Differences in the epidermal pain threshold between different needle puncture sites

Puncture of the skin by a needle, such as for peripheral nerve block or for intravenous or arterial catheter placement, may cause pain to the patient, so that analgesic method may be required to reduce pain caused by needle puncture. Nevertheless, there is little information as to which puncture sites are more painful than the other.

After obtaining an approval of the study by a research ethics committee and written informed consent from all the participants, we studied 30 volunteers to quantify pain threshold at 13 skin sites of the body, using an algometer.

Compared with pain threshold at the cubital fossa (which was regarded as the control value), the relative pain threshold was significantly lower (with clinically meaningful difference) at the lateral carpus (median (interquartile range): 0.66 (0.56-0.73)) and the medial carpus (0.80 (0.73-0.94)); and was significantly higher (with clinically meaningful difference) at the olecranon (2.08 (1.93-2.42)), the forehead (1.59 (1.46-1.74)), the upper shoulder (1.52 (1.38-1.79)), and the dorsal shoulder (1.39 (1.18-1.55)).

We conclude that there are significant differences in pain threshold between different puncture sites. Analgesic method before needle puncture may be required at the sites where the pain threshold is relatively low.