Sensorimotor anesthesia and hypotension after subarachnoid block: combined spinal-epidural versus single-shot spinal technique

The extent of the intrathecal compartment depends on the balance between cerebrospinal fluid and subatmospheric epidural pressure. Epidural insertion disrupts this relationship, and the full impact of loss-of-resistance on the qualities of subarachnoid block is unknown. In this study we sought to determine if subarachnoid block, induced by combined spinal-epidural (CSE) using loss-of-resistance to air could render higher sensory anesthesia than single-shot spinal (SSS) when an identical mass of intrathecal anesthetic was injected. Sixty patients, scheduled for minor gynecological procedures, were randomly allocated into three groups all receiving 10 mg of 0.5% hyperbaric bupivacaine. In the SSS group, intrathecal administration was through a 27-gauge Whitacre spinal needle inserted at the L3-4 level. For the CSE group, the epidural space was identified with an 18-gauge Tuohy needle using loss-of-resistance to 4 mL of air. After intrathecal administration, a 20-gauge catheter was left in the epidural space. No further drug or saline was administered through the catheter. The procedure was repeated in group CSE ((no-catheter)) except without insertion of a catheter. Sensorimotor anesthesia was assessed at regular 2.5-min intervals until T10 was reached. In all aspects, there was no difference between CSE and CSE ((no-catheter)). Peak sensory level in SSS was lower than CSE and CSE ((no-catheter)) (median T5 [max T3-min T6] versus (T3 [T1-4] and (T3 [T2-5]) (P < 0.01). During the first 10 min postblock, dermatomal thoracic block was the lowest in SSS (P < 0.05). Time for regression of sensory level to T10 was also shortest in SSS. Hypotension, ephedrine use and period of motor recovery were more pronounced in CSE and CSE ((no-catheter)). We conclude that subarachnoid block induced by CSE produces greater sensorimotor anesthesia and prolonged recovery compared with SSS. There is also a more frequent incidence of hypotension and vasoconstrictor use despite using identical doses and baricity of local anesthetic. IMPLICATIONS: This study confirms that induction of subarachnoid block by a combined-spinal epidural technique produces a greater sensorimotor anesthesia and results in prolonged recovery when compared with a single-shot spinal technique. There is a more frequent incidence of hypotension and vasoconstrictor administration despite identical doses of intrathecally administered local anesthetic.     

A randomized trial of crystalloid versus colloid solution for prevention of hypotension during spinal or low-dose combined spinal-epidural anesthesia for elective cesarean delivery

BACKGROUND: Spinal anesthesia for cesarean delivery is commonly associated with hypotension and nausea and vomiting, and preload with crystalloid or colloid solution is widely recommended. Low-dose spinal via the combined spinal-epidural technique appears to cause less hypotension and nausea and vomiting. The aim of this study was to investigate whether the combined use of colloid preload and combined spinal-epidural technique might further reduce the rates of these symptoms. METHODS: Women undergoing elective cesarean delivery were randomly allocated to one of four groups (50 in each) to receive crystalloid preload before spinal anesthesia, colloid preload before spinal anesthesia, crystalloid preload before combined spinal-epidural anesthesia, and colloid preload before combined spinal-epidural anesthesia. The incidences of hypotension and nausea and vomiting were compared. Spinal anesthesia was performed with 0.5% hyperbaric bupivacaine 9 mg and fentanyl 20 microg, and combined spinal-epidural anesthesia with 0.5% hyperbaric bupivacaine 6 mg + fentanyl 20 microg followed by epidural injection of 0.25% bupivacaine 10 mL. RESULTS: The frequencies of hypotension were 44%, 18%, 24%, and 20% in crystalloid preload-spinal anesthesia, colloid preload-spinal anesthesia, crystalloid preload-combined spinal epidural anesthesia, and colloid preload-combined spinal epidural anesthesia groups, respectively. The frequencies of nausea and vomiting were 20%, 2%, 8%, and 4% in respective groups. CONCLUSION: Colloid preload and low-dose spinal anesthesia alone or in combination lowered the incidences of hypotension and nausea. However, the combination of two methods failed to demonstrate further decreases in the incidence of the symptoms compared to the colloid-spinal anesthesia or crystalloid-combined spinal-epidural anesthesia groups.     

