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【摘要】 目的 了解硬膜外麻醉药物浓度和用药后侧卧时间对产妇取胎前血压、心率、心率收缩压乘积、麻醉效果以及对胎儿的影响，从而合理选择麻醉药浓度及硬膜外用药后侧卧时间。方法 选择SASⅠ～Ⅱ级择期剖宫产手术20～35岁初产妇200例，采用2×2析因实验设计，按随机发生数分为4组，Ⅰ组接受1.7％利多卡因硬膜外麻醉，穿刺置管给药后1min平卧（n1=50例）；Ⅱ组接受1.7％利多卡因硬膜外麻醉，穿刺置管给药后5min平卧（n2=50例）；Ⅲ组接受2％利多卡因硬膜外麻醉，穿刺置管给药后1min平卧（n3=50例）；Ⅳ组接受2％利多卡因硬膜外麻醉，穿刺置管给药后5min平卧（n4=50例）。观察麻醉前SBP，DBP，HR和HR×SBP，麻醉后至胎儿取出收缩压最低时的SBP，DBP，HR和HR×SBP，麻醉效果，麻醉至手术间期以及胎儿取出1min Apgar评分。结果 年龄、身高、体重、麻醉至手术间期组间差异均无显著性（P>0.05）。所有产妇组内比较，麻醉前后SBP和DBP均有明显下降（P<0.05），HR均有明显增加（P<0.05）,HR×SBP在Ⅳ组有明显下降（P<0.05），其他组差异均无显著性（P>0.05）。组间比较，浓度因素和侧卧因素对麻醉效果均有明显影响，1.7％和2％浓度越高，1min和5min侧卧越久，效果越好，且有协同作用（P<0.05）；两因素对胎儿1min Apgar评分未见明显影响（P>0.05）； 浓度因素对SBP的影响明显（P<0.05），浓度因素对DBP、HR和HR×SBP以及侧卧因素对SBP、DBP、HR和HR×SBP未见明显影响（P>0.05）。结论 在施行剖宫产麻醉时用1.7％和2％利多卡因，浓度较大，效果较好；侧卧1min和5min，时间越长，效果越好。而用1.7％利多卡因侧卧5min，麻醉平面扩散好，麻醉效果佳而对母体血压、心率和对胎儿Apgar评分影响小，择期剖宫产麻醉时使用较为理想。
【关键词】 剖宫产术；麻醉：硬膜外，效果；浓度：局麻药；时间：侧卧位；血压，心率
Impact of epidural anesthetic concentration, as well as lateral decubitus duration after administration, on anesthetic effects in cesarean section
YE Zhang-wen, YU Xue-ying,QI Lei,et al.Department of Anesthesiology,Nuclear Industry 416 Hospital,Chengdu 610051,China
【Abstract】 Objective Rational selection of epidural anesthetic drugconcentration, and of lateral decubitus duration after administration, during cesarean section. Methods 200 primiparas, aged 20～35, ASA grade Ⅰ-Ⅱ, undergoing selective cesarean section, were assigned into 4 groups according to randomly generated numbers, by using 2×2 factoral experimental design. Group Ⅰ underwent epidural anesthesia of 1.7% lidocaine and then, 1 minute after administration through indwelling catheter, had lateral decubitus （n1=50）; Group Ⅱ underwent epidural anesthesia of 1.7% lidocaine and then, 5 minutes after administration through indwelling catheter, had lateral decubitus （n2=50）; Group Ⅲ underwent anesthesia of 2% lidocaine and then, 1 minute after administration through indwelling catheter, had lateral decubitus （n3=50）; Group Ⅳ underwent anesthesia of 2% lidocaine and then, 5 minutes after administration through indwelling catheter, had lateral decubitus （n4=50）. The following markers were observed: SBP, DBP,HR, and HR×SBP prior to and after anesthesia, and at the lowest systolic pressure before the fetus was taken out after anesthesia; anesthetic effects, the period from anesthesia to operation, and Apgar scores of 1 minute after the fetus was taken out.Results There were no significant differences of maternal ages, height, weight and the period from anesthesia to operation between groups （P>0.05）. Through intra-group comparison of all parturients, SBP, and DBP were all significantly decreased, HR was significantly increased, between prior to and after anesthesia （P<0.05）, HR×SBP were significantly decreased in Group Ⅳ （P<0.05）, but there were no significant differences in other groups （P>0,05）. Through inter-group comparison, the factors of the concentration and the lateral decubitus duration had significant impact on anesthetic effects, and showed synergism （P<0.05）; both the two factors had no significant impact （P>0.05） on Apgar score of 1 minute after the fetus was taken out; the concentration factor had significant impact on SBP （P<0.05）; and the factor of the concentration showed no significant impact on DBP, HR, and HR×SBP, and the factor of the lateral decubitus duration also showed no significant impact on SBP, DBP, HR, and HR×SBP （P>0.05）. Conclusion During anesthesia of cesarean section, the ideal anesthetic method was of appropriately decreased anesthetic concentration, and appropriately increased lateral decubitus duration, which showed good anesthetic level, and good anesthetic effects, with no significant differences of impact on maternal blood pressure, heart rate, and fetal Apgar score.
