预注去氧肾上腺素或麻黄碱对腰麻下剖宫产产妇及新生儿的影响

目的比较预注去氧肾上腺素与麻黄碱对腰麻下剖宫产术产妇及新生儿的影响。方法选择择期单次腰麻下剖宫产产妇60例,随机分为两组:去氧肾上腺素组(P组)和麻黄碱组(E组),每组30例。产妇腰麻改平卧位后即刻静脉推注去氧肾上腺素60μg或麻黄碱5mg,若产妇血压下降超过20%时使用去氧肾上腺素或麻黄碱升压。记录入室时(T0)及腰麻后1min(T1)、3min(T2)、5min(T3)、10min(T4)、胎儿娩出时(T5)的HR、SBP和DBP;记录产妇不良反应及新生儿1、5min的Apgar评分,同时检测胎儿娩出时脐静脉血气。结果 T1~T5时E组HR均明显快于P组和T0时(P0.05或P0.01)。E组和P组的低血压及高血压发生率差异无统计学意义。两组新生胎儿脐静脉血乳酸水平、血气分析及Apgar评分差异无统计学意义。E组恶心呕吐发生率明显高于P组(P0.05)。结论腰麻剖宫产术预注去氧肾上腺素能较好地防治产妇术中低血压,产妇恶心呕吐发生率较低,对新生儿无不良影响。     

静脉预注甲氧明对剖宫产腰-硬联合麻醉低血压的防治效果

目的探讨静脉预注和补救性静脉注射甲氧明对择期剖宫产腰-硬联合麻醉后低血压防治作用的临床疗效和安全性。方法 100例足月单胎妊娠拟行剖宫产产妇随机均分为:甲氧明静脉预注组(Ⅰ组),腰-硬联合麻醉,在腰麻药注入后,即刻静脉预注甲氧明2mg,如上述处理后仍出现低血压,再静注甲氧明1～2mg;无甲氧明预注组(Ⅱ组),剖宫产腰-硬联合麻醉标准治疗基础上,在腰麻药注入后,即刻不给予甲氧明及其它升压药物预注,患者麻醉后出现血压下降(下降>20%或SBP<90mmHg)静脉注射甲氧明2mg,如上述处理后仍出现低血压,再静注甲氧明1～2mg。记录腰麻前(T0),腰麻后5min(T1),10min(T2),15min(T3)和手术结束(T4)时HR,BP,以及两组新生儿脐动脉血气分析和1minApgar评分。记录两组低血压发生率,患者恶心呕吐等不良反应发生情况。结果 T1～T3时Ⅰ组SBP、DBP明显高于Ⅱ组(P<0.05),T0、T4时两组SBP、DBP和HR差异无统计学意义。术中Ⅰ组低血压及恶心呕吐等不良反应发生率明显低于Ⅱ组(P<0.05);两组新生儿1minApgar评分及新生儿脐动脉血气分析差异均无统计学意义。结论静脉预注甲氧明能有效降低剖宫产腰麻后低血压发生率,相对于补救性静脉注射甲氧明,其升高血压的效果更明显、稳定;两种方式防治产妇低血压对胎儿都比较安全。     

麻黄碱治疗腰麻剖宫产术低血压对脐动脉血气及胎儿的影响

目的 探讨应用麻黄碱纠正腰麻剖宫产术中低血压对脐动脉血气及胎儿的影响.方法 选择ASA Ⅰ或Ⅱ级产妇40例,年龄26～34岁.无妊娠合并症,无胎儿异常,足月单胎妊娠.腰麻后出现低血压(收缩压低于基础值30%).先快速输入羟乙基淀粉200/0.5 500 ml,向左侧提起子宫,抬高产妇下肢纠正低血压.3 min后,低血压有效纠正者24例(对照组),无效者16例给麻黄碱10 mg静推(麻黄碱组,必要时追加麻黄碱10 mg).胎儿娩出尚未出现第一次呼吸之前用两把血管钳钳夹一段脐带,抽取脐动脉血行血气分析.记录注腰麻药即刻至切开子宫时间、子宫切开至胎儿娩出时间、术中产妇心率、恶心呕吐及胎儿出生时的Apgar评分.结果 两组注腰麻药即刻至切开子宫时间、子宫切开至胎儿娩出时间、术中产妇心率、恶心呕吐及胎儿出生时Apgar评分差异均无统计学意义.两组脐动脉血PO2、PCO2、pH、碱剩余(BE)差异均无统计学意义.结论 适当剂量麻黄碱可安全用于治疗腰麻引起的剖宫产术中低血压,对母体及胎儿无不良影响.     

