658 Injection site pain correlates with punctate pressure threshold measured by a sensory reduction device

Injection site pain (ISP) is a common experience, with 40% of patients experiencing needle phobia and some avoiding treatment due to concern of cutaneous discomfort. We designed and utilized a sensory reduction device (SRD) to quantify the perception of ‘punctate pressure’, the perception of a distinct point or shape applied to the skin. The device applies punctate pressure using a small dowel. We investigated punctate pressure as a potential surrogate for ISP, positing a positive correlation between these two sensations. Patients receiving Mohs surgery at our clinic were recruited for this study. Inclusion criteria were age 18 or older, ability to consent, intact skin of either forearm, and English speaking. Exclusion criterion was peripheral neuropathy or not passing discrimination task. To obtain baseline ISP, participants were asked to rate their pain from their recent anesthetic injection from 0 to 10. Participants underwent a discrimination task, where a 1mm dowel or 4mm dowel was presented via the SRD five times for each size in random order. Then, in three experimental trials, the force at which 1mm dowel was clearly felt was recorded as the threshold force. Of 40 patients, 34 (85%) scored ≥ 8/10 on the discrimination task and were included in analysis. Median age was 70 years (IQR: 64.75-75.25); 58.8% were male (n=20). Threshold force correlated with ISP (p=0.019; R2 = 0.16). Here, we demonstrated threshold force needed to perceive punctate pressure is a viable surrogate for ISP. Most importantly, a lower threshold for punctate pressure is associated with the experience of increased pain during surgical anesthetic injections.