Ko Shibata

Open stent-grafting for aortic arch aneurysm is associated with increased risk of paraplegia

BACKGROUND Open surgery using the endovascular stent-graft is a novel technique that lessens the invasiveness of surgery for the aortic arch. However, the outcome of this procedure remains uncertain. METHODS Between November 1996 and July 2000, a total of 19 patients underwent open surgery using an endovascular stent-graft for thoracic aortic aneurysms. There were 15 men (78.9%) and 4 women (21.1%). Patient age ranged from 29 to 82 years (mean 69.3 years, median 74 years). Atherosclerotic thoracic aortic aneurysms were present in 17 patients (89.4%) and aortic dissection in 2 patients (10.5%). RESULTS Two patients (10.5%) died in the hospital and 4 patients (21.1%) presented with paraplegia postoperatively. Among the 4 patients with postoperative paraplegia, 1 case was complicated with intraoperative aortic dissection. The other 3 patients with paraplegia had spinal cord ischemic time of more than 60 minutes and intraoperative body weight gain of more than 4 kg. Of these 3 patients, hemodynamic instability after cardiopulmonary bypass was observed in 1 patient and cholesterin embolus in the anterior spinal artery was found at autopsy in another. On univariate analysis, age greater than 75 years was the only risk factor associated with paraplegia (p < 0.05). Autopsy findings for the 2 patients showed that the Adamkiewicz arteries were not blocked by the stent-graft in either patient. CONCLUSIONS Intraoperative aortic dissection, embolization of the intercostal arteries, long ischemic time of the spinal cord, and excessive weight gain during operation may have been associated with the high incidence of paraplegia after open surgery using the endovascular stent-graft.

Aortopulmonary fistula in pseudoaneurysm after ascending aortic surgery

Clinical Summary A 52-year-old man had undergone, in another hospital, a graft replacement of the ascending aorta and coronary bypass grafting (saphenous vein to the right coronary artery) for acute type A aortic dissection. Gelatin-resorcinol-formaldehyde tissue glue had been used in reinforcement of the dissected aorta in both ends. Nine months after that operation, the patient had dyspnea and mild fever. Computed tomographic (CT) scan showed pseudoaneurysm of the ascending aorta, and he was referred to us. Physical findings included a continuous murmur maximal at the second right intercostal space. Chest radiography showed mild cardiomegaly and enhancement of the right pulmonary vasculature. Transesophageal echocardiography and a new CT scan (Figure 1) revealed a pseudoaneurysm of the ascending aorta, with fistulization to the right pulmonary artery arising from the proximal anastomosis. Aortography confirmed complete occlusion of the vein graft as well as the presence of the aortopulmonary fistula. Right heart catheterization revealed right-sided pressure elevation. When the left ventricular pressure was 74/20 mm Hg, the right atrial pressure was 17 mm Hg, the right ventricular was 34/18 mm Hg, and the pulmonary arterial pressure was 35/16 mm Hg. An oxygen saturation step-up was observed in the pulmonary artery, with 59.8% in the main pulmonary artery and 91.8% in the right pulmonary artery. Because of the risks of repeated median sternotomy, we chose a right thoracotomy to approach the aortic root. We prepared a cryopreserved aortic valve allograft in case of infection. The right fourth intercostal space was opened, and sternal transection and left thoracotomy were included. The femoral artery and the superior and inferior venae cavae were cannulated for cardiopulmonary bypass. An occlusion balloon was inserted into the distal part of the pseudoaneurysm to reduce the degree of aortopulmonary shunting. After systemic cooling, retrograde cardioplegia, and deep hypothermic circulatory arrest, the pseudoaneurysm was incised, and dissection proceeded until the distal part of the aortic graft was crossclamped and systemic circulation was resumed. The defect of the right pulmonary artery wall was 14 mm in diameter; it was closed with the anterior mitral leaflet taken from the aortic allograft. We found dehiscence in the anterior part of the proximal anastomosis, blackened aortic edge, and fragile aortic wall with dissection almost reaching the annulus. There were no findings indicating infection. The left coronary ostium was resected as a button. A Dacron polyester fabric tube composite graft with a mechanical valve was inserted into the aortic root, and the left coronary button was reattached to the graft. During rewarming, the right internal thoracic artery was anastomosed to the right coronary artery (Figure 2). The patient’s postoperative course included pneumonia, which improved with antibiotics, and he was discharged 47 days after operation. Histologic examination of the media of the dissected aorta revealed a homogeneous eosinophilic substance that seemed to be composed of glue, severe calcification, and fibrous tissue with hemosiderin deposition.

