Gaseous homeostasis during low-flow anaesthesia

The object of this clinical study was to investigate the circle system gas homeostasis during low-flow anaesthesia using a technique designed to keep a constant inspired oxygen fraction of 0.30. Denitrogenation was adequately accomplished with mask preoxygenation, 10 l/min, for 1 min and an initial fresh gas flow of 5 l/min for 6 min after intubation. There was no need to wash out accumulated nitrogen at intervals, since the already low nitrogen concentration in the system tended to decrease after 1 h. The fresh gas flow of nitrous oxide to oxygen ratio and the inspiratory to end-expiratory oxygen concentration difference both reflected the uptake of nitrous oxide. The calculated rates of uptake of nitrous oxide, a subject of controversy, were in accordance with those found by Severinghaus and Barton & Nunn.     

Sevoflurane low-flow anaesthesia: best strategy to reduce Compound A concentration

BACKGROUND: To define the best strategy to reduce Compound A production in Sevoflurane low-flow anaesthesia by experiments in vitro and in vivo of different absorbers and different anaesthesia machines. METHODS: In vitro Compound A has been measured at 45 degrees C in vitro following Sevoflurane interactions with potassium hydroxide, sodium hydroxide, soda lime, Dragersorb 800 Plus and Amsorb, a new absorber that does not contain sodium or potassium hydroxide. In vivo Compound A concentration in the anaesthesia circuit (inspiratory branch) has been measured using an indirect sampling method through absorber vials (SKC) with active coal granules, during low flows (500 ml/min) general anaesthesia using soda lime, Dragersorb 800 Plus or Amsorb as absorber. Compound A was also measured during low flows (500 ml/min) general anaesthesia using as carbon dioxide absorber soda lime with different anaesthesia machines. RESULTS: In vitro at 45 degrees C Compound A concentration with soda lime and Dragersorb 800 Plus was about 10 times higher than with Amsorb. In vivo the Compound A concentrations in the inspiratory branch of the circuit were lower in the group with Amsorb. CONCLUSION: The Compound A production is minimal with Amsorb as carbon dioxide absorber.     

低流量紧闭循环麻醉用于婴幼儿唇腭裂修复术的临床研究

目的：探讨低流量紧闭循环麻醉用于婴幼儿唇腭裂修复术的可行性。方法：400例婴幼儿唇腭裂修复术患儿随机分为两组：Y-轻丁酸钠＋氯胺酮麻醉（Ⅰ组），低流量静吸复合麻醉组（Ⅱ组），每组200例。Ⅰ组诱导方法：静注氯胺酮2mg／kg，Y-羟丁酸钠，80mg／kg，充分表麻后捅管，术中保留自主呼吸、麻醉维持间断追加氯胺酮、Y-羟丁酸钠、Ⅱ组诱导方法：静注氧胺酮2mg/kg，芬太尼3ug／kg，阿曲库铵0．5mg／kg后插管术中控制呼吸，麻醉维持间断追加肌松利，小剂量芬太尼，术中新鲜氧流量设定为0．5L／min。术中监测患儿生命体征变化及PET CO2，记录插管成功＆p刻及拔管时患儿MAP、HR,SPO2，观察术毕拔管时间，完全清醒时间及拔管后有无呛咳、喉头水肿、喉痉挛等并发症。结果：与Ⅰ组相比，Ⅱ组插管后，HR、Bp明显低于Ⅰ组，spo2Ⅱ组高于Ⅰ组。术毕拔管时间及完全清醒时间Ⅰ组显著延长，Ⅰ组术毕拔管后井发症明显高于Ⅱ组。结论：低流量紧闭循环式麻醉用于唇腭裂修复术安全可靠，较传统麻醉方法具有术中麻醉平稳，清醒迅速，术毕并发症少等优点。     

Effect of low fresh gas flow rates on inspired gas composition in a circle absorber system

Study Objective: To determine the effects of fresh gas f ow on inspired gas composition during low flow anesthesia.

Design: Randomized trial with 2-hour observation periods in patients assigned to one of three groups.

Setting: Inpatient surgery clinic at a medical center.

Patients: Thirty-six patients undergoing abdominal surgery with low flow anesthesia. Interventions: Fresh gas flow was given at a starting rate of 5 L/min for 6 minutes. Thereafter, the fresh gas flow setting was nitrous oxide (N₂O) 1 L/min and oxygen (O₂) 0.6 L/min (Group 1), N₂O 0.5 L/min and O₂ 0.5 L/min (Group 2), and with a moderate surplus of N₂O and O₂ with respect to the patient's O₂ consumption (Group 3).