麻黄碱与去氧肾上腺素对腰麻剖宫产产妇及新生儿的影响

目的 比较麻黄碱与去氧肾上腺素用于腰麻剖宫产术中血压维持接近基础值时对产妇及新生儿的影响.方法 择期行腰麻下剖宫产术单胎足月产妇60例,随机均分为两组:Ⅰ组泵注麻黄碱4 mg/ml,Ⅱ组泵注去氧肾上腺素50μg/ml.术中调整药物输注速度以维持血压接近基础值.监测用药1、3、5、10 min、切皮时及子宫切开时MAP和HR.胎儿娩出即刻取产妇动脉血、脐动脉及脐静脉血进行血气分析和乳酸及血糖浓度检测.结果 Ⅰ组脐动脉及脐静脉血pH值和碱剩余低于Ⅱ组(P<0.05),PCO<,2>、乳酸和血糖浓度高于Ⅱ组(P<0.05).结论 去氧肾上腺素对腰麻剖宫产产妇及新生儿影响小于麻黄碱.     

甲氧明治疗腰麻下剖宫产产妇术中低血压的量-效关系

目的观察甲氧明治疗腰麻下剖宫产产妇术中低血压的量-效关系。方法选择腰麻下行剖宫产术且术中出现低血压的产妇80例,ASAⅠ或Ⅱ级,年龄24~35岁,体重52~80kg,随机均分为四组。产妇出现低血压后,分别给予甲氧明1.6mg组(A组)、甲氧明2.0mg组(B组)、甲氧明2.5mg组(C组)和甲氧明3.2mg组(D组)。计算甲氧明的ED50、ED95和95%可信区间(CI)。结果甲氧明用于治疗剖宫产术中低血压的ED50(95%CI)和EC95(95%CI)分别为1.62(1.51~1.74)mg和2.34(2.13~2.57)mg。结论甲氧明治疗腰麻下剖宫产产妇术中低血压的ED50、ED95分别为1.62mg和2.34mg。     

盐酸甲氧明对腰麻患者血流动力学影响

目的 观察盐酸甲氧明对腰麻患者血流动力学影响.方法 选择300例拟行腰麻的患者.年龄20～50岁,ASA Ⅰ或Ⅱ级,随机均分为六组.Ⅰ组在腰麻药注入前后不给予任何药物,Ⅱ组患者在腰麻药注入时肌注盐酸甲氧明0.1 mg/kg,Ⅲ组患者在腰麻药注入后出现低血压时静注盐酸甲氧明0.05 mg/kg,Ⅳ、Ⅴ、Ⅵ组分别在Ⅰ、Ⅱ、Ⅲ组基础上预输胶体8 ml/kg.所有患者经上述处理后出现明显低血压时,静注适量麻黄碱.记录基础值和腰麻后5、10、15、20、25、30 min BP、HR及麻黄碱总量以及恶心呕吐的发生率.结果 与基础值比较,Ⅴ组在腰麻后各时点中BP和HR稳定,其他各组均在腰麻后各时点出现BP下降,HR增快(P＜0.05).与Ⅰ组比较,其它组麻黄碱总量少,恶心呕吐发生率低(P＜0.05);与Ⅴ组比较,Ⅱ、Ⅲ、Ⅳ、Ⅵ组麻黄碱总量增多、恶心呕吐发生率增高(.P＜0.05).结论 麻醉前预先肌注盐酸甲氧明联合适当的胶体扩容治疗能有效地维持腰麻血流动力学的稳定,并减少低血引起的恶心呕吐的发生.     

