The prevalence of AAAs has increased with the increased age of the population. AAAs are more prevalent in men than in women and Caucasians than African Americans. Hypertension and cigarette smoking appear to increase the risk of developing aneurysms, and atherosclerosis is seen in AAAs. Mortality rates are about 5% for surgical outcomes but much higher for untreated aneurysms.

Most aortic aneurysms are infrarenal and may extend into the iliac arteries. >95% are asymptomatic, and the aneurysms are usually diagnosed on routine examination, abdominal radiography, ultrasound, CT, and MRI—surgical intervention when the AAAs are 5.5cm or greater in diameter.

CAD coexists in 30-40% of patients and should be assessed preoperatively.

EVAAR procedure

Deployment of an endovascular stent graft within the aortic lumen.

It can be used in patients with descending thoracic aortic aneurysms or AAAs

Arterial access via bilateral femoral arteries.

Systemic anticoagulation before catheter manipulation.

The stent over the sheath is deployed using fluoroscopy for the correct position covering the AAA

Pt eligibility

Shape of aneurysm

The neck of the aneurysm

 Involvement of renal and/or iliac arteries

The ability to deliver stent via femoral or iliac arteries

The ability of the patient to compensate for possible lost aortic blood branches (occluded by stent) post-surgery 

Advantages to EVAR compared to Open Aortic Repair (OAR)

Improved hemodynamic stability

Decrease blood loss

Decrease the incidence of embolization

Reduced stress response

Decreased incidence of renal dysfunction

Decreased post-op pain

Decreased length of hospital stay

Complications to EVAR

New onset or worsening of renal failure

• Associated with the use of preoperative and intraoperative use of intravascular dye
  • Ensure good hydration

Allergy to contrast dye

Endovascular leaks

• Type I – inadequate proximal or distal seal
• Type II – backflow from collaterals
• Type III – defect in fabric or seal failures
• Type IV – secondary to the porosity of graft fabrics
  • Resolve with anticoagulation reversal
• Endovascular leaks occur in up to 20% of EVAAR and may cause continued pressurization of the aneurysm, causing compression or kinking of the graft or rupture of native aneurysm.

Endovascular thrombosis

Aortic perforation, aneurysm rupture, aortic dissection

Graft infection

Ischemia to lower extremities/bowel/pelvic area

Hematoma formation

Anesthesia considerations

Always be prepared for conversion to Open Abdominal Repair (OAR) with cross-clamping.

Cross-clamping changes anesthesia significantly as clamping causes

• Increased systemic response above the clamp
  • Increased afterload, preload, contractility, and decreased HR
  • MAP increased up to 40%
• Keep slightly hypovolemic
• Have vasodilators ready on standby
• Note hypotensive below the clamp

Releasing the cross-clamp may cause hypotension (a volume load must be performed before the clamp is released), MI, ischemia, and dysrhythmias.

Monitors

Pulse ox, ECG (lead II for dysrhythmias, V5 for ischemia), NIBP, Temp, PNS

2 large bore IVs

A-line – R radial for descending AAA / L radial for ascending thoracic AAA

Fluid warmers

Bair huggers upper and lower – start lower after reperfusion is established in cases of emergency cross-clamping and open aortic repair

Foley – U/O >0.5 mL/kg/hr

Type and Cross, PRBC in OR

Heparin 50-100 units/kg given IV before catheter manipulation

• ACT >200
• If open procedure, then ACT >380

Heparin: IV onset is immediate, T_1/2 1-3 hrs. dose-dependent

Use porcine Heparin due to decreased risk of HIT (risk of HIT higher with Bovine)

Heparin side effects

Heparin-induced thrombocytopenia - causes thrombocytopenia, tachyphylaxis, and arterial and venous thrombosis.

HIT type

Occurs after 48-72hrs. Heparin interacts with platelets and causes clumping. No thrombosis. Platelet count stays above 100,000 and returns to normal after 3-4 days.

HIT type II

Onset within 7-10 days after exposure to Heparin. Caused by the formation of IgG antibodies directed against platelet-factor-4 heparin complexes. HIT should be suspected with a sudden drop in platelet count of >50%. May see thrombosis such as DVTs, PE, AMI, or skin necrosis, venous limb gangrene, and possible death. 

Goals

Immobile patient

Position

Supine, arms tucked to the side or < 90 degrees. Pressure points padded.

Antibiotics

Cefazolin 1gm IV – weight-based

Anesthesia

GA to facilitate immobile patient with the endovascular graft placement and to be ready for possible conversion to OAR.

Possible epidural placement preop for post-op pain management (OAR)

Surgical time

3hr?

Induction

Avoid hypertension on induction (increases risk of aneurismal rupture)

Preoxygenation

Rocuronium 5 mg IV to minimize myalgias from Succinylcholine

Lidocaine 1 mg/kg/IV

Propofol 1-2 mg/kg/IV – if cardiac hx use Amidate 0.2-0.4mg/kg/iv (2mg/ml vial)

Fentanyl 1-3 mcg/kg/iv

Succinylcholine 0.5-1.5 mcg/kg/min

Tape eyes as soon as the lash reflex is gone, then intubate

Maintenance

Isoflurane

Fentanyl

Vecuronium 0.01mg-.05 mg/kg

Start Hydromorphone for post-op pain management 0.5-2 mg (0.01-0.04 mg/kg)

Monitor ACT

Emergence

Prevention of HTN and tachycardia

Esmolol to control tachycardia on emergence – 25-100 mg (0.5-2.0 mg/kg). May repeat every 5 min. (10 mg/mL)

Zofran 4 mg

Reverse Heparin if needed with protamine 1 mg/100 units of heparin

Protamine reaction

HOTN – histamine release and vasodilation

Anaphylactoid reactions – Hx of fish allergy, vasectomy, prior exposure (NPH insulin or surgery)

Severe pulmonary vasoconstriction – HOTN, increased pulmonary artery pressures, right heart failure

Reversal of muscle relaxants 

Glycopyrrolate 0.01 mg/kg

Neostigmine 0.05-0.07 mg/kg max 5mg

Sugammadex

Complications

Myocardial ischemia

HTN

Hemorrhage

Coagulopathy

Hypothermia

Organ ischemia

Contrast-induced nephropathy is a concern due to extensive angiography using dye

Remember for coiling out of the unit

PT MUST BE FLAT (muscle relaxant)

2 IVs - 3 ports on one

Extensions

Pumps

NTG/Neo/Nipride drip

Heparin