Spinal anaesthesia for caesarean section: an ultrasound comparison of two different landmark techniques

Lumbar Ultrasonography for Obstetric Neuraxial Blocks: Sonoanatomy and Literature Review

Ultrasonography has gained popularity in recent years among anaesthesiologists and being used widely for regional blocks and central venous catheterization. Ultrasonography for neuraxial blocks was found beneficial especially for determining the correct needle insertion site and estimating the needle insertion depth of epidural space. In many recent studies, ultrasound guided epidural and spinal blocks have been evaluated among obstetric patients. Pre-procedural lumbar ultrasonography and real time ultrasound guidance for neuraxial blocks was the subject of these studies. We aimed to evaluate lumbar ultrasonography for obstetric neuraxial blocks. We describe the principles of lumbar ultrasound scanning techniques and present a practical review of lumbar sonoanatomy. We discuss the potential impact and benefits of the ultrasound-guided technique in improving obstetric neuraxial blocks and limitations of its use in clinical practice, based on previous studies.

Conus medullaris trauma: is there a greater risk in parturients?

BACKGROUND

There is some evidence that anaesthetists often perform neuraxial blocks at a higher lumbar interspace than intended. It may be questioned whether parturients are at greater risk for neurological damage when the dura is perforated at a more cephalad interspace than L2-L3.

METHODS

Thirty-six patients scheduled for elective Caesarean delivery under CSE anaesthesia were selected for study. Using a B-D Durasafe Adjustable needle combination, the skin-to-epidural distance and the width of the epidural space were measured and matched with 36 female patients undergoing the same anaesthetic technique for orthopaedic procedures.

RESULTS

Pregnant patients had a higher bodyweight (77 vs. 67 kg, p = 0.007) than those scheduled for orthopaedic surgery. The skin-to-epidural distance was similar in both groups (5.3 vs. 5.1 cm, p = 0.3). The width of the epidural space was 1.1 mm larger in parturients (8.2 vs. 7.1 mm, p = 0.04). More patients in this group had tip-to-tip distances exceeding 10 mm (25 vs. 12%).

CONCLUSION

The greater epidural space or tip-to-tip distance between the epidural and spinal needle points in term parturients results in a lower margin of safety with respect to the distance from the dura to spinal cord or conus medullaris. Puncturing the correct interspace is, therefore, of crucial importance in pregnant patients.