Case presentation Cerebral infarction after surgery for acute type I aortic dissection R1 王佳茹

Patient data  Chart number:  Age/Sex: 49 y/o, Male  Date of admission: Sep. 3, 2003  Date of operation: Sep. 3, 2003

Brief history  Chronic hypertension for more than 10 years without regular medical control  Sudden-onset chest pain with radiation to back on the morning of Sep. 3, 2003  He went to ER of En-Chu-Kong H. where CXR was arranged and revealed cardiomegaly and widened mediastinum.

Echocardiography  linear echoes in the ascending aorta are suggestive of dissection of the ascending aorta.  Intimal flap visualized in the ascending and descending aorta.  There is no pericardial effusion  LVEF = 78%

Computed tomography  Ascending aorta, aoric arch and descending aorta are involved.  There is no pericardial effusion  Aortic valves and orifices of coronary arteries are intact.  Abdominal aorta above the level of renal arteries is involved.

Brief history  Under the impression of acute type 1 aortic dissection, he was transferred to our hospital for surgical intervention.

Physical examination  Vital sign: HR 70/min, RR 20/min, BP 197/103 mmHg, BT 37C,  Conscious clear, E4V5M6  Acute ill-looking,  Regular heart beat without murmur  Symmetric and intact peripheral pulse  Difference of BP measured on both arms is prominent.

At OR  BW: 100kg, Hb : 14  ASA classification : IIIe  Set up monitors  Arterial cannulation on both wrists  Induction with fentanyl 250ug, Rapifen 1000ug and pentothal 500mg  Muscle relaxant with Esmeron 100mg initially, and changed to Pavulon thereafter  On Endo and CVP

Maintenance  Gas: isoflurane, initially desflurane, during CPB  O2 combined with air, without N2O  BP control with Perdipine and Millisrol

TEE  DAA, type I, intima tear at aortic arch near brachiocephalic trunk  Mod-severe AR due to paradoxical movement of intimal flap  Brachiocephalic trunk involvement is equivocal. The possibility is very high according to hemodynamic profile. ( R’t arm 86/65 mmHg while L’t arm 130/70 mmHg)

 Median sternotomy is performed, the patient is placed on CPB.  Cannulation of Right axillary artery, SVC and IVC  Prime with albumin, lactate Ringer’s, solumedrol, 20% Mannitol and Sod. Bicarbonate

 After systemic hypothermia to 15°C, Pentothal was given and circulatory arrest was started.  The head is covered with ice bags

OP finding  Good LV contractility  No pericardial effusion  AsAo dissection: intimal tear at lesser curvature side of aortic arch  AsAo about 5cm in diameter with eccymosis  Pre-op AR: moderate,

During circulatory arrest  Retrograde cerebral perfusion via SVC was failed  Intermittent antegrade cerebral perfusion via right axillary cannula, with a balloon occluder placed in brachiocephalic artery, was performed during distal aortic anastomosis with an open technique.

During circulatory arrest  Ascending aortic grafting with 30 mm hemashield vascular graft was performed.  After distal anastomosis was completed, the vascular graft was clamped; systemic perfusion was restarted, and rewarming was done.  Aortic valve suspension and proximal anastomosis were done during rewarming.

At OR  The patient was weaned from CPB successfully, and he was send to SICU for post-op care.

Duration  Partial bypass time: 5 hrs and 39 mins  Total bypass time: 5 hrs and 18 mins  Aorta X-clamp time: 2 hrs and 46 mins  Circulatory arrest time: 1 hr and 10 mins

Post-op condition  Focal seizure and generalized seizure  Glasgow Coma Scale: E1VtM4  CT of head revealed decreased density with loss of gray-white matter differentiation at Right fronto-temporal lobe, and Right side MCA infarction with brain edema was impressed.

Post-op condition  Fever  Acute renal failure, r/o nephrotoxicity of aminoglycoside related. -> CVVH  DIC  Expire on 9/30

Discussion

Classification of aortic dissection

Surgery on the ascending aorta  median sternotomy and CPB  concomitant aortic valve replacement and coronary reimplantation ( Bentall precedure)

Surgery involving the aortic arch  median sternotomy and CPB with deep hypothermic circulatory arrest (DHCA)  Achieve optimal cerebral protection with systemic and topical hypothermia.  Hypothermia to 15°C, thiopental infusion to maintain a flat EEG, methylprednisolone or dexamethasone, mannitol, and phenytoin are also commonly used.

Surgery involving the descending thoracic aorta  Left thoracotomy without CPB  One-lung anesthesia greatly facilitates surgical exposure and reduces pulmonary trauma from retractors.

