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Antegrade selective cerebral perfusion through the right axillary artery has proved to be a safe and effective method for cerebral protection in aortic surgery. In this study, we prospectively evaluated the techniques of direct right axillary artery cannulation (Group 1) and right axillary artery side-graft cannulation (Group 2), investigated cannulationrelated complications, and determined the hemodynamic advantages and disadvantages of both cannulation techniques.
Sixty-eight patients underwent surgery from April 2001 through August 2004 with the diagnoses of ascending and aortic arch aneurysms (10 patients), type A aortic dissection (56 patients), and aortic pseudoaneurysm (2 patients). There were 22 patients in Group 1 (33.4%) and 46 patients in Group 2 (67.6%).
The antegrade selective cerebral perfusion flow was 500 to 700 mL/min in Group 1, whereas in Group 2 the flow was adjusted in accordance with the mean right radial arterial pressure, which was 50 mmHg. There was no significant difference between the groups in antegrade selective cerebral perfusion times, but the transient neurologic dysfunction rate (4 of 22 patients in Group 1 vs 1 of 42 in Group 2) was significantly lower in Group 2 (P =0.035). In Group 1, axillary artery dissection occurred in 2 patients (9%), and postoperative arm ischemia occurred in 1 patient (4.5%). These complications were not seen in Group 2 (P =0.031).
The side-graft cannulation technique may be more acceptable because of its lower local-complication rate and because it provides pressure-controlled cerebral perfusion.
The ascending aorta is the most common arterial cannulation site for cardiopulmonary bypass (CPB). In some circumstances, such as the presence of ascending aortic aneurysms, dissections, or atherosclerosis, cannulation of the ascending aorta can be dangerous. In these situations, alternative cannulation sites such as the femoral artery, axillary artery, brachial artery, brachiocephalic artery, or a combination of these arterial sites may be preferred by the surgeon. However, the femoral artery should not be cannulated in the event of thoracoabdominal aortic or iliofemoral vascular disease, or of any vascular condition associated with a risk of retrograde embolization of thrombus or atherosclerotic débris.1–7 In 1995, Sabik and colleagues1 popularized the technique of using the right subclavian/axillary artery for arterial inflow for complex cardiac operations.
Antegrade selective cerebral perfusion (ASCP) through the right axillary artery has proved to be a safe and effective method for cerebral protection in aortic surgery. The right axillary artery is now preferred for complex ascending aortic operations and is indicated for use in wider applications.
In this study, we prospectively evaluated direct right axillary cannulation and right axillary side-graft cannulation, investigated cannulation-related complications, and determined the hemodynamic advantages and disadvantages of both cannulation techniques.
The study population included 68 patients who underwent surgery from April 2001 through August 2004. The mean age of the patients was 52 ± 10 years (range, 23–73 years). Right axillary artery cannulation was used in all patients. The patients were evaluated as 2 independent groups. The first 22 patients (32.4%) were cannulated directly through the right axillary artery (Group 1), whereas the remaining 46 patients (67.6%), beginning in May 2002, were cannulated through an artificial graft implanted in the right axillary artery end to side (Group 2). There was no overlap in time between the 2 techniques. Visceral malperfusion was diagnosed when the patient presented with abdominal pain, tenderness, and absence of peristalsis; peripheral malperfusion was diagnosed when there was a pulseless extremity with ischemic pain and an absence of pulses or a lack of flow into the extremity as determined by handheld Doppler examination (Multi Dopplex II, Huntleigh Healthcare; Luton, Bedfordshire, UK); spinal malperfusion was diagnosed when the patient had paraparesis; and cerebral malperfusion was diagnosed when the patient had syncope and confusion with agitation. The clinical characteristics of the groups are seen in Table I. The data were collected prospectively from preoperative, perioperative, and postoperative patient databases of our hospital, with the permission of our Internal Review Board.