Measurements and Main Results: The inspired O₂ concentration (FIO₂) was measured using a paramagnetic technique, and N₂O levels were measured with infrared sensors; the inspired nitrogen concentration (FIN₂) was calculated by the following formula: (FIN₂) = 1 - FIO₂ - FIN₂O, where FIN₂O is the inspired N₂O concentration. After 1 hour of anesthesia, FIO₂ was significantly lower in Group 1 than in Groups 2 and 3 (p < 0.01), and FIN₂ was significantly higher in Groups 2 and 3 than in Group 1 (p < 0.01). After 2 hours of anesthesia, (FIN₂) returned to normal in Group 2 but continued to increase in Group 3. FIN₂O was close to 0.7% only in Group 1.

Conclusions: The same initial period of denitrogenation is not adequate to denitrogenate the circle system in all cases. The lower the fresh gas flow, the longer the initial period of denitrogenation should be. Various levels of fresh gas flow for low-flow anesthesia have been suggested, but none guarantees adequate control of inspired gas composition unless f owmeters are continuously adjusted.     

Tricuspid Regurgitation Is Associated With Increased Risk of Mortality in Patients With Low-Flow Low-Gradient Aortic Stenosis and Reduced Ejection Fraction: Results of the Multicenter TOPAS Study (True or Pseudo-Severe Aortic Stenosis)

ObjectivesThis study sought to examine the impact of tricuspid regurgitation (TR) on mortality in patients with low-flow, low-gradient (LF-LG) aortic stenosis (AS) and reduced left ventricular ejection fraction (LVEF).BackgroundTR is often observed in patients with LF-LG AS and low LVEF, but its impact on prognosis remains unknown.MethodsA total of 211 patients (73 ± 10 years of age; 77% men) with LF-LG AS (mean gradient <40 mm Hg and indexed aortic valve area [AVA] ≤0.6 cm²/m²) and reduced LVEF (≤40%) were prospectively enrolled in the TOPAS (True or Pseudo-Severe Aortic Stenosis) study and 125 (59%) of them underwent aortic valve replacement (AVR) within 3 months following inclusion. The severity of AS was assessed by the projected AVA (AVA_proj) at normal flow rate (250 ml/s), as previously described and validated. The severity of TR was graded according to current guidelines.ResultsAmong the 211 patients included in the study, 22 (10%) had no TR, 113 (54%) had mild (grade 1), 50 (24%) mild-to-moderate (grade 2), and 26 (12%) moderate-to-severe (grade 3) or severe (grade 4) TR. During a mean follow-up of 2.4 ± 2.2 years, 104 patients (49%) died. Univariable analysis showed that TR ≥2 was associated with increased risk of all-cause mortality (hazard ratio [HR]: 1.82, 95% confidence interval [CI]: 1.22 to 2.71; p = 0.004) and cardiovascular mortality (HR: 1.85, 95% CI: 1.20 to 2.83; p = 0.005). After adjustment for age, sex, coronary artery disease, AVA_proj, LVEF, stroke volume index, right ventricular dysfunction, mitral regurgitation, and type of treatment (AVR vs. conservative), the presence of TR ≥2 was an independent predictor of all-cause mortality (HR: 1.88, 95% CI: 1.08 to 3.23; p = 0.02) and cardiovascular mortality (HR: 1.92, 95% CI: 1.05 to 3.51; p = 0.03). Furthermore, in patients undergoing AVR, TR ≥3 was an independent predictor of 30-day mortality compared with TR = 0/1 (odds ratio [OR]: 7.24, 95% CI: 1.56 to 38.2; p = 0.01) and TR = 2 (OR: 4.70, 95% CI: 1.00 to 25.90; p = 0.05).ConclusionsIn patients with LF-LG AS and reduced LVEF, TR is independently associated with increased risk of cumulative all-cause mortality and cardiovascular mortality regardless of the type of treatment. In patients undergoing AVR, moderate/severe TR is associated with increased 30-day mortality. Further studies are needed to determine whether TR is a risk marker or a risk factor of mortality and whether concomitant surgical correction of TR at the time of AVR might improve outcomes for this high-risk population.     

深低温低流量灌注心脏直视手术中的脑干听觉诱发电位变化

为了解心脏直视手术时深低温低流量灌注对脑功能的影响，对６例复杂型先天性心脏病患儿在手术时进行了脑干听觉诱发电位（ＢＡＥＰ）监测。结果显示：（１）ＢＡＥＰ的各波峰和峰间潜伏期在体外循环前均正常；（２）肛温降至３５℃￣２５℃以下ＢＡＥＰ波形全部消失；（３）流量恢复后在升温过程中Ｖ波首先复出；（４）肛温恢复３５℃时波形恢复至深低温低流量灌注前，在体外循环前后ＢＡＥＰ的波峰和各峰间潜伏其无明显差异（Ｐ〉０     

Propofol and priapism

Propofol-induced priapism in a 25-year-old male confirmed by rechallenge is reported for its rarity and to create awareness among practitioners, because propofol is used frequently in India for the induction and maintenance of anesthesia or sedation. The probable mechanisms are highlighted. Because propofol causes low-flow priapism, early alleviation is essential to minimize and/or avert the long-term complications.