Ruptured AAA

Endovascular Repair
         If endovascular repair is possible, a sheath is placed in the femoral artery (contralateral to the occlusion balloon, if in place). The aortic stent-graft is advanced over a guidewire and an angiogram performed to confirm positioning. The stent-graft is then deployed with the goal of “landing” the proximal cuff in a normal segment of aorta. If a bifurcated graft is used, due to involvement of the iliac arteries, guidewires are advanced into place in each of the graft limbs and bridging stents deployed to achieve a distal seal zone in the iliac arteries.
         If the aneurysm involves aortic branch vessels (renal, superior mesenteric, or celiac arteries) these may be covered by emergent placement of the aortic stent. In this scenario, repair may also involve snorkel / chimney stents of these vessels or a hybrid open bypass approach to restore flow to the visceral organs.

Open Repair
         If the anatomy is unfavorable for endovascular repair and/or the aneurysm involves visceral aortic branches, an open repair may be required. Induction of general anesthesia should proceed after aortic occlusion balloon placement under local / MAC and after adequate arterial / venous access are obtained, preferably with the patient prepped / draped and the surgeon scrubbed to facilitate rapid access if decompensation occurs.
         A midline laparotomy incision is made, followed by rapid dissection aimed at achieving control proximal to the rupture via cross-clamping a portion of normal aorta. The aorta is then opened and repair proceeds. The cross-clamp is moved caudally in a stepwise fashion as anastomoses and re-implantation of the visceral vessels are completed in order to limit overall tissue ischemia. One should be prepared for an exaggerated hypotensive response and metabolic derangements with unclamping, in particular if there is a longer period of balloon occlusion and/or surgical cross-clamp.
         Once the repair is complete and all clamps are off, effort is turned toward control of ongoing bleeding and “drying up.” These patients almost always remain intubated when transferred to the ICU.

2. Patient demographics

Overall, risk factors for development of a AAA include age > 65, male sex, COPD, CAD, PAD, cerebrovascular disease, family h/o AAA, certain connective tissue disorders (Marfan’s, Ehlers-Danlos), HLD, HTN, and smoking. The risks, specifically for rupture, are increasing aneurysm size, rate of expansion, symptoms related to AAA, age > 60, female sex, HTN, and smoking. Despite this, rAAA patients are predominantly males (4:1) and age 65-80.

Only 50% of patients with rupture survive to presentation. Outcomes are better if patients present with pain from dissection prior to rupture. Frank rupture carries approximately a 75% mortality where those with intraperitoneal bleeding fare worse than retroperitoneal bleeds where there is potentially some tamponade effect. Patients who suffer cardiac arrest or require intubation prior to transfer have extremely poor outcomes and should be considered for palliation. Mortality increases with time from presentation to intervention, adding significant time pressure to the complexities of aortic repair.

3. Preoperative Assessment

Given the emergent nature of rAAA repair, a focused history is warranted, which needs to be balanced with the need to proceed efficiently to the operating room. In the unstable patient, this assessment is often concurrent with resuscitation. This focuses on cardiovascular stability, functional status (as a surrogate for CV risk stratification), and identification of factors that may immediately affect management. If feasible, based on staffing availability, one anesthesia provider should go to the emergency department to assess the patient while another prepares the OR.

• Vitals (CV stable / unstable ; respiratory compromise)
• NPO status (determine need for RSI, due to full stomach / visceral ischemia / peritonitis, if GA is planned / possible)
• Functional status (METS)
• CV and pulmonary comorbidities, renal dysfunction, diabetes
• Critical medications : beta-blockers, antihypertensives, insulin/oral hypoglycemics, anticoagulant / antiplatelet
• 12 lead EKG, standard
• Labs (including CBC, electrolytes / CMP, coags, type & screen, crossmatch)
• CT angiogram vs. ultrasound to define anatomy (surgeon’s purview)

Part of the assessment is to answer the following questions, which will affect how to proceed with planning the anesthetic and the sequence of events leading to ultimate repair of the ruptured aneurysm. Some of this evaluation should be based on the proposed surgical plan and findings should be discussed with the surgical team to integrate into the overall plan for repair.

• Is the patient stable or unstable?
• Is the surgical plan for EVAR (favorable anatomy) vs open repair?
• Is there a plan for balloon occlusion of the aorta?
• Can the patient tolerate part or all of the procedure with local anesthesia or sedation (ability to lie flat, degree of pain, respiratory compromise)?
• If GA is necessary, where does induction fit into the timeline (i.e. after aortic occlusion balloon placement)?
• Are there any anticipated pitfalls based on comorbidities and/or vascular anatomy?

