(lower should remain OFF until after reperfusion & stabilization)

• Foley catheter: Goal urine output >0.5 mL/kg/hr

• PRBC in the OR; may also need FFP

•  Management before clamping

• Induction of GA: Try to maintain BPs near baseline (HTN can rupture aneurysm, hypotension can cause myocardial ischemia)

• Control HR (usually with esmolol)

• Double-lumen tube (DLT) for thoracic aneurysm (L-DLT may risk hemorrhage if aneurysm is eroding bronchial wall)

• Consider deepening anesthesia prior to x-clamp to avoid HTN response BP control: Nitroprusside (SNP) causes arteriolar dilation & MAP reduction; nitroglycerin (NTG) may prevent myocardial ischemia & ↓ preload

• Maintain relative hypovolemia during preclamp phase to prevent HTN from inc afterload during x-clamp & ↓ risk of MI during x-clamp (do not overhydrate, use NTG/SNP)

•  Preparation for clamp release

• Gradually load with volume

• Wean vasodilators & have pressors ready

• Lighten anesthetic

•  Postclamp management

• Give fluid bolus, blood (if warranted)

• Gradual release of clamp can ↓ hemodynamic changes

• If severe hypotension results, reclamp & reassess

• Pressors (phenylephrine) may be needed, although not usually given prophylactically

• ↑ ventilation

• ABG before & after x-clamp removal (guide fluid & electrolyte management)

• Monitor HCT & correct coagulopathies

• Use standard extubation criteria (pts often stay intubated 2° large volume shifts)

•  Preventing renal failure

• Risk with supraceliac > suprarenal > infrarenal

• Maintain renal perfusion pressure with highest possible MAP that myocardium will tolerate

• Maintain intravascular volume

• Consider mannitol (0.5 g/kg before x-clamping), furosemide, Ca²⁺ blockers, dopamine, fenoldopam (not proven effective); bicarb drip

•  Preventing spinal cord ischemia

• SSEP monitoring—not useful (2/3 of cord is supplied by anterior spinal artery → motor)

• Maintain highest MAP (distal aortic perfusion pressures) that myocardium can handle

• Keep CSF pressures low (consider spinal fluid drain)

• Consider shunt to maintain distal perfusion during x-clamp

• Consider hypothermic CPB or circulatory arrest

• Consider administering steroids, barbiturates

• Consider epidural cooling

• Spinal cord perfusion pressure (SCPP)

SCPP = distal aortic pressure – (greater of spinal CSF pressure or CVP)

• If monitoring distal pressures, aim for SCPP >30 mm Hg; can drain CSF via lumbar drain, up to ∼15 mL/15 min (risk of brainstem herniation with rapid or excessive CSF drainage → limit to ∼75 mL)

• Avoid excessive SNP (hypotension → ↓ perfusion, cerebral vasodilation → ↑ ICP transmitted to CSF)

• Avoid hyperglycemia (consider insulin infusion for glucose >200)

• Consider mild hypothermia (passive cooling to about 34°C)

•  Other complications

• Nerve injuries: Recurrent laryngeal nerve during thoracoabdominal repairs, brachial plexus injuries (poor pt positioning)

Thoracoabdominal Aortic Aneurysm (TAAA) Repair

•  Management similar to AAA (see above) with following key points

Crawford Classification of TAAA (I–IV)

•  I: Descending thoracic aortic aneurysm distal to subclavian artery

•  II: Aneurysm originating at subclavian artery to distal abdominal aorta

•  III: Aneurysm from mid–descending thoracic aorta to distal abdominal aorta

•  IV: Abdominal aortic aneurysm (below the diaphragm)

Stanford Classification of TAAA (A–B)

•  Type A: Intimal tear (acute) in aorta from ascending aorta to descending aorta

•  Type B: Intimal tear (acute or chronic) in aorta from descending aorta down

Possible Associated Findings with TAAA

•  Airway deviation/compression

•  Tracheal deviation/compression

•  Hemoptysis

•  Esophageal deviation/compression

•  Distortion & compression of central vasculature/anatomy

•  Hemothorax & mediastinal shift

•  Reduced distal perfusion

(Adapted from: Dunn P. Clinical Procedures of the MGH. Philadelphia, PA: Lippincott Williams & Wilkins.)

