Diseases of Thoracic Aorta
A 77-year-old man presents to the emergency room with severe back pain following a syncope. A dissecting aortic aneurysm is reported to extend from just beyond the aortic valve through to the abdominal aorta.
What preoperative evaluation is required?
Preoperatively, a brief cardiac history (myocardial ischemia/infarction, stents, medication) is needed. The anesthesia team should note the patient's neurological function and confirm the presence and quality of all peripheral pulses. ECG should be examined especially pertaining to chronic/acute myocardial ischemic events. MRI, chest x-ray (CXR), and echocardiography should be reviewed to determine the extent of the dissection and to determine the competency of the aortic valve as well as overall hemodynamics.
What monitors are required and how should induction proceed?
Bilateral radial artery catheters are placed to make sure perfusion is equivalent on both sides of the aortic arch. Femoral vessels are best left for surgical/perfusion access if possible. Any anesthetic agents may be used assuming the surgeon is not planning on using evoked potentials monitoring. Blood pressure control is essential to prevent further expansion or rupture of the dissecting aortic aneurysm and to avoid organ ischemia.
The surgeon informs you that DHCA is required to repair the aortic arch. How will you proceed?
After initiation of CPB, the perfusionist cools the patient to a core temperature of less than 15°C and the anesthesia team packs the patient's head in ice. At this point the patient's circulation is suspended. All intravenous infusions must be stopped completely! The surgeon repairs the aorta and the patient is rewarmed.
On separating from bypass the patient has new LV anterior and lateral wall motion abnormalities. What is the possible differential diagnosis?
New wall motion abnormalities can occur secondary to myocardial ischemia due to kinking of the coronary arteries if they have been reattached to the aortic graft, air, or particulate emboli entrained though the coronary arteries or inadequate myocardial protection. TEE demonstrates flow in the left coronary artery. Mean arterial pressure is increased through the administration of vasopressin 2 U/h and eventually LV function returns to normal.
The patient is weaned from CPB and protamine is administered slowly; however, the patient continues to bleed profusely from the suture sites. How should you proceed?
Assuming that the bleeding is not surgical, efforts are undertaken to correct for probable post DHCA, bypass coagulopathy. Platelets, fresh frozen plasma, cryoprecipitate, and packed red blood cells are given as indicated. If hemorrhage is life threatening, activation of a "mass transfusion" protocol can be helpful to ensure the timely delivery of blood products. Occasionally, to correct the coagulopathy, recombinant factor VII may be administered (Chapter 16).
The coagulopathy is corrected and the patient is transferred to the ICU. What postoperative issues must be considered?
Patients following DHCA for aortic surgery may experience stroke, renal failure, mesenteric ischemia, and myocardial dysfunction secondary to either hypoperfusion or embolic events. If postoperative bleeding due to coagulopathy persists, as will often be the case, blood products will be administered according to the results of laboratory tests such as PT, PTT, thromboelastography, or platelet count.
Discussion of the high risks associated with aortic dissections and other diseases of the thoracic aortic (eg, stroke and death) and their treatment should be made clear to patients and their families so that expectations are realistic.