Quantification of exhaled propofol is not feasible during single-lung ventilation using double-lumen tubes: A multicenter prospective observational trial

Background

Volatile propofol can be measured in exhaled air and correlates to plasma concentrations with a time delay. However, the effect of single-lung ventilation on exhaled propofol is unclear. Therefore, our goal was to evaluate exhaled propofol concentrations during single-lung compared to double-lung ventilation using double-lumen tubes.

Methods

In a first step, we quantified adhesion of volatile propofol to the inner surface of double-lumen tubes during double- and single-lumen ventilation in vitro. In a second step, we enrolled 30 patients scheduled for lung surgery in two study centers. Anesthesia was provided with propofol and remifentanil. We utilized left-sided double-lumen tubes to separately ventilate each lung. Exhaled propofol concentrations were measured at 1-min intervals and plasma for propofol analyses was sampled every 20 min. To eliminate the influence of dosing on volatile propofol concentration, exhalation rate was normalized to plasma concentration.

Results

In-vitro ventilation of double-lumen tubes resulted in increasing propofol concentrations at the distal end of the tube over time. In vitro clamping the bronchial lumen led to an even more pronounced increase (Δ AUC +62%) in propofol gas concentration over time. Normalized propofol exhalation during lung surgery was 31% higher during single-lung compared to double-lung ventilation.

Conclusion

During single-lung ventilation, propofol concentration in exhaled air, in contrast to our expectations, increased by approximately one third. However, this observation might not be affected by change in perfusion-ventilation during single-lung ventilation but rather arises from reduced propofol absorption on the inner surface area of the double-lumen tube. Thus, it is only possible to utilize exhaled propofol concentration to a limited extent during single-lung ventilation.

Registration of Clinical Trial

DRKS-ID DRKS00014788 ( www.drks.de ).     

肾周脂肪梅奥粘连概率评分系统在肾癌后腹腔镜肾部分切除术中的应用

目的探讨肾周脂肪梅奥粘连概率评分系统（MAP）在肾癌后腹腔镜肾部分切除术中的临床应用价值。 方法回顾性分析2015年1月至2020年6月徐州医科大学附属淮安医院泌尿外科收治的行后腹腔镜肾部分切除术的153例肾癌患者的临床病例资料。依据MAP评分系统将其分为低度复杂组、中度复杂组和高度复杂组三组。比较各组间的手术时间、术中出血量、术中及术后并发症、术中热缺血时间、术后住院时间及术后血肌酐变化情况。 结果在153例患者中，低度复杂组68例，中度复杂组58例和高度复杂组27例。三组患者在年龄、性别、术前血肌酐水平、肿瘤最大径、肿瘤位置、BMI、RENAL评分等方面差异无统计学意义（P>0.05）。随着复杂程度的提高，手术时间、术中出血量也在不断增加（P<0.05）；而术中热缺血时间、术后住院时间及术后血肌酐水平无明显变化（P>0.05）。在术中并发症方面，随着复杂程度的提高，术中并发症的发生率也在增加（P<0.05），且高度复杂组的术后并发症发生风险是低度复杂组的13.895倍（P=0.002)，MAP评分系统预测术中并发症发生的精度较高（AUC=0.757，P=0.002）。但是术后并发症各组比较差异无统计学意义（P>0.05）。 结论MAP评分系统在肾癌后腹腔镜肾部分切除术中，对预估手术难度及术中并发症发生风险有较好的临床应用价值。     

针灸联合西药对中重度间歇性过敏性鼻炎患者T淋巴细胞亚群、IL-4、IL-10、VACM-1水平的影响

目的观察针灸联合西药对中重度间歇性过敏性鼻炎患者血清T淋巴细胞亚群、炎性因子及血管细胞黏附分子-1(VACM-1)的影响。方法将120例中重度间歇性过敏性鼻炎患者随机分为对照组和治疗组,每组60例。对照组予丙酸氟替卡松鼻喷雾剂、盐酸氮卓斯汀片治疗,治疗组在对照组治疗措施的基础上加用针灸疗法。两组疗程均为28天,观察临床疗效,比较中医证候积分、血清T淋巴细胞亚群、炎性因子[白介素-4(IL-4)、白介素-10(IL-10)]及VACM-1水平的变化情况。结果①治疗组、对照组总有效率分别为95.0%、81.7%,治疗组临床疗效优于对照组(P0.05)。②治疗前与疗程结束后7天组内比较,两组中医证候(鼻塞不通、鼻痒难耐、鼻流清涕、喷嚏频作)较治疗前改善(P0.05);组间疗程结束后7天比较,治疗组中医证候改善情况优于对照组(P0.05)。③治疗前与疗程结束后7天组内比较,两组血清CD3~+、CD4~+水平和CD4~+/CD8~+较治疗前升高(P0.05),血清CD8~+、IL-4、IL-10、VCAM-1水平较治疗前降低(P0.05);组间疗程结束后7天比较,上述指标差异有统计学意义(P0.05)。结论针灸联合西医治疗中重度间歇性过敏性鼻炎疗效满意,可有效缓解患者的临床症状,改善机体免疫状态,减轻炎症反应。     

