Radial artery vs saphenous vein grafts for sequential coronary bypass grafting as a second conduit for the left coronary territory.

OBJECTIVE: Although the radial artery graft has an adaptive property to flow demand, its flow characteristics in aorto-coronary sequential bypass grafting are not well elucidated. We evaluated the differences between the vein and radial artery grafts in the patency and the transit time flow meter-derived parameters (flow and pulsatile index), according to the stenosis rate of terminal target vessels and the number of anastomoses, in sequential bypass grafting to the left coronary territories as a second conduit. METHODS: We analyzed 222 patients who underwent isolated on-pump beating coronary artery bypass grafting with an aorto-coronary bypass to the left coronary territory. The patients were divided into radial artery group (n = 154) and vein graft group (n = 68). Sequential bypass was performed 1n 171 patients (127 radial arteries, 44 veins). RESULTS: Flow of the radial artery grafts was lower than that of the vein grafts (40.9 ± 22.3 vs 47.5 ± 23.8 mL/min, p = 0.044), while it became higher as the number of anastomoses per graft increased (1: 28.9 ± 16.3 vs 2: 40.9 ± 19.9 vs 3: 55.8 ± 27.5, p < 0.001). The patency of radial artery grafts was better than that of vein grafts (98.0% vs 92.6%, p = 0.010; p < 0.001 after propensity score weighting). CONCLUSIONS: Although intraoperative flow rate of the radial artery graft is lower, it has sufficient flow reserve for sequential bypass grafting, and its early patency is high enough. Radial artery is suitable for sequential bypass grafting to the left coronary territories as a second arterial conduit.

Left upper lobectomy with combined distal aortic arch and left subclavian artery resection after neoadjuvant chemoradiotherapy for locally advanced lung squamous cell carcinoma.

T4 locally advanced non-small cell lung cancer (NSCLC) is a heterogeneous group with a great variety of involved organs and is associated with a poor prognosis. However, appropriately selected patients benefit from surgical resection. The surgical indication must be carefully considered based on the risk-benefit between high surgical stress and expected prognosis, particularly in cases with probable aortic involvement. Here, we report a long-term survival case of left upper lobe squamous cell carcinoma, in which lobectomy and combined distal aortic arch and left subclavian artery resection achieved a complete resection after induction chemoradiotherapy (CRT). Appropriate patient selection considering expected prognosis, induction CRT and complete resection under well-planned cardiopulmonary bypass are essential to achieve a long-term survival on T4 NSCLC with a probable aortic involvement.

Etiology of renal failure influences the outcome of heart valve replacement in chronic dialysis patients.

Life expectancy of the chronic dialysis patients depends upon the underlying renal disease, but its influence on the outcome of heart valve replacement has not been studied. We aimed to elucidate the difference in the early and midterm results of heart valve replacement according to the etiology of renal diseases. We retrospectively analyzed 17 patients on chronic dialysis who underwent heart valve replacement from 2002 to October 2009. Underlying renal disease was primary in ten patients (glomerulonephritis 8, others 2) and secondary in seven (nephrosclerosis 4, diabetic nephropathy 3). Mean age was 61 ± 10 for primary and 67 ± 7 for secondary renal diseases. Mean duration of dialysis was 18 ± 6 years for primary and 9 ± 9 for secondary renal diseases (p = 0.02). In the aortic position, mechanical valves were used in 12 patients and bioprostheses in three. In the mitral position, mechanical valves were used in all four. Deep hypothermic operation was required for severe aortic calcification in five (primary 5). Mean follow up period was 23 ± 18 months. There were two in-hospital deaths in patients with primary renal disease. Three-year survival rate including hospital deaths, on the other hand, was higher for primary renal diseases (80%) than secondary ones (34%). Despite elevated perioperative risk due to consequence of longer duration of dialysis, midterm survival of patients with primary renal diseases seemed better than for those with secondary renal diseases. These results may help the choice of heart valve prosthesis in chronic dialysis patients.

