硬膜外麻醉下不同二氧化碳气腹压在腹腔镜胆囊切除手术中应用的前瞻性随机对照研究

目的通过评价硬膜外麻醉下腹腔镜胆囊切除术（laparoscopic cholecystectomy，LC）中不同二氧化碳（CO2）气腹压对患者生命体征、血气指标及术后恢复的影响，探讨LC术更经济、安全、微创的治疗条件。方法采用前瞻性随机对照研究方法，60例择期LC术分为低、中、高气腹压三组，气腹压力A组8mmHg，B组11mmHg，C组14mmHg。对比术前术中生命体征、血气指标及术后恢复等指标。结果60例LC术在硬膜外麻醉下均顺利完成。气腹后3组血压（BP）均明显下降（P〈0．001），C组明显低于A、B组（P〈0．05）。气腹后3组心率（HR）均减慢（P〈0．001），3组间差异无显著性（P〉0．05）。气腹后3组呼吸频率（RF）均显著增快（P〈0．001），C组增加较A、B组明显（P〈0．05）。气腹后3组动脉血CO2分压（PaCO2）均明显增高（P〈0．05），B、C组明显高于A组（P〈0．05）。气腹后3组pH值均明显降低（P〈0．01），C组明显低于A组（P〈0．05）。气腹后3组血浆CO2含量（TCO2）、碳酸氢根（HCO3^-）明显增高（P〈0．05），3组间差异无显著性（P〉0．05）。3组手术时间、术中CO2消耗量、术后肩痛和恶心呕吐发生率差异无显著性（P〉0．05）。结论硬膜外麻醉、低气腹压（8mmHg）完全能够满足绝大部分LC手术需要，而且可以达到更安全、经济、微创的目的。     

不同压力CO2气腹对腹腔镜胆囊切除术后肩部疼痛发病影响的临床观察

目的研究腹腔镜胆囊切除术 (laparoscopiccholecystectomy ,LC)后肩部疼痛发生的原因、机理及防治方法。方法将 12 0例行LC的患者随机分为A、B、C组 ,每组 4 0例。气腹压力设定A组 10mmHg ,B组 12mmHg ,C组 14mmHg。观察 3组术前、术后的PaO2 、PaCO2 、动脉血 pH值以及术后 1、3、6、12、2 4、4 8、72、96h肩痛的发生率和疼痛程度 (视觉模拟评分 VAS)。结果术中CO2 用量C组较A组多 ,差异有显著意义 (F =11 38,P <0 0 5 )。C组术前、术后的PaO2 差值与A、B组术前、术后PaO2 差值相比较大 ,且差异有显著意义 (F =6 92 ,P <0 0 1)。随 3组气腹压力的增高 ,术后 3、12、2 4、4 8h肩痛发生率有增高趋势 (χ2 值分别为 2 36 6 ,2 32 4 ,2 72 9,2 340 ,P <0 0 5 ) ;其VAS评分也明显上升 (F =19 5 3,P <0 0 1)。结论LC术后肩痛的主要原因可能与人工气腹张力对膈肌的牵拉有关。在 10mmHg低压气腹下行LC ,可显著降低LC术后肩痛的发生率及疼痛程度。     

人工气腹前腹腔灌洗对腹腔镜胆囊切除术后肩痛的疗效分析

目的比较腹腔充入CO₂气体建立人工气腹前、后不同时间段进行腹腔灌洗,对腹腔镜胆囊切除术（LC）术后肩痛的疗效。 方法选择2016年3月至2018年6月南方医科大学附属小榄医院诊治的LC患者120例,按照数字表法随机分为A、B、C组,每组40例。A组为对照组,术后尽量吸尽膈下气体关腹,不进行腹腔灌洗;B组术后用温生理盐水（37.5℃的0.9%氯化钠溶液）进行腹腔灌洗;C组为充入CO₂气腹前先进行膈下温生理盐水灌洗,术后再次行腹腔灌洗。比较3组患者术后6、12、24、48 h的术后肩痛评分（VAS）和中、重度肩痛发生率。 结果3组患者在术后48 h不同时间点的肩痛VAS评分比较及两两比较,差异均有统计学意义（P<0.05）,其中C组的肩痛程度最轻。A、B、C组患者中、重度肩痛发生率分别为27.5%（11/40）、7.5%（3/40）、2.5%（1/40）,整体比较差异有统计学意义（χ²=12.708,P=0.002）,其中A组发生率显著高于B组和C组（χ²=4.242、7.941,P=0.039、0.005）,而B、C两组发生率差异无统计学意义（χ²=0.263,P=0.608）。 结论温生理盐水灌洗腹腔可明显降低LC术后疼痛的发生率和减轻术后肩痛的强度,其中人工气腹前灌洗温生理盐水的患者术后发生肩痛程度最轻。     

