpose?

  • Supraspinous: C5- sacrum
  • Interspinous: entire length
  • Ligamentum flavum
    • foramen magnum to the sacral hiatus
    • tough wedge-shaped ligament composed of elastin
    • thickest in the midline (3-5 mm at L3)
    • called "yellow ligament"
  • Posterior longitudinal ligament: posterior surface of vertebral bodies (C2- sacrum)
  • Anterior longitudinal ligament: anterior surface of vertebral bodies (C1-sacrum)
  • **Purpose of all ligaments is to stabilize the spine


What are the spinal meninges?

  • Protective membranes that are continuous with the cranial meninges
  • Dura Mater- the thick outer layer
    • begins at foramen magnum and ends caudally at the S2/Dural sac
  • Arachnoid mater- thinner and pressed up against the dura
    • principal physiologic barrier for drugs moving between the epidural space and the spinal cord
    • ends at S2- delicate and nonvascular
  • Pia- very thin and right against the spinal cord
    • separated from arachnoid mater by the CSF in the subarachnoid space


Where does the spinal cord start and finish?

How many nerves does it have?

  • Foramen magnum to conus medullaris
    • terminates anywhere from T12 to L2
    • Usually L1
    • sometimes L3 in peds
  • 31 pairs of spinal nervs, each with anterior and posterior root


How do you remember what the anterior and posterior spinal nerve roots do?



What is a spinal cord segment?

What is a dermatome?

  • Segment- the portion of the spinal cord that gives rise to all the rootlets of a single spinal nerve
  • Dermatome- skin area innerved by a spinal nerve and its segment


What are the noteworthy dermatomes?

  • C6- thumb
  • C7- 2nd and 3rd finger
  • C8- 4th and 5th fingers
    • Phrenic nerve innervating diaphragm
  • T4- nipple
    • cardiac accelerators T1-T4
  • T6- xiphoid
  • T8- last rib
  • T10- umbilicus




Rate produced

specific gravity

  • 150 ml in the subarachnoid space
  • volume replaced 3-4x/day
  • 21 ml produced per hour by choroid plexus
  • Specific gravity: 1.004- 1.008


How is blood supplied to the spinal cord?

  • One anterior spinal artery and two posterior spinal arteries
    • these arteries are from branches off the aorta
    • the posterior arteries have better continuity of blood supply than anterior


What are the physiological differences of a Sub-Arachnoid Block (SAB) and an epidural?

  • SAB- LA is injected into CSF to directly bathe the nerve root; rapid onset of block
    • autonomic blockade 2-6 levels above sensory blockade; motor blockade 2 below sensory
  • Epidural anesthesia- LA is injected into epidural or caudal space and diffuses through the dural cuff before bathing the nerve root; slower onset
    • approx 5 minute onset
    • autonomic blockade same level as sensory blockade; motor blockade 2-4 levels below sensory blockade
    • not as dense of a block
    • good option if pt will not tolerate the large drop in autonomic response of the SAB


What is the goal of a neural blockade?

  • Goal: blockade of nociceptive impulses
    • it will block all impulses regardless of fiber type
      • autonomic
      • sensory
      • proprioception
      • motor


Which nerve type are highly sensitive to blockade?


resistant to LA blockade?

  • Autonomic nerves are highly sensitive with rapid onset
  • Sensory nerves have intermediate sensitivity
  • Motor nerves are more resistant to LA and have slower onset


What are the advantages of neuraxial anesthesia?


  • decreased incidence of DVT, cardiac morbidity and death
  • decreased lower extremity vascular graft occlusion, due to vasodilation which increases tissue blood flow below level of blockade
  • decreased incidence of PNA
  • decreased stress response
  • avoids airway manipulation
  • decreased incidence of PONV
  • intra and postoperative pain relief


What are the disadvantages of neuraxial anesthesia?


  • hypotension
  • delayed case start
  • failure rate depends on experience
  • not a benign anesthetic


Things to consider when choosing a neuraxial technique: (7)

  • Anatomy
  • Age: younger ppl are easier because the spaces between vertebrae get smaller with age
  • pregnancy
  • pathophysiology/comorbidities
  • sensory level required vs adverse physiological effects
  • length of procedure: a spinal gives about 2 hours, can be prolonged a bit with vasoconstrictor and decadron added
  • post-op analgesia needs


What are contraindications for neuraxial anesthesia?


  • patient refusal (the only absolute contraindication)
  • infection at injection site
  • bacteremia
  • septicemia
  • increased ICP
  • clotting defects/anticoagulant therapy
  • severe hemorrhage or hypovolemia
  • CNS disease/meningitis
  • hysteria/inability to remain still for block placement
  • valvular lesions with fixed stroke volume
    • severe AS/MS and hypertrophic cardiomyopathy
  • difficult airway
  • full stomach
  • peripheral neuropathies