选择性肋间动脉灌注在主动脉手术中的脊髓保护作用

目的: 观察选择性肋间动脉灌注在降主动脉手术中对脊髓的保护作用。方法: 2004年8月~2007年7月,10例患者（非灌注组）因降主动脉夹层（4例）或降主动脉瘤（6例）行降主动脉置换术,术中切断置换降主动脉的肋间动脉。2007年8月~2008年6月,6例患者（选择性灌注组）因降主动脉夹层（4例）或降主动脉瘤（2例）行降主动脉置换术。术中保留置换降主动脉的所有肋间动脉,进行选择性肋间动脉灌注,减少脊髓缺血时间及程度以达到脊髓保护的目的。术后早期观察和中期随访是否有截瘫发生。结果: 非灌注组术中脊髓缺血时间(28.9±3.6)min,选择性灌注组术中脊髓缺血时间(25.0±1.7)min,非灌注组患者的脊髓缺血时间显著长于选择性灌注组。非灌注组10例患者中1例患者术后出现截瘫,选择性灌注组6例患者术后均无截瘫发生,痊愈出院,选择性灌注组随访4～14个月,患者无远期截瘫发生,生活质量良好。结论: 选择性肋间动脉灌注可缩短脊髓缺血时间和程度,脊髓保护效果良好,并可大大降低手术操作难度。     

Computational fluid dynamics within bifurcated abdominal aortic stent-grafts.

PURPOSE: To assess the hemodynamic forces on a bifurcated abdominal aortic stent-graft under realistic conditions of flow, blood pressure, and sac pressure. METHODS: Computational fluid dynamics was used to study the temporal and spatial variations in surface pressure and shear through the cardiac cycle on models of bifurcated stent-grafts derived from computed tomography in 4 patients who had previously undergone endovascular repair of abdominal aortic aneurysm (AAA). The trunk, bifurcation, and limbs of the graft were analyzed separately and as parts of a unified whole. Analyses were repeated under varying conditions of sac pressure, reflecting different conditions of perigraft flow and sac diameter change. RESULTS: Pressure-related forces were far larger than flow-related forces in all 3 segments of all 4 cases. The largest forces acted at the bifurcation of the stent-graft. High sac pressures, seen in patients with endoleak or aneurysm dilatation, were associated with reduced transmural pressure and low-pressure-derived forces. CONCLUSION: Several parameters of stent-graft design affect the magnitude and distribution of forces on a bifurcated stent-graft. The forces on a stent-graft are also affected by the pressure within the aneurysm sac, which depends on stent-graft performance.     

Spinal cord protection for thoracic aortic surgery

Spinal cord protection is critical for successful outcomes after descending thoracic and thoracoabdominal aortic aneurysm repair. For descending thoracic aneurysms which end above T9, optimum protection is maintained by distal aortic perfusion via a left atrial to distal arterial bypass circuit with a centrifugal pump. In repairs of extensive thoracoabdominal aneurysms, additional measures are required of extensive thoracoabdominaal aneurysms, additional measures are required including hypothermia, intercostal artery implantation into the graft, and spinal fluid drainage.     

胸腹主动脉瘤手术患者血脑屏障损伤生化标志物的监测与评估

目的:探讨胸腹主动脉瘤手术患者的血脑屏障损伤,评价血清和脑脊液S100B蛋白、神经元特异性烯醇化酶(NSE)和胶质原纤维酸性蛋白(GFAP)诊断血脑屏障损伤的价值。方法:检测和分析15例胸腹主动脉置换患者,男性11例,女性4例,平均年龄46岁。围手术期各时间点白蛋白商值和脑脊液-IgG指数,并以其为标准评估血脑屏障损伤、以及其与血清和脑脊液的S100B、GFAP和NSE蛋白的相关性。结果:12例在主动脉重新开放后2 h至12 h时间内,白蛋白商值升高至9～28,而脑脊液-IgG指数升高至0.8～2,有3例患者血脑屏障损伤重:2例白蛋白分别升高至38.6和41.8,1例脑脊液-IgG指数升高至3.06。结论:胸腹主动脉手术中白蛋白商值和脑脊液-IgG指数会出现一过性轻到中度升高,提示血脑屏障一过性轻中度损害可能,未发现白蛋白商值和脑脊液-IgG指数与S100B、GFAP及NSE具有相关性。     

Efficacy and frequency of cerebrospinal fluid drainage in operative management of thoracoabdominal aortic aneurysms