不同气腹压力对腹腔镜胆囊切除术后短期并发症的影响

目的：探讨不同CO2 气腹压力对腹腔镜胆囊切除（LC）术后肝功能、动脉血气及对颈肩部疼痛的 影响。 方法：选择行择期LC 术患者120 例,随机分为A,B,C 3 组,每组40 例。A 组气腹压力设置为 10 mmHg（1 mmHg=0.133 kPa）,B 组为12 mmHg,C 组为14 mmHg。对比分析3 组手术前后 肝功能、血气指标及术后1~3 d 恶心呕吐、颈肩部疼痛的发生率。 结果：术前3 组间各参数比较差异无统计学意义（均P>0.05）,但术后3 组间肝功能、血气指标 改变及恶心呕吐、颈肩部疼痛的发生率均有明显差异（均P<0.05）。结果显示,气腹压力越大, 术后肝功能（AST,ALT,TBIL 升高）和血气指标（PCO2 升高,pH,PO2 下降）变化越明显,且 术后颈、肩痛及恶心呕吐发生率越高。 结论：气腹压力对LC 术后肝功能,动脉血气,颈,肩痛及恶心呕吐有明显影响,故术中应尽量降 低气腹压力。     

内镜垂体瘤切除术中鞍膈形态与肿瘤残余及并发症的关系

目的：探讨经鼻内镜垂体瘤切除术中鞍膈下降形态与肿瘤残余、尿崩症及术中脑脊液漏的关系。方法回顾分析2012年2月～2013年3月我科80例鼻内镜垂体瘤切除术的临床资料。术中肿瘤切除后鞍膈下降形态分为4型：A型：鞍膈以垂体柄为中心对称性降至鞍区;B型：鞍膈非对称性降至鞍区,垂体柄偏向一侧;C型：鞍膈对称性下降,垂体柄移至鞍背;D型：鞍膈未或仅有轻微下降,垂体柄位置模糊不清。结果 A、B、C、D四型鞍膈的肿瘤残余率、尿崩症发生率及脑脊液漏发生率有统计学差异（χ2＝11．069,P＝0．011;χ2＝11．483,P＝0．009;χ2＝8．890,P＝0．031）。肿瘤残余多见于B、D型鞍膈,肿瘤残余发生率与A、C型鞍膈有统计学差异（Z＝-2．409,P＝0．016;Z＝-2．062,P＝0．039;Z＝-2．477,P＝0．013;Z＝-2．245,P＝0．025）,但B型与D型肿瘤残余率无统计学差异（Z＝-0．791,P＝0．429）。尿崩症、术中脑脊液漏多见于A、C型鞍膈,发生率与B、D型鞍膈有统计学差异（P＜0．05）,但A型与C型尿崩症、脑脊液漏发生率无统计学差异（Z＝-0．195, P＝0.846;Z＝-0．362,P＝0．717）。结论鞍膈下降形态可以作为肿瘤残余、尿崩症及术中脑脊液漏的一个解剖参考。     