【Key words】 cesarean;effect:anesthesia, epidural;concentration: anesthetic, local;duration: decubitus, lateral; blood pressure; heart rate
Intraspinal anesthesia is favorable to the parturients and the fetus in anesthesia for cesarean section in case of no contraindication［1］. The combined spinal-epidural anesthesia［1～6］is presently popular in cesarean section. Low-dose spinal anesthesia with rapid onset is applicable for parturients with emergency cesarean section, and is reinforced for delayed time through epidural block, and if necessary, epidural analgesia may also be conducted. However, blood pressure may be decreased rapidly, heart rate may be increased, or even supine hypotensive syndrome may occur; moreover, low-dose spinal anesthesia shows no sufficient anesthetic level to head, and the same-site combined epidural anesthesia has a limited range of diffusion［7,8］.Therefore, epidural block is also the mainstream anesthetic method for cesarean section. It has less impact on blood pressure than spinal anesthesia, with lower incidence of supine hypotensive syndrome. However, epidural block is of slower onset. Stress shall be laid clinically on how to overcome such defects, and exert its predominance. To provide more rational application of anesthesia for cesarean section, we conducted a clinical study on epidural anesthetic concentration, as well as lateral decubitus duration after administration, by using 2×2 factoral experimental design for 200 primiparas from Apr. 2004 to Aug. 2005.
1 Clinical Data and Method
1.1 Enrolment criteria Primiparas, aged 20-35, with ASA Grade I-II, undergoing selective-period cesarean section.
1.2 Exclusion criteria Women with gestational hypertension syndrome or with bleeding or coagulation disorders were excluded. Prior to anesthesia, women with supine hypotensive syndrome during the gestation, or with a history of intraspinal anesthesia at the loin were excluded from this study. After epidural administration, women whose blood pressure was unable to be detected due to chill, or who showed no anesthetic effects, were excluded. Women with gestational hypertension syndrome or with bleeding or coagulation disorders were excluded too.
1.3 Clinical Design and Data 200 Primiparas who met the enrolment criteria, except those belonging to exclusion criteria, were selected, and assigned into 4 groups according to randomized numbers. Group Ⅰ underwent epidural anesthesia of 1.7% lidocaine and then, 1 minute after administration through indwelling catheter, had lateral decubitus （n1=50）; Group Ⅱ underwent epidural anesthesia of 1.7% lidocaine and then, 5 minutes after administration through indwelling catheter, had lateral decubitus （n2=50）; Group Ⅲ underwent epidural anesthesia of 2% lidocaine and then, 1 minute after administration through indwelling catheter, lateral decubitus （n3=50）; Group Ⅳ underwent epidural anesthesia of 2% lidocaine and then, 5 minutes after administration through indwelling catheter, had lateral decubitus （n4=50）.
1.4 Standardized Operational Method of Anesthesia In all observed parturients with left-lateral flexion positioning, a catheter was placed into epidural space through interspace between lumbar 1～2, and then 5 ml of lidocaine was injected into epidural space through interspace between lumbar 3～4, and observed for 1 minute; if no poisoning of local anesthetics occurred, then inject 3～5 ml of lidocaine solution through the indwelled catheter at lumbar vertebra 1～2; then: Let Groups Ⅰ and Ⅲ have dorsal decubitus after lateral decubitus 1 minute; 4 minutes later, detect anesthetic level, and supplement anesthetic if necessary. Let Groups Ⅱ and Ⅳ have dorsal decubitus after lateral decubitus 5 minutes, detect anesthetic level, and supplement lidocaine if necessary.
1.5 Transfusion Use 5% GNS or lactated Ringer's solution at the rate of 500～1000 ml/h; increase the rate or use a plasma substitute in case of significant decrease of blood pressure.
