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.     

Positive end-expiratory pressure during induction of general anesthesia increases duration of nonhypoxic apnea in morbidly obese patients

Positive end-expiratory pressure (PEEP) applied during induction of anesthesia prevents atelectasis formation and increases the duration of nonhypoxic apnea in nonobese patients. PEEP also prevents atelectasis formation in morbidly obese patients. Because morbidly obese patients have difficult airway management more often and because arterial desaturation develops rapidly, we studied the clinical benefit of PEEP applied during anesthesia induction. Thirty morbidly obese patients were randomly allocated to one of two groups. In the PEEP group, patients breathed 100% O(2) through a continuous positive airway pressure device (10 cm H(2)O) for 5 min. After induction of anesthesia, they were mechanically ventilated with PEEP (10 cm H(2)O) for another 5 min until tracheal intubation. In the control group, the sequence was the same but without any continuous positive airway pressure or PEEP. We measured apnea duration until Spo(2) reached 90% and we performed arterial blood gases analyses just before apnea and at 92% Spo(2). Nonhypoxic apnea duration was longer in the PEEP group compared with the control group (188 +/- 46 versus 127 +/- 43 s; P = 0.002). Pao(2) was higher before apnea in the PEEP group (P = 0.038). Application of positive airway pressure during induction of general anesthesia in morbidly obese patients increases nonhypoxic apnea duration by 50%.     

Effects of pneumoperitoneum and reverse Trendelenburg position on cardiopulmonary function in morbidly obese patients receiving laparoscopic gastric banding

We prospectively evaluated the effects of pneumoperitoneum and reverse Trendelenburg position on cardiopulmonary function in 20 ASA physical status II-III morbidly obese patients (body mass index > 35 kg m(-2)) undergoing laparoscopic gastric banding. After general anaesthesia was induced, patients' lungs were ventilated using intermittent positive pressure ventilation (at measurement times, the following parameters were used: tidal volume 12 mL kg(-1) ideal body weight, respiratory rate of 12 bpm, an inspiratory to expiratory time ratio of 1:2). Haemodynamic variables, blood gas parameters, and lung/chest compliance were recorded: in the supine position, after induction of general anaesthesia (T0, baseline) and induction of pneumoperitoneum (T1); after placing the patient in a 25 degree reverse Trendelenburg position (T2); during the surgical time (T3); before deflating the abdomen (T4); after pneumoperitoneum resolution (T5), and before the end of anaesthesia, with the patient supine (T6). The PaO2, PaO2/FiO2 ratio, and lung/chest compliance decreased during the study. After the pneumoperitoneum had been resolved, lung/chest compliance but not oxygenation parameters returned to baseline values. The arterial to end-tidal CO2 tension difference progressively increased from 0.38+/-0.3 kPa (2.85+/-2.25 mmHg) (T0) to 0.63+/-0.3 kPa (4.73+/-2.25 mmHg) (T6). In morbidly obese patients, undergoing laparoscopic gastric banding, a CO2 pneumoperitoneum markedly affected gas exchange and lung/chest compliance, while positioning the patient in a 25 degree reverse Trendelenburg position had no beneficial effects.     

呼气末正压通气对阻塞性睡眠呼吸暂停综合征肥胖患者全麻术中呼吸功能的影响

目的 评价呼气末正压通气对阻塞性睡眠呼吸暂停综合征(OSAS)肥胖患者全麻术中呼吸功能的影响.方法 择期行悬雍垂腭咽成形术的OSAS患者40例,性别不限,年龄26 ～ 57岁,ASAⅠ或Ⅱ级,按照体重将患者分为2组(n=20):正常体重组(A组),BMI＜ 26 kg/m2;肥胖组(B组),BMI＞ 32 kg/m2.静脉注射咪达唑仑、异丙酚、舒芬太尼和顺阿曲库铵麻醉诱导,气管插管后先行非呼气末正压通气60 min,再行呼气末正压通气60 min,PEEP为8 cm H2O,维持PETCO2 35 ～ 45 mm Hg和气道峰压＜ 28 cm H2O.分别于气管插管后5 min(T1)、60min(T2)和120 min(T3)时记录胸肺顺应性(CL)和气道阻力(Raw).于清醒状态未吸纯氧前(T0)和T1-3时,采集足背动脉血样进行血气分析,计算氧合指数(PaO2/FiO2)、呼吸指数(RI)和生理无效腔(VD/VT).记录术后24h内不良反应的发生情况.结果 与T0时比较,B组T1和T2时PaO2/FiO2降低,RI升高(P＜0.05);与T1时比较,B组T3时PaO2/FiO2、CL升高,RI降低(P＜0.05);与A组比较,B组T1和T2时PaO2/FiO2和CL降低,T1-3时Raw,RI和VD/VT升高(P＜0.05).两组患者术后24 h内均未见心脑血管意外、气胸或肺水肿等不良反应的发生.结论 呼气末正压通气(PEEP 8 cm H2O)可抑制OSAS肥胖患者全麻术中肺不张,改善气体交换和胸肺顺应性.     

