I. Indications for Sun’s surgery
Sun’s procedure is mainly applied to patients with extensive thoracic aortic or thoracoabdominal aortic lesions involving the ascending aorta, aortic arch and thoracoabdominal aorta, which often require second-stage thoracic aortic or thoracoabdominal aortic replacement after the ascending aorta and aortic replacement. In patients with lesions in the ascending arch of the aorta combined with lesions in the upper segment of the thoracic aorta, the Sun’s procedure can be used to obtain a one-stage radical cure.
II. Basic anesthesia methods
(I) Adequate sedation and analgesia before anesthesia.
Take O.1g of oral hypocretin the night before surgery, 10mg of oral valium or o.1g of hypocretin one hour before surgery, and morphine half an hour before surgery. In patients with severe preoperative chest pain, 10mg of morphine can generally be injected intramuscularly for analgesic purposes.
(ii) Induction and maintenance of anesthesia.
This procedure is more important to maintain hemodynamic stability than the choice of anesthetic drugs and methods. In patients with concomitant hypertension, both thiopentone sodium and isoproterenol can be safely used for induction, while etomidate is a good choice for those with cardiac insufficiency. The combination of imipramine and fentanyl can be used in patients with hypertension and good cardiac function. Anesthesia maintenance is based on opioid analgesics and strong inhalation anesthetics.
(iii) Circulatory monitoring.
Central venous pressure and traumatic pulse pressure in the upper and lower limbs should be routinely monitored intraoperatively. In case of large pressure difference between two limbs, the side with high pressure should be selected for monitoring invasive arterial pressure. The right axillary artery is often selected for selective cerebral perfusion in Sun’s surgery, and the right internal jugular vein should be selected for venipuncture, while radial artery puncture and arterial oxygen saturation monitoring should be placed in the left upper limb, and the lower limb arteries are routinely punctured for pressure measurement to understand the preoperative and postoperative upper and lower limb pressure differences.
(iv) Neurological monitoring.
EEG and transcranial Doppler are routinely applied.
(v) Cerebral protection measures.
Before extracorporeal circulation after anesthesia, the patient’s blood pressure should be maintained as much as possible. In the normal range, the mean arterial pressure should be maintained above 50 mmHg in extracorporeal circulation. The general nasopharyngeal temperature is reduced to below 20°C during stopping the circulation. Simultaneous application of the right axillary artery cannula for selective cerebral perfusion with a flow rate of 5-10 ml/kg/min40-60 mmHg.
(vi) Hemoprotection and management of coagulation abnormalities.
Generally prepare l0 units of blood cells, 2000 ml of plasma and 2 therapeutic units of platelets. Quickly input 1 therapeutic unit of platelets after the neutralization of fisetin, and subsequently apply plasma for rapid restoration of coagulation, and then input another unit of platelets if necessary. All bleeding after fisetin neutralization was recovered with ceIlsaver.
III. Basic methods of extracorporeal circulation.
(A) Ice cap was placed on the head after induction of anesthesia, and the body surface of the variable temperature blanket was cooled.
(B) Routine preparation of arterial single pump double tube, right axillary artery cannulation (sometimes joint application of femoral artery cannulation), right atrial placement of bipolar cannula for drainage, right upper pulmonary vein placement of left heart drainage.
(iii) The nasopharyngeal temperature is lowered to 20C, the anal temperature is 25C, and the operative field is routinely filled with CO2.
(iv) Methylprednisolone 15mg/kg was given in head-down position 30, stopping circulation and selective cerebral perfusion (flow rate 5-10ml/kg/min) was started, and 10ml a 15ml/kg of blood was released intravenously.
(v) Open venous drainage after slow arterial return of blood at the end of stopping circulation and resume extracorporeal circulation.
(vi) After restoration of circulation, try to use off-flow perfusion, and start rewarming after mixed venous oxygen saturation >85%, and perform artificial renal ultrafiltration during rewarming.
