ANESTHESIA FOR AORTIC SURGERY By: DR. Ahmed Mostafa Assist. Prof. of anesthesia Benha faculty of medicine.

Indications for aortic surgery include: -Aortic dissections. -Aortic aneurysms. -occlusive disease. -Trauma. -Coarctation of the aorta.

Preoperative Considerations *Large intraoperative blood losses. * Aortic cross-clamping -↑↑ lt. ventricular afterload. -Severe hypertension. -myocardial ischemia. -left ventricular failure. -aortic valve regurgitation may be precipitated. -↓↓ organ perfusion distal to the occlusion. -Interruption of blood flow to the spinal cord paraplegia→ -Interruption of blood flow to kidneys →renal failure.

ANESTHETIC MANAGEMENT

Surgery on the Ascending Aorta -Incision: median sternotomy -cardiopulmonary bypass. -Complications: 1-Aortic regurgitation. 2-Long aortic cross-clamp time. 3-Large intraoperative blood loss. 4-Coronary re-implantation may be needed.

To monitor ABP -The left radial artery should be used. -the femoral and dorsalis pedis arteries are suitable alternatives. To control B.P.→ Nitroprusside is generally used. Aortic dissection→ Beta -Adrenergic blockade (esmolol). Bradycardia should be avoided. If there is risk of aortic rupture during Sternotomy→ The arterial inflow cannula for CPB is placed in a femoral artery instead of ascending aorta and the venous outflow cannula is placed in the femoral vain. Surgery on the Ascending Aorta

Surgery Involving the Aortic Arch -Incision: median sternotomy. -Deep hypothermic circulatory arrest (following institution of CPB). -cerebral protective measures: 1-systemic and topical hypothermia. (Hypothermia to 15°C) 2-thiopental infusion to maintain a flat EEG. 3-Methylprednisolone or Dexamethasone. 4-Mannitol, and Phenytoin are also commonly used. 5-Long rewarming time.

-Incision: Left thoracotomy -One-lung anesthesia greatly facilitates surgical exposure and reduces pulmonary trauma from retractors. -Right radial artery is used for ABP monitoring. -A nitroprusside infusion to prevent excessive increases in blood pressure above the clamp. -Increasing anesthetic depth just prior to cross- clamping may also be helpful. Surgery Involving the Descending Thoracic Aorta

Major anesthetic problems: 1-Excessive intraoperative bleeding. -Prophylaxis with aprotinin. -A blood scavenging device (cell saver). - Adequate venous access. 2-Release hypotension during de-clamping: -Decreasing anesthetic depth. -volume loading. -Slow release of the cross-clamp. -A small dose of a vasopressor. -Sodium bicarbonate if pH < 7.20.

Surgery Involving the Descending Thoracic Aorta 3-PARAPLEGIA. Artery of Adamkiewicz: this artery has a variable origin from the aorta, arising between T5 and T8 in 15%, between T9 and T12 in 60%, and between L1 and L2 in 25% of patients. Higher rates are associated with: -Cross-clamping periods longer than 30 min. -Extensive surgical dissections. -Emergency procedures.

Surgery Involving the Descending Thoracic Aorta 3-PARAPLEGIA. Spinal cord protective measures include: 1- Heparin-coated shunt to maintains distal perfusion. 2-Methylprednisolone. 3-Mild hypothermia. 4-Mannitol and drainage of cerebrospinal fluid (CSF). 5-magnesium is also protective in some animal models.

4-RENAL FAILURE An increased incidence is reported after: - emergency procedures. -prolonged cross-clamping time. -Prolonged hypotension. -preexisting renal disease. Surgery Involving the Descending Thoracic Aorta

4-RENAL FAILURE Renal protective measures : 1-Infusion of mannitol (0.5 g/kg) prior to cross- clamping. 2-Low (renal)-dose dopamine. 3-Preserve renal blood flow e.g. Fenoldopam infusion. 4-Maintenance of adequate cardiac function. Surgery Involving the Descending Thoracic Aorta

Surgery on the Abdominal Aorta * Incision:-Anterior trans-peritoneal or -Anterolateral retroperitoneal approach. *Cross-clamp: supraceliac, suprarenal, or infrarenal aorta. *Anesthetic problems: -The large incision -Extensive retroperitoneal surgical dissection. -Increase fluid requirements (up to 10–12 mL/kg/h). -Increase blood loss. -Renal impairment.

Surgery on the Abdominal Aorta Anesthetic technique: Combined general epidural anesthesia. Advantages: -↓↓ anesthetic requirement. -↓↓Release of stress hormones. -Provides postoperative epidural analgesia.

Postoperative Considerations -Patients undergoing surgery on the ascending aorta, the arch, or the thoracic aorta should remain intubated and ventilated for 2–24 h postoperatively. -Patients undergoing abdominal aortic surgery are often extubated at the end of the procedure. -All patients typically continue to require a marked increase in maintenance fluids for several hours postoperatively.

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