不同剂量甲氧明与麻黄碱联合预注对剖宫产母婴的影响

目的 比较不同比例甲氧明和麻黄碱联合用于预防腰麻-硬膜外联合麻醉(combined spinal and epidural anesthesia,CSEA)剖宫产术中低血压的作用效果及对母婴的影响,评价联合用药不同药物比例的作用效果.方法 采用随机数字表法将150例拟在CSEA下行剖宫产手术的产妇分成5组(1组～5组,每组30例),分别接受5种不同剂量浓度的甲氧明和麻黄碱混合静脉给药.假设2 mg甲氧明约等效于8 mg麻黄碱,各组比例分别相当于100％、75％、50％、25％、0的甲氧明和0、25％、50％、75％、100％的麻黄碱,调节输注速率以恒速泵注.测定产妇血流动力学变化和脐带血血气,记录新生儿Apgar评分,产妇恶心、呕吐及低血压情况.结果 随1组～5组甲氧明的比例下降和麻黄碱比例的上升,低血压发生率有升高的趋势(1组3％、2组10％、3组7％、4组13％、5组30％)(P＜0.05).2组、3组恶心呕吐发生率低于其他3组(1组7％、2组3％、3组0、4组10、5组23％)(P＜0.05).1组～5组脐动脉胎儿血红蛋白值含量有下降的趋势[1组93(91～98)％、2组89(86～91)％、3组88(85～91)％、4组85(83～89)％、5组81(78～84)％](P＜0.05),二氧化碳分压有逐渐升高的趋势[1组49 (46～54) mmHg、2组51(45～56) mmHg、3组53(47～57)mmHg、4组55(50～59) mmHg、5组56(51～59) mmHg(1 mmHg=0.133 kPa)] (P＜0.05).结论 CSEA下剖宫产术不同剂量甲氧明和麻黄碱复合输注以维持血压时,随着甲氧明比例增大和麻黄碱比例减小,产妇血流动力学能得到更好的控制.0.375g/L甲氧明:0.5 g/L麻黄碱至0.25 g/L甲氧明:1 g/L麻黄碱效果较好,能产生更为有利于胎儿的效应.     

去甲肾上腺素和麻黄碱治疗子痫前期产妇腰麻后低血压效果的比较

目的 比较等效去甲肾上腺素和麻黄碱用于治疗子痫前期产妇剖宫产腰麻后低血压的效果。
方法 选择腰麻后出现低血压的子痫前期产妇111例，年龄22～36岁，BMI≤35 kg/m²， ASA Ⅱ级，随机分为去甲肾上腺素组（N组，n=56）和麻黄碱组（E组，n=55），分别在出现低血压（SBP<基础值80%）后静脉注射去甲肾上腺素4 μg或麻黄碱4 mg。观察产妇入室时、腰麻后1、3、5、10 min、胎儿娩出时HR和SBP。记录腰麻完成至胎儿娩出期间产妇心动过速（HR＞120次/分）、心动过缓（HR＜60次/分）和高血压（SBP＞基础值120%）的发生情况；以及使用血管活性药的次数和不良反应，包括恶心、呕吐、眩晕和寒战。记录新生儿Apgar评分和脐动脉血气分析。
结果 与E组比较，N组腰麻后3、5、10 min及胎儿娩出时产妇HR明显减慢（P＜0.05），心动过速发生率明显降低（P＜0.05），新生儿脐动脉血pH、HCO-3和BE明显升高（P＜0.05），乳酸（Lac）明显降低（P＜0.05）。两组产妇心动过缓和高血压的发生率、使用血管活性药的次数、眩晕和寒战的发生率差异无统计学意义。两组新生儿Apgar评分、脐动脉血PaO2、PaCO2、Glu差异无统计学意义。
结论 等效去甲肾上腺素与麻黄碱治疗子痫前期产妇腰麻后低血压的效果相似，但去甲肾上腺素的安全性更高。     

