Case report
A 50 year old male weighing 75 kg was transferred to our center for sudden chest pain lasting for 35 hours. He had an eight-year history of hypertension, but did not receive regular medical treatment. He had no known allergies, but had suffered from intermittent asthma for four years, treated with an albuterol inhaler, and theophylline irregularly. His last hospitalization was 13 months ago. He was febrile at 37.8 degree centigrade. His blood pressure was 65/45 mmHg, the heart rate was 97 beat per minute, and the central venous pressure was 20 mmHg. The distal skin was pale and cold. He had a normal neurological exam. The blood routine analysis showed that a white blood cell count of 18.2*109/L, and a neutrophil frequency of 86.4 percent. Computer tomography angiography (CTA) found a large tear on the ascending aorta, which extended to the common iliac artery, and presence of massive pericardial fluid and patchy exudation in both lungs. Pneumonia was diagnosed by fever, the blood routine and CT scans. Transthoracic echocardiography reconfirmed diagnosis of TAAD, and revealed massive pericardial fluid, and mild aortic valve regurgitation. The left ventricular ejection fraction was 50%. Considering the unstable dynamics, the patient was sent to the operating room immediately for emergency surgery. Two million units of Penicillin was given intravenously before he was sent to the operating room.
For premedication, 10 mg of morphine and 1 mg of penehyclidine hydrochloride (anticholinergic drugs) was given intramuscularly, and 5 mg of dexamethasone and 0.25 g of aminophylline were given intravenously. Anesthesia was achieved with fentanyl, midazolam, atracurium besylate and isoflurane. After tracheal intubation, the lungs were clear to auscultation, and peak inspiratory pressure was 18 mmHg. Arterial blood gas analysis revealed no specific abnormalities. After median sternotomy, institution of CPB proceeded uneventfully. Then the aortic root repair and ascending aorta replacement was performed. When the rectal temperature decreased to 23℃, deep hypothermia circulation arrest (DHCA) and antegrade selective cerebral perfusion (SCP) was used during the procedure of total arch remodeling by a triple-stent graft implantation as we have previously described (14). After proximal and distal anastomoses complete the crossclamp was removed, rewarming was started. The aortic cross-clamp time was 54 minutes, and the total circulatory arrest time was five minutes, while the SCP time was 20 minutes. When mechanical ventilation was resumed, expiratory wheezing was heard, and the airway pressure was elevated to 50 mmHg. In addition, the lungs remained inflated. After a few minutes, the lungs over-expanded and bulged into the mediastinum.
The ventilator (Infinity C700 for IT, Drager medical GmbH, Germany) was carefully checked and was found to be working satisfactorily. A suction catheter was easily passed through the endotracheal tube, and no secretions were removed. The lungs deflated when they were disconnected from ventilator. However, they re-inflated after the ventilation was resumed, even though the inspiratory pressure was lower down to 5 mmHg. Fiber optic bronchoscopy was performed, and no tracheobronchial abnormality or obstruction was found. The left atrial pressure was 7 cm H2O. Hemodynamics were stable and transesophageal echocardiogram confirmed normal biventricular function. No urticaria, skin erythema or edema were present and an initial diagnosis of severe bronchospasm was made.
To alleviate bronchospasm, ventilation with isoflurane was begun. Intravenous amino-phylline 0.5 g and methylprednisolone 0.5 g was given, followed by isoproterenol and metaproterenol inhalation by the intratracheal route. 0.1ug*kg-1*min-1 of epinephrine was continuously infused intravenously. However, the lungs showed sustained inflation for 60 minutes. Considering the long CPB time, VV- ECMO was performed. The outflow cannula was set in the right femoral vein, and the inflow site was the right jugular internal vein. A Quadrox oxygenator and a Rotaflow Centrifugal pump (Maquet, Hirrlingen, Germany) were connected to the extra-corporeal circuit. The flow rate was set at 3.5 L/min, and the fraction of inspired oxygen was 40 percent. The ventilator was then temporarily stopped, following which, the lungs were found to deflate gradually. Next, ventilation was resumed under the pressure controlled mode, and the peek inspiratory pressure was set as 10 mmHg. The positive end expiratory pressure was set at 5 mmHg to prevent the collapse of the alveoli. The patient was stabilized hemodynamically, and the patient was weaned off CPB. Blood gas analysis revealed that the partial pressure of oxygen was 175 mmHg, and the partial pressure of carbon dioxide was 40 mmHg. After careful hemostasis and sternal closure, the patient was the sent to the adult intensive care unit (ICU). While at the ICU, antibiotic therapy was continued. Methylprednisolone 80mg was given every eight hours during the first 48 hours. Then the dose was reduced gradually in 3 days. A bronchodilator was used for inhalation every four hours. Eight hours later, the inspiratory pressure of the ventilator was set to 18 mmHg with stable hemodynamics. ECMO was weaned 26 hours later without hemorrhagic complications. The patient was weaned from the mechanical ventilator and extubated four days post-operatively. The remainder of the patient’s hospital stay was otherwise uneventful, and he was discharged 12 days post-surgery.