• No bypass (clamp and sew):- maintain SBP at baseline SBP + � 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

• 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

• Blunt trauma: e.g., MVAs, falls, crush
• Pedestrian struck
• Airplane crash

• Widened mediastinum on CXR
• Chest CT, TEE, Aortography

• 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

• 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

• 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

• 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

• 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

• Advance ETT into right of left mainstem bronchus
• Use Fogarty catheter as blocker

• 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)

• 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