Intrapartum oxytocin: time to focus on longer term consequences?

Protocolized oxytocin infusion for elective cesarean delivery: a retrospective before-and-after study

PURPOSE

To elucidate the clinical impact of the novel oxytocin protocol using a syringe pump with a stratified dose compared with the conventional practice of putting oxytocin into the bag.

METHODS

This is a retrospective cohort study. We collected the data of the patients who underwent elective cesarean delivery under neuraxial anesthesia between June 2019 and May 2020. The patients were allocated to two groups according to oxytocin administration methods; the control group (the attending anesthesiologist put oxytocin 5-10 units in the infusion bag and adjusted manually after childbirth) and the protocol group (the oxytocin protocol gave oxytocin bolus 1 or 3 units depending on the PPH risk, followed by 5 or 10 unit h-1 via a syringe pump). We compared the total amount of oxytocin within 24 h postpartum, estimated blood loss, and adverse clinical events within 24 h postpartum between the two groups.

RESULTS

During the study period, 262 parturients were included. Oxytocin doses of intraoperative and postoperative were significantly lower in the protocol group (9.7 vs. 11.7 units, intraoperative, 15.9 vs. 18 units, postoperative). The subgroup analyses showed that the impact was more remarkable in the low PPH risk than in the high PPH risk. The multivariate linear regression analyses also confirmed the difference. The groups had no significant difference in blood loss, requirement of additional uterotonics, and other adverse events.

CONCLUSIONS

Our oxytocin infusion protocol significantly reduced oxytocin requirements in elective cesarean delivery under neuraxial anesthesia without increasing blood loss. However, we could not find other clinical benefits of the novel protocol.

Oxytocin-induced birth causes sex-specific behavioral and brain connectivity changes in developing rat offspring

Despite six decades of the use of exogenous oxytocin for management of labor, little is known about its effects on the developing brain. Motivated by controversial reports suggesting a link between oxytocin use during labor and autism spectrum disorders (ASDs), we employed our recently validated rat model for labor induction with oxytocin to address this important concern. Using a combination of molecular biological, behavioral, and neuroimaging assays, we show that induced birth with oxytocin leads to sex-specific disruption of oxytocinergic signaling in the developing brain, decreased communicative ability of pups, reduced empathy-like behaviors especially in male offspring, and widespread sex-dependent changes in functional cortical connectivity. Contrary to our hypothesis, social behavior, typically impaired in ASDs, was largely preserved. Collectively, our foundational studies provide nuanced insights into the neurodevelopmental impact of birth induction with oxytocin and set the stage for mechanistic investigations in animal models and prospective longitudinal clinical studies.

A study of the pharmacokinetics and pharmacodynamics of oxytocin at elective caesarean delivery

Oxytocin is widely used to prevent atonic postpartum haemorrhage after caesarean delivery. Initial treatment failure rates are high and inadequate dosing may contribute. Excessive doses, however, are associated with serious adverse effects. The pharmacokinetic data from this context are sparse and there is a lack of data in the immediate postpartum minutes after an initiating bolus. The pharmacodynamic data from this context are exclusively from dose-effect studies, with some suggesting that higher doses of oxytocin are required to provide adequate uterine tone in obese compared with non-obese women. We aimed to perform a pharmacokinetic and pharmacodynamic study that would facilitate more precise weight-based oxytocin dosing. We measured arterial oxytocin concentration, uterine tone and haemodynamic parameters in 25 women in the first 40 min after exogenous oxytocin administration at elective caesarean delivery. Serum oxytocin concentrations varied considerably between individuals. We constructed a one-compartment pharmacokinetic model of exogenous oxytocin deposition, after its administration with an initiating bolus and a maintenance infusion, at elective caesarean delivery. Body weight was evaluated as a potential covariate but was not included in the model due to lack of statistically significant reduction in the objective function. We calculated the volume of distribution and clearance (mean [coefficient of variation]) as 156.1 l [18%] and 83 ml.s-1 [32%] but found no within-individual correlation between serum oxytocin concentration and uterine tone or haemodynamic parameters. In conclusion, we observed a large variation in serum oxytocin concentrations between individuals receiving similar doses of oxytocin and were unable to establish weight-based dosing of exogenous oxytocin at caesarean delivery. Our findings suggest that future studies on oxytocin pharmacokinetics would need large sample sizes. In the absence of such data, oxytocin dosing should continue to be guided by uterine tone assessments and adjusted according to a strategy based on the best evidence from dose-effect studies.

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.

Carbetocin compared with oxytocin in non-elective Cesarean delivery: a systematic review, meta-analysis, and trial sequential analysis of randomized-controlled trials

PURPOSE

Carbetocin has been shown to reduce the requirement for additional uterotonics in women exclusively undergoing elective Cesarean delivery (CD). The aim of this review was to determine whether this effect could also be demonstrated in the setting of non-elective CD.

METHODS

Medline, Embase, CINAHL, Web of Science and Cochrane databases were searched for randomized-controlled trials (RCTs) in any language comparing carbetocin to oxytocin. Studies with data on women undergoing non-elective CD, where carbetocin was compared with oxytocin, were included. The primary outcome was the need for additional uterotonics. Secondary outcomes included incidence of blood transfusion, estimated blood loss (mL), incidence of postpartum hemorrhage (PPH; > 1000 mL) and mean hemoglobin drop (g·dL^-1 RESULTS: Five RCTs were included, with a total of 1,214 patients. The need for additional uterotonics was reduced with carbetocin compared with oxytocin (odds ratio, 0.30; 95% CI, 0.11 to 0.86; I², 90.60%). Trial sequential analysis (TSA) confirmed that the information size needed to show a significant reduction in the need for additional uterotonics had been exceeded. No significant differences were shown with respect to any of the secondary outcomes, but there was significant heterogeneity between the studies.

CONCLUSIONS

Carbetocin reduces the need for additional uterotonics in non-elective CD compared with oxytocin. TSA confirmed that this analysis was appropriately powered to detect the pooled estimated effect. Further trials utilizing consistent core outcomes are needed to determine an effect on PPH.

TRIAL REGISTRATION

PROSPERO CRD42019147256, registered 13 September 2019.

A Nonpeptide Oxytocin Receptor Agonist for a Durable Relief of Inflammatory Pain

Oxytocin possesses several physiological and social functions, among which an important analgesic effect. For this purpose, oxytocin binds mainly to its unique receptor, both in the central nervous system and in the peripheral nociceptive terminal axon in the skin. However, despite its interesting analgesic properties and its current use in clinics to facilitate labor, oxytocin is not used in pain treatment. Indeed, it is rapidly metabolized, with a half-life in the blood circulation estimated at five minutes and in cerebrospinal fluid around twenty minutes in humans and rats. Moreover, oxytocin itself suffers from several additional drawbacks: a lack of specificity, an extremely poor oral absorption and distribution, and finally, a lack of patentability. Recently, a first non-peptide full agonist of oxytocin receptor (LIT-001) of low molecular weight has been synthesized with reported beneficial effect for social interactions after peripheral administration. In the present study, we report that a single intraperitoneal administration of LIT-001 in a rat model induces a long-lasting reduction in inflammatory pain-induced hyperalgesia symptoms, paving the way to an original drug development strategy for pain treatment.