What is the physiology of the white reaction of skin after a stroke by a sharp object, also known as a blunt (or sharp) trauma-induced pallor (or hypoxia)?

From the Guidelines

The white reaction of skin after being struck by a sharp object, known as blanching or white dermographism, occurs due to a localized vasoconstriction response. When the skin is stroked firmly with a sharp object, the mechanical pressure triggers the release of various chemical mediators from mast cells and nerve endings, including norepinephrine. This causes the smooth muscles surrounding small blood vessels (arterioles) in the affected area to contract, reducing blood flow to the area. The decreased blood supply results in the characteristic white line or area that appears on the skin. This initial blanching is typically followed by a red reaction (erythema) as blood vessels dilate in response to inflammatory mediators released during the injury. The white reaction is a normal physiological response and part of the body's initial protective mechanism to reduce potential blood loss following injury. This response is more pronounced in individuals with fair skin and can be exaggerated in certain conditions like dermatographism, where even light pressure can cause prominent skin reactions. The white reaction typically lasts only a few seconds to minutes before the subsequent inflammatory response takes over, bringing increased blood flow to the area.

Some key points to consider in the context of stroke patients, as mentioned in 1 and 1, include the importance of skin integrity and the potential for skin breakdown due to loss of sensation, impaired circulation, and decreased level of consciousness. However, these studies do not directly address the physiology of the white reaction after a stroke by a sharp object. In the context of real-life clinical medicine, it is essential to prioritize the patient's overall health and well-being, including their skin integrity, while also considering the potential for exaggerated skin reactions in certain individuals. The white reaction is a normal physiological response, but it can be affected by various factors, including the patient's skin type, the severity of the injury, and any underlying medical conditions.

Key factors to consider in the management of stroke patients include:

• Assessing patients' skin every shift and every time patients have been repositioned or sitting, as mentioned in 1
• Using the Braden scale to predict the likelihood of pressure ulcer development
• Repositioning patients at least every 2 hours to avoid excessive friction or pressure
• Keeping the skin clean and dry, and using special mattresses and other padding as needed
• Educating patients and family members regarding proper skin care and assessing them as appropriate in preparation for discharge. However, these factors are not directly related to the physiology of the white reaction after a stroke by a sharp object. The most important consideration is the patient's overall health and well-being, and the white reaction is just one aspect of the body's response to injury.

From the Research

Physiology of White Reaction

The white reaction of skin after a stroke by a sharp object, also known as blunt or sharp trauma-induced pallor or hypoxia, is a complex physiological response.

• The immediate response to trauma involves the activation of the immune system and the release of inflammatory mediators 2.
• However, the provided studies do not directly address the physiology of the white reaction of skin after a stroke by a sharp object.
• Studies on ischemic stroke discuss the injury to white matter and its clinical features, such as cognitive dysfunction and sensorimotor impairments 3.
• The inflammatory response after ischemic stroke involves the activation of glial cells and the release of pro- and anti-inflammatory signals, which can contribute to neuronal cell death 4, 5.
• Collateral circulation plays a crucial role in protecting the brain against ischemic injury and can influence ischemic lesion size and growth 6.

Related Physiological Responses

• The immune response after stroke is a complex process involving various cell types and effector molecules, which can impact tissues outside of the CNS 4.
• Inflammation after ischemic stroke involves the activation of glial cells and infiltrating leukocytes, including neutrophils, monocytes, and lymphocytes 5.
• The release of inflammatory mediators can exacerbate brain injury, but also contribute to wound healing 5.