Axillary artery perfusion in acute aortic dissection type a repair for a better cerebral protection

 Introduction
Acute aortic dissection type A, still has a high morbidity and mortality in spite of better cerebral and cardiac protection. One major reason of this complications and fatal evolution is cerebral and visceral perioperative malperfusion due to presence of false lumen and embolic events (11).
Routinely, arterial cannulation for CPB insta-llation in this emergency operation has been performed through femoral vessels. However, a necropsy study of patients died with acute aortic dissection showed that a large percentage of patients were at high risk for this malperfusion syndrome, if the femoral artery should be used for perfusion (21). Also, femoral artery cannulation carries with another local complication like; lower extremity ischemia, neurologic injury, wound infection, lymphoragy,  dislogement and retrograde embolization of thrombosis or luminal debris, cerebral and visceral malperfusion and several time is affected by dissection or atherosclerosis.
Using of axillary artery site for arterial inflow of CPB, was suggested in this type of aortic arch surgical repair in 1963 by DeBakey, Cooley, Crawford but regained interest only in the last years.
To avoid this malperfusion syndrome, we have started in 2000, using the axillary artery cannulation in emergency operation to repair ascending aorta and aortic arch in total circulatory arrest, deep hypothermia and retrograde cerebral perfusion. We cannulated the right axillary artery in 14 patients, with acute aortic dissection type A (67 patients), providing antegrade flow and femoral artery in 52 patients, giving retrograde flow of CPB. The variables of this two groups, hospital mortality, cerebral troke, renal failure, sepsis, bleeding, local cannulation complication, MSOF, Marfan syndrome, hypertension were statistical analised. This study review and compare in our experience this two techniques of arterial cannulation.

Material and Methods
We started in January 2000, to apply cannulation achieving full ardiopulmonary bypass (CPB) in aortic dissection type A repair. Between January 2000 and September 2001,  67 emergency patients underwent aortic repair for acute aortic dissection type A, using deep hypothermia and circulatory arrest. Median age of patients was 56 years (range, 18 to 85 years); 47 were male and 20 female. Axillary artery cannulation were performed in 14 patients (21%) and the traditional way, femoral artery in 52 patients (77%) and cannulation of ascending aorta 1 (2%). In 5 patients we have used a side graft sutured to the axillary artery. All the patients were operated in emergency, total circulatory arrest and deep hypothermia. Preoperative characteristics for the both groups are described in Table 1.

Axillary artery dissection and CPB installation
The right axillary artery is dissected for cannulation through an 6 - 8 cm incision under and parallel in lateral 1/3 of the clavicle. The pectorals majors fibers are spreaded in their direction and the clavipectoral fascia is incised, showing the pectorals minor muscle. This is divided or retracted and the vessels, artery and axillary vein are identified (artery by palpation of the pulse). Proximal and distal axillary artery is dissected and encircled with a vessel loop. We paid attention for carefully hemostasis, but don’t use too much the cauthery to avoid the brachial plexus injury. Systemic heparinization is given. Median sternotomy is performed in a standard way.
Pericardium is opened and the great vessels, ascending aorta and aortic arch are inspected. In this time cannulation of axillary artery is made using two, distal an proximal 120º femoral clamp and a transverse arteriotomy. A flexible arterial cannula 20 - 22 F, could be accepted by this vessel, secured with a tourniquet over proximal part and keeping in place the distal vascular clamp
(fig. 1). This technique was used in majority of cases and a lateral side prosthesis Vascutek 8 mm diameter was swing in case of small axillary artery or in situation when you like to monitored the cerebral perfusion in antegrade delivery by radial artery line (5 patients). At the decannulation time we used a 6/0 Prolene, running or interrupted suture to close the arteriotomy. Venous cannulation is performed using a single double-stage cannula inserted in the right atrium. When we use the retrograde cerebral perfusion during total circulatory arrest via superior cava venae, this is dissected at this time and encircled with a vessel loop (the same sinus venous cardioplegia with self balloon inflation is used for cerebral perfusion delivery). For the cardiac protection we used a retrograde blood cardioplegia through the venous sinus. Slice is used over heart.
Vent is placed in apex or through the superior right pulmonary vein. In this time CPB is started with a flow 2,0 - 2,4 L/min and cooling up to deep hypothermia (esophagian temperature 18ºC) is achieved. After aortic arch repair, CPB is resumed and rewarming is start using the same arterial inflow line of axillary artery. Special monitoring during the circulatory arrest were; jugular venous blood saturation (should be over 95%, when circulatory arrest begin), EEG, blood gas analysis, tympanic temperature and perfusion pressure of cerebroplegia. Very effectively is continuous using of transesophageal ecocardio-graphy intraoperative to assess aortic valve status, left ventricle contractility, entry point and retry, false and true lumen before and after repair.
Statistical analysis was used with MS Excel for Windows and SPSS for Windows. Univariate variables were calculated using the Mann-Whitney test. A p value less than 0,05 was assumed to be statistically significant.

