Remifentanil produces vasorelaxation in isolated rat thoracic aorta strips

BACKGROUND: Remifentanil can cause transient instability in hemodynamic variables. However this change may not be solely the result of autonomic or central nervous system inhibition or of centrally mediated vagal stimulation. In this study, the aim was to examine the direct effects of remifentanil on isolated thoracic aorta strips in vitro. METHODS: Forty-five Wistar rat thoracic aorta rings were isolated, and contraction-relaxation responses were recorded. RESULTS: In aortic rings precontracted with phenylephrine or potassium chloride, remifentanil produced concentration-dependent relaxation in both endothelium-intact and denuded rings (P<0.001). Remifentanil induced significantly greater relaxation in intact rings than in those denuded of endothelium, regardless of whether they were precontracted with phenylephrine hydrochloride or KCl (P<0.001). When the endothelium was present, remifentanil produced greater relaxation in KCl-contracted rings than in PE-contracted rings at lower concentrations (10-9 and 10-8), and similar relaxation at higher concentrations (10-7 and 10-6). However, when the endothelium was removed, relaxation was similar in both solutions, at all concentrations (10-9 to 10-6). In intact rings, pretreatment with L-NO-ARG or indomethacin reduced the degree of remifentanil-induced relaxation. In Ca+ +/- free media, calcium-dependent KCl contractions were inhibited in a dose-dependent manner by remifentanil (P<0.001). CONCLUSION: Remifentanil vasodilates by an endothelium-dependent mechanism, involving prostacyclin and nitric oxide released from the endothelium. Its endothelium-independent vasodilation probably occurs via the suppression of voltage-sensitive Ca++ channels.     

胸主动脉分支血管的CT研究

目的 利用CT血管造影测量胸主动脉分支血管,为胸主动脉腔内修复技术提供相关的血管解剖指导.方法 收集2008年1月-2012年2月在广州军区武汉总医院进行胸主动脉CT血管造影检查的739例患者资料,测量升主动脉、主动脉弓、弓上分支的直径和长度,并进行统计、分析.结果 主动脉弓分为标准型和变异型,其中标准型最常见,占总例数的91.1％,变异型占8.9％.主动脉弓标准型患者的冠状动脉开口处升主动脉直径为(35.7±4.3) mm,头臂干开口处升主动脉直径为(33.6±4.2) mm,头臂干与左颈总动脉之间的主动脉弓直径为(29.4±5.7) mm,左颈总动脉与左锁骨下动脉之间的主动脉弓直径为(27.6±4.2) mm,左锁骨下动脉开口处降主动脉直径为(25.4±4.5) mm,头臂干在主动脉弓分支处的直径为(12.9±0.9) mm,左颈总动脉在主动脉弓分支处的直径为(8.5±0.7)mm,左锁骨下动脉在主动脉弓分支处的直径为(10.4±1.1) mm,冠状动脉与头臂干之间的管壁长度为(53.3±12.5) mm,头臂干与左颈总动脉之间的管壁长度为(4.7±1.5) mm,左颈总动脉与左锁骨下动脉之间的管壁长度为(7.9±2.6)mm,头臂干起始处至右锁骨下动脉开口处长度为(41.1±8.2)mm,左锁骨下动脉起始处至椎动脉开口处管腔长度为(38.5±5.7) mm,头臂干与左颈总动脉间距的平面与矢状面之间的夹角为(71.2±7.2)°,左颈总动脉与左锁骨下动脉间距的平面与矢状面之间的夹角为(31.1±2.9)°.结论 CT测量所得的胸主动脉数据可以为血管支架的生产提供支持,还能为腔内修复术中支架的定位释放提供指导.     

Freezing the canine thoracic aorta in situ

The descending thoracic aorta was frozen in situ in 32 dogs with liquid nitrogen (?196°C). After thawing, the thoracic aorta continued to function as a blood conduit. Devitalization of the aorta was produced but no postoperative complications or serious late sequelae occurred. The reparative process was orderly and featured gradual resorption of necrotic tissue and replacement by new tissue that restored normal aortic wall structure. Late changes, 8 months after freezing, included progressive localized arteriosclerotic changes and calcification (cartilaginous and bony metaplasia). These results encourage the continued development of cryosurgical techniques for visceral tumors involving critical blood vessels.     

