Effect of low dose phenylephrine infusion on shivering and hypothermia in patients undergoing cesarean section under spinal anesthesia: a randomized clinical trial

BackgroundShivering is a common complication of spinal anesthesia. Phenylephrine, due to its peripheral vasoconstrictive effect, may limit the core to periphery redistribution of body temperature following spinal anesthesia, and reduce hypothermia and shivering. We hypothesized that prophylactic phenylephrine infusion would reduce shivering and hypothermia in women undergoing cesarean section under spinal anesthesia.MethodsA two-arm randomized, double-blind, placebo-controlled trial in term pregnant patients undergoing cesarean section. In the phenylephrine group (n=75) prophylactic phenylephrine infusion was administered at 25 µg/min immediately after initiation of spinal anesthesia and continued until the end of the operative period. In the placebo group (n=75) a normal saline infusion was administered during the same period. The primary outcome was the incidence of shivering; secondary outcomes were severity of shivering, changes in nasopharyngeal (core) temperature, and incidence of hypotension and bradycardia.ResultsThe incidence of shivering in the phenylephrine and control groups was 24.0% (95% CI 14.3% to 33.7%) and 53.3% (95% CI 42.0% to 64.6%), respectively. The severity of shivering was greater in the control group (P=0.002) and the mean (±SD) end of surgery core temperature was significantly higher in the phenylephrine group (35.84°C ± 0.60) compared with controls (35.61°C ± 0.48) (P=0.009). The incidence of hypotension was higher in controls (53.4% vs. 2.7%; P <0.001) but bradycardia more frequent in group P (P=0.023).ConclusionThe incidence of shivering and degree of hypothermia were significantly reduced by a prophylactic phenylephrine infusion during cesarean section under spinal anesthesia.     

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.     

A prospective observational study of the change in regional cerebral oxygen saturation during cesarean delivery in women receiving phenylephrine prophylaxis for spinal hypotension

BackgroundSpinal hypotension causes decreased regional cerebral oxygen saturation (ScO₂) in women undergoing cesarean delivery. In this study we aimed to measure the change in ScO₂ using near infrared spectroscopy in women receiving a prophylactic phenylephrine infusion during cesarean delivery under spinal anesthesia.MethodsThis was a prospective, observational cohort study. Fifty-three women had ScO₂ measurements at the following time points: preoperatively, in the supine position with 30° of left lateral tilt; one and five minutes after spinal anesthesia; at the time of skin incision; immediately after delivery; one minute after commencing the oxytocin infusion; at completion of surgery, and one hour after surgery. Spinal anesthesia and a prophylactic phenylephrine infusion were administered according to a standard treatment protocol. Statistical analysis used the Wilcoxon Signed Rank test with Bonferroni’s correction for multiple comparisons.ResultsBlood pressure was maintained within 20% of baseline throughout surgery. The baseline mean (range) ScO₂ was 61.5% (54.0–66.3%). It decreased significantly at all subsequent measurement points. The maximum decrease was five minutes after spinal anesthesia. Thirty-four (64.2%) of the parturients exhibited ScO₂ values <20% of baseline, or a decrease to below an absolute value of 50%. There was no significant correlation between systolic blood pressure and mean ScO₂.ConclusionSpinal anesthesia with phenylephrine infusion during cesarean delivery is associated with a significant decrease in ScO₂ levels, maximal five minutes later. Further studies are required to establish the clinical significance of this finding.     

Relationship between regional cerebral blood volume and oxygenation and blood pressure during spinal anesthesia in women undergoing cesarean section

Purpose

During spinal anesthesia for cesarean section, cerebral oxygenation decreases may be related to an abrupt drop in cerebral blood flow due to hypotension. We measured the changes in maternal regional cerebral blood volume (rCBV) and oxygenation (rCBO) using near-infrared spectroscopy (NIRS) to evaluate whether a decrease in arterial blood pressure during spinal anesthesia diminishes rCBV and rCBO.

Methods

Forty patients scheduled for elective cesarean section under spinal anesthesia were monitored for mean arterial pressure (MAP), heart rate (HR), respiratory rate (RR), and concentrations of oxy-hemoglobin (Hb), deoxy-Hb, total-Hb, and tissue oxygenation index (TOI), before spinal anesthesia (baseline) and for 20 min after intrathecal injection of bupivacaine. We investigated changes in the values from baseline and evaluated whether the maximum changes in total-Hb (Δ-total-Hb) and TOI (Δ-TOI) correlate with changes in MAP at the same time point.

