Spinal versus epidural anesthesia for cesarean delivery in severe preeclampsia: a prospective randomized, multicenter study

In this randomized, multicenter study we compared the hemodynamic effects of spinal and epidural anesthesia for cesarean delivery in severely preeclamptic patients. The epidural group (n = 47) received 2% lidocaine with epinephrine 1:400,000, 18-23 mL, followed by 3 mg of morphine after delivery. The spinal group (n = 53) received 2.2 mL of 0.5% hyperbaric bupivacaine plus 0.2 mg morphine. We hypothesized that the lowest MAP (mean arterial blood pressure, the primary outcome) during the delivery period would have to be at least 10 mm Hg less in the spinal group to be of clinical importance. We found that there was a statistically significant difference in MAP, with more patients in the spinal group exhibiting hypotension (P < 0.001). Although the incidence of hypotension (systolic arterial blood pressure, SAP < or =100 mm Hg) was more frequent in the spinal group than in the epidural group (51% versus 23%), the duration of significant hypotension (SAP < or =100 mm Hg) was short (< or =1 min) in both groups. There was more use of ephedrine in the spinal group than in the epidural group (median, 6 versus 0 mg) but hypotension was easily treated in all patients. Neonatal outcomes assessed by Apgar scores and the umbilical arterial blood gas analysis were similar in both groups. Adverse neonatal outcomes (5-min Apgar score < 7 and umbilical arterial blood pH < 7.20) were found in only 2 premature newborns (weight < 1500 g) who were born without maternal hypotension after regional anesthesia. We conclude that the results of this large prospective study support the use of spinal anesthesia for cesarean delivery in severely preeclamptic patients.     

Evidence that intravenous vasopressors can affect rostral spread of spinal anesthesia in pregnancy

BACKGROUND: The authors have previously observed an apparent association between rostral spread of spinal anesthesia and choice of intravenous vasopressor given to maintain maternal systolic arterial pressure during cesarean delivery. This study tested the hypothesis that an intravenous infusion of phenylephrine can reduce rostral spread of spinal anesthesia in pregnancy, compared with ephedrine. METHODS: The study was randomized and double blind. It compared phenylephrine 100 microg/ml (phenylephrine group, n = 30), and ephedrine 3 mg/ml (ephedrine group, n = 30), given by infusion, to prevent maternal hypotension during combined spinal-epidural anesthesia for cesarean delivery. Two ml intrathecal plain levobupivacaine, 0.5%, combined with 0.4 ml intrathecal fentanyl, 50 microg/ml, and 10 ml epidural saline was given with the patient in the sitting position. The upper level of neural blockade to cold and light touch sensation was recorded at 10 and 20 min postspinal. Epidural space pressure was recorded at 5, 10, 15, and 20 min. RESULTS: At 20 min, the upper dermatome blocked to cold sensation was median T3 (interquartile range, T2-T4) for the phenylephrine group, compared with T1 (T1-T2) for the ephedrine group (P = 0.001). At 20 min, the upper dermatome blocked to light touch sensation was median T5 (T4-T8) for the phenylephrine group, compared with T3 (T2-T6) for the ephedrine group (P = 0.009). The mean epidural space pressure in the phenylephrine group was 16 (13-19) mmHg, compared with 16 (13-18) mmHg in the ephedrine group (P = 0.63). CONCLUSIONS: This study provides evidence that intravenous phenylephrine can decrease rostral spread of spinal anesthesia in pregnancy, compared with intravenous ephedrine. Further work is required to investigate possible mechanisms and to assess its clinical significance.     

Evidence That Intravenous Vasopressors Can Affect Rostral Spread of Spinal Anesthesia in Pregnancy

Background: The authors have previously observed an apparent association between rostral spread of spinal anesthesia and choice of intravenous vasopressor given to maintain maternal systolic arterial pressure during cesarean delivery. This study tested the hypothesis that an intravenous infusion of phenylephrine can reduce rostral spread of spinal anesthesia in pregnancy, compared with ephedrine.

