AA Aneurysm Open: Difference between revisions

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=== Overview ===
=== Overview ===
* The open AAA repair procedure is becoming rarer due to the rise of endovascular stent placements.
* The open AAA repair procedure has become less common due to advancements in endovascular stent placements.
* It is associated with significant blood loss and complexity.
* Open procedures are associated with significant blood loss and complex surgical management.


=== Procedure Description ===
=== Procedure Description ===
* Repair is performed through a midline abdominal incision.
* An open AAA repair involves a midline abdominal incision to access and repair the aneurysm.
* Most open AAA procedures have been replaced by endovascular AAA repair.
* Most open AAA procedures have been replaced by endovascular repair due to the latter's minimally invasive nature and reduced recovery times.
* Elective surgery is recommended for aneurysms greater than 5 cm in diameter.
* Elective surgery is typically indicated for aneurysms exceeding 5 cm in diameter.
* Repair methods include:
* Repair methods include:
   * Straight tube graft
   * **Straight Tube Graft**: Involves replacing the aneurysmal segment with a straight synthetic graft.
   * Aorta to bilateral iliac graft replacement
   * **Aorta to Bilateral Iliac Graft Replacement**: Replaces the aneurysmal segment with a graft extending from the aorta to both iliac arteries.


=== Symptoms ===
=== Symptoms ===
* Typically asymptomatic, but may present with lumbar back or abdominal pain.
* AAAs are often asymptomatic and may be discovered incidentally during routine medical examinations.
* When symptomatic, patients may experience lumbar back pain, abdominal pain, or a pulsatile abdominal mass.
* Advanced symptoms may include:
  * Collapse
  * Shock
  * Coma


=== Imaging ===
=== Imaging ===
* Methods include CT scan, MRI, basic x-ray, or angiography.
* Diagnostic imaging options include:
* 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).
  * **CT Scan**: Provides detailed cross-sectional images to assess aneurysm size and location.
  * **MRI**: Useful for evaluating complex cases and assessing soft tissue structures.
  * **X-ray**: Less commonly used but can provide preliminary information.
  * **Angiography**: Can visualize blood vessels and assess the aneurysm's relationship with major arteries.
* **CT Angiography** is increasingly preferred for its ability to detail aneurysm size, location (infra- or supra-renal), and the condition of major branches such as the inferior mesenteric artery.


=== Causes ===
=== Causes ===
* Atherosclerosis
* **Atherosclerosis**: The most common cause, involving the buildup of plaques in the aorta.
* Marfan syndrome
* **Genetic Disorders**: Conditions such as Marfan syndrome and Ehlers-Danlos syndrome.
* Ehlers-Danlos syndrome
* **Dissection**: Tear in the aortic wall leading to aneurysm formation.
* Dissection
* **Congenital Vasculitis**: Inflammation of blood vessels present from birth.
* Congenital vasculitis
* **Infections**: Including syphilis and other rare causes.
* Infections, including syphilis


=== Preoperative Tips ===
=== Preoperative Tips ===
* Maintain patient warmth.
* **Patient Management**:
* Keep heart rate slow (avoid tachycardia).
  * Maintain normothermia to prevent hypothermia-related complications.
* Prevent anemia (keep hematocrit (HCT) >25-30).
  * Avoid tachycardia by managing heart rate.
* Prevent hypertension to avoid stressing the aneurysm.
  * Prevent anemia by maintaining a hematocrit (HCT) level >25-30%.
  * Prevent hypertension to reduce stress on the aneurysm.


=== Procedure Details ===
=== Procedure Details ===
* The surgeon cross-clamps above and below the aneurysm, opens the aorta, removes the diseased section, and replaces it with a graft.
* The surgical technique involves:
* Clamps are then removed; estimated blood loss (EBL) can be substantial.
  * **Cross-Clamping**: The aorta is clamped above and below the aneurysm to control blood flow.
* Be aware of hemodynamic changes during clamping and unclamping.
  * **Aneurysm Removal**: The diseased portion of the aorta is excised.
  * **Graft Placement**: A synthetic graft is inserted to replace the removed section.
  * **Clamp Removal**: The clamps are removed, and blood flow is restored.


