Primeros Auxilios en Heridas

Wound Management

The role of the veterinarian who provides primary care to patients with open wounds is vital, having a direct influence on the chances of recovery.

These patients should be treated by ABC emergency protocol, giving priority to stabilization. It is common for large non-life-threatening wounds to distract the inexperienced clinician from more serious problems such as chest trauma, hemorrhagic shock or encephalic trauma. Meanwhile, other not so impressive wounds sometimes compromise patient's life and require immediate intervention (pervasive chest, jugular laceration).

External bleeding must be stopped by applying pressure with a clean bandage covering the wound site. If bleeding does not stop, a second layer of bandage should be applied. These bandages should only be removed in the operation room. Tourniquets are contraindicated because they might aggravate the bleeding if the pressure is enough to obstruct venous return but not arterial blood flow and they might induce neurovascular damage if they are too tight.

To prevent further contamination during patient handling cover open wounds with a sterile dressing. This is particularly important in cases of penetrating abdominal wounds and evisceration, pneumothorax, open fractures and partial amputation of limbs, having a direct effect on prognosis. Immobilize fractures below the elbow and the knee with a splint. Never reduce an exposed bone fragment because it will take pollutants into deeper tissues.

The treatment goal is to convert a contaminated or infected wound into a clean surgical wound that can be surgically closed. An aseptic technique, proper handling of tissues and appropriate hemostasis are essential.

Systemic antibiotic therapy should be implemented before handling the wound. If treatment is started during the first three hours, we will ensure an adequate level of antibiotic in the wound fluids, before the bacteria are protected within fibrin networks.

Cephalosporin, amoxicillin or ampicillin are a good antibiotic choice because of their wide range of antimicrobial activity and good tissue penetration. In heavily contaminated wounds a combination of systemic and local antibiotics as nitrofurantoin dressings is a better choice. The selection of antibiotic can be based on Gram stain from the wound. Culture and sensitivity testing of a wound swab might introduce a change in antibiotic selection.

Wound Preparation

Sedation or general anesthesia may be required. Patients with increased anesthesia risk can be treated by local or regional infiltration of local anesthetics, combined or not with neuroleptanalgesia. Direct wound infiltration is acceptable once the wound has been properly prepared. To prevent further contamination of the wound with hair and other contaminants, cover the wound using sterile water-soluble gel or sterile gauze soaked in saline. The cornea and conjunctiva should be protected by instilling ophthalmic ointment in wounds that are close to the eyes. Clip a wide area. The hair located at the wound edges can be clipped with sterile scissors dipped in saline solution or mineral oil; hair will adhere to the scissors edges instead of falling into the wound. Wash the area with chlorhexidine soap solution and then to 0.2% iodine povidone solution. The use of 3% hydrogen peroxide is contraindicated.

Wound Debridement

Wound debridement is performed under aseptic surgical conditions. The aim is to remove all devitalized contaminated or infected tissue and debris from the wound in order to transform it into a surgically clean wound that can be closed by primary intention. Sharp dissection is the best debridement method; surface tissue scarification should be avoided.

There are two basic techniques, layered or en bloc debridement. The first one consists on removing all the tissue as if it were a tumor, it removes all contaminated tissue but it is restricted to areas where the abundance of tissue allows proper closure.

Layered dissection involves the removal of devitalized tissue using a selection criterion retaining those that eventually may be needed for wound closure. Severely damaged edges that lack irrigation should be cut.

It is critical to restore venous drainage of turgid dark flaps. If they present a clear demarcation line should be cleaved a few millimeters proximal to the demarcation line. If there is no demarcation groove, it is preferable to preserve the flap and re-evaluate it in 48 hours. Dorsal based flaps are more likely to survive than those with a ventral base.

Muscle viability is assessed based on four Cs: color, consistency, circulation and contractility. All nonviable muscle tissue must be removed.

Bone fragments should be preserved whenever possible and are essential not to interfere with the soft tissue junction. If you suspect articular penetration distant to injury joint sac should be located, and aseptically prepared, then introduce 5 ml of sterile saline and look for fluid flow through the wound. If it tests positive, the joint should be washed with plenty of sterile saline and 0.05% chlorhexidine. Joints should never be inspected through the wound bed because bacteria could be inoculated.

Occasionally debridement may be performed in stages. All obviously devitalized tissue should be removed leaving all the dubious tissue. A bandage is applied and at each dressing change all non-vital tissue is removed.

Wound Wash

Fluids infused at high pressure can be used to remove contaminants, clots, tissue debris and to reduce bacterial population.

Plenty amount of fluids should be used (1–2 liters) and discontinued before tissue acquire a discolored and edematous appearance.

A suitable pressure of at least 7 psi can be obtained with a 20 to 60-cc syringe and an 18 to 19-G needle.

Repair Procedures

After wound cleaning and debridement the clinician must decide if the wound can be closed using sutures or if we should allow closure by contraction and epithelialization. Whenever possible, wounds should be sutured.

If you decide to leave it open a proper dressing for the wound healing phase in should be chosen. Adherents' bandages are preferred during the debridement phase, and then non-adherent bandages are used.

The contact layer of an adhesive bandage may be sterile gauze; the extensive network traps necrotic tissue and foreign material and adheres to the surface of the wound thus helping to complete the debridement at each dressing change. The most common adhesive bandages are designed as wet to-dry and dry-to-dry; and should be replaced every 24 to 48 hours.

Non-adherent dressings are indicated for wounds that are in the repair phase, presenting a healthy granular bed, a degree of serosanguineous discharge and epithelialization from the edges. These bandages are generally semi-occlusive because they retain sufficient moisture to prevent dehydration and promote epithelialization, while allowing fluid absorption from the wound into the intermediate layer, thereby preventing maceration of tissues.

The contact layer is gauze impregnated with propoleum or nitrofurazone. They can remain in place for up to 5 or 6 days depending on the degree of wound exudation.

All bandages should be applied as "physiological", so that they are firmly placed without interfering venous or lymphatic return.

Complete healing of large defects in areas of loose skin is one of the biggest advantages of contraction. The disadvantages of this process include the formation of rigid skin bridges over flexor surfaces, which severely limit the possibility of movement; stenosis of natural orifices; insufficient shrinkage; and stiffness of the skin after a wide contraction produced limiting body movement.

All these cases require reconstructive surgery in order to correct the defect. Epithelialization can take weeks, and in extensive wounds does not provide adequate coverage in the central area, because this epithelium is so delicate that easily comes off. This epithelial tissue lacks normal skin annex structures as hair and glands. Therefore, the patient may require the use of flaps in certain areas whether for cosmetic reasons or to avoid the repeated trauma of this delicate epithelium.

References

1.  Swaim SF, Henderson RA. Wound healing. Small Animal Wound Management. Baltimore, MD: Williams & Wilkins; 1997.

2.  Swaim SF, Henderson RA. Wound management. Small Animal Wound Management. Baltimore, MD: Williams & Wilkins; 1997.

3.  Swaim SF, Henderson RA. Wound dressing materials and topical medications. Small Animal Wound Management. Baltimore, MD: Williams & Wilkins; 1997.

4.  Swaim SF, Henderson RA. Specific types of wounds. Small Animal Wound Management. Baltimore, MD: Williams & Wilkins; 1997.

5.  Stashak TS. Principles of wound healing. Equine Wound Management. Lea & Febiger; 1991.

6.  Stashak TS. Selected factors that affect wound healing. Equine Wound Management. Lea & Febiger; 1991.

7.  Stashak TS. Principles of wound management and selection of approaches to wound closure. Equine Wound Management. Lea & Febiger; 1991.