Effect of a High-Rate Versus a Low-Rate Oxytocin Infusion for Maintaining Uterine Contractility During Elective Cesarean Delivery: A Prospective Randomized Clinical Trial

Impact of different obstetric interventions and types of delivery on breastfeeding: a nationwide cross-sectional survey of Hungarian women

BACKGROUND

We assessed the effect of different obstetric interventions and types of delivery on breastfeeding.

METHODS

A quantitative, cross-sectional study was carried out using an online questionnaire. Data collection was performed in 2021 in Hungary. We included biological mothers who had raised their at least 5-year-old child(ren) at home (N = 2,008). The questionnaire was completed anonymously and voluntarily. In addition to sociodemographic data (age, residence, marital status, education, occupation, income status, number of biological children, and anthropometric questions about the child and the mother), we asked about the interventions used during childbirth, and the different ways of infant feeding used. Statistical analysis was carried out using Microsoft Excel 365 and SPSS 25.0. Descriptive statistics, two-sample t tests, χ2 tests and ANOVA were used to analyse the relationship or differences between the variables (p < 0,05).

RESULTS

We found that in deliveries where synthetic oxytocin was used for both induction and acceleration, there was a higher incidence of emergency cesarean section. However, the occurrence of vaginal deliveries was significantly higher in cases where oxytocin administration was solely for the purpose of accelerating labour (p < 0.001).Mothers who received synthetic oxytocin also received analgesics (p < 0.001). Women giving birth naturally who used oxytocin had a lower success of breastfeeding their newborn in the delivery room (p < 0.001). Children of mothers who received obstetric analgesia had a higher rate of complementary formula feeding (p < 0.001). Newborns born naturally had a higher rate of breastfeeding in the delivery room (p < 0.001) and less formula feeding in the hospital (p < 0.001). Infants who were breastfed in the delivery room were breastfed for longer periods (p < 0.001). Exclusive breastfeeding up to six months was longer for infants born naturally (p = 0.005), but there was no difference in the length of breastfeeding (p = 0.081).

CONCLUSIONS

Obstetric interventions may increase the need for further interventions and have a negative impact on early or successful breastfeeding.

TRIAL REGISTRATION

Not relevant.

Oxytocin infusion dose-response to maintain uterine tone in obese elective cesarean patients: a randomized controlled trial

Background

For cesarean delivery (CD), the 90% effective dosage (ED90) of oxytocin for a first bolus has been established. It is not yet known how much oxytocin to inject into obese women undergoing elective discectomy to keep their uterine tone (UT) appropriate. We hypothesized that patients who are overweight need a greater dose of oxytocin infusion; thus, we aimed to determine how the dose-response curve for oxytocin infusion changes following an initial 1 international unit (IU) bolus in obese women undergoing elective CD.

Methods

One hundred parturients with a body mass index (BMI) greater than 30 kg/m2 were randomly assigned to receive an infusion rate of 14, 18, 22, or 26 IU/h of oxytocin. When the uterine palpation is as hard as touching the forehead or tip of the nose, it is considered sufficient UT according to the criteria used by obstetricians. The median effective dose (ED50) and ED90 values were determined using probit analysis.

Results

We found the ED50 and ED90 values for the infusion dose of oxytocin were around 11.0 IU/h and 19.1 IU/h, respectively. Each group had a different number of parturients who needed rescued oxytocin: 14 IU/h for six, 18 IU/h for three, one for 22 IU/h, and none for 26 IU/h. The correlation between the frequency of rescued oxytocin administration and the amount of oxytocin infusion needed to avoid uterine atony was statistically significant (p = 0.02).

Conclusion

The present research showed that the most effective dosage of oxytocin infusion for obese parturients undergoing elective CD is 19.1 IU/h, following an initial loading dose of 1 IU. Patients with obesity should receive a greater dosage of prophylactic oxytocin, and further studies comparing patients with and without obesity (with higher BMI) are required.

Clinical Trial Registration

https://www.chictr.org.cn/showproj.html?proj=159951, identifier ChiCTR2200059582.

Oxytocin infusion for maintenance of uterine tone under prophylactic phenylephrine infusion for prevention of post-spinal hypotension in cesarean delivery: a prospective randomised double-blinded dose-finding study

BACKGROUND

Prior studies have shown that, when administered as an intravenous bolus to prevent uterine atony, prophylactic phenylephrine infusion increased the dose requirement of oxytocin and second-line uterotonics. For the prevention of uterine atony, oxytocin should be delivered by continuous infusion. Here, we aimed to determine the ED50 and ED90 parameters (the effective doses for 50 and 90% patients without uterine atony) of oxytocin for co-infusion with prophylactic phenylephrine during cesarean delivery.