Anesthetic Management of TAAA

•  A-line: Ascending aneurysm, usu. placed in L radial (innominate artery may be involved); descending aneurysm, usu. placed in R radial (left subclavian may be clamped)

•  Circ arrest: If utilized, will need to pack head in ice (cover monitors so they remain dry)

•  TEE: Used intraop to detect intimal tear, coronary ostia, AI, assess embolic risk

•  Neuroprotection: Thiopental 3–10 mg/kg (may offer benefit for cerebral protection)

•  Partial bypass: May be used for descending aneurysms

•  Ventilation: One-lung ventilation often employed

•  Access: 1 large-bore peripheral IV (16- or 14-gauge) + 1 large-bore central line

BP Control During TAAA

•  If no bypass: Maintain SBP at baseline SBP + ¹⁄₂ of peak aortic x-clamp SBP

•  If bypass: Maintain SBP at baseline SBP

•  Can reduce proximal HTN during aortic clamp by ↑ flow to pump & ↓ flow to heart

•  SNP should be used sparingly (or not at all) during aortic clamp (risk of ↓ spinal cord & renal perfusion)

•  ↓ conc of volatile agent & turn off vasodilators before aortic unclamp

•  Volume repletion with colloid, crystalloid, blood products before & after aortic unclamp

Carotid Endarterectomy

•  Indication: History of stroke, TIA, or significant arterial occlusion on angiography

•  Morbidity: Incidence of concomitant CAD ≈ 50%; periop mortality 1–4%

•  Anesthetic techniques

• Regional advantages

• Pt can tell you of neurologic symptoms/deficits during surgery

• Less anesthesia required for pts with significant comorbidities

• Avoidance of coughing/bucking at case end

• Less postop hyper- & hypotension

• Potentially reduced ICU & hospital stay

• Regional disadvantages
“A good general is always better than a bad regional” (if regional not working, pt may be uncomfortable, moving, & tachycardic)

Some providers give “deep sedation” + regional anesthesia

(eliminates benefit of awake detection of neurologic deficits)

• Regional: Deep cervical block

• Technique: Inject anesthetic at C2, C3, C4 in line drawn between mastoid process, & C6 transverse process; needle should have slight caudal angulation, contact transverse process, withdraw 2 mm & inject

• Potential complications:

Intravertebral artery injection

Horner’s syndrome (sympathetic chain)

Hoarseness (recurrent laryngeal nerve)

• Regional: Superficial cervical block

• Technique: Inject anesthetic just posterior to sternocleidomastoid (goal to spread anesthetic subcutaneously & behind SCM) at C6 level, & fanned 2–3 cm superior & inferior

• Easy technique with minimal risk & excellent efficacy

• General anesthesia: Advantages

• Potential for brain protection by volatile and intravenous anesthetics

• General anesthesia: Disadvantages

• Necessitates careful planning & drug management to avoid HTN, coughing, & bucking during emergence & extubation

• Can get hypotension (minimal surgical stim but must keep pt still)

• No proven mortality ↓ with either technique (GA vs. regional)

•  Intraoperative shunting

• Provides blood flow from common carotid artery to internal carotid artery (distal/superior to site of x-clamp)

• Indicated in pts with significant contralateral dz

• Stump pressure: Measurement of pressure distal to site of x-clamp, need to provide well-flushed A-line tubing over drape stump pressure <50 mm Hg = indication for shunting

• Risk of plaque dislodgement, intimal injury, & air embolus

•  Hemodynamic management

• Avoid tachycardia (↑ myocardial O₂ demand) & hypotension (↓ coronary flow)

• Maintain MAP slightly above baseline (optimizes collateral blood flow)
May be difficult to maintain normal MAP (minimal surgical stim)
Phenylephrine infusion → ideal to maintain MAP without raising heart rate

• Consider nitroglycerin for reduction of BP at induction/emergence
Esp in chronically HTN pts (may have wide swings in MAP)

• Consider esmolol/metoprolol to prevent tachycardia
Intubation, reversal of neuromuscular blockade, extubation

• Consider A-line placement prior to induction in pts with known CAD

•  Intraoperative brain monitoring has not been shown to improve outcomes

• CNS monitors:

• Awake: ↓ cardiac morbidity & HTN, shorter ICU stay

• EEG: May correlate with neuro changes

• SSEPs: Sensitive, but intermittent indicator of cortical ischemia

• Stump press poor sensitivity/specificity

• Transcranial Doppler/brain oximetry/JvO₂ (unproven)

•  Perioperative complications

• Brain hypoperfusion (avoid hyperglycemia)

• Bradycardia (esp during carotid body manipulation)
Can avoid with lidocaine infiltration by surgeon

• Intraoperative stroke (consider if delayed emergence/mental status change)

• Hematoma: Evacuate hematoma 1st, manipulate airway 2nd

• Diagnosis: Progressive stridor & subjective difficulty breathing; often difficult to see hematoma (dressings/patient size)