Methods: The study was randomized and double blind. It compared phenylephrine 100 [mu]g/ml (phenylephrine group, n = 30), and ephedrine 3 mg/ml (ephedrine group, n = 30), given by infusion, to prevent maternal hypotension during combined spinal-epidural anesthesia for cesarean delivery. Two ml intrathecal plain levobupivacaine, 0.5%, combined with 0.4 ml intrathecal fentanyl, 50 [mu]g/ml, and 10 ml epidural saline was given with the patient in the sitting position. The upper level of neural blockade to cold and light touch sensation was recorded at 10 and 20 min postspinal. Epidural space pressure was recorded at 5, 10, 15, and 20 min.

Results: At 20 min, the upper dermatome blocked to cold sensation was median T3 (interquartile range, T2-T4) for the phenylephrine group, compared with T1 (T1-T2) for the ephedrine group (P = 0.001). At 20 min, the upper dermatome blocked to light touch sensation was median T5 (T4-T8) for the phenylephrine group, compared with T3 (T2-T6) for the ephedrine group (P = 0.009). The mean epidural space pressure in the phenylephrine group was 16 (13-19) mmHg, compared with 16 (13-18) mmHg in the ephedrine group (P = 0.63).     

Fetal and maternal effects of phenylephrine and ephedrine during spinal anesthesia for cesarean delivery

BACKGROUND: In our routine practice, we observed a reduced incidence of fetal acidosis (umbilical artery pH < 7.20) at cesarean delivery during spinal anesthesia when a combination of phenylephrine and ephedrine was used as first line vasopressor therapy, compared with using ephedrine alone. METHODS: The study was randomized and double blind. It compared phenylephrine 100 microg/ml (phenylephrine group), ephedrine 3 mg/ml (ephedrine group), and phenylephrine 50 microg/ml combined with ephedrine 1.5 mg/ml (combination group), given by infusion, to maintain maternal systolic arterial pressure at baseline during spinal anesthesia for elective cesarean delivery. RESULTS: Fetal acidosis was less frequent in the phenylephrine group (1 of 48) (P = 0.004) and less frequent in the combination group (1 of 47) (P = 0.005) than in the ephedrine group (10 of 48). The mean systolic arterial pressure was similar for the three groups: Phenylephrine group median 98% (IQR 94-103) of baseline, ephedrine group 100% (96-106) and combination group 101% (97-108) (P = 0.11). The mean heart rate was higher in the ephedrine group (median 107% [IQR 99-118] of baseline) than in the phenylephrine group (88% [82-98]) (P < 0.0001), or the combination group (96% [86-102]) (P < 0.0001). Nausea and vomiting were less frequent in the phenylephrine group (nausea 17%, vomiting 0%) than in the ephedrine group (nausea 66%, vomiting 36%) (P < 0.0001), or the combination group (nausea 55%, vomiting 18%) (P < 0.0001). CONCLUSIONS: Giving phenylephrine alone by infusion at cesarean delivery was associated with a lower incidence of fetal acidosis and maternal nausea and vomiting than giving ephedrine alone. There was no advantage to combining phenylephrine and ephedrine because it increased nausea and vomiting, and it did not further improve fetal blood gas values, compared with giving phenylephrine alone.     

脊麻下剖宫产术中去氧肾上腺素与麻黄素复合用药维持血压稳定对胎儿酸碱平衡和血流动力学影响的随机双盲对照研究

背景去氧肾上腺素和麻黄素都可用于脊麻下剖宫声术中的血压维持。通常情况下单独给予其中一种,但也有关于两者联合应用的研究。然而,应用不同比例组合血管升压药的效果尚未见报道。方法125例产妇拟在脊麻下实施择期刮宫产手术,随机接受5种不同浓度比例的去氧肾上腺素和麻黄素复合静脉给药。假设100μg去氧肾上腺素约等效于8mg麻黄素,各组比例分别相当于100％、75％、50％、25％、0％的去氧肾上腺素和0％、25％、50％、75％、100％的麻黄素。调节输注速率以维持收缩压（SBP）在基线水平直到子宫切开。对血流动力学变化和脐带血气进行分析比较。结果随着各组去氧肾上腺素的比例下降和麻黄素比例的上升,我们发现下列显著趋势：低血压和恶心,口区吐的发生率增加,收缩压高于或低于基线差值的中位数俐数增加,收缩压高于基线的偏侈量增加,产妇心率增快,胎儿pH值和碱剩余降低,脐动脉血氧含量下降,脐静脉氧分压增加。结论脊麻剖宫产术中,当去氧肾上腺素和麻黄素以不同配比复合输注以维持血压时,随着去氧肾上腺素比例下降和麻黄素比例上升,血流动力学的可控性减弱,对胎儿酸碱平衔状况不利。对于防治剖宫产过程中的脊麻相关低血压,去氧肾上腺素和麻黄素复合输注与单独应用去氧肾上腺素相比似乎没有优势．     