Brain protection

 The major complications associated with ascending/arch repair are stroke and encephalopathy.  The incidence of postoperative stroke ranged from 7-15% after thoracic aortic surgery with DHCA, and most of them are embolic in origin.  The major risk factors are circulatory arrest time and whether the transverse arch is involved.

Brain protection  Goals are to optimize CPP, decrease metabolic requirements, and possibly block mediators of cellular injury.  The most effective strategy is prevention.

Surgical consideration

Deep Hypothermic Circulatory Arrest (DHCA)  Permitting a field free of blood and cannulas, allowing thorough inspection of the aneurysm and a careful open distal anastomosis  Reducing the metabolic rate for oxygen, promoting preferential organ perfusion, and increasing tissue oxygen extraction

Deep Hypothermic Circulatory Arrest (DHCA)  Cooling to 10-13°C in esophagous  O2 sat. in the jugular venous bulb > 95%, indicating maximal metabolic suppression.  Cooling > 30mins to prevent a gradual upright temp. and the intracranial temp. should be protected by packing the head in ice.

Deep Hypothermic Circulatory Arrest (DHCA)  Gradual rewarming and avoidance of high perfusion temp. are essential.  A duration of DHCA exceeding 25 mins has been shown to produce temporary neurologic dysfunction. from J. Toracic cardiovascular surgery March,2003

Deep Hypothermic Circulatory Arrest (DHCA)

 DHCA was demonstrated to have longer electroencephalographic recovery times and a higher incidence of clinical seizures in the early postoperative period. from Miller

During deep Hypothermic Circulatory Arrest (DHCA)

Retrograde cerebral perfusion  Oxygenated blood is perfused in a retrograde direction through the superior vena cava and the internal jugular veins and to the brain.  providing continued cerebral cooling, delivering nutrition to the brain and flushing out cerebral emboli

Retrograde cerebral perfusion  Too little capillary flow occurs during RCP (even with occlusion IVC) to confer any meaningful metabolic benefit even during deep hypothermia.  Long durations of RCP are associated with high rates of temporary neurologic dysfunction and an increased risk of stroke and death after aortic surgery. from J. Toracic cardiovascular surgery March,2003

Antegrade cerebral perfusion  Total arch replacement using antegrade selective cerebral perfusion with right axillary artery perfusion is a safe and useful alternative for brain protection in total arch replacement. Eur J Cardiothorac Surg 2003;23:

Antegrade cerebral perfusion  It allows a much longer interval of safe circulatory arrest, since the supply of nutrients and oxygen allows maintenance of appropriate level of oxygen metabolism at hypothermic temporature. Ann Thorac Surg 2002;73:

Antegrade cerebral perfusion  If the total time necessary for aortic arch repair requiring arrest is moderately long, between 40 and 80 mins, the incidence of temporary neurologic dysfunction is clearly lower with ACP than any other alternative. from J. Toracic cardiovascular surgery March,2003

Anesthetic considerations

Monitor  arterial cannula  thermodilution PAC  TEE  EEG  transcranial Doppler  transcranial oximetry

Anesthetic considerations  Prophylactic thiopental infusion ( completely suppressing electroencephalographic activity)  Prior to DHCA, corticosteroid (methylprednisolone 30mg/kg), mannitol (0.5 g/kg), and phenytoin (10-15mg/kg) are also usually administered.  The head is covered with ice bags.

Anesthetic considerations  Nitrous oxide is to be avoided because of its expansion of air emboli  hyperglycemia should be avoided  maintain serum glucose in the 100 to 250 mg/dL range.

Barbiturate  reduce CMR  inhibit free radical formation  reduce Ca 2+ influx,,  potentiate GABAergic activity,  enhance cyclic AMP production,  delay the loss of inotropic glutamate receptor- mediated transmembrane electrical gradients  reduce glucose transport into cells,  block Na + channels,  reduce glutamate, aspartate, lactate, and catecholamines ANESTHESIOLOGY 1998;89:

Steroid  Timing of steroid treatment is important for cerebral protection during CPB and circulatory arrest, different timing of steroid administration results in different inflammatory mediator response.  Steroid in CPB prime is not significantly better than no steroid treatment, while systemic steroid pre-treatment significantly decreases systemic manifestation of inflammatory response and brain damage. Eur J Cardiothorac Surg 2003;24:

Steroid  Systemic steroid pretreatment significantly reduced total body edema and cerebral vascular leak and was associated with better immunohistochemical indices of neuroprotection after DHCA. Ann Thorac Surg 2001;72:

The end