Femoral artery cannulation combined with axillary artery cannulation is safe for Stanford type A aortic dissection

Background The optimal cannulation strategy in surgery for Stanford type A aortic dissection is critical to the patients’ survival, but remains controversial. Different cannulation strategies have their own advantages and drawbacks during cardiopulmonary bypass. Our center used femoral and axillary artery cannulation for Stanford type A aortic dissection. The purpose of this study was to review and clarify the clinic outcome of femoral artery cannulation combined with axillary artery cannulation for the treatment of type A aortic dissection. Methods We performed a retrospective study that included 327 patients who were surgically treated for type A aortic dissection in our institution from January 2017 to June 2019.Using femoral and axillary artery cannulation to establish cardiopulmonary bypass in patients with type A aortic dissection. The demographics data and surgical data, clinical results of the patients were calculated.


Introduction
Stanford type A aortic dissection (AD) is a surgical emergency with a high rate of medical/surgical complication and mortality [1][2] . The optimal cannulation strategy in surgery for Stanford type A AD is critical to the patients' survival, but remains controversial [3][4][5][6] . Because the lesion mainly involves the ascending aorta and the aortic arch, the ascending aorta is often not suitable for cannulation to set up the extracorporeal circulation. Various cannulation techniques to establish a cardiopulmonary bypass (CPB) for the emergency treatment of AD have been reported [7][8][9] . The femoral artery and the axillary artery have become common alternative cannulation sites. Each of these cannulation sites has its own advantages and disadvantages, and the selection strategy is often affected by the range of lesion involvement, surgical methods, peripheral vascular lesions and other factors.
Femoral artery is the classic cannulation site of this kind of surgery. It can be easily performed before sternal opening, avoid ascending aorta cannulation. But many people question the risk of increased mortality, neurological complications, lower limb ischemia, malperfusion syndrome, embolism and other problems 3,10 .
The axillary artery cannulation can avoid these problems. In recent years, surgeons have begun to use axillary artery cannulation to treat type A AD due to malperfusion with traditional femoral artery cannulation. It provides an effective cerebral protection and is rarely involved in the AD so ensure the true lumen blood supply to the greatest extent, facilitating the implementation of anterograde selective cerebral perfusion for brain protection. Physiological blood ow direction reduces malperfusion complications during CPB and allows anterograde cerebral perfusion during circulatory arrest. However, axillary artery cannulation still has some defects such as insu cient ow, which may affect the perfusion of organs 11-12 . We have combined axillary artery cannulation with femoral artery cannulation to overcome the disadvantages of single cannulation. The strategy has been performed at our institution for more than ten years. This study reviewed the mortality and morbidity of type A AD in our hospital from January 2017 to June 2019, and analyzed the safety and e cacy of our combined cannulation strategies.
Material And Methods

1.Patients and methods
Medical records, operative records, and discharge summaries of all patients who underwent type A AD surgery with combined cannulation at our institution from January 2017 to June 2019 were reviewed in electronic medical record system and picture achieving and communication system. Records were noted for cannulation sites, surgical procedures, and overall clinical outcomes were reviewed. We were particularly concerned about postoperative lower limb ischemia, stroke, malperfusion, paraplegia, and death -complications that may be related to the cannulation site and retrograde perfusion.
The ethics committee of our institution, Union Hospital of Fujian Medical University in Fuzhou, China, approved this study protocol, Informed consent was waived as it was a retrospective study.