The indications for surgery are shown in Table I. The groups were compared in accordance with cannulation-related complications, postoperative neurologic outcomes, intensive care unit length of stay, length of hospitalization, total blood transfusion amount, fresh frozen plasma transfusion amount, and death. The postoperative neurologic dysfunction might be permanent (stroke or coma) or transient, with complete resolution before discharge: confusion, agitation, delirium, prolonged unconsciousness, double vision, delayed awakening (more than 24 hours), or transient parkinsonism accompanied by negative brain scan results as determined by computed tomography.8,9
All operations were performed with the patient under general anesthesia. Arterial lines were routinely placed in both radial arteries for pressure monitoring. A right internal jugular central venous line was preferred to a subclavian, because a subclavian line could preclude axillary artery cannulation. Routine preoperative upper-extremity arterial examination was performed on every patient, to avoid malperfusion. Except in the presence of acute aortic dissections, the brachiocephalic arteries were preoperatively evaluated with Doppler ultrasonography for the presence of any arterial occlusive disease, again in order to avoid malperfusion.
The axillary artery was exposed through an incision that was made inferior and parallel to the lateral two thirds of the clavicle. The pectoralis major muscle was divided in the direction of its fibers. The clavipectoral fascia was incised and the pectoralis minor muscle was exposed. This muscle was divided and retracted laterally. The axillary artery was seen superior to the axillary vein. The proximal and distal parts of the axillary artery were controlled with Silastic tape. After heparin administration, the axillary artery, in Group 1, was cannulated with a 21F cannula through a transverse arteriotomy. In Group 2, an 8-mm Dacron vascular graft was anastomosed to the axillary artery in an end-to-side fashion with a 6–0 polypropylene suture; after anastomosis, the graft was cannulated with a 21F cannula.
Venous cannulation was performed with a 2-stage right atrial cannula. A retrograde cardioplegia cannula was inserted into the coronary sinus. The brachiocephalic and left carotid arteries were prepared before CPB was started. An 18F cannula was inserted into the right superior pulmonary vein in order to vent the left heart.
All operations were performed under moderate hypothermia, with a rectal temperature of 25 to 28 °C. The rectal temperature was decreased to 25 °C for longer ASCP times (in anticipation of aortic arch operations, for example), whereas it was stabilized at 28 °C for shorter ASCP times. Radial artery pressures in both arms were checked at the beginning of CPB, in order to avoid malperfusion. After cross-clamping the ascending aorta, we accomplished cardiac arrest with antegrade infusion of isothermic hyperkalemic blood cardioplegic solution. Arrest was maintained by a continuous retrograde infusion of solution. An open distal anastomosis was performed in all patients. Continuous ASCP, accomplished by clamping the brachiocephalic and left carotid arteries proximally, was done during distal reconstruction. The ASCP flow was stabilized to 500 to 700 mL/min (more precisely, 8–10 mL/kg/min) in Group 1. However, in Group 2, the ASCP flow was regulated so that right radial artery pressure was 50 to 60 mmHg.
When the procedure was completed, the axillary artery in Group 1 was repaired before protamine administration. In Group 2, the axillary artery graft was clamped, cut, and oversewn with 5–0 polypropylene suture after the administration of protamine. The operative procedures are listed in Table II.
Statistical Analysis. Statistical analysis was done with the SPSS version 10.0 statistical software program (SPSS Inc.; Chicago, Ill). Continuous variables were expressed as the mean ± 1 SD, and comparison between the groups was done by the Mann-Whitney U test. The difference between the groups according to neurologic outcome was analyzed by Fisher's exact test. Statistical significance was found in P values of less than 0.05. Transient neurologic dysfunction was considered to indicate the presence of a neurologic event.
