Ann Thorac Surg 2003;76:1485-1489
© 2003 The Society of Thoracic Surgeons
a Division of Cardiovascular Surgery, Funabashi Municipal Medical Center, Chiba, Japan
Accepted for publication April 18, 2003.
* Address reprint requests to Dr Takahara, Division of Cardiovascular Surgery, Funabashi Municipal Medical Center, 1-21-1 Kanasugi Funabashi, Chiba, 273-8588 Japan.
BACKGROUND: In aortic arch grafting, antegrade cerebral perfusion prolongs the safe time of arch exclusion. However, there are the problems of cerebral embolism and distribution of the cerebral perfusion. We describe and analyze mortality and cerebral complications in patients undergoing total arch grafting using our refined technique.
METHODS: Between June 1994 and March 2002, 100 consecutive patients underwent total arch grafting through median sternotomy. There were 49 atherosclerotic aneurysms and 51 aortic dissections. Fifty-four patients were operated on an emergency basis because of rupture or acute type A dissection. We conducted total arch grafting using hypothermic antegrade cerebral perfusion from every cervical vessel. Carbon dioxide gas was added to the cerebral perfusion in order to inhibit the increase in the cerebral vascular resistance during hypothermic cerebral perfusion.
RESULTS: Hospital mortality was 4%. The causes of death were dysarrhythmia (n = 1), mesenteric necrosis (n = 1), and preoperative cardiac arrest (n = 2). On univariate analysis, preoperative shock and concomitant cardiac procedures were risk factors for hospital death. The rate of postoperative neurologic damage was 5%. Two patients suffered from cerebral infarction. Temporary neurologic dysfunction occurred in 3 patients. On univariate analysis, emergency surgery was a risk factor for postoperative neurologic damage. On multivariate analysis, there was no significant independent predictor of hospital mortality and neurologic damage. Actuarial survival at 96 months was 66.4 ± 9.1%, and freedom from aortic accidents (reoperation, rupture, and cholesterol embolism) was 74.9 ± 7.9%.
CONCLUSIONS: The early- and long-term results of total arch grafting using integrated antegrade cerebral perfusion were found to be satisfactory.
In surgical repair of transverse aortic arch aneurysms, cerebral injury is one of the most feared complications and a major cause of poor outcome. Circulatory arrest with deep hypothermia, retrograde cerebral perfusion, and antegrade selective cerebral perfusion have been introduced as a mean of protecting the cerebral tissue from ischemic damage during total aortic arch grafting. However, there is a limited safe time in the method of circulatory arrest with deep hypothermia and retrograde cerebral perfusion. Although antegrade cerebral perfusion prolongs the safe time of arch exclusion, there remain the problems of cerebral embolism and distribution of cerebral perfusion .
Therefore, we use a refined technique of antegrade selective cerebral perfusion. Our cerebral perfusion is conducted from every cervical branch. Carbon dioxide gas is added to cerebral perfusion in order to inhibit the increase in the cerebral vascular resistance during hypothermic cerebral perfusion . The most common approach to an arch aneurysm is median sternotomy. Left thoracotomy is one of the causes of operative pulmonary injury. In the patients where the distal side of whose aneurysm was above the eighth thoracic vertebra, we conducted total aortic arch grafting through only median sternotomy using integrated antegrade selective cerebral perfusion. We herein describe the surgical results and the independent predictors of hospital mortality and neurologic morbidity in 100 consecutive patients.
Material and methods
From June 1994 to March 2002, 100 consecutive patients in our hospital underwent grafting of the total aortic arch through median sternotomy only. The mean age was 64.6 ± 11.2 years. Sixty-six were men and 34 were women. Forty-nine patients suffered from atherosclerotic aneurysms and 51 patients from aortic dissections. Fifty-four patients were operated on an emergency basis because of rupture or acute type A dissection. In terms of preoperative complications, 84 patients had hypertension, 10 patients had diabetes mellitus, 7 patients had old myocardial infarction, 19 patients had previous cerebral vascular accident, 10 patients had chronic renal failure, and 25 patients were in states of shock or preshock. Preshock was defined as a loss of consciousness; shock was defined as a loss of consciousness with systolic blood pressure less than 90 mm Hg. Four patients had undergone previous cardiac or thoracic aortic operations: coronary artery bypass grafting (CABG) (n = 1), descending aortic grafting (n = 1), and ascending aortic grafting (n = 2). Eighteen patients underwent concomitant cardiac procedures: CABG (n = 7), modified Bentall's operation (n = 8), mitral valve replacement (MVR) (n = 1), aortic valve replacement (AVR) (n = 1), and CABG + AVR (n = 1).
