What is the failure rate in extending labour analgesia in patients with a body mass index ≥ 40 kg/m(2)compared with patients with a body mass index < 30 kg/m(2)? a retrospective pilot study

Anatomy of the lumbar interspinous ligament: findings relevant to epidural insertion using loss of resistance

BACKGROUND AND OBJECTIVES

The 'loss of resistance' technique is used to determine entry into the epidural space, often by a midline needle in the interspinous ligament before the ligamentum flavum. Anatomical explanations for loss of resistance without entry into the epidural space are lacking. This investigation aimed to improve morphometric characterization of the lumbar interspinous ligament by observation and measurement at dissection and from MRI.

METHODS

Measurements were made on 14 embalmed donor lumbar spines (T12 to S1) imaged with MRI and then dissected along a tilted axial plane aligned with the lumbar interspace.

RESULTS

In 73 interspaces, median (IQR) lumbar interspinous plus supraspinous ligament length was 29.7 mm (25.5-33.4). Posterior width was 9.2 mm (7.7, 11.9), with narrowing in the middle (4.5 mm (3.0, 6.8)) and an anterior width of 7.3 mm (5.7, 9.8).Fat-filled gaps were present within 55 (75%). Of 51 anterior gaps, 49 (67%) were related to the ligamenta flava junction. Median (IQR) gap length and width were 3.5 mm (2.5, 5.1) and 1.1 mm (0.9, 1.7).Detection of gaps with MRI had 100% sensitivity (95% CI 93.5 to 100), 94.4% specificity (72.7, 99.9), 98.2% (90.4, 100) positive predictive value and 100% (80.5, 100) negative predictive value against dissection as the gold standard.

CONCLUSIONS

The lumbar interspinous ligament plus supraspinous ligament are biconcave axially. It commonly has fat-filled gaps, particularly anteriorly. These anatomical features may form the anatomical basis for false or equivocal loss of resistance.

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

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.

Epidural extension failure in obese women is comparable to that of non-obese women

BACKGROUND

Management of labor epidurals in obese women is difficult and extension to surgical anesthesia is not always successful. Our previous retrospective pilot study found epidural extension was more likely to fail in obese women. This study used a prospective cohort to compare the failure rate of epidural extension in obese and non-obese women and to identify risk factors for extension failure.

METHODS

One hundred obese participants (Group O, body mass index ≥ 40 kg/m² ) were prospectively identified and allocated two sequential controls (Group C, body mass index ≤ 30 kg/m² ). All subjects utilized epidural labor analgesia and subsequently required anesthesia for cesarean section. The primary outcome measure was failure of the labor epidural to be used as the primary anesthetic technique. Risk factors for extension failure were identified using Chi-squared and logistic regression.

RESULTS

The odds ratio (OR) of extension failure was 1.69 in Group O (20% vs. 13%; 95% CI: 0.88-3.21, P = 0.11). Risk factors for failure in obese women included ineffective labor analgesia requiring anesthesiologist intervention, (OR 3.94, 95% CI: 1.16-13.45, P = 0.028) and BMI > 50 kg/m² (OR 3.42, 95% CI: 1.07-10.96, P = 0.038).

CONCLUSION

The failure rate of epidural extension did not differ significantly between the groups. Further research is needed to determine the influence of body mass index > 50 kg/m² on epidural extension for cesarean section.

Does obesity complicate regional anesthesia and result in longer decision to delivery time for emergency cesarean section?

BACKGROUND

Maternal obesity can cause problems with anesthesia and surgery which may be reflected in emergency cesarean sections (CS) as an increased decision-to-delivery interval (DDI).

AIM

To study the association of elevated maternal BMI with DDI and the failure of regional anesthesia.

METHODS

Eight hundred and forty-two consecutive emergency CSs during a period of 1 year in a tertiary hospital were studied retrospectively. DDIs were analyzed in Crash and < 30-min urgency categories (n = 528), while the time required to establish regional anesthesia and its success were analyzed for all emergency CS cases.

RESULTS

The urgency distribution of the CSs was 11%, 52%, and 37% in Crash, < 30-min, and > 30-min urgency categories respectively. Increased BMI was associated with longer DDI time in the < 30-min urgency category (33(13-176) vs. 38(18-118) min; P < 0.05 for BMI < 30 and > 35 group respectively). Regional anesthesia failures (new regional anesthesia, conversion to general anesthesia, or complaint of pain during surgery) took place in 3.7%, 6.8%, and 8.5% in the BMI < 30, 30-35, and > 35 groups respectively (P = 0.021). Epidural top-up resulted in shorter DDI and time delay between arrival at the operating room and skin incision across all urgency and BMI groups than combined spinal epidural (CSE) anesthesia.

CONCLUSION

Higher BMI was associated with longer DDI and more regional anesthesia failures. Epidural top-up was faster than CSE for establishing CS anesthesia.

Anaesthetic Management of Obese Parturients: What is the Evidence Supporting Practice Guidelines?

Increasing rates of obesity in western populations present management difficulties for clinicians caring for obese pregnant women. Various governing bodies have published clinical guidelines for the care of obese parturients. These guidelines refer to two components of anaesthetic care: anaesthetic consultation in the antenatal period for women with a body mass index (BMI) > 40 kg/m2 and the provision of early epidural analgesia in labour. These recommendations are based on the increased incidence of obstetric complications and the predicted risks and difficulties in providing anaesthetic care. The concept behind early epidural analgesia is logical—site the epidural early, use it for surgical anaesthesia and avoid general anaesthesia if surgery is required. Experts support this recommendation, but there is weak supporting evidence. It is known that the management of labour epidurals in obese women is complicated and that women with extreme obesity require higher rates of general anaesthesia. Anecdotally, anaesthetists view and apply the early epidural recommendation inconsistently and the acceptability of early epidural analgesia to pregnant women is variable. In this topic review, we critically appraise these two practice recommendations. The elements required for effective implementation in multidisciplinary maternity care are considered. We identify gaps in the current literature and suggest areas for future research. While prospective cohort studies addressing epidural extension (‘top-up’) in obese parturients would help inform practice, audit of local practice may better answer the question “is early epidural analgesia beneficial to obese women in my practice?”.