Impact of homeostatic body hydration status, evaluated by hemodynamic measures, on different pain sensitization paths to a chronic pain syndrome

Abstract

Contrasting findings on the mechanisms of chronic pain and hypertension development render the current conventional evidence of a negative relationship between blood pressure (BP) and pain severity insufficient for developing personalized treatments. In this interdisciplinary study, patients with fibromyalgia (FM) exhibiting clinically normal or elevated BP, alongside healthy participants were assessed. Different pain sensitization responses were evaluated using a dynamic 'slowly repeated evoked pain' (SREP) measure, as well as static pain pressure threshold and tolerance measures. Cardiovascular responses to clino-orthostatic (lying-standing) challenges were also examined as acute re- and de-hydration events, challenging cardiovascular and cerebrovascular homeostasis. These challenges involve compensating effects from various cardiac preload or afterload mechanisms associated with different homeostatic body hydration statuses. Additionally, hair cortisol concentration was considered as a factor with an impact on chronic hydration statuses. Pain windup (SREP) and lower pain threshold in FM patients were found to be related to BP rise during clinostatic (lying) rehydration or orthostatic (standing) dehydration events, respectively. These events were determined by acute systemic vasoconstriction (i.e., cardiac afterload response) overcompensating for clinostatic or orthostatic cardiac preload under-responses (low cardiac output or stroke volume). Lower pain tolerance was associated with tonic blood pressure reduction, determined by permanent hypovolemia (low stroke volume) decompensated by permanent systemic vasodilation. In conclusion, the body hydration status profiles assessed by (re)activity of systemic vascular resistance and effective blood volume-related measures can help predict the risk and intensity of different pain sensitization components in chronic pain syndrome, facilitating a more personalized management approach.

The relationship between autonomic nervous system function and interoceptive accuracy in persons with fibromyalgia versus healthy controls

“…Finally, pain thresholds were related to subjectively perceived stress in persons with FM whereas this was not found in healthy controls where pain thresholds were instead associated with SBP and PEP at rest. It has been previously proposed that subjective stress is importantly implicated in pain sensitivity in FM (Ursin and Eriksen, 2001) and some findings also show that physiological measures of for example blood pressure and cardiac factors can be linked to pain thresholds (Davydov et al, 2024). Why these effects were found for one subgroup and not the other group needs further study.…”