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Experimental pain phenotyping in adults with sickle cell anemia and normal volunteers

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source: The Journal of Pain

year: 2014

authors: D. Darbari, M. Quinn, C. Seamon, G. Wallen, I. Belfer, J. Taylor


Sickle cell anemia’s (SCA) hallmark is an acute vaso-occlusive pain crisis (VOC) which occurs with hypoxia, intra-vascular erythrocyte sickling and ischemia reperfusion injury. Because frequent pain alters sensory perception, we hypothesized that adults with SCA experience hypersensitivity to experimental pain as observed in other chronic painful conditions. Eighteen subjects with SCA and 19 normal volunteers (NV) underwent quantitative thermal testing (cold and heat) for temperature at first detection, threshold for sensing pain, and pain tolerance as endpoints. Pressure pain threshold and tolerance were measured bilaterally with an algometer. Ischemic pain testing was performed on the non-dominant arm. Testing was at baseline at least 2 weeks since a painful event requiring hospitalization. The only significant difference for thermal testing was temperature at first cold detection (SCA mean 24.5±6.3 ˚C vs. NV mean of 26.6±4.7 ˚C, P=0.05). There were no other significant differences between SCA subjects and NV for cold pain threshold (P=0.84), cold pain tolerance (P=0.82), first heat detection (P=0.21), heat pain threshold (P=0.68) or heat pain tolerance (P=0.38). Furthermore, there were no differences in pressure for pain thresholds at the thumb (P=0.31), forearm (P=0.44) or trapezius (P=0.10), nor were there pain tolerance differences. Surprisingly, ischemic pain QST showed no differences for initial pain threshold (468.3±263.1 seconds for SCA vs. 569.6±395.8 seconds for NV, P=0.69) or pain tolerance (642.5±245.4 seconds for SCA vs. 774.4±453.5 seconds for NV). Detection of cold temperature change was the only observed sensory difference. Of particular interest were the ischemic tests, where SCA subjects tolerate ischemia as well as NV despite the expectation this promotes forearm hypoxia, erythrocyte sickling and potentially vaso-occlusion. The absence of a difference in onset of ischemic pain contradicts the SCA VOC paradigm. Further studies are necessary to further elucidate the pathophysiology of pain in SCA.

organisation: National Heart, Lung and Blood Institute, Bethesda, MD

DOI: 10.1016/j.jpain.2014.01.089

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