Patients undergoing surgery on the descending thoracic aorta (DTA) present a great anesthetic challenge. The general categories of aortic pathology affecting the DTA include aneurysm, pseudoaneurysm, coarctation, aortic rupture, dissection, intramural hematoma, infection, and atherosclerotic disease (with or without penetrating ulcers). Constructing a safe anesthetic plan for patients requiring DTA surgery mandates an intimate knowledge of aortic pathology, the planned procedure, and strategies to minimize the deleterious effects of surgical manipulation of the aorta. These patients often present in an urgent or emergent fashion with little time to evaluate serious comor-bidities that frequently accompany aortic disease. Emergent procedures require recruiting additional anesthesia personnel so preoperative preparation is carried out with optimal efficiency. The anesthesiologist must review the details of all available imaging studies and create an anesthetic plan that focuses on providing protection and support for all bodily systems affected by the planned procedure.

A successful anesthetic monitoring plan for DTA surgery considers that the nature of these procedures creates hemodynamic instability and hypoperfusion of multiple organ systems. To partially circumvent the effects of interrupting blood flow with aortic cross-clamping, the distal aorta is often perfused using a Gott shunt or partial left-heart bypass (left atrium to distal aorta, iliac or femoral artery bypass with centrifugal pump assist). Femoral arterial blood pressure monitoring is therefore necessary to assess distal arterial perfusion pressure. Distal aortic mean arterial pressure (MAP) is commonly maintained between 60 and 70 mm Hg during the partial bypass period, while proximal MAP is maintained at approximately 90 mm Hg. The use of partial left-heart bypass does not routinely incorporate a heater/cooler exchange unit into the extracorporeal circuit and thus puts the patient at risk for developing profound hypothermia as heat is lost through the extracorporeal circuit. Hypothermia increases the risk of coagulopathic hemorrhage and hyperglycemia (which may exacerbate ischemic injury to the cord and/or heart) in these patients, and thus patient warming systems (e.g., forced convective
air blankets or hydrogel energy conduction pads) should routinely be used in these anesthetics.

Invasive monitoring is essential for DTA surgery. Caution is warranted in choosing a site for radial arterial cannulation because atherosclerotic disease is highly prevalent in patients requiring DTA surgery. Severe subclavian or axillary artery plaquing can result in inaccurate hemodynamic data. Checking bilateral noninvasive cuff pressures can identify significant gradients between the upper extremities. Central venous access is mandated for these procedures so cardiac function and filling pressures can be monitored (e.g., by insertion of a pulmonary artery catheter). Intraoperative transesophageal echocardiography (TEE) monitoring can also be useful in this regard. A dedicated central infusion port for the rapid administration of potent inotropes, vasoconstrictors, and vasodilators is also necessary. Aortic cross-clamping places an acutely increased afterload on the left heart that can result in myocardial ischemia and/or acute left ventricular failure in susceptible patients. Careful monitoring for ischemic electrocardiogram changes and/or signs of acute left ventricular failure (e.g., an acute increase in the pulmonary capillary wedge pressure or new wall motion abnormalities observed with TEE) during aortic cross-clamping is mandatory. Pharmacologic-based afterload reduction (e.g., administration of sodium nitroprusside, nitroglycerin, or fenoldopam) is often indicated during aortic cross-clamping. Aortic cross-clamp removal can also be accompanied by hemodynamic instability (e.g., hypotension) related to an acute reduction in left ventricular afterload and to the release of lactic acid from ischemic tissue beds distal to the clamp if partial left-heart bypass is not employed. The transient increase in circulating lactic acid and potassium associated with cross-clamp removal can also instigate ventricular irritability or arrhythmias. Fluid loading and pharmacotherapy (e.g., administration of α₁-agonists and sodium bicarbonate) just prior to and after unclamping can be useful to quell the hemodynamic deterioration. Large-bore peripheral intravenous access is standard for these procedures to allow for the rapid administration of fluid and/or blood products throughout perioperative period.