Obstetric anaesthesia: Overview + SIG resources

Abstract
Background: Ondansetron has been reported to attenuate the incidence of spinal anesthesia-induced hypotension (SAIH) and norepinephrine requirement during cesarean 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 anesthesia for cesarean section. The median effective dose (ED50) and 90% effective dose (ED90) were compared to evaluate the effect of ondansetron versus placebo on the norepinephrine requirement.

Materials and methods: 150 parturients undergoing cesarean section were randomized to receive either 0.1 mg/kg ondansetron or saline control 10 min before spinal anesthesia. 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 ED50 and ED90 of norepinephrine infusion were determined using probit regression. Differences between the two groups were evaluated by comparing the relative median potency with 95% confidence intervals (CIs).

Results: The ED50 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 ED90 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 anesthesia significantly reduced the dose requirement of prophylactic norepinephrine infusion in parturients undergoing elective cesarean section. This finding is potentially useful for clinical practice and further research.

Abstract
Background: Among assisted reproductive technologies, frozen thawed embryo transfer (FET) is associated with increased blood loss at delivery. Anesthesiologists need to be aware of new factors that affect postpartum blood loss. This study investigated whether FET cycles with or without hormonal support affect the amount of postpartum bleeding.

Methods: We conducted a retrospective cohort study of patients admitted for delivery at a single university hospital between January 2015 and December 2018. Patients were divided into no-assisted reproductive technology (No-ART), hormonal cycle FET (HC-FET) and natural cycle FET (NC-FET) group. The primary outcome was the amount of blood loss after delivery (median [interquartile range]), which was compared among the three groups. Multiple regression analysis was performed to investigate the factors affecting blood loss.

Results: Between 2015 and 2018, 3187 women delivered neonates. In vaginal delivery, postpartum blood loss in the HC-FET group (1060 [830] g) was significantly greater than in the NC-FET group (650 [485] g, P = 0.001) and in the No-ART group (590 [420] g P < 0.001). Multiple linear regression analysis showed that HC-FET (P < 0.001) was one of the independent factors for the amount of bleeding. In cesarean delivery, the HC-FET group had more blood loss than the No-ART group (910 [676] g vs. 784 [524] g, P = 0.039). However, HC-FET was not an independent factor for postpartum blood loss.

Conclusions: The HC-FET group had more blood loss than the No-ART group for both vaginal and cesarean deliveries. Furthermore, HC-FET was an independent factor that increased postpartum blood loss in vaginal deliveries.

Abstract
Objectives: To summarize and appraise the use of dexmedetomidine in epidural labor analgesia, we conducted a systematic review and meta-analysis of randomized controlled trials (RCTs).

Methods: We conducted the literature search about the RCTs of epidural labor analgesia with or without dexmedetomidine from inception until Nov 1,2022 in the following databases: PubMed, the Cochrane Library and Embase. The primary outcome was visual analogue scale(VAS) within 2h after epidural intubation. The secondary outcomes included the duration of the first and second labor stage, Apgar score, umbilical blood pH, dosage of analgesics, and side effects.

Results: 8 RCTs including 846 parturients were included. The VAS score of dexmedetomidine group was significantly lower than that of the control group at the time of 15min(MD -1.41,95%CI -2.23,-0.59)、30min(MD -1.02,95%CI -1.70,-0.33)、60min(MD -0.90,95%CI -1.36,-0.44)、90min(MD -0.70,95%CI -1.16,-0.23). The incidence of pruritus in dexmedetomidine group was lower than that of control group（MD 0.28,95%CI 0.11,0.74）but the incidence of maternal bradycardia was higher (MD 6.41,95%CI 1.64,25.04). There were no significant difference in other outcomes.

Discussion: Dexmedetomidine combined with local anesthetic for epidural labor analgesia can improve the VAS score of parturients. Except for the increased incidence of maternal bradycardia, it seems to be safe for the parturients and fetuses.