Effects of Recruitment Maneuver on Atelectasis in Anesthetized Children

Background: General anesthesia is known to promote atelectasis formation. High inspiratory pressures are required to reexpand healthy but collapsed alveoli. However, in the absence of positive end-expiratory pressure (PEEP), reexpanded alveoli collapse again. Using magnetic resonance imaging, the impact of an alveolar recruitment strategy on the amount and distribution of atelectasis was tested.

Methods: The authors prospectively randomized 24 children who met American Society of Anesthesiologists physical status I or II criteria, were aged 6 months-6 yr, and were undergoing cranial magnetic resonance imaging into three groups. After anesthesia induction, in the alveolar recruitment strategy (ARS) group, an alveolar recruitment maneuver was performed by manually ventilating the lungs with a peak airway pressure of 40 cm H2O and a PEEP of 15 cm H2O for 10 breaths. PEEP was then reduced to and kept at 5 cm H2O. The continuous positive airway pressure (CPAP) group received 5 cm H2O of continuous positive airway pressure without recruitment. The zero end-expiratory pressure (ZEEP) group received neither PEEP nor the recruitment maneuver. All patients breathed spontaneously during the procedure. After cranial magnetic resonance imaging, thoracic magnetic resonance imaging was performed.

Results: The atelectatic volume (median, first and third standard quartiles) detected in the ZEEP group was 1.25 (0.75-4.56) cm3 in the right lung and 4.25 (3.2-13.9) cm3 in the left lung. The CPAP group had 9.5 (3.1-23.7) cm3 of collapsed lung tissue in the right lung and 8.8 (5.3-28.5) cm3 in the left lung. Only one patient in the ARS group presented an atelectasis of less than 2 cm3. An uneven distribution of the atelectasis was observed within each lung and between the right and left lungs, with a clear predominance of the left basal paradiaphragmatic regions.     

Use of a Vital Capacity Maneuver to Prevent Atelectasis after Cardiopulmonary Bypass: An Experimental Study

Background: Respiratory failure secondary to cardiopulmonary bypass (CPB) remains a major complication after cardiac surgery. The authors previously found that the increase in intrapulmonary shunt was well correlated with the amount of atelectasis. They tested the hypothesis that post-CPB atelectasis can be prevented by a vital capacity maneuver (VCM) performed before termination of the bypass.

Methods: Eighteen pigs received standard hypothermic CPB (no ventilation during bypass). The VCM was performed in two groups and consisted of inflating the lungs during 15 s to 40 cmH2 O at the end of the bypass. In one group, the inspired oxygen fraction (FIO2) was then increased to 1.0. In the second group, the FIO2 was left at 0.4. In the third group, no VCM was performed (control group). Ventilation-perfusion distribution was measured with the inert gas technique and atelectasis by computed tomographic scanning.

Results: Intrapulmonary shunt increased after bypass in the control group (from 4.9 +/- 4% to 20.8 +/- 11.7%; P < 0.05) and was also increased in the vital capacity group ventilated with 100% oxygen (from 2.2 +/- 1.3% to 6.9 +/- 2.9%; P < 0.01) but was unaffected in the vital capacity group ventilated with 40% oxygen. The control pigs showed extensive atelectasis (21.3 +/- 15.8% of total lung area), which was significantly larger (P < 0.01) than the proportion of atelectasis found in the two vital capacity groups (5.7 +/- 5.7% for the vital capacity group ventilated with 100% oxygen and 2.3 +/- 2.1% for the vital capacity group ventilated with 40% oxygen.     

Effect of Carbon Dioxide Pneumoperitoneum on Development of Atelectasis during Anesthesia, Examined by Spiral Computed Tomography

Background: Anesthesia per se results in atelectasis development in the dependent regions of the lungs. The effect of pneumoperitoneum on atelectasis formation is not known. The aim of the current study was to measure by spiral computed tomography the effect of carbon dioxide pneumoperitoneum for laparoscopic surgery on the development of atelectasis, overall lung volume, and regional tissue volumes of gas and tissue.

Methods: Seven patients (American Society of Anesthesiologists physical status I), scheduled to undergo laparoscopic cholecystectomy, were observed. After induction of anesthesia, the patients were mechanically ventilated and positioned supine on the computed tomography table. Tomography of the lungs (10 mm spiral) was performed before and 10 min after induction of carbon dioxide pneumoperitoneum at an intraabdominal pressure of 11-13 mmHg. The Student t test was used for statistical analysis. A P value less than 0.05 was considered significant.

