VASOCONSTRICTION: PERIPHERAL, CUTANEOUS, SUBSTANCES, MEDICATIONS - ANATOMY AND PHYSIOLOGY - 2025

The vasoconstriction is reducing the caliber of a glass blood due to the contraction of vascular smooth muscle that forms the walls of arteries, arterioles and veins. Capillaries - very small blood vessels - do not have muscles in their walls, so they do not enter into the concept of vasoconstriction.

This reduction in vascular caliber occurs for many causes and also has multiple purposes. The control of contraction and relaxation of the vascular musculature depends on many intra and extracellular phenomena, and any alteration in these can cause pathological events such as arterial hypertension, ischemia and heart attacks.

Peripheral vasoconstriction

Peripheral vasoconstriction is an important autonomic response of the body to specific stimuli.

This phenomenon occurs basically in the presence of hypothermia and severe bleeding; in the first case, to try to maintain the proper body temperature; and in the second case, to conserve blood supply to key organs.

Hypothermia

When there is a picture of hypothermia, either by contact with very cold water or exposure to climates with freezing temperatures, the sympathetic nervous system is activated and orders the adrenal glands to release certain substances, such as adrenaline and noradrenaline, which they have a powerful vasoconstrictor effect at the peripheral level.

These substances act at the level of certain receptors found on the walls of the blood vessels.

Once these receptors are activated, the muscle cells of the arteries and arterioles contract, reducing their light or caliber, at the same time reducing the flow of blood through them and diverting it towards the vital organs.

This mechanism is activated when core body temperature drops, not skin temperature. That is why prolonged exposures to cold or extremely low temperatures are necessary for peripheral vasoconstriction to occur as such, with the consequent redistribution of blood flow.

Bleeding

When significant bleeding occurs, whether it is simple or injury-mediated, vasoconstriction also occurs.

Simple bleeding is understood to be that which is not a consequence of tissue destruction, such as digestive bleeding or dysfunctional uterine bleeding. Bleeding from musculoskeletal injuries is usually more severe.

The sympathetic nervous system is activated by perceiving blood loss and a decrease in blood pressure. Vasoconstrictor substances are released, which exert their functions by increasing peripheral vascular resistance, blood pressure and ensuring blood flow to the heart, brain and lungs, compromising the kidneys and intestines.

This vasoconstrictor effect has a limited action, both in time and intensity, both due to the consumption of the substances that generate it and due to its definitive consequences, since prolonged blood flow compromise can cause renal necrosis and mesenteric infarcts, deteriorating the condition. patient clinic.

Cutaneous vasoconstriction

Cutaneous vasoconstriction is not a phenomenon apart from the peripheral one, but it has its own characteristics. The main characteristic of cutaneous vasoconstriction is paleness.

By reducing the caliber of the arterioles and small vessels of the dermis, with the immediate reduction of blood flow, there is an abnormal loss of skin color and hypothermia to the touch.

Paleness, considered a clinical sign by physicians in general, is usually one of the first obvious consequences in patients with active bleeding or hypothermia.

In fact, its appearance is very early and allows health professionals to act before further complications occur.

Some particular situations other than cold or bleeding can trigger skin vasoconstriction. Stress, the use of certain medications or drugs, sports activity and various diseases can cause paleness by different mechanisms, the only common denominator being the entry of calcium into the vascular muscle cells.

Vasoconstrictor drugs and substances

The factors that trigger vasoconstriction can be endogenous or exogenous. Whatever its origin, multiple internal elements will mediate so that the final consequence is the reduction of the vascular caliber.

Epinephrine

Also known as adrenaline (perhaps its most popular name), it is a naturally occurring substance permanently present in the blood and that produces a vasoconstrictive effect when its serum levels increase.

Norepinephrine

Chemically very similar to epinephrine, but with a more powerful vasoconstrictor effect. It is only released from the adrenal glands in very precise situations.

It is also known as norepinephrine. Some authors refer to norepinephrine when speaking of the naturally produced one and norepinephrine when they speak of the synthetic one.

Vasopressin

Synthetic form of antidiuretic hormone produced in the pituitary. In addition to concentrating the urine by promoting the renal reabsorption of water, it has an important vasoconstrictor effect.

Dopamine

Dopamine is an organic catecholamine produced in the brain and kidneys that performs multiple functions in the human body, including vasoconstriction tasks.

These first four substances are naturally produced by the body, but can also be synthesized in pharmacological laboratories.

All have clinical use and are frequently used in intensive care units, trauma shock and operating rooms.

Angiotensin II

Powerful endogenous vasoconstrictor, whose activation is inhibited through the regular administration of drugs known as ACEIs (angiotensin converting enzyme inhibitors), which are one of the most widely used antihypertensives in the world today.

Thromboxanes and endothelin

Endogenous substances that act in the area of ​​the vascular muscles, favoring the entry of calcium into the muscle cells and generating vasoconstriction.

Some chemical substances produced in laboratories, clandetinal or not, that are used for recreational purposes, have predominantly peripheral vasoconstrictive effects and can be administered by different routes. Among these substances we have:

- Cocaine.

- Amphetamines.

- Alpha-methyltryptaline (Indopan).

- 25I or «N-Bomb».

- LSD.

- Mephedrone (meow meow, cactus food, CatMef).

Several medications have some vasoconstrictive effect, not necessarily as their main function, but affecting blood pressure values. The most recognized are:

- Ephedrine.

- Pseudoephedrine.

- Phenylephrine.

- Oxymetazoline.

- Antihistamines.

Caffeine and xanthines, present in coffee and various types of tea, can cause asymptomatic vasoconstriction in humans.

References

1. Clark, Joseph and Pyne-Geithman, Gail (2005). Vascular smooth muscle function: The physiology and pathology of vasoconstriction. Pathophysiology, 12 (1), 35-45.
2. Johnson, John; Minson, Christopher and Kellogg, Dean (2014). Cutaneous Vasodilator and Vasoconstrictor Mechanisms in Temperature Regulation. Comprehensive Physiology, American Physiological Society, 4: 33-89.
3. Kirkman, E and Watts, S (2014). Haemodynamic changes in trauma. British Journal of Anesthesia, 113 (2), 266-275.
4. Van Someren, Eus (2011). Age-Related Changes in Thermoreception and Thermoregulation. Handbook of the Biology of Aging, 7th Edition, Chapter 22, 463-478.
5. Wikipedia (last edition April 2018). Vasoconstriction. Recovered from: en.wikipedia.org
6. Encyclopaedia Britannica (nd). Vasoconstriction. Recovered from: britannica.com