Effects of carbon dioxide absorbent cooling and temperature gradient reduction on water condensation in the anaesthesia circuit

BACKGROUND: Large quantities of water condensation occur in the anaesthesia circuit during low-flow anaesthesia. We hypothesized that cooling of the CO2 absorbent would prevent water condensation. METHODS: To cool CO2 absorbent efficiently, we constructed a novel temperature gradient reduction (TGR) canister, which was cooled by a blower. Experiments were divided into three groups: the conventional canister group (control group, n=6), the TGR canister without cooling group (TGR group, n=6), and the TGR canister with cooling group (TGR cooling group, n=6). One kilogramme of CO2 absorbent was placed into the canister. The anaesthetic ventilator was connected to a 3 litre bag and 300 ml min(-1) of CO2 was introduced. About 500 ml min(-1) of oxygen was used as fresh gas. The anaesthetic ventilator was set at a ventilatory frequency of 12 bpm, and tidal volume was adjusted to 700 ml. RESULTS: The longevity of the CO2 absorbent was 437 (sd 7.8) min in the control group, 564 (13.8) min in the TGR group (P<0.001 vs control), and 501 (5.8) min in the TGR cooling group (P<0.001 vs control, TGR). Total water condensation in the anaesthesia circuit was 215 (9.4) mg min(-1) in the control group, 223 (9.7) mg min(-1) in the TGR group, and 47.7 (5.7) mg min(-1) in the TGR cooling group (P<0.001 vs control, TGR). CONCLUSIONS: TGR of CO2 absorbent with cooling is a useful and simple method to reduce water condensation in the anaesthesia circuit in low-flow anaesthesia, with a little increase in the longevity of the CO2 absorbent.     

Studies on the oxygenation of human blood by photocatalytic action

Abstract:  The present article gave the proof of concept for oxygenating human blood using the established principles of photocatalytic action of anatase TiO₂ thin films in generating oxygen from water. The photocatalytic action involves the absorption of the UV optical energy (365 nm) to split water available in the blood into oxygen and hydrogen, and the generated oxygen is attached to the hemoglobin. In the present study, an enhanced catalytic action was achieved by preparing the nanosized anatase TiO₂ thin films on tin-doped indium oxide (ITO) thin films, forming TiO₂/ITO semiconducting junction. These TiO₂ and ITO thin films and the semiconducting junctions were grown by the reactive DC Magnetron sputtering technique (using pure metallic targets) at room temperature (300 K) and subsequently annealed at 870 K for 60 min. The annealing process (i) influenced the formation of the anatase phase of TiO₂; and (ii) diffused indium from ITO into TiO₂, forming InTi₂O₅. The work functions of ITO and InTi₂O₅ were measured to be 4.72 and 4.76 eV, respectively. The higher efficacy of the photocatalytic action was attributed to the lower work function of ITO. The results clearly show that the photocatalytic action increases the oxygen content in the blood significantly.     

Laparoscopic parenchymal division of the liver in a porcine model: comparison of the efficacy and safety of three different techniques

Background Bleeding is a known and CO₂ embolization a suggested risk factor for increased morbidity after laparoscopic liver resection. Devices for laparoscopic liver parenchymal transection must be evaluated for safety in this context. Method Twelve piglets underwent laparoscopic surgery during CO₂ pneumoperitoneum, each animal receiving three 6 cm long transections into the liver parenchyma made with ultrasonic dissector, ultrasonic shears and vessel sealing system, respectively. Endpoints were bleeding, operation time and gas embolization. The transections and embolization events, evaluated with transesophageal echocardiography, were video recorded. Bleeding and embolization were also assessed on video tapes and operating time measured. Arterial blood gases were recorded on line. Results The ultrasonic dissector was least advantageous in terms of bleeding and operation time. Gas embolization was more frequent with the vessel sealing system than with the ultrasonic dissector and ultrasonic shears. During two episodes of gas embolization, pCO₂ increased and pO₂ and pH decreased. Conclusions Use of all three devices is feasible. Bleeding and operation time are greatest with the ultrasonic dissector. Gas embolization occurs during transection, though in most instances it is completely harmless. Laparoscopic liver surgery with these techniques used may pose a risk of gas embolization with clinical implications. Monitoring for such events is probably to be recommended.     

