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Obstetric – Free Papers 2
OP030 Landmark accuracy for spinal anaesthesia in obese obstetric patients: should we use lumbar ultrasound routinely?
  1. Nishant Kalra1,
  2. Nishant Kalra1,
  3. Fleur Roberts2,
  4. Mark Prince2,
  5. Timothy Orr2,
  6. Ian Wrench2,
  7. Phil Bonnet2 and
  8. Alison Colhoun3
  1. 1Higher Clinical Fellow, Anaesthetics, Cambridge University Hospitals, NHS Foundation Trust, Cambridge, UK
  2. 2Consultant Anaesthetist, Sheffield Teaching Hospitals NHS Trust, Royal Hallamshire Hospital, Glossop Road, Sheffield, S10 2JF, UK, Sheffield, UK
  3. 3Consultant Anaesthetist, Barnsley District General Hospital, Gawber Road, Barnsley, S75 2EP, UK, Barnsley, UK

Abstract

Please confirm that an ethics committee approval has been applied for or granted: Yes: I’m uploading the Ethics Committee Approval as a PDF file with this abstract submission

Background and Aims Obesity complicates landmark-based spinal anaesthesia, increasing misidentification of intervertebral levels and needle insertions. While various meta-analyses have compared ultrasound to landmark techniques, obstetric studies remain scarce. In this study, we aimed to determine if obesity impacts injection site accuracy in landmark-based spinal anaesthesia among Obstetric patients.

Methods Ethical approval was obtained for this observational prospective cohort study(HRA,England 16/NE/0410). Two cohorts were defined as lower BMI >/=35 kgm-2 or higher BMI <35 Kgm-2, based on our local population’s median booking BMI(35 kgm-2). Intervertebral space was determined by the anaesthetist using landmark-based approach which assumes the line intersecting top of iliac crests at the level of L4 vertebra and distal end of spinal cord at L1 vertebra. Using ultrasound(U/S), the research team determined whether there was a difference between the landmark and the U/S-derived spinal level and then quantified the difference in levels. We also recorded difficulty in identifying the landmarks.

Results 111 women were included. Palpating landmarks was significantly easier in the lower BMI group (n=55) than higher BMI group(n=56), (p < 0.0001). Spinal level was correctly determined only approximately 50% of the time in both the lower and the higher BMI group (50.9% v 44.6%, p=0.7); however, with the higher BMI group, 100% inaccuracies resulted from aiming too high, compared to 69.8% in lower BMI group(p=0.001).

View this table:
Abstract OP030 Table 1

Comparing landmark-based spinal injection accuracy between Lower BMI (35 kgm-2) groups

Abstract OP030 Figure 1
Abstract OP030 Figure 1

Lumbar spine anatomy visualised using a low-frequency curved array 2-5MHz Ultrasound probe positioned just paramedian to the spine and angling medially to obtain the classic “Saw tooth” pattern

Abstract OP030 Figure 2
Abstract OP030 Figure 2

Ultrasound probe moved caudad to cephalad, enabling the sacrum and lumbar spine interspaces to be identified using the “counting up” approach as illustrated by the picture

Conclusions Obesity increases the risk of aiming higher than intended intervertebral space for spinal anaesthesia in obstetric patients using traditional landmark-based approach, which highlights the need for routinely incorporating pre-procedural ultrasound, especially in this group of patients.

  • Obstetric spinal anaesthesia
  • landmark-based approach
  • pre-procedural ultrasound
  • obesity.

https://doi.org/10.1136/rapm-2024-ESRA.29

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