AA Aneurysm Open: Difference between revisions

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== Open Abdominal Aortic Aneurysm (AAA) Repair ==
* **Overview:**
  * Open AAA repair is becoming less common due to the availability of endovascular stent placements.
  * The procedure is associated with significant blood loss and is generally more complex.
* **Procedure Description:**
  * Involves repairing the AAA through a midline abdominal incision.
  * Most open AAA repairs have been replaced by endovascular AAA repairs.
  * Elective surgery is recommended for aneurysms >5 cm in diameter.
  * Repair methods:
    * Straight tube graft
    * Aorta to bilateral iliac graft replacement
* **Symptoms:**
  * Usually 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 for assessing size, location (infra- or supra-renal), and major branch status (e.g., inferior mesenteric artery).
* **Causes:**
  * Atherosclerosis
  * Marfan syndrome
  * Ehlers-Danlos syndrome
  * Dissection
  * Congenital vasculitis
  * Infections, including syphilis
* **Preoperative Tips:**
  * Keep the patient warm.
  * Maintain a slow heart rate (avoid tachycardia).
  * Avoid anemia (keep hematocrit (HCT) >25-30).
  * Prevent hypertension (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 removed with potential for large estimated blood loss (EBL).
  * Hemodynamic changes should be managed carefully.
* **Preoperative Preparation:**
  * Ensure thorough cardiac workup; treat as a coronary artery disease (CAD) patient if not done.
  * Line and Monitoring:
    * Place the largest bore peripheral IVs possible (14G if possible).
    * Use a right internal jugular (IJ) line.
    * 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.
    * Blood transfusion tubing (2) should be set up with normal saline (NSS).
    * Prepare a cell saver and warming blankets (2).
* **Induction and Intubation:**
  * Methods to avoid hypertension with direct laryngoscopy:
    * Consider adding Esmolol to induction to blunt BP spikes.
    * Use Remifentanil (start at 0.5-1 mcg/kg/min) 8 minutes before intubation.
    * High narcotic induction doses can be used, similar to heart cases.
    * Consider using a GlideScope to reduce stimulation.
  * Anesthesia:
    * General anesthesia with endotracheal tube (ETT).
    * Thoracic epidural is recommended; dose or start an infusion before incision.
    * Rapid Sequence Induction (RSI) is commonly used.
    * 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
  * Be prepared for rigidity with large narcotic doses.
* **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 (usually 12.5-25 g) 30 minutes before cross-clamping.
  * Have Lasix available; 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 drop when unclamping.
* **Complications of Aortic Cross-Clamping:**
  * Increased risk of renal failure:
    * Preexisting renal disease
    * Cross-clamp time >30 minutes
    * Hypovolemia and decreased cardiac output without partial or complete bypass
  * Renal protection:
    * Mannitol (0.5-1.0 g/kg) is crucial before clamping.
    * Consider Lasix, Dopamine, and Fenoldopam based on surgeon's needs.
  * Paraplegia:
    * The anterior spinal cord, supplied by a single artery, is most prone to ischemia.
    * Prolonged spinal cord ischemia occurs with cross-clamping times >30-45 minutes or during perioperative hypotension.
* **Methods to Prevent BP Drops with Unclamping:**
  * Decrease anesthetic depth.
  * Maintain hypervolemia while clamped.
  * Infuse Neosynephrine before clamp removal.
  * Unclamp slowly as directed by the surgeon.
* **Unclamping Effects:**
  * Reactive hyperemia due to a drop in systemic vascular resistance (SVR) from metabolites in ischemic tissue.
  * Lactic acid causes vasodilation.
  * Increased minute ventilation may help control acidosis and manage blood flow distribution.
* **Late Operative and Postoperative Considerations:**
  * Common issues:
    * Facial, scalp, and airway edema.
  * Recommendations:
    * Delay extubation until edema subsides.
    * Elevate the patient’s head of bed (HOB) overnight.
    * Monitor 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 most susceptible to ischemia due to single arterial supply.
* **Possible Complications:**
  * Ruptured aneurysm
  * Cardiac and pulmonary issues
  * Nerve damage causing pain or numbness in the legs
  * Intestinal or organ damage
  * Graft infection
  * Ureter injury
  * Incisional hernia
  * Spinal cord injury
  * Sexual dysfunction
  * Lower extremity paralysis
  * Death

Revision as of 10:26, 21 July 2024

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