(vii) Give methylprednisolone 15mg/kg and mannitol 0.5g-lg/kg after rewarming.
(viii) The management of acid-base balance is based on a_steady state, but an acidic environment can be maintained during hypothermia.
(ix) Except for the period of stopping circulation, if conditions permit, the same stop-jump solution should be instilled.
(X) If forward selective cerebral perfusion cannot be implemented, retrograde perfusion via the superior vena cava is also an option, with flow rate, superior vena cava pressure maintained at about 25 mmHg, and oxygen saturation in the cephalic brachial artery greater than 70%.
IV. Main surgical steps
(A) Preparation before cutting skin
Unlike conventional extracorporeal circulation surgery, Sun’s surgery requires simultaneous puncture and pressure measurement of the left upper and lower extremities, and central venous line is placed in the right internal jugular vein. The patient is placed in supine position with the upper chest pad elevated and the neck in extension. The skin disinfection and towel laying method is the same as that of coronary artery bypass grafting, but the range of axillary artery and femoral artery free cannulation should be left after the towel laying.
(B) Freeing the right axillary artery
A 6-8 cm long incision perpendicular to the long axis of the body is made under the right clavicle from the skin of the inner 1/3 intersection of the clavicle outward, the pectoralis major muscle is separated bluntly, the deep pectoralis minor muscle is pulled outward with the thyroid pulling groove, the axillary vein is firstly freed and banded, and if necessary, 1.2 branches of the upper edge of the vein are ligated, and the axillary vein is drawn downward, and the axillary artery is located above the posterior part of the axillary vein. The axillary artery will be free for about 3 cm, and the branch of the segment will be ligated, and the proximal and distal ends will be tied separately for backup, taking care not to damage the surrounding brachial plexus nerve when freeing the axillary artery.
(C) Open chest and head and arm vascularization
The sternal opening is the same as the conventional extracorporeal surgery, but the skin incision at the upper edge reaches the upper sternal fossa or deviates upward to the left or right, sometimes the incision needs to be extended to the neck, and the sternum must be split gently, and after the sternum is drawn, the stump of the thymus is removed and the left innominate vein is free and brought up. The left innominate vein is lifted and pulled downward to further free the innominate artery below it, the left common carotid artery and the right subclavian artery. This procedure is best accomplished prior to heparinization.
(iv) Establishment of extracorporeal circulation
After heparinization of the cephalobrachial vessels and the anterior and posterior walls of the aortic arch, arterial pumping is routinely performed with a single pump and two tubes, one of which is inserted through the axillary artery to establish extracorporeal circulation, while the other is used as a femoral artery cannula or an artificial vascular perfusion cannula. The left heart can be drained via the right upper pulmonary vein or the main pulmonary artery.
(E) Treatment of the proximal aorta
The treatment of the proximal aorta is mainly dependent on its pathological changes. For patients with aortic sinus diameter greater than 5.Ocm, aortic root replacement or root replacement with preserved aortic valve should be performed depending on the aortic valve lesion; aortic diameter between 4.0 ～If the aortic diameter is between 4.0 and 5.Ocm, sinusoplasty and aortic valvuloplasty should be performed first, and if necessary, aortic valve replacement and partial aortic sinus replacement are feasible.
If the aortic sinus diameter is less than 4.O cm, the aortic sinus should be preserved and the aortic valve should be shaped or replaced. If the right coronary artery ischemia is present before surgery and the right coronary opening is significantly involved during intraoperative exploration, the right coronary opening can be sutured closed and right coronary artery bypass grafting can be performed. During the treatment of the proximal aorta, when the nasal temperature drops to 20°C, the proximal operation is suspended and the treatment of the aortic arch and descending aorta is shifted.
