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.     

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.     

Metaraminol infusion for maintenance of arterial blood pressure during spinal anesthesia for cesarean delivery: the effect of a crystalloid bolus

We randomly allocated women having elective cesarean delivery to receive either no bolus (Control Group, n = 31) or 20 mL/kg lactated Ringer's solution (Bolus Group, n = 35) IV before spinal anesthesia. An infusion of metaraminol started at 0.25 mg/min was titrated to maintain systolic arterial blood pressure in the target range 90%-100% of baseline. The total dose of metaraminol required up to the time of uterine incision was similar between the Control Group and the Bolus Group (3.62 +/- 1.20 vs 3.27 +/- 1.39 mg, P = 0.3). However, the Control Group required more metaraminol in the first 5 min (1.29 +/- 0.60 vs 0.96 +/- 0.58 mg, P = 0.025) and a faster maximum infusion rate (0.45 +/- 0.20 vs 0.32 +/- 0.13 mg/min, P = 0.002) compared with the Bolus Group. There was no difference between groups in regards to changes in systolic arterial blood pressure or heart rate over time, or maternal or neonatal outcome. We conclude that when metaraminol is used to maintain arterial pressure during spinal anesthesia for cesarean delivery, crystalloid bolus is not essential provided that sufficient vasopressor is given in the immediate postspinal period.     

An open-label randomized controlled clinical trial for comparison of continuous phenylephrine versus norepinephrine infusion in prevention of spinal hypotension during cesarean delivery

BackgroundDuring spinal anesthesia for cesarean delivery phenylephrine is the vasopressor of choice but can cause bradycardia. Norepinephrine has both β- and α-adrenergic activity suitable for maintaining blood pressure with less bradycardia. We hypothesized that norepinephrine would be superior to phenylephrine, requiring fewer rescue bolus interventions to maintain blood pressure.MethodsEighty-five parturients having spinal anesthesia for elective cesarean delivery were randomized to Group P (phenylephrine 0.1 μg/kg/min) or Group N (norepinephrine 0.05 μg/kg/min) fixed-rate infusions. Rescue bolus interventions of phenylephrine 100 μg for hypotension, or ephedrine 5 mg for bradycardia with hypotension, were given as required to maintain systolic blood pressure. Maternal hemodynamic variables were measured non-invasively.ResultsThere was no difference between groups in the proportion of patients who required rescue vasopressor boluses (Group P: 65.8% [n=25] vs. Group N: 48.8% [n=21], P=0.12). The proportion of patients who received ⩾1 bolus of phenylephrine was similar between groups (Group P: 52.6% [n=20] vs. Group N: 46.5% [n=20], P=0.58). However, more patients received ⩾1 bolus of ephedrine in the phenylephrine group (Group P: 23.7% [n=9] vs. Group N: 2.3% [n=1], P <0.01). The incidence of emesis was greater in the phenylephrine group (Group P: 26.3% vs. Group P: 16.3%, P <0.001). Hemodynamic parameters including heart rate, the incidence of bradycardia, blood pressure, cardiac output, cardiac index, stroke volume, and systemic vascular resistance and neonatal outcome were similar between groups (all P <0.05).ConclusionNorepinephrine fixed-rate infusion has efficacy for preventing hypotension and can be considered as an alternative to phenylephrine.     

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.     

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．     

去氧肾上腺素对蛛网膜下隙麻醉剖宫产产妇血流动力学和母婴预后的影响

去氧肾上腺素针对于剖宫产产妇因蛛网膜下隙麻醉引起的低血压具有良好效果。过去麻黄素被认为是产科患者首选的升压药,但现在去氧肾上腺素得到越来越广泛的应用,主要是因为研究表明注射去氧肾上腺素能改善胎儿的酸碱状态,预防性使用去氧肾上腺素能减少低血压的发生率及相关副作用。本篇综述针对麻黄素与去氧肾上腺素对产妇血流动力学（动脉血压、心率和心排血量）及术中恶心和呕吐的影响加以较,同时比较了去氧肾上腺素治疗性单剂给药与预防性输注对低血压的疗效,还评价了与麻黄素相比,去氧肾上腺素对子宫胎盘血流灌注以及胎儿预后（如新生儿酸碱状态和Apgar评分）的影响,还对去氧肾上腺素的最佳给药方案进行了讨论。     

A review of the impact of phenylephrine administration on maternal hemodynamics and maternal and neonatal outcomes in women undergoing cesarean delivery under spinal anesthesia