Combined low-dose spinal-epidural anesthesia versus single-shot spinal anesthesia for elective cesarean delivery

Combined spinal-epidural anesthesia balancing low-dose intrathecal bupivacaine/fentanyl and low-dose epidural bupivacaine may be more useful than single-shot spinal anesthesia for cesarean delivery in reducing incidences of adverse effects such as hypotension and nausea and in shortening motor recovery. Combined spinal-epidural anesthesia (n=50) or spinal anesthesia (n=50) was randomly performed in 100 parturients. Intrathecal bupivacaine 6 mg added by fentanyl 20 mug followed after 5 min by 10 mL of 0.25% epidural bupivacaine were used for combined spinal-epidural and intrathecal bupivacaine 9 mg with fentanyl 20 mug for spinal anesthesia. The initial sensory block level was higher in the spinal group (P<0.001), although the maximum levels were the same (T3). Complete surgical anesthesia was achieved and no patient complained of intraoperative pain in either group. Patients in the spinal group had denser motor block in the extremities and a higher incidence of hypotension (P<0.05) and nausea and vomiting (P<0.05). Motor recovery was faster in the combined spinal-epidural group (P<0.001). We concluded that combined spinal-epidural anesthesia using low-dose local anesthetic-opioid spinal anesthesia and routine epidural supplementation before surgery had some potential advantages over single-shot spinal anesthesia in the lower incidences of adverse effects and quicker recovery.     

The effect of right versus left lateral decubitus positions on induction of spinal anesthesia for cesarean delivery

Induction of spinal anesthesia for cesarean delivery in the left lateral (LL) decubitus position combined with intraoperative left uterine displacement may result in pooling of local anesthetic onto one side of the body. We studied the effect of the right lateral (RL) and LL decubitus positions during placement of spinal anesthesia on the intrathecal spread of 0.5% hyperbaric bupivacaine plus fentanyl in 60 term parturients. Though all parturients acquired a loss of cold sensation at T4 15 min after intrathecal injection, more parturients in the LL group than in the RL group did so at 5 min (P < 0.05). The maximum levels of sensory blockades, amounts of fluid, vasopressor, and supplementary analgesia used, and the incidence of postoperative complications were similar. We conclude that the two positions can be used equally well when hyperbaric bupivacaine and fentanyl are used in cesarean delivery under spinal anesthesia. IMPLICATIONS: We conducted a double-blinded randomized trial comparing the spread of spinal anesthesia placed with a parturient in either the right or left lateral position. There was a faster onset in the left lateral group; however, the maximum block heights and the time taken to achieve them were similar in both groups.     

去甲肾上腺素预防腰硬联合麻醉下剖宫产低血压对母婴的影响

目的研究去甲肾上腺素预防腰硬联合麻醉下剖宫产低血压对母婴的影响。方法采用前瞻性研究方法,选择腰硬联合麻醉下择期行剖宫产的患者60例,按区组分A、B、C三组,每组20例。在麻醉开始前20 min分别按照以下速度恒速泵入药品,A组去甲肾上腺素0.05μg/kg·min,B组去甲肾上腺素0.1μg/kg·min,C组生理盐水0.1μg/kg·min,均持续20分钟停止。三组患者均在L_(3-4)间隙注入0.5%罗哌卡因3 mL行腰麻。观察记录三组患者以下时间点的平均动脉压(MAP)及心率(HR)变化,麻醉前(T_1)、腰麻给药(T_2)、给药后5 min(T_3)、给药后10 min(T_4)、给药后20 min(T_5)和术毕(T_6)术后8 h(T_7)和术后24 h(T_8),观察三组新生儿Apgar评分、血气分析、产妇不良反应发生情况。结果三组患者T_1时MAP及HR差异无统计学意义,A、B两组患者在各时间点MAP及HR差异无统计学意义(P0.05)。与T_1时比较,C组患者T_3、T_4、T_5时MAP明显降低,T_4时HR明显降低,差异有统计学意义(P0.05)。T_3、T_4、T_5时C组患者MAP明显低于A组和B组,差异有统计学意义(P0.05)。三组胎儿脐血PaO_2、PaCO_2、PH水平对比均不明显,差异均无统计学意义(P0.05)。A、B组患者恶心、呕吐、头痛发生率均显著低于C组,差异均有统计学意义(P0.05)。三组新生儿1 min、5 min的Apgar评分比较不明显,差异均无统计学意义(P0.05)。结论麻醉前去甲肾上腺素0.05μg/kg·min可有效预防腰硬联合麻醉下剖宫产低血压,且对母婴的影响较小,安全性较佳。     

