Different low constant flows can equally determine the lower inflection point in acute respiratory distress syndrome patients

Among the possible techniques to obtain the pressure-volume (P x V) curve at the bedside the low constant flow (CF) is the easiest and quickest one. However, the best value for CF to perform a good semi-static P x V curve is still to be determined. The purpose of this study was to evaluate the influence of 4 different CFs (1, 2, 5, and 10 L/min) on determination of lower inflection point of the P x V curve (L-Pflex) and upper inflection point of the P x V curve (U-Pflex) on the maximum slope and on the inspiratory work of breathing (up to volume of 1.35 L; inspiratory work L/cm H2O), comparing the volume estimated from the CF with the measured volume obtained by the respiratory inductive plethysmograph. The design was a prospective study, and the setting was an adult medical intensive care unit of a university hospital. There were 7 acute respiratory distress syndrome (ARDS) patients, less than 5 days of installation, after the standardization of lung volume history received sequentially from 4 different low inspiratory CFs in 2 trials. The P x V curve lasted from 73 +/- 1.6 s (1 L/min) to 8.8 +/- 0.69 s (10 L/min). The L-Pflex differed in the 2 performed trials (p = 0.04). There was no difference of L-Pflex among the 4 CFs comparing the 3 methods (p = 0.072) used for its calculation as well as comparing the estimated and the measured volume (p = 0.456). The maximum slope decreased significantly while increasing the flow from 1 to 10 L/min just in the estimated volume (p = 0.03). The inspiratory work did not increase with the increment of the flow either in the estimated volume (p = 0.217) or in the measured volume (p = 0.149). The U-Pflex differed among the trials (p = 0.003) and the methods used for its calculation (p < 0.01). Constant flows from 1 to 10 L/min can equally determine L-Pflex in ARDS patients and is an easy and quick way to obtain the L-Pflex in order to optimize positive end expiratory pressure (PEEP) in ARDS patients.     

Derecruitment of the lung induced by stepwise lowering of positive end-expiratory pressure in patients with adult respiratory distress syndrome

BACKGROUND AND OBJECTIVE: It has recently been suggested that recruitment proceeds far above the lower inflection point of the elastic pressure-volume (Pel/V) curve of the respiratory system. Accordingly, the value of the lower inflection point as a guide to set the positive end-expiratory pressure (PEEP) has been challenged. Our aim was to evaluate the derecruitment induced by stepwise decreasing PEEP levels. METHODS: Seven consecutive sedated and paralysed patients with acute respiratory distress syndrome were studied. Multiple Pel/V curves of the respiratory system were recorded at PEEP levels progressively decreasing in steps of 3.75 cmH2O from + 15 to zero according to the principles of the low flow inflation method. RESULTS: Multiple Pel/V curves shifted towards lower volumes at decreasing PEEP. Dynamic compliance was higher for Pel/V curves recorded from lower PEEP levels. A high correlation (r = 0.99) was found between dynamic compliance and PEEP. The lower inflection point was on average 9.2 cmH2O. However, the transition between the lower segment and the linear part of the Pel/V curve was in general smooth to the eye. The upper inflection point was on average 23.8 cmH2O. A high correlation (r = 0.98) between the upper inflection point and PEEP was found. CONCLUSIONS: The lower inflection point is a poor indicator of alveolar closure. The evaluation of derecruitment induced by a stepwise reduction in PEEP seems to be more useful than individual titration of PEEP and tidal volume in patients with adult respiratory distress syndrome.     