Results

The mean oxy-Hb, total-Hb, TOI, and MAP significantly decreased from baseline after intrathecal injection of bupivacaine (P < 0.01). There were significant positive correlations between both Δ-total-Hb and Δ-TOI and the decrease in MAP (Δ-total-Hb: r = 0.53, P < 0.01; Δ-TOI: r = 0.59, P < 0.01).

Conclusions

Maternal rCBV and rCBO decrease significantly during spinal anesthesia for cesarean section. Reductions in rCBV and rCBO may be associated with the severity of hypotension induced by subarachnoid sympathetic block with bupivacaine.

     

The effects of prophylactic bolus phenylephrine on hypotension during low-dose spinal anesthesia for cesarean section

BackgroundContinuously infused phenylephrine is frequently used to reduce the incidence of hypotension in women undergoing cesarean section under spinal anesthesia, but less is known about the prophylactic bolus method. We evaluated three prophylactic bolus doses of phenylephrine during low-dose spinal anesthesia for cesarean section.MethodsOne-hundred-and-eighty-four patients were randomized to receive 0.9% saline 2 mL (Control Group) or phenylephrine 1.0 μg/kg (PHE1 Group), 1.5 μg/kg (PHE1.5 Group), or 2.0 μg/kg (PHE2 Group) immediately after induction of combined spinal-epidural anesthesia. Maternal blood pressure and heart rate were recorded at 1-min intervals until delivery. Hypotension, defined as systolic blood pressure <80% of baseline, was treated with rescue doses of phenylephrine 100 μg at 1-min intervals until hypotension resolved. The incidence of nausea, vomiting, bradycardia, and hypertension, as well as Apgar scores and umbilical blood gases, were recorded.ResultsThe incidence of hypotension was 71.7% (33/46) in the Control Group, 68.9% (31/45) in the PHE1 Group, 37.0% (17/46) in the PHE1.5 Group and 45.7% (21/46) in the PHE2 Group (P=0.001). The total rescue dose of phenylephrine was greater in the Control Group than those in the PHE1.5 Group (P <0.05) and PHE2 Group (P <0.05). The incidence of hypertension increased as the dose of prophylactic phenylephrine increased (P <0.001) and was highest in the PHE2 group (37%). Other variables did not differ among the four groups.ConclusionsUnder the conditions of this study, prophylactic bolus injection of phenylephrine 1.5 μg/kg was a suitable alternative method for reducing the incidence of hypotension during low-dose spinal anesthesia for cesarean section.     

Colloid coload versus crystalloid coload to prevent maternal hypotension in women receiving prophylactic phenylephrine infusion during caesarean delivery: a randomised controlled trial

BackgroundThe optimal fluid strategy to prevent maternal hypotension during caesarean delivery remains unclear. This study aim was to compare the incidence of post-spinal anaesthesia hypotension in women receiving either colloid or crystalloid coload in the setting of prophylactic phenylephrine infusion during caesarean delivery.MethodsHealthy mothers undergoing elective caesarean delivery under spinal anaesthesia were randomised to receive a rapid intravenous coload with 6% hydroxyethyl starch 130/0.4 10 mL/kg (colloid group) or balanced crystalloid solution (Plasma Solution A) 10 mL/kg (crystalloid group) during spinal anaesthesia. All women had a prophylactic phenylephrine infusion initiated at 25 μg/min immediately after the subarachnoid block and titrated to systolic blood pressure using a standardised protocol. The primary outcome was the incidence of hypotension (systolic blood pressure <80% of baseline) until delivery.ResultsThe incidence of hypotension was 50% in the colloid group and 62% in the crystalloid group (absolute difference, −12% [95% CI −33% to 9%]; relative risk, 0.8 [95% CI 0.56 to 1.14]; P=0.314). No significant difference between groups was found in the number of hypotensive episodes (median 0.5 [IQR 0 to 1] vs 1 [0 to 2], P=0.132) or phenylephrine dose (675 [IQR 425 to 975] μg vs 750 [625 to 950] μg, P=0.109). The incidence of severe hypotension, symptomatic hypotension, bradycardia, nausea, and the neonatal outcomes were not significantly different.ConclusionsThis study found no benefit of colloid coload compared with crystalloid coload for preventing maternal hypotension in the presence of prophylactic phenylephrine infusion during caesarean delivery.     

Cesarean under general or epidural anesthesia: Does it differ in terms of regional cerebral oxygenation?