Low-dose combined spinal-epidural anesthesia for cesarean delivery: a comparison of three plain local anesthetics

The new local anesthetics have been poorly studied for intrathecal use during Cesarean section surely in low doses and in combination with an opioid substance. The purpose of the present study was to compare bupivacaine and the newer local anesthetics in equipotent doses. During the induction of combined spinal-epidural anesthesia, 91 elective Cesarean section patients were randomly assigned to receive a spinal injection of either 10 mg ropivacaine or 6.6 mg bupivacaine or levobupivacaine both combined with sufentanil 3.3 microg. After securing the epidural catheter patients were turned to the supine position respecting a 15 degrees left lateral tilt. The three local anesthetics were compared with respect to sensory and motor block, the need for epidural supplementation, the severity of hypotension and neonatal outcome. More patients in bupivacaine had a Bromage-3 motor block at incision. The ropivacaine group required additional local anesthetics by the epidural route in 23% of the cases versus 10% in the bupivacaine group and 9% with levobupivacaine. This caused the interval between the spinal injection and the end of surgery to be longer in the ropivacaine group. Hemodynamic values were comparable between the three groups although a trend towards better systolic blood pressures and a lower incidence of severe hypotension were noticed in favor of levobupivacaine. Apgar scores and umbilical pH values did not differ. When performing a low-dose combined spinal-epidural technique for Cesarean section, the present study confirms that the new local anesthetics can be used successfully, induce less motor block but that ropivacaine requires at least a 50% larger dose than bupivacaine or levobupivacaine.     

Intrathecal morphine overdose during combined spinal-epidural block for Caesarean delivery

We describe a 25 mg intrathecal morphine overdose duringa combined spinal–epidural block for a Caesarean delivery.Naloxone infusion (5.24 mg over 24 h) was startedprior to the patient becoming symptomatic and almost immediatelyafter the overdose. Invasive therapeutics such as mechanicalventilation were avoided. Br J Anaesth 2002; 89: 925–7     

Prophylactic phenylephrine infusion for preventing hypotension during spinal anesthesia for cesarean delivery

In a randomized, double-blinded, controlled trial, we investigated the prophylactic infusion of IV phenylephrine for the prevention of hypotension during spinal anesthesia for cesarean delivery. Immediately after intrathecal injection, phenylephrine was infused at 100 microg/min (n = 26) for 3 min. From that point until delivery, phenylephrine was infused at 100 microg/min whenever systolic arterial blood pressure (SAP), measured each minute, was less than baseline. A control group (n = 24) received IV bolus phenylephrine 100 microg after each measurement of SAP <80% of baseline. Phenylephrine infusion decreased the incidence (6 [23%] of 26 versus 21 [88%] of 24; P < 0.0001), frequency, and magnitude (median minimum SAP, 106 mm Hg; interquartile range, 95-111 mm Hg; versus median, 80 mm Hg; range, 73-93 mm Hg; P < 0.0001) of hypotension compared with control. Heart rate was significantly slower over time in the infusion group compared with the control group (P < 0.0001). Despite a large total dose of phenylephrine administered to the infusion group compared with the control group (median, 1260 microg; interquartile range, 1010-1640 microg; versus median, 450 microg; interquartile range, 300-750 microg; P < 0.0001), umbilical cord blood gases and Apgar scores were similar. One patient in each group had umbilical arterial pH <7.2. Prophylactic phenylephrine infusion is a simple, safe, and effective method of maintaining arterial blood pressure during spinal anesthesia for cesarean delivery. IMPLICATIONS: In patients receiving spinal anesthesia for elective cesarean delivery, a prophylactic infusion of phenylephrine 100 microg/min decreased the incidence, frequency, and magnitude of hypotension with equivalent neonatal outcome compared with a control group receiving IV bolus phenylephrine.     

