Mechanism of injury of Burn

Each has its own distinctive features and management problems

SCALD

Hot water produces a particularly well defined type of skin damage . The temperature of boiling water or steam is constant and the major determinant of severity of injury is the duration of contact . Even a cup of tea or coffee can cause considerable scalding . Immersion of boiling water or prolong steam exposure as in some industrial accidents are particularly dangerous and likely to cause deeper burn , usually it causes partial thickness burn .

FAT  BURN 

Cooking fat or oil has a much higher temperature (180 degree) than boiling water and hot fat cools slowly on the skin surface . Spills therefore causes deep burn .

FLAME BURN

Flame burn have a varried aetiology, house fires ,clothing fires , spills of petrol, on the skin, butane gas fires. They often occurs in confined spaces and may be association with inhalation injury, generally deep burn will result .Flame retardant clothing may burn under extreme condition.

ELECTRIC BURN

The passage of electric current through the tissues causes heating that results in cellular damage.Heat produced is a function of resistance of the tissue , the duration of contact and the square of  the current .Bone is a poor conductor of electrical current , whereas blood vessels , nerves and  muscles are good conductors .Bone can therefore become very hot and cause secondary damage to tissues near the bone . Low voltage <1000 V causes significant contact wounds and may induce cardiac arrest .High voltage >1000V cause damage by two mechanisms – Flash burn and current transmission .The flash from the arc may cause cutaneous burn and ignite clothing and will not damage in deep damage . High voltage current transmission will result in cutaneous entrance and exit wound and deep damage . A direct strike has a high mortality . A side strike may cause superficial burn to the skin and deep exit burn to the feet . Internal damage is not common , but respiratory and then cardiac arrest occur .

COLD INJURY

Tissue damage from cold can occur from industrial accidents due to spill of liquid from nitrogen or similar substances . This injuries cause acute cellular damage with the possibility of either a partial thickness or full thickness burn .Severe cooling can freeze tissues and ice formation is particularly is likely to cause cellular disruption . Frost bite is due to prolong exposure to cold and there is often an element of ischaemic damage .

FRICTION BURN

The tissue damage in friction burn is due to a combination of heat and abrasion . There is generally a superficial open wound that may progress to full thickness skin loss . Friction burn may be associated with degloving injuries where the damage is judged to be deep .Early surgical excision and skin cover is the best means of management .

IONIZING RADIATION 

X- irradiation may lead to tissue necrosis. Such injuries are exceedingly rare if industrial and medical safety pre cautions are working .The tissue necrosis is not developed immediately . Surgical excision and flap reconstruction may be appropriate management .

CHEMICAL  BURN

Numerous chemicals in industrial and domestic situation can cause burn .Tissue damage depends on the strength and quantity of the agents and  the duration of contact .Some agents penetrate deeply or may have  specific toxic effect .Chemicals cause local coagulation of  protein  and necrosis and some also  have systemic .The harmful effect will continue until the  chemical is diluted or neutralize . The most important initial  treatment is dilution with running water .