METHODS

In this prospective randomized double-blinded dose-finding study, one hundred patients were divided into four groups to receive 2.5, 5.0, 7.5, or 10 IU/h oxytocin infusion, after the umbilical cord was clamped during the study period. The uterine tone was evaluated and defined as either adequate or inadequate. Probit regression analysis was applied to calculate the ED50 and ED90 of oxytocin infusion. Uterine tone, the percentage of patients who needed additional oxytocin bolus, second-line uterotonics, side effects, estimated blood loss, and neonatal outcomes were monitored.

RESULTS

The estimated ED50 and ED90 values of the oxytocin infusion doses for the prevention of uterine atony were 1.9 IU/h (95% CI -4.6-3.8) IU/h and 9.3 IU/h (95% CI 7.3-16.2) IU/h, respectively. Across groups, there was a significant linear trend between the infusion dose and the percentage of patients who required additional oxytocin (p-value = 0.002). No differences were observed in the incidence of side effects and neonatal outcomes.

CONCLUSION

Under the conditions of this study, the ED90 of oxytocin infusion for the prevention of uterine atony was 9.3 IU/h, which is higher than the current recommendation. This finding is helpful for clinical practice, because of the routine use of phenylephrine in cesarean delivery. Further studies are needed to determine the appropriate initial bolus of oxytocin after neonatal delivery.

TRIAL REGISTRATION

The study was registered on the Chinese Clinical Trial Register (register no. ChiCTR2200059556 ).

The utero-tonic effects of low dose intravenous ketamine in cesarean section under spinal anesthesia; A randomized double-blind clinical trial

Background

Recently, the prevalence of cesarean section (CS) has been on the rise and the proper uterine tone is an important issue. We investigated the effects of intravenous (IV) ketamine on intraoperative bleeding and the need for oxytocin in CS under spinal anesthesia (SA).

Methods

This study, took place at Alzahra hospital during 2020. Pregnant women candidate for elective CS under SA were divided into two groups of ketamine and placebo. In group K, after umbilical cord clamping, 0.25 mg/kg ketamine and in group P 2ccs normal saline was injected. Mean arterial pressure and heart rate were recorded at baseline, before and 5 minutes after cord clamping and at the end of the surgery. The drop in hemoglobin values, the administrated units of oxytocin and side effects were also recorded.

Results

No significant difference was found in terms of patients' demographic data (P ≥ 0.05). The mean units of administrated oxytocin in group K was 34.61±6.63 and in group P; 48.47±12.15, which was significantly different (P=0.0001). The drop in Hb was less in group K, however not statistically significant (P=0.094). The need for methergine was significantly higher in group P (P=0.0001). The mean HR was significantly higher in group P (P=0.027), however, no significant difference was observed regarding the MAP (P=0.064). The incidence of hallucination (4.8%) and nystagmus (21%) was significantly higher in group K (P= 0.0001), but nausea and vomiting were more significant in group P (P= 0.027).

Conclusion

Prophylactic administration of low-dose ketamine in CS under S.A could significantly reduce the administrated oxytocin units and the need for additional utero-tonics and was associated with less drop in Hb values.

Intravenous oxytocin regimens in patients undergoing cesarean delivery: a systematic review and network meta-analysis of cluster-based groups

Information on evaluations of different oxytocin regimens used to prevent post-partum hemorrhage during cesarean delivery is scarce, and there is a lack of statistically pooled results for comparative doses. In this review, we aimed to analyze the effectiveness of different oxytocin regimens used and rank them accordingly. We performed a meta-analysis of randomized controlled trials (RCTs) reporting the incidence of additional uterotonic (AUT) use or amount of blood loss during cesarean delivery, where different oxytocin regimens were compared. Cluster analysis was used to define different clusters of oxytocin therapy based on the identified variable regimens. During the frequentist network meta-analysis, all clusters were compared to bolus clusters of dose range 3-5 IU. Data from 33 RCTs (6741 patients) to 26 RCTs (5422 patients) were assessed for AUT use and blood loss, respectively. Pairwise meta-analysis revealed a significant reduction in the use of AUTs or blood loss was recorded for bolus-infusion combination regimens. The network meta-analysis found that combined bolus-infusion regimens of (i) 3-5 IU and 0.25-1 IU/min or (ii) 3-5 IU and < 0.25 IU/min had statistically significant results for lowest consumption of AUTs (Ranks 1 and 2, respectively); whereas with the latter's use, the lowest blood loss (Rank 2) was observed. In contrast, the dose range, > 5 IU regimen was associated with higher side effects (lowest rank). During cesarean delivery, a significant reduction in the use of AUTs or blood loss (Rank 2) was recorded for bolus-infusion combination regimens. High doses did not have enough evidence to draw meaningful conclusions.