BACKGROUND: Paraplegia remains the most dreaded complication following thoracoabdominal aortic repair. We investigated the efficacy of cerebrospinal fluid drainage as a spinal cord-protecting modality. We also evaluated the correlation between the frequency of cerebrospinal fluid drainage and the Crawford classification. METHODS: Spinal cord function was monitored during 20 open surgical procedures (group I) and 27 stent-graft implantations (group II). Evoked potentials and intracranial pressure were monitored in each operation. If intracranial pressure exceeded 15 mmHg, cerebrospinal fluid was drained. RESULTS: Cerebrospinal fluid drainage was necessary in 75 % of patients in group I (Crawford type I: 33 %, type II: 40 %, type III: 20 %, type IV: 7 %) and in 22 % of patients in group II (Crawford type I: 33 %, type II: 66 %). Evoked potential alterations correlated with an increase in intracranial pressure. Timely cerebrospinal fluid drainage reversed these changes in 72 %. Three patients remained paraplegic. CONCLUSION: Cerebrospinal fluid drainage is a valuable neuroprotective interventional tool to lower the risk of spinal cord ischemia. The combination of neurophysiological monitoring and cerebrospinal fluid drainage optimizes the prevention of paraplegia during aortic repair.     

胸腹主动脉瘤手术中重建肋间动脉的简易方法

目的:脊髓缺血性损伤是胸腹主动脉瘤手术后一种严重并发症,改进重建肋间动脉的外科技巧可减少这一风险的发生。方法:自2003年8月至2005年1月,行全胸腹主动脉替换术41例(男性30例,女性11例),年龄22～58岁,平均(40.3±9.1)岁。Crawford Ⅱ型38例,Crawford Ⅲ型3例,其中马方综合征合并胸腹主动脉瘤19例。采用深低温、分段停循环技术应用四分叉人工血管行全胸腹主动脉替换,其中自T6-L2肋间和腰动脉开口动脉壁修剪重建成新肋间血管管道,再与四分叉血管之8mm分支吻合,恢复脊髓血供。结果:术后早期死亡3例(病死率7.3%),脑部系统并发症3例(7.9%),脊髓损伤并发症2例(5.3%),均经脱水及神经营养治疗后痊愈。随访除3例死亡(病死率7.9%)外均生存良好,CT检查显示"新肋间动脉"血流通畅。结论:在胸腹主动脉瘤四分叉人工血管置换术中,采用修剪重建新肋间血管管道的方法,能简化手术方式,明显缩短脊髓和重要腹腔脏器的缺血时间,减少脊髓并发症发生,效果良好。     

Nasal-continuous positive airway pressure reduces pulmonary morbidity and length of hospital stay following thoracoabdominal aortic surgery

STUDY OBJECTIVES: Patients who undergo surgical repair of thoracoabdominal aortic aneurysms have a high risk for the development of respiratory complications, which cause significant postoperative morbidity and prolong hospitalization, compared to patients who undergo other types of surgery. We studied whether prophylactic noninvasive application of nasal continuous positive airway pressure (nCPAP) administered via a facemask immediately after extubation may reduce pulmonary morbidity and shorten the length of hospitalization. DESIGN: Prospective randomized clinical trial. SETTING: Surgical ICU of a university hospital. PATIENTS: Fifty-six patients following elective prosthetic replacement of the thoracoabdominal aorta, of whom 6 patients were excluded because they had received prolonged mechanical ventilation. INTERVENTIONS: Following extubation in the ICU, nCPAP was applied for 12 to 24 h at an airway pressure of 10 cm H2O to patients in the study group (n = 25). Subjects in the control group (n = 25) received standard treatment including intermittent nCPAP (10 cm H2O for 10 min) every 4 h. MEASUREMENTS AND RESULTS: In the study group, nCPAP was applied for a mean (+/- SD) duration of 23 +/- 3 h at an airway pressure of 10 +/- 1 cm H2O, which improved pulmonary oxygen transfer without altering hemodynamics (ie, heart rate, mean arterial BP, and central venous pressure). The application of nCPAP was associated with fewer pulmonary complications (Pa(O2)/fraction of inspired oxygen [F(IO2)] <100, atelectasis, pneumonia, reintubation rate) compared to the control group (7 of 25 patients vs 24 of 25 subjects, respectively; p = 0.019). The mean duration of intensive care treatment tended to be shorter in the study group compared to the control group (8 +/- 1 vs 12 +/- 2 days, respectively; difference not significant), while the mean length of hospital stay was shorter with nCPAP therapy (22 +/- 2 vs 34 +/- 5 days, respectively; p = 0.048). CONCLUSIONS: The prophylactic application of nCPAP at airway pressures of 10 cm H2O significantly reduced pulmonary morbidity and length of hospital stay following the surgical repair of thoracoabdominal aortic aneurysms. Thus, it can be recommended as a standard treatment procedure for this patient group.     

