Evaluation of pre-procedure ultrasound examination as a screening tool for difficult spinal anaesthesia*

We performed a pre-procedure ultrasound examination of the spine on 60 patients undergoing lower extremity orthopaedic surgery under spinal anaesthesia. We hypothesised that the inability to identify the posterior longitudinal ligament or vertebral body easily with ultrasound would be associated with difficulty placing a spinal anaesthetic. Clinicians blinded to the ultrasound scan performed the injections using the traditional landmark technique. The spinal procedure was videotaped and subsequently reviewed by independent investigators. We defined procedure difficulty by total procedure time (> 400 s) and number of needle passes (≥ 10) required to achieve return of cerebrospinal fluid, or abandonment of the procedure due to unsuccessful dural puncture. When images of the posterior longitudinal ligament were poor (low score group), the mean (SD) number of passes was 21.2 (30.6), compared with 4.8 (7.5) with good ultrasound images (high score group) (p < 0.01). The mean (SD) time for placement was 420 (300) s in the low score group vs 176 (176) s in the high score group (p < 0.01). You can respond to this article at http://www.anaesthesiacorrespondence.com.