Phenylephrine is effective for the management of spinal anesthesia-induced hypotension in parturients undergoing cesarean delivery under spinal anesthesia. While ephedrine was previously considered the vasopressor of choice in obstetric patients, phenylephrine is increasingly being used. This is largely due to studies suggesting improved fetal acid-base status with the use of phenylephrine as well as the low incidence of hypotension and its related side effects with prophylactic phenylephrine regimens. This review highlights the effects of phenylephrine compared with ephedrine on maternal hemodynamics (arterial blood pressure, heart rate, and cardiac output), and occurrence of intraoperative nausea and vomiting. The impact of the administration of phenylephrine as a bolus for the treatment of established hypotension compared with its administration as a prophylactic infusion is discussed. This article also reviews the impact of phenylephrine compared with ephedrine on uteroplacental perfusion, and fetal outcomes such as neonatal acid-base status and Apgar scores. The optimum dosing regimen for phenylephrine administration is also discussed.     

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.     

Closed‐loop double‐vasopressor automated system to treat hypotension during spinal anaesthesia for caesarean section: a preliminary study

Hypotension occurs in most caesarean sections under spinal anaesthesia, necessitating vasopressor administration. However, the optimal dosing regimen remains unclear. We have developed a novel vasopressor delivery system that automatically administers phenylephrine or ephedrine based on continuous non‐invasive blood pressure monitoring. This prospective cohort study recruited 55 healthy women under standardised spinal anaesthesia with 2.2 ml hyperbaric bupivacaine 0.5%, 15 μg fentanyl and 100 μg morphine. A 50‐μg phenylephrine bolus was given at 1‐min intervals when systolic blood pressure fell below 90% of baseline, and a 4‐mg ephedrine bolus was given when hypotension developed with bradycardia (heart rate <60 beats.min^?1). Systolic blood pressure was within 20% of baseline in 88% of all measurements. Six patients (11%) had one or more measurements above 120% of baseline (1% of all measurements), whereas 36 (65%) had at least one reading below 80% of baseline (11% of total measurements). The system maintained systolic blood pressure at a mean (SD) of ?9.1 (7.0)% below baseline, with 5.4 (2.5)% fluctuation. Two patients (4%) experienced pre‐delivery nausea. All 5‐min Apgar scores were 9.     

Prophylactic Angiotensin II Infusion during Spinal Anesthesia for Elective Cesarean Delivery

Background: Angiotensin II may prove useful in treating regional anesthesia-induced hypotension in obstetric patients, because it causes less uterine vasoconstriction than do other vasoconstrictor drugs (such as phenylephrine). This study compared (1) maternal blood pressure and heart rate and (2) fetal status at delivery in parturients given either prophylactic angiotensin II or ephedrine infusion during spinal anesthesia for elective cesarean delivery.

Methods: Fifty-four women were randomized to receive either angiotensin II or ephedrine infusion intravenously during spinal anesthesia for elective cesarean section delivery. Simultaneous with subarachnoid injection, infusion of angiotensin II (2.5 [micro sign]g/ml) or ephedrine (5 mg/ml) was initiated at 10 ng [middle dot] kg-1 [middle dot] min-1 and 50 [micro sign]g [middle dot] kg-1 [middle dot] min-1, respectively. The rate of each infusion was adjusted to maintain maternal systolic blood pressure at 90-100% of baseline.

Results: Cumulative vasopressor doses (mean +/- SD) through 10, 20, and 30 min were 150 +/- 100, 310 +/- 180, and 500 +/- 320 ng/kg in the angiotensin group and 480 +/- 210, 660 +/- 390, and 790 +/- 640 [micro sign]g/kg in the ephedrine group. Maternal heart rate was significantly higher (P < 0.001) during vasopressor infusion in the ephedrine group than in the angiotensin group. Umbilical arterial and venous blood pH and base excess were all significantly higher (P < 0.05) in the angiotensin group than in the ephedrine group.     

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).     

Ephedrine vs. phenylephrine by intravenous bolus and continuous infusion to prevent hypotension secondary to spinal anesthesia during cesarean section: a randomized comparative trial

