Minimal effective weight-based dosing of ondansetron to reduce hypotension in cesarean section under spinal anesthesia: a randomized controlled superiority trial

Commonly used antiemetics for prophylaxis of postoperative nausea and vomiting after Caesarean delivery with neuraxial morphine: a network meta-analysis

BACKGROUND

Dopamine antagonists, 5-HT3 antagonists, and dexamethasone are frequently used in obstetrics to prevent postoperative nausea and vomiting (PONV). However, the superiority of any drug class is yet to be established. This network meta-analysis aimed to compare the efficacy of these antiemetics for PONV prophylaxis in women receiving neuraxial morphine for Caesarean delivery.

METHODS

We searched PubMed, Embase, CENTRAL, Web of Science, and Wanfang Data for eligible randomised controlled trials. Primary outcomes were the incidences of postoperative nausea (PON) and postoperative vomiting (POV) within 24 h after surgery. We used a Bayesian random-effects model and calculated odds ratios with 95% credible intervals for dichotomous data. We performed sensitivity and subgroup analyses for primary outcomes.

RESULTS

A total of 33 studies with 4238 women were included. In the primary analyses of all women, 5-HT3 antagonists, dopamine antagonists, dexamethasone, and 5-HT3 antagonists plus dexamethasone significantly reduced PON and POV compared with placebo, and 5-HT3 antagonists plus dexamethasone were more effective than monotherapy. In the subgroup analyses, similar results were seen in women receiving epidural morphine or intrathecal morphine alone but not in women receiving intrathecal morphine with fentanyl or sufentanil. However, most included studies had some concerns or a high risk of bias, and the overall certainty of the evidence was low or very low.

CONCLUSIONS

Combined 5-HT3 antagonists plus dexamethasone are more effective than monotherapy in preventing PONV associated with neuraxial morphine after Caesarean delivery. Future studies are needed to determine the role of prophylactic antiemetics in women receiving intrathecal morphine and lipophilic opioids.

SYSTEMATIC REVIEW PROTOCOL

PROSPERO CRD42023454602.

Dose-Response Study of Phenylephrine for Preventing Spinal-Induced Hypotension During Cesarean Delivery with Combined Spinal-Epidural Anesthesia Under the Effect of Prophylactic Intravenous Ondansetron

Background

Ondansetron reduces the median effective dose (ED50) of prophylactic phenylephrine to prevent spinal-induced hypotension (SIH) during cesarean delivery. However, the exact dose response of phenylephrine in combination with prophylactic ondansetron for preventing SIH is unknown. Therefore, this study aimed to determine the dose-response of phenylephrine to prevent SIH in cesarean delivery when 4 mg of ondansetron was used as a preventive method.

Methods

A total of 80 parturients were enrolled and divided randomly into four groups (n = 20 in each group) who received either 0.2, 0.3, 0.4, or 0.5 μg/kg/min of prophylactic phenylephrine. Ten minutes before the initiation of spinal induction, 4 mg prophylactic ondansetron was administered. The effective dose of prophylactic phenylephrine was defined as the dose required to prevent hypotension after the period of intrathecal injection and up to neonatal delivery. The ED50 and ED90 of prophylactic phenylephrine and 95% confidence intervals (95% CI) were calculated using probit analysis.

Results

The ED50 and ED90 for prophylactic phenylephrine to prevent SIH were 0.25 (95% CI, 0.15 to 0.30), and 0.45 (95% CI, 0.39 to 0.59) μg/kg/min, respectively. No significant differences were observed in the side effects and neonatal outcomes between the four groups.

Conclusion

The administration of 4 mg of prophylactic ondansetron was associated with an ED50 of 0.25 (95% CI, 0.15~0.30) and ED90 of 0.45 (95% CI, 0.39~0.59) μg/kg/min for phenylephrine to prevent SIH.

Ultrasound-guided caudal anaesthesia combined with epidural anaesthesia for caesarean section: a randomized controlled clinical trial

BACKGROUND

Although epidural anaesthesia and spinal anaesthesia are currently the general choices for patients undergoing caesarean section, these two neuraxial anaesthesia methods still have drawbacks. Caudal anaesthesia has been considered to be more appropriate for gynaecological surgery. The purpose of this study was to compare epidural anaesthesia combined with caudal anaesthesia, spinal anaesthesia and single-space epidural anaesthesia for caesarean section with respect to postoperative comfort and intraoperative anaesthesia quality.