Oxytocin infusion rates for maintaining uterine tone during non-elective cesarean section in laboring patients: a randomized, controlled trial

PURPOSE

Oxytocin infusions for uterine tone maintenance are recommended following initial low oxytocin doses during cesarean section. Very limited literature is available on the optimal infusion rates in laboring patients who have been earlier exposed to oxytocin.

METHODS

105 patients, having received oxytocin for induction/augmentation of labor, received oxytocin infusions at rates of 2.5 IU/h (Group 2.5), 5 IU/h (Group 5) or 10 IU/h (Group 10) following 3 IU slow bolus. The primary outcome measure was estimated intraoperative blood loss; secondary outcome measures included uterine tone adequacy, requirements for additional uterotonics, and any side effects. Minor postpartum hemorrhage (PPH) was defined as blood loss > 500 ml and major/severe hemorrhage as blood loss > 1000 ml.

RESULTS

Group 10 had minimum blood loss (311.1 ± 44.9 ml) and uterotonic requirements compared to other groups (p < 0.001). Group 2.5 had maximum blood loss (549.4 ± 74.3 ml) and uterotonic requirements; Group 5 had intermediate values (402.0 ± 49.5 ml). Twenty-six patients in group 2.5 had minor PPH against only one in group 5 and none in group 10 (p < 0.001). No patient in either group had major PPH. The incidence of hypotension was higher in group 10 than in group 2.5 (p = 0.004). Nausea and vomiting were also more frequent in group 10 than in the other two groups.

CONCLUSION

Oxytocin infusions at 5 IU/h and 10 IU/h are more effective in reducing blood loss and preventing PPH than 2.5 IU/h. The dose of 10 IU/h, although the most efficacious, is associated with a high incidence of side effects. Hence, further studies are needed to find out the optimal maintenance infusion rate of oxytocin during cesarean section in laboring patients who have received oxytocin earlier.

Prophylactic Phenylephrine Increases the Dose Requirement of Oxytocin to Treat Uterine Atony During Cesarean Delivery: A Double-Blinded, Single-Center, Randomized and Placebo-Controlled Trial

Purpose: Studies involving mouse models and human uterine smooth muscle cells have shown that phenylephrine inhibits uterine contractions in non-pregnant mice and human in vitro cell via cyclic adenosine monophosphate (cAMP) signaling. However, there has been no limited exploration to date of the effect of phenylephrine on uterine contractions in clinical practice. This study aimed to compare the dose requirement of oxytocin with or without the infusion of prophylactic phenylephrine to prevent post spinal hypotension during cesarean delivery under combined spinal and epidural anesthesia.

Methods: This was a double-blinded, single-center, randomized, control study. One hundred and sixty pregnant patients provided informed consent and were randomly allocated to the phenylephrine (phenylephrine infusion) and control (saline infusion) groups. Patients randomized to the phenylephrine group received an intravenous prophylactic phenylephrine infusion at a fixed rate of 0.5 μg/kg/min. The control group received a saline placebo at the same rate and used the same apparatus for delivery. After neonatal delivery and clamping of the umbilical cord, patients received a standard institutional oxytocin protocol. The primary outcome measure was the total dose of oxytocin administered during CD. Secondary outcomes including the proportion (%) of patients requiring a secondary uterotonic agent and estimated blood loss (EBL) in the first 24 h after surgery.

Results: The median oxytocin dose administered was significantly higher in the phenylephrine group than in the control group [6.9 ± 2.5 international standardized units (IU) vs. 5.4 ± 2.4 IU, p = 0.0004]. The number of patients that required a secondary uterotonic agent was significantly higher in the phenylephrine group than in the control group (24.2% vs. 9.1%; p = 0.034). The EBL in the first 24-h postoperatively was similar between the two groups (467 ± 47 ml vs. 392 ± 38 ml; p = 0.22).

