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Postpartum haemorrhage is a leading cause of maternal death during childbirth. There is an increasing incidence of atonic postpartum haemorrhage in developed countries, and maternal obesity has been proposed as a contributing factor. The dose-response relationship of carbetocin in obese women has not yet been determined. We conducted a double-blind, dose-finding study of carbetocin using a biased coin up-and-down design in women with a body mass index ≥ 40 kg.m À2 undergoing elective caesarean section. The determinant for a successful response was satisfactory uterine tone, with no intra-operative need for additional uterotonic drugs. Secondary outcomes included the use of additional uterotonic drugs postoperatively, estimated blood loss and adverse effects of carbetocin administration. Thirty women were recruited to the study. The median (IQR [range]) body mass index was 44.93 (41.5-55.2 [40-66.5]) kg.m À2 . The ED 90 of carbetocin was estimated as 62.9 (95%CI 57.0-68.7) lg using the truncated Dixon and Mood method, and 68 (95%CI 52-77) lg using the isotonic regression method. The estimated blood loss was 880 (621-1178 [75-2442]) ml. The overall rates of hypotension and hypertension after delivery were 40% and 6.7%, respectively, while nausea occurred in 26.7% of women. The ED 90 for carbetocin in obese women at elective caesarean section is lower than the dose of 100 lg currently recommended by the Society of Obstetricians and Gynaecologists of Canada, but is approximately four times higher than the previously demonstrated ED 90 of 14.8 lg in women with body mass index < 40 kg.m À2 .

Background: Evaluation of the anterior neck anatomy is used to identify the cricothyroid membrane (CTM) before front of neck airway access. This has been traditionally performed using palpation which results in misidentification of the CTM in a high proportion of subjects. The 'laryngeal handshake' is currently advocated by the Difficult Airway Society as the method to identify the CTM. We sought to investigate the accuracy of this technique in females. Methods: Five clinicians were asked to identify the CTM using the 'laryngeal handshake' technique in a total of 45 anaesthetised females (Group L) and by conventional palpation in 45 controls (Group P). We measured and analysed the distance to actual CTM using ultrasound, the time to identification, and perceived difficulty using a visual analogue scale. Results: Successful identification of the CTM occurred in 28/45 (62%) patients in Group L vs 15/45 (33%) in Group P [P¼0.006; mean difference, 29%; 95% confidence interval (CI), 21e39%]. Distance to the CTM (P¼0.012) and visual analogue scale (P¼0.012) were significantly reduced in Group L. Mean time to CTM identification was greater in Group L at 31 (5.6) s, compared with Group P, which took 18 (5.5) s (P<0.001). The midline was accurately identified more frequently in Group L than in Group P (39/45 vs 28/45, P¼0.008). Conclusions: The 'laryngeal handshake' method of palpation is more accurate but takes longer than conventional palpation technique in locating the CTM and the midline. This is of particular relevance if a vertical incision is required to perform front of neck access when anatomy is indistinct.