For induction of spinal anaesthesia is sitting really the same as the lateral position?

The ongoing debate as to the best position for the induction of spinal anaesthesia for caesarean section and how the block should be tested remains unresolved, in part due to the large cohorts of patients required to show statistically significant differences in failure rates. Thus the paper by Sng and colleagues, which suggested no difference in failure rates between the sitting or lateral positions (P=0.4), is welcomed. However, I am not convinced that their data support this. In their analysis only partial block failures (i.e. those needing supplementary intraoperative analgesia) were included. There were four other patients, all sitting inductions, who received general anaesthesia before surgery commenced for an inadequate block level. It is not clear why these women were excluded from the analysis but their inclusion would have resulted in a significant difference between sitting and lateral ‘failures’ (P=0.04). Unfortunately there are insufficient details to give a clear understanding of how the block levels were assessed. They state that loss of cold sensation was used to determine the height of sensory block at the start of surgery and inadequate sensory block was defined as an upper level lower than T5. Was this a complete loss of cold sensation, or a change in the appreciation of the cold sensation? However assessed, it would be of interest to know the level of cold block in the 37 women who required intra-operative supplements. If the level was T5 or above, then it would suggest that loss of cold sensation is not an appropriate testing method to differentiate between blocks that will or will not be adequate for caesarean section.