◊ 2-Burns & Scalds ◊

II-BURNS AND SCALDS

Definition: -

It is an injury of the skin and underlying tissues as a result of exposure to high temperature or corrosive chemical substances. Burns appear to be fairly uncommon pets. The commonest cause is friction injuries where the animal is hit by a car then dragged along the road or falling from an auto and being dragged behind it. When the etiology of burn is hot liquid or steam, the condition is called scald. Degree of injury depends up on temperature of object and duration of contact with the body. Generally, sudden increase in the tissue temperature causes coagulation of tissue protein and cellular death.

Etiology: -

1-Heat                                                                            

2-Chimicals (acidic or alkaline)

3-Various forms of energy (light, ultraviolet rays, radiation, or electrical current)

Classification of Burns

I-ACCORDING TO THE DEPTH (CLASS I)

Burn depth has been classified according the degrees of injury. Superficial or first degree involves the epidermis layer, partial-thickness or second degree involves the epidermis and mid to deep amount of dermis, and the full-thickness or third degree there is complete destruction of the skin and compromise structures of the subcutaneous

1-Burns grade I

First-degree burns result in some redness and swelling of the injured part, without necrosis of any tissue or the formation of blisters. This type of burns is characterized by injury of the superficial layers of the epidermis, burning pain, marked hyperemia or erythema, and moderate edema of the skin. An example is the mild sunburn, and healing is completed in a few days without scarring as the superficial layers desquamate and replaced by the deeper germinal layers.

2-Burns grade II (Partial thickness)

Second-degree burns show a variable destruction of parts of the epidermis so that blistering occurs. Healing by regeneration in such superficial burns does not necessitate skin grafting, unless secondary infections ensue; no scarring results. This type of burns is characterized by;

1-Injury of the partial thickness of the skin including the whole epidermal layer and parts of the papillary layer of the skin

2-Burns that are caused by hot fluids or steam (in carnivorous animals) are characterized by formation of blisters or vesicles of variable sizes filled with serous exudates. On the other hand, burns as a result of flame (in large animals) never show blisters, but it is associated with edema of the subcutaneous fat.

3-Due to complete loss of epidermis, healing occurs by cells located in the dermis

4-Dilatation of the blood vessels in affected area with exudation of plasma and migration of leucocytes via affected blood vessels

5-Edema of subcutaneous tissue

3-Burns grade III (Full thickness)

Third-degree burns are marked by complete destruction of the epidermis of a region, including the necrosis of accessory skin structures like hair and sweat glands. A brownish-black eschar (a piece of dead tissues) marks the destroyed tissue. This is sloughed off and that defect becomes filled with granulation tissue that later consolidates and changes to form a dense, thick scar. Complications may occur without adequate care, and grafting is not unusual, sometimes being required because of contracture of the scar tissue. This type is characterized by;

1-Injury of the epidermis and papillary layer, the epidermis undergoes total charring, and the papillary layer undergoes coagulative necrosis, leading to transformation of the entire skin into homogenous coagulated mass under the effect of heat and the formed eschar appears leathery and dark brown in color and the skin acquires rubber consistency.

2-Superficial subcutaneous blood vessels undergo thrombosis while deeper ones become progressively permeable leading to edema of the subcutaneous fat

3-Loss of sensation at affected area due to destruction of nerve endings

4-Damaged tissue undergo necrosis and gangrene

5-Healing ensues slowly, unless grafting performed, as the necrosed tissue slowly rejected leaving shallow ulcers, but later on, it is slowly covered by epithelium from wound edges

4-Burns grade IV

This type of burns is characterized by;

1-Total charring of the superficial layers of the skin

2-Coagulative necrosis of the skin through its depth

3-Necrosis of fascia, subcutaneous fat (with massive edema), and even the superficial muscular layers

4-The skin acquires shell appearance

5-Burns grade V

This type of burn is characterized by charring and blackness of all soft tissues and even of the bone.

II-ACCORDING TO EXTENT

Affected surface can be approached by burned body segments. Each forelimb means 9% each rear limb means 18%, head and neck 9%, Trunk and abdomen 18%.

1-Minor burn

It affects less than 15% of the body surface

2-Intermediate burn

It affects 30% of the body surface

3-Major burn

It affects more than 30% of body surface

Pathogenesis

I-LOCAL LESION

Burns grade I and II are manifested by serous or serofibrinous exudation and epithelial regeneration. While burns grade III to V are characterized by inflammatory reaction of purulent nature.

1-Stage of destruction

Skin destruction either occurs as a result of direct cellular damage via protein denaturation, or delayed injury via progressive dermal ischemia, necrosis, and gangrene. Affected area has three zones;

1-Central zone of coagulation contains eschar

2-Intermediate zone contains viable tissue that may die over the next 24 hours after burn

3-Outer hyperemic zone contains inflammatory mediators (prostaglandins and histamine) with edema formation and usually it recovers within 7-10 days unless infection ensues

2-Stage of inflammation

This stage is characterized by vasodilatation, plasma exudation on affected skin, and infection

3-Stage of healing

A-Partial thickness burn: -

Crust is formed to lower evaporation and to act as a dam against infection, then it separate after 3-4 weeks to leave a fully epithelialized healthy skin.

