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Epidural Review

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Epidural Review Kate Hagan, M.D. 10/14/2008 Anatomy At each vertebral level, paired spinal nerves exit the central nervous system The 1st cervical vertebra is the ... – PowerPoint PPT presentation

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Title: Epidural Review


1
Epidural Review
  • Kate Hagan, M.D.
  • 10/14/2008

2
Anatomy
  • At each vertebral level, paired spinal nerves
    exit the central nervous system
  • The 1st cervical vertebra is the atlas
  • The 2nd cervical vertebra is the axis
  • All 12 thoracic vertebrae articulate with their
    corresponding rib

3
  • The spinal cord sits in the hollow ring bordered
  • - anteriorly by the vertebral body
  • - laterally by the pedicles and transverse
    processes
  • - posteriorly by the lamina and transverse
    processes

4
  • 3 layers of meninges the pia, arachnoid, and dura
  • CSF is found between the pia and arachnoid
    membranes
  • Spinal cord goes to L1 in adults and L3 in
    children
  • At the cervical level nerves arise above their
    respective vertebrae, but starting at T1 they
    exit below
  • Subdural space extends to S2 in adults and S3 in
    children

5
  • Blood supply to the spinal cord and nerve roots
    is derived from a single anterior spinal artery
    and paired posterior spinal arteries
  • Anterior spinal artery is formed from the
    vertebral artery, supplying the anterior 2/3 of
    the spinal cored
  • Posterior spinal arteries are derived from the
    posterior inferior cerebellar arteries and
    provide for the posterior 1/3
  • The artery of Adamkiewicz arises from the aorta
    typically on the left hand side and provides the
    major blood supply to the anterior, lower 2/3 of
    the spinal cord

6
Mechanism of Action
  • Principle site of action is the nerve root
  • Smaller myelinated fibers are blocked more easily
    than larger unmyelinated ones
  • Sympathetic blockade may be 2 segments higher
    than the sensory block, which is usually 2
    segments higher than the motor block

7
  • Sympathectomy leads to variable decreases in BP,
    accompanied by a decrease in heart rate and
    cardiac contractility
  • Vasomotor tone is determined by sympathetic
    fibers arising T5-T11, when these are blocked
    vasodilation of vessels occurs in conjunction
    with blood pooling
  • HR decreases when cardioaccelerator fibers
    (T1-T4) are blocked

8
  • Treatment
  • - volume load with 10-20 cc/kg of IVF in healthy
    patients prior to placing epidural
  • - left uterine displacement of pregnant patients
    minimizes physical obstruction of venous return
  • - autotransfuse with head down position
  • - treat bradycardia with atropine
  • - treat hypotension with fluid and pressors

9
Contraindications
  • Patient refusal
  • Bleeding diathesis
  • Severe hypovolemia
  • Elevated ICP
  • Infection at site of injection
  • Severe stenotic valvular heart disease
  • Ventricular outflow obstruction

10
Neuroaxial Blockade and the Anticoagulated Patient
  • Coumadin it must be stopped prior to placement
    and normal coagulation studies confirmed
    removing a catheter from a patient on low dose
    therapy (5mg/day) is reported to be safe
  • Antiplatelet drugs ASA and NSAIDS should be safe
    in normal patients with normal coagulation
    profiles more potent agents should be stopped
    and a waiting period observed i.e. Ticlid 14d,
    Plavix 7d, Rheopro 48hrs, Integrilin 8h

11
  • Standard (Unfractionated) Heparin
    - minidose SQ prophylaxis is not a
    contraindication
  • - blocks may be performed up to 1 hour prior
    to heparin administration
  • - removal of catheters should occur 1hr prior
    to or 4hr after heparin dosing
  • - Avoid in patients on therapeutic doses of
    heparin or in those with increased PTT

12
  • LMWH wait 12-24hrs prior to performing
    neuroaxial block
  • - if bloody needle or catheter placement occurs,
    LMWH should be delayed until 24h postoperatively
    to decrease risk of spinal hematoma
  • - remove catheters 2hrs prior to first LMWH
    dose
  • - if the catheter is already present, wait
    until 10 hours after last dose to pull it, and
    then wait another 2 hours before restarting it
  • Fibrinolytic or thrombolytic therapy avoid
    neuroaxial blockade

13
Approach for Epidural
  • Midline remembering that spinous processes
    course downward from the spine, the needle is
    directed slightly cephalad you pass through the
    supraspinous and interspinous ligaments, then the
    ligamentum flavum
  • Paramedian raise skin wheal 2 cm lateral to the
    inferior aspect of the superior spinous process
    of the desired level, advance the needle at a
    10-25 degree angle towards midline you directly
    enter the ligamentum flavum

14
Techniques for Recognizing Entrance to Epidural
Space
  • Loss of Resistance glass syringe filled with 2cc
    of fluid or air and attached to the epidural
    needle is advanced through the ligaments while
    applying continuous or rapidly repeating attempts
    at injection as you slowly advance the needle
    millimeter by millimeter. As the tip of the
    needle enters the epidural space, there is a
    sudden loss of resistance and injection becomes
    easy

15
  • Hanging drop technique once the interspinous
    ligament has been entered and the stylet removed,
    the hub of the needle is filled with solution so
    that a drop hangs from its outside opening. The
    needle is then slowly advanced deeper. As the
    tip of the needle enters the epidural space it
    creates negative pressure and the drop of fluid
    is sucked into the needle

