Hypothermia and circulatory arrest for surgical resection of aortic arch aneurysms

Repair of thoracic aneurysms, with special emphasis on the preoperative work-up

The anesthetic approach to the patient with a thoracic aortic aneurysm depends on the urgency of repair. Symptomatic patients with leaking aneurysms require urgent intervention, and there is generally little time to perform more than the most basic preoperative assessment. For elective repair, however, one must consider nearly every organ system. Many of the specific issues are inherent to the underlying pathophysiology that has resulted in aneurysm formation, and some stem from the requirements of the surgical procedure itself. A thorough knowledge of the extent and location of the aneurysm, the functional status of the heart, and the coronary artery anatomy are critical. Most patients aged older than 40 years undergo coronary angiography preoperatively, as do younger patients with specific risk factors for myocardial ischemia. Respiratory failure is one of the most common sequelae of these procedures, and a thorough preoperative pulmonary work-up is mandatory. Neurologic deficits are not uncommon postoperatively, and pre-existing deficits in the central nervous system must be sought. Coagulopathy is common in the immediate postoperative period, and preoperative assurance of hemostatic competence is important. Computed tomography scans and magnetic resonance imaging are the mainstay of diagnosis, although the adjunctive use of echocardiography provides important information. Routine preoperative laboratory studies include complete blood count, chemistries, coagulation profile, and indices of renal function; an electrocardiogram, and chest radiograph. Close communication with the surgeon regarding the operative procedure, cannulation strategy (where applicable), and planned evoked potential monitoring is necessary to ensure appropriate perioperative management. Prophylactic antibiotics and antifibrinolytics are routine.

Aortic Arch Replacement Using a Trifurcated Graft: Simple, Versatile, and Safe

BACKGROUND

Hypothermic selective antegrade cerebral perfusion during aortic arch replacement may prevent adverse neurologic sequelae. It can be provided via balloon-tipped catheters or a branched graft sewn to the brachiocephalic vessels. We report a consecutive series of total arch replacement using a trifurcated graft.

METHODS

From September 1999 through October 2004, 109 patients underwent nonemergent total arch replacement using this technique. The graft, placed during a period of hypothermic circulatory arrest, was used for selective cerebral perfusion during the arch reconstruction.

RESULTS

Adverse outcomes were seen in 9 (8.3%) patients: hospital death in 5 (4.6%), and stroke in 5 (4.6%). Transient neurologic dysfunction was noted in 6 (5.5%) patients. Mean duration of hypothermic circulatory arrest was 31.2 +/- 6.6 minutes and selective cerebral perfusion was 65.3 +/- 20.9 minutes. Reoperation for bleeding was required in 3 (2.8%) patients and prolonged intubation in 15 (13.8%). Median intensive care unit stay was 3 days (interquartile range 2-4; range, 1 to 108) and hospital stay was 9 (interquartile range 8-15; range, 5 to 108).

CONCLUSIONS

The trifurcated graft technique results in low rates of perioperative mortality, temporary neurologic dysfunction, and stroke. It may reduce cerebral embolization as it requires no instrumentation of the aortic arch to establish selective cerebral perfusion and, although it mandates hypothermic circulatory arrest to place the graft, this interval is reliably brief enough to fall within accepted safe limits. This strategy leaves no residual arch tissue behind, and allows placement of an elephant trunk proximal to one or more arch vessels if anatomically indicated.

Aneurysms of the innominate artery: surgical treatment of 27 patients

PURPOSE

Aneurysms of the innominate artery (AIA) are widely considered to be a rare entity. We describe our experience with AIAs in the last three decades.

METHODS

From October 1973 to October 2000, we operated on 27 patients with an AIA. The underlying cause of aneurysm was Takayasu's disease in 7 patients, degenerative disease in 6 patients, syphilis in 5 patients, chronic dissection in 3 patients, trauma in 2 patients, infection in 2 patients, a postoperative complication in 1 patient, and Marfan syndrome in 1 patient. AIA was associated with an aortic aneurysm in 17 patients. Fourteen patients had no symptoms. The remaining patients had symptoms, with thromboembolic complications in 7 patients, pain without rupture in 3 patients, and a ruptured aneurysm in 3 patients. In two patients at high risk for surgery who had a small AIA with embolic complications, a cervical approach was used as a means of performing distal exclusion and crossover bypass. In the remaining 25 patients, a midline sternotomy was used. One patient with a ruptured AIA exsanguinated during sternotomy. Ten patients underwent a prosthetic replacement of the ascending aorta and/or aortic arch with a separate prosthetic branch to the innominate artery (IA). Thirteen patients underwent ascending aorta-to-IA prosthetic bypass in association with lateral suture (8 patients) or prosthetic patching (5 patients) of the aorta. One patient with an infected aneurysm was treated by means of resection of the aneurysm, proximal ligation of the IA, and transposition of the right into the left common carotid artery. Cardiopulmonary bypass with deep hypothermic circulatory arrest was used in 10 patients.