=== Preoperative Preparation ===
=== Preoperative Preparation ===
* Verify if the patient has had a thorough cardiac workup; if not, treat them as a coronary artery disease (CAD) patient.
* Ensure thorough cardiac evaluation; treat as CAD patients if necessary.
* Line and Monitoring:
* **Line and Monitoring**:
   * Use the largest bore peripheral IVs available (14G if possible).
   * Use the largest bore peripheral IVs available (preferably 14G).
   * Right internal jugular (IJ) line is recommended.
   * A right internal jugular (IJ) line is ideal for central access.
   * Consider a transesophageal echocardiogram (TEE) instead of a Swan-Ganz catheter for monitoring left ventricular filling status.
   * Consider a transesophageal echocardiogram (TEE) for continuous monitoring of left ventricular filling status.
   * Have fluid warmers (1-2) and rapid transfusers or pressure bags ready.
* **Equipment Preparation**:
   * Prepare blood transfusion tubing (2) with normal saline (NSS).
   * Fluid warmers (1-2)
   * Use a cell saver and warming blankets (2).
  * Rapid transfusers or pressure bags
   * Blood transfusion tubing (2) with normal saline (NSS)
   * Cell saver
  * Warming blankets (2)


=== Induction and Intubation ===
=== Induction and Intubation ===
* To avoid hypertension with direct laryngoscopy:
* To minimize hypertension during intubation:
   * Consider adding Esmolol to induction to mitigate BP spikes.
   * Add Esmolol to blunt blood pressure spikes.
   * Use Remifentanil (0.5-1 mcg/kg/min) 8 minutes before intubation.
   * Use Remifentanil (0.5-1 mcg/kg/min) 8 minutes before intubation.
   * High narcotic induction doses may be used.
   * High doses of narcotics may be employed for induction.
   * Consider a GlideScope to reduce stimulation.
   * Utilize a GlideScope to reduce laryngoscopic stimulation.
* Anesthesia:
* **Anesthesia**:
   * General anesthesia with endotracheal tube (ETT).
   * General anesthesia with endotracheal tube (ETT).
   * Thoracic epidural is recommended; administer before the incision.
   * Thoracic epidural anesthesia may be administered before incision.
   * Rapid Sequence Induction (RSI) is often utilized.
   * Rapid Sequence Induction (RSI) is often used due to the risk of aspiration.
   * Nasogastric (NG) tube is advisable.
   * Nasogastric (NG) tube placement is advised.
* Duration: 3-5 hours.
* **Duration**: 3-5 hours.
* Position: Supine with arms tucked.
* **Position**: Supine with arms tucked.
* Estimated Blood Loss (EBL): 500-1,000 mL.
* **Estimated Blood Loss (EBL)**: 500-1,000 mL.


=== Common Intubation Doses ===
=== Common Intubation Doses ===
* Fentanyl: 10-20 mcg
* **Fentanyl**: 10-20 mcg
* Midazolam (Versed): 5 mg
* **Midazolam (Versed)**: 5 mg
* Large narcotic doses may cause rigidity; these reduce the need for volatile agents during induction.
* High doses of narcotics can lead to rigidity; these doses help reduce the need for volatile anesthetics.


=== Pre-Induction ===
=== Pre-Induction ===
* Use a priming dose of a non-depolarizing muscle relaxant or succinylcholine for RSI.
* **Priming Dose**: Use a non-depolarizing muscle relaxant or succinylcholine for RSI.
* Connect fluids to the warmer as soon as possible.
* **Fluid Management**:
* Keep the patient covered; use a Bair Hugger after central line placement.
  * Connect fluids to the warmer immediately.
* Administer a 200-500 cc fluid bolus before induction.
  * Use a Bair Hugger for warming.
  * Administer a 200-500 cc fluid bolus before induction.


=== Induction to Pre-Clamp Period Goals ===
=== Induction to Pre-Clamp Period Goals ===
* Avoid hypertension to prevent aneurysm rupture.
* **Avoid Hypertension**: Prevent aneurysm rupture due to high blood pressure.
* Administer 0.5 g/kg Mannitol (typically 12.5-25 g) 30 minutes before cross-clamping.
* **Mannitol Administration**: Administer 0.5 g/kg (typically 12.5-25 g) 30 minutes before cross-clamping.
* Have Lasix available and follow the surgeon’s instructions for administration.
* **Lasix**: Have available for managing fluid balance as instructed by the surgeon.


