Coloured chlorhexidine cotton pads may help to identify cerebrospinal fluid during epidural or spinal anaesthesia

During complicated technical conditions in epidural or spinal anaesthesia, it may be difficult to safely identify the epidural space. The confirmation or exclusion of the presence of cerebrospinal fluid (CSF) during the procedure of regional anaesthesia is helpful to determine the position of the epidural needle in order to proceed with the anaesthetic block.

We have examined how CSF and different anaesthetic solutions change the colour of yellowish phenol red absorbed in cotton pads.

Sodium chloride and local anaesthetic agents do not change the colour of yellowish phenol red. However, CSF immediately changes the colour from yellow to pink or red. Letting a drop of fluid from the epidural/spinal needle fall on to the cleaning pads filled with phenol red will enable the anaesthesiologist to immediately confirm the presence or absence of CSF. The higher pH of CSF relative to that of sodium chloride and local anaesthetic agents explains the different colour reaction.

This colour reaction quickly identifies the presence of CSF and thus the intradural space during the procedure of spinal or epidural anaesthesia.