Introduction
This detailed illustrated article describes our preferred
surgical technique of total arch replacement using selective antegrade
cerebral perfusion (SACP). Our current approach includes: (I) meticulous
selection of arterial cannulation site and type of arterial cannula;
(II) SACP for neuro-protection; (III) whole body hypothermia with
minimal tympanic temperatures between 20 and 23 °C and minimal rectal
temperatures below 30 °C; (IV) early re-warming after distal anastomosis
with SACP flow adjustment while monitoring brain oxygenation by near
infrared spectroscopy (NIRS); and (V) after 2006, maintaining strict
fluid balance below 1 L by the extracorporeal ultrafiltration method
(ECUM) during cardiopulmonary bypass (CPB), with the expectation of more
rapid pulmonary functional recovery.
Operative techniques
Preparation
The patient is placed in the supine position and
the diodes of NIRS are attached on the foreheads bilaterally. For NIRS,
we use INVOS 5100C (Somanetics, Troy, MI), which provides continuous
regional cerebral oxygen saturation (rSO
2). The rSO
2
readings are expressed as an index, measuring differences from an
unknown baseline. A standard median sternotomy is performed and there is
no need for extension of the skin incision to the left neck.
Before
going on the CPB, the innominate vein is fully mobilized with division
of several branches to facilitate exposure of the aneurysm. The vein is
seldom divided (
Figure 1).
Dissection of the aneurysm, aortic arch branches, or the vagus nerve is
not usually performed to minimize aortic manipulation and recurrent
laryngeal neuroprexia. Taping around the arch or arch vessels is not
necessary (
Figure 2). The serrated balloon tipped cannulae usually sit well in the neck vessels without snaring or can be fixed with a silk suture.
Cannulation
Preoperative CT scan is done in every patient to
assess the atheromatous lesions in the ascending aorta. Both
transesophageal and epi-aortic echocardiography are applied to
interrogate the ascending aorta and determine cannulation site. CPB is
established with bi-caval drainage. The left ventricle is vented through
the right upper pulmonary vein. Femoral artery cannulation is applied
particularly in patients with aortic dissection. For the diseased
ascending aorta/aortic arch, a 24 Fr dispersion arterial cannula
(Duraflo II, Edwards Lifesciences LLC, Irvine, CA) is used. Otherwise a
straight tip cannula in the ascending aorta (DLP, Medtronic,
Minneapolis, MN, USA) is used. Cannula tip is always set towards the
aortic valve to avoid direct flow to the arch (
Figure 2).
All patients receive 100 mg of betamethasone sodium phosphate, and 100
mg of sivelestat sodium hydrate is added to the pump circuit at the
initiation of CPB.
Exposition
After tympanic temperature has dropped down to 23
°C with rectal temperature below 30 °C, the aortic arch aneurysm is
opened while raising the central venous pressure to 10 mmHg or brief
periods of retrograde cerebral perfusion. By using four traction
sutures, including one at the root of each arch vessel and one in the
lesser curvature of the arch, the inside of the aortic arch is exposed (
Figure 3).
Aortic arch reconstruction
The vagal nerve is never dissected out to prevent
left recurrent laryngeal nerve injury and to alleviate inadvertent
injury of the esophagus. Direct circumferential transection of the
proximal end of the descending aorta, distal to the aneurysm is usually
performed starting at 3 o’clock position. Incising back of the aortic
arch may not be necessary and can be rather harmful sometimes to the
left recurrent laryngeal nerve (
Figure 4).
It is very important not to lose the adventitia in this maneuver.
Further dissection of the descending aorta, at least 3-5 cm, is
necessary in order to have enough suture bites and for placement of a 25
mm wide Teflon felt strip around the proximal descending aorta. Usually
the bronchial arteries are divided, and sometimes the upper intercostal
arteries, in order to mobilize the descending aorta (
Figure 5).
The thoracic duct often lies along the descending aorta in this level
and should not be injured. Every attempt is made to leave the left
pleura intact otherwise inadvertent bleeding from the distal anastomosis
may escape into the deep in the left pleural cavity and go unnoticed.
A sealed four-branched (10, 8, 8, 8 mm) graft (J graft.
Japan Lifeline, Tokyo or Triplex, Terumo Corporation, Tokyo, Japan) is
used. Open distal aortic anastomosis is performed with a flexible sucker
being placed inside the graft to collect blood in the descending aorta (
Figure 6).
A 4-0 monofilament suture on a 22 mm needle is used. The suture starts
at 9 o’clock position, progressing counter-clockwise. Suture is tied
first and bites are taken at least 10 mm apart. After completing the
anastomosis, a 4-0 compacting suture is placed to fasten the Teflon felt
(
Figure 6).
Lower body circulation is then
reinstituted through one branch of the graft, sometimes after flushing
from the femoral arterial cannula, and whole body rewarming is started
with antegrade perfusion (
Figure 7).
At this stage, secure hemostasis in the distal suture line must be
obtained. Concurrent with re-warming, SACP flow is gradually increased
while maintaining the baseline values of rSO
2. However, SACP flow is limited below 1,200 mL/min at all times to prevent brain edema.
Epi-aortic vessel reconstruction
Aortic arch is divided to make vessel buttons with each traction suture (
Figure 8).