16
Complications of Neuroaxial Blocks
  • Adverse or Exaggerated Physiological Responses
  • High levels of neural blockade causing
    hypotension, bradycardia, and respiratory
    insufficiency even unconsciousness may also be
    caused by inadvertent intrathecal injection
  • Cardiac arrest has been seen, especially in
    patients with high baseline vagal tone
  • Urinary Retention

17
  • Complications Associated with Needle or Catheter
    Insertion
  • Intravascular Injection affecting the CNS
    (seizures and unconsciousness) and cardiovascular
    system (hypotension, arrhythmia, and
    cardiovascular collapse)
  • Tx ACLS lipid emulsion therapy
  • LA toxicity occurs secondary to binding to Na
    channels
  • Lipid emulsion acts as a sink to effectively
    remove the LA from the circulation
  • Dosage 20 intralipid 1.5cc/kg as initial bolus
    followed by0.25 cc/kg/min for 30-60 min. You
    may repeat initial bolus 1-2 times if asystole
    persists

18
  • Total spinal consider subarachnoid lavage
    repeated withdrawal of 5cc of CSF, replacing it
    with preservative free NS
  • Subdural Injection clinical presentation similar
    to high spinal, but onset is delayed 15-30
    minutes
  • Backache

19
  • Postdural Puncture Headache
  • typically bilateral, frontal or retroorbital, and
    occipital and extends into the neck
  • Pain is aggravated by sitting or standing and
    relieved or decreased by lying down flat
  • Onset is 12-72 hrs following procedure
  • Pain may last weeks
  • Cx loss of CSF faster than it can be replaced
    leads to traction on structures supporting the
    brain.
  • Pts may have diplopia secondary to traction on
    the sixth cranial nerve

20
  • risk factors larger needles, cutting point
    needles, young age, female sex, pregnancy
  • Tx recumbent position, analgesics, iv or po
    fluid, and caffeine
  • Epidural Blood patch inject 15-20cc autologous
    blood into epidural space at, or one interspace
    below the level of the dura puncture 90 respond
    to 1st patch and 90 or nonresponders respond to
    2nd patch

21
  • Neurological Injury injury to nerve roots or
    spinal cord
  • Spinal or Epidural Hematoma
  • clinically significant cases or usually seen in
    the presence of abnormal coagulation or bleeding
    disorder
  • onset of symptoms is usually faster than that
    seen with an abcess
  • sx include sharp back pain and leg pain with a
    progression to numbness and motor weakness and/or
    sphincter dysfunction
  • Obtain MRI or CT
  • Surgical decompression must occur within 8-12
    hours for good neurological recovery

22
  • Meningitis and arachnoiditis
  • Epidural abcess
  • Sheering of an epidural catheter occurs when
    catheter is withdrawn through the needle
  • if catheter must be withdrawn before needle is
    pulled out, then they must be withdrawn together
  • If catheter breaks deep within tissues, then
    leave it and observe pt
  • If it breaks superficially, causing concern as a
    nidus for infection, then surgical removal is
    warranted

23
  • Transient Neurological Symptoms back pain
    radiating to the legs without sensory or motor
    deficits, occurring after resolution of spinal
    block and resolving spontaneously within several
    days
  • Most common with Lidocaine
  • Highest among outpatients, after surgery in the
    lithotomy position

24
  • Lidocaine Neurotoxicity
  • Cauda Equina Syndrome was associated with the use
    of continuous spinal catheters and 5 Lidocaine
  • It is characterized by bowel and bladder
    dysfunction together with evidence of multiple
    nerve root injury, paresis of the legs, patchy
    sensory deficits
  • Neurotoxicity of LAs
  • lidocaine tetracaine gt bupivacaine gt
    ropivacaine

25
Questions
  • Which of the following is the earliest sign of
    lidocaine toxicity?
  • 1) shivering
  • 2) nystagmus
  • 3) lightheadedness and dizziness
  • 4) tonic-clonic seizures
  • 5) nausea and vomiting

26
  • The snap felt just before entering the epidural
    space represents passage through which ligament?
  • 1) anterior longitudinal ligament
  • 2) posterior longitudinal ligament
  • 3) ligamentum flavum
  • 4) supraspinous ligament
  • 5) interspinous ligament

27
  • The correct arrangement of local anesthetics in
    order of their ability to produce cardiotoxicity
    from most to least is
  • 1) bupivacaine, lidocaine, ropivacaine
  • 2) bupivacaine, ropivacaine, lidocaine
  • 3) lidocaine, bupivacaine, ropivacaine
  • 4) ropivacaine, bupivacaine, lidocaine
  • 5) lidocaine, ropivacaine, bupivacaine

28
  • A 21-yr-old patient reports tingling in her thumb
    during c-section under epidural anesthesia. To
    which dermatomal level would this correspond?
  • 1) C4
  • 2) C5
  • 3) C6
  • 4) C7
  • 5) C8

29
  • Each of the following is associated with
    increased incidence of headache after spinal
    anesthesia except
  • 1) young age
  • 2) female gender
  • 3) early ambulation
  • 4) pregnancy
  • 5) large needle size

30
  • Morgan, G. Edward et al., Clinical
    Anesthesiology, McGraw-Hill New York, 2006.
  • Hall, Brian A., Anesthesia A Comprehensive
    Review, Mosby Pennsylvania, 2003.
  • Connelly, Neil Roy, Review of Clinical
    Anesthesia, Lippincott Williams Wilkins
    Philadelphia, 2006.
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