=== Preparation for Aortic Cross-Clamping ===
=== Preparation for Aortic Cross-Clamping ===
* Ensure nitroglycerin and/or Milrinone are available.
* **Medications**:
* Monitor ionized calcium (Ca) levels.
  * Ensure availability of nitroglycerin and/or Milrinone.
* Maintain volume and prepare to manage BP drops when unclamping.
* **Monitoring**:
  * Check ionized calcium (Ca) levels.
* **Volume Management**:
  * Maintain adequate volume and prepare to manage blood pressure drops during unclamping.


=== Complications of Aortic Cross-Clamping ===
=== Complications of Aortic Cross-Clamping ===
* Renal failure:
* **Renal Failure**:
   * Increased risk with preexisting renal disease, cross-clamp time >30 minutes, and hypovolemia/decreased cardiac output without bypass.
   * Risk factors include preexisting renal disease, cross-clamp duration >30 minutes, and hypovolemia without bypass.
   * Renal protection may include Mannitol (0.5-1.0 g/kg) before clamping, and potentially Lasix, Dopamine, and Fenoldopam.
   * **Renal Protection**:
* Paraplegia:
    * Mannitol (0.5-1.0 g/kg) is crucial.
   * The anterior spinal cord is most prone to ischemia due to its single arterial supply.
    * Consider Lasix, Dopamine, and Fenoldopam based on surgical needs.
   * Prolonged ischemia can occur with cross-clamping times >30-45 minutes or during perioperative hypotension.
* **Paraplegia**:
   * The anterior spinal cord is particularly vulnerable due to its single arterial supply.
   * Prolonged ischemia can result from cross-clamping >30-45 minutes or perioperative hypotension.


=== Methods to Prevent BP Drops with Unclamping ===
=== Methods to Prevent BP Drops with Unclamping ===
* Decrease anesthetic depth.
* **Anesthetic Management**:
* Maintain a hypervolemic state while clamped.
  * Decrease anesthetic depth.
* Infuse Neosynephrine before clamp removal.
  * Maintain hypervolemia while clamped.
* Unclamp slowly as per the surgeon’s direction.
* **Vascular Management**:
  * Infuse Neosynephrine before clamp removal.
  * Gradual unclamping is preferred to mitigate hemodynamic changes.


=== Unclamping Effects ===
=== Unclamping Effects ===
* Reactive hyperemia due to reduced systemic vascular resistance (SVR) from metabolites in ischemic tissue.
* **Reactive Hyperemia**: Caused by a drop in systemic vascular resistance (SVR) from ischemic tissue metabolites.
* Lactic acid causes vasodilation.
* **Lactic Acid**: Dilates blood vessels; some surgeons may request sodium bicarbonate (NaHCO3).
* Consider NaHCO3 if requested by the surgeon.
* **Ventilation Management**:
* Increase minute ventilation to manage acidosis; hypocarbia will constrict vessels and redirect blood flow to ischemic tissues.
  * Increase minute ventilation to control acidosis.
  * Hypocarbia helps constrict vessels and redirect blood flow to ischemic tissues distal to the clamp.


=== Late Operative and Postoperative Considerations ===
=== Late Operative and Postoperative Considerations ===
* Common issues:
* **Edema Management**:
   * Facial, scalp, and airway edema.
   * Facial, scalp, and airway edema are common.
* Recommendations:
   * Delay extubation until edema subsides; elevate the head of the bed (HOB) overnight.
   * Delay extubation until edema subsides.
* **Fluid Shifts**:
  * Elevate the head of bed (HOB) overnight.
   * Postoperative fluid shifts can cause pulmonary issues, delaying extubation despite apparent readiness.
   * Monitor for fluid shifts postoperatively to address potential pulmonary issues.


