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Ann Thorac Surg 2006;81:1358-1364
© 2006 The Society of Thoracic Surgeons
a Department of Cardiothoracic and Respiratory Sciences, Second University of Naples, Naples, Italy
b Department of Cardiovascular Surgery and Transplant, V Monaldi Hospital, Naples, Italy
Accepted for publication November 29, 2005.
* Address correspondence to Dr Della Corte, Via A. Modigliani 64, 81031, Aversa CE, Italy (Email: aledellacorte{at}libero.it).
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Abstract |
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METHODS: Two hundred two arch procedures performed with moderate hypothermia (22° to 26°C) and antegrade cerebral perfusion (ACP) were the objects of retrospective investigation. Acute type A dissection was the indication in 164 patients, aortic aneurysm in 38. In 80 patients, during ACP, the thoracoabdominal aorta was perfused either in an antegrade fashion through proximal descending aorta endoluminal cannulation (in 62 dissections), or retrograde through femoral artery cannulation with proximal descending aorta endoluminal occlusion (in 18 aneurysms). Hospital mortality and morbidity rates were compared between the two treatments (group A: ACP only, 122 patients; group B: ACP plus TAP, 80 patients) and the underlying aortic disease (dissection/aneurysm) was stratified.
RESULTS: Cerebral perfusion (p = 0.008) and cardiopulmonary bypass times (p = 0.035) were significantly longer in group B. No complication related to the TAP technique was observed in group B. Overall hospital mortality was 12.9%, without significant difference between groups. No differences were found in terms of permanent neurological dysfunction between groups A (9.3%) and B (9.1%; p = 0.58). Group B patients showed lower rates of respiratory failure (18.2% versus 30.5% in group A; p = 0.038), shorter mechanical ventilation times (18.1 ± 26 hours versus 57.9 ± 70.1; p< 0.001) and lower incidence of acute renal failure (6.5% versus 18.6%; p = 0.012). Shorter intensive care and hospital stays were observed in group B (p = 0.02).
CONCLUSIONS: The adjunction of TAP to ACP was associated with lower rates of end-organ complications, even in more extensive and time-consuming procedures.
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Introduction |
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One possible strategy to protect end-organs during moderate hypothermic circulatory arrest (HCA) with cerebral perfusion may consist of concomitant perfusion of the thoracoabdominal aorta (TAP). We have recently introduced TAP in our aortic arch surgery practice, and in the present retrospective study, the early results of this strategy in patients undergoing aortic arch surgery were compared with the outcomes of HCA and selective cerebral perfusion, without TAP.
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Material and Methods |
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Technique: Group A
Anesthesia was induced with moderate doses of fentanyl, midazolam, and a long-acting muscle relaxant, and was maintained with isofluorane or sevofluorane in 100% oxygen and supplemental intravenous opioids. Thirty mg/kg intravenous steroid bolus was administered preoperatively for systemic inflammatory response limitation. After median sternotomy and systemic heparinization, cardiopulmonary bypass was instituted with a cannula for arterial return placed in the right femoral artery (117 cases) or in the right axillary artery (5 cases). A venous single-stage cannula was placed in the right atrium or (in patients presenting with cardiac tamponade) in the right femoral vein. The left ventricle was vented through the right superior pulmonary vein. Moderate systemic hypothermia (22° to 26°C of nasopharyngeal temperature) and myocardial protection with intermittent antegrade (directly into the coronary ostia) or retrograde cold crystalloid cardioplegia, or both, were employed in all cases. After cooling, systemic circulation was arrested, the aorta opened, and ACP performed according to the Kazui technique (117 cases) [11] or by mean of combined right axillary artery and left carotid artery direct cannulation (5 cases). Tape tourniquets encircling the vessel origin were used to keep the cerebral perfusion cannulas in place (an 18F cannula for the innominate artery and a 14F cannula for the left carotid artery) and to occlude the left subclavian artery. The cerebral perfusion tubing always came from the oxygenator with a separate roller pump. Cerebral flow was started at a rate of 10 mL · kg–1
· min–1 and adjusted according to the right radial pressure.
Technique: Group B
Preparation, cardiopulmonary bypass, and myocardial and cerebral protection methods were similar to those reported above. Also in group B, the ACP line always came from the blood cardioplegia outlet of the oxygenator through a separate roller pump. In patients with aortic dissection (group B1), the femoral artery was employed for arterial cannulation in 51 cases, the right axillary artery in 11. In case of femoral artery cannulation, the arterial line from the main roller pump was bifurcated: one branch served for arterial return in the femoral artery, the other was attached to an orotracheal cannula (generally size 8 or 9 can be directly connected to pump tubes) and proximally clamped during the cooling phase. Once the aorta was opened and the arch inspected, the orotracheal cannula, passed through the Dacron (C. R. Bard, Haverhill, Pennsylvania) graft, was inserted under direct vision into the distal arch (hemiarch replacements) or into the proximal tract of the descending aorta (total arch replacements), and its balloon cuff was filled with saline solution. During distal anastomosis and ACP by the Kazui technique, the branch of the arterial line connected to the femoral cannula was clamped, and a flow rate of 1 to 1.5 L/min was delivered into the descending aorta through the orotracheal cannula (Fig 1A). In case of axillary artery cannulation, after antegrade cooling, ACP was performed through axillary and left carotid arteries. The main arterial line was connected to the orotracheal cannula and used to deliver TAP (Fig 1B). In all group B1 patients, adequate distal aortic perfusion was assessed through intraoperative transesophageal echocardiography.