呼气末正压通气对二氧化碳气腹期间病人肺内分流的影响

目的观察二氧化碳气腹期间不同呼气末正压通气(PEEP)对肺内分流的影响。方法35例ASAⅠ或Ⅱ级经腹腔镜行中、上腹部手术的病人,随机分为P0组(不予PEEP)、P1组(予4mm Hg PEEP)、P2组(予7mm Hg PEEP)及P3组(予9mm Hg PEEP)。观察注气前5min、注气后30、60、120min的SBP、DBP、HR、SpO2、PETCO2及血气分析。结果与注气前5min比较,四组注气后30min SBP、DBP均显著增高、HR均显著增快(P<0.05或P<0.01);P3组注气后60、120min仍高于注气前(P<0.05或P<0.01),并且其HR、DBP高于P0组(P<0.05或P<0.01)。P0、P1、P3三组注气后PaCO2、动脉血-呼气末二氧化碳分压差(Pa-ETCO2)、肺泡氧分压-动脉血氧分压差(A-aDO2)均显著增高(P<0.05或P<0.01),PaO2注气后30、120min显著降低(P<0.05或P<0.01);P2组差异无统计学意义,并且其PaO2高于P0组,PaCO2、Pa-ETCO2、A-aDO2均低于P0组(P<0.05或P<0.01)。P2、P3两组注气后吸气峰压(Ppeak)均显著增高(P<0.01),并高于P0组(P<0.05或P<0.01)。结论气腹期间采用7mm Hg PEEP的通气模式能有效改善肺的换气功能,且对循环功能的影响较小。     

呼气末正压通气对二氧化碳气腹病人动脉血氧合的影响

目的观察腹腔镜手术期间呼气末正压通气(PEEP)对二氧化碳气腹病人动脉血氧合及血液动力学的影响。方法20例ASAⅠ～Ⅱ级经腹腔镜肾上腺肿块、输尿管上段结石及肾切除的病人,随机均分为P组和C组。50%氧气混合空气机械通气,P组予以5cmH2O的PEEP,C组无PEEP。观察建立二氧化碳气腹前(T0)、气腹后10min(T1)、30min(T2)、1h(T3)和2h(T4)的PaO2、PaCO2、HR及MAP。结果P组气腹期间PaO2有上升趋势,而C组呈下降趋势,气腹后1hC组显著低于P组(P<0.05)。两组MAP和HR波动均未超过11%。结论腹腔镜手术期间PEEP能促进动脉血氧合,对循环影响较小。     

呼气终末正压通气对麻醉中和术后肺血分流的影响

研究呼气末正压（ＰＥＥＰ）通气对全麻中及术后肺分流（Ｑｓ／Ｑｔ）的影响。选择２０例无心肺疾患行胆囊切除术患者，随机分为实验组（Ｐ组）和对照组（Ｚ组），在全麻诱导后分别行ＰＥＥＰ和呼气终末平压（ＺＥＥＰ）机械通气。并在麻醉前、麻醉后３０分钟、麻醉后１．５小时、麻醉后２．５小时和术后１小时取动脉和右心室混合静脉血行血气分析并计算分流量。结果表明，全麻期间 Ｐ组Ｑｓ／Ｑｔ逐渐减少，术后 １小时恢复至术前水平。 Ｚ组在麻醉中Ｑｓ／Ｑｔ持续升高，术后１小时仍显著高于术前。两组间各不同时期Ｑｓ／Ｑｔ有显著性差异（Ｐ＜０．０５）。结论：全麻可导致肺分流增加，并可持续至术后。全麻后即应用 ＰＥＥＰ通气可减少肺分流，对术后低氧血症和肺部并发症的发生起到预防作用，为患者呼吸功能恢复创造良好条件。     

Pituitary apoplexy during general anesthesia in beach chair position for shoulder joint arthroplasty

Pituitary apoplexy is a rare but potentially life-threatening clinical syndrome caused by the sudden enlargement of pituitary adenoma secondary to infarction and/or hemorrhage. It may be the first presentation of previously undiagnosed pituitary adenoma. Although various precipitating factors of pituitary apoplexy are indicated, the pathogenesis remains unknown. In this report, we describe for the first time a case of pituitary apoplexy developed explicitly during general anesthesia supplemented with interscalene brachial plexus block in beach chair or barbershop position for shoulder joint arthroplasty.     