The combined hospital mortality rate for both groups was 13.2%. The mortality rate of Group 1 was 18.2%, due to 4 deaths (low cardiac output and arrhythmia in 2 patients, gastrointestinal system ischemia in 1, and disseminated intravascular coagulation in 1). The mortality rate of Group 2 was 10.9%, due to 5 deaths (low cardiac output in 2 patients, gastrointestinal system ischemia in 2, and respiratory insufficiency and hypoxia in 1).
More cannulation-related complications occurred in Group 1. No brachial plexus injury was seen in either group. However, in Group 1, axillary artery dissection (necessitating aortobrachial bypass) was seen in 2 patients (9%), and postoperative arm ischemia was seen in 1 patient (4.5%). These complications were not seen in Group 2 (P =0.031).
The mean ASCP flow in Group 1 was 543 ± 58 mL/min, and in Group 2 it was 658 ± 80 mL/min (P <0.001). This difference may have been due to right arm perfusion. The body temperature in both groups was 25 to 28 °C during ASCP. There was no significant difference between the groups in regard to length of ASCP (Group 1, 36.9 ± 18.6 min; Group 2, 38.6 ± 14.5 min); however, the neurologic dysfunction rate was significantly lower in Group 2 (4 of 22 patients in Group 1: postoperative confusion, agitation, and delirium in 3 patients, and awakening delayed more than 24 hours in 1 patient; 1 of 46 patients in Group 2: awakening delayed more than 24 hours; P =0.035). No permanent neurologic dysfunction occurred (Table III).
Femoral artery cannulation is still widely used in aortic surgery. However, it is associated with lower extremity ischemia, compartment syndrome, wound complications, propagation of retrograde dissection, dislodgment and retrograde embolization of luminal débris, and end-organ ischemia caused by malperfusion.5 Because axillary artery cannulation can prevent many of these complications, its wide adoption for arterial inflow has begun.1–5 The axillary artery is generally free from atherosclerosis, in comparison with the femoral arteries,8 and the axillary artery is rarely affected by dissection.9 As in the case of the femoral artery, surgical exploration of the axillary is easy to perform. In surgery for aortic dissection, axillary artery cannulation provides antegrade perfusion of the true lumen at the beginning of CPB and again after the distal anastomosis. It is not necessary to cannulate the ascending aortic graft after completion of the distal anastomosis. The most important advantage of right axillary artery cannulation is that it provides antegrade perfusion of the brain during open distal aortic reconstruction.
Axillary artery cannulation can also be applied in distal aortic arch aneurysms, Stanford type B aortic dissections, or complex thoracic aortic aneurysms, by placing the patient in the right lateral semidecubitus position.10
Some authors have described the use of deep hypothermia and retrograde cerebral perfusion in cases in which the circulatory arrest period exceeds 30 minutes, even in cases in which they have cannulated the axillary artery.1–3,5,11 In our study, ASCP at moderate hypothermia (25–28 °C) was used during open distal aortic reconstruction in the period of circulatory arrest.
Svensson11 reported that, because of poor protection of visceral organs like the liver, moderate hypothermia increased the risk of bleeding, compared with deep hypothermia. However, Di Eusanio and coworkers12 reported that ASCP provides safe circulatory arrest for as long as 90 minutes under 25 °C nasopharyngeal temperature, which can reduce the systemic complications of profound hypothermia, such as coagulation.
Neri and colleagues2 reported that they preferred left axillary artery cannulation, because the left subclavian artery has its origin separate and downstream from the carotid artery. They suggested that the brachiocephalic trunk was often obstructed by expansion of the false lumen in type A aortic dissection.2 If this theoretically possible complication were encountered, the pressure difference between the 2 radial arteries would encourage the surgeon, at the outset of CPB, to cannulate the femoral artery rather than the radial artery, in order to avoid malperfusion. However, we ourselves did not encounter any complication related to the encroachment of the aortic false lumen upon the brachiocephalic artery.3
Tasdemir and associates,13 in their study involving 104 patients, found only 1 cannulation-related complication involving upper brachial artery cannulation, but ischemia of the right upper extremity may hypothetically occur during prolonged CPB.13 Tasdemir's group used an 18F cannula for cannulation of the brachial artery. However, an 18F cannula may not provide enough arterial inflow for patients with high body-surface areas. In such an instance, either a different arterial inflow site (such as the femoral artery) should be chosen, or the diameter of the cannula should be increased. In addition, it may be more dangerous to cannulate the brachial artery than the axillary artery, because the brachial is more vulnerable to injury.
