Carbetocin at elective caesarean section: a sequential allocation trial to determine the minimum effective dose in obese women

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.

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.

Weight-based versus fixed dose oxytocin infusion for preventing uterine atony during cesarean section in laboring patients: A randomized trial

OBJECTIVE

We compared efficacy of weight-based (0.4 IU/kg/h) versus fixed-dose (34 IU/h) oxytocin infusion during cesarean section.

METHODS

The oxytocin infusion in either group (n = 32 each) was initiated upon cord clamping. Primary outcome measure was adequacy of uterine tone at 4 min after initiating oxytocin infusion. Oxytocin associated side effects were also observed.

RESULTS

Significantly less oxytocin was used with the weight-based versus fixed-dose regimen (16.3 [11.2-22.4] IU vs 20.4 [15.8-26.9] IU; P = 0.036). Incidence of adequate uterine tone was clinically greater but not significantly different with the weight-based versus fixed-dose regimen (81.3% vs 71.9%; P = 0.376). The weight-based regimen was associated with clinically lesser, although not statistically significant need for rescue oxytocin (25% vs 46.9%; P = 0.068) and additional uterotonic (9.4% vs 15.6%; P = 0.708); as well as oxytocin associated side effects (hypotension [34.4% vs 46.9%; P = 0.309], nausea/vomiting [18.8% vs 40.6%; P = 0.055], and ST-T changes [0% vs 3.1%; P = 1.000]).

CONCLUSION

Weight-based oxytocin was not significantly different from the fixed-dose regimen in terms of uterotonic efficacy or associated side-effects, despite significantly lower doses being used. Use of weight-based oxytocin infusion (0.4 IU/kg/h) can be considered in clinical practice.

TRIAL REGISTRATION

Clinical Trial Registry of India (ctri.nic.in, number. CTRI/2021/01/030642).

Uterotonics, magnesium sulphate and antibiotics during childbirth and peripartum: Important obstetric drugs for the anaesthesiologist

The main causes of maternal mortality are comorbidities, hypertensive pregnancy syndrome, obstetric haemorrhage, and maternal sepsis. For this reason, uterotonics, magnesium sulphate, and antibiotics are essential tools in the management of obstetric patients during labour and in the peripartum period. These drugs are widely used by anaesthesiologists in all departments, and play a crucial role in treatment and patient safety. For the purpose of this narrative review, we performed a detailed search of medical databases and selected studies describing the use of these drugs in patients during pregnancy, delivery and the pospartum period. Uterotonics, above all oxytocin, play an important role in the prevention and treatment of pospartum haemorrhage, and various studies have shown that in obstetric procedures, such as scheduled and emergency caesarean section, they are effective at lower doses than those hitherto accepted. We also discuss the use of carbetocin as an effective alternative that has a therapeutic advantage in certain clinical circumstances. Magnesium sulphate is the gold standard in the prevention and treatment of eclampsia, and also plays a neuroprotective role in preterm infants. We describe the precautions to be taken during magnesium administration. Finally, we discuss the importance of understanding microbiology and the pharmacology of antibiotics in the management of obstetric infection and endometritis, and draw attention to the latest trends in antibiotic regimens in labour and caesarean section.

The minimum effective dose (ED90) of prophylactic oxytocin infusion during cesarean delivery in patients with and without obesity: an up-down sequential allocation dose-response study

BACKGROUND

Obesity is associated with greater oxytocin requirement during labor induction or augmentation. There are scant data exploring the intra-operative requirement during cesarean delivery in patients with obesity, and none comparing it with those without obesity. We evaluated the minimum effective dose (ED90) of an oxytocin infusion to achieve adequate uterine tone during cesarean delivery in patients with and without obesity.

METHODS

Patients (body mass index ≥30 kg/m2 represented patients with obesity) undergoing cesarean delivery using subarachnoid block were included. This prospective dual-arm dose-finding study used a 9:1 biased sequential allocation design. Oxytocin infusion was initiated at 13 IU/h at cord clamping in the first patient of each group. Uterine tone was graded as satisfactory or unsatisfactory by the obstetrician four minutes after initiation of the infusion. The dose of oxytocin infusion for subsequent patients was determined according to the response of the previous patient in the group. Oxytocin-associated side effects were evaluated. Dose-response data for the groups was evaluated using log-logistic function and ED90 estimates derived from fitted equations using the delta method.

RESULTS

The ED90 of oxytocin was significantly higher for patients with obesity (n = 40) compared with those without obesity (n = 40) [25.7 IU/h, 95% CI 18.6 to 32.9) vs. 16.6 IU/h, 95% CI 14.9 to 18.3)]; relative ratio 1.55 [95% CI 1.09 to 2.01] (P = 0.019).

