Advanced Pathophysiology

Burns

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Speaker 2: A burn is the damage that happens after something really hot, like a fire, hot water or steam, or even a hot object comes into contact with skin. But burn injuries can also be caused by extreme cold, electricity, some chemicals like strong acids or radiation, like from the sun or medical treatments. Ultimately, burns cause damage and inflammation of the skin. The skin plays an important role in protecting underlying muscles, bones, ligaments, and internal organs, forming a barrier to infectious pathogens and preventing water loss from the body. Now, the skin is divided into three layers; the epidermis, dermis, and hypodermis. The epidermis forms the thin outer most layer of skin and it's made up of several layers of keratinocytes, which make and secrete glycolipids, which help to prevent water from easily seeping into an out of the body. Underneath the epidermis is the thicker dermis layer that contains the nerves and blood vessels.

But the dermis is divided into two layers; a thin papillary layer just below the epidermis and to deeper reticular layer. The papillary layer contains fiber blasts, which produce a connective tissue protein called collagen. The fibroblasts are arranged in finger like projections called papillae, each of which contains blood vessels and nerve endings. Nerve endings found in this layer since pain and fine touch, which allows you to feel something like a feather touching your arm. The reticular layer of the dermis is even thicker than the papillary layer. The collagen and the reticular layer is packed very tightly together, making it excellent tissue support. In addition, fibroblasts in the reticular layer, secrete elastin, which is a stretchy protein that gives skin its flexibility. The reticular layer also contains the skin's accessory structures like oil and sweat glands, hair follicles, lymphatic vessels, and nerves, and all of the blood vessels that serve these tissues. A type of nerve ending found here detects pressure or vibration, which allows you to feel someone grabbing your arm.

Finally, just below the reticular layer is the hypodermis it's made of fat and connective tissue that insulates and pads, the deeper tissue and anchors the skin to the underlying muscle. When the skin is burned, it damages cells and the proteins within them. And the number of skin layers affected determines the burn degree. So in first degree burns, also called superficial burns, the burn only affects the epidermis. In second degree burns, the burn affects the epidermis and the dermis. If only the papillary layer is burned, it's considered a second degree superficial partial thickness burn. But if the burn reaches the deeper reticular layer, but doesn't extend through the entire layer, then it's considered a second degree deep partial thickness burn. In third degree burns also called full thickness burns, the entire epidermis and dermis are effected. And finally, fourth degree burns extend into the hypodermis.

When a skin layer is affected, it means that the skin can't function effectively and common complications are infections, especially from pseudomonas aeruginosa and water loss through the damaged skin. As burns heal, macrophages move into the tissue to remove dead cells, and fibroblasts create new collagen to heal the damaged skin. The more extensive the area with new collagen, the more extensive the scar. So scars are common in second degree deep partial thickness burns and third and fourth degree burns. Symptoms of a burn depend on the degree of the burn. In first degree, the effected area becomes red, dry and painful. These areas also tend to blanche turning white as blood flow is restricted with compression. Second degree superficial partial thickness burns can be read with clear blisters, wet as if they're weeping, and are even more painful than first degree burns, but still blanche.

A second degree deep partial thickness burn may vary in color from yellow or white to red, have blisters and can be wet or dry. Because of damage to blood vessels and nerve endings, burns of this degree may not blanche and there may only be pain due to pressure because of nerve damage. A third degree burn can appear waxy white to leathery gray or black and dry. Again, blanching doesn't occur and the pain may only feel like deep pressure. In other words, they can be relatively painless. Additionally, the elastin damage causes the burn to be stiff or inelastic. Finally, fourth degree burns are charred black, dry, have pain only from deep pressure, but can be painless from complete destruction of nerve endings and have patches of dead skin. Having said that the margins of all burns often have lots of damaged nerve endings, and that can be painful.

The diagnosis of a burn is often based on the burn's appearance and the amount or type of pain. But sometimes tissue biopsies are obtained to accurately determine which layers are affected. In adults, the severity of burns is calculated using the rule of nines. The rule of nines evaluate several distinct sections of the body's total surface area for the presence and degree of burns. 11 of the sections each make up 9% of the body's surface area and are the head, right arm, left arm, chest, abdomen, upper back, lower back, the front of the left leg, and the back of the left leg, and the same for the right leg. A final section, the groin, accounts for the missing 1% of the body's surface area. The treatment for a burn is determined by what caused the burn, the rule of nines and the location of the burns on the body. In general, immediate treatment typically includes preventing further burning, like flushing the burn with cool, but not ice cold running water. After that, it's important to manage pain with medication.

Minor burns, like first and second degree superficial thickness burns, can heal on their own over a few days or weeks by keeping them bandaged and clean with soap and water. Sometimes lotions to prevent drying or topical antibiotics can be used. If blisters form it's best to leave them alone because the intact skin helps to prevent infections. For more serious burns like electrical and chemical burns or second or third degree burns in sensitive areas like the face, hands and genitalia hospitalization in specialized burn centers is often needed. In those situations, it's important to replenish lost fluids and electrolytes and to prevent infections with antibiotics. Surgical procedures like skin grafting, excision of dead skin or amputation, especially in third or fourth degree burns, may also be needed.

So to recap, a burn is injury, protein denaturation and cellular damage that occurs in the skin caused by extreme heat or cold, electricity, some chemicals, or radiation. The degree of burn is determined by whether the epidermis, dermis or hypodermis are affected and each degree has specific symptoms. The rule of nines, the cause of the burn and location of the burn can help determine treatments. In general, treatments include minimizing the initial burn and pain management. Minor burns don't typically require treatment beyond keeping the area clean, moist and bandaged. But severe burns may require more extensive medical intervention, particularly hospitalization at specialized burn centers to prevent infections and dehydration.

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