Inert gas exchange during pneumoperitoneum at incremental values of positive end-expiratory pressure

Laparoscopy is a surgical technique for a growing variety of abdominal operations. In patients undergoing this procedure, arterial blood oxygenation and hemodynamics are frequently depressed. This study evaluated the effect of different levels of positive end-expiratory pressure (PEEP) during intraperitoneal CO(2) insufflation on the lung's ventilation-perfusion distribution in a porcine model. We studied 13 anesthetized pigs with an intraperitoneal pressure of 15 cm H(2)O applied at either incremental values of PEEP (5-20 cm H(2)O, increments of 5 cm H(2)O) or a constant PEEP of 5 cm H(2)O. The effects of CO(2) pneumoperitoneum on inert gas exchange and hemodynamics were examined with the multiple inert gas elimination technique. During pneumoperitoneum, gas exchange was most augmented by 15 and 20 cm H(2)O of PEEP. Although the differences in hemodynamics between the individual settings were insignificant, 10 cm H(2)O of PEEP provided the smallest impairment of hemodynamics. We conclude that PEEP of 15 H(2)O during pneumoperitoneum resulted in a modest hemodynamic depression but significant gas exchange augmentation in our experiment. IMPLICATIONS: Anesthetized pigs, with a pneumoperitoneum of 15 cm H(2)O, were treated either with incremental values of positive end-expiratory pressure (5-20 cm H(2)O, increments of 5 cm H(2)O) or with a constant positive end-expiratory pressure of 5 cm H(2)O. Fifteen and 20 cm H(2)O resulted in significantly improved pulmonary gas exchange compared with 5 cm H(2)O.     

Positive end-expiratory pressure optimization using electric impedance tomography in morbidly obese patients during laparoscopic gastric bypass surgery

BACKGROUND: Morbidly obese patients have an increased risk for peri-operative lung complications and develop a decrease in functional residual capacity (FRC). Electric impedance tomography (EIT) can be used for continuous, fast-response measurement of lung volume changes. This method was used to optimize positive end-expiratory pressure (PEEP) to maintain FRC. METHODS: Fifteen patients with a body mass index of 49 +/- 8 kg/m(2) were studied during anaesthesia for laparoscopic gastric bypass surgery. Before induction, 16 electrodes were placed around the thorax to monitor ventilation-induced impedance changes. Calibration of the electric impedance tomograph against lung volume changes was made by increasing the tidal volume in steps of 200 ml. PEEP was titrated stepwise to maintain a horizontal baseline of the EIT curve, corresponding to a stable FRC. Absolute FRC was measured with a nitrogen wash-out/wash-in technique. Cardiac output was measured with an oesophageal Doppler method. Volume expanders, 1 +/- 0.5 l, were given to prevent PEEP-induced haemodynamic impairment. RESULTS: Impedance changes closely followed tidal volume changes (R(2) > 0.95). The optimal PEEP level was 15 +/- 1 cmH(2)O, and FRC at this PEEP level was 1706 +/- 447 ml before and 2210 +/- 540 ml after surgery (P < 0.01). The cardiac index increased significantly from 2.6 +/- 0.5 before to 3.1 +/- 0.8 l/min/m(2) after surgery, and the alveolar dead space decreased. P(a)O2/F(i)O2, shunt and compliance remained unchanged. CONCLUSION: EIT enables rapid assessment of lung volume changes in morbidly obese patients, and optimization of PEEP. High PEEP levels need to be used to maintain a normal FRC and to minimize shunt. Volume loading prevents circulatory depression in spite of a high PEEP level.     