ObjectiveIt is aimed to evaluate whether there is a difference in regional cerebral saturation of newborns measured by near infrared spectroscopy born either by general anesthesia or combined spinal epidural anesthesia during elective cesarean deliveries.MethodsAfter approval from the ethics committee of our hospital, and informed consents of the parturients were taken, 68 patients were included in the study. The regional cerebral oxygen saturations (RcSO2) of newborns were measured by near infrared spectroscopy (NIRS) measurements at 1st, 5th min after birth. In group I (n=32), general anesthesia was performed for the cesarean operation and in group II (n=36), combined spinal epidural anesthesia (CSEA) was the anesthetic management. The age of the mother, gestation, the problems related to the pregnancy, heart rate, blood pressure, oxygen saturation (SpO2) of the mother had been recorded. The measurements of the newborn were; SpO2 of right hand, RcSO2 measured by NIRS, the delivery time (from incision to the cessation of circulation in the placental cord), Apgar score. Data were analyzed using GraphPad Prism 5.0 (GraphPad Software, La Jolla, California) and presented as mean +/− SD. Results obtained in different groups were compared using upaired t-test. Differences were statistically significant at p < 0.05.ResultsThere were no significant differences between the groups related to the mother's age, gestation week and baseline blood pressure. Both the systolic and diastolic blood pressures measured at 1st and 5th min after induction or start of the spinal block were significantly lower in the mothers who had undergone combined spinal epidural anesthesia. The heart rates of the mothers who had been under CSEA were significantly higher than the general anesthesia group. The Apgar at the 1st min were observed significantly higher in Group II. Oxygen saturation of the newborns were significantly higher in Group II. Regional cerebral oxygenation measured by NIRS were significantly higher in CSEA group.ConclusionCombined spinal epidural anesthesia, besides other known advantages, had been shown to be superior to general anesthesia as a means of regional cerebral oxygenation of the newborns.     

Role of pleth variability index for predicting hypotension after spinal anesthesia for cesarean section

BackgroundHypotension is frequently observed after spinal anesthesia for cesarean section and can be detrimental to both mother and baby. We investigated the role of the pleth variability index for predicting hypotension after spinal anesthesia for cesarean section.MethodsEighty-five parturients undergoing elective cesarean section under spinal anesthesia were enrolled. We recorded pleth variability index and perfusion index before anesthesia, and blood pressure, heart rate and pulse oxygen saturation before and after anesthesia. The association between baseline pleth variability index and perfusion index with hypotension after spinal anesthesia was explored using multivariate analysis.ResultsHypotension occurred in 42 parturients. Baseline pleth variability index was higher in parturients who experienced hypotension than in those who did not (P < 0.05), although there was no difference in baseline perfusion index. The area under the receiver operating characteristic curve was 0.66 for baseline pleth variability index for the prediction of hypotension (P < 0.05). Baseline pleth variability index was significantly related to the incidence of hypotension (P = 0.017), but was not significantly related to the magnitude of the decrease in systolic blood pressure. Baseline perfusion index was not significantly related to the magnitude of the decrease in systolic blood pressure.ConclusionGreater baseline pleth variability index was associated with hypotension after spinal anesthesia for cesarean section, but may not be a clinically useful predictor.     

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.     

Anesthetic technique for cesarean delivery and neonatal acid–base status: a retrospective database analysis

IntroductionA previous meta-analysis reported lower umbilical artery pH with spinal anesthesia for cesarean delivery compared to general or epidural anesthesia. Ephedrine was used in the majority of studies. The objective of this study was to evaluate the effect of anesthetic technique on neonatal acid–base status now that phenylephrine has replaced ephedrine in our institution.MethodsWe retrospectively reviewed our database to identify patients who underwent cesarean delivery and had umbilical artery pH available. We decided a priori to test separately cases where cesarean delivery was performed emergently (category I and II) or non-emergently (category III and IV). Multivariable models were constructed to detect significant predictors of lower umbilical artery pH.ResultsOne thousand sixty-four cases were included (647 emergent, 417 non emergent). In emergent cesarean delivery, anesthesia type was a significant predictor of lower umbilical artery pH (P <0.0001) with the pairwise comparisons showing lower neonatal umbilical artery pH [mean (95% CI)] with general anesthesia [7.16 (7.13, 7.19)] compared with spinal anesthesia [7.24 (7.22, 7.25)] and epidural anesthesia [7.23 (7.21, 7.24)], with no difference between spinal and epidural anesthesia. When excluding cases where general anesthesia was chosen due to insufficient time to place a neuraxial block or dose an existing epidural catheter, anesthesia type was not a predictor of lower umbilical artery pH. Anesthetic technique was not a predictor of lower umbilical artery pH in non-emergent cases.ConclusionsSpinal anesthesia was not associated with lower umbilical artery pH compared to other types of anesthesia. This might be due to the use of phenylephrine in our practice.     