Effects of Fentanyl on Respiratory Pressure-Volume Relationship in Supine Anesthetized Children

The effects of fentanyl on total respiratory pressure-volume relationship were studied in 12 supine, anesthetized (thiopental, succinylcholine, halothane, N₂O/O₂) children, 5, 10 and 15 min after administration of fentanyl, 3 μg/kg (Group F) and at similar intervals in 11 control, anesthetized children who did not receive fentanyl (Group C). Lung and chest wall pressure-volume relationships were measured in five children from Group F and in six from Group C. Compliance values were estimated from the linear part of PVR curves. In Group F, a significant decrease was observed at 5, 10 and 15 min (maximum 29%) for total compliance and at 15 min (maximum 26 %) for lung compliance. Chest wall compliance was reduced (maximum 45 %) at 15 min, but not significantly. In Group C., no change in compliances was noted. The comparison between the two groups for total, chest wall and lung compliances showed a significant decrease in these three parameters at 15 min in children receiving fentanyl. The decrease of chest wall compliance can be explained by increased muscle tone, but the mechanism of decreased lung compliance awaits further study.     

Triple-phase computed tomography and intraoperative flow measurements improve the management of portosystemic shunts during liver transplantation.

Ligation of portosystemic shunts in patients with cirrhosis undergoing liver transplantation has been recommended to avoid insufficient portal vein (PV) flow. Shunts are not always recognized pretransplantation because intraoperative PV flow assessment is not routinely attempted. As a result of a posttransplantation PV thrombosis in a recipient with a large portosystemic shunt and a PV flow <1 L/minute, we employed triple-phase computed tomography with vascular reconstruction and intraoperative graft flow measurement to determine the need for inflow modification in our next 16 patients with large portosystemic shunts. Subsequently, 6 patients with large portosystemic shunts and PV flows 相似文献   

Pressure-volume relationships in acute lung injury: methodological and clinical implications

BACKGROUND: Pressure-volume relationships (PV curves) are the only available method for bedside monitoring of respiratory mechanics. Alveolar recruitment modifies the results obtained from the PV curves. We hypothesized that method-related differences may influence PV-curve guided ventilatory management. METHODS: Twelve acute lung injury (ALI) patients [PaO2/FiO2 13.0 +/- 1.5 kPa (97.6 +/- 11.3 mmHg), bilateral pulmonary infiltrates] were studied. Two PV curves [one at variable, and another at constant level of positive end-expiratory pressure (PEEP)] were obtained from each patient using constant inspiratory flow and end-inspiratory and -expiratory occlusions. Upper and lower inflection points (UIP, LIP) were estimated. Recruitment due to PEEP and during inflation was assessed by respiratory inductive plethysmography (RIP). RESULTS: (1) Pressure-volume curves at constant PEEP tended to provide higher LIP values compared with curves at variable PEEP (mean difference +/- SEM 5.1 +/- 1.9 cmH2O); and (2) recruitment occurred throughout the PV curve with no relationship with LIP or UIP. CONCLUSION: Pressure-volume curves obtained using variable PEEP translate a different physiological reality and seem to be clinically more relevant than curves constructed at constant PEEP. If curves constructed at constant PEEP are used to set the ventilator, unnecessarily high PEEP levels may be used. Respiratory inductive plethysmography technology may be used for monitoring of recruitment at the bedside.     

Measurement of pressure-volume curves in patients on mechanical ventilation. Methods and significance

In critically ill patients measurements of pressure volume curves has been suggested as a method for assessing the severity of lung injury and for monitoring the evolution of the lung disease; it can also guide the ventilatory adjustments to optimize the mechanical ventilation. The static pressure-volume curves are impaired in acute respiratory distress syndrome (ARDS). The evaluation of the lower and upper inflection point on the pressure-volumes curves at the bedside of patients with acute respiratory failure means to apply a "protective ventilatory strategy". The combined application of positive end expiratory pressure (PEEP) to the level of alveolar recruitment and low tidal volume (< 6 ml/kg) ameliorates the lung function and decrease mortality in ARDS patients. Routine monitoring with continuous technique is easy and develops good therapeutic practice.     