METHODS

In this clinical trial, 150 patients undergoing elective caesarean section were recruited and randomized into three groups according to a ratio of 1:1:1to receive epidural anaesthesia only, spinal anaesthesia only or epidural anaesthesia combined with caudal anaesthesia. The primary outcome was postoperative comfort in the three groups. Secondary outcomes included intraoperative anaesthesia quality and the incidences of nausea, vomiting, postdural puncture headache, maternal bradycardia, or hypotension.

RESULTS

More patients were satisfied with the intraoperative anaesthesia quality in the EAC group than in the EA group (P = 0.001). The obstetrician was more significantly satisfied with the intraoperative anaesthesia quality in the SA and EAC groups than in the EA group (P = 0.004 and 0.020, respectively). The parturients felt more comfortable after surgery in the EA and EAC groups (P = 0.007). The incidence of maternal hypotension during caesarean section was higher in the SA group than in the EA and EAC groups (P = 0.001 and 0.019, respectively).

CONCLUSIONS

Epidural anaesthesia combined with caudal anaesthesia may be a better choice for elective caesarean section. Compared with epidural anaesthesia and spinal anaesthesia, it has a higher quality of postoperative comfort and intraoperative anaesthesia.

Comparative dose-response study on the infusion of norepinephrine combined with intravenous ondansetron versus placebo for preventing hypotension during spinal anesthesia for cesarean section: a randomised controlled trial

BACKGROUND

Ondansetron has been reported to attenuate the incidence of spinal anaesthesia-induced hypotension (SAIH) and norepinephrine requirement during caesarean section. However, no quantitative study has evaluated the extent of this effect. This study aimed to determine the dose-response of prophylactic infusion of norepinephrine to prevent SAIH in parturients who received intravenous ondansetron or placebo before spinal anaesthesia for caesarean section. The median effective dose (ED 50 ) and 90% effective dose (ED 90 ) were compared to evaluate the effect of ondansetron versus placebo on the norepinephrine requirement.

MATERIALS AND METHODS

One hundred fifty parturients undergoing caesarean section were randomized to receive either 0.1 mg/kg ondansetron (group O) or saline control (group C) 10 min before spinal anaesthesia. The parturients were randomly assigned to one of five different norepinephrine infusion groups: 0.02, 0.04, 0.06, 0.08 or 0.10 µg/kg/min. An effective infusion dose of norepinephrine was defined as non-occurrence of hypotension during the study period. The values for ED 50 and ED 90 of norepinephrine infusion were determined using probit regression. Differences between the two groups were evaluated by comparing the relative median potency with 95% CIs.

RESULTS

The ED 50 values were 0.033 (95% CIs, 0.024-0.043) µg/kg/min in group C and 0.021 (95% CIs, 0.013-0.029) µg/kg/min in group O. The ED 90 values were 0.091 (95% CIs 0.068-0.147) µg/kg/min in group C and 0.059 (95% CIs 0.044-0.089) µg/kg/min in group O, respectively. The estimate of the relative median potency for norepinephrine in group C versus group O was 0.643 (95% CIs, 0.363-0.956). The incidence of side effects was comparable between groups. No significant difference in neonatal outcomes.

CONCLUSION

Intravenous ondansetron 0.1 mg/kg before spinal anaesthesia significantly reduced the dose requirement of prophylactic norepinephrine infusion in parturients undergoing elective caesarean section. This finding is potentially useful for clinical practice and further research.

Ondansetron for the Prevention of Pruritus in Women Undergoing Cesarean Delivery With Intrathecal Opioid: A Systematic Review and Meta-Analysis

BACKGROUND

Pruritus is a frequently reported and unpleasant side effect following intrathecal opioid use with frequency further increased among parturients. We have performed a systematic review to assess the overall efficacy of ondansetron for the prevention of pruritus in patients receiving intrathecal opioid as part of spinal anesthesia for cesarean delivery.

METHODS

A literature search of MEDLINE, Embase, Cochrane, and Web of Science databases was conducted from date of inception to September 2022. Studies that included patients undergoing cesarean delivery with spinal anesthesia using intrathecal opioid were included. The primary outcome was the presence of pruritus, and the secondary outcome was time to onset of pruritus. Data from included studies were pooled for analysis using an appropriately determined random-effects model. Outcomes were presented using forest plots and 95% confidence intervals. Additional sensitivity and subgroup analysis were performed. Trial sequential analysis was conducted for the primary outcome.

