Pathophysiology of Shock

#KYJ Pale, Cold 'n' Clammy

In this Knowing your jargon episode of #FOANed I look at arguably the most recognisable symptoms of shock and the Fight or flight response.

When many animals sense fear, threat or stress, they experience a neurohormonal response that aims at assisting the animal to stand and fight the threat (eg an attacking predator) or flee from it.  This is called fight n flight.  It manifests as tachycardia, adrenaline release, enhanced muscle strength, increased cardiac output/blood pressure, miscarriage, high blood sugar, pupil dilation, And our topic of the day "Pale, cold n clammy".  Let's look at these individually.

Pale

As the sympathetic nervous system is activated to cause increase in cardiac output, it achieves this in part, by constricting peripheral veins in arms, legs, feet, hands and skin. Given that our perfused skin takes on a pink tinge due to blood in the dermal vessels, vasoconstriction in skin leads to reduced blood, so reduced pink hues.  The skin looks pale to ashen in colour.  In dark skinned people, the palms and nail beds become pale.

Cold

For the same reason as pallor, reduced blood flow in skin causes the skin to feel cool to cold, to the touch. 

The vasoconstriction peripherally, redistributes blood away from tissues that ate not vital to immediate survival, and towards the core central circulation (heart,brain,lungs,kidneys).

Clammy

Perspiration or sweat is stimulated by the sympathetic nervous system activated during a stressful event or threat. This has its roots in evolutionary biology where at one time sweat contained many chemicals. Some were toxic to predators to ingest, some were foul tasting, dissuading the predator from eating you, and some, collectively called pheromones, are produced as a chemical attractant, or in the case of attack, as a repellant, offensive odour.  The Skunk is perhaps the most notable mammal that achieves this.   Clamminess it therefore an ancient symptom that serves little purpose in humans, but still seen as part of this fight n flight response of pale,cold n clammy.

Many intimate partners would attest to the fact that their partner's perspiration and scent is different when they are aroused, than when they are angry.  This is largely due to their being different sweat glands. Eccrine glands are the most abundant sweat glands that are all over our body, apocrine sweat glands are specialised and found around nipples, axilla, groin, genitalia and other areas. These produce scents usually associated with sexual arousal.

So there it is. Pale, cold and clammy =Shock (usually).  These symptoms represent a response to a physical or psychological threat.

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