Hyperalgesia in Outpatients with Dermal Injury: Quantitative Sensory Testing Versus a Novel Simple Technique†

Objective Dermal inflammation from many causes may produce a reversible period of hyperalgesia (increased sensitivity to pain perception) or allodynia (pain from innocuous stimuli). Hyperalgesia and allodynia have received relatively little attention in clinical trials of acute pain. We sought to quantitate tactile allodynia and thermal hyperalgesia in outpatients presenting with acute dermal injuries. Design We performed a randomized clinical trial to compare standard methodology for the assessment of hyperalgesia with two novel simple quantitative techniques. Patients After Institutional Review Board approval, 40 patients presenting with acute chemical, thermal, mechanical, or infectious skin injury were subjected to a series of tests at the site of injury, an intact mirror site, and a noninjured ipsilateral control site. Outcome Measures Quantitative thermal sensory testing (Medoc sensory analyzer) was followed by a 5-second application, in random order, of copper rods preheated in water to 40°C, 43°C, 46°C, and 49°C. Pressure testing was conducted with a 1.25-inch diameter commercially available pressure transducer gauge. Results The observed pattern of responses was remarkably consistent among testing methods. All challenges with the four different temperatures elicited pain scores on a visual analog scale markedly greater at the injured than at the mirror or control site (P < 0.001 vs control). Pressure discomfort thresholds followed a similar pattern. Conclusions We conclude that hyperalgesia is a prominent contributor to discomfort in acute dermal injury and hence is a legitimate therapeutic target. Quantitation of the contribution of thermal hyperalgesia and tactile allodynia and assessment of their management is feasible using simple, rugged, low-cost methods. This inexpensive methodology may be useful in everyday clinical practice as well as in clinical research evaluating pharmacological agents to manage hyperalgesia.