Lung collapse and gas exchange during general anesthesia: effects of spontaneous breathing, muscle paralysis, and positive end-expiratory pressure

Lung densities (atelectasis) and pulmonary gas exchange were studied in 13 supine patients with no apparent lung disease, the former by transverse computerized tomography (CT) and the latter by a multiple inert gas elimination technique for assessment of the distribution of ventilation/perfusion ratios. In the awake state no patient had clear signs of atelectasis on the CT scan. Lung ventilation and perfusion were well matched in most of the patients. Three patients had shunts corresponding to 2-5% of cardiac output, and in one patient there was low perfusion of poorly ventilated regions. CT scans after 15 min of halothane anesthesia and mechanical ventilation showed densities in dependent lung regions in 11 patients. A shunt was present in all patients, ranging from 1% in two patients (unchanged from the awake state) to 17%. Ventilation of poorly perfused regions was noted in nine patients, ranging from 1-19% of total ventilation. The magnitude of the shunt significantly correlated to the size of dependent densities (r = 0.84, P less than 0.001). Five patients studied during spontaneous breathing under anesthesia displayed both densities in dependent regions and a shunt, although of fairly small magnitude (1.8% and 3.7%, respectively). Both the density area and the shunt increased after muscle paralysis. PEEP reduced the density area in all patients but did not consistently alter the shunt. It is concluded that the development of atelectasis in dependent lung regions is a major cause of gas exchange impairment during halothane anesthesia, during both spontaneous breathing and mechanical ventilation, and that PEEP diminishes the atelectasis, but not necessarily the shunt.     

Effect of position and positive pressure ventilation on functional residual capacity in morbidly obese patients: a randomized trial

Purpose

In morbidly obese patients, the position and ventilation strategy used during pre-oxygenation influence the safe non-hypoxic apnea time and the functional residual capacity (FRC). In awake morbidly obese volunteers, we hypothesized that the FRC would be higher after a five-minute period of positive pressure ventilation compared with spontaneous ventilation at zero inspiratory pressure.

Methods

Using a prospective crossover randomized trial design, obese subjects underwent, in a randomized order, a combination of one of three positions, supine (S), beach chair (BC), and reverse Trendelenburg (RT), and one of two ventilation strategies, spontaneous ventilation at zero inspiratory pressure (ZEEP-SV) or with positive pressure (PP-SV) set to an inspiratory pressure of 8 cmH₂O, positive end-expiratory pressure of 10 cmH₂O, and fraction of inspired oxygen of 0.21.

Results

Seventeen obese volunteers with a mean (standard deviation; SD) body mass index of 50 (8) kg·m^?2 were included. Mean (SD) FRC in the three positions (S, BC, RT) was significantly higher using PP-SV compared with ZEEP-SV [2571 (477) vs 2215 (481) mL, respectively; mean difference, 356; 95% confidence interval (CI), 209 to 502; P < 0.001]. Mean (SD) FRC was significantly higher in the RT compared with BC position [2483 (521) vs 2338 (469) mL, respectively; mean difference, 145; 95% CI, 31 to 404; P = 0.01], while there was no difference between S and BC [2359 (519) mL vs 2338 (469) mL, respectively; mean difference, 21; 95% CI, -93 to 135; P = 0.89].

Conclusion

In awake morbidly obese volunteers, an increase in the FRC is observed when spontaneous ventilation at zero inspiratory pressure is switched to positive pressure. Compared with S positioning, the BC position had no measurable impact on the FRC. The RT position resulted in an optimal FRC.

Trial registration

clinicaltrials.gov (NCT02121808). Registered 24 April 2014.

     

The effects of the reverse trendelenburg position on respiratory mechanics and blood gases in morbidly obese patients during bariatric surgery

Anesthesia adversely affects respiratory function, particularly in morbidly obese patients. Although many studies have been performed to determine the optimal ventilatory settings in these patients, this question has not been answered. The aim of this study was to evaluate the effect of reverse Trendelenburg position (RTP) on gas exchange and respiratory mechanics in 15 obese patients undergoing biliopancreatic diversion. A standardized anesthetic regimen was used and patients were examined at standard times: 1) after tracheal intubation, 2) after laparotomy, 3) after positioning of subcostal retractors, 4) with retractors in RTP. The measurements of respiratory mechanics were repeated for a wide range of tidal volumes by using the technique of rapid occlusion during constant flow inflation. We noted a wide alveolar-arterial oxygen difference [P(A-a)O(2)] in all patients, particularly during Phase 3. When the patients were placed in RTP, P(A-a)O(2) showed a significant improvement and a return toward baseline values. As for mechanics, total respiratory system compliance was significantly higher in RTP than in the other phases. In conclusion, our data suggest that RTP is an appropriate intraoperative posture for obese subjects because it causes minimal arterial blood pressure changes and improves oxygenation.     