RESULTS

Twenty-three randomized controlled trials with a total of 2586 patients were included: 1219 received ondansetron, 1030 received a placebo, and a further 337 received a different study drug and were excluded from analysis. Opioids used in the included studies were morphine, fentanyl, and sufentanil. Patients who received ondansetron showed a significant reduction in the incidence of pruritus compared to the control group (RR, 0.81; 95% confidence interval [CI], 0.71-0.92; I 2 = 64%). There was no significant difference in pruritus onset between the groups (mean difference [MD], 17.54 minutes; 95% CI, -2.18 to 37.26; I 2 = 83%). The overall Grading of Recommendations Assessment, Development, and Evaluation (GRADE) assessment of quality of evidence was low.

CONCLUSIONS

This systematic review has demonstrated a significant reduction in the incidence of pruritus following the use of ondansetron. This is in contrast to previously published meta-analyses. Studies included were of varying quality and some at high risk of bias with a high degree of statistical heterogeneity. Furthermore, high-quality and well-powered studies are required to confirm these findings.

Pharmacological agents for prevention of pruritus in women undergoing Caesarean delivery with neuraxial morphine: a systematic review and Bayesian network meta-analysis

BACKGROUND

Neuraxial opioids provide effective analgesia for Caesarean delivery, however, pruritus can be a troubling side-effect. Effective agents to prevent pruritus are needed. Our objective was to perform an updated systematic review and network meta-analysis to provide clinicians with a comparison of relative efficacy of available interventions to reduce the incidence of pruritus, induced by either intrathecal or epidural single-shot morphine, in women undergoing Caesarean delivery.

METHODS

Databases systematically searched (up to January 2022) included PubMed MEDLINE, Web of Science, EBSCO CINAHL, Embase, LILACS, and two Cochrane databases. We included randomised, controlled trials involving adult female patients undergoing Caesarean delivery. We pooled trials comparing interventions used for preventing pruritus after Caesarean delivery and performed a Bayesian model network meta-analysis.

RESULTS

The final primary network included data from comparisons of 14 distinct interventions (including placebo) used to reduce the incidence of pruritus in 6185 participants. We judged five interventions to be 'definitely superior' to placebo: propofol, opioid agonist-antagonists (neuraxial), opioid antagonists, opioid agonist-antagonists (systemic), and serotonin antagonists. For the network evaluating the incidence of severe pruritus (warranting additional therapeutic treatment of pruritus), data were available for 14 interventions (including placebo) in 4489 patients. For this outcome, we judged three interventions to be 'definitely superior' to placebo: dopamine antagonists (neuraxial) and systemic and neuraxial opioid agonist-antagonists.

CONCLUSION

Our analysis found several interventions to be effective in reducing the incidence of pruritus. Although sub-hypnotic doses of propofol appear to have an antipruritic effect, replication of this finding and further investigation of optimal dosing are warranted.

SYSTEMATIC REVIEW PROTOCOL

PROSPERO (CRD42022367058).

Granisetron or ondansentron to prevent hypotension after spinal anesthesia for elective cesarean delivery: A randomized placebo-controlled trial

STUDY OBJECTIVE

This study aimed to compare the effects of high doses of ondansetron and granisetron before spinal anesthesia on hemodynamic parameters in patients undergoing elective cesarean section.

DESIGN

A double-blinded randomized placebo-controlled trial.

SETTING

Operating room.

PATIENTS

A total of 120 parturients with term pregnancy undergoing elective cesarean section with combined spinal-epidural anesthesia were included.

INTERVENTIONS

Three groups (n = 40 for each group) were formed by randomization. Five minutes before the anesthesia procedure, Group I received 8 mg intravenous (IV) ondansetron diluted in 10 ml normal saline, Group II received IV 3 mg granisetron diluted in 10 ml normal saline, and Group III received IV 10 ml normal saline.

MEASUREMENTS

Following intrathecal drug administration, intraoperative hemodynamic changes were recorded every 2 min for 20 min and then every 5 min until the end of the operation.