Arterial blood gas management in retrograde cerebral perfusion: the importance of carbon dioxide

OBJECTIVES Many interventional physiological assessments for retrograde cerebral perfusion (RCP) have been explored. However, the appropriate arterial gas management of carbon dioxide (CO2) remains controversial. The aim of this study is to determine whether alpha-stat or pH-stat could be used for effective brain protection under RCP in terms of cortical cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2), and distribution of regional cerebral blood flow. METHODS Fifteen anesthetized dogs (25.1+/-1.1 kg) on cardiopulmonary bypass (CPB) were cooled to 18 degrees C under alpha-stat management and had RCP for 90 min under: (1), alpha-stat; (2), pH-stat; or (3), deep hypothermic (18 degrees C) antegrade CPB (antegrade). RCP flow was regulated for a sagittal sinus pressure of around 25 mmHg. CBF was monitored by a laser tissue flowmeter. Serial analyses of blood gas were made. The regional cerebral blood flow was measured with colored microspheres before discontinuation of RCP. CBF and CMRO2 were evaluated as the percentage of the baseline level (%CBF, %CMRO2). RESULTS The oxygen content of arterial inflow and oxygen extraction was not significantly different between the RCP groups. The %CBF and %CMRO2 were significantly higher for pH-stat RCP than for alpha-stat RCP. The regional cerebral blood flow, measured with colored microspheres, tended to be higher for pH-stat RCP than for alpha-stat RCP, at every site in the brain. Irrespective of CO2 management, regional differences were not significant among any site in the brain. CONCLUSIONS CO2 management is crucial for brain protection under deep hypothermic RCP. This study revealed that pH-stat was considered to be better than alpha-stat in terms of CBF and oxygen metabolism in the brain. The regional blood flow distribution was considered to be unchanged irrespective of CO2 management.

Effectiveness of combined blood conservation measures in thoracic aortic operations with deep hypothermic circulatory arrest

BACKGROUND The effectiveness of blood conservation measures for thoracic aortic operations with deep hypothermic circulatory arrest has not yet been documented. METHODS From July 1997 to December 2000, 148 thoracic aortic operations were performed in our department. Sixty-one cases involving patients who underwent elective thoracic aortic operation with deep hypothermic circulatory arrest were reviewed retrospectively. RESULTS Seventeen patients did not meet the criteria for the blood conservation program and were excluded from the present study. Therefore, 44 patients were analyzed in this study. Overall, 50% of patients did not require operative homologous blood transfusion (HBT) and 43% did not require in-hospital HBT. Smaller amounts of autologous donation, greater blood loss, and a longer operation time were independent risk factors for HBT requirement. Among 16 patients who had made an autologous donation of 1,600 mL or greater, 75% did not require intraoperative HBT and 69% did not require in-hospital HBT. The overall perioperative mortality rate was 4.5%. As for postoperative complications, prolonged intubation and postoperative infection were significantly more frequent among patients who required in-hospital HBT. CONCLUSIONS Our combined blood conservation measures were effective in avoiding HBT during major thoracic aortic operations with deep hypothermic circulatory arrest and may have reduced postoperative complications. The amount of the autologous donation was a strong predictor for avoiding HBT.

Elephant trunk in a small-calibre true lumen for chronic aortic dissection: cause of haemolytic anaemia?