Antifogging effects of a socket-type device with the superhydrophilic, titanium dioxide–coated glass for the laparoscope

Background Lens fogging during laparoscopic surgery extensively deteriorates operative field visibility and may provoke serious complications. Methods A simulation model study was conducted using a conventional laparoscope, a conventional laparoscope plus heating (100°C, 10 s), a conventional laparoscope plus surfactant, and a conventional laparoscope plus both a titanium dioxide (TiO₂)-coated glass (with ≥15 h of preoperative ultraviolet irradiation) and a water supply. For each, the time from laparoscope insertion into the peritoneal cavity to fogging-induced interruption of surgery was measured. Results The TiO₂-coated glass had unique verified properties of exerting antifogging effects on the oil film after 15 or more hours of previous ultraviolet irradiation, and of inversely accelerating fogging after less than 15 h of previous ultraviolet irradiation. The clinical study showed later fogging with the TiO₂-coated glass model, which successfully completed surgery without retraction of the laparoscope from the peritoneal cavity, as compared with the other models. Conclusion An antifogging device using superhydrophilic TiO₂-coated glass was very effective in preventing fogging during laparoscopic surgery.     

Arterial to endtidal carbon dioxide gradient during pediatric laparoscopic fundoplication

Background: Discrepancies between arterial carbon dioxide (P_aCO₂) and endtidal carbon dioxide (ETCO₂) measures have been demonstrated in ventilated children with cyanotic congenital heart disease, infants with respiratory failure and during visceral and urological laparoscopic surgery. Objectives: Our objective was to assess the extent of the P_aCO₂ to ETCO₂ gradient in children during laparoscopic fundoplication. Methods: We prospectively collected data on patient characteristics, surgical conditions, pH, ETCO₂and P_aCO₂ during laparoscopic fundoplication using carbon dioxide insufflation in children age <29 months. Results: Data were collected on nine cases, four cases aged <1 year. A P_a‐ETCO₂ gradient was present during insufflation. The gradient was larger in children age less than 1 year but statistically significantly different from a value of zero, only at t = 30 min (mean = 8 mmHg, sem = 0.81, P = 0.004) and t = 60 min (mean = 5 mmHg, sem = 1, P = 0.014). Minute ventilation was increased from 20% to 100% to control ETCO₂. Conclusions: ETCO₂ may not accurately represent arterial values during laparoscopic fundoplication, especially in the infant when carbon dioxide insufflation is used. Consideration should be given to placing an arterial line for blood gas measurement in some patients.     

Photodynamic therapy with the phthalocyanine photosensitizer Pc 4: the case experience with preclinical mechanistic and early clinical-translational studies

Photodynamic therapy (PDT) is emerging as a promising non-invasive treatment for cancers. PDT involves either local or systemic administration of a photosensitizing drug, which preferentially localizes within the tumor, followed by illumination of the involved organ with light, usually from a laser source. Here, we provide a selective overview of our experience with PDT at Case Western Reserve University, specifically with the silicon phthalocyanine photosensitizer Pc 4. We first review our in vitro studies evaluating the mechanism of cell killing by Pc 4-PDT. Then we briefly describe our clinical experience in a Phase I trial of Pc 4-PDT and our preliminary translational studies evaluating the mechanisms behind tumor responses. Preclinical work identified (a) cardiolipin and the anti-apoptotic proteins Bcl-2 and Bcl-xL as targets of Pc 4-PDT, (b) the intrinsic pathway of apoptosis, with the key participation of caspase-3, as a central response of many human cancer cells to Pc 4-PDT, (c) signaling pathways that could modify apoptosis, and (d) a formulation by which Pc 4 could be applied topically to human skin and penetrate at least through the basal layer of the epidermis. Clinical-translational studies enabled us to develop an immunohistochemical assay for caspase-3 activation, using biopsies from patients treated with topical Pc 4 in a Phase I PDT trial for cutaneous T-cell lymphoma. Results suggest that this assay may be used as an early biomarker of clinical response.     