Spinal arterial anatomy and risk factors for lower extremity weakness following endovascular thoracoabdominal aortic aneurysm repair with branched stent-grafts

PURPOSE: To evaluate spinal arterial anatomy and identify risk factors for lower extremity weakness (LEW) following endovascular thoracoabdominal aortic aneurysm (TAAA) repair. METHODS: A retrospective review was conducted of 37 patients (27 men; mean age 74.8+/-7.1 years, range 58-86) undergoing endovascular TAAA repair with branched stent-grafts at a single academic institution from July 2005 to December 2007. Data were collected on preoperative comorbidities, duration of operation, blood loss, type of anesthesia, extent of aortic coverage, blood pressure, cerebrospinal fluid (CSF) pressure and drainage, and postoperative development of LEW. Pre- and postoperative contrast-enhanced computed tomographic angiograms (CTA) in a 26-patient subset were analyzed to evaluate the number of patent intercostal and lumbar arteries before and after repair. RESULTS: All patients were neurologically intact at the end of the operation. Seven (19%) patients developed LEW postoperatively: 6 perioperatively and 1 after discharge. LEW was associated with postoperative hypotension, internal iliac artery (IIA) occlusion, and fewer patent segmental arteries on preoperative CTA. Lowest mean systolic blood pressure was <90 mmHg in all 6 (100%) patients who developed LEW in hospital compared to 12 (44%) of the 27 patients who did not develop LEW (p = 0.02). Complete resolution of LEW (n = 4) followed prompt measures to raise blood pressure and lower CSF pressure. Persistent LEW (n = 3) was associated with sustained hypotension from sepsis, postoperative bleeding, and hemodialysis, respectively. Two (29%) of 7 patients with LEW either lost prograde flow to an IIA during repair or had bilaterally occluded IIAs preoperatively compared to 2 (7%) of 30 patients without LEW (p = 0.16). Comparison of pre- and postoperative CTAs showed no reduction in the mean number of patent segmental arteries in patients with or without LEW. CONCLUSION: Endovascular TAAA repair inevitably occludes direct inflow to lumbar and intercostal arteries. The distal segments of these arteries to the spine, however, are seen to remain patent through collaterals. Measures to preserve collateral pathways and increase perfusion pressure may help prevent or treat LEW.     

Two-stage combined endovascular and surgical approach for recurrent thoracoabdominal aortic aneurysm.

PURPOSE: To present a 2-stage combined endovascular and surgical approach for recurrent thoracoabdominal aortic aneurysm (TAAA). CASE REPORT: A 78-year-old man with previous surgical repairs of infrarenal abdominal and descending thoracic aortic aneurysms was referred for dysphagia due to an enlarging 9-cm aneurysm extending from the mid thoracic to the suprarenal aorta. Because no suitable endograft was available, an open repair was attempted, but the presence of a "frozen" chest made the redo procedure extremely difficult. A 2-stage treatment was thus decided upon. First, a retrograde bifurcated bypass graft was implanted from the abdominal aortic graft to the superior mesenteric and celiac arteries. Twenty days later, the TAAA was successfully excluded with a stent-graft, during which spinal fluid drainage was performed to prevent paraplegia. At 6 months, computed tomography showed patency of the endoprosthesis and visceral grafts. At 1 year, the patient remains asymptomatic. CONCLUSIONS: This case illustrates that a 2-stage combined endovascular and surgical approach may be a safe and effective alternative to reoperation for recurrent TAAA.     

Coincidence of spinal canal stenosis and thoracoabdominal aortic aneurysm

We report a case in which a thoracoabdominal aneurysm was present in association with previously unknown critical spinal canal stenosis. In spite of using left heart bypass, systemic hypothermia, and controlled cerebrospinal fluid drainage for spinal cord protection, the patient developed paraplegia following aortic aneurysm repair. Computed tomography scan revealed critical stenosis of the spinal canal that was thought to be sufficient to produce spinal cord compression syndromes including paraplegia.     

