Endovascular aortic repair

Endovascular aortic repair

Anesthesia type	General Neuraxial (for abdominal aneurysm) Local with MAC (rare)
Airway	ETT if general
Lines and access	PIV x 2 (at least 1 large bore (14-16 G) Arterial line (right sided preferred)
Monitors	Standard ASA monitors 5-lead EKG Arterial line TEE (for thoracic aneurysm)
Primary anesthetic considerations
Preoperative	Assess co-existing cardiovascular comorbidities
Intraoperative	Heparin for anticoagulation Consider decrease BP immediately prior to stent deployment and/or increase BP post-deployment
Postoperative	Monitor for spinal/intraabdominal ischemia due to graft occlusion
Article quality
Editor rating	In development
User likes	0

Endovascular aortic repair is a surgical procedure by which a stent graft is deployed along the extent of an aortic lesion through vascular access, typically via the common femoral vessels. The stent graft protects the aneurysmal wall from high blood pressure in the aorta decreasing the risk of rupture.

Aortic repair is indicated when an aneurysm is at high risk of rupture, which is defined as:

• Size larger than 5.5 cm
• Growth of 10 mm or more per year

The procedure involves obtaining vascular access to allow the introduction of the stent deployment apparatus. Prior to the introduction of stent deployment apparatus, systemic heparinization is provided. Fluoroscopy is performed with IV contrast to evaluate vascular anatomy and guide stent placement. Once the stent graft is deployed and placement confirmed with fluoroscopy/TEE without the presence of endoleak or aortic dissection, the stent graft introducer is removed and vascular access sites are closed.

Preoperative management

Patient evaluation

System	Considerations
Neurologic	Assess for presence of history cerebrovascular disease or carotid stenosis by obtaining baseline neurologic exam, especially strength of lower extremities and auscultation.
Cardiovascular	Assess baseline functional status and evaluate for myocardial ischemia, previous myocardial infarction, valvular dysfunction, heart failure and peripheral arterial disease.
Pulmonary	Assess for COPD, cigarette smoking, and reversible pulmonary pathology. Smoking cessation of at least 8 weeks is optimal.
Renal	Preoperative hydration and avoidance of nephrotoxic drugs during the perioperative period are important to reduce the risk of kidney injury due to IV contrast used during the procedure.

Labs and studies

• Type and screen
• Contrast-enhanced spiral CT scans of the thorax and thoracic aortography to assess the dimensions of the aneurysms
  • This allows for the assessment of adequate proximal and distal neck for surgical planning. The CT scan also helps assess the adequacy of the vessel used for vascular access for the stent introducer system
• EKG to assess for any myocardial ischemia or previous infarction
• TTE to assess valvular disease, size and extent of aneurysm, and LV function
• Exercise or pharmacologic stress testing or radionuclide imaging may be warranted

Operating room setup

• Arterial catheter and transducer
• Hotline on fluid warmer
• Infusion pumps
• Vasopressor infusions available (usually norepinephrine on pump)
• Push dose pressors drawn up
• Heparin and protamine
• +/- lumbar drain setup
• Heated circuit (if available)

Patient preparation and premedication

• IV midazolam (+/- Fentanyl) for anxiety
• PO acetaminophen for pain control

Regional and neuraxial techniques

Spinal and/or epidural may be considered for endovascular abdominal aortic aneurysm repair

If lumbar drain needed, usually placed by VIR and capped the day prior. When entering the OR, attach the lumbar drain chamber tubing to the lumbar drain before laying the patient down to ensure adequate CSF flow. Once the patient is supine on the OR bed, check again that CSF is freely flowing. At this point, make sure the transducer is zeroed to the level of the subarachnoid space (typically even with the level of the ear).

Intraoperative management

Monitoring and access

• Standard ASA monitors
• 5-lead EKG
• Arterial line is required as it allows prompt vasopressor titration in response to blood pressure change, particularly just prior to stent deployment and post stent deployment
  • Right sided preference as left sided vascular access from the surgical team may be needed allowing for an easier approach to the aorta compared to right sided approach. Also, the stent graft may block the L subclavian artery leading to false reading
• TEE used to assist in the identification of aneurysm necks, monitor the deployment of the stent graft, endoleaks status post deployment, and aortic dissection (Endovascular Thoracic Aneurysm Repair)
• Urine output monitoring in the setting of possible renal vessel occlusion from deployment of stent graft and contrast induced nephropathy
• Spinal drain (a.k.a. lumbar drain) CSF draining and pressure monitoring if placed for high risk patient undergoing endovascular thoracic aneurysm stent grafting
• Somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) may be used to assess for spinal ischemia for patient undergoing endovascular thoracic stent grafting
• At Least 1 large bore IV (14-16G) given risk of vascular injury or rupture

Induction and airway management

• Most common anesthesia type is general anesthesia
  • May need to reverse neuromuscular blockade if neuromonitoring is used
• If neuraxial anesthesia is chosen, supplement with minimal to deep sedation as needed
• Rarely, local anesthetic placement by the surgical team with monitored anesthesia care is used, depending on patient cooperativity.