• Treatment: Pt back to OR stat—if condition worsening, open wound prior to airway manipulation; attempts at intubation can be impossible (may result in airway swelling/bleeding, making situation worse)

ENDOVASCULAR PROCEDURES

Endovascular AAA Repair

•  Monitoring for most limited to A-line (plus large-bore IV access)

•  Pressors/vasodilators usually not needed

•  Conversion to open procedure rate <5% (should always anticipate this possibility)

•  Anesthetic options

• General

• Complex cases (inexperienced surgeon) or pt refuses regional/MAC

• Always considered as backup for conversion to open procedure

• Regional

• Spinal: Duration of procedure usually precludes this

• Epidural: Allows for ideal anesthesia of incision sites (bilateral femoral vascular access), But must be prepared to delay case if achieve bloody/traumatic tap or intravascular catheter

• Regional techniques may ↓ incidence of hypercoagulability & perioperative vessel clot formation (esp for lower extremity procedures)

• Sedation

• Ideal for thin pts (less dissection necessary) if surgeons apply local

• Pt must remain still for hrs on uncomfortable fluoroscopy bed

• Contrast induced nephropathy a concern (2° to extensive angiography) (see below)

Carotid Stent Placement

•  Requires immobile pt (minimal head/neck movement) & able to tolerate fluoroscopy table

•  Consider narcotic/α-2 agonist technique (may avoid sedation-associated confusion)

Distal Angioplasty/Thrombectomy

•  Pts with operative lower limb vascular dz have >50% incidence of concomitant CAD

•  Procedure times often long (on uncomfortable fluoroscopy bed) usually best to avoid long infusions/large doses of midazolam/propofol (problem of confusion/disorientation)

•  Always be prepared for conversion to open procedure

•  Regional techniques may ↓ incidence of hypercoagulability & perioperative vessel clot formation (esp for lower extremity procedures)

ENDOVASCULAR SAFETY CONCERNS

•  Perioperative β-blockade: Current ACC guidelines – recommend perioperative β-blockade in vascular pts found to have myocardial ischemia on preop testing

(less strong evidence for pts with low/intermediate cardiac risk)

•  Transfusion triggers: Evidence suggests vascular pts allowed to bleed below a hemoglobin level of 10 mg/dL have ↑ incidence of periop myocardial ischemia

•  Regional anesthesia & anticoagulation (see Chapter 6, Regional Anesthesia)

CONTRAST-INDUCED NEPHROPATHY (CIN)

•  ARF after ischemia or contrast thought 2° to acute tubular necrosis from

• Free-radical formation, which is promoted in acidic environment (e.g., renal medulla)

• Contrast-related ↓ in renal blood flow

• Atheroembolism

•  Tips to Avoid CIN

• Maintain plasma volume, good urine output

• NaHCO₃ may be protective: D₅ NaHCO₃ 154 mEq/L (from pharmacy)

• Load: 3 mL/kg over 1 hr, given 1 hr before contrast

• Maintenance: 1 mL/kg/hr until 6 hr after procedure

• Use 110 kg max weight for calculations

• If bolus leads to significant HTN → stop bolus, diurese before injecting contrast, then resume infusion

• N-acetylcysteine (free-radical scavenger)

• 600 mg PO bid starting day before surgery and through day of surgery

•  Risk Factors

• Patient factors: Renal dz, diabetes, CHF, ↑ age, anemia, LV dysfx

• Nonpatient factors: ↑ osmolar or ionic contrast, contrast viscosity & volume

PERIPHERAL VASCULAR SURGERY

•  Preop risk: Patients often have significant comorbidities (↑ risk of associated CAD)

•  Procedures: Bypass grafts (fem-pop, ilio-fem, etc.), embolectomy, pseudoaneurysm repair

•  Monitoring: Invasive monitors per pt condition (hemodynamics often labile)

(place A-line in side opposite surgery)

•  Anesthetic

• General anesthesia/regional/MAC

• Epidural & GA → associated with comparable rates of cardiac morbidity

• Continuous epidural/spinal

• ↓incidence of postop vascular graft clotting (Anesthesiology 1993:79:422)

• Continuous lumbar epidural catheter commonly used (occ spinal)

• Awake pts can notify personnel of acute MI symptoms (chest pain)

• Helpful for postop pain control

• Intraop heparin after epidural placement does not ↑ risk of epidural hematoma

• Epidural associated with ↓ incidence of reoperation for inadequate tissue perfusion (compared to GA) (Anesthesiology 1993;79[3]:422–434)

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