Avian mud nest architecture by self-secreted saliva

Mud nests built by swallows (Hirundinidae) and phoebes (Sayornis) are stable granular piles attached to cliffs, walls, or ceilings. Although these birds have been observed to mix saliva with incohesive mud granules, how such biopolymer solutions provide the nest with sufficient strength to support the weight of the residents as well as its own remains elusive. Here, we elucidate the mechanism of strong granular cohesion by the viscoelastic paste of bird saliva through a combination of theoretical analysis and experimental measurements in both natural and artificial nests. Our mathematical model considering the mechanics of mud nest construction allows us to explain the biological observation that all mud-nesting bird species should be lightweight.

Bird nests come in a variety of forms made from diverse building materials (1, 2). Each type of bird nest is subjected to mechanical constraints imposed by material characteristics. To overcome these constraints, birds have devised brilliant architectural technologies, which provide inspiration for a novel materials processing scheme and help us to better understand animal behavior.For instance, some birds including storks (Cicioniidae) and eagles (Accipitidae) build nests by piling up hard filamentary materials such as twigs, harnessing their friction as the cohesion mechanism (3). Weaverbirds (Ploceidae) weave soft filamentary materials such as grass and fine leaves into a woven nest tied to a tree branch. Some bird species use their own saliva in nest building, which Darwin considered an example of natural selection (4). An extreme case is the Edible-nest Swiftlets, which build their nest purely of self-secreted saliva so that it can be attached to cliff walls and cave ceilings where the above twig piles and tied leaves are not allowed (5).Swallows (Hirundinidae), phoebes (Sayornis), and other mud nesters have developed a unique building material, a mixture of mud and their own saliva, in contrast to those made of purely collected or self-secreted materials (6) (Fig. 1). During construction, mud nesters repeatedly pile a beakful of wet mud on the nest, and liquid bridges are formed in the nest due to evaporation. While building a nest usually takes several weeks, a transition from wet to dry structures can occur within a few hours. Hence, the capillary forces of liquid bridges temporarily provide cohesion such as those in sandcastles. However, unlike sandcastles, dehydrated saliva comes into play for permanent cohesion after complete evaporation (SI Appendix, Supplementary Note 1).Open in a separate windowFig. 1.A nest of the barn swallow (H. rustica). (A) Photograph of a barn swallow nest, taken from under the ceiling of a house in Suwon-si, Gyunggi-do, South Korea (37°16′13.5″N 126°59′01.0″E). (B) SEM image of the nest surface. (C) Chemical composition analysis of the surface shown in B by EDS. The red area indicates a region containing mostly carbon atoms, which may originate from bird saliva. The green area indicates a region containing mostly the silicon atoms of clay particles.Mud itself cannot confer sufficient cohesion and adhesion in mud nests. The ability of mud nests to bear tensile loads originates from the gluing agent in the bird''s saliva, which permeates into granules as a liquid and binds them as a solid after solvent evaporation (6–8) (SI Appendix, Supplementary Note 2). The gluing agent is called mucin, a family of large glycoproteins that are ubiquitous in animal organs and form a mucus gel with versatile functionality (9). Fig. 1B shows the scanning electron microscopy (SEM) image of a barn swallow’s mud nest consisting of platelet clay particles and larger grains. Energy-dispersive spectroscopy (EDS) mapping image of Fig. 1C clearly shows regions corresponding to organic material which is presumed to be from bird’s saliva.Of particular interest and worth biophysical investigation are the tensile strength of the mud nest with hardened saliva, design principles associated with the saliva-originated strength, and the resulting effects on the evolution of these mud-nesting birds. Principles behind cohesion in granular materials, such as wet sands (10), cemented powder aggregates (11), construction materials (12), and pharmaceutical tablets (13), have been studied to date, exploring the stress transmission, elasticity, and failure (14–18), and the formation of solidified bridges (19–21). However, little attention has been paid to the cohesion effects of self-secreted polymer materials upon evaporation and the biologically constructed granular architecture like birds’ mud nests. Here we devised experimental techniques to measure the strength of the relatively small and fragile nest specimens in order to mechanically characterize birds’ mud nests. We elucidate how solutes from bird saliva generate solid bridges that give rise to macroscopic tensile strength, which has long awaited physicochemical explanation since its first observation (4). To characterize the design principle of bird''s mud nests, we investigated natural and three-dimensional (3D)-printed artificial nests with various tools for visualization and mechanical testing. Along with the experimental studies, we theoretically investigated the effects of biopolymer concentration on nest strength. This combination of theory and experiment suggests that there is a size limit for mud-nesting birds, which is supported by biological data.     

