AA Aneurysm Open: Difference between revisions

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AA Aneurysm Open (view source)

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== Open Abdominal Aortic Aneurysm (AAA) Repair ==
=== Overview ===
* The open AAA repair procedure is becoming rarer due to the rise of endovascular stent placements.
* It is associated with significant blood loss and complexity.
=== Procedure Description ===
* Repair is performed through a midline abdominal incision.
* Most open AAA procedures have been replaced by endovascular AAA repair.
* Elective surgery is recommended for aneurysms greater than 5 cm in diameter.
* Repair methods include:
  * Straight tube graft
  * Aorta to bilateral iliac graft replacement
=== Symptoms ===
* Typically asymptomatic, but may present with lumbar back or abdominal pain.
=== Imaging ===
* Methods include CT scan, MRI, basic x-ray, or angiography.
* CT angiography is preferred as it provides details on size, location (infra- or supra-renal), and the status of major branches (e.g., inferior mesenteric artery).
=== Causes ===
* Atherosclerosis
* Marfan syndrome
* Ehlers-Danlos syndrome
* Dissection
* Congenital vasculitis
* Infections, including syphilis
=== Preoperative Tips ===
* Maintain patient warmth.
* Keep heart rate slow (avoid tachycardia).
* Prevent anemia (keep hematocrit (HCT) >25-30).
* Prevent hypertension to avoid stressing the aneurysm.
=== Procedure Details ===
* The surgeon cross-clamps above and below the aneurysm, opens the aorta, removes the diseased section, and replaces it with a graft.
* Clamps are then removed; estimated blood loss (EBL) can be substantial.
* Be aware of hemodynamic changes during clamping and unclamping.
=== Preoperative Preparation ===
* Verify if the patient has had a thorough cardiac workup; if not, treat them as a coronary artery disease (CAD) patient.
* Line and Monitoring:
  * Use the largest bore peripheral IVs available (14G if possible).
  * Right internal jugular (IJ) line is recommended.
  * Consider a transesophageal echocardiogram (TEE) instead of a Swan-Ganz catheter for monitoring left ventricular filling status.
  * Have fluid warmers (1-2) and rapid transfusers or pressure bags ready.
  * Prepare blood transfusion tubing (2) with normal saline (NSS).
  * Use a cell saver and warming blankets (2).
=== Induction and Intubation ===
* To avoid hypertension with direct laryngoscopy:
  * Consider adding Esmolol to induction to mitigate BP spikes.
  * Use Remifentanil (0.5-1 mcg/kg/min) 8 minutes before intubation.
  * High narcotic induction doses may be used.
  * Consider a GlideScope to reduce stimulation.
* Anesthesia:
  * General anesthesia with endotracheal tube (ETT).
  * Thoracic epidural is recommended; administer before the incision.
  * Rapid Sequence Induction (RSI) is often utilized.
  * Nasogastric (NG) tube is advisable.
* Duration: 3-5 hours.
* Position: Supine with arms tucked.
* Estimated Blood Loss (EBL): 500-1,000 mL.
=== Common Intubation Doses ===
* Fentanyl: 10-20 mcg
* Midazolam (Versed): 5 mg
* Large narcotic doses may cause rigidity; these reduce the need for volatile agents during induction.
=== Pre-Induction ===
* Use a priming dose of a non-depolarizing muscle relaxant or succinylcholine for RSI.
* Connect fluids to the warmer as soon as possible.
* Keep the patient covered; use a Bair Hugger after central line placement.
* Administer a 200-500 cc fluid bolus before induction.
=== Induction to Pre-Clamp Period Goals ===
* Avoid hypertension to prevent aneurysm rupture.
* Administer 0.5 g/kg Mannitol (typically 12.5-25 g) 30 minutes before cross-clamping.
* Have Lasix available and follow the surgeon’s instructions for administration.
=== Preparation for Aortic Cross-Clamping ===
* Ensure nitroglycerin and/or Milrinone are available.
* Monitor ionized calcium (Ca) levels.
* Maintain volume and prepare to manage BP drops when unclamping.
=== Complications of Aortic Cross-Clamping ===
* Renal failure:
  * Increased risk with preexisting renal disease, cross-clamp time >30 minutes, and hypovolemia/decreased cardiac output without bypass.
  * Renal protection may include Mannitol (0.5-1.0 g/kg) before clamping, and potentially Lasix, Dopamine, and Fenoldopam.
* Paraplegia:
  * The anterior spinal cord is most prone to ischemia due to its single arterial supply.
  * Prolonged ischemia can occur with cross-clamping times >30-45 minutes or during perioperative hypotension.
=== Methods to Prevent BP Drops with Unclamping ===
* Decrease anesthetic depth.
* Maintain a hypervolemic state while clamped.
* Infuse Neosynephrine before clamp removal.
* Unclamp slowly as per the surgeon’s direction.
=== Unclamping Effects ===
* Reactive hyperemia due to reduced systemic vascular resistance (SVR) from metabolites in ischemic tissue.
* Lactic acid causes vasodilation.
* Consider NaHCO3 if requested by the surgeon.
* Increase minute ventilation to manage acidosis; hypocarbia will constrict vessels and redirect blood flow to ischemic tissues.
=== Late Operative and Postoperative Considerations ===
* Common issues:
  * Facial, scalp, and airway edema.
* Recommendations:
  * Delay extubation until edema subsides.
  * Elevate the head of bed (HOB) overnight.
  * Monitor for fluid shifts postoperatively to address potential pulmonary issues.
=== Spinal Cord Blood Supply ===
* Supplied by:
  * One anterior spinal artery.
  * Two posterior spinal arteries.
  * A network of small segmental spinal arteries.
* The anterior spinal cord is particularly vulnerable to ischemia due to its single arterial supply.
=== Possible Complications ===
* Ruptured aneurysm
* Cardiac and pulmonary problems
* Nerve damage causing pain or numbness in the legs
* Damage to intestines or nearby organs
* Graft infection
* Injury to the ureter(s)
* Incisional hernia
* Spinal cord injury
* Sexual dysfunction
* Lower extremity paralysis
* Death
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