A dose-response study of prophylactic intravenous ephedrine for the prevention of hypotension during spinal anesthesia for cesarean delivery

We performed a randomized, double-blinded dose-finding study of IV ephedrine for prophylaxis for hypotension in 80 women who received an IV crystalloid preload and spinal anesthesia for elective cesarean delivery. One minute after the intrathecal injection, patients were given saline control or ephedrine 10, 20, or 30 mg IV for 30 s. Systolic arterial pressure (SAP) in the first 12 min after the spinal injection was greater in the 30-mg group compared with other groups (P < 0.05). Hypotension occurred in 7 patients (35%) in the 30-mg group compared with 19 (95%), 17 (85%), and 16 (80%) patients in the control and 10- and 20-mg groups, respectively (P < 0.0001). Maximum decrease in SAP was smaller in the 30-mg group (mean lowest SAP 87% of baseline, range 58%-105%) compared with other groups (P < 0.01). Reactive hypertension occurred in 9 patients (45%) in the 30-mg group (mean highest SAP 120% of baseline, range 104%-143%) compared with 2 (10%), 1 (5%), and 5 (25%) patients in the other groups (P = 0.009). Heart rate changes, total ephedrine requirement, incidence of nausea and vomiting, and neonatal outcome were similar among groups. The proportion of patients with umbilical arterial pH < 7.2 was 10.5%, 25%, 42%, and 22% in the control, 10-, 20-, and 30-mg groups, respectively (P = 0. 12). We conclude that the smallest effective dose of ephedrine to reduce the incidence of hypotension was 30 mg. However, this dose did not completely eliminate hypotension, nausea and vomiting, and fetal acidosis, and it caused reactive hypertension in some patients. Implications: We investigated different doses of IV ephedrine as prophylaxis for hypotension during spinal anesthesia for cesarean delivery and found that the smallest effective dose was 30 mg. However, this dose did not completely eliminate hypotension, caused reactive hypertension in some patients, and did not improve neonatal outcome.     

In nonhuman primates intracarotid adenosine, but not sodium nitroprusside, increases cerebral blood flow.

Intracarotid infusion of short-acting vasodilators, such as adenosine and nitroprusside, in doses that lack significant systemic side effects, may permit controlled manipulation of cerebrovascular resistance. In this experiment we assessed changes in cerebral blood flow (CBF) after intracarotid infusion of nitroprusside and adenosine. The study was conducted on six adult baboons under isoflurane anesthesia and controlled ventilation. Intracarotid drug infusion protocol avoided hypotension during nitroprusside infusion and tested for autoregulatory vasoconstriction. CBF (intraarterial (133)Xe technique) was measured four times during infusions of 1) intracarotid saline, 2) IV phenylephrine (0.2 microg x kg(-1) x min(-1)) aimed to increase mean arterial pressure by 10-15 mm Hg, 3) IV phenylephrine and intracarotid nitroprusside (0.5 microg x kg(-1) x min(-1)), and 4) intracarotid adenosine (1 mg/min). IV phenylephrine increased mean arterial pressure (69 +/- 8 to 91 +/- 9 mm Hg, P < 0.0001, n = 6), and concurrent infusion of intracarotid nitroprusside reversed this effect. However, compared with baseline, CBF did not change with IV phenylephrine or with concurrent infusion of IV phenylephrine and intracarotid nitroprusside. Intracarotid adenosine profoundly increased CBF (from 29 +/- 8 to 75 +/- 32 mL x 100 g(-1) x min(-1); P < 0.0001). In nonhuman primates, intracarotid adenosine increases CBF in doses that lack significant systemic side effects, whereas intracarotid nitroprusside has no effect. Intracarotid adenosine may be useful for manipulating cerebrovascular resistance and augmenting CBF during cerebral ischemia. IMPLICATIONS: Intraarterial (133)Xe cerebral blood flow (CBF) measurements suggest that intracarotid adenosine, in a dose that lacks significant systemic side effects, profoundly increases CBF, whereas nitroprusside has no effect.(5-12)     

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.     

