Effects of propofol vs isoflurane on respiratory gas exchange during laparoscopic cholecystectomy

Background : Respiratory function and pulmonary gas exchange are affected in laparoscopic procedures where a pneumoperitoneum is introduced using CO₂. Previous studies have shown differing results concerning pulmonary gas exchange during laparoscopic procedures: Whereas in patients undergoing isoflurane anaesthesia decreases in PaO₂ are demonstrated, this factor remains unchanged in patients undergoing propofol anaesthesia. In the present study, the effects of propofol on pulmonary gas exchange were compared with those of isoflurane in patients undergoing elective laparoscopic cholecystectomy in a prospective randomised manner. Methods : Twenty ASA patients with physical status I and II were divided randomly between isoflurane (IG) and propofol groups (PG). After induction of anaesthesia patients were moderately hyperventilated. Respirator settings remained unchanged during pneumoperitoneum (PP) until 10 min after deflation of the peritoneal cavity. Blood gas analyses were performed at 5 time points: 15 min after induction of anaesthesia (giving pre-PP values), immediately before carbon dioxide insufflation (0 min PP), after both 30 and 60 min of PP and 10 min post PP. Inspiration plateau pressure (P_plat), compliance of the respiratory system, and both ins- and expiratory gas concentrations were continuously recorded by an Ultima V® monitor (Datex Corp., Helsinki, Finland). The difference between arterial and end-tidal CO₂ partial pressure (P(a-et)CO₂) was calculated so as to allow assessment of physiological dead space by the modified Bohr equation. Results : Pulmonary gas exchange differed significantly after 30 min of PP between the IG and the PG. At this time, PaO₂ was 19.5 ± 2.9 kPa (mean ± SD) in the IG and 23.1 ± 1.8 kPa in the PG (P<0.01), whereas PaCO₂ was 5.5 ± 0.37 kPa in the IG and 4.9 ± 0.27 kPa in the PG (P<0.01). These discrepancies remained until after carbon dioxide desufflation. At 10 min post PP, PaO₂ was 18.3 ± 2.6 kPa in the isoflurane group and 21.9 ± 2.2 kPa in the propofol group (P<0.01), whereas PaCO₂ was 5.4 ± 0.46 kPa in the IG and 4.8 ± 0.22 kPa in the PG (P<0.01). During carbon dioxide insufflation the P(a-et)CO₂ increased significantly in the IG from 0.47 ± 0.13 kPa to 0.76 ± 0.37 kPa (P<0.05), while the values in the PG remained constant. Conclusion : This study demonstrates that pulmonary gas exchange in patients with laparoscopic cholecystectomy is affected by the choice of anaesthetic procedure. During and after laparoscopic cholecystectomy using isoflurane as the anaesthetic, the PaCO₂ is significantly higher and the PaO₂ significantly lower than they are with propofol.     

妇科腹腔镜手术中Trendelenburg体位时脑血流动力学的变化

目的应用经颅多普勒超声监测Trendelenburg体位(简称T位)时脑血流动力学的变化。方法择期腹腔镜下妇科手术患者40例,常规全身麻醉后行颈内静脉球部置管,监测麻醉诱导前(T1)、麻醉诱导后(T2)、气腹后(T3)、T位即刻(T4)、T位后30min(T5)、体位恢复后(T6)大脑中动脉平均血流速度(Vm)、搏动指数(PI)、阻力指数(RI),计算脑灌注压(CPP)。同时测量颈内静脉压,并于T2、T5采颈内静脉球部、桡动脉血进行血气分析。计算动-颈内静脉氧分压差(Da-jvO2)、二氧化碳分压差(Da-jvCO2)、血乳酸浓度差(Da-jvLac)和血糖浓度差(Da-jvGlu)。结果与T1时比较,T2时患者Vm、CPP明显降低(P0.05);与T2时比较,T4~T6时Vm明显升高(P0.05),T4、T5时PI、CVP和T5时RI、CPP明显升高(P0.05);T5时Da-jvO2明显降低(P0.05),Da-jvCO2、SjvO2明显升高(P0.05)。结论 Trendelenburg体位30min存在大脑过度灌注和脑氧摄取量减少,但未造成明显脑组织代谢障碍。     

