A recent study published in European Journal of Pain has shown that remote ischemic conditioning (RIC) induces a decrease in blood flow in complex regional pain syndrome (CRPS).

Complex regional pain syndrome is a neurological condition, characterized by vascular changes like increased blood shunting and decreased monoxide (NO) blood-levels, which further leads to decreased tissue perfusion. Remote ischemic conditioning is an application of non-damaging ischemia in cycles which causes increased tissue perfusion, among others triggered by NO. Therefore, it was hypothesized that RIC could improve tissue perfusion in CRPS.

To prove this concept, a study was conducted in which RIC was applied on a group of 21 patients having early CRPS with a clinical history of less than a year, 20 age/sex-matched controls and other one involving 12 patients with unilateral nerve lesions via a tourniquet on the unaffected/non-dominant upper limb. Laser Doppler and tissue spectroscopy were used to check the blood flow and tissue oxygen saturation (StO2) before, during and after RIC on the affected extremity. The oxygen extraction fraction was also calculated.

The study showed that after RIC application, blood flow was declined in CRPS patient (p<0.01). StO2 decreased in CRPS and healthy controls (p<0.01). A negative correlation was observed in oxygen extraction fraction and decreasing blood flow, only among CRPS, between (p < 0.05).

Therefore, it was concluded that RIC induced a decrease in blood flow in CRPS, which led to a revised hypothesis.  The reason for the decrease of blood flow could be an anti-inflammatory effect that attenuates vascular disturbances and reduces blood shunting, thus improving oxygen extraction. Further studies could determine whether a repeated application of RIC leads to reduced hypoxia in chronic CRPS.