Bipolar transesophageal thoracic spinal cord stimulation: A novel clinically relevant method for motor-evoked potentials.

OBJECTIVE: Although transesophageal motor-evoked potential elicited by monopolar cervical cord stimulation is more stable and rapid in response to ischemia than transcranial motor-evoked potential in canine experiments, direct cervical alpha motor neuron stimulation precludes clinical application. We evaluated a novel stimulation method using a bipolar esophageal electrode to enable thoracic cord stimulation. METHODS: Twenty dogs were anesthetized. For bipolar transesophageal stimulation, the interelectric pole distance was set at 4 cm. Changes in amplitude in response to incremental stimulation intensity (100-600 V) were measured to evaluate stability. Spinal cord ischemia was induced by aortic balloon occlusion at the T8 to T10 level for 10 minutes to evaluate response time or at the T3 to T5 level for 25 minutes to evaluate prognostic value. Neurological function was evaluated using the Tarlov score at 24 and 48 hours postoperatively. RESULTS: Bipolar transesophageal stimulation was successful in all animals and their forelimb waveforms were identical to those after transcranial stimulation. The minimum stimulation intensity to produce >90% of the maximum amplitude was significantly lower in both monopolar and bipolar transesophageal stimulation than in transcranial stimulation (n = 5). Time to disappearance and recovery (>75%) of the hindlimb potentials were significantly shorter by both monopolar and bipolar transesophageal stimulation than by transcranial stimulation (n = 5). Correlation with neurological outcomes was comparable among all stimulation methods (n = 10). CONCLUSIONS: Motor-evoked potential can be elicited by bipolar transesophageal thoracic cord stimulation without direct cervical alpha motor neuron stimulation, and its stability and response time are comparable to those elicited by monopolar stimulation.

Clinical feasibility and safety of transoesophageal motor-evoked potential monitoring.

OBJECTIVES: Canine experiments have shown that transoesophageal motor-evoked potential monitoring is feasible, safe and stable, with a quicker response to ischaemia and a better prognostic value than transcranial motor-evoked potentials. We aimed to elucidate whether or not these findings were clinically reproducible. METHODS: A bipolar oesophageal electrode mounted on a large-diameter silicon tube and a train of 5 biphasic wave stimuli were used for transoesophageal stimulation. Results of 18 patients (median age 74.5 years, 13 males) were analysed. RESULTS: There were no mortalities, spinal cord injuries or complications related with transoesophageal stimulation. Transcranial motor-evoked potential could not be monitored up to the end of surgery in 3 patients for unknown reasons, 2 of whom from the beginning. Transoesophageal motor-evoked potential became non-evocable after manipulation of a transoesophageal echo probe in 2 patients. Strenuous movement of the upper limbs during transoesophageal stimulation was observed in 3 patients. In 14 patients who successfully completed both monitoring methods up to the end of surgery (11 thoraco-abdominal and 3 descending aortic repair), the final results were judged as false positives in 6 by transcranial stimulation and in 1 by transoesophageal stimulation. The stimulation intensity was significantly lower and the upper limb amplitude was significantly higher by transoesophageal stimulation, while the lower limb amplitude was comparable. CONCLUSIONS: Transoesophageal motor-evoked potential monitoring is clinically feasible and safe with a low false positive rate. A better electrode design is required to avoid its migration by transoesophageal echo manipulation. Further studies may be warranted. CLINICAL REGISTRATION NUMBER: UMIN000022320.

Japanese perspective in surgery for thoracoabdominal aortic aneurysms.