2.Surgical techniques
All patients were under general anesthesia. In order to avoid a malperfusion, the following measures are taken to minimize the risk: 1. Peripheral vascular condition is evaluated by computed tomography images, whether there is occlusive disease and whether there is dissection involvement; 2. Peripheral blood pressure monitoring and oxygen saturation detection were used to evaluate whether there was occlusive disease and dissection involvement. The affected arteries should not be cannulated if a signi cant stenosis and dissection are identi ed in the preoperative examinations.
We preferred right axillary artery combined with the right femoral artery cannulation. The surgeons were divided into two groups and started at the same time. During femoral artery cannulation, after a pursestring suture is placed on the exposed femoral artery, a femoral arterial cannula is inserted into the femoral artery by using the Seldinger technique. The right femoral artery is usually cannulated if dissection was absent in the right iliofemoral artery. If both sides are dissected, we exercise great care to make certain that our cannula is placed into the true lumen.
If the vital sign was stable, another group continue on anatomy the right axillary artery, the axillary artery exposure for cannulation was obtained through a 4 -6 cm incision about 2 cm under the Subclavian fossa. The bers of the pectoralis major muscle were blunt split. The pectoralis minor muscle is retracted laterally. After exposed the axillary artery, femoral artery clamps are used proximal and distal to the cannulation site. After clamping of the vessel and longitudinal arteriotomy, either direct cannulation with an arterial cannula or anastomosed a Dacron graft end-to-side to the axillary artery with a running 5-0 Prolene suture. Flow is evaluated through the cannula by back bleeding, and if adequate, the cannula is connected to the arterial line and secured to the skin.
Median sternotomy was performed, and venous cannulation was performed with a 2-stage right atrial cannula. or with superior and inferior vena cava cannulation if combined with intracardiac operation. The arterial perfusion line was divided into two branches on the operating table, and "single pump and double tube method" was adopted for management, so as to transfer the position of artery perfusion and protect the cerebral at different stages of the operation.
After cannulation, the position of cannulation was con rmed by observing whether there was a clear blood return, whether the pump pressure was normal, and whether there was a signi cant increase in the pump pressure after pumping 50 ~ 100ml of liquid to eliminate the possibility of insert to the dissection. The arterial pressure of the radial and dorsal foot arteries, transesophageal echocardiography (TEE) and regional cerebral oxygen saturation were routinely monitored by an anesthesiologist.
After the CPB was initiated, we routinely palpated the aorta and compared the pressures of the radial artery and dorsal foot artery, and evaluated the area ratio of the true lumen and false lumen in the descending aorta with TEE to evaluate whether there is a case of malperfusion. We changed the arterial cannulation site if we suspected that the patients had malperfusion syndrome caused by inadequate perfusion.
During surgery, our brain protection methods were deep hypothermia concomitant with selective antegrade cerebral perfusion (SACP). Also, neuro-protective drugs were administered and the head was cooled with a topical ice hat. The axillary artery is rarely dissected, so we can put the cannula inside the true lumen basically. After establishment of the circulatory arrest, we can nd the back ow in the ori ce of arch vessels. But if we can nd not, we put another cannula inside the ori ce of carotid artery [13][14] .
If the dissection involves only the ascending aorta, the ascending aorta and a hemi-arch replacement are usually performed. For patients with arch department involvement, we usually use triple-branched Stent Graft technology 15 . During core cooling, the left common carotid and innominate arteries were dissociated from the surrounding tissue. After the ascending aorta was clamped, aortic root manipulations such as aortic valve repair and sinus of Valsalva reconstruction were performed. Then the Dacron tube graft was subsequently continuous anastomosis to the aortic root. When a 22°C rectal temperature was achieved, selective cerebral perfusion via the right axillary artery was started at a rate of 10 to 15 mL/kg/min, and femoral artery perfusion was discontinued. Then the left common carotid artery and innominate artery were cross-clamped, next transected the ascending aorta at the base of the innominate artery. The triple-branched stent graft was inserted and properly positioned. Finally, continuous end-to-end anastomosis was performed between the arti cial vessels and intraoperative stents. After the dissection operation and after the air was carefully ushed out, systemic perfusion was resumed, and the patient was rewarmed [16][17][18] .

3.De nition of clinical parameters
Early mortality was de ned as all-cause mortality either in-hospital or within 30 days of surgery. Transient neurologic dysfunction was de ned as the occurrence of post-operative confusion, agitation, and delirium without focal neurologic symptoms. Permanent neurologic injury was de ned as the new onset of focal injury (stroke) or global dysfunction (coma) after a surgical repair with and without morphological correlates in a brain computed tomography or magnetic resonance image. Early stroke was de ned as permanent neurologic injury being evident after the emergence from anesthesia. Delayed stroke was de ned as permanent neurologic injury after rst awaking from surgery without a neurological de cit. Acute kidney injury was de ned as serum creatinine concentrations over 133 μmol/l or the need of dialysis due to oliguria. Postoperative liver failure was de ned as at least having two of the following parameters were concurrently observed: the coagulation abnormality, total bilirubin > 15 mg/dL, liver enzymes levels more than tenfold the upper limit of normal, alteration of consciousness, asterixis.

4.Statistical analysis
Statistical analysis was performed with SPSS ver. 22.0(SPSS Inc., Chicago, IL, USA). Continuous variables with a normal distribution were expressed as mean ± standard distribution. nonnormally distributed data were expressed as median.

Results
A total of 327 patients who underwent surgical repair for type A AD in our institution between January 2017 to June 2019. There were 253 male and 74 females with a mean age of 52. 16  Neurologic Symptoms (n) 7 Cardiac tamponade (n) 13 Renal insu ciency (n) 11 Hepatic insu ciency (n) 4

Paraplegia (n) 2
Transient leg ischemia 3 The ascending aorta was replaced in all cases. The most frequent extent of aortic replacement was ascending aorta and hemiarch replacement combined with modi ed triple-branched stent graft implantation for repair type A AD. The detailed operative procedures are shown in    Table 3.

