title: Identification of the midline by obese and non-obese women during late pregnancy.
abstract: During central neuraxial blockade, identifying the midline in parturients can be difficult, particularly if they are obese. We assessed the ability of women in late pregnancy, both obese and non-obese, to identify the midline of their own back by pointing and by pinprick discrimination with reference to the true midline identified by ultrasound. Thirteen out of 25 (52%) obese women were accurate to within 5 mm in identifying the midline of their back by pointing with their fingertip, compared with 21/25 (84%) non-obese women (p = 0.03). The median (IQR [range]) fingertip-midline distance was greater in obese women (5 (5-10 [0-10]) mm compared with non-obese women (2 (0-5 [0-12]) mm; p = 0.007). Identification of the midline using pinprick was poorer by obese women (median (IQR [range]) 33 (25-45 [3-85]) mm) than by non-obese women (18 (13-25 [8-40]) mm; p < 0.0001). However, women in both groups were correct > 99% of the time in identifying that a stimulus was either to the left or to the right side.
authors.affiliation: Department of Anaesthesia, Chelsea and Westminster Hospital, London, UK.
authors.forename: M
authors.initials: M
authors.lastname: Butcher
authors.forename: R T
authors.initials: RT
authors.lastname: George
authors.forename: J
authors.initials: J
authors.lastname: Ip
authors.forename: J P
authors.initials: JP
authors.lastname: Campbell
authors.forename: S M
authors.initials: SM
authors.lastname: Yentis
mesh_terms: D000767:Anesthesia, Epidural / Q000379:methods*; D000773:Anesthesia, Obstetrical / Q000379:methods*; D015992:Body Mass Index; D004824:Epidural Space / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D009765:Obesity / Q000000981:diagnostic imaging*; D011247:Pregnancy; D018084:Ultrasonography, Interventional / Q000379:methods*