Transintercostal-evoked spinal cord potential in thoracic aortic surgery.

BACKGROUND: We have developed a novel method of measuring spinal cord-evoked potentials with stimulation and recording at the intercostal nerves (transintercostal-evoked spinal cord potential: Tic-ESCP). The purpose of this study was to examine the feasibility and accuracy of Tic-ESCP during thoracic aortic surgery. METHODS: In addition to the conventional electrodes (cranial and intrathecal), stimulating and recording electrodes were placed on the intercostal nerves that were located at a cephalad and caudal level relative to the aneurysm after the pleura on the intercostal nerves was opened. Specially designed hook-type electrodes were anchored to the nerves and surroundings atraumatically and fixed on the pleura. The conventional transcranial motor-evoked potential (Tc-MEP) and Tic-ESCP were recorded simultaneously. Eight patients were examined in this study. RESULTS: In all patients, Tic-ESCP could be clearly recorded with biphasic waveforms consisting of first a positive wave and a subsequent negative wave. In all 8 patients, the waveform of Tc-MEP and Tic-ESCP changed during aortic reconstruction. In 2 cases, the waveform of Tc-MEP and Tic-ESCP decreased below 50% of baseline during aortic clamping and the intercostal arteries were reconstructed with no resultant spinal cord injury. In 1 case with a shaggy aorta, Tc-MEP and Tic-ESCP had different values and each evoked potential could have reflected that regional spinal cord infarction and paraplegia had occurred. CONCLUSIONS: Tic-ESCP was clinically feasible and changes were compatible with the conventional Tc-MEP. The Tic-ESCP waveforms were simple and appeared to be specific to the spinal cord within the target range, in contrast to the other evoked potentials which are multimorphic and reflect the amplitudes at the brain and multiple levels of the spinal cord.

New method for absolute spinal cord ischemia protection in rabbits.

OBJECTIVE: This study aims to establish a superior procedure to prevent spinal cord damage after severe spinal cord ischemia during aortic surgery. We examined the synergistic effect of topical hypothermia of the spinal cord combined with radical scavenger infusion into the clamped segment of the aorta to prevent spinal cord damage in an animal model. METHODS: Spinal cord ischemia was induced in rabbits by clamping the aorta between the renal artery and aortic bifurcation for 30 minutes. Rabbits were divided into four groups of 16 each: group I, sham-operated; group II, edaravone (6 mL, 4°C, 1 mg/kg); group III, saline (6 mL, 4°C) with transvertebral cooling pads; group IV, edaravone (6 mL, 4°C, 1 mg/kg) and transvertebral cooling pads. Solutions were injected into the clamped segment of the aorta. Postoperative assessments included the Tarlov score, spinal cord histopathology, and measurement of malondialdehyde levels in the spinal cord tissue. RESULTS: At 48 hours after reperfusion, the mean Tarlov scores in groups I, II, III, and IV were 4.0, 1.5, 1.9, and 4.0, respectively. The mean number of normal motor neurons was significantly higher in groups I (54.1) and IV (53.7) than in groups II (32.8) and III (36.3; P < .001). The mean malondialdehyde level in groups I (19.8 nmol/mL) and IV (22.6 nmol/mL) was significantly lower than in groups II (64.8 nmol/mL) and III (60.9 nmol/mL; P < .001). At 168 hours after reperfusion, the mean Tarlov scores in groups I, II, III, and IV were 4.0, 1.1, 1.3, and 4.0, respectively. The mean number of normal motor neurons was significantly higher in groups I (52.9) and IV (50.8) than in groups II (22.4) and III (25.9; P < .001). The mean malondialdehyde level in groups I (20.7 nmol/mL) and IV (23.4 nmol/mL) was significantly lower than in groups II (68.9 nmol/mL) and III (61.6 nmol/mL; P < .001). CONCLUSION: In a rabbit model with aortic clamping up to 30 minutes, which consistently produces complete paraplegia in rabbits, spinal cord damage was partially reduced by topical cooling with transvertebral cooling pads or the injection of edaravone into the clamped segment of aorta, but was more effectively protected by a combined use of these two strategies.