Variables used to set PEEP in the lung lavage model are poorly related

Setting an appropriate positive end-expiratory pressure (PEEP) value is determined by respiratory mechanics, gas exchange and oxygen transport. As these variables may be optimal at different PEEP values, a unique PEEP value may not exist which satisfies both the demands of minimizing mechanical stress and optimizing oxygen transport. In 15 surfactant- deficient piglets, PEEP was increased progressively. Arterial oxygenation and functional residual capacity (FRC) increased, while specific compliance of the respiratory system decreased. Static compliance increased up to a threshold value of PEEP of 8 cm H2O, after which it decreased. This threshold PEEP did not coincide with the lower inflection point of the inspiratory limb of the pressure-volume (PV) loop. Oxygen transport did not correlate with respiratory mechanics or FRC. In the lavage model, the lower inflection point of the PV curve may reflect opening pressure rather than the pressure required to keep the recruited lung open. Recruitment takes place together with a change in the elastic properties of the already open parts of the lung. No single PEEP level is optimal for both oxygen transport and reduction of mechanical stress.      

Inhaled nitric oxide delivery by anesthesia machines

Inhaled nitric oxide (NO) is a selective pulmonary vasodilator used to treat intraoperative pulmonary hypertension and hypoxemia. In contrast to NO delivered by critical care ventilators, NO delivered by anesthesia machines can be complicated by rebreathing. We evaluated two methods of administering NO intraoperatively: via the nitrous oxide (N(2)O) flowmeter and via the INOvent (Datex-Ohmeda, Madison, WI). We hypothesized that both systems would deliver NO accurately when the fresh gas flow (FGF) rate was higher than the minute ventilation (VE). Each system was set to deliver NO to a lung model. Rebreathing of NO was obtained by decreasing FGF and by simulating partial NO uptake by the lung. At FGF > or = VE (6 L/min), both systems delivered an inspired NO concentration ([NO]) within approximately 10% of the [NO] set. At FGF < VE and complete NO uptake, the N(2)O flowmeter delivered a lower [NO] (70 and 40% of the [NO] set at 4 and 2 L/min, respectively) and the INOvent delivered a higher [NO] (10 and 23% higher than the [NO] set at 4 and 2 L/min, respectively). Decreasing the NO uptake increased the inspired [NO] similarly with both systems. At 4 L/min FGF, [NO] increased by 10%-20% with 60% uptake and by 18%-23% with 30% uptake. At 2 L/min, [NO] increased by 30%-33% with 60% uptake and by 60%-69% with 30% uptake. We conclude that intraoperative NO inhalation is accurate when administered either by the N(2)O flowmeter of an anesthesia machine or by the INOvent when FGF > or = VE. IMPLICATIONS: Inhaled nitric oxide (NO) is a selective pulmonary vasodilator. In a lung model, we demonstrated that NO can be delivered accurately by a N(2)O flowmeter or by a commercial device. We provide guidelines for intraoperative NO delivery.     

The esophageal-tracheal combitube resistance and ventilatory pressures

STUDY OBJECTIVE: To measure resistance of the Combitube, a supraglottic ventilatory device used in the management of the patients with difficult airways, and its influence on delivered ventilatory pressures. DESIGN: Prospective study. SETTING: University-affiliated hospital. PATIENTS: A total of 20 patients with ASA status I or II who were scheduled for elective knee arthroscopy. INTERVENTIONS: (Part 2 of the study) After induction of general anesthesia and insertion of the Combitube, mechanical ventilation was initiated. Airway pressures were measured using fluid-filled pressure lines at the Y-piece (P(Y-piece)) of the breathing system and in the oropharynx (P(oropharynx)) at a position 2 cm beyond the second proximal anterior hole of the Combitube. These pressures were simultaneously recorded and the pressure curves were compared. MEASUREMENTS: (Part 1 of the study) Resistance of the esophageal and the tracheal lumen of the 37-F Combitube and standard endotracheal tubes (with internal diameters of 6, 7, and 8 mm) was compared ex vivo with a Datex AS/3 monitor. Ventilation conditions were kept constant at a tidal volume of 0.5 L, frequency of 10 breaths per minute, and ramp flow waveform and peak flow of 1 L/s. MAIN RESULTS: Resistance of standard endotracheal tubes was inversely proportional to their diameters (16, 11, and 7 cm H(2)O/L per second for the tubes with internal diameters of 6, 7, and 8 mm, respectively). The resistance of the Combitube's tracheal lumen was 12 cm H(2)O/L per second. There was a significant difference in peak respiratory pressures between P(Y-piece) and P(oropharynx) (40 +/- 5 and 23 +/- 5 cm H(2)O, respectively). CONCLUSIONS: The Combitube has significant airflow resistance that should be considered when patients are mechanically ventilated because the delivered oropharyngeal pressure is significantly lower than the pressure measured at the anesthesia breathing system.     

