A comparison of cold, pinprick and touch for assessing the level of spinal block at caesarean section

The sensory block levels of 102 women undergoing caesarean section under spinal anaesthesia were assessed by four different methods: sharp pinprick (Neurotip tester pin), cold (ethyl chloride spray), touch (Neurotip tester pin), touch (ethyl chloride spray). While the data indicate a median difference of some 2 segments between the levels of block assessed by sharp pinprick or cold, and touch, there was no constant relationship between these levels of block within the group nor within individual patients: variable and at times very large differences in the levels of block assessed among these modalities existed: up to 10 segments (pinprick - touch); 11 segments (cold - touch). For any one individual, it is not possible to predict the level of block to touch from a known level of block to sharp pinprick or cold. To facilitate comparison of results across future studies it is suggested that block levels to touch sensation should always be reported. The results suggest that, for clinical purposes, there is no difference in outcomes whether Neurotip touch or ethyl chloride spray touch sensations are used. When using diamorphine 100 micrograms/mL mixed with bupivacaine 0.5% w/v in 8% dextrose, no patient felt any pain or discomfort provided the block to Neurotip or ethyl chloride touch sensations included T6 or above.