How do burns lead to shock?

I was reading that if you come across someone with severe burns that you should cover the burn with a dry, sterile dressing and treat for shock.

I was wondering about the physiology around when burns lead to shock- I thought that shock was caused by hypoperfusion.... how do burns line up with this?

To put it in simple terms, fluids from your vascular space seep into the surrounding tissues (called third spacing). Thats why there is massive4 swelling. Besides this, if the burns are weeping serous fluid, that also takes fluid from the vascular space. When you remove all this fluid from the vascular space, ther isn't enough blood to circulate the oxygen, hence be hypoperfusion.
Hope this makes sense for you.

If left untreated, cutaneous thermal injury greater that one-third of the total body surface area (TBSA) invariably results in the severe and unique derangement of cardiovascular function called burn shock. Shock is defined as an abnormal physiologic state in which the flow of blood is insufficient to maintain adequate nutritive perfusion to meet cellular needs.

unresuscitated burn shock correlates with greatly increased hematocrit values in burned patients, which are secondary to fluid and electrolyte loss after burn injury. The increased hematocrit values occurring shortly after severe burn were interpreted as a plasma volume deficit.

It is now recognized that burn shock is a complex process of circulatory and microcirculatory dysfunction, not easily or fully repaired by fluid resuscitation. Severe burn injury results in significant hypovolemic shock and substantial tissue trauma, both of which cause the formation and release of many local and systemic mediators.6-8 Burn shock results from the interplay of hypovolemia and mediator action and continues as a significant pathophysiologic state, even if hypovolemia is corrected. Increases in pulmonary and systemic vascular resistance (SVR) and myocardial depression occur despite adequate preload and volume support.8-12 These physiologic changes can further exacerbate the whole body inflammatory response into a vicious cycle of accelerating organ dysfunction.

well im sure if you had severe burns youd be freaking out to