12. Vascular pain: Ischemic pain in the extremities and Raynaud's syndrome

Peripheral artery diseases (PAD) and Raynaud's syndrome are associated with substantial morbidity. PAD, through the restriction of blood flow to the extremities, may lead to critical limb ischemia with symptoms of pain at rest which may eventually progress to severe limb ischemia with gangrene. This serious and painful clinical condition requires extensive medical care, is limb-threatening and, in case of delayed or unsuccessful treatment, is associated with a high mortality rate. In Raynaud's syndrome, the blood supply to certain parts of the body, usually the fingers and toes and less frequently the nose or ears, is restricted because of vasculopathy of the smaller vessels at acral sites. Under certain circumstances, with cold as the most well-known provoking factor, blood flow restriction occurs, leading to demarcated color changes and symptoms such as pain, paresthesia, and numbness. In severe cases of Raynaud syndrome tissue ischemia may lead to necrosis and the need for amputation of the affected area.

In this narrative review, the literature on the diagnosis and interventional pain treatment of PAD and Raynaud's syndrome was updated and summarized.

This review focused on interventional pain treatment. In PAD, the effects of the intervention on limb salvage, ulcer healing, and ischemic pain were summarized. Additionally, results with respect to skin microcirculation and quality of life were reported if available. In Raynaud's syndrome, we focused on the effect of the intervention on peripheral blood flow metrics and pain intensity during attacks.

In PAD, prevention and treatment of risk factors are important. Initially, conservative treatment and pharmacological therapy are preferred first-line therapies. However, when disease progression occurs, interventional management may be considered. The literature search yielded conflicting evidence for sympathectomy as a treatment for PAD. Spinal cord stimulation (SCS) as a treatment modality for advanced PAD had high-quality evidence for limb salvage in subgroups of patients but conflicting evidence for other outcome measures such as pain, wound healing, and quality of life. The literature search for interventional pain management in Raynaud's syndrome was limited to only one randomized controlled trial (RCT) studying the effect of thoracic sympathectomy. This study had several limitations and hence the level of evidence for this interventional treatment is very low. No RCTs studying SCS in patients with Raynaud's syndrome were found.

In both PAD and Raynaud's syndrome, additional RCTs are needed to substantiate interventional (pain) management and bolster the evidence base for sympathectomy and SCS as treatment options.