1.6 Observation and Recording Items parturient's age, height, and weight were recorded; SBP, DBP, and HR of pre-anesthesia, as well as at the lowest systolic pressure before the fetus was taken out after anesthesia, were observed. The period from anesthesia to operation, and apgar score of 1 minute after the fetus was taken out were recorded; the product of heart rate and systolic blood pressure （SBP×HR） was calculated. Anesthetic effect was assessed by following standard.Overall score of anesthetic effect: no effect: belonging to exclusion criteria; 1: effective, but with skin-cutting pain, needing some auxiliary drugs; 2: without skin-cutting pain, but with tractive pain; 3: without skin-cutting pain, but with discomfort during the operation, or not ideal muscle relaxation; 4: without any pain, and with satisfactory muscle relaxation.
1.7 Statistical Analysis Statistical software: SAS System for Windows （version 9.00）.Variance analysis of the 2×2 factoral design was conducted for: ages; height; weight; anesthetic effect ratings; the period from anesthesia to operation, and Apgar scores of 1 minute after the fetus was taken out; SBP, DBP, HR, and SBP×HR prior to and after anesthesia. t Test was conducted for intra-group comparison. α＝0.05.
1.8 Medical Ethics It met the requirements of law and ethics to supplement with an intravenous drug in case of no or poor anesthetic effects, and was agreed by the Scientific & Technological Committee of our hospital.
2 Result
2.1 General Data Variance analysis of the 2×2 factoral design was conducted for general data such as ages, weight, height, the period from anesthesia to operation, and Apgar scores, value of P>0.05; in all inter-group comparisons, P>0.05 （Table 1）.Table 1 General Data of Maternal
2.2 Comparison of Anesthetic Effects Table 2. Table 2 Ratings of Anesthetic Effects Notes: no effect: belonging to exclusion criteria; 1: effective, but with skin-cutting pain, needing some auxiliary drugs; 2: without skin-cutting pain, but with tractive pain; 3: without skin-cutting pain, but with discomfort during the operation, or not ideal muscle relaxation; 4: without any pain, and with satisfactory muscle relaxation. Data in the table were expressed in mean±SD. Factor of the concentration: F＝6.12, P=0.0142<0.05; factor of the lateral decubitus duration: F＝17.0, P<0.0001; interaction of the two factors: F＝7.56,P=0.0065<0.05）.
2.3 Apgar Scores of 1 minute after the fetus was taken out Table 3. Table 3 Apgar scores of 1 minute after the fetus was taken outNotes:Data were expressed in mean±SD; factor of the concentration: F＝0.05, P=0.6260>0.05; factor of the lateral decubitus duration: F＝2.37, P=0.1250>0.05; interaction of the two factors: F＝0.19, P=0.6603>0.05.）
2.4 Impact on Blood Pressure and Heart Rate In all the 4 Groups, prior to anesthesia and at the lowest systolic pressure before the fetus was taken out after anesthesia, SBP and DBP were significantly decreased （P<0.05）, HR was significantly increased （P<0.05）, and HR×SBP was significantly decreased only in Group Ⅳ （2% lidocaine, 5-minute） （P<0.05）. Through inter-group comparison, the factor of the concentration had significant impact on SBP, DBP, and HR after anesthesia （P<0.05）, and had no significant impact on other markers （P>0.05） （Table 4）. Table 4 Changes of Blood Pressure and Heart Rate prior to and after Anesthesia in parturients of the 4 Groups Notes: C: Concentration factor; L: lateral factor; Inter: interaction; Total: total impact; Pror to: Pror to anesthesia; After: at the lowest systolic pressure before the fetus was taken out after anesthesia; Data were expressed in mean±SD; t test was conducted for intra-group comparison, α＝0.05,# indicated P<0.05; variance analysis of the 2×2 factoral design was conducted for inter-group comparison. Data of the table were expressed in “F value/P value”）.
3 Discussion
This clinical study adopted the 2×2 factoral design, which was able to discover impact of epidural anesthetic concentration, and lateral decubitus duration after administration, on anesthetic effects, fetal Apgar score, as well as maternal blood pressure and heart rate, and also interaction of the two factors, to facilitate selection of rational methods and drugs for anesthesia for cesarean section, and to decrease occurrence of complications, for safety of both mother and baby.