OBJECTIVE: Operative mortality and morbidity after thoracoabdominal aortic surgery remain high. We report our strategy and outcomes, especially those of spinal cord protection. METHODS: Outcomes of 178 patients (age: 26-88 years) who underwent thoracoabdominal aortic replacement were retrospectively analyzed. 65 had aortic dissection, 14 had infected aneurysms, and 22 presented with rupture. Operations were non-elective in 24 and redo through re-thoracotomy in 21. Extent of replacement was Crawford-I in 39, II in 26, III in 78, and IV in 35. Staged repair was recently preferred, which resulted in decrease in extent II repair and increase in redo since 2009. Operations were performed under distal aortic perfusion and multi-segmental sequential repair to maximize collateral blood flow, and deep hypothermic circulatory arrest was preserved for those requiring open aortic anastomosis (n = 20). A total of 166 separate grafts were used for intercostal reconstruction in 88 patients, which was guided by preoperative feeding artery localization. Their patency was studied by postoperative MD-CT in 74 patients for 145 grafts. RESULTS: There were 3.9% hospital mortality and 5.1% spinal cord injury. Preoperative feeding artery localization resulted in reduced number of reconstruction and improved patency, and grafts connecting to the feeding artery were patent in 92%. Results of redo operations were not different (no mortality and spinal cord injury) from the de novo operations. CONCLUSIONS: Our concept of spinal cord protection, which was based on selective intercostal reconstruction while maximizing spinal cord collateral blood flow, seems justified.

Interleukin-1 receptor antagonist attenuates the severity of spinal cord ischemic injury in rabbits.

OBJECTIVE: Thoracic and thoracoabdominal aortic surgery is sometimes complicated by subacute or delayed paraplegia. Pro-inflammatory cytokine interleukin-1 (IL-1) beta has been implicated in extensive inflammation and progressive neurodegeneration after ischemia. Using a rabbit model, we investigated the neuroprotective effects of IL-1 receptor antagonist (IL-1ra) in a temporal fashion. METHODS: Spinal cord ischemia was induced by aortic cross-clamping in New Zealand White rabbits. The animals were assigned to three groups. Group C (n = 20) received saline (0.2-mL) and Group I (n = 20) received IL-1ra (200-microg/0.2-mL) intrathecally just after reperfusion. Group S (n = 3) underwent sham operation without aortic occlusion. We assessed the neuroprotective effects of IL-1ra by evaluating neurological function, histopathological changes, and in-situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL staining). We also measured the levels of Nitric Oxide (NO) and S100beta in cerebrospinal fluid (CSF). Each evaluation was performed sequentially within 120 hours after reperfusion. RESULTS: Group C showed progressive deterioration of motor function which became statistically significant from 48 hours after the onset of reperfusion (P < .05, P < .01, P < .001, P < .001 at 48, 72, 96, and 120 hours, respectively). Compared to Group C, a higher number of viable neurons was observed with less severe spinal cord injury in Group I (P < .01, .05 and .05 at 24, 72, and 120 hours, respectively). TUNEL-positive neurons were also significantly reduced by the administration of IL-1ra (P <.01 and .05 at 24, and 120 hours, respectively). The difference between Group C and Group I with regard to NO was significant at 72 and 120 hours (P < .05), while that in terms of S100beta was significant only at 24 hours (P < .05). CONCLUSIONS: Administration of IL-1ra attenuates spinal cord ischemic-reperfusion injury as evidenced by reducing both neuronal necrosis and apoptosis.

Carotid stenosis with impaired brain flow reserve is associated with an increased risk of stroke in on-pump cardiovascular surgery.

OBJECTIVES: To prevent haemodynamic stroke during cardiovascular surgery in patients with carotid stenosis, we routinely evaluated magnetic resonance angiography and selectively evaluated brain perfusion single-photon emission computed tomography with acetazolamide challenge. Off-pump surgery was preferred when cerebral blood flow reserve was impaired. This strategy's usefulness was investigated. METHODS: Among the 1059 consecutive patients who underwent preoperative carotid screening by magnetic resonance angiography, 84 (7.9%) patients had >50% stenosis; 45 of them underwent brain single-photon emission computed tomography. The severity of cerebral blood flow compromise was estimated by the proportion of Stage 2 area in the affected territory, in which both resting blood flow (<32 ml/min) and flow reserve (<10%) were reduced. RESULTS: Perioperative stroke occurred in 1.7% overall (18/1059), in 6% (5/84) of those with carotid stenosis and in 1.3% (13/975) of those without stenosis (P = 0.010). On subgroup analysis, carotid stenosis was associated with an increased risk of stroke in the on-pump surgery group [n = 949, 5/59 (9%) with stenosis vs 11/890 (1.1%) without stenosis, P = 0.002], while it was not in the off-pump group [n = 110, 0/25 (0%) with stenosis vs 2/85 (2%) without stenosis, P = 0.59]. With respect to the role of acetazolamide single-photon emission computed tomography, 2 of the 4 patients with Stage 2 area >10% undergoing on-pump surgery without preceding carotid revascularization developed stroke, while none of the 21 patients with Stage 2 area <10% undergoing on-pump surgery developed stroke (P = 0.020). CONCLUSIONS: Carotid stenosis is a risk factor for perioperative stroke in on-pump surgery. Patients with large Stage 2 area (>10%) are at increased risk of perioperative stroke when on-pump surgery is performed.