(vi) Aortic arch replacement and stent elephant trunk implantation
The nasal temperature was brought to 20℃, the head was lowered, CO2 was blown into the surgical field to remove the air within it, the three cephalic vessels were blocked separately, while selective cerebral perfusion was performed via the right axillary artery, the aortic arch was dissected, the three cephalic vessels were transected, the proximal end of the left subclavian artery was closed with 4/0 prolene suture, and the appropriate type of stent elephant trunk was selected for implantation into the true lumen of the descending aorta via the distal port of the aortic arch, trimming the multiple The aortic arch tissue was trimmed so that the edges were flush with the artificial vessel proximal to the stent trunk.
A quadrant artificial vessel with a diameter comparable to that of the stent elephant trunk was selected, and its main vessel was anastomosed distally to the descending aorta with the stent elephant trunk with continuous sutures around the entire circumference of the 3/0prolene line, and the other end of the arterial pumping tube was inserted into the perfusion branch of the artificial vessel to restore lower body circulation, and the corresponding branch of the cephalic arm vessel was first anastomosed to the left common carotid artery with continuous sutures of 5/0prolene line, and the venting was opened to start Resuscitation, followed by anastomosis of the proximal end of the main vessel of the artificial vessel with the proximal end of the aorta, 4/0prolene line continuous with the suture, restoration of cardiac circulation, and finally anastomosis of the branch of the innominate artery and the left subclavian artery.
(vii) Proximal aortic anastomosis
In patients with preserved aortic root, the aorta is transected at 0.5-1 cm above the sinotubular junction and anastomosed proximally with the quadrantal artificial vessel with continuous sutures of 3/0prolene thread. In patients with root replacement, the two artificial vessels are anastomosed end to end after completion of the root surgery and sutured continuously with 4/0prolene sutures.
(H) Resuscitation and detachment from extracorporeal circulation
After completing all the vascular anastomoses, the aortic blocking clamp is opened by full venting, the heart is resuscitated by electric shock, the nasal temperature to 37.5℃ and the anal temperature to 35℃ can be slowly evacuated from the extracorporeal circulation, and each anastomosis is checked for active bleeding and sutured closed during the resuscitation process, and the extracorporeal circulation doctor is ready for blood recovery after the shutdown.
(ix) Neutralization and postoperative hemostasis
After evacuation of the extracorporeal circulation machine, it is clear that there is no active bleeding, and then the patient’s coagulation function is rapidly restored by rapid neutralization at a ratio of 1 to 1.5 of heparin and fisetin, along with rapid application of 1 therapeutic unit of platelets and, if necessary, fresh plasma. The application of gauze compression and patch wrapping for anastomotic pinhole bleeding can often achieve the purpose of hemostasis. For bleeding from the proximal and distal anastomoses when the above methods are ineffective, a shunt should be performed with the right atrium after wrapping the anastomosis.
(X) Chest closure
It is basically the same as after conventional extracorporeal circulation, but the head and arm vessels should be placed well before closing the sternum to avoid twisting, folding and compression.
(I) Difficulty in revealing the right axillary artery
Cannulation of the right axillary artery is the key to perform selective cerebral perfusion. Clinically, we sometimes encounter difficulties in revealing the axillary artery and cannulation, mainly due to unclear anatomy of the local area, inappropriate skin incision, incomplete blockage of the lateral branch ligation, and incorrect direction of cannulation.
We generally choose the right subclavian from the intersection of the middle and inner 1/3 of the clavicle to make a skin incision 6-8 cm long perpendicular to the long axis of the body, bluntly separate the pectoralis major muscle, pull the deep pectoralis minor muscle to the outside with the thyroid groove, free the right axillary vein in the deep surface of the tissue, first ligate 1-2 branches of the upper edge of the jugular vein, pull the axillary vein to the bottom, and find the axillary artery above it. The axillary artery can be found above it. The thoracic-shoulder artery is superficially exposed and clearly pulsating in this area, and sometimes the main trunk can be successfully found along this artery and free the ligature proximally and distally. When freeing the artery, care is taken to completely ligate or block the arterial branches at the cannulation site and not to injure the adjacent brachial plexus nerve.
