The Effects of Ephedrine and Phenylephrine on Placental Vascular Resistance During Cesarean Section Under Epidual Anesthesia

Anesthesia characteristic of an algorithm of bupivacaine dose based on height in caesarean section under spinal anesthesia: a retrospective cohort study

BACKGROUND

An algorithm of bupivacaine dose based on height is applied to reduce maternal hypotension in caesarean section under spinal anesthesia. This study is designed to further verify whether the algorithm of bupivacaine dose based on height is suitable.

METHODS

The parturients were grouped according to height. The comparison of anesthesia characteristic among subgroups was carried out. The univariate and multivariate binary logistic regressions were executed to reanalyze the interference factor for the anesthesia characteristic.

RESULTS

When the dose of bupivacaine was adjusted by using the height based dosing algorithm, except for weight (P < 0.05), other general data did not present statistical changes with height (P > 0.05); the incidences of complications, characteristics of sensory or motor block, quality of anesthesia and neonatal outcome were of no statistical difference among parturients with different heights (P > 0.05); the height, weight and body mass index were not related with maternal hypotension (P > 0.05). When the dose of bupivacaine is constant, except for weight and body mass index (P > 0.05), the height was the independent risk factor for maternal hypotension (P < 0.05).

CONCLUSIONS

Except for weight and body mass index, the height has an influence on the bupivacaine dose. It is reasonable that the bupivacaine dose is adjusted by using this dosing algorithm based on height.

TRIAL REGISTRATION

This study was registered at http://clinicaltrials.gov (13/04/2018, NCT03497364).

A Height-Based Dosing Algorithm of Bupivacaine in Spinal Anesthesia for Decreasing Maternal Hypotension in Cesarean Section Without Prophylactic Fluid Preloading and Vasopressors: A Randomized-Controlled Non-Inferiority Trial

Background

There is a high incidence of maternal hypotension in spinal anesthesia for cesarean section. The aim of the study is to investigate whether there is a height-based dosing algorithm of bupivacaine that provides adequate anesthesia with less maternal hypotension.

Methods

There were 2 groups of 280 parturients who did not receive prophylactic fluid preloading: Test and Conventional group. In Test group, a height based dosing algorithm was used to confirm the dose of bupivacaine in parturients without prophylactic vasopressors. In the Conventional group, a constant dose of bupivacaine was used. The complications and quality of anesthesia were evaluated.

Results

In the Conventional group, the shorter participants had higher incidence of hypotension, faster sensory block time, and more participants with complete motor block (p = 0.030, 2.957 × 10^-14, and 0.012). In the Test group, the incidence of hypotension, sensory block time, and number of participants with complete motor block did not change with height (p = 0.199, 0.617, and 0.209). The height-based dosing algorithm of bupivacaine decreased the incidence of hypotension (p = 0.004), induced lower sensory block level and less degree of motor block (p = 3.513 × 10^-7 and 5.711 × 10^-11). The quality of analgesia, quality of muscle relaxation, and degree of intraoperative comfort were similar in both groups (p = 0.065, 0.498, and 0.483).

Conclusions

The height influences the dose of bupivacaine in spinal anesthesia; without prophylactic fluid pre-loading and vasopressors, the height-based dosing algorithm of bupivacaine is suitable, and meets the cesarean section' requirement with less maternal hypotension.

Clinical Trial Registration

www.ClinicalTrials.gov, identifier: NCT03497364.

Effects of Vasoactive Medications and Maternal Positioning During Cesarean Delivery on Maternal Hemodynamics and Neonatal Acid-Base Status

Maternal hemodynamics, positioning, and anesthesia technique for cesarean delivery influence neonatal acid-base balance; direct effects from drugs that cross the placenta also have an influence. Spinal anesthesia limits fetal exposure to depressant drugs and avoids maternal airway instrumentation, but is associated with hypotension. Hypotension may be prevented/treated with vasopressors and intravenous fluids. Current evidence supports phenylephrine as the first-line vasopressor. Fifteen degrees of lateral tilt during cesarean delivery has been advocated to relieve vena caval obstruction, but routine use may be unnecessary in healthy nonobese women having elective cesarean delivery if maternal blood pressure is maintained near baseline.

Height-based dosing algorithm of bupivacaine in spinal anaesthesia for decreasing maternal hypotension in caesarean section without prophylactic fluid preloading and vasopressors: study protocol for a randomised controlled non-inferiority trial

INTRODUCTION

Effectively preventing or treating spinal-induced maternal hypotension is considered to be the Holy Grail of obstetric anaesthesia. Prophylactic fluid preloading and vasopressors decrease hypotension but may aggravate heart load, induce fetal acidosis or maternal bradycardia. Using low-dose local anaesthetic decreases hypotension but may cause insufficient anaesthesia. Whether there is a height-based dosing algorithm of local anaesthetic in spinal anaesthesia for caesarean section that can provide sufficient anaesthesia with less hypotension without prophylactic fluid preloading and vasopressors is unclear. This study was designed to investigate a height-based dosing algorithm of bupivacaine in spinal anaesthesia for caesarean section.