How do we manage the gastrectomy for gastric cancer after coronary artery bypass grafting using the right gastroepiploic artery? Report of two cases and a review of the literature.

BACKGROUND: Recently, the right gastroepiploic artery (RGEA) has been used in coronary artery bypass grafting (CABG) as an alternative arterial graft. Unfortunately, an increased incidence of gastric cancers has been reported after CABG using the RGEA. Handling of the RGEA during gastrectomy in these patients may cause lethal complications, which sometimes reduces the feasibility of curative dissection of lymph nodes at the base of the graft. CASE PRESENTATIONS: We describe two cases of gastric cancer undergoing gastrectomy after CABG with the use of RGEA. To avoid the potentially fatal coronary event during gastrectomy, safe handling of the conduit including preparations for injuries and prevention of vessel spasm was performed in both cases, accompanied by an adequate monitoring of the systemic circulation. Intraoperative frozen section examination showed no lymph node metastasis around the graft in any of the cases; therefore, complete lymph node dissection at the base of the graft was not undertaken. No complications occurred during the operation. In addition to these two cases, twenty-four cases reported in the literatures were reviewed (a total of 26 cases). Ten early and 16 advanced gastric cancers were included. Among the 16 advanced gastric cancer cases, an alternative graft was employed in 8 due to the resection of an original graft to complete lymph node dissection. Mere handling of a graft often caused lethal complications suggesting that the operation should be completed by isolation of the graft. A pedicled graft harvesting via the ante-gastric route was popular. However, a skeletonized harvesting with resection of the pyloric branches of the RGEA would be better because this would interrupt the original lymph flow, which could eliminate the need for lymph node dissection and graft isolation. Among the 10 cases having early gastric cancers, 6 were found within 1.5 years after CABG. Early detection in these 6 cases was possible due to the use of gastric fiberscopic examination before and after CABG, which gave them opportunities to receive a less extensive operation such as endoscopic mucosal resection. CONCLUSION: Adequate intraoperative care as well as an optimal lymph node dissection considering the graft harvesting method at the first CABG leads to successful gastrectomy after CABG using the RGEA graft. Therefore, this operation should be carried out with careful management by both gastrointestinal and cardiovascular surgeons.

Spinal cord ischaemia after endovascular aneurysm repair.

We report the case of a patient who developed paraparesis 2 days after endovascular aneurysm repair for a right common iliac aneurysm. The patient had undergone thoracic endovascular aortic repair. The left subclavian artery was occluded, but the left internal iliac artery was preserved. The patient fully recovered from the paralysis within 3 months. This case illustrates the importance of collateral blood supply to the spinal cord from the lumbosacral region, especially when other sources are occluded.

Valve-sparing aortic root replacement for a prolapsing asymmetric valve.

Valve-sparing aortic root replacement remains challenging for patients with eccentric severe aortic regurgitation when the cusps are totally asymmetric. We report a case of successful reimplantation operation for such a lesion. Because free margin lengths from commissure to Arantius body of the adjacent two cusps were matched while inter-commissural distances were totally different, right coronary cusp prolapse was corrected by asymmetrically aligning the position and height of three commissures without cusp plication.