4. Preoperative Preparations

• Priority should be given to proceed to the OR as quickly as possible, after which additional medications and equipment can be prepared.
• When additional anesthesia providers are available, delegate tasks (preop assessment, medication preparation, monitors, arterial / venous access, etc) to allow these to occur in parallel, prevent overlap, and facilitate rapid surgical intervention.
• In addition to access & monitors (below), request a Belmont, CellSaver (even if infected to help wash / prepare blood), ACT machine, ABL (blood gas analyzer).
• Order blood (10:10:2 minimum).
• Consider early activation of MTP (place order; call Blood Bank at 3-1313; send runner to pick up 4:4:1).
• Ensure the following labs / tests are sent (not necessarily resulted): CBC, CMP, coags, T&S, cross-match, ABG, EKG.
• Medications to prepare (delegate someone to obtain (from cardiac Pyxis) and draw up these once in the OR)
  • Vasopressors / inotropes : Norepi, Epinephrine, CaCl, Vasopressin
  • Arterial vasodilators : nicardipine (prediluted in cardiac pyxis), clevidipine, nitroprusside
  • Beta blockers : esmolol
  • Insulin
• If the patient is on anticoagulants / anti-platelet agents, consider reversing, if indicated :
  • Determine dose and timing of last dose
  • Consider indication for anticoagulation and consequence of reversing
  • Consult “IP Adult Anticoagulation Reversal Orders” order set for guidance and ordering of reversal agents
• Consider TEE if plan is for open repair, particularly, w/ supraceliac clamp

5. Access/Fluids

• In general, 2 good PIVs are the minimum to start. An arterial line is not a pre-requisite to sheath placement for aortic balloon occlusion.
• For most patients (particularly those who are unstable), priority should be given to placement of a femoral sheath and positioning of the aortic occlusion balloon prior to further placement of lines.
• In stable patients, a discussion with the surgical team should occur as to the timing of arterial and central access.
• In general, placement of a large-bore CVC (MAC, trialysis, introducer sheath) is prudent after balloon control and before induction of GA
• Consider placement of a RIC (rapid infusion catheter) or use to size up an existing PIV.

6. Monitors

• Standard ASA monitors plus...
• Arterial line (may be deferred until after occlusion balloon placed for unstable patients but always prior to induction of GA)
• CVP (consider this if placing CVC)
• ACT monitoring during heparinization
• POCT blood gas analysis (ABL 90)

7. Anesthetic Technique

The decision on whether to perform the procedure under MAC or general anesthesia depends on several factors. The ability to tolerate lying flat and still for the duration of the procedure may be limited by abdominal pain. If possible, an aortic occlusion balloon should be placed under local anesthesia or minimal sedation. Careful titration of analgesics and anxiolytics can be used to facilitate this. Consider using low-dose remifentanil if abdominal pain is the main limitation in lying flat or still. Exercise caution with excessive sedation, particularly in patients with comorbid OSA, obesity, and/or preexisting lung disease. In addition, visceral ischemia and peritonitis can increase the risk of aspiration, making preservation of airway reflexes favorable.

If anatomy is favorable for an endovascular repair and the patient can tolerate lying flat / still for the procedure, consideration should be given to performing the entire repair under MAC. This can allow for greater hemodynamic stability but comes with the risk of having to covert to GA mid-procedure. Outcomes are generally better with endovascular over open repair as well as local / MAC over general anesthesia, if possible / tolerated.

If general anesthesia is necessary, either due to planned open repair or intolerance of positioning, proceed with caution, preferably after an aortic occlusion balloon has been positioned, and preferably after arterial and large bore central venous access is obtained. While there is the advantage of better operating conditions, vasodilation on induction can result in hemodynamic instability due to hypovolemia in the setting of preexisting unknown cardiopulmonary disease. In addition, loss of abdominal tone, which may be tamponading a contained rupture, may result in conversion to a free rupture with uncontrolled hemorrhage. Surgeons should be scrubbed and the patient prepped prior to induction.