CONCLUSIONS

Patients with obesity require a higher intra-operative oxytocin infusion dose rate to achieve a satisfactorily contracted uterus after fetal delivery when compared with patients without obesity.

The optimal oxytocin infusion rate for preventing uterine atony during cesarean delivery in elderly parturients with prior history of cesarean delivery

Background: An estimate of 90% effective dose (ED90) of oxytocin infusion has already been proved effective in non-laboring parturients. However, the requirements of oxytocin for elderly parturients with prior history of cesarean delivery (CD) may be higher. The aim of this study was to find the optimum oxytocin infusion rate for preventing uterine atony during CD in elderly parturients with prior history of CD. Method: We performed a randomized, double-blinded study in 120 healthy elderly parturients with prior history of CD scheduled for elective CD under combined spinal-epidural (CSE) anesthesia. Participants were treated with oxytocin infusion randomly at the rates of 0, 4, 8, 12, 16, or 20 IU h-1 after the delivery of infants. Following oxytocin administration, a blinded obstetrician evaluated the uterine tone (UT), verbally describing it using numerical scales (0-10: 0, no UT; 10, optimal UT) as either adequate or inadequate at the time intervals of 3, 6, and 9 min. Maternal adverse effects, requirements for additional uterotonic agents, delivery-placenta delivery time (PD), and estimated blood loss (EBL) were recorded. Results: The 50% effective dose (ED50) and 90% effective dose (ED90) of oxytocin infusion were 14.6 IU h-1 (95% confidence interval 12.0-18.4 IU h-1) and 27.7 IU h-1 (95% confidence interval 22.5-39.4 IU h-1), respectively. As the rate of infusion was increased in parturients, the rescue oxytocin dose and delivery-PD time were decreased. Parturients who received 0 IU h-1 oxytocin at 3, 6, and 9 min obtained lower UT scores than those who received 16 and 20 IU h-1 oxytocin (p < 0.05, respectively). No significant differences were observed among groups in EBL and maternal adverse effects. Conclusion: The infusion rate of oxytocin at 14.57 and 27.74 IU h-1 produces adequate UT in 50% and 90% of elderly parturients with prior history of CD, respectively. An oxytocin infusion rate of 27.7 IU h-1 is suggested to be the optimal dose for preventing uterine atony during CD in elderly parturients with prior history of cesarean delivery. Clinical Trial Registration: [https://www.chictr.org.cn/bin/project/edit?pid=62489], Identifier: [ChiCTR2000038891].

The 50% and 95% effective doses of remimazolam tosilate with adjuvant sufentanil for sedation in patients with liver cirrhosis undergoing oesophagogastric varices screening endoscopy

WHAT IS ALREADY KNOWN AND OBJECTIVE

Sedation is routinely provided for patients undergoing gastrointestinal endoscopy. Remimazolam tosilate is a novel and short-acting sedative agent that has been used for sedation during endoscopic procedures. The optimal dose of remimazolam in gastrointestinal endoscopy for patients with liver cirrhosis has not been elucidated.

BACKGROUND

To determine the effective dose of remimazolam tosilate with adjuvant sufentanil for sedation in patients with liver cirrhosis undergoing oesophagogastric varices screening endoscopy.

MATERIAL AND METHODS

Patients aged 18-65 years with liver cirrhosis undergoing screening endoscopy for oesophagogastric varices were recruited. Sufentanil 0.15 μg/kg was given intravenously at 2 min before administration of remimazolam tosilate. The initial dose of remimazolam was 0.1 mg/kg and adjusted by 0.025 mg/kg as a step size, based on the Dixon and Massay up-and-down sequential method. Inclusion of patients was stopped after eight crossovers and the calculated median effective dose (ED₅₀ ) of remimazolam for successful endoscopy was obtained by calculating the mean of midpoint of all crossovers. Furthermore, a probit regression was applied to establish the dose-response curve of remimazolam and further assess the 95% effective dose (ED₉₅ ) of remimazolam.

RESULTS

The calculated ED₅₀ of remimazolam for successful endoscopy using the mean of midpoint of all crossovers was 0.097 mg/kg (95% CI, 0.004-0.099 mg/kg). Using the probit regression analysis, the ED₅₀ and ED₉₅ of remimazolam for successful endoscopy was 0.097 mg/kg (95% CI, 0.004-0.099 mg/kg) and 0.107 mg/kg (95% CI, 0.103-0.336 mg/kg), respectively. No adverse events were observed throughout the study period.

