MetroHealthAnesthesia Case Western Reserve University
MetroHealth Medical Center Department of Anesthesiology

Anesthetic Considerations for Thoracic Aortic Surgery

Charles E. Smith, M.D. and Antonio Cooper, M.D., December 2002

Note: All Attendings and Senior Residents Taking Call in the Main Operating Room Should Become Familiar with These Anesthetic Considerations, Especially Drugs PSR.

Outline: Historical
1903 Matas: internal shunt for aneurysm
1948 End to end anastomosis of coarctation
1952 DeBakey and Cooley: thoracic homograft
1957 Aortic arch replacement

Classification of Thoracic Aorta Disease
  1. Dissection: intimal tear, hematoma in media
  2. Aneurysm: dilation, atheromatous
  3. Tear: major trauma
  4. Coarctation: congenital narrowing

1. Thoracic Aortic Dissection

  • Sudden tranverse tear of intima
  • Blood forced under pressure down aorta
  • Media destroyed
  • Intima stripped from adventitia
  • Type A: ascending aorta
  • Type B: distal to left subclavian
Diagnosis
  • Pain
  • Pulse deficit
  • Aortic insufficiency- new murmur
  • Neurologic deficit
  • Widened mediastinum, Lt pleural effusion
  • Aortography, CT, TEE
Management
  • Stop progression of dissection
  • Type A: urgent surgery
  • Type B: medical- beta blockers + SNP; surgery if progression or Marfan’s
Surgical Management of Type A Dissections
  • Cardiopulmonary bypass: various cannulation sites
  • Drugs PSR:
    • Full heparinization, 3 mg/kg
    • Amicar per protocol: mix 5 vials (20 ml, 5 G) in 150 ml bag- final volume 250 ml, final conc = 100 mg/ml. Load ½ ml/kg over 30 min; infusion: ¼ ml/kg/hr until bag is finished
    • Add 1 bottle albumin, 25% to bypass circuit
    • Protamine after CPB, e.g., 4 mg/kg over 15 minutes
  • Interposition of tubular graft
  • Re-establish circulation through true lumen
  • Assumes aortic valve, coronary ostia, arch not involved
  • Hypothermic circulatory arrest (circ arrest): 19-21 C, slow cooling
  • Operative mortality: 4%
  • Long-term survival: 70% at 6 yrs
  • If arch involved, increased mortality
Surgical Management of Type B Dissection
  • Only for progression or if Marfan’s
  • High mortality 21-45% due to bleeding, low CO
  • Medical rx preferred (20% mortality)
Anesthetic Management: Type A Dissection
  • Stop progression of dissection: initiate medical treatment of BP as soon as diagnosis is made. Control BP with SNP and beta- blockers. If dissection progresses, may develop aortic insufficiency, coronary ischemia, cerebral infacrtion, occlusion of limb circulation, cardiac tamponade
  • Standard anesthetic principles for cardiac surgery: can add lidocaine, 1.5 mg/kg, and esmolol, 1 mg/kg, to prevent tachycardia and hypertension during induction
  • Usual monitors for cardiac surgery and CPB
  • Left radial art line (inominate artery may be involved in the dissection)
  • Pack head in ice for circ arrest (cover BIS so it does not get wet)
  • Intraoperative TEE: intimal tear, coronary ostia, AI