不同通气模式对腹腔镜下Trendelenburg体位患者肺通气的影响

目的 采用电阻抗断层成像(EIT)技术观察容量控制通气(VCV)和压力控制容量保证通气(PCV-VG)模式对腹腔镜下Trendelenburg体位患者全麻术中肺通气的影响。方法 择期全麻下行腹腔镜下Trendelenburg体位妇科手术患者60例,年龄40～65岁,BMI 18～30 kg/m²,ASA Ⅰ或Ⅱ级,采用随机数字表法将患者分为两组：VCV模式组（V组）和PCV-VG模式组（P组）,每组30例。V组术中采用VCV模式,P组采用PCV-VG模式。记录入室后(T0)、插管后5 min(T1)、更改体位（由平卧位更改为Trendelenburg体位）后即刻(T2)、更改体位后30 min(T3)、更改体位后60 min(T4)、更改体位后120 min(T5)、改平卧位(T6)时的MAP、HR、通气中心(CoV)、依赖静止区(DSS)、非依赖静止区(NSS)的面积百分比。记录T1、T3—T5时气道峰压（Ppeak）、pH、PaO₂、PaCO₂、氧合指数（OI）。记录术后7 d内肺部感染、呼吸衰竭等肺部并发症发生情况。结果 T0—T6时两组MAP、HR差异无统计学意义。与V组比较,T3—T6时CoV面积百分比明显升高,DSS面积百分比明显降低（P<0.05）,T3—T5时Ppeak明显降低（P<0.05）,T4、T5时PaO₂、OI明显升高（P<0.05）。两组术后7 d内均无肺部并发症。结论 PCV-VG通气模式可明显改善腹腔镜下Trendelenburg体位患者术中肺通气及肺氧合功能。     

短时俯卧位机械通气对急性肺损伤病人呼吸功能及血液动力学的影响

目的观察短时闯俯卧位机械通气对急性肺损伤病人功能残气量(FRC)、气体交换功能及血液动力学的影响。方法选择机械通气治疗的急性肺损伤病人8例,分别于仰卧位和俯卧位后30min行动脉血气分析,随即采用密闭式氦稀释法测定FRC,持续监测动态胸肺顺应性(Cst)以及血液动力学变化。结果与仰卧位相比,俯卧位后30min病人FRC从(1.4±0.4)L上升至(1.5±0.3)L(P<0.05),动脉血氧分压(PaO2)从(120±28)mmHg增加至(140±24)mmHg(P<0.01),同时肺泡动脉氧分压差减小,氧合指数上升(P<0.05),Csr差异无统计学意义。平均动脉压、中心静脉压、心率等血液动力学指标差异无统计学意义。PaO2与FRC间的相关系数r=0.709(P<0.05)。结论短时间俯卧位可以增加急性肺损伤病人FRC,改善氧合状况,且对血液动力学无明显影响。     

The effect of the Trendelenburg position on lower oesophageal sphincter tone

Measurements were made of gastric, lower oesophageal and barrier pressures in the supine, moderate and steep Trendelenburg positions in 10 healthy female patients during balanced anaesthesia. Adoption of the Trendelenburg position resulted in no significant changes in any measurement, with the exception of a small increase (0.1 kPa) in intragastric pressure in the steep head-down position. We conclude that the steep Trendelenburg position should not predispose to regurgitation in healthy patients.     

