Anesthetic Challenges for Modified Bentall Procedure in a Pregnant Marfan Patient with Acute Stanford Type A Dissection

Aortic dissection is a life-threatening condition which requires immediate surgical intervention. It has been estimated that half of aortic dissection and/or ruptures in women younger than 40 years of age have been associated with pregnancy. The limited data on the coincidence of Marfan syndrome, pregnancy and aortic dissection makes its anesthetic management a formidable challenge to any anesthesiologist. This is a case of a 33-year-old G1P0, 28 weeks age of gestation with Marfan syndrome, who had Aortic Dissection Stanford type A and underwent an emergency Modified Bentall’s surgery with cardiopulmonary bypass and deep hypothermic circulatory arrest. This case illustrates the dilemma of managing this case since there are two patients involved, mother and fetus. Wrong decision could result in demise of both. Although the aim is life for both, survival of one without neurologic sequelae is already considered a success.

Deep hypothermic circulatory arrest (DHCA) is technique required in cases of acute aortic dissection or aneurysms that extend into the aortic arch. 49SSN: 1978-3094 .Medicinus.2018; 7 (1) : 17-26  Surgical replacement of the aortic valve and surgery of the aortic aneurysm or dissection that extend into the aortic arch carry risk of neurologic injury from global ischemia or embolization of atherosclerotic debris secondary to clamping of the great vessels. 5Surgery of descending aorta is associated with postoperative paraplegia secondary to interruption of 13 to 17% of blood supply of the spinal cord. 5is case report will show how neurologic sequelae was prevented during anesthesia for modified Bentall procedure to a pregnant Marfan patient with acute type A dissection.

Case summary
This is a case of a 33-year-old primigravid, 28 weeks age of gestation (AOG) with Marfan syndrome, who consulted due to sudden chest discomfort with radiation to the left jaw associated with burning substernal chest pain and diaphoresis.
Past medical history showed that the patient had hiatal hernia and gastroesophageal reflux disease (GERD) and was on esomeprazole tab as needed.She had no previous surgery.Prenatal check up was not clear.Modified Bentall's procedure with double set up for possible obstetrical intervention was contemplated.Risks and benefits were explained to patient and relatives.The risk of demise for both the patient and fetus was not eliminated.Survival of patient but with neurologic and nephrologic sequelae was also a possibility.There was no immediate indication for an emergency caesarian section and fetal demise can occur.The risks were explained by all specialists obstetrician, cardiologist, thoracic, cardiovascular surgeon, intensivist, neonatologist and anesthesiologist.
Patient and relatives accepted risks.
Urgent modified Bentall procedure was scheduled.Initial vital signs were as follows: BP 165/60 mmHg, HR 105 bpm and pulmonary arterial pressure (PAP) 25/19 mmHg (normal PAP is 15-28/ 5-16mm Hg). 52itial arterial blood gas showed a metabolic acidosis (see Appendix A) and was corrected with the NaHCO3 administration.Nitroglycerin drip was started during induction period to achieve hemodynamic stability during intubation and to improve coronary blood flow.
Anesthetics administered were as follows: fentanyl 250µg followed by infusion, midazolam 1 mg, propofol infusion, rocuronium 50 mg followed by infusion and sevoflurane titrated between 1-3%.Patient was intubated with 7.5 size ETT under direct visualization of vocal cords.She was hooked to ventilator with the setting as follows: volume controlled ventilation, tidal volume 450 ml, RR 14 per minute, IE ratio 1:2 and FiO2 1.
