Post-occlusive reactive hyperemia evoked a consistent perfusion decrease in both hands during occlusion followed by rapid reperfusion, indicating a sympathetic mediated response.
Observational (n=60)
Randomized limb selection
Does Post-Occlusive Reactive Hyperemia (PORH) evoke a sympathetic reflex in healthy participants?
Post-occlusive reactive hyperemia evokes a systemic sympathetic reflex rather than purely local microcirculatory changes, suggesting new potential clinical endpoints for cardiocirculatory assessment.
Introduction: A practical easy-to-use method to assess cardiocirculatory function in vivo is still a need for the early detection of related processes. The well known Post-Occlusive Reactive Hyperemia (PORH) likely represent the oldest in vivo exploratory strategy with this diagnostic purposes. PORH is believed to represent the local microcirculatory physiology allegedly related to local ischemia and measured by the quantification of the reperfusion response after occlusion of a major artery. A reduction of related endpoints has been linked to impairment of the local microcirculatory unit where measurements take place. However its clinical use is practically nonexistent mostly due to multiple difficulties in interpreting results. Our research concluded that the main obstacle related to the clear understanding of mechanisms underlining PORH. This hyperemic response has been traditionally regarded as an ischemia related (local) adaptive response. Our research defies these views and intends to clarify some of the involved key facts. Methods: We analyzed the effects of hyperemia following PORH in normal healthy participants of both sexes (total n=60). PORH was applied to one randomly chosen limb using a pressure cuff (applied to the arm). Occlusion was maintained for 2 minutes with a 200 mmHg pressure. The procedure measurements took place in both hands palmar skin at baseline (Phase 1), challenge (Phase 2) and recovery (Phase 3). The perfusion response was measured by laser Doppler flowmetry (LDF) in all participants. In a few participants perfusion was also followed by Polarized Spectroscopy (TiVi) in the skin dorsal circulation. Microcirculation imaging was also obtained by photoacoustic tomography (PAT) in the ipsilateral forearm. Hemodynamics were followed by the Task Force platform. Results: PORH immediately evokes a consistent perfusion decrease (LDF) in both hands in Phase 2. In the ipsilateral forearm PAT revealed a strong constriction of superficial skin plexus that keeps perfusion to a minimum during phase 2. TiVi revealed in the same Phase a vasodilation. When PORH ceases, reperfusion occurs rapidly in both limbs, although with different intensities, with blood moving from deeper to superficial plexus.. No other changes were observed. Conclusions: PORH evoke a sequence of two reflexes in both limbs - a fast strong constrictor (sympathetic) response followed by a faster reperfusion when occlusion ceases (sympathetic withdraw). The dorsal vasodilation seems to confirm the presence of the sympathetic vasodilator system. Then a longer duration adaptive reaction emerges most probably determined by the local (endothelial) mediators. These reflexes are meant to preserve hemodynamics in each phase of the procedure confirming that reactive hyperemia is not a local phenomena but a sympathetic mediated response to a sudden change in local hemodynamics. As a direct consequence a new set of endpoints with clinical application potential should be investigated. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Rodrigues et al. (2026) conducted an observational in Healthy participants (n=60). Post-Occlusive Reactive Hyperemia (PORH) vs. Baseline was evaluated on Perfusion response. Post-occlusive reactive hyperemia evoked a consistent perfusion decrease in both hands during occlusion followed by rapid reperfusion, indicating a sympathetic mediated response.