Characterizing saccular aortic arch aneurysms from the geometry-flow dynamics relationship.

OBJECTIVE: Low wall shear stress (WSS) has been reported to be associated with accelerated atherosclerosis, aneurysm growth, or rupture. We evaluated the geometry of aortic arch aneurysms and their relationship with WSS by using the 4-dimensional flow magnetic resonance imaging to better characterize the saccular aneurysms. METHODS: We analyzed the geometry in 100 patients using multiplanar reconstruction of computed tomography. We evaluated WSS and vortex flow using 4-dimensional flow magnetic resonance imaging in 16 of them, which were compared with 8 age-matched control subjects and eight healthy young volunteers. RESULTS: Eighty-two patients had a saccular aneurysm, and 18 had a fusiform aneurysm. External diameter/aneurysm length ratio and sac depth/neck width ratio of the fusiform aneurysms were constant at 0.76 ± 0.18 and 0.23 ± 0.09, whereas those of saccular aneurysms, especially those involving the outer curvature, were higher and more variable. Vortex flow was always present in the aneurysms, resulting in low WSS. When the sac depth/neck width ratio was less than 0.8, peak WSS correlated inversely with luminal diameter even in the saccular aneurysms. When this ratio exceeded 0.8, which was the case only with the saccular aneurysms, such correlation no longer existed and WSS was invariably low. CONCLUSIONS: Fusiform aneurysms elongate as they dilate, and WSS is lower as the diameter is larger. Saccular aneurysms dilate without proportionate elongation, and they, especially those occupying the inner curvature, have higher and variable sac depth/neck width ratio. When this ratio exceeds 0.8, WSS is low regardless of diameter, which may explain their malignant clinical behavior.

Aorto-right atrial fistula following acute type A aortic dissection repair.

This report describes a rare case of aorto-right atrial fistula caused by rupture of a huge pseudoaneurysm that developed at the proximal aortic anastomotic site after total aortic arch replacement for acute type A aortic dissection. Preoperative aortography revealed that the fistula communicated with the right heart, but it was intraoperative Doppler transesophageal echocardiography that confirmed its course into the right atrium. Repeat total aortic arch replacement with concomitant direct closure of the fistula was performed successfully. The underlying cause of the pseudoaneurysm was the dehiscence of sutures at the proximal aortic anastomotic site, probably due to gelatin-resorcin-formaldehyde glue.

Transesophageal versus transcranial motor evoked potentials to monitor spinal cord ischemia.

OBJECTIVES: We have previously reported that transesophageal motor evoked potential is feasible and more stable than transcranial motor evoked potential. This study aimed to investigate the efficacy of transesophageal motor evoked potential to monitor spinal cord ischemia. METHODS: Transesophageal and transcranial motor evoked potentials were recorded in 13 anesthetized dogs at the bilateral forelimbs, anal sphincters, and hindlimbs. Spinal cord ischemia was induced by aortic balloon occlusion at the 8th to 10th thoracic vertebra level. In the 12 animals with motor evoked potential disappearance, occlusion was maintained for 10 minutes (n = 6) or 40 minutes (n = 6) after motor evoked potential disappearance. Neurologic function was evaluated by Tarlov score at 24 and 48 hours postoperatively. RESULTS: Time to disappearance of bilateral motor evoked potentials was quicker in transesophageal motor evoked potentials than in transcranial motor evoked potentials at anal sphincters (6.9 ± 3.1 minutes vs 8.3 ± 3.4 minutes, P = .02) and hindlimbs (5.7 ± 1.9 minutes vs 7.1 ± 2.7 minutes, P = .008). Hindlimb function was normal in all dogs in the 10-minute occlusion group, and motor evoked potentials recovery (>75% on both sides) after reperfusion was quicker in transesophageal motor evoked potentials than transcranial motor evoked potentials at hindlimbs (14.8 ± 5.6 minutes vs 24.7 ± 8.2 minutes, P = .001). At anal sphincters, transesophageal motor evoked potentials always reappeared (>25%), but transcranial motor evoked potentials did not in 3 of 6 dogs. In the 40-minute occlusion group, hindlimb motor evoked potentials did not reappear in 4 dogs with paraplegia. Among the 2 remaining dogs, 1 with paraparesis (Tarlov 3) showed delayed recovery (>75%) of hindlimb motor evoked potentials without reappearance of anal sphincter motor evoked potentials. In another dog with spastic paraplegia, transesophageal motor evoked potentials from the hindlimbs remained less than 20%, whereas transcranial motor evoked potentials showed recovery (>75%). CONCLUSIONS: Transesophageal motor evoked potentials may be superior to transcranial motor evoked potentials in terms of quicker response to spinal cord ischemia and better prognostic value.