=== Spinal Cord Blood Supply ===
=== Spinal Cord Blood Supply ===
* Supplied by:
* **Sources**:
   * One anterior spinal artery.
   * One anterior spinal artery
   * Two posterior spinal arteries.
   * Two posterior spinal arteries
   * A network of small segmental spinal arteries.
   * A network of small segmental spinal arteries
* The anterior spinal cord is particularly vulnerable to ischemia due to its single arterial supply.
* The anterior spinal cord is most prone to ischemia due to its single arterial supply.


=== Possible Complications ===
=== Possible Complications ===
* Ruptured aneurysm
* **Ruptured Aneurysm**
* Cardiac and pulmonary problems
* **Cardiac and Pulmonary Problems**
* Nerve damage causing pain or numbness in the legs
* **Nerve Damage**: Causing pain or numbness in the legs.
* Damage to intestines or nearby organs
* **Damage to Intestines or Nearby Organs**
* Graft infection
* **Graft Infection**
* Injury to the ureter(s)
* **Ureter Injury**
* Incisional hernia
* **Incisional Hernia**
* Spinal cord injury
* **Spinal Cord Injury**
* Sexual dysfunction
* **Sexual Dysfunction**
* Lower extremity paralysis
* **Lower Extremity Paralysis**
* Death
* **Death**

Latest revision as of 10:37, 21 July 2024


Open Abdominal Aortic Aneurysm (AAA) Repair

Overview

  • The open AAA repair procedure has become less common due to advancements in endovascular stent placements.
  • Open procedures are associated with significant blood loss and complex surgical management.

Procedure Description

  • An open AAA repair involves a midline abdominal incision to access and repair the aneurysm.
  • Most open AAA procedures have been replaced by endovascular repair due to the latter's minimally invasive nature and reduced recovery times.
  • Elective surgery is typically indicated for aneurysms exceeding 5 cm in diameter.
  • Repair methods include:
 * **Straight Tube Graft**: Involves replacing the aneurysmal segment with a straight synthetic graft.
 * **Aorta to Bilateral Iliac Graft Replacement**: Replaces the aneurysmal segment with a graft extending from the aorta to both iliac arteries.

Symptoms

  • AAAs are often asymptomatic and may be discovered incidentally during routine medical examinations.
  • When symptomatic, patients may experience lumbar back pain, abdominal pain, or a pulsatile abdominal mass.
  • Advanced symptoms may include:
 * Collapse
 * Shock
 * Coma

Imaging

  • Diagnostic imaging options include:
 * **CT Scan**: Provides detailed cross-sectional images to assess aneurysm size and location.
 * **MRI**: Useful for evaluating complex cases and assessing soft tissue structures.
 * **X-ray**: Less commonly used but can provide preliminary information.
 * **Angiography**: Can visualize blood vessels and assess the aneurysm's relationship with major arteries.
  • **CT Angiography** is increasingly preferred for its ability to detail aneurysm size, location (infra- or supra-renal), and the condition of major branches such as the inferior mesenteric artery.

Causes

  • **Atherosclerosis**: The most common cause, involving the buildup of plaques in the aorta.
  • **Genetic Disorders**: Conditions such as Marfan syndrome and Ehlers-Danlos syndrome.
  • **Dissection**: Tear in the aortic wall leading to aneurysm formation.
  • **Congenital Vasculitis**: Inflammation of blood vessels present from birth.
  • **Infections**: Including syphilis and other rare causes.

Preoperative Tips

  • **Patient Management**:
 * Maintain normothermia to prevent hypothermia-related complications.
 * Avoid tachycardia by managing heart rate.
 * Prevent anemia by maintaining a hematocrit (HCT) level >25-30%.
 * Prevent hypertension to reduce stress on the aneurysm.

Procedure Details

  • The surgical technique involves:
 * **Cross-Clamping**: The aorta is clamped above and below the aneurysm to control blood flow.
 * **Aneurysm Removal**: The diseased portion of the aorta is excised.
 * **Graft Placement**: A synthetic graft is inserted to replace the removed section.
 * **Clamp Removal**: The clamps are removed, and blood flow is restored.