Large tidal volume ventilation improves pulmonary gas exchange during lower abdominal surgery in Trendelenburg’s position

Impaired pulmonary gas exchange is a common complication of general anaesthesia. Periodic hyperinflation of the lungs and large tidal volume ventilation were the first preventive measures to be widely embraced, but their effectiveness in clinical practice has never been clearly established by controlled clinical studies. To assess their effects in high-risk patients we studied 24 adults having lower abdominal gynaecological surgery in the Trendelenburg (head down) position. Pulmonary oxygen exchange was determined during four steady-states: awake control (AC), after 30 min of conventional tidal volume (CVT, 7.5 ml.kg-1) or high tidal volume (HVT, 12.7 ml.kg-1) ventilation, introduced in random order, and five minutes after manual hyperinflations (HI) of the lungs. The patients' lungs were ventilated with air/O2 by an Ohmeda volume-controlled ventilator via a circle system. The FIO2 was controlled at 0.5, and FETCO2 was controlled by adding dead space during HVT. Arterial blood gas analysis was used to calculate the oxygen tension-based indices of gas exchange. There was significant deterioration of (A-a)DO2 at 30 min in Group A, whose lungs were first ventilated with CVT (81.6 +/- 7.2 to 166.8 +/- 13.7 mmHg, P less than 0.001); but not in Group B, whose lungs were first ventilated with HVT (77.0 +/- 9.9 to 104.4 +/- 16.8 mmHg). When Group A and B data were pooled there was no difference between randomized CVT and HVT, but improvement occurred after HI. In this model of compromised O2 exchange large inflation volumes (HVT and HI) were of considerable clinical benefit, HVT prevented and HI reversed the gas exchange disorder.     

Intratracheal pulmonary ventilation improves gas exchange during laparoscopy in a pediatric lung injury model

Background/Purpose

This study was aimed at determining whether intraoperative intratracheal pulmonary ventilation (ITPV) could prevent/treat respiratory complications of laparoscopy in a model of pediatric pulmonary insufficiency.

Methods

Severe lung injury was induced in 0- to 2-month-old lambs (n = 5) by endotracheal saline lavage. Animals then underwent establishment of CO₂ pneumoperitoneum. Intraperitoneal pressures were progressively raised from 0 to 15 mm Hg, at intervals of 5 mm Hg. At each interval, blood gas and hemodynamic data were recorded, 20 minutes after initiation of both conventional ventilation and pure ITPV. All ventilatory parameters were constant and identical on both modes of ventilation.

Results

On conventional ventilation, severe respiratory acidosis and hypoxemia ensued at intraperitoneal pressures of 5 mm Hg and 10 mm Hg or more, respectively. Compared with conventional ventilation, ITPV led to statistically significant decreases in Pco₂ at intraperitoneal pressures of 5 mm Hg (43.2 ± 5.2 vs 56.1 ± 6.6 mm Hg) and 10 mm Hg (45.1 ± 3.2 vs 61 ± 6.3 mm Hg) and to significant increases in Po₂ at 10 mm Hg (92 ± 10.2 vs 61 ± 8.1 mm Hg), resolving the acidosis and hypoxemia at those pressure levels.

Conclusions

Compared with conventional ventilation, ITPV improves both CO₂ removal and oxygenation during CO₂ pneumoperitoneum in a pediatric lung injury model. Intratracheal pulmonary ventilation may be a safer intraoperative mode of ventilation for neonates and children with respiratory failure who require laparoscopy.     

Comparison of volume-controlled and pressure-controlled ventilation in steep Trendelenburg position for robot-assisted laparoscopic radical prostatectomy

Study Objective

To compare the effects of volume-controlled ventilation (VCV) and pressure-controlled ventilation (PCV) on respiratory mechanics and hemodynamics in steep Trendelenburg position.

Design

Prospective, randomized clinical trial.

Setting

University hospital.

Patients

34 ASA physical status 1 and 2 patients undergoing RLRP.

Interventions

Patients were randomly allocated to either the VCV (n = 17) or the PCV group (n = 17). After induction of anesthesia, each patient's lungs were ventilated in constant-flow VCV mode with 50% O₂ and tidal volume of 8 mL/kg; a pulmonary artery catheter was then inserted. After establishment of 30° Trendelenburg position and pneumoperitoneum, VCV mode was switched to PCV mode in the PCV group.