左心辅助引流管的研制及体内外测试

目的　研制适合于经外周血管插管 ,进行左心辅助的左心引流管道。　方法　测试 4类 8种管道在体外模拟循环台上及犬体内的最大引流量及其抗折瘪性能。　结果　 ( 1)体外测试发现 ,不同型号的管道内径越大 ,最大引流量越大 ,各组间相比差异有极显著性 (P <0 0 1)。内径分别为 3 0、4 0、5 0、6 0mm ,壁厚 0 5mm聚乙烯管 (PV 0 5管 )的最大引流量分别是 ( 1 82± 0 0 3)、( 2 44± 0 0 3)、( 3 0 2± 0 0 4)、( 3 31± 0 0 3)L/min ;内径为 3 0、5 0mm ,壁厚 1 0mm的聚氯乙烯壁内镶嵌弹性钢丝管 (PVCSW 1 0管 )的最大引流量分别为 ( 1 83± 0 0 3)、( 3 0 7± 0 0 4)L/min ;内径 3 0mm、壁厚0 8mm的增塑聚乙烯管 (SPV 0 8管 )及壁厚 1 0mm的聚乙烯管 (PV 1 0管 )的最大引流量分别是( 1 82± 0 0 2 )、( 1 84± 0 0 2 )L/min。内径 3 0mm的 4种管道的最大流量相比 ,差异无显著性 (P >0 0 5 )。 ( 2 )各管道抗折瘪性能以PVCSW 1 0管最佳 ,其次是PV 1 0管 ;而SPV 0 8管、PV 0 5管最差。( 3)内径为 3 0mm的PVCSW 1 0管、PV 1 0管在犬体内的最大引流量与体外测试结果差异无显著性意义 (P >0 0 5 ) ;SPV 0 8管与PV 0 5管差异有非常显著性意义 (P <0 0 1)。　结论　PV 0 5管和SPV 0 8     

经皮肾镜取石术中采用压力控制容量保证通气模式对肺功能的影响

目的探讨压力控制容量保证通气模式(PCV-VG)在经皮肾镜取石术中对患者肺功能的影响。方法择期行经皮肾镜取石术患者40例,根据不同通气模式随机分为两组,每组20例,分别采用容量控制通气模式(V组)和PCV-VG(P组)。记录气管插管即刻(T0)、插管后15 min(T1)、30min(T2)、60min(T3)、120min(T4)的肺功能指标。结果 T2~T4时P组肺泡-动脉氧分压差(PA-aO2)、呼吸指数(RI)、吸气峰压(Ppk)、平台压(Pmean)明显低于V组(P0.05或P0.01),氧合指数(OI)、静态肺顺应性(Cst)明显高于V组(P0.05或P0.01)。结论 PCV-VG能够安全应用在经皮肾镜取石术,PCV-VG优于容量控制模式,术中有更低的气道压,血流动力学更平稳,更有利于对患者肺功能的保护。     

A Comparison of the Respiratory Effects of Sevoflurane and Halothane in Infants and Young Children

Background: This study compared the respiratory effects of sevoflurane with those of halothane in anesthetized infants and young children.

Methods: Infants were randomized to receive 1 minimum alveolar concentration (MAC) halothane or sevoflurane in a mixture of nitrous oxide and oxygen. Anesthetic management included the use of a laryngeal mask. Flow, airway pressure, and the end-tidal carbon dioxide pressure (PETCO(2)) were measured during spontaneous ventilation and airway occlusions. Respiratory inductive plethysmography was used to assess chest wall motion.