呼气末正压通气对腹腔热灌注化疗患者呼吸力学及肺功能的影响

目的探讨不同呼气末正压通气对腹腔热灌注化疗患者呼吸力学及肺功能的影响。方法选择择期行腹膜癌热灌注化疗的患者90例,男55例,女35例,年龄40~70岁,ASAⅠ~Ⅲ级。随机分为三组,每组30例。A组为容量控制通气(VCV)组,VT10 ml/kg;B组为VCV+低PEEP组,VT6ml/kg,PEEP 5cm H_2O;C组为VCV+高PEEP组,VT6ml/kg,PEEP 10cm H_2O;术中调整RR维持PETCO2 35~45 mm Hg。于气管插管后5 min(T_1)、腹腔热灌注化疗开始前(T2)、化疗结束时(T_3)、气管拔管前(T4)记录气道峰压(Ppeak)、气道平台压(Pplat)和平均气道压(Pmean),计算动态肺顺应性(C_(dyn))。并取桡动脉血进行血气分析,计算氧合指数(OI)、呼吸指数(RI)、肺泡-动脉血氧分压差(A-aDO_2)及死腔率(VD/VT)。记录术后7d内肺部相关并发症情况。结果与A组比较,T_1~T_4时B、C组Ppeak、Pplat、A-aDO_2和RI明显降低,OI和VD/VT明显升高(P0.05);T_2~T_4时B、C组Pmean明显降低,Cdyn和PaO_2明显升高(P0.05)。与T_1比较,T_2~T_4时A组Ppeak、Pplat和Pmean明显升高,C_(dyn)明显降低(P0.05);T_3时B组Ppeak和Pplat明显升高(P0.05),T_2~T_4 Pmean明显升高(P0.05),T3、T4时C_(dyn)明显降低(P0.05);T_2~T_4时C组Ppeak、Pplat和Pmean明显升高(P0.05),T_3、T_4时Cdyn明显降低(P0.05)。与T0时比较,T2~T4时三组PaO_2和OI明显降低,A-aDO_2、RI和VD/VT明显升高(P0.05)。术后7d内B、C组肺部感染、低氧血症和肺不张的发生率明显低于A组(P0.05)。结论小潮气量(6ml/kg)联合PEEP(5cm H_2O)通气可以显著改善腹膜癌患者术中热灌注期间肺功能,降低围术期肺部并发症的发生风险。     

Effects of positive end-expiratory pressure on splanchnic circulation and function in experimental peritonitis

Splanchnic and central hemodynamic effects of positive end-expiratory pressure (PEEP) were studied in anesthetized pigs using mechanical ventilatory assistance, with or without sepsis (fecal peritonitis). One hour after sepsis, PEEP (10 cm H2O) was applied (n = 6). Another group (n = 6) had sepsis without PEEP. In one group (n = 6) without sepsis, PEEP was applied after 1 hour, while a fourth group (n = 5), without sepsis or PEEP, served as a control. The group with PEEP and sepsis had reduced cardiac index, portal venous blood flow, and liver surface blood flow. The group with PEEP alone had reduced splanchnic circulation by increasing gastrointestinal vascular resistance, while the group with sepsis alone had increased portal vascular resistance. In a separate series with sepsis, intermittent PEEP, and vigorous fluid resuscitation, it was demonstrated that avoiding hypovolemia did not seem to protect from the PEEP effects on the splanchnic circulation. The combination of sepsis and PEEP was not additive on portal blood flow reduction but reduced bile production.     

个体化呼气末正压对全麻手术患者术后肺功能影响的Meta分析

目的 探索个体化呼气末正压(PEEP)对全麻手术患者术后肺功能的影响。方法 检索PubMed、Cochrane Library、Embase、Web of Science、中国知网、维普、万方数据库,收集个体化PEEP对全麻手术患者术后肺功能影响的随机对照试验(RCT),检索时间为建库至2021年6月。按照Cochrane指导手册进行文献筛选、资料提取和质量评价后,采用RevMan 5.3软件进行Meta分析。结果 共纳入RCT研究17篇,共计患者1 355例,其中个体化PEEP组670例,固定PEEP组685例。与固定PEEP组比较,个体化PEEP组术后肺部并发症发生率明显降低(RR=0.60,95%CI 0.49～0.74,P<0.001),个体化PEEP组术中肺顺应性明显升高(SMD=1.41,95%CI 0.98～1.83,P<0.001),个体化PEEP组术后PaO₂/FiO₂明显升高(SMD=1.02,95%CI 0.61～1.43,P<0.001)。结论 个体化PEEP可提高术中肺顺应性、改善术后氧合,降低全麻...     

