Altered cardiovascular/pain regulatory relationships in chronic pain

In healthy individuals, there is an inverse relationship between resting blood pressure (BP) and pain sensitivity. This study examined possible dysregulation of this adaptive relation in chronic pain patients, and tested whether the extent of this dysregulation is a function of pain duration, Continuous resting BP_s were assessed for 5 min after a 5-min rest period in 121 chronic benign pain patients. Unlike the inverse relationship observed previously in normals, mean resting diastolic BP_s during the assessment period were correlated positively with ratings of pain severity. A Pain Duration x Systolic BP i nteraction emerged (p > .05) such that the magnitude of the BP-pain relation was greatest in patients with the longest duration of pain, r(38) = .50, p > .001. A hypothesized progressive alteration in endogenous pain regulatory systems in chronic pain patients was supported. A possible role of endogenous opioid dysfunction in accounting for these alterations is discussed. This investigation was supported by Grant BRSG S07 RR05366-28. awarded to John W. Burns by the Biomedical Research Grant Program, Division of Research Resources, National Institutes of Health. We thank Kathleen Kiselica and Ronald Pawl for allowing access to their patients at the Center for Rehabilitation at Lake Forest Hospital in Lake Forest, IL.