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。     

Prevention of hypotension during spinal anesthesia for cesarean delivery: an effective technique using combination phenylephrine infusion and crystalloid cohydration

BACKGROUND: Many methods for preventing hypotension during spinal anesthesia for cesarean delivery have been investigated, but no single technique has proven to be effective and reliable. This randomized study studied the efficacy of combining simultaneous rapid crystalloid infusion (cohydration) with a high-dose phenylephrine infusion. METHODS: Nonlaboring patients scheduled to undergo elective cesarean delivery received an intravenous infusion of 100 mug/min phenylephrine that was started immediately after spinal injection and titrated to maintain systolic blood pressure near baseline values until uterine incision. In addition, patients received infusion of lactated Ringer's solution that was given either rapidly (group 1, n = 57) or at a minimal maintenance rate (group 0, n = 55). Maternal hemodynamic changes and neonatal condition were compared. RESULTS: Six patients were excluded from analysis. Only 1 of 53 patients (1.9% [95% confidence interval, 0.3-9.9%]) in group 1 experienced hypotension versus 15 of 53 patients (28.3% [95% confidence interval, 18.0-41.6%]) in group 0 (P = 0.0001). Compared with group 0, patients in group 1 had greater values for the following: serial measurements of systolic blood pressure (P = 0.02), minimum recorded systolic blood pressure (P = 0.0002), and minimum recorded heart rate (P = 0.013). Total phenylephrine consumption was smaller in group 1 compared with group 0 (P = 0.008). Neonatal outcome and maternal side effects were similar between groups. CONCLUSIONS: Combination of a high-dose phenylephrine infusion and rapid crystalloid cohydration is the first technique to be described that is effective for preventing hypotension during spinal anesthesia for cesarean delivery.     

Fetal and Maternal Effects of Phenylephrine and Ephedrine during Spinal Anesthesia for Cesarean Delivery

Background: In our routine practice, we observed a reduced incidence of fetal acidosis (umbilical artery p H < 7.20) at cesarean delivery during spinal anesthesia when a combination of phenylephrine and ephedrine was used as first line vasopressor therapy, compared with using ephedrine alone.

Methods: The study was randomized and double blind. It compared phenylephrine 100 [mu]g/ml (phenylephrine group), ephedrine 3 mg/ml (ephedrine group), and phenylephrine 50 [mu]g/ml combined with ephedrine 1.5 mg/ml (combination group), given by infusion, to maintain maternal systolic arterial pressure at baseline during spinal anesthesia for elective cesarean delivery.

Results: Fetal acidosis was less frequent in the phenylephrine group (1 of 48) (P = 0.004) and less frequent in the combination group (1 of 47) (P = 0.005) than in the ephedrine group (10 of 48). The mean systolic arterial pressure was similar for the three groups: Phenylephrine group median 98% (IQR 94-103) of baseline, ephedrine group 100% (96-106) and combination group 101% (97-108) (P = 0.11). The mean heart rate was higher in the ephedrine group (median 107% [IQR 99-118] of baseline) than in the phenylephrine group (88% [82-98]) (P < 0.0001), or the combination group (96% [86-102]) (P < 0.0001). Nausea and vomiting were less frequent in the phenylephrine group (nausea 17%, vomiting 0%) than in the ephedrine group (nausea 66%, vomiting 36%) (P < 0.0001), or the combination group (nausea 55%, vomiting 18%) (P < 0.0001).     