Right axillary artery side-graft cannulation has many advantages in bi-hemispheric perfusion of the brain, compared with direct right axillary artery cannulation. The brain is supplied by 2 internal carotid arteries and 2 vertebral arteries. The 4 arteries anastomose on the inferior surface of the brain and form the circle of Willis. The anterior communicating artery links the 2 anterior cerebral arteries to each other. The basilar artery divides into the 2 posterior cerebral arteries, both of which are linked to the internal carotid arteries by 2 posterior communicating arteries.14 Under-perfusion of the contralateral cerebral hemisphere is hypothetically difficult in right axillary artery side-graft cannulation unless there is an anomaly in which the 3 communicating arteries are absent or unless the cerebral arteries are atherosclerotic. However, when the right axillary artery is directly cannulated, right vertebral artery malperfusion may occur, and this will increase the risk of under-perfusion of the contralateral hemisphere.3 Another point is that the left carotid artery is clamped during ASCP, which is important for the maintenance of adequate pressure in the circle of Willis.
The side-graft cannulation technique affords the possibility of indirect pressure monitoring of cerebral perfusion. The ASCP pressure is monitored by right radial artery catheterization. Side-graft cannulation avoids the undesired high-pressure oscillations that can occur as a consequence of constant antegrade selective cerebral flow during direct axillary artery cannulation. Svensson reported that higher ASCP pressure was associated with greater risk of stroke and neurocognitive deficit.10 In our study, transient neurologic dysfunction was significantly higher in the direct axillary artery cannulation group. This result might have been due to high antegrade cerebral flow pressure. However, more detailed studies should be done in order to verify this.
Tasdemir and associates13 also used continuous ASCP at moderate hypothermia with an arterial flow of 500 to 600 mL/min (8–10 mL/kg/min) and found a 1.9% total neurologic incidence. In our study, the neurologic dysfunction rate (2.1%) was similar to Tasdemir's in the side-graft cannulation group. We are of the opinion that continuous antegrade perfusion of the brain will avoid the necessity of deep hypothermia and retrograde cerebral perfusion. In this manner, the harmful effects of the hypothermia can be avoided, and the time needed for cooling and rewarming will be shortened.
Side-graft cannulation has other advantages over direct axillary artery cannulation. Sabik's group15 compared direct right axillary artery cannulation with sidegraft cannulation in regard to cannulation-related morbidity. They evaluated 392 patients who underwent 399 axillary artery cannulations. The axillary artery was cannulated directly in 212 (54%) instances and with a side graft in 187 (48%). Side-graft cannulation significantly reduced brachial plexus injury, axillary artery injury, arm ischemia, and aortic dissection. They concluded that cannulation with a side graft was associated with less cannulation-related morbidity than was direct cannulation, and they recommended the routine use of a side graft whenever axillary artery cannulation was indicated.15 The results of the present study also point to this recommendation.
Antegrade selective cerebral perfusion can be indirectly measured and regulated when side-graft cannulation is performed.
This is an observational study and not a randomized study. There seems to have been a temporal effect upon outcome. The first 22 patients, in Group 1, underwent surgery first, and the same surgical team carried out all of the operations—so there may have been a learning curve. However, the ASCP times of the groups were statistically similar, which militates against the possibility of a training effect on outcomes.
Address for reprints: Bilgin Emrecan, MD, 226 sok. 17/10 Hatay, Izmir 35280, Turkey. E-mail: moc.oohay@nacermeniglib