腹腔镜胆囊切除术不同压力CO2气腹对气腹存留时限及肩部疼痛的影响

目的 探讨腹腔镜胆囊切除术(laparoscopic cholecystectomy,LC)不同压力CO2气腹对气腹存留时限及肩部疼痛的影响,探讨LC术后气腹存留时限的影响因素及肩部疼痛的原因.方法 2002年4～10月连续观察69例LC,随机分为A、B、C 3组,每组23例.气腹压力设定A组10mm Hg,B组12mm Hg,C组14mm Hg.对69例LC术后进行连续胸部X线平片观察膈下游离气体,测量术后24h两侧膈下游离气体的长、高并计算残气量.采用视觉模拟评分(vision analogue score,VAS)观察3组术后1、3、6、12、24、48、72、96、120h肩部疼痛程度.结果 LC后气腹存留时限为(1.8±1.1)d,男女组气腹存留时限分别为(1.8±1.1)d和(1.7±1.0)d,2组比较无显著意义(H=0.013,P=0.911).3组术后24h膈下残气量及术后气腹存留时限差异无显著性(P＞0.05).逐步回归分析示lg(气腹存留时限)与术后24h膈下残气量呈正相关(r=0.616,P=0.006),与气腹时间呈负相关(r=-0.228,P=0.014),与年龄、体重、身高、手术时间及所用气体量无相关性.术后26例出现肩部疼痛,随着A、B、C 3组气腹压力的增高,发生肩部疼痛患者的VAS评分明显增高(F=9.635, P=0.000),术后24h肩部疼痛VAS评分与术后24 h右侧膈下残气量呈正相关(r=0.333,P=0.005),与气腹存留时限呈正相关(r=0.296,P=0.014).结论 LC术毕尽量将腹腔内CO2气体排净可缩短术后残气吸收时间.不同压力CO2气腹对LC术后残余的CO2气体量及气腹存留时限无明显影响.LC后肩部疼痛程度随气腹压增高有明显加重趋势,人工气腹引起膈肌的张力可能是造成肩部疼痛的重要原因.     

Centerpiece单开门椎板成形术和椎板切除融合术治疗多节段颈脊髓病的临床疗效对比分析

目的：比较多节段颈脊髓病2种后路手术方式的临床疗效。方法回顾分析80例因多节段颈脊髓病行椎板成形术（A组）和椎板切除融合术（B组）的患者的资料,对2组患者术前、术后及随访时影像学资料和临床评价指标进行比较。结果术后1周2组日本骨科学会（ Japanese Orthopaedic Association , JOA）评分平均改善率差异无统计学意义（P＞0．05）,A组疼痛视觉模拟量表（visual analogue scale, VAS）评分、颈椎曲度与术前相比差异无统计学（P＜0．05）,B组则显著改善（P＜0．05）。术后1年B组JOA评分较术后1周显著降低（P＜0．05）,B组与术前颈椎活动度的差值显著大于A组（P＜0．01）。随访期间,A组C5神经麻痹的发生率为2．8％（1/36）,B组为12．5％（3/24）,差异有统计学意义（χ2＝3．35,P＜0．05）。结论2种方法早期都可取得良好的神经功能改善,在颈椎曲度、颈痛和活动度的影响上,两者各有优劣。     

CO2气腹对ACTH、COR、PGE2分泌的影响及与肩部疼痛的关系

目的 研究不同压力下CO2气腹腹腔镜胆囊切除术(LC)对机体促肾上腺皮质激素(ACTH)、皮质醇(COR)、前列腺素E(PGE2)对肩部疼痛的影响及其之间的关系.方法 将90例行LC的患者随机分为A、B、C 3组,每组30例.气腹压力:A组10 mm Hg,B组12 mm Hg,C组14 mm Hg.放射免疫法测定患者术前、术终、术后血浆ACTH及COR、PGE2浓度,采用视觉模拟评分法(VAS)测定术后1、3、6、12、24、48、72、96、120 h肩部疼痛的程度.并对数据进行相应的卡方检验、方差分析、t检验、相关分析及多元逐步回归分析.结果 ①3组肩部疼痛VAS随气腹压力降低而减轻,差异有统计学意义(F=16.12,P＜0.01).②与术前比较,术终、术后6 h 3组ACTH、COR、PGE2均有明显升高,并随气腹压力升高而升高,术终时最高,随时间延长逐渐降低,至术后1 d,3组ACTH均恢复至术前水平,而C组COR仍明显高于术前水平(t=3.19,P＜0.01),A、B、C 3组PGE2均明显高于术前水平(t值分别为3.31,6.75,7.51,均P＜0.01).组间比较,术终PGE2在C组明显高于A组(t=2.15,P＜0.05);术后6 h,C组ACTH、COR、PGE2均明显高于A组;术后1 d,COR、PGE2C组明显高于A组(t值分别为2.94,2.08;P＜0.01,P＜0.05).③术后24 h肩部疼痛VAS与术后1 d PGE2呈正相关(r=0.47,P＜0.01),与术后6 h COR正相关(r=0.40,P＜0.01).结论 不同压力下CO2气腹LC后,都引起明显的神经内分泌激素反应,降低气腹压力可减轻LC手术后肩部疼痛,减少ACTH、COR、PGE2释放.     