Results: Measurements were obtained in 30 infants and young children (mean (SD) age, 14.5 (5.9) months), 15 of whom received sevoflurane and 15 received halothane. Some respiratory depression, as indicated by a PETCO(2) of 45 mmHg (6 kPa), was present in both groups. Minute ventilation and respiratory frequency were significantly lower during sevoflurane than halothane anesthesia (4.5 compared with 5.4 (1/m2)/min, and 37.5 compared with 46.7 breaths/min, respectively, P < 0.05). There was no difference in respiratory drive, but the shape of the flow waveform differed according to anesthetic agent, with peak inspiratory flow reached later, and peak expiratory flow reached earlier, in the sevoflurane group. There was also significantly less thoracoabdominal asynchrony during sevoflurane anesthesia.     

Pressure-volume curve variations after a recruitment manoeuvre in acute lung injury/ARDS patients: implications for the understanding of the inflection points of the curve

BACKGROUND AND OBJECTIVE: Although the pressure-volume (P-V) curve has been proposed in the management of mechanically ventilated patients, its interpretation remains unclear. Our aim has been to study the variations of the P-V curve after a recruitment manoeuvre (RM). Our hypothesis was that the lower inflection point (LIP) represents the presence of compressive atelectases, so it should not change after lung recruitment, while the upper inflection point (UIP) reflects reabsorptive atelectases, and an effective recruitment should result in changes at this level. METHODS: Two P-V curves (quasi-static method) separated by an RM (40 cmH2O, two consecutive manoeuvres) were plotted in 35 postoperative patients with criteria of acute lung injury/acute respiratory distress syndrome (ARDS). LIP, UIP and expiratory inflection point (EIP) were defined as the first point where the curve consistently starts to separate from the line. RESULTS: One to six measurements were obtained per patient (73 procedures). Neither the lower nor the EIPs varied significantly after the RM (P = 0.11 and 0.35, respectively). An UIP was observed in 18 curves (25%) before the RM and disappeared on nine occasions after the recruitment. Similar results were obtained when first measurements only were analysed, and when the cause (pulmonary vs. extrapulmonary), severity of lung injury or duration of mechanical ventilation at first measurement were studied. CONCLUSIONS: An RM does not modify the LIP significantly, but induces the disappearance of the UIP in 50% of the cases in which this point is found.     

Positive end-expiratory pressure improves respiratory function in obese but not in normal subjects during anesthesia and paralysis.

BACKGROUND: Morbidly obese patients, during anesthesia and paralysis, experience more severe impairment of respiratory mechanics and gas exchange than normal subjects. The authors hypothesized that positive end-expiratory pressure (PEEP) induces different responses in normal subjects (n = 9; body mass index < 25 kg/m2) versus obese patients (n = 9; body mass index > 40 kg/m2). METHODS: The authors measured lung volumes (helium technique), the elastances of the respiratory system, lung, and chest wall, the pressure-volume curves (occlusion technique and esophageal balloon), and the intraabdominal pressure (intrabladder catheter) at PEEP 0 and 10 cm H2O in paralyzed, anesthetized postoperative patients in the intensive care unit or operating room after abdominal surgery. RESULTS: At PEEP 0 cm H2O, obese patients had lower lung volume (0.59 +/- 0.17 vs. 2.15 +/- 0.58 l [mean +/- SD], P < 0.01); higher elastances of the respiratory system (26.8 +/- 4.2 vs. 16.4 +/- 3.6 cm H2O/l, P < 0.01), lung (17.4 +/- 4.5 vs. 10.3 +/- 3.2 cm H2O/l, P < 0.01), and chest wall (9.4 +/- 3.0 vs. 6.1 +/- 1.4 cm H2O/l, P < 0.01); and higher intraabdominal pressure (18.8 +/-7.8 vs. 9.0 +/- 2.4 cm H2O, P < 0.01) than normal subjects. The arterial oxygen tension was significantly lower (110 +/- 30 vs. 218 +/- 47 mmHg, P < 0.01; inspired oxygen fraction = 50%), and the arterial carbon dioxide tension significantly higher (37.8 +/- 6.8 vs. 28.4 +/- 3.1, P < 0.01) in obese patients compared with normal subjects. Increasing PEEP to 10 cm H2O significantly reduced elastances of the respiratory system, lung, and chest wall in obese patients but not in normal subjects. The pressure-volume curves were shifted upward and to the left in obese patients but were unchanged in normal subjects. The oxygenation increased with PEEP in obese patients (from 110 +/-30 to 130 +/- 28 mmHg, P < 0.01) but was unchanged in normal subjects. The oxygenation changes were significantly correlated with alveolar recruitment (r = 0.81, P < 0.01). CONCLUSIONS: During anesthesia and paralysis, PEEP improves respiratory function in morbidly obese patients but not in normal subjects.     