Positioning

• Supine +/- slight right lateral decubitus (endovascular thoracic aortic aneurysm repair)

Maintenance and surgical considerations

• Volatile anesthetics supplemented with opioids for analgesia if neuromonitoring is not used
• If neuromonitoring is used, 0.5 MAC of volatile anesthetic supplemented by IV anesthetic/opioids or TIVA and avoiding neuromuscular blockade after intubating dose
• Administration of heparin prior to introducer insertion

• Verification of activated clotting time (ACT) throughout the case with goal of 200 seconds until introducer is removed
• Maintenance of baseline MAP as this patient population have increase risk of CVA, MI, aortic dissection, and paraplegia
• Just prior to stent deployment, BP must be decrease to reduce the risk of graft migration during deployment with vasodilators
• Post stent graft deployment, BP is increased to ensure perfusion especially if there is a risk of spinal ischemia with vasopressor
• Closed loop communication with surgical team regarding heparinization and ACT monitoring
• Spinal cord ischemia is a rare, but devastating complication of both open and endovascular aortic aneurysm repair. Incidence in EVAR has been reported as 0.21% and up to 6.9% in TEVAR
• Remember that spinal cord perfusion pressure is equal to the mean arterial pressure minus the cerebral spinal cord pressure (SCPP = MAP - ICP)
• The most common mitigation strategy is blood pressure augmentation (increasing MAP) with MAP goals usually >90
  • SCI is multifactorial, but in endovascular repair, it is usually thought to be the result of the permanent interruption, by covering with the stent, of sufficient sources of cord blood supply to render a portion of the cord nonviable - these sources include the segmental arteries, artery of Adamkiewicz, subclavian, and hypogastric arteries - as well as decrease of pressure in those arteries, by major bleeding or other causes of shock
  • Episodes of delayed paraplegia/paraparesis have been reversed by increasing blood pressure and cardiac output. Clearly, both an increase in arterial pressure and a decrease in CSF pressure result in a net increase in perfusion of the spinal cord. Similarly, because central venous pressure and CSF pressure are—at least in part—additive in increasing outflow pressure from the spinal canal, it is important to avoid hemodynamic management strategies that entail high venous pressure
• Larger grafts will cover more of the arteries that supply the spinal cord and, therefore, increase the risk of ischemia. In these higher risk cases, a lumbar drain can be used to drain CSF, lowering the ICP, and, therefore, increasing the spinal cord perfusion pressure. Whether CSF drainage improves outcomes is not entirely clear
  • Drainage can be set to an ICP threshold after the drain transducer is "zeroed" to the patients spine (i.e., the drain will drain CSF when the ICP is greater than 12mmHg)
  • Drainage can be set as a volume per hour (i.e., drain 10ml per hour)
  • Overly aggressive CSF drainage carries a risk of intracranial hemorrhage (related to tearing bridging vessels). This risk can be minimized by not draining more than 20ml per hour and/or targeting ICP of 8-10mmHg
• Occasionally (rarely at UNC), somatosensory evoked potentials (SSEPs) and/or motor evoked potentials (MEPs) may be used to monitor for SCI
• Because of its more tenuous blood supply, the anterior two-thirds of the spinal cord are most at risk for ischemia which presents as a painful myelopathy known as anterior spinal artery syndrome

Emergence

• PONV prophylaxis
• Reversal of neuromuscular blockade if used
• Assessment of hip flexion if spinal cord is at risk for ischemia
• Reversal of heparin with protamine with confirmation of ACT returning to normal value
• Maintain BP goals

Postoperative management

Disposition

• PACU then floor
• Consider ICU if intraoperative complications occur

Pain management

• Postoperative pain is usually mild

• Multimodal pain management
  • PO/IV acetaminophen
  • PO/IV opioid
  • Local anesthetic at vascular access sites
  • Epidural analgesia if chosen as anesthetic technique
  • Usually avoiding NSAID due to pre-existing renal disease or potential renal injury

Potential complications

• Endoleaks
• Vascular injury
• Graft migration
• Stent frame fractures
• Breakdown of graft material
• Spinal cord ischemia or infarction secondary to occlusion of intercostal arteries
• Intraabdominal ischemia secondary to occlusion of vessels supplying the gastro-intestinal organ including the celiac artery, superior mesenteric artery, inferior mesenteric artery, and renal arteries

• Bleeding from groin site or retroperitoneal bleeding
• Contrast induced nephropathy

Procedure variants

	Thoracic Aortic Aneurysms	Abdominal Aortic Aneurysms
Unique considerations	Use of TEE and possible neuromonitoring and lumbar drain	Neuraxial anesthesia possible
Position	Supine +/- slight right lateral decubitus	Supine
Surgical time	1-3 hours	1-3 hours
EBL	Minimal, unless vascular injury	Minimal, unless vascular injury
Postoperative disposition	Usually PACU to the floor, possible ICU	Usually PACU to the floor
Pain management	Multimodal	Multimodal
Potential complications	Paraplegia	Intraabdominal ischemia/infarction