2. Thoracic Aortic Aneurysms

  • Fusiform or saccular dilatation of aorta
  • Etiology: Atherosclerosis, cystic medionecrosis, infectious
  • Location:
    1. Ascending: proximal to inominate artery
    2. Arch: between inominate and left subclavian
    3. Descending: distal to left subclavian
Diagnosis
  • Pain
  • Recurrent laryngeal (hoarseness)
  • Compression: dysphagia, hemoptysis, pneumonitis
  • CXR abnormalities
  • Echo, MR, CT, aortogram
Surgical Management of Ascending Aneurysm
  • Generally needed if > 5 cm
  • Operative mortality ~ 2%
  • Cardiopulmonary bypass: various cannulation sites
  • Bentall procedure: ascending aorta replacement with AVR and coronary implants
  • Drugs PSR:
    • Full heparinization, 3 mg/kg
    • Amicar per protocol: mix 5 vials (20 ml, 5 G) in 150 ml bag- final volume 250 ml, final conc = 100 mg/ml. Load ½ ml/kg over 30 min; infusion: ¼ ml/kg/hr until bag is finished
    • Add 1 bottle albumin, 25% to bypass circuit
    • Protamine after CPB, e.g., 4 mg/kg over 15 minutes
Anesthetic Management of Ascending Aneurysm
  • Standard anesthetic principles for cardiac surgery
  • Usual monitors for cardiac surgery and CPB
  • Left radial art line (inominate artery may be involved)
Surgical Management of Arch Aneurysm
  • Higher risk, technically difficult: 5 cm
  • Operative mortality ~ 13%
  • Replace arch between inominate and left subclavian
  • Cardiopulmonary bypass: various cannulation sites
  • Circ arrest 19-21 C
  • Retrograde cerebral perfusion (+ ): superior vena cava (SVC) to brain
Selective cerebral perfusion
  • Risk of air / atherosclerotic embolism
  • Drugs PSR:
    • Full heparinization, 3 mg/kg
    • Amicar per protocol: mix 5 vials (20 ml, 5 G) in 150 ml bag- final volume 250 ml, final conc = 100 mg/ml. Load ½ ml/kg over 30 min; infusion: ¼ ml/kg/hr until bag is finished
    • Add 1 bottle albumin, 25% to bypass circuit
    • Protamine after CPB, e.g., 4 mg/kg over 15 minutes
Anesthetic Management of Arch Aneurysm
  • Standard anesthetic principles for cardiac surgery
  • Usual monitors for cardiac surgery and CPB
  • Verify anatomy prior to insertion of art line (inominate +/or left subclavian artery may be involved)
  • Intraoperative TEE to assess embolic risk
  • Pack head in ice
  • Thiopental 3-10 mg/kg: possible benefit for cerebral protection
Surgical Management of Descending Aortic Aneurysm
  • Median survival w/o surgery: 3.3 yrs
  • Rupture more likely if > 5 cm
  • Operative mortality: 4% (range 3-28%)
  • Replace aorta from left subclavian artery to diaphragm
  • Partial bypass may be used – flow 1-2 L/min/m2, with heparin bonded tubing e.g., left atrium to femoral artery with heat exchanger but without oxygenator
  • Drugs PSR:
    • Heparin, 1 mg/kg before clamp
    • Mannitol 0.5 G/kg before clamp
    • NaHCO3 infusion 3 mEq/kg/hr during clamp (clamp time usually < 30 min)
    • CaCl2 1 g before clamp release
Anesthetic Management of Descending Aortic Aneurysm:
  • Standard anesthetic principles for cardiac surgery
  • Usual monitors for cardiac surgery
  • Right radial art line (left subclavian artery may be clamped)
  • One lung ventilation- see section on providing OLV Hemodynamic support and blood products
  • Level 1 warmer and Rapid infusion device (FMS 2000)
  • 1 large bore peripheral IV (16 or 14 G) + 1 large bore central line BP control:
    • No bypass (clamp and sew):- maintain SBP at baseline SBP + ½ of peak aortic cross clamp SBP
    • Bypass (distal perfusion)- maintain SBP at baseline SBP
    • Can reduce proximal hypertension during aortic clamp by increasing flow to the pump and decreasing flow to the heart
    • SNP should be used sparingly or not at all during aortic clamp because of risk of decreased spinal cord and renal perfusion.
    • Decrease concentration of volatile agent and turn off vasodilators before aortic unclamp
    • Volume repletion with colloid, crystalloid, blood products before and after aortic unclamp
    Reducing spinal cord ischemia:
    • Best method is short cross clamp time (< 30 min)
    • Maintain distal aortic perfusion pressure
    • Mild hypothermia
    • CSF drainage: controversial
    • Avoid hyperglycemia: insulin drip if glucose > 200
    • Pharmacologic agents: controversial

    3. Blunt Thoracic Aortic Injury

    • 80-90% die at scene
    • 90% survivors die within 10 weeks
    • Survivors have intact adventitia
    • Most common injury near ligamentum arteriosum, distal to left subclavian
    Etiology
    • Blunt trauma: e.g., MVAs, falls, crush
    • Pedestrian struck
    • Airplane crash
    Diagnosis
    • Widened mediastinum on CXR
    • Chest CT, TEE, Aortography
    Surgical Management of Blunt Aortic Injury
    • Depends on location of tear + extent of injury
    • Ascending- requires CPB + possible circ arrest (see aneurysm section)
    • Partial bypass may be used for descending tears – flow 1-2 L/min/m2, with heparin bonded tubing e.g., left atrium to femoral artery with heat exchanger but without oxygenator
    • Delayed v. emergent repair: delayed treatment if head injury, major burn, coagulopathy, pulmonary or myocardial contusion, preop hemodynamic instability
    • Risk of delayed repair = free rupture
    • Drugs PSR:
      • Heparin, 1 mg/kg before clamp
      • Mannitol 0.5 G/kg before clamp
      • NaHCO3 infusion 3 mEq/kg/hr during clamp (clamp time usually < 30 min)
      • CaCl2 1 g before clamp release
    Anesthetic Management of Blunt Aortic Injury
    • See section on Anesthetic Management of Descending Aortic Aneurysm:
    • High incidence extra-thoracic injuries: head, spine, extremity, rib fx, lung contusion, liver, spleen, etc.
    • Medical control of HR + BP during induction- esmolol, labetalol, metoprolol