RESULTS

Three perioperative deaths occurred (2 of 4 in association with emergency treatment and 1 of 23 with elective treatment). Respiratory complications requiring prolonged artificial ventilation developed in five patients. Two patients had transient worsening of preoperative neurologic deficits. Late results, with a mean follow-up of 85 months, were good.

CONCLUSION

The etiology and presentation of AIAs are variable. Surgical management with current cardiovascular techniques achieves excellent results.

Selective Cerebral Perfusion Via Innominate Artery in Aortic Arch Replacement Without Deep Hypothermic Circulatory Arrest

To attain satisfactory results in aortic arch surgery a reliable method of cerebral protection, avoidance of emboli, and control of hemorrhage is mandatory. Deep hypothermic circulatory arrest is the most common technique at present but gives only a limited period of protection, whereas a complicated aortic arch operation may require more time than anticipated. Therefore the selective cannulation and perfusion of the innominate artery has not been widely used until now because it is uncertain whether the left hemisphere of the brain is adequately perfused. Between 1990 and 1995, 21 of 69 patients within the last 36 months, consisting of 15 men and 6 women averaging 45 +/- 13.4 years, underwent operative treatment for aneurysm (n = 9) or type A dissection (n = 12) involving the aortic valve and aortic arch; selective innominate perfusion (SCP [i]) in moderate hypothermia (28 degreesC) for brain protection was used. Extended perioperative monitoring included bilateral somatosensory-evoked potentials (SEP), transcranial Doppler sonography (TCD), a computer-aided topographical electro-encephalometry (CATEEM), and analysis of the arterial and venous oxygen saturation and desaturation. Mean time periods were 229.7 +/- 56.5 minutes for extracorporeal circulation, 151.7 +/- 34.1 minutes for aortic cross-clamping, and 67.05 +/- 34.03 for selective cerebral perfusion via the innominate artery. Not once did the intraoperative monitoring reveal hints of cerebral damage due to inadequate perfusion. All patients survived surgery but two could not be weaned from the respirator; one died 2 days and the other 6 days after the operation due to multiple organ failure (MOF). Another two patients died after 13 days due to untreatable septic syndrome with pulmonary insufficiency. All four patients died within 30 days, during which time they had aortic dissection involving the complete aortic arch and severe aortic valvular incompetence (grade IV). There was no late death and follow-up time of 19.76 +/- 8.04 months revealed an overall mortality rate of 19%. Only temporary neurological affections (left-sided hemiparesis) were found in two patients (9.5%). Additionally, we observed neuropsychological disturbances in one of these. Our first experience with selective cerebral perfusion via innominate artery and the attendant CATEEM monitoring for assessment of adequate bilateral cerebral perfusion suggests that this method is a useful addition to the armamentarium in complicated aortic arch surgery.

Deep hypothermic intermittent circulatory arrest--an adjunct technique for operations on aneurysms involving the aortic arch

Aneurysms involving the aortic arch were repaired in 12 patients using a technique known as deep hypothermic intermittent circulatory arrest (DHICA). This technique consists of repeated cycles of 20 min of circulatory arrest and 10 min of cerebral and systemic reperfusion. Aneurysms were of the following types: 2 true atherosclerotic aneurysm, 8 aortic dissections, and 2 traumatic aneurysm. There were 2 operative deaths caused by coagulopathy as a result of hepatic failure and difficulty with left ventricular venting. The frequency of circulatory arrest ranged from 2 to 5 cycles, and total circulatory arrest ranged from 20 to 71 min (mean 43.6 min). The lowest tympanic temperature ranged from 17.7 to 19.2 degrees C. No permanent cerebral complications occurred in 10 patients. We believe that this adjunct technique offers excellent results in the surgical treatment of aneurysms involving the aortic arch.