The wrapping method using biodegradable felt strips has a preventive effect on the thinning of the aortic wall: experimental study in the canine aorta

OBJECTIVES: Wrapping methods have been widely used to reinforce the anastomotic site in vascular surgery; however, postoperative changes in the aortic wall wrapped by nonbiodegradable felt have not been well characterized. The purposes of this investigation are to elucidate the sequelae of wrapping with nonbiodegradable felt on the aortic wall and to modify those changes by using biodegradable felt with or without basic fibroblast growth factor (bFGF). METHODS: The descending thoracic aortas of 15 beagles were wrapped with three different materials: nonbiodegradable polytetrafluoroethylene (PTFE) felt, biodegradable polyglycol acid (PGA) material, and PGA with 100 microg bFGF (n = 5 in each group). The descending thoracic aorta was resected after 3 months. The thickness of the aortic wall, vessel density in the media and the adventitia, and the wall strength were assessed. Untreated native aortic wall served as a normal control. RESULTS: The thickness of the media of the PTFE group was lower than that of the PGA + bFGF group (66% +/- 5% vs 85% +/- 6% of control, P < .05). The adventitia-media ratio in the PTFE group decreased compared with controls (59.1% of normal, P < 0.05), whereas those in the PGA and PGA + bFGF groups increased (172.1% and 189.6% of normal, respectively, P < .01). The collagen-smooth muscle ratio in the media was higher in the PTFE group than in the controls (0.14 +/- 0.02 vs 0.07 +/- 0.01, P < .01). The number of vessels in the adventitia was higher in the PGA + bFGF group than those in PTFE or PGA groups (29.6 +/- 2.5/mm2 vs 6.4 +/- 0.8/mm2, 19.0 +/- 1.1/mm2, P < .01). The PGA + bFGF group demonstrated larger failure force than the PTFE group (4.0 +/- 0.3 kgf vs 1.6 +/- 0.3 kgf, P < .01). The failure stress in the PGA and PGA + bFGF groups was larger than that in PTFE group (PTFE:PGA + bFGF = 5.3 +/- 0.9 x10(2) kPa:11.7 +/- 1.7 x 10(2) kPa, P < .01; PTFE:PGA = 5.3 +/- 0.9 x 10(2) kPa:11.2 +/- 1.2 x 10(2) kPa, P < .05). CONCLUSION: The aortic wall wrapped with nonbiodegradable PTFE felt showed a reduced thickness and diminished vessels in the adventitia. Biodegradable felt (PGA), with or without bFGF, modified these histologic changes. The vessel-rich thickened adventitia, after wrapping by PGA with bFGF, was associated with increased aortic wall strength. CLINICAL RELEVANCE: This investigation was conducted in an attempt to elucidate mechanisms underlying the occurrence of late postoperative false aneurysm after aortic surgery. We hypothesized that sustaining compression of the aorta by the felt strip may cause structural derangement and local ischemia on the aortic wall. We used a simple wrapping of the aorta with a felt strip rather than a felt strip at anastomotic sites to simplify the experimental model and to exclude confounding factors brought by technical inconsistency on the surgical anastomosis. We further attempted to find a clue for preventing adverse effects of wrapping with a conventional felt strip. Practically, we pursued a possible application of a biodegradable felt strip to aortic wrapping in our experimental model before we proceed in a clinical application of the new material.     

Propofol has both enhancing and suppressing effects on human platelet aggregation in vitro.