Conclusions: Prophylactic infusion of phenylephrine used to prevent post-spinal hypotension during CD was associated with a higher dose of oxytocin. This has important clinical implications, as the suboptimal use of oxytocin is associated with an increased risk of postpartum hemorrhage and increased maternal morbidity and mortality. Further studies are now needed to confirm these findings.

The Intraoperative Median Effective Dose of Oxytocin for Preventing Uterine Atony in Parturients with a Prior History of Caesarean Delivery

BACKGROUND AND OBJECTIVE

While oxytocin is commonly used for the prevention of uterine atony, its pharmacology may be affected by a prior history of caesarean delivery. The objective of this study was to determine the 50% effective dose (ED₅₀) of bolus oxytocin after caesarean delivery in parturients with and without prior caesarean delivery.

METHODS

This was a parallel-group, double-blind, dose-response study using Dixon's up-and-down sequential allocation method to estimate the ED₅₀ of bolus-administered oxytocin in parturients having caesarean delivery under combined spinal-epidural anaesthesia (CSE). Twenty-seven parturients with a history of prior caesarean delivery (With-PCD group) and 26 parturients with no such history (Without-PCD group) were enrolled. Oxytocin was administered as an intravenous bolus at a starting dose of 0.5 units, which was then increased or decreased by 0.25 units at a time. Uterine tone was assessed by the obstetrician as either 'adequate' or 'inadequate' 3 min after delivery of the fetus. Adverse effects, administration of additional uterotonic agents, and estimated blood loss were recorded.

RESULTS

The ED₅₀ of oxytocin was greater in the With-PCD group than in the Without-PCD group (0.95 units [95% CI 0.82-1.08] vs. 0.55 units [95% CI 0.38-0.73], P < 0.001). The overall incidence of adverse effects was higher in the With-PCD group than in the Without-PCD group (33.3% vs. 7.7%, P = 0.02).

CONCLUSION

The initial bolus dose of oxytocin needed to prevent uterine atony was higher in parturients with prior caesarean delivery than in parturients without prior caesarean delivery. Uterine scarring may contribute to the increased oxytocin requirements of the former group.

TRIAL REGISTRATION NUMBER

ChiCTR1900023474; investigator: Wei CN; date of registration: 30 May 2019.

Maternal outcomes before and after new oxytocin protocol at cesarean delivery

OBJECTIVE

The primary objective was to describe the incidence of post-partum hemorrhage at cesarean delivery before and after implementation of a new high dose oxytocin protocol at Chris Hani Baragwanath Academic Hospital.

METHODS

This was a cross sectional retrospective record review 3 months before and 3 months after the implementation of a high dose oxytocin protocol. The study included all women that underwent cesarean delivery between 1 November 2016 and 30 April 2017 with a gestation of >24 weeks.

RESULTS

A total of 4604 Cesarean deliveries were performed during the study period, 2162 before the implementation of the new protocol and 2442 after. The incidence of post-partum hemorrhage was 4.8% (n = 91) in the Before group and 3.9% (n = 89) in the After group (P = 0.17). There was a 17.9% change in incidence of postpartum hemorrhage between the groups (P = 0.17). There was no significant difference in uterine atony between the Before and After groups (21.8% and 30.1%, P = 0.30).

CONCLUSION

There was no difference in the incidence of postpartum hemorrhage at cesarean delivery after the implementation of a high dose oxytocin protocol.

Intravenous oxytocin dosing regimens for postpartum hemorrhage prevention following cesarean delivery: a systematic review and meta-analysis

OBJECTIVE

To compare the available evidence on intravenous oxytocin dosing regimens for the prevention of postpartum hemorrhage following cesarean delivery.

DATA SOURCES

We searched Ovid MEDLINE, Embase, Global Index Medicus, Cumulative Index of Nursing and Allied Health Literature, Cochrane Controlled Register of Trials, ClinicalTrials.gov, and the International Clinical Trials Registry Platform for eligible studies published until February 2020.

STUDY ELIGIBILITY CRITERIA

We included any randomized or nonrandomized study published in peer-reviewed journals that compared at least 2 different dosing regimens of intravenous oxytocin for postpartum hemorrhage prevention in women undergoing cesarean delivery.