Preoperative Preparation

  • Ensure thorough cardiac evaluation; treat as CAD patients if necessary.
  • **Line and Monitoring**:
 * Use the largest bore peripheral IVs available (preferably 14G).
 * A right internal jugular (IJ) line is ideal for central access.
 * Consider a transesophageal echocardiogram (TEE) for continuous monitoring of left ventricular filling status.
  • **Equipment Preparation**:
 * Fluid warmers (1-2)
 * Rapid transfusers or pressure bags
 * Blood transfusion tubing (2) with normal saline (NSS)
 * Cell saver
 * Warming blankets (2)

Induction and Intubation

  • To minimize hypertension during intubation:
 * Add Esmolol to blunt blood pressure spikes.
 * Use Remifentanil (0.5-1 mcg/kg/min) 8 minutes before intubation.
 * High doses of narcotics may be employed for induction.
 * Utilize a GlideScope to reduce laryngoscopic stimulation.
  • **Anesthesia**:
 * General anesthesia with endotracheal tube (ETT).
 * Thoracic epidural anesthesia may be administered before incision.
 * Rapid Sequence Induction (RSI) is often used due to the risk of aspiration.
 * Nasogastric (NG) tube placement is advised.
  • **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
  • High doses of narcotics can lead to rigidity; these doses help reduce the need for volatile anesthetics.

Pre-Induction

  • **Priming Dose**: Use a non-depolarizing muscle relaxant or succinylcholine for RSI.
  • **Fluid Management**:
 * Connect fluids to the warmer immediately.
 * Use a Bair Hugger for warming.
 * Administer a 200-500 cc fluid bolus before induction.

Induction to Pre-Clamp Period Goals

  • **Avoid Hypertension**: Prevent aneurysm rupture due to high blood pressure.
  • **Mannitol Administration**: Administer 0.5 g/kg (typically 12.5-25 g) 30 minutes before cross-clamping.
  • **Lasix**: Have available for managing fluid balance as instructed by the surgeon.

Preparation for Aortic Cross-Clamping

  • **Medications**:
 * Ensure availability of nitroglycerin and/or Milrinone.
  • **Monitoring**:
 * Check ionized calcium (Ca) levels.
  • **Volume Management**:
 * Maintain adequate volume and prepare to manage blood pressure drops during unclamping.

Complications of Aortic Cross-Clamping

  • **Renal Failure**:
 * Risk factors include preexisting renal disease, cross-clamp duration >30 minutes, and hypovolemia without bypass.
 * **Renal Protection**:
   * Mannitol (0.5-1.0 g/kg) is crucial.
   * Consider Lasix, Dopamine, and Fenoldopam based on surgical needs.
  • **Paraplegia**:
 * The anterior spinal cord is particularly vulnerable due to its single arterial supply.
 * Prolonged ischemia can result from cross-clamping >30-45 minutes or perioperative hypotension.

Methods to Prevent BP Drops with Unclamping

  • **Anesthetic Management**:
 * Decrease anesthetic depth.
 * Maintain hypervolemia while clamped.
  • **Vascular Management**:
 * Infuse Neosynephrine before clamp removal.
 * Gradual unclamping is preferred to mitigate hemodynamic changes.

Unclamping Effects

  • **Reactive Hyperemia**: Caused by a drop in systemic vascular resistance (SVR) from ischemic tissue metabolites.
  • **Lactic Acid**: Dilates blood vessels; some surgeons may request sodium bicarbonate (NaHCO3).
  • **Ventilation Management**:
 * Increase minute ventilation to control acidosis.
 * Hypocarbia helps constrict vessels and redirect blood flow to ischemic tissues distal to the clamp.

Late Operative and Postoperative Considerations

  • **Edema Management**:
 * Facial, scalp, and airway edema are common.
 * Delay extubation until edema subsides; elevate the head of the bed (HOB) overnight.
  • **Fluid Shifts**:
 * Postoperative fluid shifts can cause pulmonary issues, delaying extubation despite apparent readiness.

Spinal Cord Blood Supply

  • **Sources**:
 * One anterior spinal artery
 * Two posterior spinal arteries
 * A network of small segmental spinal arteries
  • The anterior spinal cord is most prone 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**
  • **Ureter Injury**
  • **Incisional Hernia**
  • **Spinal Cord Injury**
  • **Sexual Dysfunction**
  • **Lower Extremity Paralysis**
  • **Death**
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