BACKGROUND: Volatile anesthetics are known to suppress platelet aggregation. In contrast, there is conflicting information regarding the effect of propofol on platelet function. The present study was designed to clarify the effects of propofol on platelet function and the mechanisms underlying these effects. METHODS: Propofol or an equivalent volume of 10% Intralipos (as a control) was added to test tubes 5 min before the induction of each reaction. Platelet aggregation induced by epinephrine, arachidonic acid (AA), prostaglandin G2 (PGG2), or STA2 (a thromboxane A2 [TXA2] analog) was measured using an eight-channel aggregometer. To determine type 1 cyclooxygenase activity, AA (0.5 mM) was added to an assay mixture containing type 1 cyclooxygenase, and the concentration of the final product, malonaldehyde, was measured by spectrophotometry. Epinephrine-, adenosine diphosphate-, AA-, and PGG2-induced TXA2 formation was measured using a commercially available radioimmunoassay kit. To estimate TXA2 receptor-binding affinity, 3H-S145, a specific TXA2 receptor antagonist, was added, and the radioactivity of receptor-bound 3H-S145 was determined using a liquid scintillation analyzer. Inositol 1,4,5-triphosphate formation was measured in STA2-stimulated platelets using a commercially available inositol 1,4,5-triphosphate assay kit. RESULTS: Propofol (40 microM) enhanced, whereas 100 microM suppressed, adenosine diphosphate- and epinephrine-induced secondary aggregation without affecting primary aggregation. Propofol (40 microM) also enhanced, but 100 microM suppressed, AA-induced aggregation. Propofol (100 microM) enhanced PGG2- and STA2-induced aggregation. Propofol (100 microM) suppressed AA-induced TXA2 formation but did not alter that induced by PGG2. Propofol (30-100 microM) suppressed AA-induced malonaldehyde formation, indicating inhibition of type 1 cyclooxygenase activity. Propofol did not alter TXA2 receptor-binding affinity. Propofol (30 and 100 microM) augmented inositol 1,4,5-triphosphate formation in STA2-stimulated platelets. CONCLUSIONS: The present findings clearly indicate that high concentrations of propofol suppress the activity of type 1 cyclooxygenase, the enzyme that converts AA to PGG2. Furthermore, propofol also enhanced STA2-induced inositol 1,4,5-triphosphate formation. These results may explain the inconsistent findings of previous investigators.     

Critical decisions in trauma of the thoracic aorta

Trauma to the thoracic aorta is a significant injury with a high mortality. This mortality is partly due to the delayed recognition of the condition. The increase of motor vehicle accidents and the use of firearms worldwide has resulted in an increase of the incidence of trauma to the thoracic aorta. Certain new developments in diagnosis and management have resulted in traditional methods being questioned. This review analyses current literature and data which we attempt to evaluate.     

Surgical treatment for primary infected aneurysm of the descending thoracic aorta,abdominal aorta,and iliac arteries

OBJECTIVE AND METHOD: In this retrospective review, we report the surgical results of infected aortic aneurysms treated at a single center over 5 years. RESULTS: From October 1996 to October 2001, 19 patients with infected aortic aneurysm were treated with surgery, nine with suprarenal infections (four proximal descending thoracic aortic aneurysms, two distal descending thoracic aortic aneurysms, and three suprarenal abdominal aortic aneurysms) and 10 with infrarenal infections (eight infrarenal abdominal aortic aneurysms and two iliac artery aneurysms). All had a positive blood or tissue culture; 89% were febrile, 89% had leukocytosis, and 32% were hemodynamically unstable. The most common responsible pathogens were Salmonella organisms (74%) followed by Streptococcus species (11%). Nine of 10 infrarenal infections were caused by Salmonella organisms. Both infrarenal and suprarenal infections were treated with wide débridement of infected aorta, in situ prosthetic graft or patch repair, and prolonged intravenous antibiotics. Hospital survival rate was 95%: 100% for infrarenal and 89% for suprarenal infections. There was no perioperative intestinal ischemia or perioperative limb loss. Acute renal failure occurred in two patients with suprarenal infection. Late deaths have occurred in three patients with one early graft infection (5%) resulting in the only one in-hospital death at 4 months. Sixteen patients remain alive at mean follow-up of 17.8 months (range, 4-47 months). There have been no late aortic or graft infections. During the same period, there were five unoperated patients, four of whom died of shock during hospitalization. CONCLUSIONS: Infected aortic aneurysm is common in Taiwan, and Salmonella species were the most common responsible microorganisms. With surgical intervention and prolonged intravenous antibiotics, in situ graft replacement provided a good outcome. The incidence of prosthetic graft infection was low, even in patients with infections due to Salmonella species and with in situ graft replacement.     