麻醉诱导期开始采用肺保护性通气策略对妇科腔镜手术患者氧合及预后的影响

目的探讨从麻醉诱导期开始采用肺保护性通气策略对妇科腔镜手术患者氧合及预后的影响。方法选择在本院接受妇科腹腔镜手术的患者60例,随机分为三组,每组20例。采用间歇正压通气(IPPV)模式,氧浓度为100%,氧气流量2 L/min,吸呼比为1∶2。A组:从诱导期(即自主呼吸消失后,予面罩机械通气5 min)开始全程通气模式:VT6 ml/kg,RR 16次/分,PEEP为5cm H2O,每30分钟给予一次手法肺复张(手控通气,气道压力维持40 cm H2O,持续30 s);B组:诱导期通气模式:VT10 ml/kg,RR 10次/分,插管后通气模式:VT6 ml/kg,RR 16次/分,PEEP 5cm H2O,每30分钟给予一次手法肺复张;C组:全程通气模式均为VT10 ml/kg,RR 10次/分。记录插管前(T0)、气腹后(T1)、手术开始30 min(T2)、60 min(T3)、放气腹(T4)时的气道峰压(Ppeak)、平均气道压(Pmean)、计算肺顺应性(CL),并在T0、T1、T3、清醒拔管后吸空气5 min(T5)时抽取动脉血进行血气分析,计算氧合指数(OI)及肺内分流率(Qs/Qt)。记录患者术后并发症发生情况与住院天数。结果与T0时比较,T1~T4时三组Ppeak和Pmean均明显升高,C组Ppeak明显高于A组和B组(P0.05),T2时C组Pmean明显高于A组和B组(P0.05);三组CL在气腹后明显降低(P0.05),T3和T4时C组明显低于A组和B组(P0.05);三组PETCO2在气腹后明显升高,T2~T4时C组明显低于A组与B组(P0.05),A组与B组差异无统计学意义;三组OI随着时间延长变化差异无统计学意义,拔管后三组均明显降低(P0.05);三组Qs/Qt随着手术进行呈上升趋势,与T0时比较,三组在T3时明显上升(P0.05),C组明显大于A组和B组(P0.05);T5时均明显下降(P0.05)。术后仅C组有1例发生肺部感染。结论与常规通气相比,对接受妇科腔镜手术患者采用保护性肺通气策略能够明显改善患者的肺顺应性和氧合功能,有利于肺保护。     

