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Anesthesia for Orthopedic Surgery and Evoked Potentials Monitoring

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Anesthesia for Orthopedic Surgery and Evoked Potentials Monitoring Jampierre Mato CRNA,MSN,ARNP Clinical Adjunct Professor Anesthesiology Nursing Program – PowerPoint PPT presentation

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Title: Anesthesia for Orthopedic Surgery and Evoked Potentials Monitoring


1
Anesthesia for Orthopedic Surgery and Evoked
Potentials Monitoring
  • Jampierre Mato CRNA,MSN,ARNP
  • Clinical Adjunct Professor
  • Anesthesiology Nursing Program
  • Florida International University

2
The Specialty
  • Orthopedics has grown immensely within the past 2
    to 3 decades, mainly due to the development of
    arthroscopic equipment and hardware to replace
    joints
  • Total joint replacement (shoulder, elbow, wrist,
    hip, knee, and ankle)-may offer a vast
    improvement in quality of life
  • Inter-vertebral disc replacements are now being
    offered
  • Benefits of arthroscopy
  • Much less invasive than open techniques
  • Allows direct visualization and manipulation with
    specialized equipment
  • Reduced discomfort and length of stay (many
    procedures done as outpatient)

3
Tourniquets
  • Pneumatic Tourniquets
  • Provide virtually bloodless field
  • Cuff should overlap only 3 to 6 inches
  • Area underneath must be padded and wrinkle-free
  • Overlap of cuff should be opposite of
    neurovascular bundle (e.g. on the humerus,
    overlap is on the lateral aspect-opposite the
    brachial plexus)
  • Inflation pressure usually 100mmHg greater than
    systolic blood pressure

4
Tourniquets
  • Must exsanguinate extremity prior to inflation
    (elevate or use Esmarch bandage)
  • Elevation is preferred in infected extremities
  • Inflation pressures
  • Should not exceed 300mmHg in upper extremities
  • Should not exceed 500 mmHg in lower extremities

5
Tourniquet Pain
  • Compression of intra-neural blood vessels
  • Causes secondary nerve ischemia
  • Leads to stimulation of pain pathways
  • Onset 45-60 minutes after inflation
  • Similar to thrombotic vessel occlusion
  • Activation of C fibers burning and aching
  • Activation of A delta fibers pins and needles
  • Difficult to treat, once it begins analgesics
    and anesthetics have little effect, may need to
    treat sympathetic activation (tachycardia and
    hypertension)-What is the only true treatment?

6
Effects of Tourniquets
7
Tourniquet Safety
  • -Always place cuff where nerves are best
    protected in the musculature
  • -Check proper function of machine
  • -Never inflate for longer than 2 hours 10 to 15
    minute reperfusion interval required prior to
    re-inflation
  • -Minimally effective pressure to occlude blood
    flow
  • -Put display where you can see it
  • Report 60 minutes, then 15 min increments after
    that to the surgeon and be sure to chart that you
    did so
  • Always chart times on your record

8
Hip Fractures
9
Hip Surgery
  • -ORIF Open Reduction with Internal fixation
  • Done for fractures (usually frail/elderly)
  • Requires use of special fracture table (legs
    split with traction applied)
  • Frequent concomitant diseases (dementia,
    Parkinsons, CAD, diabetes, etc.)
  • Frequently dehydrated
  • Occult blood loss can be significant
  • Intracapsular
  • Subcapital, transcervical less blood loss
  • Extracapsular
  • Femoral neck, intertrochanteric, subtrochanteric
    expect higher blood loss
  • -Bipolar hip replacement (not a total hip
    arthroplasty)
  • -done when fracture is not amenable to permanent
    fixation
  • - femoral head and partial femoral neck are
    resected and replaced with a prosthesis
  • -acetabular component is not fixed to the
    acetabulum
  • -procedure usually takes less than an hour