Results: Induction of pneumoperitoneum increased the mean atelectasis volume in the dependent lung regions by 66% (range, 11-170%). The overall lung volume and gas as well as tissue volume significantly decreased. Relative to the total lung volume, lung tissue volume increased, while gas volume decreased significantly. Both upper and lower lobes reacted the same way. A cranial displacement of the diaphragm between 1 and 3 cm (mean, 1.9 cm) was registered.     

Optimal Oxygen Concentration during Induction of General Anesthesia

Background: The use of 100% oxygen during induction of anesthesia may produce atelectasis. The authors investigated how different oxygen concentrations affect the formation of atelectasis and the fall in arterial oxygen saturation during apnea.

Methods: Thirty-six healthy, nonsmoking women were randomized to breathe 100, 80, or 60% oxygen for 5 min during the induction of general anesthesia. Ventilation was then withheld until the oxygen saturation, assessed by pulse oximetry, decreased to 90%. Atelectasis formation was studied with computed tomography.

Results: Atelectasis in a transverse scan near the diaphragm after induction of anesthesia and apnea was 9.8 +/- 5.2 cm2 (5.6 +/- 3.4% of the total lung area; mean +/- SD), 1.3 +/- 1.2 cm2 (0.6 +/- 0.7%), and 0.3 +/- 0.3 cm2 (0.2 +/- 0.2%) in the groups breathing 100, 80, and 60% oxygen, respectively (P < 0.01). The corresponding times to reach 90% oxygen saturation were 411 +/- 84, 303 +/- 59, and 213 +/- 69 s, respectively (P < 0.01).     

Effect of Low-dose Droperidol on the QT Interval during and after General Anesthesia: A Placebo-controlled Study

Background: Since the effects of antiemetic doses of droperidol on the QT interval have not been previously studied, the authors designed a randomized, double-blind, placebo-controlled study to evaluate the intraoperative and postoperative effects of small-dose droperidol (0.625 and 1.25 mg intravenous) on the QT interval when used for antiemetic prophylaxis during general anesthesia.

Methods: One hundred twenty outpatients undergoing otolaryngologic procedures with a standardized general anesthetic technique were enrolled in this study. After anesthetic induction and before the surgical incision, 60 patients were given either saline or 0.625 or 1.25 mg intravenous droperidol in a total volume of 2 ml. A standard electrocardiographic lead II was recorded immediately before and every minute after the injection of the study medication during a 10-min observation period. The QTc (QT interval corrected for heart rate) was evaluated from the recorded electrocardiographic strips. In 60 additional patients, a 12-lead electrocardiogram was obtained before and at specific intervals up to 2 h after surgery to assess the effects of droperidol and general anesthesia on the QTc. Any abnormal heartbeats or arrhythmias during the operation or the subsequent 2-h monitoring interval were also noted.

Results: Intravenous droperidol, 0.625 and 1.25 mg, prolonged the QT interval by an average of 15 +/- 40 and 22 +/- 41 ms, respectively, at 3-6 min after administration during general anesthesia, but these changes did not differ significantly from that seen with saline (12 +/- 35 ms) (all values mean +/- SD). There were no statistically significant differences among the three study groups in the number of patients with greater than 10% prolongation in QTc (vs. baseline). Although general anesthesia was associated with a 14- to 16-ms prolongation of the QTc interval in the early postoperative period, there was no evidence of droperidol-induced QTc prolongation after surgery. Finally, there were no ectopic heartbeats observed on any of the electrocardiographic rhythm strips or 12-lead recordings during the perioperative period.     

Heat Flow and Distribution during Induction of General Anesthesia

Background: Core hypothermia after induction of general anesthesia results from an internal core-to-peripheral redistribution of body heat and a net loss of heat to the environment. However, the relative contributions of each mechanism remain unknown. The authors evaluated regional body heat content and the extent to which core hypothermia after induction of anesthesia resulted from altered heat balance and internal heat redistribution.

Methods: Six minimally clothed male volunteers in an [nearly equal] 22 degrees Celsius environment were evaluated for 2.5 control hours before induction of general anesthesia and for 3 subsequent hours. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. To separate the effects of redistribution and net heat loss, we multiplied the change in overall heat balance by body weight and the specific heat of humans. The resulting change in mean body temperature was subtracted from the change in distal esophageal (core) temperature, leaving the core hypothermia specifically resulting from redistribution.