Effects of maternal supplementary oxygen on the newborn for elective cesarean deliveries under spinal anesthesia

Purpose  

The aim of this investigation was to determine whether supplementary oxygen provided by either nasal cannula or face mask versus room air might affect fetal oxygenation during elective cesarean section under spinal anesthesia by assessing maternal and neonatal regional cerebral oxygenation (rSO₂) with a cerebral oximeter.     

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。     

Comparison between colloid preload and crystalloid co-load in cesarean section under spinal anesthesia: a randomized controlled trial

BackgroundHypotension is a common problem during spinal anesthesia for cesarean delivery. Intravenous fluid loading is used to correct preoperative dehydration and reduce the incidence and severity of hypotension. Different fluid regimens have been studied but colloid preload and crystalloid co-load have not been compared.MethodsIn this randomized double-blind study, 210 patients scheduled for elective cesarean section under spinal anesthesia were randomly allocated to receive either 6% hydroxyethyl starch 130/0.4 500 mL before spinal anesthesia (colloid preload) or Ringer’s acetate solution 1000 mL administered rapidly starting with intrathecal injection (crystalloid co-load). Maternal hypotension (systolic blood pressure <80% of baseline or <90 mmHg) and severe hypotension (systolic blood pressure <80 mmHg) were treated with 5 and 10 mg ephedrine boluses, respectively. The primary outcome was the incidence of hypotension. Secondary outcomes included the incidence of severe hypotension, total ephedrine dose, nausea and vomiting and neonatal outcome assessed by Apgar scores and umbilical artery blood gas analysis.ResultsData analysis was performed on 205 patients; 103 in the colloid preload group and 102 in the crystalloid co-load group. There were no significant differences in the incidence of hypotension (52.4% vs. 42.2%; P=0.18) or severe hypotension (15.5% vs. 9.8%; P=0.31) between colloid preload and crystalloid co-load groups, respectively. The median [range] ephedrine dose was 5 [0–45] mg in the colloid preload group and 0 [0–35] mg in the crystalloid co-load group (P=0.065). There were no significant differences in maternal nausea or vomiting or neonatal outcomes between groups.ConclusionThe use of 1000 mL crystalloid co-load has similar effect to 500 mL colloid preload in reducing the incidence of hypotension after spinal anesthesia for elective cesarean delivery. Neither technique can totally prevent hypotension and should be combined with vasopressor use.     

A prospective observational study to investigate the relationship between local anesthetic infiltration pain before spinal anesthesia and acute and chronic postsurgical pain in women undergoing elective cesarean delivery

BackgroundCesarean delivery is one of the most common procedures performed worldwide. We conducted this prospective cohort study to evaluate the association between local anesthetic infiltration (LAI) pain prior to spinal anesthesia and pain and morphine consumption within 24 h after cesarean delivery (primary outcomes). A secondary objective was to assess the association between LAI pain and pain at one month postoperatively.MethodsRecruitment of 216 eligible women scheduled for elective cesarean delivery. Local infiltration before spinal anesthesia was performed using a 24-gauge needle and 3 mL 2% plain lidocaine. All subjects received 2.2 mL 0.5% hyperbaric bupivacaine with 200 µg morphine for spinal anesthesia. A 0–10 verbal numerical rating scale was used to assess LAI pain severity, and subsequent pain at 24 h, 1, 3 and 12 months.ResultsWe found a moderate correlation between LAI pain intensity and severity of acute pain at rest (rho=0.56, P <0.001) and with movement (rho=0.58, P <0.001) and a weak correlation with morphine consumption (rho=0.17, P=0.01) within 24 h postoperatively. We also found a positive correlation between LAI pain and the severity of persistent wound pain at rest (rho=0.30, P <0.001) and with movement (rho=0.52, P <0.001) at 1 month. The incidence of wound pain at 1, 3 and 12 months postoperatively was 37.1%, 7.0% and 1.4%, respectively.ConclusionsPain from LAI prior to spinal anesthesia is significantly associated with subsequent postoperative pain both acutely and at one month in women scheduled for elective cesarean delivery under spinal anesthesia.     

