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
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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

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Complications of CEA

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

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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

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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

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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

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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

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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

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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

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Regional Anesthesia

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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