Results: Core temperature was nearly constant during the control period but decreased 1.6 plus/minus 0.3 degrees Celsius in the first hour of anesthesia. Redistribution contributed 81% to this initial decrease and required transfer of 46 kcal from the trunk to the extremities. During the subsequent 2 h of anesthesia, core temperature decreased an additional 1.1 plus/minus 0.3 degrees Celsius, with redistribution contributing only 43%. Thus, only 17 kcal was redistributed during the second and third hours of anesthesia. Redistribution therefore contributed 65% to the entire 2.8 plus/minus 0.5 degrees Celsius decrease in core temperature during the 3 h of anesthesia. Proximal extremity heat content decreased slightly after induction of anesthesia, but distal heat content increased markedly. The distal extremities thus contributed most to core cooling. Although the arms constituted only a fifth of extremity mass, redistribution increased arm heat content nearly as much as leg heat content. Distal extremity heat content increased [nearly equal] 40 kcal during the first hour of anesthesia and remained elevated for the duration of the study.     

全麻期间的血糖变化

目的：观察全麻手术期间的血糖变化。方法：对51例手术病人，在咪唑安定、芬太尼、丙泊酚、琥珀胆碱静脉诱导气管内插管、吸入异氟醚和笑气及静注维库溴铵复合麻醉下手术，分别在病室内、麻醉前、术毕和拔管后抽取静脉血测定血糖。结果：术前药使57．89％病人的血糖值有所下降，从6．21±1．8retool／L降至5．07±0．9mmol／L。病人进入手术室后，13例病人（34．21％）血糖升高，从5．20±1．06mmol／L升到6．39±1．61mmol／L．手术期间80％病人的血糖升高，从5．30±1．01mmol／L升到6．63±1．52mmol／L，其中高於正常值者为48％。拔管后的血糖变化呈两极分化趋势，血糖高於正常值者为34％，高於手术中血糖值者为26％（6．57±1．65mmol／LVS6．28±1.74mmol／L，高於麻醉前血糖值者为68％，6．16±1．21mmol／Lvs5．16±0．92mmol／L，有66％病人血糖低於术中水平，6．43±1．68mmol／LVS5．21±1.80mmol／L，其中12％病人的血糖低於正常值，且有2例的血糖降至危险的水平（1．1mmol／L）。结论：由于病人对疾病和手术的焦虑、疾病的影响、手术刺激、术前镇静药和麻醉药的影响，全麻手术期间的血糖可出现明显的变化．     

全麻术后苏醒延迟一例报告

女性患者,21岁,41千克,因下腹部反复疼痛不适二个月入院。CT提示骶前腹膜后包块。手术拟行“骶前腹膜后包块切除术”。患者既往体健,未诉其它特殊病史,实验室资料未见明显异常。     

Reexpansion of atelectasis during general anaesthesia may have a prolonged effect

Pulmonary atelectasis, as found during general anaesthesia, may be reexpanded by hyper-inflation of the lungs. The purpose of this study was to determine whether such a recruitment is maintained and whether this is accompanied by an improved gas exchange. We studied a consecutive sample of twelve lung healthy adults, scheduled for elective surgery. After induction of intravenous anaesthesia, the lungs were hyperinflated manually. The ventilationperfusion relationship (Va/Q) was estimated with the multiple inert gas method, and in six patients atelectasis was assessed by computed x-ray tomography. The mean pulmonary shunt was 7.5% of cardiac output after induction of anaesthesia and this decreased to 1.0% and 2.8% at 20 and 40 min after the recruitment manoeuvre. Perfusion of poorly ventilated lung regions (low Va/Q), however, increased from 3.7% to 10.6% and 7.8% at 20 and 40 min after the recruitment, respectively. The mean alveolar-arterial oxygen tension difference (P_A-ao₂) was 14.3 kPa after induction of anaesthesia and 11.1 kPa immediately after recruitment. Forty minutes later P_A-ao₂ was still 2.0 kPa lower than after induction of anaesthesia (95% conficence interval [CI] 0.3 to 3.8 kPa). P_A-ao₂ decreased more in obese patients. The mean area of atelectasis decreased from 9.0 cm² after induction of anaesthesia to 0.1 cm² immediately after recruitment, and there was a slow increase to 1.9 cm² (95% CI 0.0 to 3.9 cm²) 40 min later. During general anaesthesia in lung healthy patients, most of the reexpanded atelectatic lung tissue remains inflated for at least 40 min. The recruitment manoeuvre decreases pulmonary shunt, but increases low Va/Q. The net effect on gas exchange is a small reduction of P_A-ao₂.     