Discussion
Type A AD surgery is associated with high mortality and high complication morbidity. Establishing a CPB that maintains adequate systemic perfusion is essential to prevent end-organ hypoperfusion during the procedure. Femoral artery cannulation and axillary artery cannulation to establish extracorporeal circulation are widely used in clinical practice and have been extensively reported in the previous literature [19][20][21] .
The femoral artery has been used as the primary cannulation site for CPB in cardiac surgery for more than 40 years [22][23] . Several studies have shown that retrograde perfusion of the femoral artery has the following de ciencies: (1) "Live valve" effect and false cavity blood supply, leading to central nervous system, upper arm, kidney and abdominal organ perfusion disorders; (2) false lumen blood supply and retrograde blood ow ush atherosclerotic plaque on the vascular wall, leading to embolization increase the incidence of stroke; (3) compared with the axillary artery, it is more easily involved by atherosclerosis and extensive interlayer; (4) lower limb ischemia; (5) Anterograde selective cerebral perfusion is inconvenient [24][25] .
Since 1995, axillary arterial cannulation has been used as an alternative to the femoral artery in patients with type A AD 26 . Compared with femoral artery cannulation, axillary artery cannulation can signi cantly reduce central nervous system complications in patients with deep hypothermia. Anterograde selective cerebral perfusion is considered to be the most ideal method for cerebral protection at present, and axillary artery cannulation can be very convenient to coordinate with it for brain protection, which greatly reduces the side effects brought by deep hypothermia and circulatory arrest (DHCA). In this group, 32,9% of the patients were cannulated in the axillary artery, and none of the patients showed a veri able insu ciency of visceral perfusion during the operation [27][28] . In addition, the advantages of axillary artery cannulation are also shown in the following aspects: 1.the collateral circulation of neck and shoulder is rich. Only 15% of the human beings have no functional circle of Willis 2. not easily affected by atherosclerosis and dissection; 3. to avoid retrograde embolism and the expansion of the dissection; 4.
facilitate selective cerebral perfusion.
One disadvantage of axillary artery cannulation is that it takes more time to construct. But Budde et al. used axillary artery cannulation to establish CPB in 61 patients undergoing elective and emergency surgery due to proximal aortic pathology. There were no signi cant differences in postoperative neurological dysfunction or mortality between the selective group and the emergency group. They claimed that the routine use of axillary artery cannulation in emergent cases is just as safe and e cacious as in the elective setting 29 . However, the biggest disadvantage of axillary artery cannulation is the insu cient ow, which may affect the perfusion of organs 12 .
Our center used femoral artery combined with axillary artery cannulation to establish extracorporeal circulation, providing reliable circulation support for AD repair. Few studies have examined the clinical outcomes of this cannulation strategy. In this study, 96.94% (317/327) of the patients undergoing femoral and axillary artery cannulation survived. In addition, the incidence of permanent neurologic dysfunction, renal insu ciency, live failure and lower limb ischemia were respectively 0.92%, 4.89%, 1.53% and 0.92%. Based on the results of our institution, we conclude that femoral artery combined with axillary artery cannulation results in satisfactory short-term outcomes.
Combined with femoral artery and axillary artery cannulation, with this single pump and double tube method, the true lumen of AD can be fully perfused to the greatest extent during CPB, avoiding systemic poor perfusion. In addition, anterograde cerebral perfusion can also be carried out through the upper body during the circulatory arrest, which greatly ensures the cerebral perfusion and reduces the incidence of cerebral complications 30 .

Conclusion
Femoral artery combined with axillary artery cannulation for Stanford type A AD can signi cantly improve the prognosis of patients, especially in cerebral protection and reducing the occurrence of adverse malperfusion syndrome, as well as reducing the time of cooling and rewarming. This study complied with the requirements of the Ethics Committee of Fujian Medical University, and adhered to the Declaration of Helsinki. Written informed consent was also obtained from the patient or a relative of the patient.

Consent for publication
Not applicable.

Availability of data and materials
Data sharing not applicable to this article as no data sets were generated or analyzed during the current study.

Competing interests
The authors declare that they have no competing interests.

Funding
There is no nancial support for this work.
Authors' contributions L-WC and L-CH and Q-CX designed the study, participated in the operation, and drafted the manuscript. Q-CX and L-CH collected the clinical data and performed the statistical analysis. X-FD and D-ZC provide technical support. All authors read and approved the nal manuscript.