Content Reviewers:Antonella Melani, MD, Ashley Mauldin MSN, APRN, FNP-BC, Lisa Miklush, PhD, RNC, CNS, Gabrielle Proper, RN, BScN, MN
Contributors:Jung Hee Lee, MScBMC, Evan Debevec-McKenney, Maria Emfietzoglou, MD, Katherine May, BSN, RN
Raynaud phenomenon is a peripheral vascular condition characterized by vasoconstriction of arterioles near the skin, most often of the fingers and toes, which makes them turn white, then blue, and then red.
Okay, now let’s quickly review some anatomy and physiology. Normally, blood flows from large arteries into medium and then small arteries called arterioles, which in turn carry the blood to capillary beds. All arterial vessels have three layers: from inside out, there’s the endothelium; then the media layer, which contains smooth muscle; and finally the adventitia layer, which has loose connective tissue, as well as vasa vasorum or vessels that supply the artery, and nervi vasorum or nerves that innervate the artery and help regulate vasoconstriction via contraction of the smooth muscle in the media layer.
Now, some nerves in the skin function as thermoreceptors, which sense changes in temperature and then send signals up through the spinal cord to the hypothalamus, which is at the base of the brain. The hypothalamus serves as the body’s thermostat and coordinates the body’s response to temperature changes through the sympathetic and parasympathetic nervous systems.
Normally, there’s a lot of heat energy in the blood that gets lost from skin to the environment. So, when the hypothalamus gets the signal that we’re cold, it stimulates the sympathetic nervous system, which in turn signals the nervi vasorum to trigger vasoconstriction in certain body areas, such as the skin, resulting in a reduction of blood flow. That shunts blood away from the skin and towards the body’s core or organs, where less heat energy is lost. On the other hand, when we’re hot, the hypothalamus stimulates the parasympathetic nervous system, which ultimately leads to vasodilation in skin to dissipate the heat.
Now, Raynaud phenomenon is caused by abnormal and exaggerated vasoconstriction in skin. When this occurs alone and is not associated with any other disease, it’s called primary Raynaud phenomenon or Raynaud disease.
Risk factors for primary Raynaud phenomenon include family history, clients assigned female at birth, pregnancy, cigarette smoking, as well as manual occupations that require lots of vibration, like using a jackhammer, or exposure to cold environments or heavy metals, like lead.
On the other hand, when there is an associated disease, it’s called secondary Raynaud phenomenon or Raynaud syndrome. This is often associated with autoimmune diseases, such as systemic lupus erythematosus, Sjögren's syndrome, or scleroderma; as well as vasculitides like Buerger’s disease, Takayasu’s arteritis, or cryoglobulinemia.
Regardless of the type, the most common triggers are emotional stress and exposure to cold temperatures, but other potential triggers include nicotine and caffeine, as well as medications that affect the sympathetic nervous system like pseudoephedrine.
Now when someone susceptible to Raynaud phenomenon experiences a trigger, it causes the nervi vasorum in the walls of arterioles to get overstimulated by the sympathetic nervous system, leading to exaggerated vasoconstriction that dramatically decreases blood flow to the skin.
If the vasoconstriction happens briefly or intermittently, it’s called a vasospasm. Initially, this vasospasm causes ischemia, or decreased blood supply. This is followed by hypoxia, which is the low oxygen state of a tissue that occurs after prolonged ischemia. Finally, once the vasospasm ends, there's reactive hyperemia, where oxygenated blood is able to rush back into the skin.