根据静态压力-容量曲线指导开胸手术病人保护性单肺通气的效果

目的 评价根据静态压力.容积曲线(P-V曲线)设置开胸手术病人的呼气末正压(PEEP)行单肺通气(OLV)的效果.方法 择期行肺叶切除术病人120例,性别不限,年龄20～60岁,体重40～ 80 kg,ASA分级Ⅱ或Ⅲ级.双肺通气(TLV)3 min后,描绘准静态P-V曲线,确定P-V曲线低位拐点对应的压力(PLIP).采用随机数字表法,将病人随机分为5组(n＝24):对照组(C组)和不同保护性OLV方式组(P1～4组).C组PEEP为0,vT为10 ml/kg;P1组PEEP为0,vT为6ml/kg; P2组PEEP为PLIP,-2 cm H2O,VT为6ml/kg;P3组PEEP为PLIP,VT为6 ml/kg;P4组PEEP为PLIP+2 cmH2O,VT为6 ml/kg.分别于TLV和OLV呼吸力学指标平稳后,记录气道峰压、气道平台压、气道阻力和肺顺应性.分别于麻醉诱导前、TLV 20 min和OLV 20 min时,取动脉血样,进行血气分析,计算肺内分流率.分别于OLV开始时和OLV结束时采集动脉血样,采用酶联免疫吸附法测定血浆II-6和TNF-α的浓度.结果 与C组比较,P4组TLV和OLV呼吸力学指标平稳后气道峰压和气道平台压升高,气道阻力降低,OLV结束时血浆IL-6浓度降低,P1组、P2组、P3组和P4组PaC02升高(P<0.05或0.01);P1组、P2组和P3组各呼吸力学指标、血气分析指标和血浆IL-6和TNF-α的浓度比较差异无统计学意义(P＞0.05).与P1组、P2组和P3组比较,P4组气道峰压和气道平台压升高,OLV结束时血浆IL-6浓度降低(P<0.05或0.01).结论 VT为6 ml/kg,根据PLIP+2 cm H2O确定PEEP,有助于改善开胸手术病人的氧合,抑制炎性反应,是保护性OLV的有效手段.     

不同穿刺体位在腰-硬联合麻醉剖宫产术中的比较

目的比较不同穿刺体位在腰-硬联合麻醉(CSEA)剖宫产术中的效果。方法拟行剖宫产术的足月妊娠产妇90例,随机分为两组,每组45例。选择L3~4椎间隙作为穿刺点。R组右侧穿刺腰麻后保持穿刺体位2 min后左倾30°仰卧至手术开始,L组左侧穿刺腰麻后仰卧位,并调整手术床左倾30°直至手术开始。腰麻药物均为1.0%罗哌卡因1.5 ml+10%葡萄糖0.5 ml。观察腰麻药物注入后15 min内产妇感觉阻滞效应及不良反应情况,记录新生儿Apgar评分,检测脐动脉血p H值。结果 R组产妇最终阻滞平面明显低于L组,达到最终阻滞平面所需时间明显短于L组(P0.05)。R组麻黄碱用量为0(0~6)mg,明显低于L组的6(0~12)mg(P0.05)。R组脐动脉血p H值明显高于L组(P0.05)。两组新生儿Apgar评分差异无统计学意义。结论剖宫产术采用右侧卧位穿刺注药后保持穿刺体位2 min后30°仰卧,其麻醉效果优于左侧卧位穿刺后30°仰卧体位。     

Single-dose dexmedetomidine reduces agitation after sevoflurane anesthesia in children