Comparison of metaraminol and ephedrine infusions for maintaining arterial pressure during spinal anesthesia for elective cesarean section

BACKGROUND: Although ephedrine is usually recommended as the first-line vasopressor in obstetrics, its superiority over other vasopressors has not been proven in humans. METHODS: In a double-blind study, the authors randomized women having elective cesarean section with spinal anesthesia to receive an intravenous infusion of ephedrine, starting at 5 mg/min (n = 25), or metaraminol, starting at 0.25 mg/min (n = 25), titrated to maintain systolic arterial pressure in the target range 90-100% of baseline. Umbilical cord gases, maternal hemodynamics, uterine artery puLsatility index, and Apgar scores were compared. RESULTS: Systolic arterial pressure was maintained more closely in the target range in the metaraminol group compared with the ephedrine group. In the metaraminol group, umbilical arterial pH was greater (median and interquartile range, 7.31 and 7.31-7.33 vs. 7.24 and 7.14-7.29; P < 0.0001), and umbilical venous pH was greater (7.36 and 7.35-7.38 vs. 7.33 and 7.26-7.34; P < 0.0001) compared with the ephedrine group. No patient in the metaraminol group had umbilical arterial pH less than 7.2, compared with nine patients (39%) in the ephedrine group (P = 0.0005). Apgar scores were similar between groups. Changes in uterine artery pulsatility index were similar between groups. CONCLUSIONS: When used by infusion to maintain arterial pressure during spinal anesthesia for cesarean section, metaraminol was associated with less neonatal acidosis and more closely controlled titration of arterial pressure compared with ephedrine.     

Effect of injection rate on hypotension associated with spinal anesthesia for cesarean section

Maternal hypotension is a common problem during cesarean section under spinal anesthesia. We evaluated in a prospective observational study the influence of injection speed on maternal hypotension. Hyperbaric bupivacaine 10 mg, sufentanil 2 microg and morphine 200 microg (total volume 4 mL) were injected either quickly (<15 s) or slowly (=120 s) in 50 women scheduled for elective cesarean section. Hypotension (systolic arterial pressure (SAP) <100 mmHg or <70% of baseline) was promptly treated with 5 mg ephedrine boluses. Slow injection significantly reduced the incidence of hypotension (68% in the 120 s group and 92% in the other, P =0.03). In addition, onset of hypotension was delayed, had a shorter duration and required less ephedrine for hypotension in the 120 s group (11.6 mg vs. 19.6 mg, P =0.019). Anesthesia was satisfactory for all women. We conclude that a 2 mL/min injection rate may be a simple and effective way to reduce the incidence and severity of hypotension during cesarean section under spinal anesthesia.     

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 during Spinal Anesthesia for Cesarean Delivery: An Effective Technique Using Combination Phenylephrine Infusion and Crystalloid Cohydration

Background: Many methods for preventing hypotension during spinal anesthesia for cesarean delivery have been investigated, but no single technique has proven to be effective and reliable. This randomized study studied the efficacy of combining simultaneous rapid crystalloid infusion (cohydration) with a high-dose phenylephrine infusion.

Methods: Nonlaboring patients scheduled to undergo elective cesarean delivery received an intravenous infusion of 100 [mu]g/min phenylephrine that was started immediately after spinal injection and titrated to maintain systolic blood pressure near baseline values until uterine incision. In addition, patients received infusion of lactated Ringer's solution that was given either rapidly (group 1, n = 57) or at a minimal maintenance rate (group 0, n = 55). Maternal hemodynamic changes and neonatal condition were compared.

Results: Six patients were excluded from analysis. Only 1 of 53 patients (1.9% [95% confidence interval, 0.3-9.9%]) in group 1 experienced hypotension versus 15 of 53 patients (28.3% [95% confidence interval, 18.0-41.6%]) in group 0 (P = 0.0001). Compared with group 0, patients in group 1 had greater values for the following: serial measurements of systolic blood pressure (P = 0.02), minimum recorded systolic blood pressure (P = 0.0002), and minimum recorded heart rate (P = 0.013). Total phenylephrine consumption was smaller in group 1 compared with group 0 (P = 0.008). Neonatal outcome and maternal side effects were similar between groups.     