The impact of gestational age and fetal weight on the risk of failure of spinal anesthesia for cesarean delivery

BackgroundThere are limited data about spinal dosing for cesarean delivery in preterm parturients. We investigated the hypothesis that preterm gestation is associated with an increased incidence of inadequate spinal anesthesia for cesarean delivery compared with term gestation.MethodsWe searched our perioperative database for women who underwent cesarean delivery under spinal or combined spinal-epidural anesthesia with hyperbaric bupivacaine ⩾10.5 mg. The primary outcome was the incidence of inadequate surgical anesthesia needing conversion to general anesthesia or repetition or supplementation of the block. We divided patients into four categories: <28, 28 to <32, 32 to <37 and ⩾37 weeks of gestation. The chi-square test was used to compare failure rates and a multivariable regression analysis was performed to investigate potential confounders of the relationship between gestational age and failure.ResultsA total of 5015 patients (3387 term and 1628 preterm) were included. There were 278 failures (5.5%). The incidence of failure was higher in preterm versus term patients (6.4% vs. 5.1%, P=0.02). Failure rates were 10.8%, 7.7%, 5.3% and 5% for <28, 28 to <32, 32 to <37 and ⩾37 weeks of gestation, respectively. In the multivariable model, low birth weight (P<0.0001), gestational age (P=0.03), ethnicity (P=0.02) and use of combined spinal-epidural anesthesia (P<0.0001) were significantly associated with failure.ConclusionsAt standard spinal doses of hyperbaric bupivacaine used in our practice (⩾10.5 mg), there were higher odds of inadequate surgical anesthesia in preterm parturients. When adjusting for potential confounders, low birth weight was the main factor associated with failure.     

Comparison of the ED50 of intrathecal hyperbaric ropivacaine co-administered with or without intrathecal dexmedetomidine for cesarean section: A prospective,double-blinded,randomized dose-response trial using up-down sequential allocation method

Study objectiveStudies have showed that intrathecal dexmedetomidine as supplements to local anesthetics can improve the quality of the spinal anesthesia and reduce the local anesthetic requirement of spinal anesthesia for cesarean section. However, the magnitude of this effect has not been fully quantified. Therefore, we conducted the present study to investigate the ED₅₀ of intrathecal hyperbaric ropivacaine with or without dexmedetomidine for cesarean section in healthy parturients. ED₅₀ values obtained were compared to estimate the effect of intrathecal dexmedetomidine versus placebo on ropivacaine requirement.DesignSingle-blinded, prospective, randomized study.SettingDepartment of Anesthesia, Women's Hospital, Zhejiang University School of Medicine.PatientsSixty healthy parturients under elective cesarean section with combined spinal-epidural anesthesia were randomized into Group C (intrathecal ropivacaine alone) and Group D (intrathecal ropivacaine + 5 μg dexmedetomidine).InterventionsThe dose of intrathecal ropivacaine for the first parturient in both groups was 11 mg. An increment or decrement of 0.5 mg intrathecal ropivacaine was made for the subsequent parturient based on the effective or ineffective response of the previous parturient. Effective dose was defined as a bilateral T6 or above sensory block level was achieved within 15 min after induce of spinal anesthesia and no additional epidural anesthetics was required during surgery. The Dixon and Massay sequential method and Probit regression were applied to calculate the ED₅₀ of intrathecal ropivacaine in both groups.MeasurementsCharacteristics of spinal anesthesia and side effects were recorded.Main resultsThe ED₅₀ of hyperbaric ropivacaine calculated by Dixon and Massay formula was 11.4 mg (95% CI, 11.1–11.7 mg) in Group C, and 9.4 mg (95% CI, 9.0–9.7 mg) in Group D (P < 0.05). While using the Probit regression, the ED₅₀ of intrathecal hyperbaric ropivacaine was 11.1 mg (95% CI, 10.7–11.6 mg) in Group C, and 9.1 mg (95% CI, 8.6–9.5 mg) in Group D. Shivering was less observed in Group D than in Group C (P < 0.05). There was no significant difference in the onset time of sensory block or motor block, the incidence of hypotension, bradycardia, nausea and vomiting, sedation and pruritus between the two groups.ConclusionUnder the conditions of the present study, intrathecal dexmedetomidine (5 μg) reduced the ED₅₀ of intrathecal hyperbaric ropivacaine by approximately 18% for cesarean section in healthy parturients under combined spinal-epidural anesthesia.     