腹腔镜胆囊切除术后肩部疼痛的预防措施研究

目的对比预防腹腔镜胆囊切除术(laparoscopic cholecystectomy,LC)后肩部疼痛发生的不同措施的效果。方法将90例患者平均分为A、B、C三组,A组为对照组,B组延长术后吸氧时间4 h,C组术中膈下温热生理盐水冲洗。进行术后观察,统计其术后肩部疼痛的发生率,并采用视觉模拟法评测其疼痛程度,并抽血行血气分析。结果术后48 h,B组和C组肩痛发生率明显低于A组,其中C组肩痛发生率最低。同时B组和C组的疼痛程度也较A组有显著降低,且C组患者的疼痛时间有明显缩短。术中、术后6 h B、C组的Pa Co2、Pa O2和术后6 h p H值均显著优于A组(P0.05)。结论相比于术后延长吸氧时间,温热生理盐水冲洗法的作用效果更佳明显,对术后肩部疼痛的预防更为有效。     

大肠癌术前动脉灌注化疗与术后经门静脉插管化疗的对比研究

目的 比较大肠癌不同化疗方案的临床疗效。方法 71例大肠癌患者随机分为3组：（1）A组,术前动脉灌注化疗;（2）B组,术后门静脉化疗;（3）C组（对照组）,仅行经典根治性手术。结果 术后3年生存率A,B两组分别为75．0％,73．1％（P＞0．05）,但A,B组与C组（44．0％）比较,差异均有显著性（P＜0．05）。结论 有条件的情况下,在术前、中、后采用有效的局部化疗措施,有助于提高病人的长期生存率。     

腹腔镜胆囊切除术不同气腹持续时间对术后肩痛的影响

目的:探讨腹腔镜胆囊手术不同气腹持续时间对术后肩痛的影响。方法:于全身麻醉下为91例患者行腹腔镜胆囊切除术,气腹压力为12mm Hg,根据气腹时间分为3组,A组<1h;B组1~2h;C组>2h。记录术后清醒、拔管时间及术后3d内的肩痛情况,并让患者于术后12h、24h、48h、72h肩痛用视觉模拟评分法(visual analogue scale system,VAS)评分。结果:术后出现肩痛A组12例,B组10例,C组8例,差异无统计学意义(P>0.05)。3组患者肩痛VAS评分差异无统计学意义。结论:不同气腹时间对术后肩痛的发生率和疼痛程度无影响。     

Double-blind, prospective, randomized study of warmed, humidified carbon dioxide insufflation vs standard carbon dioxide for patients undergoing laparoscopic cholecystectomy

HYPOTHESIS: Patients undergoing warmed, humidified carbon dioxide (CO2) insufflation for laparoscopic cholecystectomy will (1) maintain a warmer intraoperative core temperature, (2) have their surgeon experience less fogging of the camera lens, and (3) have less postoperative pain than patients undergoing laparoscopic cholecystectomy with standard CO2 insufflation. DESIGN: A double-blind, prospective, randomized study comparing patients undergoing laparoscopic cholecystectomy with standard CO2 insufflation vs those receiving warmed, humidified CO2 (Insuflow Filter Heater Hydrator; Lexion Medical, St Paul, Minn) was performed. Main variables included patient core temperature, postoperative pain, analgesic requirements, and camera lens fogging. RESULTS: One hundred one blinded patients (69 women, 32 men) undergoing laparoscopic cholecystectomy were randomized into 2 groups-52 receiving standard CO2 insufflation (group A) and 49 receiving warmed, humidified CO2 (group B). Mean patient intraoperative core temperature change (group A decreased by 0.03 degrees C, group B increased by 0.29 degrees C, P =.01) and mean abdominal pain (Likert scale, 0-10) at 14 days postoperatively (group A, 1.0; group B, 0.3; P =.02) were different. Other variables (camera lens fogging, early postoperative pain, narcotic requirements, recovery room stay, and return to normal activities) between groups were similar. CONCLUSION: While patients undergoing laparoscopic cholecystectomy with warmed, humidified CO2 had several advantages that were statistically significant, no major clinically relevant differences between groups A and B were evident.     

