How burns affect the tissues.....

Doc, could you please explain the cellular and chemical processes that occur when the tissues are burnt?

Rony v, Goa

A number of inflammatory processes both local (at the site of the burn) as well as systemic (in the rest of the body) take place when burns occur which eventually lead to the shifting of fluid from the vascular compartment to the interstitial spaces. Subsequent to the burn a number of cells like Neutrophils, macrophages, and lymphocytes cross over into the burned tissues and start releasing chemical mediators like histamine, serotonin, prostaglandins, kinins, platelet products and complement components. These chemical substances damage the normal blood capillary barrier which leads to an increase in the permeability of the vessels. Intravascular fluids therefore start to leak from the walls of the vessels and this ultimately leads to a decrease of the circulating intravascular blood volume. A fact that is not commonly recognized is that these processes that occur in the burn tissues also take place in the tissues that have not suffered any burns and therefore one can see edema in areas of the body that have not suffered burns. Thermal injury also ends up damaging the cell wall and collagen fibers which in turn lead to inadequacy of the cell wall transport mechanisms and buildup of sodium and water and eventual death of the cell if the fluid imbalances are not immediately corrected. In minor burns such as 10 percent in children and about 15 percent in adults these fluid balances are well adjusted and tolerated and therefore additional fluid replacements are not needed. However in patients with TBSA higher than the one’s mentioned above intravenous fluid resuscitation is needed.

The capillaries begin to regain their functional integrity and the leak eventually gets controlled, but this often takes more than 8 hours post burn. Crystalloids are usually given in the first 8 hours and one’s the integrity of the capillary wall is regained after 8 hours, colloid fluids are started since they will not leak out. Adding colloids also help to reduce the fluid overload that may result of excess of crystalloid infusions. Burn wounds are composed of three zones- a central zone of coagulation or severe tissue damage, a peripheral zone of hyperemia or vasodilatation, and an  intervening zone of stasis or low blood flow (ischaemia). If the fluid imbalances that occur from the fluid shifts as noted above are not corrected on time then these zones can extend and more tissue damage can result explaining the fact that some superficial burns on admission can end up as deep over period of time. This can also happen when burn wounds get infected.

(an original initiative in burn care education from asktheburnsurgeon)

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Burns, fluid therapy, burn management, fluid resuscitation in burns

Doc why is fluid therapy so important in burn patients?

Neeraj,

Pune, India

Till the nineteenth century burn patients had a high mortality rate. Why so many patients died in the early stage of burn treatment remained a mystery till the concept of body fluids in different compartments became clear. The body fluids lie in three different compartments- vascular (within the blood vessels), intracellular (within the cells) and extracellular space (outside the cells and blood vessels). A constant shift of fluids keeps occurring to maintain a balance between these three spaces and they remain in a state of equilibrium.

Among the organs of the body the skin is the largest – about 15% of body weight and roughly 1.7 sq meter in surface area. While the skin has a large number of functions like sensation, physical protection, temperature regulation and others, the function of prevention of fluid loss is critical to the burn management. Skin is made up of two critical components –dermis and epidermis.  Burns damage the integrity of the skin and destroy its ability to manage fluids effectively. A lot of chemical substances are released due to the burn injury which increases the leaking of fluids from the vascular compartment to the extracellular space causing edema or tissue swelling. This edema may be insignificant in small burns but in large burns or burns more than 10 percent in children and 15 percent in adults can lead to   loss of water, albumin, sodium  and red blood cells which can lead to a sudden fall in the vascular space compartment pressure and shock (burn shock)- culminating in death if not properly treated. The larger the TBSA of burn (Total body surface area) the greater the risk of death. The fluid loss need to be calculated correctly and has to be replaced. Some historic events like the coconut groove fires and other mass casualties led researches to understand the importance of fluid management especially in the initial stage of burn management.   

It is believed that every year, 2.5 million Americans sustain a significant burn injury of which about 100,000 are hospitalized, and around 10,000 die. Burn researchers - Underhill and Moore were the first to identify the concept of thermal injury- induced intravascular fluid deficits in the early nineteenth century, followed by Evans who introduced the fluid resuscitation formula in 1952. More than 50 percent of patients with 50% TBSA  or more died in the past and now this mortality has come down to less than 10 percent – all because of the clear understanding of fluid management in burn care. 

 (An original initiative in burn care education from asktheburnsurgeon!!!)

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