10
Bipolar Hip Prosthesis
  • Cup is not attached to acetabulum
  • Utilized when patient will be non-ambulatory or
    will limit weight-bearing activities on hip for
    the rest of his life

11
Fat Embolism
  • High correlation with long bone, hip, and pelvic
    fractures
  • Occurs, to some degree, in all hip fracture
    patients
  • Patients typically have low oxygen saturation and
    low-grade fever
  • Fat Embolism Syndrome
  • Presents within 72 hours of injury
  • 3 hallmark signs confusion, dyspnea, petechiae
  • Fat globules released into the blood through
    tears in medullary vessels
  • Theory that chylomicrons result from aggregation
    of circulating fatty acids
  • Thrombocytopenia and prolonged clotting times may
    occur

12
Fat Embolism Under GA
  • Diagnosing fat embolism syndrome under general
    Anesthesia
  • Decline in end tidal CO2
  • Decline in arterial oxygen saturation
  • Rise in pulmonary artery pressures
  • Ischemic-appearing ST segment changes
  • Right sided heart strain
  • If severe, may lead to RVOT obstruction with
    resultant CV failure/arrest

13
Anesthetic Choice in Hip Fracture
  • General or Regional?
  • Extensively evaluated
  • Regional has lower mortality in the first 2
    months post surgery
  • No significant difference in mortality after 2
    months
  • General is associated with more thrombo-embolic
    events than regional
  • Morbidity post-general is higher immediately post
    operatively

14
Total Hip Arthroplasty
  • -Usually done in lateral decubitis position
  • Higher degree of visibility and range of motion
  • -Most common indication is Osteoarthritis (OA)
    AKA Degenerative Joint Disease (DJD)
  • -Surgical Concerns (large incision, muscle
    trauma)
  • Acetabulum and femoral head/neck are very
    vascular
  • Resection of femoral head and neck
  • Reaming of femoral shaft to accept stem
  • Reaming of acetabulum to accept cup
  • Three life threatening complications
  • Bone cement implantation syndrome (cement rarely
    utilized in primary arthroplasty)
  • Peri-operative hemorrhage
  • Thrombo-embolism

15
Cement Implantation Syndrome
  • Methylmethacrylate (MMA)
  • Mixing Powder and liquid causes exothermic
    reaction
  • Reaction causes expansion of cement and forces
    fat, blood, and air into the femoral venous
    channels
  • Residual monomer (liquid) is a potent systemic
    vasodilator and pulmonary vasoconstrictor
  • Release of tissue thromboplastin may trigger
    thrombo-embolism and cause hemodynamic
    instability

16
Total Hip Replacement
Minimally invasive/muscle sparing techniques are
in widespread use
17
Closed Hip Reduction
  • May be necessary if prosthesis dislocates
  • Often done with heavy MAC or IV general with
    short-acting muscle relaxant, unless
    contraindicated
  • Extremes of flexion and internal rotation can
    dislocate a new prosthesis- abduction pillow is
    placed immediately post-operatively to avoid
    dislocation
  • Repeated dislocation of a hip prosthesis may
    require revision of the prosthesis-this is
    usually a failure of either surgical technique or
    the implant itself

18
Lateral Decubitus Position
  • Used in thoracic, renal, and orthopedic
    procedures
  • Presents unique challenges to the anesthetist
  • Importance of body alignment (cervical/thoracic/lu
    mbar)
  • Use of bean bag, axillary roll, pillows, sandbag
  • Cardiovascular Considerations
  • Respiratory Considerations
  • FRC decreased
  • Ventilation/Perfusion mismatch
  • Atelectasis
  • Use of PEEP (may worsen mismatch)

19
Lateral Decubitus
20
Total Knee Arthroplasty
  • Usually done for osteoarthritis or late-stage
    rheumatoid arthritis
  • Supine position
  • Regional vs. general anesthesia
  • Cement implantation syndrome (when is this a
    concern?)
  • Tourniquet concerns (ensure it is working)
  • Autologous blood donation
  • Bleeding is usually an issue post-op (once
    tourniquet is down)