METHODS

Two authors independently assessed the eligibility of studies, extracted the data, and assessed the risk of bias. The primary outcome was incidence of postpartum hemorrhage ≥1000 mL. Other review outcomes included use of additional uterotonics, blood loss, and adverse maternal events. Data were analyzed according to the type of intravenous administration (bolus only, infusion only, or bolus plus infusion) and total oxytocin dose. A meta-analysis was performed on randomized trials and the results were reported as risk ratios or mean differences with 95% confidence intervals. The Grading of Recommendations, Assessment, Development, and Evaluations scale was used to rate the certainty of evidence. Findings from dose-finding trials and nonrandomized studies were reported narratively.

RESULTS

A total of 35 studies (7333 women) met our inclusion criteria and included 30 randomized trials and 5 nonrandomized studies. There were limited data available from the trials for most outcomes, and the results were not conclusive. Compared with bolus plus infusion regimens, bolus only regimens probably result in slightly higher mean blood loss (mean difference, 52 mL; 95% confidence interval, 0.4-104 mL; moderate certainty). Among the bolus plus infusion regimens, initial bolus doses <5 IU may reduce nausea (risk ratio, 0.26; 95% confidence interval, 0.11-0.63; low certainty) when compared with doses of 5-9 IU. Total oxytocin doses of 5-9 IU vs total doses of 10-19 IU may increase the use of additional uterotonics (risk ratio, 13.00; 95% confidence interval, 1.75-96.37; low certainty). Effects on other outcomes were generally inconclusive.

CONCLUSION

There are limited data available for comparisons of IV oxytocin regimens for postpartum hemorrhage prevention following cesarean delivery. Bolus plus infusion regimens may lead to minor reductions in mean blood loss and initial bolus doses of <5 IU may minimize nausea. Bolus only regimens of 10 IU vs bolus only regimens of 5 IU may decrease the need for additional uterotonics, however, further comparative trials are required to understand the effects on other key outcomes, particularly hypotension.

Refractory uterine atony: still a problem after all these years

Postpartum hemorrhage is a leading cause of maternal morbidity and mortality, and uterine atony is the leading cause of postpartum hemorrhage. Risk factors for uterine atony include induced or augmented labor, preeclampsia, chorio-amnionitis, obesity, multiple gestation, polyhydramnios, and prolonged second stage of labor. Although a risk assessment is recommended for all parturients, many women with uterine atony do not have risk factors, making uterine atony difficult to predict. Oxytocin is the first-line drug for prevention and treatment of uterine atony. It is a routine component of the active management of the third stage of labor. An oxytocin bolus dose as low as 1 IU is sufficient to produce satisfactory uterine tone in almost all women undergoing elective cesarean delivery. However, a higher bolus dose (3 IU) or infusion rate is recommended for women undergoing intrapartum cesarean delivery. Carbetocin, available in many countries, is a synthetic oxytocin analog with a longer duration than oxytocin that allows bolus administration without an infusion. Second line uterotonic agents include ergot alkaloids (ergometrine and methylergonovine) and the prostaglandins, carboprost and misoprostol. These drugs work by a different mechanism to oxytocin and should be administered early for uterine atony refractory to oxytocin. Rigorous studies are lacking, but methylergonovine and carboprost are likely superior to misoprostol. Currently, the choice of second-line agent should be based on their adverse effect profile and patient comorbidities. Surgical and radiologic management of uterine atony includes uterine tamponade using balloon catheters and compression sutures, and percutaneous transcatheter arterial embolization.

The risk of postpartum hemorrhage when lowering the oxytocin dose in planned cesarean section, a pilot study

OBJECTIVES

Oxytocin is the drug of choice in preventing postpartum hemorrhage (PPH). The aim was to compare the peroperative- and total blood loss within two hours and PPH after planned cesarean section (CS) when receiving 2.5 IU vs 5.0 IU of oxytocin in different risk groups for PPH.

STUDY DESIGN

A pilot study including 927 women undergoing planned CS where women receiving 2.5 IU of oxytocin were compared to women receiving 5.0 IU of oxytocin.

MAIN OUTCOME MEASURES

Data comparing peroperative blood loss, total blood loss within two hours and PPH were analyzed.

