Effect of Carbetocin on Uterine Tone during Cesarean Section: A Comparison between Subarachnoid Block and General Anesthesia

Background

Postpartum hemorrhage remains a challenge in obstetric practice in developing climes and contributes immensely to the horrendous figures of maternal mortality worldwide.

Aim

The aim was to compare the effect of intravenous (IV) carbetocin on uterine tone under different anesthetic techniques for elective cesarean section.

Methods

Four hundred and seventy-eight consecutive women scheduled for elective cesarean section were recruited into two groups by convenience. While 445 parturients received subarachnoid block (SAB), 33 had general anesthesia (GA). At delivery, IV carbetocin was administered. The uterine tone was assessed manually and blood loss from intraoperative period to the 24th h was determined. Other variables such as hemodynamic profiles and Apgar scores were determined and recorded.

Results

The bio-characteristics between the two groups were essentially the same in terms of age, weight, height, body mass index, preoperative hemoglobin, and gestational age. While the response to the administered carbetocin was slower in the GA group, there was no need for additional dose. The mean estimated intraoperative blood loss under SAB was 250.44 ± 50.59 ml and that under GA was 470.89 ± 35.70 ml, P = 0.000000. The ephedrine consumption was 6.25 ± 2.05 mg in the SAB group while it was 11.25 ± 2.49 mg, P = 0.000000. There was no further maternal blood loss observed after the intraoperative period until the end of 24-h period. The hemodynamic profiles were significantly different in terms of mean systolic blood pressure, mean diastolic blood pressure, and mean arterial blood pressure, P = 0.006, P = 0.002, and P = 0.003, respectively. However, the difference in the mean heart rate was not statistically significant, P = 0.304. While the Apgar scores between groups were not statistically significant, the mean umbilical pH was 7.34 ± 0.09 in the SAB group, it was 7.35 ± 0.02 in the GA group, P = 0.071.

Conclusion

Intraoperative maternal blood loss was more among the parturients who received GA than subarachnoid blood. This could probably be due to the effect of the halogenated vapor used for the GA on the uterine tone. There was no further blood loss after the intraoperative period. The hemodynamic profile was better under SAB as evidenced by the total ephedrine consumption.

Weight-based oxytocin infusion for preventing uterine atony during caesarean delivery in non-labouring patients: A dose-response study

Postpartum haemorrhage remains a significant cause of maternal morbidity and mortality with the commonest reason being uterine atony. For prevention of uterine atony during caesarean delivery, oxytocin is advocated as a first line drug. There is however no published data regarding utility of a weight-based oxytocin infusion. The present study evaluated dose-response relationship for oxytocin infusion when used as weight-based regimen. A total of 55 non-labouring patients without risk factors for uterine atony and scheduled for caesarean delivery under spinal anaesthesia were enrolled. Randomization was done to receive oxytocin infusion in a dose of 0.1, 0.15, 0.2, 0.25 or 0.3 IU kg^-1  h^-1 (n = 11 each), initiated at the time of cord clamping and continued until the end of surgery. Successful outcome was defined as attaining an adequate uterine response at 4 min of initiation of infusion and maintained till end of surgery. Oxytocin associated hypotension, tachycardia, ST-T changes, nausea/vomiting, flushing and chest pain were also observed. A significant linear trend for adequate intraoperative uterine tone was seen with increasing dose of weight-based oxytocin infusion (P < 0.001). The effective dose in 90% population (ED90) was 0.29 IU kg^-1  h^-1 (95% CI = 0.25-0.42). Amongst the oxytocin associated side effects, a significant linear trend was seen between increasing dose of oxytocin infusion and hypotension as well as nausea/vomiting (p = 0.016 and 0.023 respectively). Thus, oxytocin infusion during caesarean delivery may be used as per the patient's body weight.

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 interrater reliability and agreement of a 0 to 10 uterine tone score in cesarean delivery

BACKGROUND

Postpartum hemorrhage is a leading source of maternal morbidity and mortality worldwide with uterine atony identified as the underlying cause in up to 80% of cases. Several measures have been utilized to report uterine tone. The most commonly reported measure is a 0 to 10 numeric rating scale, but this scale has not been tested for reliability or agreement between different raters.

OBJECTIVE

The primary purpose of this study was to evaluate the interrater reliability and agreement of the 0 to 10 visual numeric rating scale of uterine tone during cesarean delivery. A secondary purpose was to obtain estimates of scale responsiveness and minimal clinically important difference.

STUDY DESIGN

Between August and November of 2018, obstetricians used a 0 to 10 numeric rating score to independently rate uterine tone at 3 and 10 minutes after cesarean delivery by palpation of the uterus. Of note, "0" represented "no tone" and "10" represented excellent tone. Each obstetrician independently and blinded to the other's score pointed to a numeric rating scale held by the anesthesiologist through a clear sterile drape. Intraclass correlation coefficients and Bland-Altman analysis were used to assess interrater reliability and agreement, respectively. Standardized response mean and standard error of measurement were used to obtain estimates of responsiveness and minimal clinically important difference, respectively.