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Postoperative Management
Postoperative sedation was carried out with intravenous infusion of remifentanil. Awakening was allowed when the following targets were achieved: stable cardiocirculatory condition on continuous positive airways pressure ventilation, chest drainage less than 100 mL/h, and warm and cooperative patient. Patients were extubated when awake at spontaneous ventilation with assistance pressure less than 15 cmH2O and positive end expiratory pressure less than 5 cmH2O, with inspired fraction of oxygen (FiO2) 40% or less, if arterial oxygen pressure tension (PaO2) greater than 80 mm Hg, arterial carbon dioxide pressure tension (PaCO2) less than 50 mm Hg, tidal volume 10 mL/kg or greater, and respiratory rate 15 to 20 breaths per minute.
Statistical Analysis
Hospital mortality and morbidity, intensive care unit and hospital stay, and postoperative laboratory assessments (considering the peak values reached in the first postoperative week) were compared between the two study groups. Variable definitions are reported in the Appendix. Discrete variables are presented as counts and percentage whereas continuous variables as mean values ± SD. The 
2 test and Fisher's exact test were used for comparing categorical variables. Continuous variables were compared by using the t test or Wilcoxon's rank-sum test. Outcomes were also compared between subgroups homogeneous for underlying disease (A1 versus B1; A2 versus B2). Moreover, a subanalysis was performed including only patients operated on after 2002 (group A, n = 41; group B, n = 80), to attain concurrent patient populations and to correct for possible heterogeneity in perioperative management and surgical expertise due to different operation eras. A p value of 0.05 or less was considered statistically significant. The analysis was performed by means of the SPSS version 11.0.1 (SPSS, Chicago, Illinois) statistical program.
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Results |
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Postoperative Laboratory Assessments
Postoperative laboratory assessments showed peak serum alanine transaminase in group A 72.7 ± 34.9 versus 52.7 ± 28.6 U/L in group B (p<0.001); peak serum aspartate transaminase in group A 71.7 ± 38.9 versus 56.8 ± 33.6 U/L in group B (p = 0.007); peak lactic dehydrogenase in group A 1,112.5 ± 550.6 versus 690 ± 283.6 U/mL in group B (p< 0.001); peak serum creatinine in group A 2.06 ± 1.1 versus 1.6 ± 0.9 mg/dL in group B (p = 0.008); and peak blood urea nitrogen in group A 58.8 ± 26.3 versus 49.2 ± 20.1 mg/dL in group B (p = 0.009).
Clinical Outcomes
Overall hospital mortality was 12.9% (26 patients, 7 of whom died in the operative room: 4 in group A, 2 for massive hemorrhage and 2 for cardiac failure; and 3 in group B, for cardiac failure after massive preoperative myocardial infarction), which was slightly lower in group B but without significant difference (Table 3). Causes of postoperative death included multiorgan failure in 10 patients, low cardiac output in 3 patients, sepsis in 4, and pneumonia in 2.
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When concurrent populations were analyzed, the results were confirmed: hospital mortality with ACP was 12.2% versus 10% with ACP plus TAP (p = 0.47); respiratory failure was 34.2% versus 18.2% (p = 0.049); renal failure was 21.1% versus 6.5% (p = 0.025); and bleeding was 18.4% versus 20.8% (p = 0.49).
The analysis in subgroups of underlying disease (Table 4) evidenced that the overall advantage in terms of respiratory and renal complications observed with the ACP plus TAP protocol was due to the acute dissection subgroups. In particular, a reduction of more than 17% in the incidence of acute renal failure and of more than 12% of respiratory failure was observed in group B1 when compared with group A1. In the aneurysm subgroups (A2, B2), the low numbers probably affected the lack of significance for some differences.
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Comment |
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In case of total arch replacement in an anatomically unfavorable thorax, the tube can be removed soon after distal anastomosis, clamping the aortic prosthesis and continuing hypothermic TAP through a side branch of the prosthesis as usual. As regards the maneuver for establishing TAP, which is similar to those proposed by Klodell and colleagues [10] and Novitzky and colleagues [12], we did not observe any complication potentially attributable to endo-clamping the distal arch or proximal descending aorta. Even in case of dissection extending into the descending tract, endo-clamping the aorta allows for pressurization of the true lumen as a flow of 1 to 1.5 L/min is delivered by antegrade route. Retrograde TAP was favored when possible (that is, only in chronic aneurysms, in which the absence of reentries along the descending aorta had been assessed preoperatively by transesophageal echocardiography), to obtain a less cluttered operative field than with antegrade TAP.