银花五汁饮对全麻术后患者呼吸道炎症反应的临床观察

目的:探讨银花五汁饮治疗全麻术后气管插管患者呼吸道炎症的临床效果。方法:选取2018年10月—2019年2月我院外科病区收治的行腹腔镜胆囊切除术的患者60例,分为对照组和观察组,每组30例。观察组:术后24 h采用常规治疗和银花五汁饮口服,2次/d,50 mL/次,连服3 d。对照组:术后24 h采用常规治疗和盐酸氨溴索注射液雾化吸入治疗,2次/d,连用3 d。比较手术日(治疗前)、术后第3天(治疗后)两组患者的咽喉疼痛症状积分及咳嗽咳痰症状积分,观察并比较患者的总有效率。结果:治疗前,两组的咽喉疼痛症状积分及咳嗽咳痰症状积分差异无统计学意义;治疗后,两组的咽喉疼痛症状积分及咳嗽咳痰症状积分均降低,且观察组明显低于对照组,差异有统计学意义(P<0.05)。观察组的总有效率为93.33%(28/30),高于对照组66.67%(20/30),差异有统计学意义(P<0.05)。结论:银花五汁饮具有养阴清肺、生津化痰的作用,对于全麻术后气管插管患者呼吸道炎症的治疗具有显著疗效。     

Experimental Determination of Heat Flow Parameters during Induction of General Anesthesia

Background: Alterations in body temperature result from changes in tissue heat content. Heat flow is a complex function of vasomotor status and core, peripheral, and ambient temperatures. Consequently it is difficult to quantify specific mechanisms responsible for observed changes in body heat distribution. Therefore the authors developed two mathematical models that independently express regional tissue heat production and the motion of heat through tissues in terms of measurable quantities.

Methods: The equilibrium model expresses the effective regional heat transfer coefficient in terms of cutaneous heat flux, skin temperature, and temperature at the center of the extremity. It applies at steady states and provides a ratio of the heat transfer coefficients before and after an intervention. In contrast, the heat flow model provides a time-dependent estimate of the heat transfer coefficient in terms of ambient temperature, skin temperature, and temperature at the center of the extremity.

Results: Each model was applied to data acquired in a previous evaluation of heat balance during anesthesia induction. The relation between the ratio of steady state regional heat transfer coefficients calculated using each model was linear. The effective heat transfer coefficient for the forehead (a core site) decreased approximately 20% after induction of anesthesia. In contrast, heat transfer coefficients in the six tested extremity sites more than doubled.     

定量脑电图监测全麻状态下意识的变化

目的：判断定量脑电图在全麻下监测意识的价值。方法：无神经济损务的健康志愿者,按０、０．２、０．３、０．４ＭＡＣ递增呼末异氟醚浓度,观察ｑＥＥＧ及指令反应变化,通过事后调查麻醉中的外显及内隐记忆。结果：按全麻下意识水平的１～４个阶段,第２与第１阶段相比,ｑＥＥＧＦ７、Ｆ８、Ａ１异联θ波相对功率明显降低（Ｐ〈０．０５）,第３与第２阶段相比,Ｏ１、及Ｏ２导联的α波相对功率明显降低（Ｐ〈０．０５）,Ｏ２与     

50例全麻患儿术中循环的管理

为维持全麻患儿术中循环的稳定,１９９９年１～１２月对５０例全麻心脏手术患儿术前失液量进行评估,准确计算术中输入量和输液速度,加强了术中、术后循环的管理,无１例发生并发症。提出做好术前准备,术中悉心观察和准确控制出入量是预防循环变化的重要措施。     

CH-6型CO_2测定仪在间断振荡通气的应用

本文就利用CH-6型CO_2测定仪对全麻期间患者呼气末CO_2浓度的监测进行了探讨。结果表明,该测定仪对通气期间CO_2浓度的测定结果与同时间内动脉血PaCO_2值之间有明显的相关性,基本上能正确反映通气效应,是一种可行的监测方法。