Maintenance of subcutaneous cavities with CO2

Since mechanical retractors in endoscopic plastic surgery cause certain drawbacks, we developed a model in dogs, which, by insufflating CO2 into a subcutaneous cavity, we were able to maintain. We evaluated the magnitude of subcutaneous emphysema and absorption of CO2 by insufflating different pressures and the efficacy of external pressure on the skin with the purpose of limiting the subcutaneous emphysema. Sixteen dogs were divided in 3 groups, A, B, and C. We controlled the pulmonary function by using a volume-cycle ventilator. In all groups, we maintained a subcutaneous cavity by insufflating CO2. Groups A and C were insufflated at 15 mm Hg; group B, at 8 mm Hg. We placed circumferential Esmarch bandages on the thorax of groups B and C to delimit superiorly and inferiorly the surgical area. Arterial blood gas analyses (ABGA) were taken from the femoral artery 60 minutes after intubation, 60 minutes after Esmarch bandage was placed and at the end of the CO2 insufflation. Statistically, results were analyzed by Wilcoxon test. P < 0.05 was considered statistically significant. Group A showed extensive subcutaneous emphysema. Two dogs died. The systemic increase of the CO2 showed a median of 9.6 mm Hg (P < 0.05). In Group B, Esmarch bandages caused increase in CO2, with a median of 1.65 mm Hg (P < 0.028). None of these dogs showed subcutaneous emphysema during the insufflation after CO2 insufflation pressure augmented with a median of 3.7 mm Hg (P < 0.028). In Group C, chest restriction increased CO2 median of 6.1 mm Hg (P < 0.043), and subcutaneous emphysema shown was less extensive than group A. The CO2 increased after insufflation a median of 16 mm Hg (P < 0.043). CONCLUSIONS: Subcutaneous cavities can be maintained open with CO2 insufflation at 8 mm Hg, limiting perfectly the surgical area; as done with Esmarch bandages, it reduces CO2 absorption and makes this procedure safe.     

不同CO2气腹压力对腹腔镜胆囊切除术后肩痛的影响

目的研究不同CO2气腹压力对腹腔镜胆囊切除术(LC术)后肩部疼痛的影响。方法将100例行LC术的患者随机分为两组,每组50例,分别设定气腹压力为1.2kPa(10mmHg)和2kPa(15mmHg)下行LC术。对比两组术后肩部疼痛发生率及程度。结果在1.2kPa下手术组,患者的术后肩部疼痛程度明显低于2kPa手术组,差异有统计学意义(χ2=22.698,P<0.05)。结论LC术后肩部疼痛的主要原因可能与人工气腹张力对膈肌牵拉刺激有关。在10mmHg低压气腹下行LC术,可显著降低LC术后肩部疼痛的发生率及程度。     

Towards painless colonoscopy: a randomized controlled trial on carbon dioxide-insufflating colonoscopy

Background: Carbon dioxide (CO₂) insufflation during colonoscopy was reported to reduce pain, but data are limited. The objective of this randomized controlled trial was to assess the effect of CO₂ insufflation on pain during and after colonoscopy. Methods: Patients were randomized into CO₂ insufflation (CO2i) or air insufflation (AIRi) groups. Pain during and after the examination were recorded using a visual analogue scale. Other outcomes included the caecal intubation rate, time to reach the caecum and complication. With questionnaire, patients’ satisfaction and acceptance of the procedure were assessed. Results: Over a 4‐month period, 96 patients were recruited. The caecal intubation rate was 96 and 98% in the CO2i group and the AIRi group, respectively. No complication occurred in the CO2i group whereas one patient from the AIRi group developed late haemorrhage after polypectomy. Patients in the CO2i group had a lower pain score during (P < 0.01) and 30 min after (P = 0.02) the examination. Significantly more patients in the CO2i group reported the examination as painless (visual analogue scale 0) during the procedure (45 vs 14%, P < 0.01) and 30 min after (70 vs 51%, P = 0.04). In both groups, high satisfaction scores were recorded. Most patients (93% for the CO2i group and 98% for the AIRi group) would accept another colonoscopy if indicated. Conclusion: Insufflation with CO₂ during colonoscopy results in less pain during and after the examination. Because of better tolerance, colonoscopy with CO₂ insufflation might gain wide acceptance in the community to be used as a screening tool.     