不同剂量去氧肾上腺素静脉注射对腰麻下剖宫产产妇及新生儿的影响

目的观察不同剂量去氧肾上腺素静脉注射对腰麻下剖宫产产妇及新生儿的影响。方法择期腰麻剖宫产单胎产妇60例,随机均分为三组,在蛛网膜下腔注入0.5%重比重布比卡因2.5ml,鞘内注药后立即静脉泵注去氧肾上腺素150μg(P1组)、300μg(P2组)或等量生理盐水(C组)各3ml,速率1ml/min。若发生低血压时追加去氧肾上腺素100μg。监测并记录产妇SBP、DBP、HR、每搏输出量(SV)和心输出量(CO),以及低血压、高血压、恶心呕吐及心动过缓的发生次数。记录新生儿Apgar评分,并取脐带动静脉血行血气分析。结果与入室后比较,腰麻后1、5minC组SBP、DBP明显降低(P<0.05),P1、P2组无显著变化;腰麻后1、5min和分娩前1minP1、P2组HR明显减慢,C组仅在分娩前1min显著减慢(P<0.05);腰麻后1、5minP2组SV显著升高,腰麻后5minC组显著降低(P<0.05),且腰麻后5minP1、P2组明显高于C组(P<0.05);腰麻后5min和分娩前1minP1、P2组CO显著降低(P<0.05),分娩前1minC组也显著降低(P<0.05)。P1组和P2组低血压的发生率显著低于C组(P<0.05)。P1组和P2组分别有1例和3例高血压。结论小剂量去氧肾上腺素静脉输注能减少分娩前产妇低血压的发生率,对母体和胎儿影响较小。     

腰麻剖宫产手术预注去氧肾上腺素对母婴的影响

目的探讨腰麻剖宫产手术预注去氧肾上腺素对母婴的影响。方法选择2013年6月至2015年6月间我院行腰麻剖宫产产妇76例,随机分为观察组与对照组。产妇腰麻改平卧位后观察组即刻静脉推注去氧肾上腺素60μg,对照组静脉推注麻黄碱5 mg。记录入室后(T1)、腰麻后1 min(T2)和5 min(T3)及胎儿娩出前1 min(T4)、娩出后3 min(T5)、10 min(T6)的收缩压(systolic blood pressure,SBP)、舒张压(diastolic blood pressure,DBP)、心率(HR),记录围术期产妇恶心呕吐等不良反应的发生情况。记录胎儿脐动脉血的血气指标(p H、Pa O2、Pa CO2、BE)和脐静脉血的血糖和乳酸浓度,由新生儿科医生对新生儿进行Apgar评分(1 min、5 min)。结果观察组新生儿脐静脉血的血糖和乳酸水平略低于对照组,但是比较差异无统计学意义(P0.05)。两组新生儿脐动脉血的血气指标p H值、BE、Pa CO2比较均无显著差异(P0.05)。与观察组比较,对照组的HR在T2~T6时间点明显加快,差异具有统计学意义(P0.05);对照组的HR在T2~T6时间点与同组T1时比较亦明显加快,差异具有统计学意义(P0.05)。T1~T6时两组产妇的SBP和DBP组内、组间比较均无明显差异(P0.05)。观察组产妇恶心呕吐的发生率明显低于对照组,差异具有统计学意义(P0.05);而两组产妇头晕、胸闷以及低血压的发生率比较无明显差异(P0.05)。两组新生儿的Apgar评分无明显差异(P0.05)。结论腰麻剖宫产手术预注去氧肾上腺素能较好地防治产妇术中低血压,有效降低产妇不良反应的发生,而且对新生儿无不良影响,值得临床推广。     