Transesophageal echocardiography (TEE) done after induction showed a dilated aortic root of 44 mm x 38 mm (normal < 37mm) 41 and proximal ascending aorta 35 mm x 27 mm (normal is 30 mm) 21 with dissection of the posterior aortic wall from the aortic root to the descending thoracic aorta of 32 mm (normal 18 -22 mm) 21 with thrombus formation at the false lumen.There was also moderate to severe aortic regurgitation with mild mitral and tricuspid regurgitation.Citicholine 1 gm, tranexamic acid 2 g were administered.Nitroglicerine drip, low dose dopamine drip and blood transfusion were started.Median sternotomy commence 29 hours from onset of symptoms or five hours from arrival at the emergency department.Heparin at 3 mg/kg was administered.Activated coagulation time (ACT) level of 375 was achieved before cannulation of the axillary artery, femoral artery and right atrium.ACT determination was done every 30 minutes to maintain a level above 350.
Surgery proceeded with a period of cardiac arrest by infusion of cardioplegic solution into the aortic root.Deep hypothermia at 20°C was achieved by infusion of cold blood using CPB, application of blanket roll and ice pack over the head.After the core temperature of 20C was achieved, innominate artery was clamped.
Blood cardioplegic solution was given in retrograde manner to facilitate the aortic root replacement with a composite valve graft.During this period of time, antegrade cerebral perfusion technique was used to provide blood flow to the brain.Perfusion to other organs was also preserved through femoral artery cannulation Rewarming of the temperature to 28°C was then initiated and maintained during completion of the coronary artery bypass of the right main coronary artery using a distal saphenous vein graft.
All anesthetic agents were given by continuous intravenous infusion.Total DHCA time, clamped/ischemic time and CPB time were 24 minutes, 155 minutes and 190 minutes respectively.
After rewarming to 37 °C, the bypass was gradually terminated.Heparin reversal with protamine was administered intravenously.
The modified Bentall surgery lasted 7 hours.Total blood loss was 1000 cc (maximal allowable blood loss was 252 cc) with total urine output of 1350 cc.Blood products transfused were PRBC of 4 units, FFP of 3 units and platelet concentrate of 5 units.
She was maintained on mechanical ventilator for six hours at the post anesthesia care unit (PACU).Postoperative fetal heart tones could not be appreciated.Pelvic ultrasound showed fetal demise.Expectant management for the intrauterine fetal demise (IUFD) was the best option at this time.
Patient was transferred to coronary care unit sedated but arousable with pain controlled by tramadol infusion and later by oral combination of paracetamol 325 mg and tramadol 37.5 mg.
On 2 nd post op day, left ventricular dysfunction was noted on 2D echo with dyskinesia on the entire interventricular septum and hypokinesia on the anterior left ventricle (LV) free wall with best contraction at the antrolateral and inferolateral LV free wall (EF 33% by Tiechholz and 49% by Simpson's).Dobutamine drip 5-15 mcg/kg/min was started and titrated.Fondaparinux 2.5 mg was also administered subcutaneously as an antithromboembolic agent.Other management includes general liquid diet progressive heart delight, humulin R sliding scale, calcium 600 mg, Vit D 400 IU tablet p.o. and potassium chloride tab 750 mg p.o. Neurologic examinations revealed same as preinduction.
Repeat 2D echo on 4 th post op day showed an improvement in LV function (EF 51% by Simpson's) and wall motion (hypokinesia of entire septum).She stayed at the coronary care unit for 6 days.No evidence of neurologic, nephrologic deficit, pulmonary and cardiac problems was noted. .Patient was discharged with improvement and preferred to be transferred to another hospital for delivery of the fetus.