How does measurement of platelet P-selectin compare with other methods of measuring platelet function as a means of determining the effectiveness of antiplatelet therapy?

Measurement of P-selectin on activated platelets as a means of measuring platelet function utilizing the technology described here has the advantage of not requiring immediate access to specialist equipment and expertise. Blood samples are activated, fixed, stored, and transported to a central laboratory for flow cytometric analysis. Here we have compared P-selectin with other more traditional approaches to measuring platelet function in blood and/or platelet-rich plasma (PRP) from patients with acute coronary syndromes on treatment for at least 1 month with either aspirin and clopidogrel or aspirin with prasugrel. The comparators were light transmission aggregometry (LTA), VerifyNow and Multiplate aggregometry (for determining the effects of aspirin) and LTA, VerifyNow and Multiplate together with the BioCytex VASP phosphorylation assay (for the P2Y₁₂ antagonists). The P-selectin Aspirin Test revealed substantial inhibition of platelet function in all but three of 96 patients receiving aspirin with clopidogrel and in none of 51 patients receiving aspirin and prasugrel. The results were very similar to those obtained using LTA. There was only one patient with high residual platelet aggregation and low P-selectin expression. The same patients identified as “non-responders” to aspirin also presented with the highest residual platelet activity as measured using the VerifyNow system, although not quite as well separated from the other values. With the Multiplate test only one of these patients clearly stood out from the others. The results obtained using the P-selectin P2Y₁₂ Test in 102 patients taking aspirin and clopidogrel were similar to the more traditional approaches in that a wide scatter of results was obtained. Generally, high values seen with the P-selectin P2Y₁₂ Test were also high with the LTA, VerifyNow, Multiplate, and BioCytex VASP P2Y₁₂ Tests. Similarly, low residual platelet function using the P2Y₁₂ test was seen irrespective of the testing procedure used. However, there were differences in some patients. Prasugrel was always more effective than clopidogrel in inhibiting platelet function with none of 56 patients (P-selectin and VerifyNow), only 2 of 56 patients (Multiplate) and only 3 of 56 patients (Biocytex VASP) demonstrating high on-treatment residual platelet reactivity (HRPR) defined using previously published cut-off values. The exception was LTA where there were 11 of 56 patients with HRPR. It remains to be seen which experimental approach provides the most useful information regarding outcomes after adjusting therapies in treated patients.     

儿童免疫性血小板减少症发病机制研究进展

免疫性血小板减少症(immune thrombocytopenia,ITP)是一种由自身免疫介导的出血性疾病,其特点为血小板破坏增多和生成不足。ITP发病机制复杂多样,具有异质性,至今尚未完全明确,在儿童中尤其突出。现有研究表明,免疫失耐受引起各种免疫细胞或分子异常,进而导致血小板破坏增多或生成不足,是ITP的核心发病机制。随着研究的不断深入,越来越多的机制被报道。该文就儿童ITP的发病机制及其研究进展进行介绍。     

子宫腔整复手术后再粘连的防治

宫腔粘连是子宫内膜基底层损伤所引起的疾病，严重影响女性生理健康和生育功能。宫腔镜下宫腔粘连分离术作为子宫腔整复手术的首选治疗方法，以恢复子宫正常解剖结构及功能为目的，但术后复发仍是妇科医生面临的巨大挑战。目前防治术后再粘连的方法主要有屏障治疗、激素治疗和羊膜疗法等，其他的治疗选择，如干细胞疗法、阿司匹林、富血小板血浆、西地那非等治疗尚处于研究当中。目前尚无防治术后再粘连的最佳治疗方案，如何达到最佳治疗效果仍需进一步研究。