Measurements

Respiratory and hemodynamic variables were measured at baseline supine position (T1), post-Trendelenburg and pneumoperitoneum 60 minutes (T2) and 120 minutes (T3), and return to baseline after skin closure (T4).

Main Results

The PCV group had lower peak airway pressure (AP_peak) and greater dynamic compliance (C_dyn) than the VCV group at T2 and T3 (P < 0.05). However, no other variables differed between the groups. Pulmonary arterial pressure and central venous pressure increased at T2 and T3 (P < 0.05). Cardiac output and right ventricular ejection fraction were unchanged in both groups.

Conclusions

PCV offered greater C_dyn and lower AP_peak than VCV, but no advantages over VCV in respiratory mechanics or hemodynamics.     

Lung aeration and pulmonary gas exchange during lumbar epidural anaesthesia and in the lithotomy position in elderly patients

We investigated a total of 36 subjects with a mean (SD) age of 65 (13) years, during baseline conditions (supine, before any anaesthesia), and then during one of the following protocols: (1) lithotomy positioning ( n  = 12), (2) epidural anaesthesia ( n  = 12), (3) general anaesthesia in the supine position ( n  = 12). Lung aeration, ventilation/perfusion matching, gas exchange and functional residual capacity were measured. Lung aeration was normal during baseline assessment with almost no regions with poor aeration and no substantial dependent densities. Shunt and perfusion of poorly ventilated regions were minor. Lithotomy positioning did not reduce functional residual capacity and did not affect aeration of the lung or ventilation/perfusion matching. Epidural anaesthesia, in general, had no effect on aeration, ventilation/perfusion matching or gas exchange, regardless of whether the patient was in the supine or lithotomy position. General anaesthesia, however, caused significant increases in poorly aerated lung regions and in dependent densities (interpreted as atelectasis). In conclusion, no or little impairment of lung aeration and ventilation/perfusion matching was caused by the lithotomy position and/or epidural anaesthesia, contrary to the effects seen during general anaesthesia. However, our findings also suggest that being overweight is a factor that may cause impairment of lung aeration.     

Effect of the degree of reverse Trendelenburg position on intraocular pressure during prone spine surgery: a randomized controlled trial

Background contextPostoperative vision loss complicates an estimated 1 in 1,100 prone spine surgical cases. This complication has been attributed to ischemic optic neuropathy, with one proposed reason being perioperative elevations in intraocular pressure (IOP). Previous research has studied the effects of table inclination on IOP in awake volunteers; however, the effects in spine surgery patients have not been investigated for reverse Trendelenburg positioning using a prospective, randomized controlled study design.PurposeTo assess the effect of table inclination on IOP in patients undergoing prone spine surgery.Study designSingle-center, prospective randomized controlled study.Patient sampleNineteen patients with no history of eye pathology, undergoing prone spine surgery at Dwight D. Eisenhower Army Medical Center, were randomly assigned to a table position: neutral, 5°, or 10° of reverse Trendelenburg.Outcome measuresIntraocular pressure, mean arterial pressure (MAP), estimated blood loss, fluid resuscitation, and ophthalmologic complication were assessed before and after induction and at incremental times during surgery, beginning at 30 minutes, 60 minutes, and 60-minute increments thereafter.MethodsMultivariate analyses evaluated surgical time, IOP, MAP, estimated blood loss, and fluid resuscitation as a function of table inclination to determine the effect of patient positioning on identified risk factors for postoperative vision loss.ResultsSurgical times ranged from 33 to 325 minutes. A rapid increase in IOP was noted after prone positioning, with continued increases as time elapsed. The neutral group exhibited statistically higher IOP compared with the 5° reverse Trendelenburg group after 60 minutes and the 10° group through 60 minutes of surgery. The trend continued through 120 minutes; however, because of a lack of power, we were unable to determine the statistical significance. There were no statistically significant differences between the 5° and 10° reverse Trendelenburg groups.ConclusionsReverse Trendelenburg positioning elicits decreased IOP compared with prone positioning for surgery times less than 120 minutes. Ten degrees of reverse Trendelenburg attenuate the rise in IOP during prone spine surgery superiorly in comparison with 5°. No significant complications were associated with reverse Trendelenburg positioning.     