Selective cerebral perfusion during operation for aneurysms of the aortic arch: a reassessment

Thirty-two consecutive patients with thoracic aortic aneurysms who required aortic arch reconstruction were operated on with the aid of extracorporeal circulation and selective cerebral perfusion between January 1986 and August 1990. For selective cerebral perfusion, blood was infused into both the innominate and left common carotid arteries at a rate of 10 mL.kg-1.min-1 using a single roller pump separately from the systemic circulation. In 9 patients treated before March 1987, the operations were performed without open aortic anastomosis (group 1), whereas in 23 patients treated from March 1987 onward we used open aortic anastomosis (group 2). The extracorporeal circulation and cardiac arrest times were significantly longer in group 2, but there was no significant difference in the cerebral perfusion time. Early death occurred in 1 patient in group 1 and 2 in group 2. No serious cerebrospinal neurological complications occurred in either group, and there were similar rates of postoperative hepatic and renal dysfunction in both groups. The present data suggest that selective cerebral perfusion and open aortic anastomosis are useful methods for thoracic aortic aneurysm operation requiring complex repair of the aortic arch.

Determination of brain temperatures for safe circulatory arrest during cardiovascular operation

Profound hypothermia protects cerebral function during circulatory arrest in the surgical treatment of a variety of cardiac and aortic abnormalities. Despite its importance, techniques to determine the appropriate level of hypothermia vary; studies of temperatures recorded from multiple peripheral body sites show inconsistent findings. The purpose of this study is to establish objective criteria to consistently identify intraoperatively the safe level of hypothermia. Our studies are based on experimental evidence showing a correlation between brain temperature and development of electrocerebral silence (ECS) on the electroencephalogram (EEG), and the recognition that the EEG, as an objective measure of brain function, can easily be recorded intraoperatively. We studied 56 patients who required circulatory arrest during operation for replacement of the ascending aorta or aortic arch (N = 55) or aortic valve replacement (N = 1). Peripheral body temperatures from the nasopharynx, esophagus, and rectum and the EEG were continuously recorded during body cooling. Circulatory arrest time ranged from 14 to 109 minutes. No peripheral body temperature from a single site or from a combination of sites consistently predicted ECS. There was a wide variation in temperature among body sites when ECS occurred: nasopharyngeal, 10.1 degrees to 24.1 degrees C; esophageal, 7.2 degrees to 23.1 degrees C; rectal, 12.8 degrees to 28.6 degrees C. Fifty-one (91%) of the 56 patients survived. Three had neurological deficits, none clearly related to hypothermia. Two patients (3.6%) required reexploration for postoperative bleeding. We conclude that monitoring the EEG to identify ECS is a safe, consistent, and objective method of determining the appropriate level of hypothermia.

Hypothermic circulatory arrest for cardiovascular lesions: technical considerations and results

During a six-year period (1979 to 1984), the technique of hypothermic circulatory arrest was used to operate on 128 patients. Our technique included induction of hypothermia (20 degrees to 24 degrees C) by femoral artery cannulation for return of oxygenated blood, "open" aortic reconstruction, and brief periods of circulatory arrest (range, 5 to 31 minutes; mean, 13 minutes). Eighty patients had dissecting aneurysms of the ascending aorta (42 acute, 38 chronic), 28 had fusiform aortic arch aneurysms, and 13 had annulo-aortic ectasia. Seven had other procedures. Ages ranged from 14 to 79 years (mean, 54 years). Of the 113 patients (88%) who survived the operation and were discharged, 107 are currently alive and well. Only 15 of the 21 deaths occurred within 30 days of operation, and 5 (33%) were in severely hypotensive patients whose operations were begun during active resuscitation. Of the 80 patients admitted with ascending aortic or arch dissection, an in-hospital mortality of 7.5% was achieved. A marked reduction was observed in such complications as postoperative hemorrhage, renal failure, and pulmonary insufficiency with our current hypothermic perfusion methods. Moreover, none of the five neurological complications could be attributed to anoxic cerebral injury during the period of circulatory arrest. This experience indicates that moderate levels of hypothermia provide adequate cerebral protection for most cardiovascular procedures, and our results encourage continued use of this method.

Tracheal compression caused by aneurysms of the aortic arch. Implications for the anaesthetist

Two cases of severe tracheal compression caused by aortic arch aneurysm are reported. There was a marked similarity in the clinical presentation of these patients but the different outcomes of surgical resection appeared to be related to the content of the aneurysms. The first patient had a fixed obstruction due to solid clot, which proved irreversible; while the second had an aneurysm containing fluid blood. The anaesthetic management of this complication is discussed.