CONCLUSIONS

This pilot study suggests that the ED₅₀ and ED₉₅ of remimazolam tosilate with adjuvant sufentanil for sedation in liver cirrhosis patients undergoing oesophagogastric varices screening endoscopy was 0.097 and 0.107 mg/kg, respectively.

Is there a role for carbetocin in the prophylaxis of postpartum obstetric haemorrhage?

Postpartum haemorrhage is a common complication of pregnancy, most commonly due to uterine atony. Uterotonics have a vital role in preventing postpartum haemorrhage but the choice of the most effective agent with the fewest adverse effects is a subject of debate. Carbetocin, a synthetic analogue of oxytocin has been available in the UK since 2007 but is not currently widely used. It has a longer duration of action than oxytocin, which avoids the need for an infusion and as it is heat-stable it can be stored at room temperature. Current UK clinical guidelines, based on the results of older meta-analyses, do not recommend carbetocin as a first-line agent. A Cochrane review, published in 2018, ranked carbetocin in the top three drug regimens for preventing postpartum haemorrhage and an international consensus statement on uterotonic use for caesarean birth concluded that carbetocin may become the preferred drug for caesarean birth, by reducing the need for additional uterotonics. The higher cost of carbetocin when compared with oxytocin is a limiting factor, but the significant healthcare costs of a postpartum haemorrhage and the physiological impact of this event suggests it a reasonable alternative to consider, especially if ergometrine is contraindicated or in those who are undergoing a caesarean birth or are at high risk of bleeding.

Carbetocin vs. oxytocin at elective caesarean delivery: a double-blind, randomised, controlled, non-inferiority trial of low- and high-dose regimens

Carbetocin or oxytocin are given routinely as first-line uterotonic drugs following delivery of the neonate during caesarean delivery to prevent postpartum haemorrhage. Low doses may be as effective as high doses with a potential reduction in adverse effects. In this double-blind, randomised, controlled, non-inferiority trial, we assigned low-risk patients undergoing elective caesarean delivery under spinal anaesthesia to one of four groups: carbetocin 20 μg; carbetocin 100 μg; oxytocin 0.5 IU bolus + infusion; and oxytocin 5 IU bolus + infusion. The study drug was given intravenously after delivery of the neonate. Uterine tone was assessed by the obstetrician 2, 5 and 10 minutes after study drug administration according to an 11-point verbal numerical rating scale (0 = atonic, 10 = excellent tone). The primary outcome measure was uterine tone 2 min after study drug administration. The pre-specified non-inferiority margin was 1.2 points on the 11-point scale. Secondary outcomes included uterine tone after 5 and 10 minutes, use of additional uterotonics, blood loss and adverse effects. Data were available for 277 patients. Carbetocin 20 μg resulting in uterine tone of (median (IQR [range])) 8 (7-8 [1-10]) was non-inferior to carbetocin 100 μg with tone 8 (7-9 [3-10]), median (95%CI) difference 0 (-0.44-0.44). Similarly, oxytocin 0.5 IU with tone 7 (6-8 [3-10]) was non-inferior to oxytocin 5 IU with tone 8 (6-8 [2-10]), median (95%CI) difference 1 (0.11-1.89). Carbetocin 20 μg was also non-inferior to oxytocin 5 IU, and oxytocin 0.5 IU was non-inferior to carbetocin 100 μg. Uterine tone after 5 and 10 minutes, use of additional uterotonics, blood loss and adverse effects were similar in all groups.

The Impact of Obesity on the Management and Outcomes of Postpartum Hemorrhage

OBJECTIVE

The study aimed to evaluate the impact of obesity on the management and outcomes of postpartum hemorrhage.

STUDY DESIGN

We conducted a retrospective cohort study of women who delivered at a tertiary care center between February 1, 2013 and January 31, 2014 and experienced a postpartum hemorrhage. Charts were reviewed for clinical and sociodemographic data, and women were excluded if the medical record was incomplete. Hemorrhage-related severe morbidity indicators included blood transfusion, shock, renal failure, transfusion-related lung injury, cardiac arrest, and use of interventional radiology procedures. Obese (body mass index [BMI] ≥ 30 kg/m²) and nonobese women were compared. Data were analyzed using Chi-square, Student's t-test, Mann-Whitney U test, and linear regression where appropriate. The p-value <0.05 was significant.