长时间CO2气腹和Trendelenburg体位对中老年患者直肠癌根治术中脑氧饱和度的影响

目的评估腹腔镜下直肠癌根治术中长时间CO2气腹和Trendelenburg体位对中老年患者脑氧饱和度(rSO2)的影响。方法选择拟行腹腔镜下直肠癌根治术患者38例,男19例,女19例,年龄45~80岁,BMI 18~25kg/m2,ASAⅠ或Ⅱ级。根据年龄分为两组:45~64岁为中年组(M组),65~80岁为老年组(O组)。两组均常规全麻插管,记录诱导结束后10 min(T0)、Trendelenburg体位后30 min(T1)、1 h(T2)和2 h(T3)的HR、MAP、PETCO2、PaCO2、PaO2、rSO2等。采用Pearson检验分析rSO2与年龄的相关性。记录术后3 d内急性脑卒中和术后谵妄(POD)等神经系统相关不良反应的发生情况。结果与T0时比较,T1-T3时两组rSO2均明显升高(P<0.05)。T0时M组rSO2明显高于O组(P<0.05)。不同时点两组HR、MAP、PETCO2、PaCO2、PaO2差异无统计学意义。T0时rSO2与年龄呈明显负相关(r=-0.650,P<0.05)。T1、T2时rSO2与年龄未见明显相关性。T3时rSO2和年龄之间呈明显正相关(r=0.488,P<0.05)。两组术后无一例急性脑卒中和POD等神经系统相关不良反应发生。结论在需要Trendelenburg体位的腹腔镜手术中,尤其对于老年患者,应该加强rSO2监测,避免脑氧供氧需失衡带来的神经系统并发症。     

乌司他丁预先给药对下肢手术患者松止血带后肺换气功能的影响

目的 评价乌司他丁预先给药对下肢手术患者松止血带后肺换气功能的影响.方法 择期单侧下肢手术患者(需要止血带)27例,年龄25～64岁,体重指数18～28 kG/m~2,,ASA Ⅰ或Ⅱ级,止血带充气时间1.0～1.5 h.随机分为2组:对照组(C组,n=15)和乌司他丁预先给药组(U组,n=12).于L_(2,3),或L_(3,4).间隙行脊椎一硬膜外联合阻滞.U组静脉输注乌司他丁6 000 U/kg(溶于100 ml生理盐水,10 mi/min),C组以等量生理盐水替代,均于10 min后扎止血带.于扎止血带前即刻(T_0)、扎止血带60 rain(T_1)、松止血带后30 rain(T_2)、2 h(T_3)、6 h(T_4)和24 h(T_5)时采集桡动脉血样行血气分析,测定血浆丙二醛(MDA)、血清白细胞介素6(IL-6)和IL-8的浓度.结果 与T_0时比较,C组T_4时动脉血氧分压降低,肺泡-动脉血氧分压差和呼吸指数升高,T_(2～5)时血浆MDA浓度升高,T_(3～5)时血清IL-6和IL-8浓度升高,U组T_(3,4)时血清IL6和IL-8浓度升高(P<0.05或0.01),各时点血气指标比较差异无统计学意义(P>0.05).与C组比较,U组动脉血氧分压升高,肺泡-动脉血氧分压差、呼吸指数、血浆MDA浓度、血清IL-6和IL-8的浓度降低(P<0.05或0.01).结论 乌司他丁预先给药(6 000 U/kg)可有效改善下肢手术患者松止血带后肺换气功能,其机制可能与抑制氧自由基脂质过氧化反应和全身炎性反应有关.     