Effects of positive end-expiratory pressure on intracranial pressure and compliance in brain-injured patients.

Hypoxic pulmonary disorders and head injuries associated with increased intracranial pressure (ICP) frequently co-exist. Positive end-expiratory pressure (PEEP) improves hypoxemia but has been reported to impede cerebral venous return, potentially causing a further increase in ICP. This study examined the effects of PEEP on ICP at different levels of brain compliance. continuous ICP recordings were obtained after insertion of Scott cannulas to the lateral ventricles of seven comatose patients. Brain compliance was assessed by calculation of the pressure volume index. Patients were maintained in a 30 degrees head-up position. Maintenance of PEEP to levels of 40 cm H2O pressure for as long as 18 hours did not increase ICP in patients with either normal or low intracranial compliance, and did not increase ICP in the absence of pulmonary disease. Central venous pressure and pulmonary artery wedge pressure increased proportionately as PEEP was increased. No consistent changes were found in blood pressure recordings, nor were there any reductions in cardiac output found during the studies. Abrupt discontinuation of PEEP did not result in increased ICP except for a transient rise on two occasions when respiratory secretions became copious and the patients were inadequately ventilated. Improved oxygenation in two patients as a result of PEEP was concomitant with improved intracranial compliance and neurological status. In patients with brain injuries, PEEP improves arterial oxygenation without increasing ICP as previously supposed. Consequently, PEEP is a valuable form of therapy for the comatose patient with pulmonary disorders such as pneumonia or pulmonary edema.     

Trendelenburg体位及气腹对全麻手术患者术后认知功能的影响

目的观察头低臀高截石体位(Trendelenburg体位,简称T位)及气腹对使用丙泊酚全麻手术患者术后认知的影响。方法选择58例行全麻手术的患者,年龄18～65岁,ASAⅠ～Ⅱ级。按照手术体位及是否应用气腹分为T位气腹组和平卧位非气腹组。术中监测BP、HR、SpO_2和BIS值,记录手术时间及丙泊酚总用量。术前1 d和术后第3天记录简易智能精神状态检查量表(MMSE)和脑功能状态测量仪的检查结果。结果 2组患者手术时间、丙泊酚总量差异无统计学意义(P0.05)。2组患者术后第3天的MMSE评分和脑功能状态测量结果与术前比较差异无统计学意义(P0.05),组间比较差异无统计学意义(P0.05)。结论本研究未观察到头低臀高截石体位及气腹对全麻患者术后认知功能的影响。     

More hypotension in patients taking antihypertensives preoperatively during shoulder surgery in the beach chair position

Purpose

Hypotension is common in patients undergoing surgery in the sitting position under general anesthesia, and the risk may be exacerbated by the use of antihypertensive drugs taken preoperatively. The purpose of this study was to compare hypotensive episodes in patients taking antihypertensive medications with normotensive patients during shoulder surgery in the beach chair position.

Methods

Medical records of all patients undergoing shoulder arthroscopy during a 44-month period were reviewed retrospectively. The primary endpoint was the number of moderate hypotensive episodes (systolic blood pressure ≤ 85 mmHg) during the intraoperative period. Secondary endpoints included the frequency of vasopressor administration, total dose of vasopressors, and fluid administered. Values are expressed as mean (standard deviation).

Results

Of 384 patients who underwent shoulder surgery, 185 patients were taking no antihypertensive medication, and 199 were on at least one antihypertensive drug. The antihypertensive medication group had more intraoperative hypotensive episodes [1.7 (2.2) vs 1.2 (1.8); P = 0.01] and vasopressor administrations. Total dose of vasopressors and volume of fluids administered were similar between groups. The timing of the administration of angiotensin-converting enzyme inhibitors and of angiotensin receptor antagonists (≤ 10 hr vs > 10 hr before surgery) had no impact on intraoperative hypotension.

Conclusions

Preoperative use of antihypertensive medication was associated with an increased incidence of intraoperative hypotension. Compared with normotensive patients, patients taking antihypertensive drugs preoperatively are expected to require vasopressors more often to maintain normal blood pressure.