Comparison of sequential combined spinal-epidural anesthesia and spinal anesthesia for cesarean section

AIM: The aim of our study was to prove that by using sequential combined spinal-epidural (CSE) anesthesia it is possible to overcome the limits connected to the use of spinal anesthesia (SA) alone for elective cesarean section. METHODS: We examined 100 women submitted to cesarean section; SA was administered to 50 patients and sequential CSE technique to the other 50. In every woman before execution of the anesthesia we infused 500 mL of a plasma expander and a previous administration of 5 mg of ephedrine. The CSE was executed at the L1-L2 intervertebral space, administering in spinal anesthesia 5 mg of levobupivacaine with 5 _g of sufentanil, and in peridural anesthesia 10-12 mL of levobupivacaine 0.25% according to the patient's height. The peridural catheter for postoperative analgesia was then positioned. In the group of women submitted only to SA, 7.5-8 mg of levobupivacaine was injected, according to the patient's height, in the L1-L2 intervertebral space, with 5 _g of sufentanil. We considered the following adverse effects: hypotension; bradycardia; vomiting; intraoperative discomfort and motor block. RESULTS: The results obtained showed that, with a P < or = 0.05, the incidence of motor block (P < 0.001), discomfort (P < 0.001) and hypotension (P = 0.021) in the SA group is greater than in the CSE group. The difference in the incidence of vomiting (P = 0.147) and bradycardia (P = 0.067) between the 2 groups is not statistically significant. CONCLUSIONS: In our opinion sequential CSE can be considered an important step forward in the regional anesthesia used for elective cesarean section.     

Effects of epidural injection on spinal block during combined spinal and epidural anesthesia for cesarean delivery

BACKGROUND AND OBJECTIVES: Epidural injection has been known to enhance spinal anesthesia in combined spinal and epidural (CSE) anesthesia. Saline and local anesthetics have been reported to have a volume effect, elevating sensory level when supplementing a volume into the epidural space. We evaluated the effects of epidural injection when using the CSE technique for cesarean delivery. METHODS: Sixty-six parturients were allocated randomly into group C (control, n = 21), S (saline, n = 21), or B (bupivacaine, n = 24): epidural injections of 10 mL saline and 0.25% bupivacaine were given in groups S and B, respectively, 10 minutes after they received 8 mg of 0.5% hyperbaric bupivacaine intrathecally, and no injection was given in group C. The sensory level at 10 minutes, the maximal level and the time to reach it, and degree of motor block and muscle relaxation were compared. We also investigated intraoperative side effects and postoperative findings in the postanesthesia care unit. RESULTS: Epidural injection raised the sensory level significantly in groups S and B, but the maximal height of sensory block and degree of muscle relaxation did not differ among the groups. Fewer patients complained of intraoperative pain in group B than in the other groups (P <.001). CONCLUSIONS: We could not achieve satisfactory surgical analgesia with 8 mg of hyperbaric bupivacaine injected into the subarachnoid space using the needle-through-needle technique in cesarean deliveries. An epidural saline injection elevated the sensory level, which did not improve the spinal block, whereas an epidural injection of 10 mL of 0.25% bupivacaine enhanced the spinal block and sustained the block postoperatively.     

Sequential combined spinal-epidural anesthesia for cesarean section in a woman with a double-outlet right ventricle

The number of women with complex cyanotic heart disease reaching childbearing age is continuously increasing. For anesthesiologists, management of this 'new' obstetric population is particularly challenging. We report the case of a parturient with a palliated double-outlet right ventricle, who underwent a cesarean section at 34 weeks with low-dose sequential combined spinal-epidural anesthesia with patient-controlled epidural postoperative analgesia. Anesthetic considerations and specific limitations of invasive monitoring are discussed, along with a review of recent literature on maternal and neonatal complications associated with pregnancies in women with cyanotic congenital heart disease.     