All operations were performed under hypothermic selective cerebral perfusion (20°C). Anesthesia was induced with midazolam 10 mg, fentanyl 0.05 to 0.1 mg, and vecuronium 10 mg, and maintained with 1.0% to 2.5% isoflurane, 66% N2O, and fentanyl. Isoflurane (1.0%) and morphine 10 mg were administered from the extracorporeal circulation system.
To expose the aortic arch, a median sternotomy only was made in all patients. In patients with atherosclerotic aneurysms and chronic aortic dissection, the arterial cannulation of the systemic circulation was performed to the ascending aorta or to both axillary arteries. The arterial cannulations of the selective cerebral perfusion were performed to the right brachio-cephalic artery, the left carotid artery, and the left subclavian artery. In patients with acute aortic dissection, the arterial cannulation of the systemic circulation was performed to the femoral artery, and the patients were cooled down. In patients whose dissection extended to the aortic arch branches, arterial cannulas were inserted directly through the aortic arch lumen internally under hypothermic circulatory arrest.
The extracorporeal circulation system was set up with venous reservoirs, roller-pumpings, membranous oxy-generators, and arterial filters. The priming drugs were 20% mannital 300 mL, 8.4% NaHCO3 100 mL, 6% hydroxyethylated starch 500 mL, and lactate Ringer 1200 mL. The total blood flow rate of the selective cerebral perfusion was 10 mL/Kg/min. We used two roller-pumping units for the cerebral perfusion and systemic perfusion, and 5% carbon dioxide gas was added to the cerebral circulation. The flow rate of the 5% carbon dioxide gas was controlled to maintain a carbon dioxide tension of 50 to 55 mm Hg (uncorrected for body temperature) in the cerebral circulation .
The aortic arch was resected, and the distal aortic anastomosis was performed using the open aortic technique when the distal side of the aneurysm was above the sixth thoracic vertebra. In 1 patient, the distal side of whose aneurysm was below the sixth thoracic vertebra, we conducted transmediastinal replacement . An aortic graft with four branches was used in all patients. One branch was used for the cannulation of the systemic circulation in the rewarming stage. The ascending aortic anastomosis and aortic arch reconstruction using the other three graft branches were performed during rewarming.
The continuous data are expressed as the mean ± SD. All statistical analyses were completed using the SPSS Base 8.0J software package (SPSS Inc, Chicago, IL). Univariate analyses appeared to be from 2. The continuous variables were analyzed by the logistic regression test. Multivariate analysis was performed by a stepwise multivariable logistic regression model. Pump time, cerebral perfusion time, and every other factor listed in Table 1 were entered in this model. A p value of 0.05 or less was considered statistically significant. Follow-up data were obtained from clinical visits in 98% of the patients, and the mean of follow-up time was 30.5 ± 25.4 months. The actuarial curves were constructed using the standard nonparametric Kaplan-Meier method, and all follow-up data were expressed as mean ± standard errors. We evaluated actuarial survival rates and freedom rates from aortic accidents. The definition of aortic accidents was rupture of the aortic aneurysm, reoperation of the aorta, or cholesterol embolism.
In the 100 patients in this study, the operative time, cardiopulmonary bypass time, selective cerebral perfusion time, cardiac ischemic time, systemic circulatory arrest time, and perioperative blood loss are shown in Table 2.
Regarding postoperative neurologic damage, 2 patients suffered from cerebral infarction. The diagnosis of cerebral infarction was based on neurologic signs with positive tomographic scanning. However, they made a full recovery after 3 months. Three patients suffered from temporary neulological dysfunction, defined as postoperative agitation, lethargy, confusion, or delirium with negative tomographic scanning, and and all had complete resolution before discharge. On univariate analysis, an emergency surgery was found to be a risk factor for postoperative neurologic damage (Table 1). On multivariate analysis, there was no significant independent predictor of hospital mortality and postoperative neurologic damage.
In the postoperative course, there were four cases of low output syndrome requiring mechanical cardiac support (ventricular assist device, two; intraaortic balloon pumping, two) and seven cases of renal failure requiring dialysis. The mean of postoperative mechanical ventilation time was 39.2 ± 72 hours. The mean of postoperative intensive care unit stay was 4.0 ± 5.5 days. The mean of postoperative hospital stay was 29.8 ± 13.6 days.