Prevention of hypotension during spinal anaesthesia for caesarean section

Twenty-six parturients scheduled to receive spinal anaesthesia for caesarean section were randomized to receive either isotonic saline 750 ml plus 20 ml/kg (group A) or 750 ml plus 500 ml (group B) before subarachnoid administration of bupivacaine 13 mg. Ephedrine 0.15 mg/kg i.v. followed by an infusion 0.4 mg.kg(-1) h(-1) were then administered in group B. In both groups ephedrine 10 mg/min i.v. was given if the mean arterial blood pressure decreased more than 10 mmHg. Despite the fluid preload and large doses of ephedrine noted {median (range), group A 30 mg (10-80), group B 92 mg (25-194)}, hypotension, sometimes accompanied by nausea, still occurred. Mean maternal arterial was significantly lower in group A than in group B 5-10 min after induction of spinal anaesthesia (P < 0.05). There was no difference in the frequency of nausea or vomiting, Apgar score, or pH in umbilical cord blood. One neonate in group A and 2 in group B were acidotic. In conclusion, a reduced volume loading could be compensated with an increased ephedrine administration after induction of spinal anaesthesia, without increasing the incidence of hypotension or other maternal or neonatal complications. However, the fluid volumes and/or ephedrine doses used were not sufficient to prevent hypotension altogether.     

Phenylephrine added to prophylactic ephedrine infusion during spinal anesthesia for elective cesarean section

BACKGROUND: Because ephedrine infusion (2 mg/min) does not adequately prevent spinal hypotension during cesarean delivery, the authors investigated whether adding phenylephrine would improve its efficacy. METHODS: Thirty-nine parturients with American Society of Anesthesiologists physical status I-II who were scheduled for cesarean delivery received a crystalloid preload of 15 ml/kg. Spinal anesthesia was performed using 11 mg hyperbaric bupivacaine, 2.5 microg sufentanil, and 0.1 mg morphine. Maternal heart rate and systolic blood pressure were measured at frequent intervals. A vasopressor infusion was started immediately after spinal injection of either 2 mg/min ephedrine plus 10 microg/min phenylephrine or 2 mg/min ephedrine alone. Treatments were assigned randomly in a double-blind fashion. The infusion rate was adjusted according to systolic blood pressure using a predefined algorithm. Hypotension, defined as systolic blood pressure less than 100 mmHg and less than 80% of baseline, was treated with 6 mg ephedrine bolus doses. RESULTS: Hypotension occurred less frequently in the ephedrine-phenylephrine group than in the ephedrine-alone group: 37% versus 75% (P = 0.02). Ephedrine (36+/-16 mg, mean +/- SD) plus 178+/-81 microg phenylephrine was infused in former group, whereas 54+/-18 mg ephedrine was infused in the latter. Median supplemental ephedrine requirements and nausea scores (0-3) were less in the ephedrine-phenylephrine group (0 vs. 12 mg, P = 0.02; and 0 vs. 1.5, P = 0.01, respectively). Umbilical artery pH values were significantly higher in the ephedrine-phenylephrine group than in the group that received ephedrine alone (7.24 vs. 7.19). Apgar scores were similarly good in both groups. CONCLUSION: Phenylephrine added to an infusion of ephedrine halved the incidence of hypotension and increased umbilical cord pH.     

Prevention of hypotension by a single 5-mg dose of ephedrine during small-dose spinal anesthesia in prehydrated cesarean delivery patients

To evaluate the effectiveness of prophylactic ephedrine for the prevention of hypotension associated with spinal anesthesia, 50 parturients undergoing cesarean delivery received either ephedrine 5 mg or saline IV in a double-blinded fashion immediately after the induction of spinal anesthesia. Spinal anesthesia was performed with hyperbaric bupivacaine 6.6 mg combined with sufentanil 3.3 microg as part of a combined spinal-epidural technique. All patients received 1000 mL of lactated Ringer's solution and 500 mL of hydroxyethylstarch 6% before the spinal injection. Additional ephedrine boluses (5 mg) were administered IV when the systolic blood pressure or heart rate decreased by more than 30% from baseline values, when systolic blood pressure became <100 mm Hg, or when patients complained of nausea or feeling faint. The height of the block was equal in the groups; however, more patients in the placebo group were found to develop hypotension (58% vs 25%, P < 0. 05). Only 2 (8%) patients in the ephedrine group developed hypotension with systolic blood pressure values <90 mm Hg, whereas 10 patients (42%) in the saline group experienced hypotension of this severity (P < 0.05). In addition, there was a higher incidence of nausea in the placebo-treated patients. The total amount of ephedrine administered did not differ between groups. These findings suggest that the incidence and severity of hypotension are significantly reduced by the IV administration of a prophylactic dose of 5 mg ephedrine in patients receiving small-dose spinal anesthesia for cesarean delivery. IMPLICATIONS: Ephedrine is the drug most often used to correct hypotension during spinal anesthesia for cesarean delivery in healthy patients. A single IV dose of 5 mg decreases the occurrence and limits the severity of hypotension in prehydrated subjects receiving a small-dose spinal local anesthetic-opioid combination.     