Emergence agitation is a common side effect of sevoflurane anesthesia in children. Dexmedetomidine, because of its sedative and analgesic properties, might be useful for the management of this adverse effect. We studied the effect of dexmedetomidine on recovery characteristics in 90 children aged 1 to 10 yr scheduled to undergo superficial lower abdominal and genital surgery. After inhaled induction with sevoflurane, patients were randomly assigned to receive saline (Group 1, n = 30), dexmedetomidine 0.15 micro g/kg (Group 2, n = 30), or dexmedetomidine 0.30 micro g/kg (Group 3, n = 30). After a laryngeal mask airway insertion a caudal block was performed in all patients. Maintenance of anesthesia was with 1% end-tidal sevoflurane and 50% nitrous oxide and spontaneous ventilation. Intraoperative hemodynamic and respiratory variables were recorded every 5 min. At the end of anesthesia time to eyes opening (TEO) and characteristics of emergence were recorded. General and intraoperative variables were similar in the 3 groups. The TEO was 7.5 +/- 5.0 min in Group 1, 8.2 +/- 5.0 min in Group 2, and 9.8 +/- 4.0 min in Group 3 (NS). The incidence (95% confidence interval) of agitation was 37% (20%-54%) in Group 1, 17% (4%-30%) in Group 2, and 10% (0%-21%) in Group 3 (P < 0.05). Paired comparisons showed a significant difference for Group 1 versus Group 3 (P < 0.05, 95% confidence interval of the difference: 7%-47%). The time to discharge from the postanesthesia care unit was similar for the 3 groups. We conclude that a dose of dexmedetomidine 0.3 micro g/kg administered after induction of anesthesia reduces the postsevoflurane agitation in children and with no adverse effects. IMPLICATIONS: In children undergoing surgery using sevoflurane anesthesia, dexmedetomidine 0.3 micro g/kg administered in 10 min after induction reduced the incidence of emergence agitation from 37% in the control group to 10%. No adverse effects attributable to dexmedetomidine were observed.     

An on-line computer procedure for the analysis of pressure-volume relations in ventilated intensive care patients

The inspiratory pressure-volume relationship (PV curve) describes elastic and viscous attributes of the respiratory system. The most frequently considered parameter is the quasi-static compliance, which has been used for evaluating optimal positive end-expiratory pressure (PEEP) in the treatment of patients with adult respiratory distress syndrome (ARDS). According to Falke and others, this method has not fulfilled its purpose. Since certain effects of PEEP ventilation such as the recruitment of lung areas on the one hand and the overdilatation of opened areas on the other may be reflected in different courses of parts of the PV curve, the consideration of discrete points on this curve may aid in developing mechanical criteria for the evaluation and control of artificial ventilation. Depending on lung elasticity, resistance, and tidal volume, the PV curve has a characteristic shape: initially it increases progressively until a certain airway pressure is reached, then it turns to a regressive incline. As irregularities of the PV curve due to oscillations of the respiratory gases cannot be avoided in practice, certain points (e.g. the inflection point) cannot be determined directly on the basis of the measured sample pairs. Therefore, we developed an on-line analysis of the PV curve, applying a polynomial function by least-square-fit procedure. The transthoracic pressure gradient was measured at the endotracheal tube by a Statham transducer. Inspiratory flow was measured using a Fleisch pneumotachograph with a differential pressure transducer. The flow-pressure signals were registered with a personal computer including an analog/digital interface board. Sample time was set for 10 ms.(ABSTRACT TRUNCATED AT 250 WORDS)     

An interchangeable Mapleson A-E breathing system is practical and cost effective

BACKGROUND: In locations where oxygen and anesthesia gas supplies are limited, and where circle systems are not practical, means to reduce fresh gas flow during maintenance of inhalational anesthesia are of potential value. We investigated whether a common transport breathing apparatus could be modified to allow interchange between Mapleson D (Map-D) and Mapleson A (Map A) configurations. METHODS: A common Map-D transport system was converted to a Map-A system by switching positions of the exhaust valve and the elbow connector where fresh gas is delivered; these two breathing systems were compared in this study. The key question was whether rebreathing of CO2 could be eliminated at a lower fresh gas flow rate (FGF) with the Map-A design. A structured protocol was followed. RESULTS: A mean decrease in FGF of 2.8 l/min was seen with the Map-A apparatus when compared with the Map-D (P=0.003). With no significant differences in physiologic or anesthetic variables, FGF/V(E) was significantly lower with the Mapleson A configuration than with the Mapleson D system design (1.1 vs. 1.8; P=0.007). The extent to which FGF could be lowered when switching between Mapleson D and A systems correlated strongly with the patients' respiratory rate while under anesthesia (r=0.45, P<0.01). CONCLUSIONS: Cost and resource savings can be realized through the use of a breathing system modification that achieves appropriate ventilation at lower fresh gas flows.