21
Revision Joint Replacements
  • Previous joint replacements may need to be
    revised
  • Lifespan of current implants is postulated to be
    10 to 15 years (may be shorter or longer,
    depending on recipient use)
  • Revision procedures tend to be lengthy and bloody
  • Intra-operative cell salvage is usually
    recommended
  • Infected joints need to be removed, with
    placement of antibiotic spacers until infection
    resolves-dont use cell savage in suspected
    infection cases

22
Spinal Surgery
  • -Done for a variety of diagnoses
  • -herniated discs
  • -spondylolisthesis/spondylosis
  • -spinal canal stenosis
  • -radiculopathy
  • -myelopathy
  • -osteophyte compression
  • -scoliosis
  • -kyphosis
  • -post-traumatic stabilization

23
Spondylolisthesis
24
Common Diagnoses in Spine Surgery
  • Intervertebral disc herniation
  • Herniated disc may impinge on nerve roots and the
    cord itself
  • Spinal stenosis
  • Refers to narrowing of the spinal canal, for
    whatever reason (herniation, degenerative disc
    disease, spondylolisthesis, osteophyte formation,
    etc.)

25
Minimally Invasive Spine Surgery
  • Traditional spinal surgery (laminectomy, fusion,
    etc.)
  • Large incisions
  • Large amount of blood loss and prolonged wound
    healing
  • Great post-operative discomfort
  • Lengthy hospital stays
  • Commonly required anterior approach for the
    lumbar spine (laparotomy incision)
  • Mini-invasive spine surgery
  • Small incisions
  • Decreased blood less and faster wound healing
  • Decreased post-operative discomfort
  • Shorter hospital stay
  • Allows more complex procedures to be performed at
    once
  • Often allows access to lumbar spine that formerly
    required laparotomy

26
Mini-Invasive Spine Procedures
  • Lateral interbody fusion (LIF)
  • Allows complete lumbar discectomy and cage
    placement/fusion through a small flank incision
  • Trans-foraminal lumbar interbody fusion (TLIF)
    allows near-total discectomy with cage
    placement/fusion through a para-spinous incision
  • Axia Lumbar Interbody fusion (AxLIF)
  • Allows fusion of the L5-S1 interspace through a
    sub-sacral incision
  • Micro-discectomy allows removal of a herniated
    portion of disc through an access port (may
    utilize microscope)
  • Laminectomy allows for total or hemi-laminectomy
    through a port

27
Microdiscectomy
28
Positioning on Andrews Frame
29
Positioning on Wilson Frame
30
Scoliosis
  • Lateral curvature of the spine
  • 75-80 of cases are idiopathic
  • Untreated, can lead to complex deformity
  • SSEP and MEP monitoring
  • Preoperative evaluation (cor pulmonale, pulmonary
    physiology changes)
  • PFTs, ABGs, EKG
  • Increased incidence of MH if caused by muscular
    dystrophy (in pediatric patients)

31
Scoliosis
32
Scoliosis Surgery
  • Gold standard is multi-level fusion with
    instrumentation/rods
  • Potential for large blood loss (weighing of
    laps/sponges and tight I O recording)- cell
    salvage usually utilized
  • Wake up test is uncommon, due to modern
    monitoring of evoked potentials
  • Severe respiratory disease may exist
    preoperatively, may be left intubated
    postoperatively
  • Major concerns with positioning (may have severe
    deformities)
  • Posterior, anterior, or thoraco-abdominal
    approaches may be necessary
  • May require double lumen tube if utilizing
    anterior thoracic approach

33
Monitoring of Evoked Potentials
  • Types MEP, SSEP, EMG, VEP, BAEP
  • Indications
  • Evaluation of pathology
  • Monitoring during any procedure which may
    compromise a nerve pathway