Effectiveness of intravenous ephedrine infusion during spinal anaesthesia for caesarean section based on maternal hypotension,neonatal acid-base status and lactate levels

Maternal cardiovascular changes and neonatal acid-base status, including lactate levels, were assessed in 30 healthy women undergoing elective caesarean section under spinal anaesthesia. Patients were allocated randomly to receive IV ephedrine infusion (n = 15) (5 mg.min(-1) immediately after the spinal injection or bolus administration of IV ephedrine (n = 15) (10 mg) in case of development of hypotension. Maternal and neonatal blood pressure, heart rate and acid-base status including lactate levels were compared between the groups. Systolic blood pressure in the bolus group was significantly lower when compared to the infusion group. Nausea was observed in one patient (6%) in the infusion group and nausea and vomiting were observed in 10 patients (66%) in the bolus group. Although umbilical arterial pH values were significantly lower in the bolus group, lactate levels were similar In conclusion, ephedrine infusion prevented maternal hypotension, reduced the incidence of nausea and vomiting and led to improved umbilical blood pH during spinal anaesthesia for caesarean section.     

Prophylactic intramuscular ephedrine prior to caesarean section.

Thirty healthy parturients, having given informed consent, were randomly allocated in a double-blind study to receive an intramuscular injection of either 0.9% sodium chloride (control), ephedrine 25 mg, or ephedrine 50 mg, 30 minutes prior to general anaesthesia for caesarean section. Nine patients (90%) in the 50 mg group and five patients (50%) in the 25 mg group demonstrated reactive hypertension of 20% or greater from control. The mean maximum increase in the 50 mg group was 28.2% (range 4.4-38.3%). Maternal pH was significantly lower (P = 0.03) in the ephedrine 50 mg group. Neonatal acid base status was significantly impaired in the ephedrine 50 mg group with umbilical venous pH (P = 0.0001) and umbilical arterial pH (P = 0.001) being significantly lower than the control group. The associated increase in umbilical arterial base deficit suggests a metabolic component due to fetal asphyxia related to decreased uterine blood flow. We conclude that the prophylactic administration of intramuscular ephedrine prior to spinal anaesthesia is associated with an unacceptably high incidence of maternal hypertension, and should the spinal fail and general anaesthesia be required, also results in adverse neonatal biochemical changes. The technique is therefore not to be recommended.     

Effects of preoperative methoxamine on blood loss and haemodynamic variables during transurethral prostatic resection under spinal anaesthesia

Thirty-six patients who presented for transurethral prostaticresection were allocated randomly to one of two groups. Patientsin group A were given methoxamine 10 mg i.m., 15 min beforespinal anaesthesia. Patients in group B acted as a control group.All patients received spinal anaesthesia. Preoperative administrationof methoxamine 10 mg i.m. decreased blood loss significantlyand improved haemodynamic stability compared with the controlgroup.     

Phenylephrine Added to Prophylactic Ephedrine Infusion during Spinal Anesthesia for Elective Cesarean Section

Background: Because ephedrine infusion (2 mg/min) does not adequately prevent spinal hypotension during cesarean delivery, the authors investigated whether adding phenylephrine would improve its efficacy.

Methods: Thirty-nine parturients with American Society of Anesthesiologists physical status I-II who were scheduled for cesarean delivery received a crystalloid preload of 15 ml/kg. Spinal anesthesia was performed using 11 mg hyperbaric bupivacaine, 2.5 [mu]g sufentanil, and 0.1 mg morphine. Maternal heart rate and systolic blood pressure were measured at frequent intervals. A vasopressor infusion was started immediately after spinal injection of either 2 mg/min ephedrine plus 10 [mu]g/min phenylephrine or 2 mg/min ephedrine alone. Treatments were assigned randomly in a double-blind fashion. The infusion rate was adjusted according to systolic blood pressure using a predefined algorithm. Hypotension, defined as systolic blood pressure less than 100 mmHg and less than 80% of baseline, was treated with 6 mg ephedrine bolus doses.

