Increased maternal body mass index is associated with prolonged anaesthetic and surgical times for caesarean delivery but is partially offset by clinician seniority and established epidural analgesia

Abstract

Background: Obesity is associated with higher surgical and anaesthetic morbidity and difficulties.

Aims: We aimed to investigate associations between maternal body mass index (BMI) and the in-theatre time taken to produce an anaesthetised state or to perform surgery for caesarean delivery.

Materials and methods: Using the Strengthening the Reporting of Observational Studies in Epidemiology guidelines, we identified all women who underwent caesarean section at a single institution (2009-2015). The prospectively collected data arising from antenatal and peripartum care were analysed. Generalised linear regression was used to examine associations between maternal BMI and the time taken to anaesthetise the mother and the duration of surgery.

Results: Of a total of 24 761 caesarean deliveries, 5607 (22.7%) women were obese at antenatal registration. In-theatre anaesthetic preparation (18 vs 32 min, P < 0.001) and surgical duration (38 vs 52 min, P < 0.001) were longer in women with BMI ≥50 kg/m² (BMI-50) than those with normal BMI (BMI-N). This difference remained significant after controlling for antenatal, intra-operative and immediate postoperative variables. Modifiable variables were identified that may mitigate the effects of severe obesity. Senior obstetric and anaesthetic care were both independently associated with a significant reduction in mean in-theatre anaesthetic preparation time and surgical duration, by 11 and three minutes respectively (P < 0.001), while epidural top-up significantly lessened mean anaesthetic in-theatre preparation duration by seven minutes (P < 0.001).

Conclusions: Obese women had greater anaesthesia and surgery time, but the effect may potentially be mitigated by provision of care by experienced staff and prior establishment of epidural analgesia.

Keywords: anaesthesia; body mass index; caesarean section; neuraxial; obesity; obstetric.

Figure 1

Violin plot of in‐theatre anaesthetic preparation duration by maternal body mass index (BMI). Violin plot shape illustrates probability density (wider = higher probability). White bars with black lines delineate median and interquartile range. Reference red line is at zero minutes. Note the change in shape with maternal BMI ≥ 50 kg/m²(Obese – Classes IV and V) as well as rising median values.

Figure 2

Violin plot of surgical duration by maternal body mass index (BMI). Violin plot shape illustrates probability density (wider = higher probability). White bars with black lines delineate median and interquartile range. Reference blue line is at eight minutes. Note the rising first interquartile and median values with increasing maternal BMI.