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Anesthetic Methods in the Management of Carotid Endarterectomies

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Title: Anesthetic Methods in the Management of Carotid Endarterectomies


1
Anesthetic Methods in the Management of Carotid
Endarterectomies
  • Daniel Park MD
  • CA-2
  • Boston Medical Center

2
Positioning
  • Placed in supine position
  • No head elevation
  • Head tilted away from surgical site
  • Shoulder roll may be helpful for exaggerated neck
    extension

3
Surgical Technique
  • Incision from the mastoid process extending down
    the anteromedial border of the sternocleidomastoid
    muscle
  • Ends 1-2 fingerbreaths from the sternal notch

4
Surgical Technique
  • Carotid sheath dissected to expose the carotid
    artery, internal jugular vein, vagus nerve, and
    deep cervical lymphatic chain
  • Prior to shunt placement or clamping of artery,
    heparin to be administered
  • Incision made from proximal common carotid artery
    into internal carotid artery
  • Vessel cleaned of atheromatous plaque
  • Closure either primary with vein or prosthetic
    patch

Townsend Sabiston Textbook of Surgery, 17th ed.,
2004
5
Pathophysiology
  • Type I and Type II baroreceptors present
  • Opened artery exposes baroreceptors to
    atmospheric pressure
  • Causes firing down the myelinated A-type fibers
    and C-type fibers of the glossopharyngeal nerve
    to the nucleus tractus solitarius
  • Triggers central systemic pressure response
  • Carotid chemoresponse
  • Rapid drop in oxygen tension
  • Further cause increasing signals down afferent
    pathway
  • Overall, causes onset of tachycardia and severe
    hypertension and thus increases in afterload and
    myocardial oxygen demand

6
Complications of CEA
  • Stroke
  • Neck hematoma
  • Cardiac complications (MI)
  • Nerve injury
  • Glossopharyngeal nerve
  • Phrenic nerve injury
  • Recurrent laryngeal or vagus nerve injury

7
General Anesthesia versus Regional/Local
Anesthesia
  • Remains a controversial topic
  • Cochrane review 2004
  • 7 randomized trials, 41 non-randomized trials
  • Insufficient evidence to make a clear decision
    between GA and regional

8
General Anesthesia
  • Tracheal intubation versus LMA
  • NMBA often used for immobilizing patient
  • TIVA compared to inhaled anesthetics with no
    difference in hemodynamic events or postoperative
    pain

9
General Anesthesia
  • GA does not prevent hemodynamic response of
    manipulation of the carotid sinus (severe vagal
    response)
  • Advisable to inject 1-2 ml of 1 lidocaine in the
    tissue between the internal and external carotid
    arteries before surgical manipulation
  • Severe hemodynamic response can lead to spasming
    of the coronary artery

10
General Anesthesia
  • Due to comorbidities (ie CAD, MI) important to
    avoid large BP swings
  • Especially upon intubation and emergence
  • Study done comparing hypnotic technique (high
    dose propofol with remifentanil versus opioid
    technique (low dose propofol with remifentanil)
  • Less BP swings and tachycardia with opioid group

11
General Anesthesia
  • Maintenance of normocarbia
  • Hypercarbia leads to cerebral vasodilation
  • Steal syndrome could occur
  • Hypocarbia leads to vasoconstriction
  • Ischemia to compromised area of brain
  • Quick emergence
  • Important to assess neurological function quickly

12
Regional Anesthesia
  • Deep Cervical Plexus Block
  • Three separate injections
  • Line drawn connecting the tip of the mastoid
    proxess and the Chassaignac tubercle (ie
    transverse process of C6)
  • Another line drawn 1 cm posterior to the first
    line C2 transverse process lies 1 to 2 cm caudad
    to the mastoid process
  • 22 G needle x3 advanced perpendicular to the skin
    and slightly caudad until contacting the
    transverse process (depth about 1.5 to 3 cm)
  • If paresthesias elicited, inject 3 to 4 ml of
    solution, if not elicited, walk along transverse
    process in a caudad or cephalad direction
  • OR
  • Inject in single injection at C4 transverse
    process and rely on cephalad spread of the
    anesthetic to C2 and C3 nerves

13
Regional Anesthesia
  • Deep Cervical Plexus Block
  • Complications
  • Intravascular injection
  • Intrathecal injection
  • Paralysis of the ipsilateral diaphragm
  • Laryngeal block causing hoarseness, coughing and
    dysphagia

14
Regional Anesthesia
  • Superficial Cervical Plexus block
  • Anesthetize C2 to C4 branches
  • Midpoint of the posterior border of the
    sternocleidomastoid muscle
  • Injection of solution along the posterior border
    and medial surface of the muscle
  • May block accessory nerve causing trapezius
    muscle paralysis

15
Regional Anesthesia
  • Bupivicaine
  • Longest duration of block
  • Greatest cardiac toxicity
  • Levobupivicaine
  • Similar duration
  • Less potential toxicity
  • Expensive
  • Ropivicaine
  • Similar quality of block
  • Shorter duration of postoperative pain relief
  • Sardanelli et al demostrated 8 ml dose of 0.75
    was adequate for a good quality block

16
Cerebral Monitoring
  • Why is it important?
  • Once compromise is discovered (or predicted)
    carotid shunt can improve cerebral oxygen
    delivery
  • Carotid shunt can be placed in both external or
    internal carotid artery however internal carotid
    is much more effective

17
Cerebral Monitoring
  • Why not shunt everyone?
  • Potential displacement of atheromatous debris,
    introduction of air embolism or thrombosis of
    shunt
  • Increases surgical time
  • Presence of shunt makes surgical field less than
    optimal

18
Cerebral Monitoring
  • Awake patient the gold standard
  • Assessment of grip strength of the contralateral
    hand
  • Responsive to verbal commands
  • Same anesthesiologist for assessment in
    comparison of before and after crossclamping

19
Cerebral Monitoring
  • Backpressure measurement
  • Gives an estimate of reasonable collateral
    circulation above the crossclamp
  • Carotid stump pressure to predict need for
    temporary shunt placement
  • Traditionally the cutoff has been 50 mmHg

20
Cerebral Monitoring
  • EEG current best measurement for GA patients
  • Gives ability to assess both focal and global
    changes
  • General anesthetic may change EEG patterns
  • Difficult to interpret, needing special expertise
  • BIS has been used to identify severe ischemia
  • Unable to differentiate global versus focal
    changes

21
Cerebral Monitoring
  • SSEP usefulness inconclusive
  • Retrospective review concluded could be useful
  • Prospective study of 50 patients concluded that
    although there is a 2 false negative rate, in
    general there is a limited value of SSEP in the
    detection of cerebral ischemia

22
Cerebral Monitoring
  • TCD ultrasonography noninvasive monitoring of the
    velocity of blood flow in the middle cerebral
    artery
  • Belardi suggests that U/S may not be effective in
    the prediction for shunt placement
  • Could be useful in the detection of cerebral
    emboli

23
Cerebral Monitoring
  • Carotid angiography may be a useful predictor of
    assessment of collateral circulation
  • Shunt more common when failure of collateral flow
    from contralateral hemisphere or when the
    contralateral internal collateral flow was
    occluded
  • Reported sensitivity 91 and specificity 35
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