Results: Hypotension occurred less frequently in the ephedrine-phenylephrine group than in the ephedrine-alone group: 37%versus 75% (P = 0.02). Ephedrine (36 +/-16 mg, mean +/- SD) plus 178 +/-81 [mu]g phenylephrine was infused in former group, whereas 54 +/-18 mg ephedrine was infused in the latter. Median supplemental ephedrine requirements and nausea scores (0-3) were less in the ephedrine-phenylephrine group (0 vs. 12 mg, P = 0.02; and 0 vs. 1.5, P = 0.01, respectively). Umbilical artery p H values were significantly higher in the ephedrine-phenylephrine group than in the group that received ephedrine alone (7.24 vs. 7.19). Apgar scores were similarly good in both groups.     

Prophylactic ephedrine and hypotension associated with spinal anesthesia for cesarean delivery

Hypotension commonly accompanies induction of spinal anesthesia for cesarean section. To determine whether intravenous ephedrine prophylaxis would benefit prehydrated obstetrical patients presenting for elective cesarean section, we studied 30 patients randomly assigned to one of three experimental groups. All patients were preloaded with crystalloid (15 ml/kg), given spinal anesthesia and positioned with left uterine displacement (LUD). During induction, all patients received a 2 ml intravenous bolus and intravenous infusion of the study drug or placebo. The control group (n=10) received a saline bolus and saline infusion, the bolus group (n=10) received an ephedrine bolus (10 mg) and a saline infusion and the infusion group (n=10) received a saline bolus and a two-stage ephedrine infusion (20 mg over 12 min). After induction of anesthesia, systolic blood pressure decreased in the first 5 min in all groups. Hypotension occurred in 6/10 control patients, 5/10 bolus patients and 5/10 infusion patients. The amount of supplemental ephedrine required to treat hypotension did not differ among groups. Although the efficacy of ephedrine prophylaxis for hypotension associated with spinal anesthesia for elective cesarean section cannot be established by the small number of patients studied, this practice does not appear to be clinically relevant at the doses studied.     

Changes in systemic circulation under induced total spinal block and choice of vasopressors

Total spinal block by using 2% lidocaine 0.5 ml.kg-1 (10.0 mg.kg-1) was carried out in adult mongrel dogs. The effects of atropine 0.02 mg.kg-1, isoproterenol 0.5 mcg.kg-1, methoxamine 0.1 mg.kg-1 and ephedrine 0.5 mg.kg-1 to counteract circulatory changes by total spinal block were studied. Atropine did not exert any marked influence on circulatory system. Isoproterenol elevated HR, LV dp/dt max and CI temporarily, but did not decrease MAP and SVR. Methoxamine elevated MAP and SVR, but decreased CI. Ephedrine is a drug of choice for this situation because it elevated HR, MAP, LV dp/dt max and SVR.     

Volume preload: lack of effect in the prevention of spinal-induced hypotension at caesarean section

A randomized double-blind study of 40 women was performed to compare blood pressure changes between two groups of women following induction of spinal anaesthesia for elective caesarean section. One group received a 1 L Ringer's solution preload, administered over 10 min, before spinal anaesthesia while the other group received no preload. In both groups a prophylactic infusion of ephedrine (60 mg in Ringer's solution 1000 ml) was started immediately following intrathecal injection of local anaesthetic. There was no significant difference either in the ephedrine requirements or the incidence of hypotension between the two groups. There were no differences between the groups in terms of neonatal outcome as assessed by Apgar score, umbilical arterial and venous blood pH, and Neonatal Adaptive Capacity Scores. When ephedrine is infused prophylactically immediately following spinal anaesthesia for elective caesarean section, a 1000 ml crystalloid preload confers no advantages in terms of maternal blood pressure control or neonatal outcome.