8. Key procedure related points

• Consider placement of femoral sheath and aortic occlusion balloon prior under local anesthesia or minimal sedation prior to additional line placement or induction of general anesthesia.
• Permissive hypotension (goal SBP 80-100, HR < 100) is recommended prior to surgical / endovascular control of bleeding to limit disruption of clot and further exsanguination. If this cannot be achieved passively, then careful titration of beta blockers (esmolol) to limit wall stress and arterial vasodilators (nicardipine / clevidipine) can be employed to achieve this goal.
• Aortic balloon occlusion results in similar physiology to surgical aortic cross-clamping and unclamping (high afterload while occluded, may even require vasodilators). The unclamping vasodilation / hypotension as well as subsequent metabolic derangements can be profound if there is a significant duration of balloon occlusion or surgical cross-clamp.
• Close communication and coordination with the surgical team is imperative during critical portions of the procedure, in particular, during induction, clamping / unclamping, occlusion balloon inflation / deflation, and major hemodynamic changes.
• Partial / graded unclamping or re-clamping / balloon reinflation can be used to help mitigate or temporize ongoing hemodynamic instability with unclamping
• After unclamping and resolution of any reperfusion instability, often the goal is tight BP control (SBP 110-140), with an aim to avoid hypoperfusion and avoid high pressure on anastomoses / graft edges to reduce the risk of endoleak or anastomotic failure.
• Similar to acute trauma coagulopathy, avoid the lethal triad (dilutional coagulopathy, hypothermia, acidosis) partly through balanced transfusion in a 1:1:1 RBC:FFP:Plt ratio, guided further by frequent lab measurements (Note : 1 pheresis unit = 6 pack of pooled platelets).
• Be prepared to treat hyperkalemia from transfusion and metabolic / respiratory acidosis. If time permits, washing units of product prior to transfusion (via CellSaver) can reduce the potassium load from banked products.
• Typically, lumbar drains are NOT placed for rAAA repair, given the anatomical location and the urgency of securing the rupture. If a lumbar drain is needed (due to coverage / ligation of mid-thoracic spinal arteries in thoracoabdominal aneurysms), it can be placed during the post-op period, potentially with neuroradiology using CT-guidance.

9. Potential complicatons

• Massive hemorrhage (expect on the order of liters if uncontained rupture or open repair)
• Hypertensive response and cardiac dysfunction with aortic cross-clamping (or aortic balloon occlusion)
• Coagulopathy and impaired lactate clearance from hepatic ischemia (particularly in supraceliac cross-clamp / balloon occlusion)
• Hypotension on unclamping / balloon deflation
• Metabolic derangements on unclamping (hyperkalemia, metabolic / respiratory acidosis)
• Cardiac arrhythmia / dysfunction subsequent to hypotension, metabolic derangements (know where pads/defib is located in hybrid room; if needed, use radiolucent pads)
• Mesenteric ischemia which can persist after removal of cross-clamp / balloon occlusion
• Abdominal compartment syndrome due to either ongoing visceral hypoperfusion or mechanical compression from bleeding into the (retro)peritoneum. Monitor for increased ventilatory pressures and UOP. May require an ex lap in endovascular procedures to evacuate (retro)peritoneal blood.
• Prolonged respiratory failure due to pulmonary edema / lung injury (use lung protective ventilation in GA cases).

10. Positioning / ergonomic considerations

• Supine, unless chest rotated to right for open TAAA repair
• Generally large portion of the pelvis, abdomen, and thorax are prepped even for endovascular repairs, which creates issues w/ EKG leads placement and warming (place underbody BAER hugger)
• Consider bundling lines directed off of the right corner of the fluoro table to ensure out of the likely path of rotating XR gantry.
• Prepare sufficient extensions for bolus and infusion lines, especially if connected to PIVs, as the fluoro table will move significantly during the case. Access to the patient may be more limited after draping.

11. Duration of case

Variable. Depends on several factors including endovascular vs open, degree of coagulopathy and need for resuscitation, complexity of aortic anatomy, etc.

12. References / Additional Reading

• Berry et al. Anesthesia for endovascular repair of ruptured abdominal aortic aneurysms. BJA Education. 2022. 22(6) : p 208
• Chaikof et al. The SVS guidelines on the care of patients with an abdominal aortic aneurysm. J Vasc Surg. 2018. 67(1) : p 2
• Chee et al. Management of bleeding in vascular surgery. BJA. 2016. 17(2) : p 85
• Cheesman & Maund. Anesthesia for the ruptured aortic aneurysm. Anaesth Intensive Care Med. 23(4) : p 229
• Gelman S. The pathophysiology of aortic cross-clamping and unclamping. Anesth. 1995. 82 : p 1026
• Hope et al. Modern Anesthetic Management of Ruptured Abdominal Aortic Aneurysms, J CT Vasc Anesth. 2016. 30(6) : p 1676
• Powell et al. Observations from the IMPROVE trial concerning the clinical care of patients with ruptured abdominal aortic aneurysm. Br J Surg. 2014. 101 : p 216