34
Cuneatus and Gracilis Tracts
  • Part of the dorsal-lemniscal sensory system
  • Responsible for touch, pressure, and vibration
    sensation
  • Located in the dorsal cord
  • Integrity of dorsal tract is assessed by SSEP
    monitoring (somato-sensory evoked potentials)
  • Sensations ascend on the ipsilateral side of the
    cord and cross into the contralateral side at the
    thalamus (considered a direct pathway to the
    cerebral cortex)
  • Procedures that may require SSEP monitoring
    cerebral aneurysm clipping, spine surgery, CEA
    (questionable applicability), complex
    thoraco-abdominal aneurysm repairs (MEPs are
    more useful since ischemia usually occurs in the
    ventral horn)

35
Reticular Activating System
  • Considered a secondary way by which sensory
    information arrives at the cerebral cortex
  • Deactivated during sleep
  • General anesthetics produce their effects through
    action on the RAS

36
Cortical Pathways
  • SSEPs are recorded from the scalp
  • A peripheral nerve (ulnar/median or tibial) is
    stimulated, bilaterally, to procedure a potential
    that is recorded in the scalp
  • Stimulating electrodes are peripheral and
    detecting electrodes are central (the scalp)

37
Evoked Potential Waveforms
  • Amplitude height of the waveform
  • Latency can be thought of as the frequency
  • Decreased amplitude and/or increased latency
    indicate a compromise in nerve potential
    transmission
  • Factors that affect waveforms temperature, PaO2,
    PaCO2, systemic blook pressure
  • VEPs are most affected by our anesthetics,
    SSEPs are moderately affected, and BAEPs are
    marginally affected

38
Anesthesia During Evoked Potentials Monitoring
  • What can we do?
  • Maintain normothermia
  • Maintain blood pressure within 20 of baseline
    (critical in long-standing hypertension and/or
    small vessel disease)-consider invasive
    monitoring in select patients
  • Use anesthetics with minimal effects on waveform
    character (TIVA)
  • Maintain oxygenation (may be difficult during
    one-long ventilation)
  • Maintain normocapnea

39
The Ultimate Test of Nerve Pathway Integrity?
  • Wake up and move everything!

40
Foot and Ankle Surgery
  • Ankle fracture
  • Plate and screws
  • Bunionectomy
  • Hammer toe correction
  • Plantar fasciotomy
  • Achilles tendon repair

41
Ankle Block
  • Frequently used in podiatric cases
  • Insert needle lateral to the posterior tibial
    artery at the superior aspect of the medial
    malleolus (posterior tibial nerve)
  • Inject 5ml of local and 2ml as you withdraw the
    needle
  • Insert needle at the lateral border of the
    achilles tendon with the line between the
    malleoli, advance toward the lateral condyle,
    inject 5ml of local (sural nerve)

42
Posterior Tibial Nerve
43
Sural Nerve
44
Ankle Block Technique
  • Draw a line between the superior edge of the
    medial malleolus across the anterior portion of
    the ankle
  • Flex the foot and place the needle between the
    tendons medial to the big toe (deep peroneal
    nerve), inject 5ml of local
  • With the remaining local, fan inject across the
    same plane across the ankle (saphenous nerve)

45
Superficial Peroneal Nerve
46
Needle Directions in Ankle Block
47
Upper Extremity Procedures
  • -Usually amenable to brachial plexus block
    (interscalene, supraclavicular, axillary)
  • Shoulder arthroplasty or arthroscopy
  • Requires beach chair/sitting position
  • Venous air embolism precautions
  • Airway concerns
  • Cardiovascular considerations?
  • Elbow arthroplasty or arthroscopy
  • Prone position
  • Turn head away from field
  • Turn table 90 degrees

48
Shoulder Arthroplasty
Painful!!
49
Hand Surgery
  • Hand surgery
  • General vs. regional
  • Bier block
  • Axillary block
  • Wrist block
  • Tourniquet concerns
  • Long cases
  • Often awake, often uncomfortable (consider
    general)
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