RESULTS

The women receiving 2.5 IU of oxytocin had a slightly higher peroperative blood loss, compared to the 5.0 IU group (476 ml vs 426 ml, p = 0.029). The total blood loss two hours after surgery showed no significant difference between the groups (626 ml vs 595 ml, p = 0.230). In the 2.5 IU group 13% had a blood loss ≥ 1000 ml vs 10% in the 5 IU group (aOR 1.64, 95% CI = 1.05-2.56). When the women considered to be at high risk for postpartum hemorrhage were excluded, we found no difference in the likelihood for postpartum hemorrhage between the groups (aOR 1.13, 95% CI = 0.64-1.99).

CONCLUSIONS

Women undergoing planned CS and receiving 2.5 IU of oxytocin had a slightly higher risk for postpartum hemorrhage in this study. However, a lower dose of 2.5 IU of oxytocin seems to be a safe option in planned CS for women without known risk factors for postpartum hemorrhage, but further research is needed to confirm these findings.

Prophylactic Dose of Oxytocin for Uterine Atony during Caesarean Delivery: A Systematic Review

Objective-to overview, compare and generalize results of randomized clinical trials analyzing different oxytocin doses to prevent postpartum hemorrhage, initiate and maintain uterine contraction after Caesarean delivery. Methods-'PubMed', 'EMBASE', 'CENTRAL', and 'CINAHL' electronic databases were searched for clinical trials analyzing the effectiveness of different dose of oxytocin given intravenously during surgery for uterine contraction and to reduce postpartum hemorrhage. A systematic review of relevant literature sources was performed. Results-our search revealed 813 literature sources. A total of 15 randomized clinical trials, comparing different doses of oxytocin bolus and infusion used after caesarean delivery have met the selection criteria. Conclusion-oxytocin bolus 0.5-3 UI is considered an effective prophylactic dose. Recommended effective prophylactic oxytocin infusion dose is 7.72 IU/h, but it is unanswered whether we really need a prophylactic infusion of oxytocin if we choose effective bolus dose size and rate. Adverse hemodynamic effects were observed when a 5 UI oxytocin bolus was used. However, topics such as bolus dose size, infusion dose size and requirement as well as bolus injection rate, still remain unanswered. The doses that are recommended in the guidelines of peripartum hemorrhage prophylaxis are not confirmed by randomized controlled double-blind trials and more research should cover this topic.

Efficacy of different infusion rates of oxytocin for maintaining uterine tone during elective caesarean section: A randomised double blind trial

Most research in this field has focused on finding oxytocin doses for initiating uterine contractions. Only limited data are available regarding the optimal rate of oxytocin infusion to maintain adequate uterine tone. This randomised, double blind study included 120 healthy term pregnant patients with uncomplicated, singleton pregnancy undergoing elective caesarean section under spinal anaesthesia. Following an initial 1 IU bolus, the patients received oxytocin infusion at 1.25 IU/hour (group 1.25), 2.5 IU/hour (group 2.5) or 5.0 IU/hour (group 5) for four hours. Uterine tone was assessed as adequate or inadequate at various intervals. If found inadequate, additional uterotonics were administered. Estimated blood loss was mean (standard deviation) 499 (172) ml, 454 (117) ml and 402 (151) ml in groups 1.25, 2.5 and 5, respectively (P value groups 1.25 versus 5 = 0.012). Oxytocin infusion at 5 IU/hour resulted in a significantly lower incidence of minor postpartum haemorrhage, defined as blood loss greater than 500 ml, than 1.25 IU/hour (P = 0.009). No patient had major/severe haemorrhage (>1000 ml blood loss). No significant difference was seen in haemoglobin levels (P = 0.677) and uterine tone. Fifteen, six and nine patients, respectively, required additional oxytocin (P = 0.151). The incidence of tachycardia (P = 0.726), hypotension (P = 0.321) and nausea/vomiting (P = 0.161) was comparable. To conclude, 5 IU/hour was more effective than 1.25 IU/hour in reducing total blood loss and the incidence of minor postpartum haemorrhage. Thus 5 IU/hour appears to be an optimal oxytocin infusion rate following 1 IU slow intravenous oxytocin injection for the maintenance of adequate uterine contraction in patients undergoing elective caesarean section under spinal anaesthesia.