Discussion
We are presented with a patient with aortic aneurysm with dissection type A. This requires immediate surgical intervention because of 50% risk of rupture. 2,24,32e presence of aortic dissection and systemic features with score ≥7 made our patient fulfill criteria of having Marfan syndrome following the 2010 Revised Ghent nosology criteria (see Appendix B).The aortic dissection in Marfan's syndrome patient usually manifests during pregnancy which happened in this case.
Type A dissection, meaning dissection involving the ascending aorta (Fig. 2) present in the patient, carries the risk of neurologic sequelae when the aorta is clamped.In addition, the presence of more than 50 % stenosis of the left carotid artery, though not yet an indication for carotid endarterectomy, also added to the risk of cerebral ischemia.Thus, cardiopulmonary bypass and deep hypothermic circulatory arrest techniques, defined as the use of systemic hypothermia (core temperature of 14-20°C) 3 and the intentional cessation of the circulation for periods up to 60 minutes 30 , were employed by placing the patient at 20°C to reduce the cerebral metabolic rate and oxygen consumption, and thus minimize the complication of cerebral ischemia.
Recurrence of aortic dissection in this patient is likely to happen especially during subsequent pregnancy. 19,23hus, grafting of the aortic dissection will not be enough.There should also be an aortic valve replacement and reimplantation of the left coronary ostium with a long interposed graft wrapping behind the grafting of the aortic dissection. 38e type A aortic dissection which also disrupted the right coronary artery blood flow (Fig. 3) required the patient to undergo coronary artery bypass graft in addition to the aortic dissection surgery and aortic valve replacement.Thus, the extension of the duration of the surgery is unavoidable.However, the problems did not end there.The patient was also a primi gravid at 28 weeks AOG.Her prenatal check up and work-ups were not available.Referral to the Obstetric department could not find any indication for elective caesarian section at that time.The patient was not in labor.The fetal lung was expected to be immature as surfactant would be released at 30 weeks AOG, at which time could be detected in amniotic fluid. 42Forty eight hours of steroids (dexamethasone every 12 hours for 4 doses or bethametasone every 24 hours for 2 doses) should be administered to accelerate fetal lung maturation. 11However, the emergent nature of the surgical condition could not afford to wait 48 hours.Aspiration of amniotic fluid to detect the presence of surfactant at 28 weeks AOG seemed to have no beneficial effect. 42 elective caesarian section was done in a preterm patient who is not in labor and with very low birth weight fetus with immature lung, the chance of survival of the fetus would be less than 50%. 10leeding could be expected from the uterus during the caesarean section in full term pregnancy with blood loss as much as 500 ml -1000 ml in 75% of women having a caesarean section in the Philippines and more than 1000 ml in 4% of that population. 18Furthermore, the life of the post partum patient would be greatly endangered if the patient would undergo aortic surgery wherein anticoagulants would be administered.
The patient's condition would have more than 45% risk of mortality if not immediately operated. 24An increase of 1-2% mortality was expected for every hour delay of surgery from onset of symptoms. 24e risks and benefits were explained to the patient and the relatives.The family and the physicians agreed to do the aortic surgery to save the life of the pregnant patient without any neurologic sequelae with the hope that the fetus would be able to survive the insult caused by the medical and surgical conditions.The worst possible scenarios were also explained to the relatives.The worst possibility was that the patient and the fetus might not be able to survive the surgery.Another possibility was the patient might survive the surgery but with neurologic sequelae or with kidney problem or with lower extremity paralysis secondary to the clamping of the aorta, carotid stenosis and prolonged surgery.Yet, the more expected possibility was the patient might survive but the fetus might not.
Since the patient was brought to the emergency department 24 hours from onset of symptoms, the patient was immediately operated five hours after admission or 29 hours after onset of symptoms.TEE was done after induction of GEA to determine the final surgery.Ascending aortic replacement, total arch replacement with reattachment of brachiocephalic branches with modified Bentall procedure (the replacement the aortic root and reimplantation the left coronary artery) were chosen to minimize the risk of the recurrence of the later-onset aneurysms and dissection of the aorta which commonly encountered in Marfan syndrome. 23e modified Bentall technique, which was reported by Svensson in 1992, is an aortic root's replacement using a composite valve graft (bileaflet mechanical valve attached to a polyester tube graft) involving a left coronary ostium's reimplantation using Kochoucous's button modification by leaving button's of aortic wall surrounding both coronary arteries, which are then mobilized and sutured to the aortic graft (Fig 4). 38,48 andard cardiopulmonary bypass (heart lung machine) and deep hypothermic circulatory arrest were achieved to facilitate the aortic dissection repair, valve replacement and CABG.Usual cannulation was impossible to use due to the location of the aortic dissection, thus axillary and femoral arteries were used for site of cannulation to maintain blood flow to the brain and other organs.
The patient was extubated six hours post surgery without any neurologic sequelae.However, fetal heart tone could no longer be appreciated post operatively.Thus, though the difficult CABG and aortic surgery can be considered a success, the demise of the fetus intrautero made its success not in toto.
Aware of the all the consequences that might occur, the patient and the relatives appreciated the effort of the team who was able to prevent the worst possibilities that might occur to the patient.

Conclusion
The anesthetic management for modified bentall procedure in a pregnant patient with Acute Type A dissection is very challenging since there are two patients involved, mother and child.The additional risk for higher maternal morbidity which related to Marfan syndrome also made the nature of the event more challenging for any anesthesiologist.
Although the aim is life for both, survival of one without neurologic sequelae is already considered a success.

Figure 1A&B .
Figure 1A&B.MRA of the chest/thoracic (9/29/10) showed aortic aneurysm with dissection at the level of proximal ascending aorta down to the visualized common iliac arteries.

Figure 2 .
Figure 2. Type A aortic aneurysm and dissection at the level of the proximal ascending down to the common iliac arteries (left) and intimal flap from proximal ascending aorta (right)

Figure 3 .
Figure 3. Disruption of the right coronary blood flow (left) and injury to the aortic valve due to aortic dissection causing moderate-severe aortic regurgitation (right)

Figure 4 .
Figure 4. Illustration of the modified Bentall procedure for aortic root replacement, during which buttons of aortic wall surrounding coronary arteries are mobilized and sutured to the aortic graft.(Reprinted from Schwartz's Principles of surgery, 8 th edition, 2004)