Brain and spinal cord protection during aortic surgery

In our experience, single-stage open repair of descending thoracic or thoracoabdominal aortic aneurysms with concurrent aortic arch disease is technically feasible via a high left thoracotomy or a thoracolaparotomy. Distal aortic and antegrade brain perfusion, in combination with brain and spinal cord protection, seems to contribute to adequate surgical and neurological outcome.     

Failure of selective shunting to intercostal arteries to prevent spinal cord ischemia during experimental thoracoabdominal aortic occlusion.

Paraplegia from spinal cord ischemia during thoracoabdominal aneurysm repair remains an unpredictable and unpreventable complication. In an effort to prevent spinal cord ischemia during aortic cross-clamping, preoperative angiographic localization of the blood supply to the spinal cord was performed in dogs. Sixteen animals underwent 60 minutes of thoracoabdominal aortic cross-clamping either without (control, n = 8) or with (shunted, n = 8) a selective shunt. Shunting was performed from the aortic arch to that isolated aortic segment angiographically shown to supply the thoracolumbar anterior spinal artery. Spinal cord blood flow was measured with microspheres just prior to cross-clamping, at 5 and 60 minutes after cross-clamping and at 5 minutes after restoration of aortic blood flow. Functional neurologic outcome was evaluated in animals at 24 hours postoperatively. Shunting did not decrease spinal cord injury. Seven of the 8 animals in the control group and 7 of the 8 in the shunted group developed paraplegia or paraparesis. Thoracic, but not lumbar spinal cord blood flow, was significantly increased in shunted animals. Spinal cord blood supply in dogs may be more segmental than previously believed. Technical problems in angiographic localization, spinal artery spasm, loss of spinal cord autoregulation or poor collateral circulation from the distal thoracic to the lumbar cord may also account for these results. Although shunting to aortic segments supplying the anterior spinal artery during thoracoabdominal aortic clamping may be attractive in humans, no benefit could be shown in this experimental model.     

应用腔内隔绝术治疗胸腹主动脉夹层及随访

目的:总结应用腔内隔绝术治疗Stanford B型主动脉夹层经验并报道中期随访结果。方法:22例急性和2例慢性Stanford B型主动脉夹层患者接受腔内隔绝术治疗,术后1、6、12个月,以后每年随访胸部X线平片与螺旋CT检查。结果:24例患者中23例技术成功,1例因支架故障技术失败,技术成功率95·8%。临床随访:23例技术成功患者中22例假腔内完全血栓形成,1例患者部分血栓形成,1例术后1周死于脑栓塞,1例术后3个月囊性动脉瘤形成需行外科血管置换术。临床成功率87·5%。结论:腔内隔绝术治疗急慢性胸腹主动脉夹层技术可行,中期疗效满意,远期疗效需要进一步随访观察。     

Treatment of thoracoabdominal aortic aneurysms with a combined endovascular and surgical approach.

AIM: The conventional approach for the repair of thoracoabdominal aneurysms remains complex and demanding and is associated with substantial morbidity and mortality. Moreover, in cases of reoperation the impact can be dramatic either in survival or in quality of life of the patients, albeit the use of adjuncts. A combined endovascular and surgical approach with retrograde perfusion of visceral and renal vessels has been realized in order to minimize intraoperative and postoperative complications. METHODS: Within an experience of 231 aortic stent-grafts between 1995-2000, 4 of the patients with thoracoabdominal aneurysms were treated with a combined endovascular and surgical approach. Three procedures were electively conducted and 1 on emergency basis. Two women, 59 and 68 years old, and 2 men, 68 and 73 years old (maximum aneurysm's diameter was 10, 6, 8 and 9 cm, respectively) were operated with the combined method (the first 2 patients had a previous open repair of a thoracoabdominal aneurysm). The surgical approach was executed in all patients without thoracotomy or re-do retroperitoneal exposure. Revascularization of renal, superior mesenteric (and celiac in 2 cases) arteries was accomplished via transperitoneal bypass grafting. Aneurysmal exclusion was performed by stent-graft deployment. RESULTS: The entire procedure was technically successful in all patients. The 1(st) patient was discharged 6 weeks after the operation, while the postoperative studies revealed the patency of the vessels and no evidence of leak or secondary rupture of the aneurysm; the patient died 3 months after the repair, due to rupture of an aneurysm of the ascending aorta. In the 2(nd) patient, 30 months after the operation, spiral-CT scanning revealed distinct shrinkage of the aneurysm, no graft migration or endoleak and patency of all revascularized vessels. The 3(rd) patient died on the 6th postoperative day due to multiorgan failure after having developed ischemic-related pancreatitis, albeit the successful combined repair. The 4(th) patient followed an uneventful course. No patient experienced any temporary or permanent neurological deficit. CONCLUSION: The combined endovascular and surgical approach is feasible, without cross-clamping of the aorta and with minimized ischemia time for renal and visceral arteries, and seems the appropriate strategy for high risk and previously operated, with a thoracoabdominal trans-diaphragmatic approach, patients.     