Choose an arterial cannula of comparable size, with the pectoralis minor muscle fully abducted and the lateral end of the artery slightly raised, the cannula can be inserted smoothly in the direction of the axillary artery, and the length of insertion is generally 3-4 cm, avoiding too deep and too shallow, the former can lead to high pump pressure, while the latter has the risk of dislodgement.
(B) Difficulty in freeing the head and arm vessels
Patients with obesity, ascending aortic aneurysm pushing, partial branch anatomical abnormalities of the aortic arch, chronic aortic coarctation especially coarctation involving the cephalobrachial vessels increase the difficulty of freeing the vessels on the arch. In this case, the residual thymus tissue can be fully excised first, and even the left unnamed vein can be transected first (usually reanastomosis is required after surgery) to better reveal the supra-arch vessels. In patients with adhesions around the cephalic vessels due to dilated arteries or aortic coarctation, the vessels can be free from their distal ends to their proximal ends first. In cases where the left subclavian artery is deeply located, especially in cases where the aortic arch is significantly dilated, the vertebral artery originates directly from the aortic arch, and the surrounding adhesions are present, it is often possible to free the left common carotid artery at its deep side by fully freeing it and pulling it to one side. In patients with more difficulty, the artery can be freed by finding the internal port under extracorporeal circulation or even deep hypothermic stopping circulation without pressure.
(C) Injury to surrounding tissues
There are many important tissue structures around the aortic arch, including trachea, esophagus, nerves, thoracic duct, etc. In order to avoid damage to these structures, in principle, the aortic wall should be close to the aortic wall during the freeing of the distal anterior wall of the arch and the suturing of the posterior wall, which can injure the vagus nerve, phrenic nerve and the recurrent laryngeal nerve. When freeing the subclavian artery, it is easy to injure the thoracic duct, and the exposed celiac should be ligated thoroughly, and the left pleura should be kept intact as much as possible when freeing the distal arch and left subclavian artery, which is more conducive to postoperative examination of bleeding and reduction of blood loss.
(iv) Difficulty in anastomosis of the left subclavian artery
In the case of deep location of the left subclavian artery and short freeable range, it is extremely difficult to anastomose with the artificial vessel branch, increasing the chance of bleeding from the anastomosis, especially after it itself is affected by the entrapment. At this time, the left subclavian artery can be directly ligated, while the original corresponding artificial vessel branch is used to pass through the thoracic cavity through the second intercostal space to pass out the end-lateral anastomosis to the left axillary artery, or through the superior sternal fossa and through the anterior cervical muscle group to anastomose to the left axillary artery.
(E) Difficulty in stent elephant trunk implantation
Stent implantation is easier in acute aortic coarctation, but can be difficult in chronic aortic coarctation when the true lumen is small and the intima is thickened. In this case, the operator can use the index finger to feel the direction of the true lumen of the descending aorta and put in a high strength piece of pulling hook along the direction first, and then the stent trunk is implanted in the direction of the piece of pulling hook. Sometimes the stent trunk needs to be bent into a certain curve to facilitate implantation into the descending aorta. Note that sometimes there is a large aortic endothelial rupture at the beginning of the descending aorta, and direct stent implantation is likely to enter the false lumen, so the stent can be placed into the descending aorta with the lamellar hook first and over the distal end of the rupture, and then the stent can be sent in the direction of the lamellar hook to avoid the possibility of implantation into the false lumen.
(F) Failure of right axillary artery cannulation
Perfusion of the right axillary artery can significantly reduce the occurrence of cerebral complications and improve the safety of the procedure. However, in some patients, the right axillary artery is also entrapped or cannot be perfused via the right axillary artery, so direct cannulation via the left common carotid artery can be used to achieve selective cerebral perfusion before stopping the circulation. If both the innominate artery and the left common carotid artery cannot be directly cannulated for reasons of thrombosis, entrapment, or arterial plaque, the superior vena cava can be retroperfused via a bifurcation of the arterial pumping tube with a flow rate of 5-10 ml/kg/min and a pressure of 25 mmHg.