Cold blood spinoplegia under motor-evoked potential monitoring during thoracic aortic surgery.

OBJECTIVE: Motor-evoked potential monitoring is used to prevent paraplegia during thoracic aortic surgery. Multidetector computed tomography has been used preoperatively to detect the Adamkiewicz artery, but the hemodynamic significance of the Adamkiewicz artery is controversial. This study aims to evaluate whether the multidetector computed tomography-defined Adamkiewicz artery is hemodynamically essential and needs to be reconstructed with cold blood spinoplegia under motor-evoked potential monitoring. METHODS: From 2005 to 2008, both preoperative multidetector computed tomographic analysis and intraoperative neurogenic motor-evoked potential monitoring with cold blood infusion into the clamped segment of the aorta were done in 15 patients. A motor-evoked potential decrease to less than 50% of the initial value at 3 minutes after cold blood infusion determined the hemodynamic significance of the multidetector computed tomography-defined Adamkiewicz artery. Adamkiewicz arteries determined to be essential were reconstructed, and those determined to be nonessential were sacrificed. RESULTS: The Adamkiewicz artery was involved in the clamped segment of the aorta in 11 cases. After cold blood infusion, 8 patients experienced no significant motor-evoked potential decrease, and Adamkiewicz artery ligation was undertaken, whereas a moderate motor-evoked potential decrease was noted in 1 patient, prompting reconstruction. None of these 9 patients had permanent neurologic deficits. In 2 patients, the Adamkiewicz artery was reconstructed based on motor-evoked potential findings, with paraparesis occurring in 1 patient. In 4 patients without Adamkiewicz artery involvement in the clamped segment, there was no neurologic deficit. CONCLUSIONS: Cold blood infusion accelerates motor-evoked potential changes and might enable decision making regarding the need for reconstruction of multidetector computed tomography-defined Adamkiewicz arteries. Cold blood-loaded motor-evoked potential is beneficial to minimize Adamkiewicz artery reconstruction time and limit spinal cord ischemia.

Sodium 4-phenylbutyrate protects against spinal cord ischemia by inhibition of endoplasmic reticulum stress.

OBJECTIVE: Delayed paraplegia after operation on the thoracoabdominal aorta is considered to be related to vulnerability of motor neurons to ischemia. Previous studies have demonstrated the relationship between neuronal vulnerability and endoplasmic reticulum (ER) stress after transient ischemia in the spinal cord. The aim of this study was to investigate whether sodium 4-phenylbutyrate (PBA), a chemical chaperone that reduces the load of mutant or unfolded proteins retained in the ER during cellular stress, can protect against ischemic spinal cord damage. METHODS: Spinal cord ischemia was induced in rabbits by direct aortic cross-clamping (below the renal artery and above the bifurcation) for 15 minutes at normothermia. Group A (n = 6) was a sham operation control group. In group B (n = 6) and group C (n = 6), vehicle or 15 mg/kg/h of sodium 4-PBA was infused intravenously, respectively, from 30 minutes before the induction of ischemia until 30 minutes after reperfusion. Neurologic function was assessed at 8 hours, and 2 and 7 days after reperfusion with a Tarlov score. Histologic changes were studied with hematoxylin-eosin staining. Immunohistochemistry analysis for ER stress-related molecules, including caspase12 and GRP78 were examined. RESULTS: The mean Tarlov scores were 4.0 in every group at 8 hours, but were 4.0, 2.5, and 3.9 at 2 days; and 4.0, 0.7, and 4.0 at 7 days in groups A, B, and C, respectively. The numbers of intact motor neurons at 7 days after reperfusion were 47.4, 21.5, and 44.9 in groups A, B, and C, respectively. There was no significant difference in terms of viable neurons between groups A and C. Caspase12 and GRP78 immunoreactivities were induced in motor neurons in group B, whereas they were not observed in groups A and C. CONCLUSION: Reduction in ER stress-induced spinal cord injury was achieved by the administration of 4-PBA. 4-PBA may be a strong candidate for use as a therapeutic agent in the treatment of ischemic spinal cord injury.