Interstitial fluid glucose dynamics during insulin-induced hypoglycaemia

Aims/hypothesis Glucose sensors often measure s.c. interstitial fluid (ISF) glucose rather than blood or plasma glucose. Putative differences between plasma and ISF glucose include a protracted delay during the recovery from hypoglycaemia and an increased gradient during hyperinsulinaemia. These have often been investigated using sensor systems that have delays due to signal smoothing, or require long equilibration times. The aim of the present study was to define these relationships during hypoglycaemia in a well-equilibrated system with no smoothing.Methods Hypoglycaemia was induced by i.v. insulin infusion (360 pmol·m^–2·min^–1) in ten non-diabetic subjects. Glucose was sequentially clamped at 5, 4.2 and 3.1 mmol/l and allowed to return to normoglycaemia. Subjects wore two s.c. glucose sensors (Medtronic MiniMed, Northridge, CA, USA) that had been inserted for more than 12 h. A two-compartment model was used to quantify the delay and gradient.Results The delay during the fall in plasma glucose was not different from the delay during recovery (8.3±0.67 vs 6.3±1.1 min; p=0.27) and no differences were observed in the ratio of sensor current to plasma glucose at basal insulin (2.7±0.25 nA·mmol^–1·l) compared with any of the hyperinsulinaemic clamp phases (2.8±0.18, 2.7±0.021, 2.9±0.21; p=NS). The ratio was significantly elevated following recovery to normoglycaemia (3.1±0.2 nA·mmol^–1·l; p<0.001).Conclusions/interpretation The elevated ratio suggests that the plasma to ISF glucose gradient was decreased following hypoglycaemia, possibly due to increased skin blood flow. Recovery from hypoglycaemia is not accompanied by a protracted delay and insulin does not increase the plasma to s.c. ISF glucose gradient.     

Proximal subcutaneous interstitial fluid pressure during cross-clamping of the descending thoracic aorta: A study of patients operated on for thoracic-or thoracoabdominal aortic aneurysms

Seven patients were operated on for thoracic (n=2) or thoracoabdominal (n=5) aortic aneurysms during cross-clamping of the aorta. Interstitial tissue fluid pressure was measured at the neck during cross-clamping of the descending thoracic aorta by the wick-in-needle technique, whereas control measurements were obtained prior to cross-clamping. The subcutaneous interstitial fluid pressure was significantly higher on the neck during cross-clamping of the thoracic aorta compared with control measurements (median 3.7 mmHg vs –0.6 mmHg, p<0.05). Increased subcutaneous interstitial tissue pressure of the upper part of the body is probably caused by increased capillary filtration rate induced by inhibited autoregulatory functions during aortic cross-clamping. The pressure measurements objectively confirm the problem of edema formation of the head and neck during these operations. The edema may occasionally affect the upper airways and represent a problem for intubation of the patient in the postoperative phase.     

Repair of asymptomatic aortic valve disease during other cardiac surgery.

Repair of asymptomatic aortic valve disease was performed in 12 patients (9 female, 3 male, mean age 57.5 years) undergoing other cardiac surgery. Stenosis was the predominant aortic valve lesion in 7 (group A) with a mean gradient of 33.4 mmHg and regurgitation of mean grade 1.4 was predominant in 5 (group B). Cusp debridement +/- commissurotomy was performed in 9; commissural resuspension in 6 and repair of cusp perforation in 2. Perioperative transoesophageal echocardiography was used to assess the adequacy of repair in 4 patients. Prospective precordial echocardiographic follow-up is complete (mean 4.3 months). In group A there has been a significant reduction is peak aortic pressure gradient (33.4 vs 22.1 mmHg, p less than 0.05) and in cusp thickness (2.25 to 1.64 mm, p less than 0.05). In group B the degree of incompetence has improved in 3 of the 5 patients. Three patients have worsened valve disease following repair; in all these there was mixed valve disease of rheumatic origin. Aortic valve repair of asymptomatic disease during other cardiac surgery is a feasible technique which does not accelerate the disease process in the short term. Long-term follow-up is in progress to assess the prognosis of this preventive intervention.