B-Full thickness burn: -

All the skin undergo burning with formation of thick layer called eschar that separates after 4 weeks exposing underlying granulation tissue that start epithelialization of the affected are from the periphery to the center. Healing is slow generally and associated with marked scaring that appears thin, shining, and hairless.

II-CONSTITUTIONAL EFFECT

Few hours after extensive burn, disturbance in circulation of parenchymatous organs, especially kidney, liver and lung, occurs. This disturbance might be due to vasodilatation of the peripheral blood vessels and increased permeability leading to edema and hypovolemia. The injured tissue easily invaded by bacteria leading to suppurative dermatitis. Finally, sepsis, toxemia, or shock (hypovolumic or toxic) ensues. Systemic reactions involve;

1-Kidney function as a result of hypovolemia and absorption of toxins    

2-Liver function

3-Pulmonary function as a result of inhalation of smokes or steam                              

4-Hemoconcentration and disturbance of blood protein, electrolytes, and acid base balance as a result of fluid and blood loss via skin                  

5-Shock and septicemia

Treatment: -

Burns affect primarily the skin, and the degrees of injury are related to the depth and extension surface affected. The skin has many different roles in the normal physiology of the body. It is the primary barrier against invasive infection, helps to maintain the body temperature controlling the evaporation of fluids, adapts to aggressions or changes in the environment like pain, cold and heat. All these functions are impaired in burned animals and have been related as secondary cause of death.

First degree burns usually don’t require any medical treatment, since the fur of your dog or cat will have protected it more than likely from being burned. Second degree burns need to be checked by a veterinarian if they exceed an area of more than two fists. The blisters that usually occur with second degree burns should be left alone if they look normal.

The skin will start healing on its own underneath the blister. The function of the blister is to protect the new skin from infections and further damage. The only thing you can do is applying light gauze to the blister. Then, once the blister bursts it is important to gently remove the dead skin, for example by washing it off the affected area. The new skin that formed under the blister lays open now and needs to be protected. The best way to treat the wound is applying a wound dressing under sterile gauzes.

The major goal in treating burns in your dog, horse or cat is to relieve the pain and heal the burn without infection or major scarring. Aims of treatment are;

1-Relieve of pain

2-Correction of circulatory disturbance

3-Control of bacterial infection

4-Application of healing stimulants

1-Local treatment

Run cold water over the affected area or apply cold packs for up to 15 minutes or until the body part has returned to normal temperature. Do not overcool the animal. If the animal is starting to shiver then stop applying the cold water.

Thorough washing if the cause of burn is corrosive chemical substance. Chemical burns break down the protein in the skin. Pour milk over the burn or paint the area with egg white. This gives the substance something else to break down instead of your animals flesh.

Removal of charred or necrotic tissue as it is good media for bacterial growth and to facilitate contact between the topically applied dressing solutions and healthy skin.

Evacuation of vesicles to allow escaping of its contents and to relieve pain caused by pressure

Electrical burns tend not to damage the superficial skin so there may be little to see while the deep structures can be badly damaged. Be careful of any live wires and turn off power if possible, then remove yourself and the animal from danger, and finally cool the burnt area under running water. The surface of burn can be swapped with

1-Tincture of iodine (antiseptic)                             

2-Saturated solution of picric acid (analgesic and antiseptic)

3-Tannic acid 2% in the form of jelly (astringent)

4-Anodyne antiseptic ointments like cocainised vaseline or iodeform ointment

5-Topical antibacterial agents like dyes (gention violet), sulfa, or antibiotic preparations can be used for control of infection. Systemic antibiotics do not penetrate eschar, so topical therapy is always indicated with antibiotic ointments and creams. Gentamycin, Polymyxin, Neomycin, and bacitracin are very effective against the contaminant flora in burn wounds, as well as fluoroquinolones.

6-Solcoseryl or panthenol ointment, or cod liver oil can be used to stimulate healing

2-Systemic treatment

1-Stimulants (hypodermic caffeine) to counteract the effect of toxemia and depression

2-Antihistaminic (Avil®) to counteract the effect of histamine

3-Analgesics like cortisone (for its analgesic, anti-inflammatory and antihistaminic effect aside from rising blood pressure), however, cortisone has side effects like immuno-suppresion and delayed healing. One of the best analgesics anti-inflammatory to be used is Flunixine meglumine

4-Bronchodilator can be used like minophyline, if the animal exposed to high amount of smokes, and signs of respiratory distress are present, even tracheotomy is indicated if the dyspnea is so severe

5-Antibiotic for control of infection

6-Vitamin and minerals to stimulate healing

7-Administration of fluid therapy for correcting the hypovolemia, the best fluid therapy to be used is Ringer solution. The dose and the rate of infusion are very important; the doses that can be used depend up on the degree of dehydration that can be determined by measuring PCV in the light of total protein

Dehydration	Light	Moderate	Severe	Rate of infusion
Replacement dose	5%	8%	10%	10-20 ml/ kg/ hour
Maintenance dose	50 ml/ kg			2-4 ml/ kg/ hour

Prognosis: -

It depends on the extent of injury rather than the degree of burn, shock may ensue when more than 40% of skin involved, however, prognosis is unfavorable when more than 50% of the skin is affected. First-degree burns may last 10 days for healing, while second and third degrees need 4 weeks or more for healing.