Intrathecal versus intravenous fentanyl for supplementation of subarachnoid block during cesarean delivery

Forty-eight healthy parturients scheduled for elective cesarean delivery were randomly allocated to receive intrathecally either 12 mg of hyperbaric bupivacaine plus 12.5 microg of fentanyl (n = 23) or bupivacaine alone (n = 25). In the latter group, IV 12.5 microg of fentanyl was administered immediately after spinal anesthesia. We compared the amount of IV fentanyl required for supplementation of the spinal anesthesia during surgery, the intraoperative visual analog scale, the time to the first request for postoperative analgesia, and the incidence of adverse effects. Additional IV fentanyl supplementation amounting to a mean of 32 +/- 35 microg was required in the IV Fentanyl group, whereas no supple- mentation was required in the Intrathecal Fentanyl group (P = 0.009). The time to the first request for postoperative analgesia was significantly longer in the Intrathecal Fentanyl group than in the IV Fentanyl group (159 +/- 39 min versus 119 +/- 44 min; P = 0.003). The incidence of systolic blood pressure <90 mm Hg and the ephedrine requirements were significantly higher in the IV Fentanyl group as compared with the Intrathecal Fentanyl group (P = 0.01). Also, intraoperative nausea and vomiting occurred less frequently in the Intrathecal Fentanyl group compared with the IV Fentanyl group (8 of 23 vs 17 of 25; P = 0.02). IMPLICATIONS: Supplementation of spinal bupivacaine anesthesia for cesarean delivery with intrathecal fentanyl provides a better quality of anesthesia and is associated with a decreased incidence of side effects as compared with supplementation with the same dose of IV fentanyl.     

Low-dose bupivacaine-fentanyl spinal anesthesia for cesarean delivery

BACKGROUND AND OBJECTIVES: The hypotension following spinal anesthesia remains commonplace in cesarean delivery. Intrathecal opioids are synergistic with local anesthetics and intensify sensory block without increasing sympathetic block. The combination makes it possible to achieve spinal anesthesia with otherwise inadequate doses of local anesthetic. We hypothesized that this phenomenon could be used to provide spinal anesthesia for cesarean delivery while incurring less frequent hypotension. METHODS: Thirty-two women scheduled for cesarean delivery were divided into 2 groups of patients who received a spinal injection of either 10 mg of isobaric (plain) bupivacaine 0.5% or 5 mg of isobaric bupivacaine with 25 microg fentanyl added. Each measurement of a systolic blood pressure less than 95 mm Hg or a decrease in systolic pressure of greater than 25% from baseline was considered as hypotension and treated with a bolus of 5 to 10 mg of intravenous ephedrine. RESULTS: Spinal block provided surgical anesthesia in all patients. Peak sensory level was higher (T3 v T4. 5) and motor block more intense in the plain bupivacaine group. The plain bupivacaine patients were more likely to require treatment for hypotension (94% v 31%) and had more persistent hypotension (4.8 v 0.6 hypotensive measurements per patient) than patients in the minidose bupivacaine-fentanyl group. Mean ephedrine requirements were 23.8 mg and 2.8 mg, respectively, for the 2 groups. Patients in the plain bupivacaine group also complained of nausea more frequently than patients in the minidose bupivacaine-fentanyl group (69% v 31%). CONCLUSIONS: Bupivacaine 5 mg + fentanyl 25 microg provided spinal anesthesia for cesarean delivery with less hypotension, vasopressor requirements, and nausea than spinal anesthesia with 10 mg bupivacaine.     

Hemodynamic effects of spinal anesthesia and simultaneous intravenous bolus of combined phenylephrine and ephedrine versus ephedrine for cesarean delivery