Single-stage transmediastinal replacement of the ascending, arch, and descending thoracic aorta

BACKGROUND: Aneurysms of the ascending, arch, and descending thoracic aorta are typically managed with two operations. The first stage involves replacement of the ascending and arch aorta leaving a segment of graft in the proximal descending aorta with a mortality and stroke risk of 8%. The second stage involves replacement of the descending aorta with a mortality of 5% and a paraplegia risk of 5% to 10%. Some patients refuse surgical completion and others are at increased risk to undergo the second stage thoracotomy, leaving them with untreated descending thoracic aortic aneurysms vulnerable to rupture. A single-stage transmediastinal operation used in 14 patients is described. METHODS: Under circulatory arrest, the descending thoracic aorta is opened. A wire is passed up to the arch and a graft is brought down and secured excluding the descending thoracic aneurysm. The arch vessels are attached as a single patch and the graft is brought forward, replacing the ascending aorta. RESULTS: Fourteen patients have undergone single-stage replacement of the ascending, arch, and descending aorta with a 14% mortality rate and 14% incidence of paraplegia. CONCLUSIONS: Patients with aneurysms of the ascending, arch, and descending thoracic aorta can be managed with a single operation with comparable mortality and morbidity of the two-stage approach.     

Lower limbs revascularization originated in the descending thoracic aorta

The revascularization of the lower limbs through a bypass graft from the descending thoracic aorta is one of the most uncommon surgical procedures within the scope of the so-called "extra-anatomic revascularization". It is an highly selective procedure in terms of indications and is regarded as an effective hemodynamic alternative, with acceptable long-lasting results. Two patients who underwent successfully the operation are reported, followed by a discussion on the technical aspects, indications, complications and early and late results of the procedure.     

Endovascular repair of the thoracic aorta in octogenarians.

Background: To evaluate the feasibility and safety of thoracic endografting in the octogenarian population. Methods: Between February 2000 and August 2005, 249 patients with a mean age of 69+/-12.3 years (range 23-91) underwent thoracic endografting. Forty-four patients (27 males and 17 females) were octogenarians with a mean age of 84+/-2.7 years. Indications for intervention included: atherosclerotic aneurysms (26/44, 59%), acute and chronic dissections (9/44, 20.5%), penetrating aortic ulcers (6/44, 14%) and contained rupture (3/44, 7%). Results: Endovascular repair was achieved in all octogenarian patients (44/44, 100%). Mean length of stay was 4.7+/-3.6 days. Two cardiac-related deaths and 1 retrograde dissection death occurred (3/44, 7%). Complications included hemiparesis (n=2) with full recovery at discharge, groin hematoma (n=1), pneumonia (n=2) and stroke (n=1) [6/44, 11%]. Endoleaks were diagnosed in 3 patients [3/44, 7%] (2 type I, 1 type II) at 30-day follow-up. Two patients developed an endoleak beyond 30 days [2/44, 5%] (1 type I, 1 type II). Two re-interventions were necessary at 30 days (1 type I, 1 type II). Mean follow-up was 22 months and there were no device migrations or aortic ruptures. No statistical differences in overall mortality were noted between octogenarians and non-octogenarians at 30 days (7% vs 6%, p=NS), 12 months (18% vs 13%, p=NS) and 24 months (27% vs 15%, p=NS). However, at 5 years post-procedure, octogenarians had a significantly higher overall mortality than non-octogenarians (32% vs 17%, p=0.038). Conclusions: Advanced age is not a contraindication to thoracic endografting with favorable short and mid-term outcomes compared to non-octogenarians.