Effect of the lithotomy position on spinal anesthesia with hyperbaric tetracaine

This study was performed to determine the effects of lithotomy position on the spread of analgesia and hemodynamics following spinal anesthesia with 0.5% hyperbaric tetracaine. Thirty patients who underwent hysterectomy due to myoma uteri were studied. All patients received spinal anesthesia in the left lateral decubitus position and were turned supine immediately after intrathecal administration of the drug. Fifteen patients were then placed in the horizontal lithotomy position within 10 s, and the remaining 15 were kept in the horizontal supine position for 30 min. There were no significant differences between the groups in mean arterial pressure, heart rate, cardiac output, and in the cephalad spread of analgesia. The lithotomy position had no effect on the spread of analgesia or anesthetic course of spinal anesthesia with hyperbaric tetracaine.     

Effects of isoflurane on oxygenation during one-lung ventilation in pulmonary emphysema patients

Background: Hypoxic pulmonary vasoconstriction has an important role in human one-lung ventilation (OLV) in the lateral decubitus position under general anesthesia. During OLV, inhalational anesthesia may inhibit hypoxic pulmonary vasoconstriction and the decrease in arterial oxygenation. We studied the effect of isoflurane administration on arterial oxygen tension in chronic obstructive pulmonary disease patients.
Methods: Ten patients who had thoracoscopic laser ablation of bullous emphysema were studied. Patients received 2% isoflurane in oxygen from induction until the first 20 min of OLV in the lateral decubitus position, then were switched to 1% isoflurane lasting 20 min and next were switched to 0.5% isoflurane lasting 20 min. After each 20-min inhalation, pulmonary and hemodynamic parameters were measured. The given concentrations for isoflurane were merely vapor meter concentrations.
Results: PaO₂/FIO₂, Qs/Qt respiratory rate peak inspiratory pressure and PaCO₂ showed no significant changes at each point of isoflurane. Expiratory tidal volume significantly decreased (P<0.05) with 0.5% isoflurane compared to that with 2% isoflurane. Cardiac output, mean arterial pressure, mean pulmonary arterial pressure, systemic vascular resistance and pulmonary vascular resistance showed no significant changes at each point of isoflurane.
Conclusions: In patients with pulmonary emphysema, arterial oxygenation is not affected by low isoflurane concentration during OLV in the lateral decubitus position.     

Hemodynamics during laparoscopy in the supine or prone position

During laparoscopy elevations in arterial pressure and a decrease in cardiac output have been reported. Laparoscopic surgery performed in the prone position may be advantageous for some surgical procedures, but the hemodynamic effects of pneumoperitoneum in this position have not been studied. We studied the effects of different levels of increased intraabdominal pressure on hemodynamics and oxygen transport in eight pigs in the prone and the supine position. Increases in intraabdominal pressure did not result in decreased cardiac output or in a reduction of oxygen transport and consumption in either position. These results suggest that laparoscopy in the prone position does not result in more severe hemodynamic depression than laparoscopy in the supine position.     

The effect of acetazolamide on intra‐ocular pressure after Trendelenburg positioning – a randomised double‐blind crossover trial in volunteers

Recent evidence suggests Trendelenburg positioning can produce a significant rise in intra‐ocular pressure. Peri‐operative vision loss in patients undergoing laparoscopic colorectal surgery has been reported with the rise in intra‐ocular pressure suggested as a possible factor. Acetazolamide decreases intra‐ocular pressure by reducing the formation of aqueous humour, so we aimed to investigate if it could attenuate the intra‐ocular pressure rise that can occur in the Trendelenburg position. Nine healthy volunteers were recruited and randomly assigned to a double‐blind crossover comparison of placebo or acetazolamide with a minimal 4 days’ washout period before the second study day. One and a half hours after taking the medication, volunteers lay head‐down at 17° for 4 h. Intraocular pressure measurements were repeated in both eyes every 30 min over a 4‐h period. There were two males and seven female volunteers, with a mean (SD) age of 54.3 (18.5) years. The mean (SD) increase in intra‐ocular pressure following 4 h in the Trendelenburg position was 3.17 (4.63) mmHg after the placebo, and 0.02 (4.01) mmHg (p = 0.02) after acetazolamide. We have shown than acetazolamide can attenuate the rise that occurs in intra‐ocular pressure when in the Trendelenburg position.