Differing incidences of relevant hypotension with combined spinal-epidural anesthesia and spinal anesthesia

In this investigation we assessed whether patients receiving spinal anesthesia (SPA) as part of combined spinal-epidural anesthesia (CSE) more often experience relevant hypotension than patients receiving SPA alone. From January 1, 1997, until August 5, 2000, electronic anesthesia records from 1596 patients having received SPA and 1023 patients having received CSE for elective surgery were collected by using a computerized anesthesia record-keeping system. Relevant hypotension was defined as a decrease of mean arterial blood pressure of more than 30% within a 10-min interval and a therapeutic action of the attending anesthesiologist within 20 min after onset. Electronic patient charts were reviewed by using logistic regression with a forward stepwise algorithm to identify independent risk factors that were associated with an increased incidence of hypotension after CSE. Univariate analysis was performed to assess differences in biometric data and relevant risk factors for hypotension between the two procedures. The incidence of relevant hypotension was more frequent with CSE than with SPA alone (10.9% versus 5.0%; P < 0.001). In the multivariate analysis, arterial hypertension (odds ratio, 1.83; 95% confidence interval, 1.21-2.78) and sensory block height >T6 (odds ratio, 2.81; 95% confidence interval, 1.88-4.22) were found to be factors associated with hypotension in the CSE group. Compared with patients receiving SPA alone, patients undergoing CSE had a significantly more frequent prevalence of arterial hypertension and higher sensory block levels (P < 0.01) despite smaller amounts of local anesthetics. In this study, patients receiving CSE had an increased risk for relevant hypotension as compared with patients with SPA alone. Part of this effect seems to be due to the procedure alone and not only because this population is at higher risk. IMPLICATIONS: This study, based on a large number of patients with a retrospective design by using on-line recorded data, suggests that spinal anesthesia as part of combined spinal-epidural anesthesia may more often lead to relevant hypotension than spinal anesthesia alone. Preexisting arterial hypertension and a sensory block height exceeding T6 are major risk factors for the development of this complication.     

Bilateral ultrasound-guided transversus abdominis plane block combined with ilioinguinal-iliohypogastric nerve block for cesarean delivery anesthesia

The ultrasound-guided transversus abdominis plane block and ilioinguinal-iliohypogastric nerve block have been shown to provide pain relief after abdominal surgery. A combination of the 2 blocks may provide acceptable surgical anesthesia for cesarean delivery. We describe 4 women who had contraindications to neuraxial anesthesia, who underwent cesarean delivery with ultrasound-guided bilateral transversus abdominis plane block combined with ilioinguinal-iliohypogastric nerve block using 40 mL 0.5% ropivacaine. Breakthrough pain during the delivery of the fetus was treated with small doses of IV ketamine and propofol. We suggest that this technique may be an alternative to local anesthesia for cesarean delivery in clinical practice.     

Ultra-low dose combined spinal-epidural anesthesia with intrathecal bupivacaine 3.75 mg for cesarean delivery: a randomized controlled trial

BACKGROUND: We wished to investigate the feasibility of an ultra low-dose combined spinal-epidural technique in providing surgical anesthesia for uncomplicated cesarean deliveries in a randomized, double-blind controlled trial. METHOD: Forty-four normotensive, non-obese patients were randomized to receive either intrathecal hyperbaric bupivacaine 3.75 mg (low dose group, n=22) or 9 mg (conventional group, n=22), in addition to intrathecal fentanyl 25 microg, morphine 100 microg, and epidural 1.5% lidocaine 3 mL. Sensorimotor anesthesia and hemodynamic data were assessed at 2.5-min intervals for the first 15 min. RESULTS: The maximal sensory block achieved in the low-dose group was significantly lower than that in the conventional group (median T3, [range T2-T6] vs. T2 [C2-T6], P<0.001) with a longer time taken to reach maximal sensory block. The low-dose group had less motor block, faster sensory regression to T10 dermatome and faster motor recovery to Bromage 0 (all P<0.001). The block failed to reach T6 bilaterally within 10 min in one patient in the low-dose group and two in the conventional group, with no significant difference in the need for epidural supplementation before or after delivery of the baby. The low-dose group experienced less hypotension (14% vs. 73%, P<0.001) with less ephedrine usage (0.68 vs. 17.5 mg, P<0.001). There was no difference in operating conditions and other side effects (shivering, pruritus). CONCLUSION: We conclude that this technique results in a significantly lower incidence of maternal hypotension and has a role in high-risk parturients in whom maintenance of stable hemodynamics is imperative.     