SiO2刺激矽肺肺泡巨噬细胞对MMP-9和TIMP-1表达的影响

目的 探讨SiO2对矽肺患者的肺泡巨噬细胞(AM)基质金属蛋白酶-9(MMP-9)及金属蛋白酶组织抑制因子(TIMP)-1表达的影响.方法 收集矽肺患者肺泡AM,体外经SiO2刺激3、6、12、18、24、36 h,分别用明胶酶谱法和免疫细胞化学方法检测AM中TIMP-1、MMP-9蛋白表达和MMP-9活力.结果 实验组AM中6、12、18、24 h MMP-9的蛋白表达增强,在18 h时最高(积分吸光度值为0.386±0.037),与同期对照组相比,差异均有统计学意义(P＜0.05).实验组12、18、24、36h AM中MMP-9活力的表达增强,在24 h最强(吸光度值3.061±0.153),与同期对照组相比,差异均有统计学意义(P＜0.05).实验组与对照组各时间点TIMP-1蛋白表达比较,差异无统计学意义(P＞0.05).结论 体外SiO2刺激矽肺肺泡AM可影响MMP-9蛋白及其活力的表达.     

老年人单肺通气时呼气末二氧化碳监测的可信度

目的 观察老年人单肺通气(OLV)麻醉时P_(ET)CO_2C_2和PaCO_2的相关性,以评定P_(ET)CO_2监测在老年人单肺通气麻醉的可信度.方法 37例老年肺部肿瘤患者,胸腔镜下行胸部肿瘤切除、活检或肿瘤根治术,采用静脉复合全麻,术中行OLV.记录麻醉前及OLV 30、60、90、120、180和240min时BP、HR、SpO_2、P_(ET)CO_2和动脉血气,计算氧合指数(PaO_2/FiO_2)、动脉-呼气末二氧化碳分压差(P_(a-ET)CO_2),及对应时间点P_(ET)CO_2和PaCO_2的相关性.结果 除OLV 180 min时点外,术中各时点PaCO_2与P_(ET)CO_2有较好的相关性.术中5例发生低氧血症.结论 老年人OLV麻醉中P_(ET)CO_2不能完全反映PaCO_2的变化,长时间OLV者需同时行血气分析,以保证老年人的安全.     

Maternal exposure to ambient air pollutants and risk of congenital anomalies

Studies have suggested an association between maternal exposure to ambient air pollution and risk of congenital anomaly. The aim of this study is to investigate the association between exposure to black smoke (BS; particulate matter with aerodynamic diameter <4 μg/m³) and sulphur dioxide (SO₂) during the first trimester of pregnancy and risk of congenital anomalies. We used a case-control study design among deliveries to mothers resident in the UK Northern health region during 1985-1990. Case data were ascertained from the population-based Northern Congenital Abnormality Survey and control data from national data on all births. Data on BS and SO₂ from ambient air monitoring stations were used to average the total pollutant exposure during the first trimester of pregnancy over the daily readings from all monitors within 10 km of the mother's residence. Logistic regression models estimated the association via odds ratios. A significant but weak positive association was found between nervous system anomalies and BS (OR=1.10 per increase of 1000 μg/m³ total BS; 95% CI: 1.03, 1.18), but not with other anomaly subtypes. For SO₂, a significant negative association was found with congenital heart disease combined and patent ductus arteriosus: OR significantly <1 for all quartiles relative to the first quartile. The relationship between SO₂ levels and other anomaly subtypes was less clear cut: there were either no significant associations or a suggestion of a U-shaped relationship (OR significantly <1 for moderate compared to lowest levels, but not with high SO₂ levels). Overall, maternal exposure to BS and SO₂ in the Northern region had limited impact on congenital anomaly risk. Studies with detailed exposure assessment are needed to further investigate this relationship.