RESULTS

Of 9,890 deliveries, 2.6% (n = 262) were complicated by hemorrhage. Obese women were more likely to deliver by cesarean section (55.5 vs. 39.8%, p = 0.016), undergo a cesarean after labor (31.1 vs. 12.2%, p = 0.001), and have a higher quantitative blood loss (1,313 vs. 1,056 mL, p = 0.003). Both groups were equally likely to receive carboprost, methylergonovine, and misoprostol, but obese women were more likely to receive any uterotonic agent (95.7 vs. 88.9%, p = 0.007) and be moved to the operating room (32.3 vs. 20.4, p = 0.04). There was no difference in the use of intrauterine pressure balloon tamponade, interventional radiology, or decision to proceed with hysterectomy. The two groups were similar in time to stabilization. There was no difference in the need for blood transfusion. Obese women required more units of blood transfused (2.2 ± 2 vs. 2 ± 5 units, p = 0.023), were more likely to have any hemorrhage-related severe morbidity (34.1 vs. 25%, p = 0.016), and more than one hemorrhage related morbidity (17.1 vs. 7.9, p = 0.02). After controlling for confounding variables, quantitative blood loss, and not BMI was predictive of the need for transfusion.

CONCLUSION

Despite similar management, obese women were more likely to have severe morbidity and need more units of blood transfused.

KEY POINTS

· Obese women were more likely to have a higher quantitative blood loss and require more units of blood transfused.. · Obese women were more likely to experience any hemorrhage-related severe morbidity.. · Although obese women were more likely to be moved to the operating room for intervention, the rates of intrauterine pressure balloon tamponade, interventional radiology or hysterectomy were the same for obese and non-obese women..

Risk Factors for Carbetocin Failure after a Cesarean Section: Is Obesity One of Them?

Obese pregnant women have increased rates of fetal macrosomia, long labor, and cesarean sections, which lead to an increased risk of postpartum hemorrhage (PPH). Carbetocin is useful for the prevention of PPH after a cesarean section. Our study aimed to investigate predictors of carbetocin failure after a cesarean section, and specifically whether obesity is associated with carbetocin failure. We retrospectively analyzed all women who received carbetocin after a cesarean section. Carbetocin failure was defined as changes in hematocrit and hemoglobin, blood loss ≥ 1000 mL, and the need for an additional uterotonic agent or second-line therapies for persistent PPH. Univariate and multivariate analyses were performed to investigate predictors of carbetocin failure. The study included 600 women, with 131 (21.8%) obese women. Overall, 44 (7.3%) carbetocin failures were reported, and rates of obese women were similar between groups (carbetocin failure, 11.4% vs. 22.9%; p = 0.08). Previous PPH (p < 0.001), a cesarean section during labor (p = 0.01), cervical ripening (p = 0.02), and birthweight (p = 0.01) were significantly different between groups. In the multivariable logistic regression analysis adjusted for potential confounders, cervical ripening (adjusted odds ratio (OR) 2.23, 95% confidence interval (CI) 1.01–4.80), compared with spontaneous labor, was significantly associated with carbetocin failure. Obesity was not associated with carbetocin failure after cesarean sections.

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.

Oxytocin at elective caesarean delivery: a dose-finding study in women with obesity

Prophylactic oxytocin administration at the third stage of labour reduces blood loss and the need for additional uterotonic drugs. Obesity is known to be associated with an increased risk of uterine atony and postpartum haemorrhage. It is unknown whether women with obesity require higher doses of oxytocin in order to achieve adequate uterine tone after delivery. The purpose of this study was to establish the bolus dose of oxytocin required to initiate effective uterine contraction in 90% of women with obesity (the ED₉₀ ) at elective caesarean delivery. We conducted a double-blind dose-finding study using the biased coin up-down design method. Term pregnant women with a BMI ≥ 40 kg.m^-2 undergoing elective caesarean delivery under regional anaesthesia were included. Those with conditions predisposing to postpartum haemorrhage were not included. Oxytocin was administered as an intravenous bolus over 1 minute upon delivery of the fetus. With the first woman receiving 0.5 IU, oxytocin doses were administered according to a sequential allocation scheme. The primary outcome measure was satisfactory uterine tone, as assessed by the operating obstetrician 2 minutes after administration of the oxytocin bolus. Secondary outcomes included the need for rescue uterotonic drugs, adverse effects and estimated blood loss. We studied 30 women with a mean (SD) BMI of 52.3 (7.6) kg.m^-2 . The ED₉₀ for oxytocin was 0.75 IU (95%CI 0.5-0.93 IU) by isotonic regression and 0.78 IU (95%CI 0.68-0.88 IU) by the Dixon and Mood method. Our results suggest that women with a BMI ≥ 40 kg.m^-2 require approximately twice as much oxytocin as those with a BMI < 40 kg.m^-2 , in whom an ED₉₀ of 0.35 IU (95%CI 0.15-0.52 IU) has previously been demonstrated.