METHODS AND ANALYSIS

This single-centre, double-blinded, prospective, non-inferiority, randomised controlled trial will include 264 parturients (between 18 and 45 years of age) who are scheduled for caesarean section. All participants will not receive prophylactic fluid preloading. The participants will be randomly divided into two groups: the test group or conventional group. For parturients in the test group, 0.5% isobaric bupivacaine (1.15-1.70 mL) will be injected into the subarachnoid space without prophylactic vasopressors. The bupivacaine dose depends on the height of subjects. For parturients in the conventional group, 0.5% bupivacaine (1.8 mL) will be injected into the subarachnoid space along with prophylactic vasopressors. The primary outcome is the incidence of maternal hypotension. The secondary outcomes include the failure rate of spinal anaesthesia, level of sensory block, degree of motor block, other complications in parturients, time of operation, neonatal outcome and quality of anaesthesia.

ETHICS AND DISSEMINATION

This study was approved by the Ethics Committee of Shenzhen People's Hospital of Jinan University (Permit No. SZY-00251, chairperson Xiaofang Yu) on 8 February 2018The study results will be disseminated through peer-reviewed journals, professional societies and meetings.

TRIAL REGISTRATION NUMBER

NCT03497364; Pre-results.

Phenylephrine vs ephedrine in cesarean delivery under spinal anesthesia: A systematic literature review and meta-analysis

BACKGROUND

In the past 20 years, many studies compared phenylephrine with ephedrine to prevent or treat hypotension in elective or emergency cesarean delivery and parturients with pre-eclampsia. A meta-analysis of the abovementioned trials is needed.

METHODS

Several databases (PubMed, Embase, Web of Science and Cochrane Library) were searched from inception to April 2018 for trials comparing phenylephrine with ephedrine in cesarean delivery. The primary outcome is the incidence of maternal hypotension.

RESULTS

Thirty-six trials (2439 patients) with elective cesarean delivery, three trials (400 patients) with emergency cesarean delivery and three trials (192 patients) with parturients with pre-eclampsia were included and analyzed. The incidence of hypotension did not differ in the elective surgery group (relative risk 0.83, 95% CI 0.66 to 1.05), emergency surgery group (relative risk 1.02, 95% CI 0.87 to 1.19) and pre-eclamptic parturients group (relative risk 0.93, 95% CI 0.63 to 1.37). The phenylephrine group had a higher incidence of bradycardia and lower incidences of tachycardia and nausea or vomiting in all three patient groups. The phenylephrine group also had lower fetal acidosis rate, higher umbilical artery and vein pH values and less base excess in the elective surgery. The abovementioned outcomes were similar in the emergency surgery group and the pre-eclampsia group. Publication bias for hypotension was detected. However, the trim and fill method demonstrated that the publication bias had little impact on hypotension. Trial sequential analysis of hypotension in elective surgery showed that this meta-analysis lacked a sufficient cumulative sample size and that further studies should be included.

CONCLUSION

Phenylephrine and ephedrine were both effective in maintaining hemodynamic balance. Newborns benefited more from phenylephrine in elective cesarean delivery, but not in emergency cesarean delivery or in parturients with pre-eclampsia. More trials should be included to achieve more conclusive results.

Comparison of Phenylephrine and Ephedrine in Treatment of Spinal-Induced Hypotension in High-Risk Pregnancies: A Narrative Review

Purpose

To compare maternal and fetal effects of intravenous phenylephrine and ephedrine administration during spinal anesthesia for cesarean delivery in high-risk pregnancies.

Source

An extensive literature search was conducted using the US National Library of Medicine, MEDLINE search engine, Cochrane review, and Google Scholar using search terms “ephedrine and phenylephrine,” “preterm and term and spinal hypotension,” “preeclampsia and healthy parturients,” or “multiple and singleton gestation and vasopressor.” Society of Obstetric Anesthesia and Perinatology meeting abstracts for the past 4 years were also searched for relevant studies.

Principle findings

Both phenylephrine and ephedrine can be safely used to counteract hypotension after spinal anesthesia in patients with uteroplacental insufficiency, pregnancy-induced hypertension, and in non-elective cesarean deliveries. Vasopressor requirements before delivery in high-risk cesarean sections are reduced compared to healthy parturients. Among the articles reviewed, there were no statistically significant differences in umbilical arterial pH, umbilical venous pH, incidence of fetal acidosis, Apgar scores, or maternal hypotension when comparing maternal phenylephrine and ephedrine use.

Conclusion

From the limited existing data, phenylephrine and ephedrine are both appropriate selections for treating or preventing hypotension induced by neuraxial blockade in high-risk pregnancies. There is no clear evidence that either medication is more effective at maintaining maternal blood pressure or has a superior safety profile in this setting. Further investigations are required to determine the efficacy, ideal dosing regimens, and overall safety of phenylephrine and ephedrine administration in high-risk obstetric patients, especially in the presence uteroplacental insufficiency.