3.1 Relationship of Anesthetic Effects with Epidural Anesthetic Concentration and Lateral Decubitus Duration The sufficient range of anesthetic block （anesthetic level） plays a key role in ensuring anesthetic effects. Most people［1,5,7,10,12］think that upper level should reach T4 level; however, if it reaches such level, then the incidence of supine hypotension syndrome will be increased significantly, and will impact the fetus and the mother. The lower level shows no problem in spinal anesthesia, but epidural anesthesia needs sufficient lower-level. Therefore, we selected two-site puncture, to facilitate diffusion of anesthetics. Some people suggested the combined spinal-epidural anesthesia to decrease the dose of spinal anesthesia, which might encounter the problem of insufficient upper level, while increased dose might increase supine hypotension syndrome. This study investigated the comprehensive anesthetic effects, taking the upper level and the lower level （including peritoneal tractive response） into consideration. The result showed that, there were significant differences of anesthetic effects in the 4 Groups （P<0.05）: in comparison of 1.7% lidocaine and 2% lidocaine, the higher concentration showed better effects; in comparison of 1-minute and 5-minute lateral decubitus, the longer the time was, the better the effects were. In this study, the Group with 1.7% lidocaine and 5-minute lateral decubitus showed better effects, possibly related with the plan of the same dose and different volumes, adopted by the study. Nakayama M. et al［9,10］.thought that during obstetrical and gynecological operation, epidural administration of 1% and 2% lidocaine in the same dose and different volumes showed no significant difference of anesthetic effects, which mainly depended on the total dose of the anesthetics. Studies by Kaneko T., et al［11］.also demonstrated that the volume of the local anesthetics showed no linear relationship with diffusion of epidural anesthesia. However, Okutomi T., et al［12］.thought that administration of saline in large amount, prior to epidural local anesthetics, increased scope of anesthetic diffusion. Animal experiments conducted by Lee I., et al［13］.showed that, the larger the volume of epidural injection was, the larger the scope of diffusion was. Through analysis, inadequate anesthetic effects occurred in partial patients were possibly due to insufficient upper or lower level on the one hand, and due to prolonged induction of anesthesia on the other hand. We suggested that, insufficient upper or lower level needed adjusting patient's posture or increase anesthetic dose. According to patient's condition and anatomic characteristics, increased lateral decubitus duration was also feasible, and might decrease induction time of anesthesia. It was also consistent with the results of this study. In this study, patients without any anesthetic effects were excluded, thus the local anesthetics was ensured to inject into epidural space.
3.2 Relationship of Apgar Fetal Ratings, and Epidural Anesthetic Concentration and Lateral Decubitus Duration The result of this study demonstrated that, epidural anesthetic concentration and lateral decubitus duration had no significant impact on apgar scores 1 minute after the fetus was taken out （P>0.05）; however, statistics was not conducted for apgar scores 5 and 10 minutes after the fetus was taken out. Setayesh AR,et al［14］.adopted 1-minute and 5-minute apgar scores in evaluation of cesarean fetuses at head-down tilt position, and suggested that they had no significant relationship with head-down tilt position.
3.3 Relationship of Maternal Blood Pressure, Heart Rate, and HR×SBP, and Epidural Anesthetic Concentration and Lateral Decubitus Duration The result of this study demonstrated that, significant changes occurred in maternal blood pressure and heart rate of primiparas in the 4 Groups, who underwent epidural anesthesia; blood pressure was decreased and heart rate were increased significantly, suggesting inherent anesthetic effects. No significant changes occurred in HR×SBP, suggesting good compensation of those primiparas. There were difference of changes in primiparas of the 4 Groups: local anesthetic concentration had no significant impact on heart rate, but showed significant impact on blood pressure; the higher the concentration was, the more rapidly the blood pressure was decreased; decreased epidural anesthetic concentration was able to decrease supine syndrome. Lateral decubitus duration showed no statistically significant impact on blood pressure, heart rate, and HR×SBP.
In view of the above discussed, we suggested that, during anesthesia of cesarean section, the ideal anesthetic method was of appropriately decreased anesthetic concentration, and appropriately increased lateral decubitus duration, which showed good anesthesia level spread, and good anesthetic effects, with no significant differences of impact on maternal blood pressure, heart rate, and fetal Apgar score.
（Acknowledgements:We wish to thank the nursing staff of operating-room and the obstetrician of 416 hospital.of CNNC.）
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作者单位：610051 四川成都，核工业416医院麻醉科