Three arch vessels are reconstructed tandem to the graft branches using
a 5-0, 17 mm needle, monofilament suture. Usually the parachute
technique is used and each vessel is perfused after completion of the
anastomosis. CPB is then weaned-off. The left pleura is now opened
longitudinally near the sternum to monitor unexpected bleeding into the
left pleural cavity.
If the patient also has carotid artery or
intracranial artery stenosis/occlusion, epi-aortic vessel reconstruction
is performed prior to re-warming (
Figure 9).
After distal anastomosis to the descending aorta, while perfusing the
brain at 23 °C, the left subclavian, left common carotid, and
brachiocephalic arteries are anastomosed and perfused. Rewarming is then
started and proximal anastomosis is performed in the same fashion.
Aortic dissection
In patients with acute aortic dissection,
requiring total arch replacement, hypothermic circulatory arrest is
achieved and the arch is opened. SACP is initiated by inserting three
balloon-tipped catheters in the true lumen of the arch branches. No
tourniquet around the arch vessels is necessary. The arch is transected
just distal to the left subclavian artery and the adventitia of the
descending aorta is carefully dissected without injuring it (
Figure 10).
A 5 cm long, 16 to 20 mm wide,
Dacron graft is inserted in the true lumen of the descending aorta and a
wider, 3 cm, Teflon felt strip seated outside the adventitia (
Figure 11).
A continuous 5-0 polypropylene horizontal mattress suture with straight
needle is used to secure the elephant trunk, dissection flap, and the
adventitia (
Figure 12).
At this stage, all circulation is stopped for 3 minutes to dry-up the
lumen of the descending aorta, and biological glue (Bioglue) is used to
obliterate the false lumen.
Distal anastomosis with four-branched graft
to the descending aorta, including the elephant trunk, aortic wall, and
the felt strip, is then performed using 4-0 sutures (
Figure 13).
The circulation of the lower body is then initiated.
The proximal aortic stump is incorporated with the aortic valve
commissures, the false lumen, and the inner and outer Teflon felt using
same 5-0 polypropylene horizontal mattress sutures (
Figure 14).
Proximal anastomosis is done in the same manner. Aortic arch branches
are also reconstructed using small pieces of Teflon felt strips.
The fluid balance during CPB is strictly
controlled and kept below 1,000 mL by the ECUM (Capiox Hemoconcentrator
HC11, Terumo Co., Tokyo, Japan). After completion of total arch
replacement, the patient is weaned off CPB, receives protamine and
decannulated as per routine.
For surgical approaches to the arch aneurysm,
especially for the distal arch aneurysm, both median sternotomy and left
thoracotomy can be applied. However, we have been using median
sternotomy exclusively to avoid several complications associated with
left thoracotomy. Patients with chronic obstructive lung disease or
chronic aortic dissection tend to have some adhesions between the
aneurysm and the left lung. Lung injury secondary to surgical
manipulation, especially after deep hypothermia, can add further risk to
the postoperative pulmonary complications (
1).
Also, the incidence of left recurrent laryngeal nerve damage was higher
in patients who had left thoracotomy than those with midsternotomy. We
reported that the level of carina or 17 cm from the sternum level to the
back was approachable from the median sternotomy (
2).
The
selection of an arterial cannulation site and type of cannula are very
important in preventing atheroembolic events, particularly neurological
complications. In most instances we select the ascending aorta as an
arterial cannulation site after inspection of the epiaortic echographic
scan. In an experimental study, Fukuda
et al. (
3)
confirmed that directing the cannula tip of the Dispersion cannula
towards the aortic root generated slower and less turbulent flow in the
transverse arch of the glass models of both healthy and aneurysmal
aortic arches.
Selective antegrade
cerebral perfusion is now considered to be most reliable brain
protection method and has been widely used in the field of aortic
surgery, albeit with variations (
4,
5). We have always used three cannulae, which are inserted from inside of the arch without snaring. Urbansky
et al. (
6)
used only one cannula to perfuse the whole brain and reported a low
incidence of postoperative stroke. Many surgeons perfuse only the
brachiocephalic and left common carotid artery, and not the left
subclavian artery. However, incompleteness of the circle of Willis has
been reported as 20% to 30% in normal population(
7),
with the vertebral arteries sometimes hypoplastic or stenotic,
especially in elderly patients. Also the left subclavian artery often
supplies collateral vessels to the spinal cord.
As noted by Kouchoukos
et al. (
8),
the exclusion technique for aortic anastomosis or aortic branches is
securer than the inclusion technique. We always transect the aorta just
distal from the aneurysm and divide several bronchial arteries. This may
also alleviate inadvertent injury to the esophagus or left lung.
Technically, transection of the aorta is usually performed by incision
circumferentially from inside of the aorta, not by incising the aortic
arch wall anteriorly or posteriorly.
Usage
of the four-branch graft has several potential advantages over the
“island” aortic cuff technique to reconstruct the arch vessels.
Individual anastomosis of each arch vessel can provide secure
anastomosis. By also dividing the arch cuff into the three buttons, more
liberal exposure of the aortic arch can be obtained. Consequently,
proximal anastomosis of the ascending aorta can precede the arch
anastomosis and the resultant reduction in the cardiac ischemic time is
beneficial.
In summary, we have found that
SCAP is a reliable neuro-protection strategy during aortic arch
surgery. In our hands, SACP is associated with low perioperative
morbidity and mortality.
Acknowledgements
Disclosure:
The authors declare no conflict of interest.
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