Results
The overall 30-days mortality for 67 patients, all of them operated in emergency, deep hypothermia and total circulatory arrest was 12,5%, for the axillary artery cannulation group 1/14, (7,7 %) mortality and 8/52 (15%) in femoral artery cannulation group.
Also we didn’t have postoperative new neurologic insult, arterial embolic event, postoperative bleeding and revision and moe educe incidence of sepsis, low output syndrome, in axillary artery cannulation group comparing with, 7,5% new neurologic events, stroke, 23% MSOF, 17% sepsis, 28% bleeding, 26% postoperative renal failure, in femoral patients (Table 2). No patients had complication related with axillary artery cannulation, no brachial plexus injury or revision for bleeding. In all the patients, CPB flow trout the axillary artery was adequately Peripheral ischemia was present postoperatively in two patients in femoral group and resolved by surgical revision of femoral artery. No ischemia was observed in axillary group.

Discussion
Arterial cannulation in emergency operation to repair an acute aortic dissection involving ascending aorta and aortic arch, has been performed standard by femoral artery (2, 15, 17, 18), ascending aorta or aortic arch by Westaby (19), axillary artery (1, 10, 11, 15, 16, 17, 18) or even transventricular, apexian special cannula, as recommended by some authors (12, 13).
The anatomopathological study by Van Arsdell (21) suggested that retrograde perfusion via femoral artery used by majority of surgeons can failed in cerebral and visceral malperfusion due to the false lumen.
Malperfusion is well know one of major factors contributing to the morbidity and mortality in acute aortic dissection. Also atheroembolism generated during cardiac operation  reprezented a major source of morbidity and mortality, promoting stroke, visceral injury or death. In order to reduce this complications some surgical team reintroduced in experimental study and clinical practice axillary artery cannulation.
Axillary artery cannulation for CPB conduction in not a new method, was first used by, DeBakey, Cooley and Crawford for aortic surgery in total circulatory arrest. The Cleveland group (Sabik) recommended this way for complex cardiac operation, severe aortic atherosclerosis, extensive aortic aneurysm and aortic dissection (1). But this placed can be also used in type B
dissection repair (3), in “no touch aorta“, aortic valve replacement, CABG (4, 5), to install even a Port Access for CABG in patients with high risk (6), mitral valve surgery with severe porcelain aorta (7), redo operation (8).
The major advantage of axillary artery cannulation is providing antegrade blood flow, avoiding cerebral malperfusion and embolic events when compare with historical way of femoral artery, retrograde flow of CPB.
Axillary artery is very rarely affected by dissection process or by atherosclerosis disease even in the setting of extensive involvement of periferal vessels (6). Also, axillary artery system has a large collateralization allowing a distal occlusion during CPB, without reperfusion syndrome comparing with the femoral system. Another advantage of axillary artery is the possibility to be use for antegrade cerebral perfusion during total circulatory arrest. The flow suggested  from experimental and clinical studies at 20ºC, is 10 ml/kg/min and a pressure of 30 mmHg measured in the right radial artery (in this situation a side graft to axillary artery should be attached), with occlusion of innominate artery. There are some concern about uniformity of cerebral blood distribution in case of absent circle of Willis (4). Transcranial Doppler preoperative could be used to evaluate this elective cases (4) or fi necessary perfusion of the left common artery. In our experience we used retrograde cerebral perfusion via superior cavla venae for washing also the possible debris and by inert to use a new method. There were no complication related with axillary artery dissection and cannulation, without vascular or brachial injuries.
Early and late results in acute aortic dissection type A, are very different reported in medical literature review, with mortalitity between 3,5% (24) up to 20 - 25% in another clinic (18). In the last years we succeeded to reduce mortality for this devastating disease under 15% and 7,7 % in axillary artery cannulation group. No cerebral stroke appears in antegrade flow of CPB through the axillary artery and also no visceral impairment due to ischemic reason. With caution and gentle dissection of axillary area, is possible to get access in some minutes without nerves lesion. Femoral artery is morer superficial located and in consequence easier to prepare, but the advantages offered by more physiological flow compensate this minutes spented.
However, we consider more study should be made until to have very clear results with the advantages of axillary artery over femoral. In medical review of axillary artery cannulation place there are only some reports with more than twenty patients operated by this approach (4, 10).

Conclusion
In this very aggressive pathology of acute aortic dissection we are still looking for the keys points to reduce morbidity and mortality. Interventional cardiologist are also searching and final practice to place a stented graft multibranches for aortic arch in patients with significant high risk for operation. All this achievements reduced the mortality from 30% at the beginning of this surgery up to 10% in large experience clinics.
Axillary artery cannulation represents another step in this direction, providing antegrade blood flow during CPB,  avoiding cerebral malperfusion and embolic events. Also axillary cannulation could be an ideal way for antegrade brain perfusion during total circulatory arrest by clamping of innominate artery after ruling out significant atherosclerosis or dissection (CT scan or direct inspection when aortic arch is open). This is the moment of decision for antegrade, retrograde or no cerebral protection. More studies will bring light in this field of cardiac surgery.

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