BACKGROUND: Hypotension following spinal anesthesia for cesarean delivery can produce adverse maternal symptoms and neonatal acid-base effects. Single-agent prophylaxis, most notably with ephedrine, does not reliably prevent spinal anesthesia-induced hypotension; recently, however, the prophylactic use of phenylephrine with ephedrine as an infusion was observed to be effective. We postulated that this combination, when given as an intravenous bolus for prophylaxis and rescue treatment, could be similarly effective. METHOD: Forty-three term parturients were randomized to receive a bolus of ephedrine 10 mg +/- phenylephrine 40 microg (groups E and EP, respectively) simultaneously with spinal anesthesia. Hypotension was defined as a systolic blood pressure below 100 mmHg or a decrease of 20% from a baseline value. Rescue boluses comprised of ephedrine 5 mg +/- phenylephrine 20 microg. RESULTS: For groups E and EP, respectively, the incidence of hypotension was 80% vs. 95% (P=0.339), with the mean number of rescue boluses being 3.85+/-3.7 and 3.05+/-1.7 and the mean umbilical artery pH being 7.246+/-0.081 vs. 7.244+/-0.106. All comparisons were not significant (NS). CONCLUSION: The combination of ephedrine and phenylephrine given as an intravenous bolus at the doses selected is not superior to ephedrine alone in preventing or treating hypotension in healthy parturients undergoing cesarean delivery.     

A quantitative, systematic review of randomized controlled trials of ephedrine versus phenylephrine for the management of hypotension during spinal anesthesia for cesarean delivery

This quantitative systematic review compared the efficacy and safety of ephedrine with phenylephrine for the prevention and treatment of hypotension during spinal anesthesia for cesarean delivery. Seven randomized controlled trials (n = 292) were identified after a systematic search of electronic databases (MEDLINE, EMBASE, The Cochrane Controlled Trials Registry), published articles, and contact with authors. Outcomes assessed were maternal hypotension, hypertension and bradycardia, and neonatal umbilical cord blood pH values and Apgar scores. For the management (prevention and treatment) of maternal hypotension, there was no difference between phenylephrine and ephedrine (relative risk [RR] of 1.00; 95% confidence interval [CI], 0.96-1.06). Maternal bradycardia was more likely to occur with phenylephrine than with ephedrine (RR of 4.79; 95% CI, 1.47-15.60). Women given phenylephrine had neonates with higher umbilical arterial pH values than those given ephedrine (weighted mean difference of 0.03; 95% CI, 0.02-0.04). There was no difference between the two vasopressors in the incidence of true fetal acidosis (umbilical arterial pH value of <7.2; RR of 0.78; 95% CI, 0.16-3.92) or Apgar score of <7 at 1 and 5 min. This systematic review does not support the traditional idea that ephedrine is the preferred choice for the management of maternal hypotension during spinal anesthesia for elective cesarean delivery in healthy, nonlaboring women. IMPLICATIONS: Phenylephrine and ephedrine to manage hypotension during spinal anesthesia for elective cesarean delivery were compared in this systematic review. Women given ephedrine had neonates with lower umbilical cord blood pH values compared with those given phenylephrine. However, no differences in the incidence of fetal acidosis (pH value of <7.2) or neonatal Apgar scores were found.     

Comparison of Metaraminol and Ephedrine Infusions for Maintaining Arterial Pressure during Spinal Anesthesia for Elective Cesarean Section

Background: Although ephedrine is usually recommended as the first-line vasopressor in obstetrics, its superiority over other vasopressors has not been proven in humans.

Methods: In a double-blind study, the authors randomized women having elective cesarean section with spinal anesthesia to receive an intravenous infusion of ephedrine, starting at 5 mg/min (n = 25), or metaraminol, starting at 0.25 mg/min (n = 25), titrated to maintain systolic arterial pressure in the target range 90-100% of baseline. Umbilical cord gases, maternal hemodynamics, uterine artery pulsatility index, and Apgar scores were compared.

Results: Systolic arterial pressure was maintained more closely in the target range in the metaraminol group compared with the ephedrine group. In the metaraminol group, umbilical arterial p H was greater (median and interquartile range, 7.31 and 7.31-7.33 vs. 7.24 and 7.14-7.29;P < 0.0001), and umbilical venous p H was greater (7.36 and 7.35-7.38 vs. 7.33 and 7.26-7.34;P < 0.0001) compared with the ephedrine group. No patient in the metaraminol group had umbilical arterial p H less than 7.2, compared with nine patients (39%) in the ephedrine group (P = 0.0005). Apgar scores were similar between groups. Changes in uterine artery pulsatility index were similar between groups.