Wound is an injury or damage to a living tissue arising from different agents. There are different types of wounds caused by different agents with various degrees of severity. Some wounds are minor but others may be severe enough to cause loss of function of a whole organ, tissue or cell.
Causes of Wounds (Agents of Tissue injury)
- Mechanical agents
- Chemical agents
- Radiant agents
- Biological agents (pathogenic organism)
These agents are capable of causing tissue injury and death and will be discussed below based on their severity and mechanism by which each causes injury.
Mechanical agents causing wound
Wound can be caused by mechanical forces having an impact on a tissue. When a mechanical force acts on a tissue and causes injury with the wound remaining closed, it is said to a Contusion; when an open wound is caused by a mechanical force then such an injury is referred to as a Laceration. Therefore, Lacerations and Contusions are examples of mechanical injury inflicted on a living tissue. Other types of mechanical injury also exist.
Chemical agents causing wound
These refer to liquids or gases that are corrosive such as concentrated acids or strong alkalis (bases) and also poisons from bites of venomous snakes or insects that can inflict wound on a tissue. Examples of such include Hydrochloric acid (HCL), Sodium Hydroxide and some concentrated and corrosive gases. Chemical agents can cause tissue wounds by necrosis of the skin such as in snake bites, burns of the skin due to acids or by strictures of the esophagus as a result of drinking concentrated alkalis especially in children (a common household accident).
Radiant agents of tissue injury
Radiation could be in various forms such as X-rays, atomic energy, heat, high voltage electricity and intense cold. All of these can produce tissue necrosis.
These organisms do not directly cause wound but invade an already existing wound and causing extensive tissue necrosis and enlarging an already existing wound. The pathogens make use of chemicals known as toxins which help to dissolve tissue and can cause hypersensitivity reactions.
Types of Wounds (Classifications of Wounds based on nature of wound)
- Open wounds
- Closed wounds
- Contusion (Bruise)
- Perforating and penetrating wounds
Wounds however could be broadly classified as open or closed wounds. Under each major classification are different types of wounds as listed above.
These are wounds that occur without a loss of superficial surface covering the wound. The wound occur under the surface of the skin without affecting the skin. An example of this type of wound is contusion. Infection of these wounds is rare and it may resolve without any treatment if it is not extensive.
These are wounds in which there is loss of superficial surface covering the tissue such as loss of skin. Invasion by microorganisms is the main problem in open wounds.
Sub classifications of Open wounds (Examples of open wounds)
- Perforations or Penetrating wounds
- Punctured wound
Contusion or Bruise
This type of wound results from injury to the subcutaneous or sub mucous tissues and mostly results from direct blunt trauma. In contusion, there is disruption of the connective tissue and accumulation of blood in the disrupted tissue which then appears under the intact skin as bruise or ecchymosis. When the skin remains intact, it helps to prevent invasion of the underlying wound by microorganisms which may worsen the damaged tissue. In this type of wound, healing may occur but slowly.
An abrasion occurs when there is mere loss of the superficial layers of the skin. Abrasion is the simplest form of open wound. This is called an Abrasion. Wound healing following an abrasion may occur rapidly as the underlying hair follicles and subcutaneous glands help to replace the thin epithelium that is lost.
A puncture occurs when the point of entry of the mechanical agent causing the wound is small or pointed such as nail or narrow knife. In a puncture, the full thickness of the skin is penetrated and the wound is deeper than an abrasion.
This type of open wound occurs when the wounds point of entry is wider as compared to a puncture.
A penetrating wound occurs when the wound passes through a body cavity such as the abdomen or chest or pelvis. When the wound passes through an organ instead of a body cavity, it is said to be a Perforation and occurs such as in wounds caused by missiles.
Avulsions are wounds in which there is tearing of some portions of the body. Avulsions have irregular edges and may occur in scalp injuries or the limbs.
A Complete Avulsion there is no connection between the injured part of the body and its original site, that is, there is complete transection or division of the two parts that were joined together. Bleeding in complete avulsion rarely becomes life threatening as there is rapid retraction of torn blood vessels and the hemorrhage (bleeding is controlled).
A Partial Avulsion occurs when there are some parts of tissue connecting the torn parts of the body that were initially intact. Bleeding in partial avulsion is life threatening and needs immediate medical attention.
Wound Classification based on Contamination
Wound can be classified as Clean wounds (or Tidy wounds) or Contaminated (or Untidy wounds) based on their degree of contamination. This helps in management of the wounds.
- Clean wounds: this class of wounds have minimal risk of infection (1-2% infection rate) and include surgically incised wounds with complete adherence of all septic conditions without breech of any hollow viscera (this includes lipoma excision, thyroidectomy, simple herniorrhaphy, herniotomy and lumpectomy. There is no need of antibiotics use in clean wound except in immunosuppressed patients or patients having a prosthetic heart valve
- Clean contaminated Wounds: this type of wound has low risk of infection (<10% infection rate). This type of wound includes wounds involving entry into hollow organ that is not inflamed and entry into abscess cavity, minor bridge in aseptic procedure, mild spillage of intra-abdominal viscous. These wounds occur during uncomplicated appendectomy and interval cholecystectomy. Prophylactic treatment with antibiotics is required.
- Contaminated wounds: This have high rate of infection (15-20% infection rate). This occurs when there is a major breach in aseptic condition even without entry into abscess cavity or hollow viscus. Contaminated wounds are created de novo such as in contamination of bile and feces, complicated appendectomy, colostomy and cholecystectomy. Therapeutic antibiotics aimed at treatment and not prophylaxes are given.
- Dirty or Infected wounds: These have very high risk of infection (>40% infection rate). Dirty wounds appear grossly infected with pus with entry into an abscess cavity such as in gangrenous bowel.
Management of Wounds
The aim of treatment is to aid in wound healing and preventing complications by converting contaminated (untidy) wounds to clean (tidy) wounds.
Principles of Wound Treatment and Wound care
- Debridement: this involves the removal of all dead and dying tissues and also all foreign materials to avoid invasion by microorganism. This is done by first irrigating the wound normal saline or clean water with soapy antiseptic to remove ingrained pieces.
- Strict Aseptic procedure: Any surgical procedure should follow strict aseptic technique by wearing gowns, caps and efficient masks and usual skin preparation and draping
- Wound closure: this should be done when debridement has been performed and the wound has been converted to a clean wound. The correct surgical procedure should be done and correct surgical sutures should be used.
- Careful handling of tissues: further damage to the already wounded tissue should be avoided by gently handling the tissues.
- Reduce Blood loss: bleeding should be controlled immediately and blood transfusion should be carried out where necessary.
- Immobilization and elevation of the injured part: this is essential to encourage venous and lymphatic drainage and also prevent congestion and pain.
- Prophylaxis drugs: prevention of tetanus by active or passive immunization should be given where significant wound contamination is suspected; broad spectrum antibiotic prophylaxis should also be given.