MAIN RESULTS

Twenty patients (50%) in Group I, 12 patients (30%) in Group II, and 29 patients (72.5%) in Group III had hypotension requiring treatment with IV ephedrine (P = 0.001). The ephedrine requirement in Group III was significantly higher than in Groups I (P = 0.033) and II (P < 0.001). Also, the ephedrine requirement in Group II was lower than in Group I, but the difference was not statistically significant (P = 0.055). The mean arterial pressure for the three groups differed in the 10th, 18th, and 60th minutes. The number of patients with nausea or vomiting was lower in Groups I and II than in Group III (P < 0.001). At 5 min, the Apgar scores were higher than 8 for all neonates. Postoperative scores for the visual analogue scale were similar for all groups.

CONCLUSIONS

It was concluded that prophylactic IV administration of 3 mg of granisetron or 8 mg of ondansetron before spinal anesthesia results in a significantly lower ephedrine requirement compared to placebo.

The transverse diameter of right common femoral vein by ultrasound in the supine position for predicting post-spinal hypotension during cesarean delivery

Background

Post-spinal anesthesia hypotension during cesarean delivery is caused by decreased systemic vascular resistance due to the blockage of the autonomic nerves, which is further worsened by inferior vena cava (IVC) compression by the gravid uterus. This study aimed to assess whether peak velocity and diameter of the IVC below the xiphoid or right common femoral vein (RCFV) in the inguinal region, as measured on ultrasound, could reflect the degree of IVC compression and further identify parturients at risk of post-spinal hypotension.

Methods

Fifty-six parturients who underwent elective cesarean section with spinal anesthesia were included in this study; peak velocities and anteroposterior diameters of the IVC and peak velocities and transverse diameters of the RCFV were measured using ultrasound before anesthesia. The primary outcome was the ultrasound measurements of IVC and RCFV acquired before spinal anesthesia and their association with post-spinal hypotension. Hypotension was defined as a drop in systolic arterial pressure by > 20% from the baseline. Multinomial logistic regression analysis was used to identify the association between the measurements of IVC, RCFV, and post-spinal hypotension during cesarean delivery. Receiver operating characteristic curves were used to test the abilities of the identified parameters to predict post-spinal hypotension; the areas under the curve and optimum cut-off values for the predictive parameters were calculated.

Results

A longer transverse diameter of the RCFV was associated with the occurrence of post-spinal hypotension (odds ratio = 2.022, 95% confidence interval [CI] 1.261–3.243). The area under the receiver operating characteristics curve for the prediction of post-spinal hypotension was 0.759 (95% CI 0.628–0.890, P = 0.001). A transverse diameter of > 12.2 mm of the RCFV could predict post-spinal hypotension during cesarean delivery.

Conclusions

A longer transverse diameter of RCFV was associated with hypotension and could predict parturients at a major risk of hypotension before anesthesia.

Trial registration

This study was registered at http://www.chictr.org.cn on 16, May, 2018. No. ChiCTR1800016163.

Medications for the prevention of pruritus in women undergoing cesarean delivery with Intrathecal morphine: A systematic review and bayesian network meta-analysis of randomized controlled trials

PURPOSE

Intrathecal morphine-induced pruritus can cause significant discomfort in parturients and is refractory to conventional antipruritic treatment. This systematic review and network meta-analysis evaluates the effectiveness of the medications used for prevention of intrathecal (IT) morphine-induced pruritus after cesarean delivery under spinal anesthesia.

METHODS

A literature search was conducted from 1946 up to October 2019. We included all randomized controlled trials (RCTs) that compared medications used for prevention of pruritus with a control group in women undergoing cesarean delivery under spinal anesthesia with IT morphine. The primary outcome examined was the incidence of pruritus up to 24 h after cesarean delivery. Dichotomous data were extracted and summarized using odds ratios (OR) and 95% credible intervals (CrI) with Bayesian random effects network meta-analysis model. The GRADE approach was used to evaluate quality of the studies and effect evidence.