Right vs left side thoracoscopic sympathectomy: effects of CO2 insufflation on haemodynamics.

BACKGROUND AND AIMS: Currently, few reports of the haemodynamic impact of intrapleural CO2 insufflation in the clinical setting are available. Therefore, we conducted the present study to compare the haemodynamic changes between right and left side thoracoscopic sympathectomy (TS) for treatment of palmar hyperhidrosis (PH) under general anaesthesia. MATERIALS AND METHODS: 20 adult patients (17 males) undergoing TS were randomly allocated to two groups (each 10); group A, right side and group B, left side TS procedures were performed under general anaesthesia with single-lumen endotracheal tube. Besides the routine monitoring of vital signs, non-invasive cardiac output monitor (NICO) was used to record the stroke volume (SV), cardiac output (CO) and cardiac index (CI). Intrapleural CO2 insufflation was used. Anaesthesia was maintained with 1 MAC sevoflurane in 50% nitrous oxide in oxygen with incremental doses of sufentanil and atracurium when required. Haemodynamic parameters were obtained every 3 min then averaged over the time of surgery at phases; I) after tracheal intubation, II) after CO2 insufflation and III) after CO2 deflation. RESULTS: The CO, CI and SV showed decreased trend in both groups during phase II compared to phase I with significant differences (P < 0.05). Comparing the CO and CI variables revealed lower values in group A compared to group B but with non-significant differences (P > 0.05). While the SV variable showed significant low value in group A compared to group B (P < 0.05). CONCLUSIONS: Compared to left side TS, direct compression by CO2 against the venae cava and right atrium and ventricle during right side TS caused reduction of the venous return and hence low CO, CI and SV.     

CO_2气腹压力对腹腔镜胆囊切除术后肩痛的影响

目的:探讨CO2气腹压力对腹腔镜胆囊切除术后肩痛发生的影响。方法:随机选取行腹腔镜胆囊切除术100例,随机分为两组,每组50例,分别在1.3kPa和2kPa气腹压下行腹腔镜胆囊切除术。对比两组术后肩痛发生率及程度。结果:1.3kPa术后肩痛发生率明显低于2kPa,且多能耐受,程度较轻。结论:在1.3kPa气腹压力下行腹腔镜胆囊切除术不影响手术操作。术后肩痛发生率低,是行腹腔镜胆囊切除术较理想的气腹压。     

Acetaminophen decreases early post-thoracotomy ipsilateral shoulder pain in patients with thoracic epidural analgesia: a double-blind placebo-controlled study

OBJECTIVE: Despite effective epidural analgesia, up to 85% of post-thoracotomy patients complain of moderate-to-severe ipsilateral shoulder pain. This study assessed the efficacy of acetaminophen in decreasing postoperative shoulder pain after a thoracotomy. DESIGN: Double-blind randomized and placebo-controlled study. SETTING: University medical center. PARTICIPANTS: 65 patients. INTERVENTION: Patients were randomized into 2 groups; 31 patients received acetaminophen (group A), and 34 patients received a placebo (group P). After induction of anesthesia, patients received either a loading dose of acetaminophen, 1000 mg intrarectally, or a placebo suppository. Thereafter, acetaminophen, 650 mg, or a placebo, was administered intrarectally every 4 hours for 48 hours postoperatively. MEASUREMENTS AND MAIN RESULTS: Postoperative pain at the surgical site and shoulder pain were assessed separately every 4 hours for 48 hours using a numerical rating scale (NRS). Rescue analgesia for severe shoulder pain (NRS > 7) consisted of subcutaneous hydromorphone. Sixty-three patients experienced shoulder pain (97% prevalence). Demographic and intraoperative data were similar between the 2 groups. Average NRS for shoulder pain was higher in group P compared with group A at 8, 12, and 16 hours postoperatively (3.1 +/- 2.9, 2.6 +/- 2.6, 2.3 +/- 2.4 vs 1.8 +/- 2.6, 1.2 +/- 1.5, 1.3 +/- 1.8; P < 0.05). The total dose of hydromorphone did not differ between the 2 groups at 16, 24, and 48 hours. CONCLUSION: Acetaminophen decreases post-thoracotomy ipsilateral shoulder pain when given preemptively and regularly during the first 48 hours postoperatively in patients who received thoracic epidural analgesia.