    Standard Anesthetic Principles for Cardiac Surgery

    • Medical evaluation and treatment of co-existing disease: e.g., CAD, asthma, diabetes,
    • Continue antihypertensives, beta-blockers
    • Monitor and treat hypotension, hypertension, myocardial ischemia, hypovolemia, anemia, bradycardia, tachycardia, low cardiac output, hypoxia, acidosis, coagulopathy, low urinary output
    • Drugs: esmolol, NTG, nipride, milrinone, phenylephrine, dopamine, atropine, ephedrine
    • Midazolam premed, titrated opioid (e.g., fentanyl) for lines
    • Etomidate, opioid (e.g., fentanyl) induction + midazolam + muscle relaxant
    • Volatile agent, opioid, muscle relaxant maintenance + midazolam + propofol
    • Warm room after removal of aortic clamp if risk of hypothermia
    • Large bore IVs: e.g., 1 peripheral, 1 central
    • Rapid infusor devices: Belmont FMS, Level 1
    • Convective warmer + water mattress (turn off during cross clamp if perfusion to warmed area is absent)
    • Avoid high airway pressures: risk of barotrauma (Paw < 35 cm H2O)
    • Avoid prolonged muscle relaxation: facilitates SIMV + neurologic evaluation postop
    • Postop mechanical ventilation: all patients “eligible” for fast track extubation
    • Drugs PSR: antibiotics, heparin, mannitol, NaHCO3, albumin, amicar, CaCl2, protamine

    Usual Monitors for Cardiac Surgery

    • Standard ASA monitors
    • Arterial line
    • Urinary catheter + temp probe
    • CVP
    • Swan Ganz
    • BIS
    • LidCO + systolic pressure variation ?

    Providing One Lung Ventilation

    Left double lumen tube (DLT):
    • Better margin of safety than Rt
    • Easy to apply suction + CPAP to either lung
    • Easier to deflate lung (v. blocker)
    • Lower cuff seal volumes + pressure (v. blocker)
    • Fiberoptic bronchoscope to confirm position
    • Problems with left DLT
    • Cuff tears on maxillary teeth: put a “bend” in the tube or use Wuscope
    • Risk of change-over to single lumen at end of case (e.g., facial /pharyngeal/laryngeal edema, difficult intubation): can withdraw bronchial lumen to mid-tracheal position + clamp tracheal lumen; ventilate via bronchial lumen
    Univent
    • Easier to insert than DLT if difficult airway, C-spine precautions
    • Need higher cuff volumes (+ pressure) to seal bronchus
    • Often need suction via blocker to deflate lung
    • Insertion method: once tracheal intubation confirmed, rotate tube 90 degrees to desired atelectatic side
    • Advance blocker into desired mainstem with fiberoptic confirmation
    • Blocker can be retracted into pocket for postop mechanical ventilation
    • Alternate method for insertion if c spine cleared: turn head and tube to desired atelectatic side
    Arndt Endobronchial Blocker Set
    • Ideal if difficult intubation and pre-existing ETT, size > 8.0
    • Bronchial blocker can be guided into desired bronchus by coupling with pediatric bronchoscope
    • Similar advantages + disadvantages as Univent
    Other Methods
    • Advance ETT into right of left mainstem bronchus
    • Use Fogarty catheter as blocker
    Management of One Lung Ventilation
    • Verify position of tube with auscultation and fiberoptic bronchoscopy
    • FiO2 1.0
    • Ventilate with 10-12 cc/kg to maintain PaCO2 30-35 mmHg
    • Add CPAP 5 –10 cm H2O to non-ventilated lung if hypoxic
    • Add PEEP 5 cm H2O to ventilated lung (rarely necessary with CPAP to non-ventilated lung)
    Note:
    • Low tidal volume leads to atelectasis in ventilated lung due to decreased FRC
    • High tidal volume shifts blood flow to non-ventilated lung and increases V/Q mismatch
    • PEEP to ventilated lung shifts blood flow to non-ventilated lung and increases V/Q mismatch
    References Available from Dr. Smith



  • Send Comments to Greg Gordon MD, gjg@po.cwru.edu
    Department of Anesthesiology
    The MetroHealth System
    2500 MetroHealth Drive
    Cleveland, Ohio 44109-1998
    Phone: (216) 778-4801
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