RESULTS

Of the 26 studies included in the systematic review, 21 studies with a total of 2594 patients were included in the network meta-analysis [prophylaxis, n = 1603 (62%) vs. control, n = 991 (38%)]. These studies investigated seven classes of drugs including serotonin-receptor antagonists, dopamine-receptor antagonists, opioid agonist-antagonists, opioid-receptor antagonists, histamine-receptor antagonists, propofol and celecoxib. The network meta-analysis showed that serotonin-receptor antagonists' prophylaxis [control vs. prophylaxis: 60% vs. 47%; OR (95% CrI): 2.69 (1.43-5.36)] and opioid agonist-antagonists prophylaxis [control vs. prophylaxis: 72% vs. 47%; OR (95% CrI): 4.57 (1.67-12.91)] decreased the incidence of pruritus compared to the control group. Although all included studies were at low risk of bias, the quality of the overall network meta-analysis pooled estimates was low.

CONCLUSION

This bayesian network meta-analysis of RCTs demonstrates serotonin-receptor antagonists and opioid agonist-antagonists may prevent pruritus in women undergoing cesarean delivery with intrathecal morphine compared to control group. However, further RCTs of adequate power and clearly defined end points are warranted.

Does an Earlier or Late Intravenous Injection of Ondansetron Affect the Dose of Phenylephrine Needed to Prevent Spinal-Anesthesia Induced Hypotension in Cesarean Sections?

Background

There was controversy about ondansetron can reduce the incidence of spinal-induced hypotension and decrease the consumption of vasopressor in cesarean delivery with spinal anesthesia. We hypothesized that different timing of ondansetron administration may contribute to the controversy. Therefore, we aimed to determine the effect of different timing of ondansetron administration on the dose requirement of preventing phenylephrine via comparing the ED₅₀ of prophylactic phenylephrine.

Methods

Seventy-five parturients were finally enrolled in this prospective, randomized, double-blinded dose finding study. Ondansetron or placebo was administered 5 min or 15 min before intrathecal injection. Up-down allocation method was used to determine the dose of prophylactic phenylephrine for each parturient in the three groups. The initial infusion rate of first patient was 0.5 µg/kg/min. Then, the rate for next patient was varied with increasing or decreasing of 0.05 μg/kg/min according to the response of the previous patient. An effective dose was defined as no hypotension occurred during the study period. An ineffective dose was defined as hypotension occurred during the study period. Study period in this study is from intrathecal injection to neonatal delivery. ED₅₀ of phenylephrine infusion was calculated by probit regression.

Results

The ED₅₀ of intravenous phenylephrine calculated by probit analysis was 0.33 (95% CI 0.20 to 0.38) µg/kg/min and 0.36 (95% CI 0.32 to 0.38) µg/kg/min in group A and B, and 0.41 (95% CI 0.37 to 0.44) µg/kg/min in group C for patients undergoing cesarean delivery with combined spinal-epidural anesthesia.

Conclusion

An earlier administration of 4 mg prophylactic ondansetron contributed no benefits for lowing the dose of prophylactic phenylephrine compared to a late administration, but can decrease the dose of preventing phenylephrine in patients undergoing cesarean delivery with combined spinal-epidural anesthesia. This finding may be useful for clinical practice and further studies.

SPINAL ANAESTHESIA-INDUCED HYPOTENSION IN OBSTETRICS: PREVENTION AND THERAPY

Regional centro-axial anaesthesia, primarily spinal block, is the preferred method of anaesthesia for elective caesarean section because it entails fewer risks for the mother and the foetus compared to general anaesthesia. The most common side effect associated with spinal block is hypotension due to sympatholysis, occurring in up to 75% of cases. Spinal block-induced sympatholysis leads to vasodilatation and consequently causes maternal hypotension, which may compromise uterine blood flow and foetal circulation, and thus cause foetal hypoxia, bradycardia and acidosis. The selection of the most efficient treatment strategy to achieve haemodynamic stability during spinal anaesthesia for caesarean section continues to be one of the main challenges in obstetric anaesthesiology. A number of measures for the prevention and treatment of spinal block-induced hypotension are used in clinical practice, such as preloading and coloading with crystalloid and/or colloid infusion, wrapping of lower limbs with compression stockings or bandages, administering an optimal dose of local anaesthetic and achieving an optimal spinal block level, left tilt positioning, and administering inotropes and vasopressors. Instead of administering vasopressors after a drop in blood pressure has already occurred, the latest algorithms recommend a prophylactic administration of vasopressor infusion. The preferred vasoconstrictor in this case is phenylephrine, which is associated with a lower incidence of foetal acidosis, and maternal nausea and vomiting compared to other vasoconstrictors.