69 76 Skin blood flow

Skin blood flow: role in temperature regulation, sympathetic control, heat illness and Raynaud phenomenon.

Skin blood flow serves mainly to regulate body temperature, not the skin's own metabolism. At rest in a comfortable environment the skin receives about 5–10% of cardiac output, roughly 0.3–0.5 L/min. In the cold, skin vessels constrict and flow can fall almost to zero, conserving heat. In heat stress, the vessels dilate widely and skin blood flow can rise to 6–8 L/min, carrying heat from the body core to the surface, where it is lost by radiation and sweat evaporation.

SkinThermoregulationMicrocirculation

Share at rest≈ 5–10%

At rest≈ 0.3–0.5 L/min

Severe heat stressup to 6–8 L/min

Main controllersympathetic nerves

Figure 1. Resting distribution of a cardiac output of about 5 L/min (after Chapman and Mitchell, 1965). The highlighted bar shows skin blood flow.

This application estimates regional blood flow as a percentage of cardiac output and converts it into mL/min from the calculated cardiac output. In clinical practice, organ blood flow is measured invasively or with imaging (for example indicator dilution, Doppler ultrasound, PET or MRI perfusion).

Regulation

Skin blood flow is controlled by two sympathetic systems: a vasoconstrictor system (noradrenaline), active in cold, and an active vasodilator system, which accounts for 80–90% of the large skin vasodilation during whole-body heating. Local warming and cooling of the skin also change flow. In shock and hypovolaemia, strong skin vasoconstriction diverts blood to vital organs, which is why the skin becomes cold, pale and clammy.

Clinical significance

Heat illness: high skin flow during heat stress places a large demand on the heart; dehydration and heart disease increase the risk of heat exhaustion and heat stroke
Raynaud phenomenon: excessive vasoconstriction of fingers and toes in cold or stress, with white, blue and then red skin
Diabetes and peripheral artery disease: impaired skin microcirculation slows wound healing and promotes foot ulcers
Menopause: hormonal changes alter skin blood flow control and cause hot flushes
Shock: cold, mottled skin and slow capillary refill are signs of poor perfusion

Seek emergency care

for confusion, high body temperature and hot dry or very sweaty skin after heat exposure, or for cold, mottled skin with dizziness or fainting.

References

Charkoudian N. Skin blood flow in adult human thermoregulation: how it works, when it does not, and why. Mayo Clin Proc. 2003;78(5):603–612. doi:10.4065/78.5.603
Vander A, Sherman J, Luciano D. Human Physiology: The Mechanisms of Body Function. 8th ed. Boston: McGraw-Hill; 2001. Fig. 14-9 (after Chapman CB, Mitchell JH. Sci Am. 1965). Data: BioNumbers BNID 109465

This article is for general information and does not replace a consultation with a doctor. Measurements must be interpreted by a physician together with symptoms and other tests.

Published on 30 April 2024