Arg-Vasotocin Directly Activates Isotocin Receptors and Induces COX2 Expression in Ovoviviparous Guppies

Oxytocin (OT) is a crucial regulator of reproductive behaviors, including parturition in mammals. Arg-vasopressin (AVP) is a nonapeptide homologous to Arg-vasotocin (AVT) in teleosts that has comparable affinity for the OT receptor. In the present study, ovoviviparous guppies (Poecilia reticulata) were used to study the effect of AVT on delivery mediated by the activation of prostaglandin (PG) biosynthesis via isotocin (IT) receptors (ITRs). One copy each of it and avt and two copies of itrs were identified in guppies. The results of the affinity assay showed that various concentrations of AVT and IT (10^-6, 10^-7, and 10^-8 mol/L) significantly activated itr1 (P < 0.05). In vitro experiments revealed significant upregulation (P < 0.05) of cyclooxygenase 2 (cox2), which is the rate-limiting enzyme involved in PG biosynthesis, and itr1 by AVT and IT. Furthermore, dual in situ hybridization detected positive signals for itr1 and cox2 at the same site, implying that ITR1 may regulate cox2 gene expression. Measurement of prostaglandin F_2a (PGF_2a) concentrations showed that AVT induced PGF_2a synthesis (P < 0.05) and that the effect of IT was not significant. Finally, intraperitoneal administration of PGF_2a significantly induced premature parturition of guppies. This study is the first to identify and characterize AVT and ITRs in guppies. The findings suggest that AVT promotes PG biosynthesis via ITR and that PGF_2a induces delivery behavior in ovoviviparous guppies.

The Median Effective Dose of Oxytocin Needed to Prevent Uterine Atony During Cesarean Delivery in Elderly Parturients

Purpose

Oxytocin is the first-line agent to prevent and treat uterine atony during cesarean delivery (CD). We compared the effective dose in 50% of the parturients (ED₅₀) of a prophylactic oxytocin bolus during CD in young (<35 years) and old parturients (≥35 years) using Dixon’s up-and-down method.

Patients and Methods

Twenty-eight young parturients (young group) and 25 old parturients (old group) undergoing CD under combined spinal-epidural anesthesia were enrolled. The initial oxytocin bolus was 0.5 IU, with increments or decrements of 0.25 IU. Maternal adverse effects, requirement for additional uterotonic agents, and estimated blood loss were recorded.

Results

The ED₅₀ for oxytocin in the old group was higher than that in the young group (1.41 IU; 95% confidence interval, 0.63–2.19) vs 0.66 IU (0.04–1.29), P < 0.001). The total oxytocin dose in the old group was higher than in the young group (5.9 ± 2.9 vs 4.1 ± 2.1 IU, P = 0.01). The estimated blood loss in the older group and young group was 401.2 ± 204.5 mL and 289.3 ± 104.6 mL, respectively (P =0.01). The overall prevalence of adverse effects was higher in the old group than in the young group (68.0% vs 21.4%, P < 0.001).

Conclusion

The initial bolus and total requirement of oxytocin for preventing uterine atony were higher in old parturients than in young parturients during CD. Advanced maternal age may necessitate higher doses of oxytocin.

The ED50 and ED95 of oxytocin infusion rate for maintaining uterine tone during elective caesarean delivery: a dose-finding study

Background

The 90% effective dose (ED₉₀) of oxytocin infusion has been previously estimated to be 16.2 IU h^− 1. However, bolus administration of oxytocin prior to the infusion may decrease the infusion dose required. The aim of this study was to estimate the ED₉₅ for oxytocin infusion after a bolus at elective caesarean delivery (CD) in nonlaboring parturients.

Methods

We performed a randomized, triple blinded study in 150 healthy termparturients scheduled for elective CD under epidural anaesthesia. After delivery of the infant and i.v. administration of 1 IU oxytocin as a bolus, Participants were randomized to receive oxytocin infusion at a rate of 0, 1, 2, 3, 5, or 8 IU h^− 1, to be given for a total of 1 h. Uterine tone assessed by the blinded obstetrician as either adequate or inadequate. Secondary outcomes included estimated blood loss (EBL), requirement for supplemental uterotonic agents, and development of side effects.

Results

The 95% effective dose (ED₉₅) of oxytocin infusion was estimated to be 7.72 IU h^− 1 (95% confidence interval 5.80–12.67 IU h^− 1). With increasing oxytocin infusion rate, the proportion of parturients who needed rescue oxytocin bolus or secondary uterotonic agents decreased. No significant among-group differences in the EBL and oxytocin-related side effects were observed.

Conclusions

In parturients who receive a 1 IU bolus of oxytocin during elective cesarean delivery, an infusion rate of oxytocin at 7.72 IU h^− 1 will produce adequate uterine tone in 95% of parturients. These results suggest that the total dose of oxytocin administered in the postpartum period can be decreased when administered as an infusion after oxytocin bolus.