In the long-term follow-up, there were 16 late deaths. The causes of the late deaths were five cases of pneumonia, three cases of aortic rupture, three cases of cerebral vascular accident, one case of acute myocardial infarction, one case of renal failure, one case of heart failure, one case of cancer, and one case of sudden death. The actuarial survival rate at 96 months was 66.4 ± 9.1% (Fig 1). There were 12 aortic events in the follow-up time. Four patients suffered from aortic rupture. Six patients underwent reaortic surgery. All cases of reoperation were aortic dissection. Two patients suffered from cholesterol embolism. The actuarial freedom rates from aortic events at 96 months were 74.9 ± 7.9% (Fig 2).
Recent technical improvements of cerebral protection and arch grafting have reduced the mortality and the morbidity associated with aortic arch surgery. However, strokes resulting from either global ischemia during interruption of normal cerebral perfusion or focal embolic episode are a frequent cause of poor outcomes. Hypothermic circulatory arrest and retrograde cerebral perfusion have been introduced as a means of protecting the brain from global ischemia. However, there is a limited safe time of circulatory arrest of no longer than 40 to 65 minutes [4, 5]. Antegrade cerebral perfusion has no limited safe time. Kazui and associates have reported that there was no significant correlation between the selective cerebral perfusion time and temporary and permanent neurologic dysfunction . We conducted arch grafting using hypothermic antegrade cerebral perfusion from all of the cervical vessels. There was no significant correlation between the selective cerebral perfusion time and postoperative neurologic damage.
Atherosclerotic aortic debris and thrombus are major cause of cerebral embolism during aortic surgery [1, 7, 8]. In the patients with atherosclerotic aneurysm and chronic dissection, we did not use the femoral cannulation for systemic perfusion. We conducted systemic perfusion from the ascending aorta. If the ascending aorta had an aneurysm, dissection, or severe atherosclerotic damage, we conducted systemic perfusion from both axillary arteries. In 100 consecutive patients, 2 patients suffered from cerebral infarction. They were operated on for acute dissection, and femoral cannulation for systemic perfusion was used.
Antegrade cerebral perfusion has the disadvantage of requiring manipulation of cerebral vessels with the risk of dislodging atherosclerotic debris. In the majority of patients, the orifices of the cerebral vessels were diseased, showing aneurysmal dilatation, atherosclerotic stenosis, or ulcerative debris [6, 9]. We performed the cerebral arterial cannulation and anastomosis at a distal, relatively normal arterial segment, and the proximal diseased parts of the cerebral vessels were resected.
Temporary neurologic dysfunction was defined as postoperative confusion, agitation, delirium, prolonged obtundation, or Parkinsonism without localizing neurologic signs by Ergin and associates . It is subtle but diffuse cerebral injury undetectable by conventional imaging techniques, and is directly related to inadequate brain protection. Deep hypothermic circulatory arrest of 25 minutes or more was associated with memory and fine motor deficits [1, 11]. Okita and associates have reported that the incidence of transient brain dysfunction was significantly higher in the retrograde cerebral perfusion group than in the antegrade perfusion group .
We use the refined technique of antegrade selective cerebral perfusion. Our cerebral perfusion is conducted from every cervical branch. Carbon dioxide gas is added to cerebral perfusion in order to inhibit the increase in the cerebral vascular resistance during hypothermic cerebral perfusion. The rates of postoperative temporary neurologic dysfunction and stroke were 3% and 2%, respectively. In previous reports using antegrade cerebral perfusion, temporary neurologic dysfunction was 2% to 13.3%, and stroke was 2% to 6.6% [6, 9, 1214]. In previous reports using hypothermic circulatory arrest and retrograde cerebral perfusion, temporary neurologic dysfunction was 3.3% to 33.3%, and stroke was 1.4% to 11% [7, 11, 12, 15, 1619]. Prough and associates have reported that the response of the cerebral circulation to changes in carbon dioxide tension was well maintained during hypothermic cardiopulmonary bypass . The addition of carbon dioxide gas might reduce the flow to poorly perfused regions. We used 50 to 55 mm Hg of carbon dioxide tension uncorrected for body temperature. Recently, alpha stat pH management has used in some reports [17, 21].
In conclusion, aortic arch grafting using integrated hypothermic antegrade cerebral perfusion is safe, effective, and consistent with low rates of stroke and postoperative temporary neurologic dysfunction. There was no significant correlation between selective cerebral perfusion time and postoperative neurologic damage. On multivariate analysis, there was found to be no significant independent predictor of hospital death and postoperative neurologic damage.
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