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 sequential compression mechanical pump to prevent hypotension during elective cesarean section under spinal anesthesia

BackgroundSpinal anesthesia is a standard technique for cesarean section but can cause hypotension which may be related to venous pooling secondary to progesterone-induced decreases in vascular tone. This study investigated the use of a sequential compression mechanical pump with thigh-high sleeves with compression cycles timed to venous refilling. We hypothesized that this would recruit pooled venous blood from the lower limbs, maintain the central blood volume and thus decrease the incidence of hypotension.MethodsOne hundred parturients scheduled for elective cesarean section under spinal anesthesia were recruited and randomly assigned to use of either a mechanical pump (Group M) or control (Group C). A standardized protocol for co-hydration and anesthesia was followed. Hypotension, defined as a decrease in systolic blood pressure by >20% from baseline, was treated with 6-mg boluses of intravenous ephedrine. The incidence of hypotension was defined as the primary outcome. Median ephedrine requirement was taken as a measure of the severity of hypotension.ResultsHypotension occurred in 12 of 47 (25.5%) patients in Group M compared to 27 of 45 (60%) in Group C (P = 0.001). The median [range] ephedrine dose was greater in Group C (12 [0–24] mg) compared to Group M (0 [0–12] mg) (P < 0.001). There was no difference between groups in the time to onset of hypotension.ConclusionThe use of a sequential compression mechanical pump that detects venous refilling and cycles accordingly, reduced the incidence and severity of hypotension after spinal anesthesia for cesarean section.     

Effect of preoperative Mg sulfate infusion on serum cardiac troponin (cTn) in moderate preeclamptic undergoing elective cesarean section under spinal anesthesia

This study was designed to investigate and compare the effect of preoperative Mg sulfate infusion on serum cardiac troponin (cTn) in moderate preeclampsia undergoing elective cesarean section. A total of fifty parturients having moderate preeclampsia scheduled for elective cesarean section were included. They were randomly allocated into two equal groups 25 each, magnesium group (GMg) received preoperative magnesium sulfate infusion and control group (GC) then both received spinal anesthesia, serum troponin measured preoperative then at 6, 12 and 24 h postoperative. Mean arterial pressure and heart rate were also recorded. Baseline serum cardiac troponin was higher above normal and was comparable at the rest of times in both groups. Mean arterial pressure readings were significantly lower in GMg compared to GC at induction of spinal, skin incision and skin closure (P < 0.05) and were comparable at the rest of times. Serum cardiac troponin (cTn) levels were comparable in parturients received magnesium sulfate infusion preoperatively with those did not receive magnesium sulfate.     

Maternal and neonatal effects of bolus administration of ephedrine and phenylephrine during spinal anaesthesia for caesarean delivery: a randomised study

BackgroundMaternal haemodynamic changes and neonatal well-being following bolus administration of ephedrine and phenylephrine were compared in 60 term parturients undergoing elective caesarean delivery under spinal anaesthesia.MethodsIn a randomised double-blind study, women received boluses of either ephedrine 6 mg (group E; n=30) or phenylephrine 100 μg (group P; n=30) whenever maternal systolic pressure was ?80% of baseline.ResultsChanges in systolic pressure were comparable in the two groups. There were no differences in the incidence of bradycardia (group E: 0% vs. group P: 16.7%; P>0.05), nausea (group E: 13% vs. group: P 0; P>0.05) and vomiting (group E: 3.3% vs. group P: 0; P>0.05). Umbilical artery (UA) pH (group E: 7.29 ± 0.04 vs. group P: 7.32 ± 0.04; P=0.01) and venous pH (group E: 7.34 ± 0.04 vs. group P: 7.38 ± 0.05; P=0.002) were significantly greater in group P than in group E. UA base excess was significantly less in group E (-2.83 ± 0.94 mEq/L) than in group P (-1.61 ± 1.04 mEq/L; P<0.001). Apgar scores at 1, 5 and 10min and neurobehavioural scores at 2-4 h, 24 h and 48 h were similar in the two groups (P>0.05).ConclusionsPhenylephrine 100 μg and ephedrine 6 mg had similar efficacy in the treatment of maternal hypotension during spinal anaesthesia for elective caesarean delivery. Neonates in group P had significantly higher umbilical arterial pH and base excess values than those in group E, which is consistent with other studies.