Permanent neurologic dysfunction rates in the present series were similar in both study groups, and fell nearly at the upper limit of the range of incidences reported in recent series [3, 13–15]. This should be interpreted in view of our high rates of preoperative brain damage [16], and of cardiac tamponade at admission, which is an independent risk factor for poor neurologic outcome [14]. The 50% reduction in transient neurologic dysfunctions with TAP could be attributable to the preservation of excretory functions, reducing the contribution of metabolic disorders among the possible causes of neurologic disturbances.
In the most recently published aortic arch surgery series, excluding those on deep HCA without cerebral perfusion, renal insufficiency has been reported to occur in 3.7% to 12% of cases [7, 8], respiratory failure in 11% to 50% [8, 13], and bleeding in 3.6% to 36% [2, 17]. In particular, the lung seems to be electively susceptible to the injuries caused by circulatory arrest and ischemia-reperfusion [18, 19], while hypothermia per se seems not to cause a significant increase in respiratory failure [4]. However, the lower the temperature, the longer the extracorporeal circulation time needed for rewarming and, therefore, the more severe the systemic inflammatory response [19–21]. The perfusion of the bronchial arteries through the descending aorta and the intercostal arteries [22, 23], the expected limitation of systemic inflammatory reaction by prevention of the ischemia-reperfusion phenomenon in the lower body [4, 20], and the lower number of transient neurologic disorders, a possible cause of ventilatory dysfunction or airway clearance impairment, could all possibly account for the better lung function observed in the TAP group.
Less is known about the mechanisms of renal injury in moderate HCA, but endothelial damage and inflammatory response are postulated to be main pathogenetic factors as well [4, 19]. Cooper and coworkers [24] experimentally demonstrated that circulatory arrest is associated with endothelial dysfunction also in large-caliber renal arteries. Microvascular thromboses and other hematologic changes induced by stasis could account for an important part of the damage to end-organs observed with HCA [25], and maintaining blood flow in the descending aorta may limit these mechanisms of injury.
Other arch surgery series have reported lower bleeding rates than ours [8, 9, 26]. However, bleeding in those series was defined as return to the operative room, and generally indication criteria were not acknowledged. In the present study, more than 150 mL drainage in an hour in the first 6 postoperative hours was defined as a bleeding complication, regardless of whether resternotomy was performed or medical treatment was sufficient to obtain hemostasis. A coagulopathy has been shown to accompany aortic dissection, as a consequence of blood exposure to interrupted intravascular surfaces [25, 27]; likely, many cases of postoperative hemorrhage are not related to surgically amenable bleeding points. It should be stressed that in the present series a higher proportion of patients with acute dissection (81.2%) was included, compared with other series. Indeed, series in whom more than 25% of patients had acute aortic dissection [3, 6, 28] reported rates of reoperation for bleeding between 12% and 15%; and in one series selecting only patients with dissection, this incidence reached 36% [2].
The main limitation of the present study is represented by its retrospective design. This has prevented us from documenting the mechanisms underlying the observed reduction in renal and respiratory complications through deeper investigations (such as evaluation of serum levels of inflammatory response molecules, for example, interleukins or tumor necrosis factor) that are not routinely performed in our practice. Moreover, no investigation of the most suitable flow rate for TAP was attempted.
In conclusion, continuing body perfusion during ACP in moderate hypothermia was, in our experience, a safe procedure, and it was associated with significantly lower rates of postoperative respiratory dysfunction and renal failure. A prospective trial, designed to assess the impact of TAP on systemic inflammatory response and organ metabolism, is necessary to confirm the superiority of this strategy over the standard method.
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Appendix |
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Permanent neurologic dysfunction
Occurrence of one or more of the following events: stroke, coma, new focal or multiple brain lesion detected by means of brain computed tomography scan.
Temporary neurological dysfunction
Postoperative confusion, lethargy, agitation or delirium, or both, without focal lesions at brain computed tomography scan and with complete resolution of symptoms before discharge.
Respiratory failure
Need for intubation and ventilatory support for more than 72 hours overall (including patients needing further ventilatory support after initial extubation).
Acute renal failure
Need for hemodialysis or continuous venovenous hemofiltration (indicated for postoperative serum creatinine levels greater than 1.5 mg/dL with oliguria or anuria).
Bleeding
Either total blood losses in the first 6 postoperative hours exceeding 900 mL or resternotomy for hemostasis, whenever performed.
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References |
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