Comparison between general,spinal, epidural,and combined spinal-epidural anesthesia for cesarean delivery: a network meta-analysis

BackgroundThis study is a network meta-analysis to compare maternal and fetal outcomes associated with four different anesthetic techniques for cesarean delivery.MethodsAn arm-based, random-effects frequentist network meta-analysis was performed. A random effect model was selected considering deviance information criteria. Randomized trials reporting the following outcomes were included: Apgar score at 1- or 5-min; umbilical arterial and venous pH; umbilical arterial pH <7.2; and neonatal score at 2–4 hours. Loop-specific heterogeneity was evaluated by risk of odds ratio and τ². Quality of evidence was assessed using the GRADE approach.ResultsData from 46 randomized trials including 3689 women contributed to the study. There were significant differences in Apgar score ≤6 at 1 min between spinal versus general anesthesia (odds ratio 0.27, 95% confidence interval [CI] 0.13 to 0.55: moderate quality evidence) and Apgar scores at 1- and 5-min, favoring spinal anesthesia. Umbilical venous pH associated with epidural anesthesia was significantly higher than that with general anesthesia (mean difference 0.010, 95% CI 0.001 to 0.020: moderate quality evidence) or spinal anesthesia. Spinal anesthesia was ranked best for Apgar score ≤6 at 1-min (SUCRA=89.8), Apgar score at 1-min (SUCRA=80.4) and 5-min (SUCRA=90.5). Epidural anesthesia was ranked highest for umbilical venous pH (SUCRA=87.4) and neonatal score (SUCRA=79.3).ConclusionsSpinal and epidural anesthesia were ranked high regarding Apgar scores and epidural anesthesia was ranked high regarding umbilical venous pH, but the results were based on small heterogeneous studies with high or unclear risks of bias.     

Comparative study on the manually-controlled variable-rate versus fixed-rate infusion of norepinephrine for preventing hypotension during spinal anesthesia for cesarean delivery

Study objectivePrevious studies have shown that prophylactic norepinephrine infusion is superior to intermittent bolus administration in preventing post-spinal hypotension. Nevertheless, it is still controversial whether manually-controlled variable-rate infusion is more effective than fixed-rate infusion. The purpose of the present study was to compare the efficacy of variable-rate infusion and fixed-rate infusion of norepinephrine for prophylaxis against maternal hypotension and maintaining hemodynamic stability during spinal anesthesia for cesarean delivery to determine more effective mode for clinical practice.DesignA prospective randomized, controlled study.SettingOperating room, Women's Hospital, Zhejiang University School of Medicine.PatientsA total of 161 parturients scheduled for elective cesarean delivery with spinal anesthesia were randomized into Group F (fixed-rate infusion) and Group V (variable-rate infusion).InterventionsParturients received prophylactic norepinephrine infusion concurrent with the intrathecal injection at rate started at 0.05 μg/kg/min. In Group F, norepinephrine was administered continuously at a fixed (on-off) rate, and a bolus of norepinephrine 5 μg or 10 μg was given when systolic blood pressure (SBP) decreased by 20% or more of baseline. In Group V, manually adjusted norepinephrine infusion within the range 0–0.14 μg/kg/min, according to SBP at 1-min intervals until delivery, aim to maintain values close to the baseline.MeasurementsDuring the study period, the incidence of maternal hypotension, hemodynamic performance, the number of physician interventions, reactive hypertension, bradycardia, nausea, vomiting, norepinephrine cumulative dose (before delivery), and neonatal outcomes were recorded.Main resultsThe incidence of maternal hypotension was significantly lower in Group V than that in Group F (9% versus 30%) (P < 0.001). No significant difference was found in the serial changes in SBP and heart rate (HR) for the first 15 min. Group V showed higher frequency of physician interventions compared with the Group F (P < 0.001). The incidence of hypertension, severe hypotension, nausea, vomiting, bradycardia, norepinephrine cumulative dose, and neonatal outcome were comparable between the two groups.ConclusionWhen norepinephrine was infused at an initial dose of 0.05 μg/kg/min for preventing hypotension during spinal anesthesia for cesarean delivery, due to technical limitations of inadequate dose design in this study, neither a variable-rate infusion (need more physician intervention) nor a fixed-rate infusion regimen (experience more transient hypotension) was optimal. However, in terms of clinical importance, how to prevent the parturients from experiencing more incidence of hypotension might be a greater concern for anesthesiologists.     

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.