NS-7, a novel Na+/Ca2+ channel blocker, prevents neurologic injury after spinal cord ischemia in rabbits.

OBJECTIVE: We investigated the neuroprotective effect of NS-7 (4-[4-fluorophenyl]-2-methyl-6- [5-piperidinopntyloxy] pyrimidine hydrochloride), a novel Na(+)/Ca(2+) channel blocker, on transient spinal cord ischemia in rabbits. METHODS: Spinal cord ischemia was induced in New Zealand white rabbits by means of infrarenal aortic occlusion for 20 minutes. Four experimental groups were enrolled. A sham group (n = 3) underwent the same operation without aortic occlusion. A control group (n = 7) received only saline before occlusion. Group A (n = 8) received NS-7 (1 mg/kg) 15 minutes before ischemia, and group B (n = 8) received NS-7 (1 mg/kg) at the onset of reperfusion. Neurologic function was assessed 24 and 48 hours after the operation with modified Tarlov criteria. Spinal cords were harvested for histopathologic examination and in situ terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL staining). Spinal cord infarction was investigated with 2, 3, 5-triphenyltetrazonlium chloride staining. RESULTS: Tarlov scoring demonstrated marked improvement in both group A and group B compared with the control group at 24 and 48 hours after the operation. Minimal histologic changes were found in lumbar spinal cords of the 2 NS-7-treated groups, whereas severe neuronal necrosis was shown in the control group. TUNEL-positive neurons and the infarct size of lumbar spinal cords were significantly reduced by NS-7 administered both before ischemia and at the onset of reperfusion. No significant difference was noted between group A and group B in terms of spinal cord protection. CONCLUSION: These results indicate that NS-7 protects the spinal cord against ischemic injury by preventing both neuronal necrosis and apoptosis.

Endarterectomy and graft replacement of severely calcified (porcelain) ascending aorta with coronary ostial involvement in a patient requiring aortic valve replacement.

We report a successful aortic valve replacement within an extensively calcified (porcelain) aorta, involving the left coronary artery ostium. Clamping such an aorta can result in embolization, dissection, and mural laceration. A 72-year-old female presented with a severely calcified and stenotic aortic valve with a peak pressure gradient of 101 mmHg. Computed tomography demonstrated extensive calcification of the ascending aorta. Coronary angiogram showed a 50% ostial left coronary artery stenosis. Under deep hypothermic circulatory arrest, the aorta was transected at the proximal arch and distal graft anastomosis was performed. This was followed by endarterectomy of the porcelain ascending aorta and the left coronary ostium. Aortic valve replacement, proximal aortic graft anastomosis, and a coronary artery bypass grafting (CABG) with the left internal thoracic artery (LITA) anastomosed to the left anterior descending artery (LAD) were then performed in a sequential manner.

Emergency operation for distal aortic arch aneurysm in Behcet's disease.

Arterial complications of Behcet's disease rarely affect the thoracic aorta, and the incidence of aortic arch aneurysm is especially low. We present a patient who developed a rapidly expanding aneurysm of the distal aortic arch after 20 years of treatment of Behcet's disease. Emergency total arch replacement was performed with a favorable outcome. Graft anastomosis to the normal aorta involving all three layers, wrapping of the anastomotic sites with wide felt strips, as well as strict management of systemic inflammation are essential for prevention of late complications associated with graft anastomosis sites.

