The relationship between resting blood pressure and acute pain sensitivity in healthy normotensives and chronic back pain sufferers: the effects of opioid blockade

Abstract

Resting blood pressure is inversely correlated with acute pain sensitivity in healthy normotensives. This study tested: (1) whether endogenous opioid activity is necessary for this adaptive relationship to occur, (2) whether this relationship is altered in chronic low back pain (LBP), and (3) whether endogenous opioid dysfunction underlies any such alterations. Fifty-one pain-free normotensives and 44 normotensive chronic LBP sufferers received opioid blockade (8 mg naloxone i.v.) or placebo blockade (saline) in randomized, counterbalanced order in separate sessions. During each session, subjects participated in a 1-min finger pressure (FP) pain task followed by an ischemic (ISC) forearm pain task. Among pain-free normotensives, elevated resting systolic (SBP) and diastolic (DBP) blood pressure were associated with significantly higher ISC pain thresholds (P values <0.05). Elevated SBP was also associated with significantly lower FP pain ratings (P<0.05). Opioid blockade had no significant effect on the BP-pain relationships detected (P values >0.10). In combined groups analyses, a significant subject typexSBP interaction (P<0.005) was found on ISC pain threshold: elevated SBP was associated with higher pain threshold in pain-free controls, but with lower pain threshold in LBP subjects. Although subject typexBP interactions on FP and ISC pain ratings were not significant, inclusion of LBP subjects in these analyses resulted in the overall relationship between BP and pain sensitivity becoming positive (P values <0.05). Opioid blockade exerted no significant main or interaction effects in these combined groups analyses (p values >0.10). Higher DBP was associated with greater clinical pain intensity among the LBP subjects (P<0.001). Overall, these results suggest: (1) endogenous opioids do not mediate the inverse relationship between resting blood pressure and acute pain sensitivity in pain-free normotensives; (2) the BP-pain sensitivity relationship is altered in chronic pain, suggesting dysfunction in pain regulatory systems, and (3) these alterations are not related to opioid dysfunction.

Pain catastrophizing, physiological indexes, and chronic pain severity: tests of mediation and moderation models

“…Finally, although prior work suggests that blood pressure-related analgesia may be impaired in chronic pain patients (Bragdon et al 2002;Bruehl et al 2002;Bruehl and Chung 2004), the current findings indicate that some patients do exhibit effective blood pressure-related anal-gesia. These contrasting findings could reflect key methodological differences across these studies.…”

“…From a "person × situation" perspective, it perhaps may have been more appropriate to examine links between pain catastrophizing and chronic pain using interviews probing for difficulties adjusting to pain, interference with social and work functioning, issues of loss and so forth. The ability to test whether catastrophizing affects pain through physiological reactivity may have been limited because of the unrestricted topics patients could describe in the interviews.Finally, although prior work suggests that blood pressure-related analgesia may be impaired in chronic pain patients (Bragdon et al 2002;Bruehl et al 2002;Bruehl and Chung 2004), the current findings indicate that some patients do exhibit effective blood pressure-related anal-gesia. These contrasting findings could reflect key methodological differences across these studies.…”

Nociceptive flexion reflex thresholds and pain during rest and computer game play in patients with hypertension and individuals at risk for hypertension

“…In humans, the evidence in favour of opioid dysfunction is mostly negative (e.g., Bruehl et al, 2002;France et al, 2005;Ring et al, 2007;Schobel et al, 1998;cf. McCubbin and Bruehl, 1994;McCubbin et al, 2006) whereas the evidence for baroreceptor activation is more mixed (e.g., al 'Absi et al, 2005;Edwards et al, 2001Edwards et al, ,2003aGuasti, Zanotta, Mainardi, et al, 2002;McIntyre et al, 2006;Rau et al, 1995).…”

Reduced Analgesic Effect of Acupuncture-like TENS but Not Conventional TENS in Opioid-Treated Patients

“…20,38 These results are supported by human studies that showed that small doses of naloxone (blocking for the most part μ opioid receptors) 17 are able to reverse AT but not CT analgesia. 1,8,15,19,24,37,44 Alternately, large doses of naloxone (which are believed to ensure adequate blockage of all opioid receptor subtypes) 3,5 were shown to reverse CT analgesia. 23 The interaction between AT and opioids (but not between CT and opioids) observed in the present study indirectly confirm these observations.…”