ObjectiveSubarachnoid spinal anesthesia for cesarean section is associated with a high incidence of hypotension, which can require the use of vasoconstrictors. The aim of this trial was to compare ephedrine to phenylephrine for the prevention of secondary hypotension and to assess the adverse effects on both mother and newborn.Material and methodsEighty patients undergoing elective or emergency cesarean section, in the absence of uterine activity or fetal risk, were randomized to receive prophylaxis with ephedrine or phenylephrine immediately after the spinal block. Patients in the ephedrine group received an intravenous bolus of 0.1 mg/kg plus continuous infusion at a rate of 0.5 mg/kg/h; patients in the phenylephrine group received an intravenous bolus of 1.5 µg/kg plus a continuous infusion at 1.5 µg/kg/min. Infusion was maintained until umbilical cord clamping. We recorded maternal blood pressure, heart rate, nausea and vomiting, dizziness, bradycardia, hypotension, hypertension, fetal Apgar index, and umbilical cord blood parameters (pH, PCO₂, and HCO₃).ResultsThe overall incidence of hypotension was 11.2%, with no significant between-group differences (ephedrine group, 11.4%; phenylephrine group, 11.1%). The incidences of hypertension and bradycardia were higher in the phenylephrine group (27.8% and 2.3%, respectively) than in the ephedrine group (25% and 0%, respectively). Umbilical cord blood parameters and Apgar scores were similar. After suspension of continuous infusion, an episode of hypotension was detected in 22.5% of the patients (72.2% of these patients were in the phenylephrine group and 27.8% were in the ephedrine group).ConclusionsAt the doses of ephedrine and phenylephrine administered in this trial, the ability of these drugs to prevent hypotension during cesarean section proved to be similar. Higher incidences of adverse events (hypertension and bradycardia) were observed in the phenylephrine group. No differences were observed in neonatal effects.     

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.     

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.     

Incidence of bradycardia during noradrenaline or phenylephrine bolus treatment of postspinal hypotension in cesarean delivery: A randomized double-blinded controlled trial

The treatment of choice for spinal anesthesia-induced hypotension during cesarean section is phenylephrine. As this vasopressor can cause reflex bradycardia, noradrenaline is a suggested alternative. This randomized double-blinded controlled trial included 76 parturients undergoing elective cesarean delivery under spinal anesthesia. Women received noradrenaline in bolus doses of 5 mcg or phenylephrine in bolus doses of 100 mcg. These drugs were used intermittently and therapeutically to maintain systolic blood pressure ≥ 90% of its baseline value. The primary study outcome was bradycardia incidence (<60 bpm) with intermittent bolus administration of these drugs. Secondary outcomes included extreme bradycardia (<40 bpm), number of bradycardia episodes, hypertension (systolic blood pressure > 120% of baseline value), and hypotension (systolic blood pressure < 90% of baseline value and requiring vasopressor use). Neonatal outcomes per the Apgar scale and umbilical cord blood gas analysis were also compared. The incidence of bradycardia in both groups (51.4% and 70.3%, respectively; p = 0.16) were not significantly different. No neonates had umbilical vein or artery pH values below 7.20. The noradrenaline group required more boluses than phenylephrine group (8 vs. 5; p = 0.01). There was no significant intergroup difference in any of the other secondary outcomes. When administered in intermittent bolus doses for the treatment of postspinal hypotension in elective cesarean delivery, noradrenaline, and phenylephrine have a similar incidence of bradycardia. When treating hypotension related to spinal anesthesia in obstetric cases, strong vasopressors are commonly administered, thought these can also have side effects. This trial assessed bradycardia after bolus administration of noradrenaline or phenylephrine, and found no difference in risk for clinically meaningful bradycardia.     

O efeito de epinefrina,norepinefrina e fenilefrina no tratamento da hipotensão pós‐raquianestesia: estudo clínico comparativo

Background and objectivesLimited data are present on safety and efficiency of epinephrine for the prophylaxis and treatment of spinal‐hypotension. This study was conducted to compare the effect of epinephrine with norepinephrine and phenylephrine on the treatment of spinal‐hypotension and ephedrine requirement during cesarean delivery.MethodsOne hundred and sixty parturients with uncomplicated pregnancies undergoing elective cesarean delivery under spinal anesthesia were recruited. They were allocated randomly to receive norepinephrine 5 μg.mL^‐1 (n = 40), epinephrine 5 μg.mL^‐1 (n = 40), phenylephrine 100 μg.mL^‐1 (n = 40) or 0.9% saline infusions (n = 40) immediately after induction of spinal anesthesia. Whenever systolic blood pressure drops to less than 80% of baseline, 5 mg of iv ephedrine was administered as rescue vasopressor. The incidence of hypotension, total number of hypotension episodes, the number of patients requiring ephedrine, the mean amount of ephedrine consumption and side effects were recorded.ResultsThere was no statistically significant difference in incidence of maternal hypotension between groups. The number of patients requiring ephedrine was significantly greater in group saline than in group phenylephrine (p < 0.001). However, it was similar between phenylephrine, norepinephrine, and epinephrine groups. The mean ephedrine consumption was significantly higher in group saline than in norepinephrine, epinephrine, phenylephrine groups (p = 0.001).ConclusionThere is no statistically significant difference in incidence of hypotension and ephedrine consumption during spinal anesthesia for cesarean delivery with the use of epinephrine when compared to norepinephrine or phenylephrine. Epinephrine can be considered as an alternative agent for management of spinal hypotension.     

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.     

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 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.