We evaluated a new method of assessing sensory block after spinal anae
sthesia using a fine gas jet and compared it with other established me
thods. The gas jet method was used to test the block before and after
surgery and was found to compare favourably with pin-prick (median dif
ference 0 and 0 dermatomes) and ethyl chloride (median difference 0.5
and 1.0 dermatomes) but less well with cotton wool (median difference
-2.0 and -2.0 dermatomes).