Transoesophageal spinal cord stimulation for motor-evoked potentials monitoring: feasibility, safety and stability.

OBJECTIVES: Specificity of transcranial motor-evoked potentials (MEPs) is low because amplitude fluctuation is common, which seems due to several technical and fundamental reasons including difficulty in electrodes positioning and fixation for transcranial stimulation and susceptibility to anaesthesia. This study aimed to investigate the feasibility, safety and stability of our novel technique of transoesophageal spinal cord stimulation to improve the stability of MEPs. METHODS: Ten anaesthetized adult beagle dogs were used. Transoesophageal stimulation was performed between the oesophageal luminal surface electrode (cathode) and a subcutaneous needle electrode (anode) at the fourth to fifth thoracic vertebra level. Stimulation was achieved with a train of five pulses delivered at 2.0-ms intervals. Compound muscle action potentials were recorded from four limbs and external anal sphincter muscles. Stability to anaesthetic agents was tested at varying speeds of propofol and remifentanil, and effects of varying concentration of sevoflurane inhalation were also evaluated. RESULTS: Transoesophageal MEPs could be recorded without difficulty in all dogs. Fluoroscopic evaluation showed that electrodes misalignment up to 5 cm cranially or caudally could be tolerated. Stimulus intensity to achieve maximum amplitude of hindlimb muscle potentials on both sides was significantly lower by transoesophageal stimulation than by transcranial stimulation (383 ± 41 vs 533 ± 121 V, P = 0.02) and had less interindividual variability. Latency of transoesophageal MEPs was shorter than that of transcranial MEPs at every recording point. No arrhythmia was provoked during stimulation. Animals that were allowed to recover showed no neurological abnormality. In the two sacrificed animals, the explanted oesophagus showed no mucosal injury. Stability to varying dose of anaesthetic agents was similar between transoesophageal and transcranial stimulation, except for the potentials of forelimbs by transoesophageal stimulation that were resistant to anaesthetic depression. CONCLUSIONS: Transoesophageal stimulation for MEPs monitoring was feasible without difficulty and safe. Although its stability to anaesthetic agents was similar to that of transcranial stimulation, its technical ease and small interindividual variability warrants further studies on the response to spinal cord ischaemia.

Comparison of pH management during antegrade selective cerebral perfusion in canine models with old cerebral infarction.

OBJECTIVE: We sought to examine the influence on the brain, with or without old infarction, of pH management during antegrade selective cerebral perfusion in a canine model. METHODS: A cerebral infarct canine model was created by injecting a cylindrical silicone embolus. Dogs that had obvious neurologic deficits and had survived for 4 weeks or more were included in the model. Deep hypothermia with antegrade selective cerebral perfusion was performed in intact mongrel dogs (alpha-stat: group A, n = 6; pH-stat: group B, n = 6) and mongrel dogs with infarctions (alpha-stat: group C, n = 6; pH-stat: group D, n = 6). Maxillary vein saturation of oxygen, venous-arterial lactate difference, and serum concentrations of malondialdehyde and glutamate were measured and central conduction times and amplitude in somatosensory evoked potentials were assessed during the operation. RESULTS: During the experimental procedure, the maxillary vein saturation of oxygen was significantly less (P <.05), whereas the venous-arterial lactate difference was significantly greater (P <.05) in the cooling phase to 28 degrees C in group C than in the other groups. The pH-stat group showed significantly greater arterial Paco(2) and lower pH than the alpha-stat group during the period between the cooling to 28 degrees C and the rewarming to 28 degrees C (P <.05). Other intraoperative parameters did not show any difference among the groups. In group C the serum concentrations of malondialdehyde and glutamate significantly increased, as did the central conduction time, whereas in both groups C and D the amplitude ratio decreased significantly. CONCLUSIONS: This experiment suggests that pH-stat management during antegrade selective cerebral perfusion provides more effective protection for a brain with old infarction than alpha-stat management.