Tumescent local anesthesia for a revascularization of a coronary subclavian steal syndrome.

Tumescent local anesthesia (TLA), originally developed for liposuction, has found widespread application. We report a case of peripheral arterial bypass grafting under TLA. The patient was an 84-year-old female diagnosed as having coronary subclavian steal syndrome caused by proximal left subclavian artery stenosis. Because she had several risk factors for general anesthesia, we performed axilloaxillary artery bypass grafting under TLA and mild sedation. There was no morbidity related to the surgery. The TLA technique may be ideal for performing peripheral arterial bypass grafting if general anesthesia is inappropriate because of cardiac complications.

Right gastroepiploic artery grafting for saphenous vein graft pseudoaneurysm.

Saphenous vein graft pseudoaneurysms are an unusual but potentially fatal complication of coronary artery bypass grafting because of their high risk of rupture or thromboembolism. We experienced the case of a 58-year-old man with a saphenous vein graft pseudoaneurysm with a floating thrombus that had developed 17 years after the initial coronary artery bypass grafting. The prevention of thromboembolism during a surgical procedure has been crucial for this type of operation. We developed the idea of in situ revascularization using the right gastroepiploic artery under the beating heart on cardiopulmonary bypass followed by an aneurysmectomy under an arrested heart.

Surgical treatment of virulent descending necrotizing mediastinitis.

We report a 58-year-old male treated with surgical drainage by mediansternotomy using a pedicled omental flap for descending necrotizing mediastinitis (DNM). The patient recovered from DNM after five months of mechanical respiratory support. In deciding upon the most appropriate surgical approach for mediastinal drainage, the level of infection is a good landmark and should be investigated by CT scan. We also review the 43 cases of successful surgical treatment of DNM reported since 1989 in Japan, including our own patient, who were diagnosed with DNM by CT scan according to the classification proposed by Endo et al., and discuss the most appropriate surgical approach for mediastinitis based on the literature. In the treatment of DNM localized to the upper mediastinal space above the carina, a transcervical approach may be appropriate. In diffuse DNM extending into the lower anterior mediastinum, a mediansternotomy or a thoracotomy may be useful, and in diffuse DNM extending into both the anterior and posterior lower mediastinum, a thoracotomy may be the best approach for debridement of the lower posterior mediastinum, in addition to early complete debridement of the entire cervical area.

A tracheostomy case of aortic valve regurgitation successfully treated by a lower mini-sternotomy technique.

The performance of cardiac surgical procedures via median sternotomy in a patient with a tracheostomy can result in difficult problems, such as mediastinitis, stoma necrosis or inadequate operative exposure. We present a case of successful treatment for aortic valve regurgitation in a patient with a tracheostomy using a T-shaped sternotomy instead of a usual median sternotomy. This approach permitted adequate surgical exposure for cardiopulmonary bypass and aortic valve replacement. After surgery, the patient had a good clinical course without any complications and he was discharged on the 65th postoperative day. We consider this procedure to be applicable in consideration of the favorable results obtained.

Surgical repair of a common atrium in an adult.

We report a rare successful surgical repair of a common atrium (CA) with mild tricuspid valve (TV) regurgitation due to valvular annulus enlargement in a 39-year-old man, who had a complete atrial septum defect (ASD) without the characteristic of an endocardial cushion defect. The left-to-right shunt ratio was 85 percent and the Qp/Qs was 6.7 due to the CA. Left ventriculogram revealed no evidence of typical goose-neck deformity and no mitral valve regurgitation. The operation consisted of making a new atrial septum with an autologous pericardial patch and tricuspid annuloplasty (DeVega) using extracorporeal circulation. There was no evidence of a cleft on the anterior leaflet of the mitral valve or the septal leaflet of the TV. The postoperative echocardiogram showed no residual shunt flow through a new atrial septum and no TV regurgitation, and atrioventricular (AV) dissociation did not occur. We consider this procedure to be widely applicable in consideration of the favorable results obtained after surgical treatment.