Management of post-partum hemorrhage and the role of the obstetric anesthesiologist

PURPOSE OF REVIEW

The landscape of post-partum hemorrhage management is rapidly changing. Modifications to definitions, bundles, and care plans occur frequently with management strategies becoming more complex. It has become apparent that the management of these patients requires a multidisciplinary approach with the involvement of obstetricians, anesthesiologists, gynecologist/oncologists, nursing, and care associates. This review article is meant to be an evidence-based review of post-partum hemorrhage with practical recommendations and a look at future directions of the management of post-partum hemorrhage from the vantage point of the obstetric anesthesiologist in an effort to enhance the collaborative treatment of this at risk population.

Patients Undergoing Cesarean Delivery After Exposure to Oxytocin During Labor Require Higher Postpartum Oxytocin Doses

BACKGROUND

Experts recommend postpartum oxytocin to prevent uterine atony and hemorrhage, but oxytocin may be associated with dose-dependent adverse effects, and the correct dose of postpartum oxytocin has yet to be determined. The effective dose in 90% of patients (ED90) of oxytocin after cesarean delivery may be higher in patients exposed to oxytocin during labor compared to patients unexposed. We therefore undertook this study to compare postpartum oxytocin requirements in patients exposed to oxytocin prior to cesarean delivery versus those not exposed, when all were treated according to a specific institutional protocol.

METHODS

In this retrospective chart review, we reviewed medical records of patients who underwent cesarean delivery under neuraxial anesthesia and noted demographic data, relevant comorbidities, and oxytocin exposure, infusion rate, and duration prior to delivery. Patients exposed to oxytocin before cesarean (OXY+ group) were compared to those not exposed (OXY- group). The primary outcome variable was highest infusion rate of postpartum oxytocin required per institutional protocol. Secondary outcomes included estimated blood loss, proportion of patients with postpartum hemorrhage, and proportions who received other uterotonic medications or red blood cell transfusion.

RESULTS

OXY+ patients were more likely to be nulliparous and had higher estimated gestational age and neonatal weight than OXY- patients. They also had higher incidence of chorioamnionitis and lower incidence of multiple gestation. OXY+ patients required a high postpartum oxytocin infusion rate more often than OXY- patients (adjusted odds ratio 1.94 [95% confidence interval, 1.19-3.15; P = .008]). They also received other uterotonic agents more commonly. Estimated blood loss, hemorrhage rates, and transfusion rates did not differ between groups.

CONCLUSIONS

Reported increases in the ED90 of postpartum oxytocin after oxytocin exposure during labor appear to be clinically significant. We have therefore altered our institutional protocol so that women preexposed to oxytocin routinely receive higher initial postpartum oxytocin infusion rates.

Uterotonic drug usage in Canada: a snapshot of the practice in obstetric units of university-affiliated hospitals

OBJECTIVE

The objective of this study was to determine the pattern of uterotonic drug usage in obstetric units of university-affiliated hospitals in Canada.

METHODS

This was a prospective observational study conducted in the form of an electronic survey. The target group consisted of chiefs or directors of Obstetrics and Anaesthesia at university-affiliated hospitals across Canada. The survey was sent out between November 2016 and January 2017, using the program 'SurveyMonkey'. Data on institutional obstetric practices and usage of uterotonic agents were collected.

RESULTS

The survey was sent to 92 obstetricians and anesthesiologists from 46 institutions, of which 33 clinicians from 24 institutions responded. About 65% of clinicians were unaware of the rate of postpartum hemorrhage in their institution. The first-line agent for vaginal deliveries was reported as oxytocin by 94% and carbetocin by 6% of physicians. For women at low-risk for postpartum hemorrhage when undergoing cesarean deliveries (CD), 66% reported oxytocin as the first-line uterotonic, while 34% reported carbetocin. For CDs at high-risk of postpartum hemorrhage, 60% of physicians reported oxytocin and 40% reported using carbetocin initially. The use of second-line uterotonics was also variable. The choice of uterotonic was mainly based on perceived efficacy and Society of Obstetricians and Gynaecologists of Canada guidelines.

CONCLUSION

There is a lack of a unified approach to the use of uterotonic drugs for postpartum hemorrhage management in Canada. To improve the management of postpartum hemorrhage due to uterine atony, an evidence-based approach to usage and consensus between obstetricians and anesthesiologists is warranted.