RESULTS

A total of 82 and 84 pairs of scores were collected at 3 and 10 minutes, respectively, from pairs of 62 unique obstetricians. The mean±standard deviation difference in scores between rater 1 and rater 2 was 0.4±1.4 at 3 minutes and 0.1±1.1 at 10 minutes. Intraclass correlation coefficients for a future single rater (intraclass correlation coefficient [1, 1]) at 3 and 10 minutes were 0.67 (95% confidence interval, 0.53-0.77) and 0.61 (95% confidence interval, 0.46-0.73), and for the average between 2 future raters (intraclass correlation coefficient [1, 2]), they were 0.80 (95% confidence interval, 0.71-0.87) and 0.76 (95% confidence interval, 0.63-0.84), indicating good and excellent reliability, respectively. Bland-Altman analysis estimated 95% limit of agreement between raters of -2.4 (95% confidence interval, -3.0 to -1.9) to 3.1 (95% confidence interval, 2.6-3.7) at 3 minutes and -2.1 (95% confidence interval, -2.5 to -1.7) to 2.4 (95% confidence interval, 2.0-2.8) at 10 minutes, consistent with good interrater agreement at both time points. The standardized response mean from 3 to 10 minutes after delivery was 1.1 (n=81). Standard error of measurement was 1.0 (95% confidence interval, 0.9-1.1) at 3 minutes and 0.8 (95% confidence interval, 0.7-0.9) at 10 minutes.

CONCLUSION

The 0 to 10 numeric rating scale for uterine tone demonstrated good to excellent interrater reliability with 1 and 2 raters, respectively, and good interrater agreement. The scale was responsive to within-parturient change in tone, and preliminary estimates of the minimal clinically important difference were obtained. The 0 to 10 numeric rating scale for uterine tone may be a reliable, standardized tool for future research in reporting degree of uterotonic contraction during cesarean delivery.

A Randomized Control Trial of 3 IU IV Oxytocin Bolus with 7 IU Oxytocin Infusion versus 10 IU Oxytocin Infusion During Cesarean Section for Prevention of Postpartum Hemorrhage

Purpose

Oxytocin is the preferred choice for prophylaxis and treatment of postpartum hemorrhage. Intravenous infusion has been a widely accepted route for Oxytocin administration. However, intravenous bolus route is not a readily preferred route due to apprehensions regarding hypotension that it may cause. This trial compares low dose 3 IU intravenous (IV) bolus Oxytocin along with 7 IU Oxytocin in intravenous infusion to 10IU Oxytocin intravenous infusion during cesarean section.

Patients and Methods

A total of 250 term pregnant women were randomized to either 3 IU intravenous bolus with 7 IU intravenous infusion of Oxytocin or 10IU of intravenous Oxytocin infusion. The difference in pre- and post-operative hemoglobin levels, tone of the uterus, hemodynamic changes, adverse effects of the drug, need for additional uterotonics and need for blood transfusions were assessed.

Results

There was 6.7% less blood loss in the 3 IU IV bolus Oxytocin with 7 IU Oxytocin infusion group in comparison to the Oxytocin infusion group. The tone of the uterus was firmer in IV bolus Oxytocin with Oxytocin infusion group at 5 minutes (p<0.001) than the Oxytocin infusion group. There was no significant difference in the hemodynamic changes, adverse effects or need for blood transfusions.

Conclusion

Intravenous bolus of 3 IU Oxytocin along with 7 IU infusion of Oxytocin is as safe and more effective than intravenous infusion of 10 IU of Oxytocin during cesarean section in the prevention of postpartum hemorrhage.

Oxytocin administration during cesarean delivery: Randomized controlled trial to compare intravenous bolus with intravenous infusion regimen

BACKGROUND

Oxytocin is routinely administered during cesarean delivery for uterine contraction. Adverse effects are known to occur after intravenous oxytocin administration, notably tachycardia, hypotension, and electrokardiogram (EKG) changes, which can be deleterious in high-risk patients.

AIMS AND OBJECTIVES

To compare the hemodynamic changes and uterotonic effect of equivalent dose of oxytocin administered as an intravenous bolus versus intravenous infusion.

STUDY DESIGN

Randomized, double-blind, active controlled trial.

MATERIALS AND METHODS

Eighty parturients undergoing elective cesarean delivery, under spinal anesthesia, were randomly allocated to receive 3 IU of oxytocin either as a bolus intravenous injection over 15 seconds (group B, n = 40) or as an intravenous infusion over 5 minutes (group I, n = 40). Uterine tone was assessed as adequate or inadequate by an obstetrician. Intraoperative heart rate, non-invasive blood pressure, and EKG changes were recorded. These data were compared between the groups. Any other adverse events like chest pain, nausea, vomiting, and flushing were noted.

RESULTS

There was significant rise in heart rate and significant decrease in mean arterial pressure in bolus group compared to infusion group. Three patients in bolus group had EKG changes in the form of ST-T depression and 5 patients complained of chest pain. No such complications were found in infusion group.

CONCLUSION

Bolus oxytocin (at a dose of 3 IU over 15 seconds) and infusion of oxytocin (at a dose of 3 IU over 5 minutes) have comparable uterotonic effect. However, the bolus regime shows significantly more adverse cardiovascular events.

Morphologic evaluation of acute endometritis in mares with differing resistance to uterine infections

The study was designed to determine differences between normal mares and mares with endometrial pathology in the inflammatory response after bacterial challenge. Six normal mares (biopsy category I) and 4 mares with pathological endometrial changes (biopsy category II) were given an intrauterine infusion of β-hemolytic streptococci on the second day of estrus. All mares had a similar kind of inflammatory response after the bacterial inoculation as assessed by rectal and vaginal examinations. There were no significant differences in the amount of discharge, uterine tone, uterine size and cervical relaxation between the groups. Leukocytic response, as determined by endometrial smears and biopsies, was of the same magnitude in both groups. Two mares from the pathological group were not able to eliminate the infection, but had vaginal discharge and bacteriologically positive uterine swabs until the end of the experiment. It is concluded that the inability of some mares to clear uterine infections cannot be explained by a deficient inflammatory response.