OBJECTIVES The elephant trunk technique for aortic dissection is useful for reducing false lumen pressure; however, a folded vascular prosthesis inside the aorta can cause haemolysis. The purpose of this study was to investigate whether an elephant trunk in a small-calibre lumen can cause haemolysis. METHODS Inpatient and outpatient records were retrospectively reviewed. RESULTS Two cases of haemolytic anaemia after aortic surgery using the elephant trunk technique were identified from 2011 to 2013. A 64-year-old man, who underwent graft replacement of the ascending aorta for acute Stanford type A aortic dissection, presented with enlargement of the chronic dissection of the descending aorta and moderate aortic regurgitation. A two-stage surgery was scheduled. Total arch replacement with an elephant trunk in the true lumen and concomitant aortic valve replacement were performed. Postoperatively, he developed severe haemolytic anaemia because of the folded elephant trunk. The anaemia improved after the second surgery, including graft replacement of the descending aorta. Similarly, a 61-year-old man, who underwent total arch replacement for acute Stanford type A aortic dissection, presented with enlargement of the chronic dissection of the descending aorta. Graft replacement of the descending aorta with an elephant trunk inserted into the true lumen was performed. The patient postoperatively developed haemolytic anaemia because of the folded elephant trunk, which improved after additional stent grafting into the elephant trunk. CONCLUSIONS A folded elephant trunk in a small-calibre lumen can cause haemolysis. Therefore, inserting an elephant trunk in a small-calibre true lumen during surgery for chronic aortic dissection should be avoided.

Doppler ultrasonographic identification of the critical segmental artery for spinal cord protection

OBJECTIVE The purpose of this study is to evaluate the possibility of identifying critical segmental arteries (CSAs) based on Doppler ultrasonographic hemodynamics. METHODS In 18 mongrel dogs, the descending aorta was scanned directly with a 5-MHz linear probe through left thoracotomies and the flow velocities in segmental arteries were measured by pulsed Doppler. The aorta was cross-clamped between Th13 and L1, and flow velocity changes were recorded. According to flow increases, segmental arteries were divided into three groups: arteries with the largest flow increase (L-arteries), arteries with the smallest increase (S-arteries) and other arteries (O-arteries). Animals were divided into three groups. One aortic segment including an L-artery or an S-artery was perfused via a temporary shunt during 30-min aortic cross-clamping distal to the left subclavian artery (Group L or Group S) and neurological outcomes were compared with those of animals without shunting (Group N) after 24 and 48 h. RESULTS L-arteries had significantly larger flow increases than S- and O-arteries (74.3+/-33.8, 20.4+/-9.8 and 33.3+/-17.8 cm/s, P<0.01). In Group N, five of the six animals were completely paraplegic (Tarlov Grade 0) and the other was Grade 1. In Group S, four animals were Grade 4 and two were Grade 0 after 24h. However, two animals showed delayed paraplegia. Therefore, four animals were Grade 0 and two were Grade 4 after 48 h. All animals in Group L were neurologically normal (Grade 4) at both after 24h (vs. Group N, P=0.0013) and 48 h (vs. Group N, P=0.0013; vs. Group S, P=0.019). CONCLUSIONS Flow responses to aortic cross-clamping differed among segmental arteries and selective perfusion of L-arteries completely prevented paraplegia. Therefore, L-arteries were considered to be CSAs. Hemodynamic measurement of segmental arterial flow using Doppler ultrasonography could be clinically useful for spinal cord protection during thoracoabdominal aortic surgery.

Cerebral Metabolism of Nitric Oxide during Retrograde Cerebral Perfusion

The aim of this study was to determine whether alpha- or pH-stat protects the brain during deep hypothermic retrograde cerebral perfusion. Fifteen anesthetized dogs on cardiopulmonary bypass were cooled to 18°C under alpha-stat and underwent retrograde cerebral perfusion for 90 minutes under alpha-stat or pH-stat, or underwent antegrade cardiopulmonary bypass under alpha-stat as the control. Cerebral blood flow of the cortex was monitored and serial analyses of blood gases and total nitric oxide oxidation products made. Cerebral blood flow and cerebral metabolic rate for oxygen were significantly higher and plasma levels of nitric oxide oxidation products in the outflow from the brain were significantly lower in retrograde cerebral perfusion under pH-stat than under alpha-stat. This study shows that reduced levels of nitric oxide oxidation products may protect against neuronal damage induced by nitric oxide and that increased cerebral blood flow under pH-stat may lead to a reduction of nitric oxide oxidation products. Under retrograde cerebral perfusion, pH-stat is thus better than alpha-stat for protecting the brain.