Factors affecting wound healing

Factors affecting wound healing includes local factors, systemic factors, Medications and underlying systemic disease.

Local factors affecting wound healing

Good surgical technique is warranted for proper wound healing if Halsted’s principles are followed. The principles include- Gentle handling of tissue, Aseptic surgical technique, Perfect haemostasis and preservation of blood supply to the wound area,Close tissue approximation and obliteration of dead space and Removal of necrotic and devitalized tissue.

Tissue vascularity ensures oxygenation and nutrients which is essential for wound healing. Oxygen influences angiogenesis, epithelialization and resistance to infection.

Infection is one of the major factors which retard the wound healing significantly as it prolongs the inflammatory phase, disrupts the normal clotting mechanisms, promotes disordered leukocyte function and ultimately prevents the development of new blood vessels and formation of granulation tissue.

Topical medications promote wound healing by minimizing bacterial infection. However, certain antimicrobial agents and local anaesthetics delay the healing process by destroying cellular elements of wound.

Lavage and dressings accelerate wound healing by protecting healing tissue. Lavage with sterile isotonic solutions like normal saline decreases the concentration of the microorganisms mechanically and aids in healing process. Non-adherent, moist dressing triggers epithelisation whereas adherent gauge dressing mechanically debride the contaminated wound.

Presence of foreign bodies such as tissue debris, dirt, soil, sequestrum, or nonabsorbable braided suture materials delay the healing process by exacerbating the inflammatory response and inciting infection.

Obliteration of dead space and prevention of fluid accumulation promote migration of reparative cells and minimizing the risk of infection during wound healing.

Ionizing radiation retards wound healing by decreasing fibroblast formation, collagen synthesis and neovascularisation within fortnight of surgery.

Movement of the wound site prolongs the healing process as movement can disrupt cell migration, neovascularisation and formation of early ground substances of the wound.

Mutilation of the wound not only disturbs the healing but also complicate by creating evisceration like condition.

Systemic factors affect healing

Advanced age retards healing because of reduced skin elasticity and collagen replacement. The immune system also declines with age making patients more susceptible to infection. Older animals are also susceptible to other chronic diseases, which affect their circulation and oxygenation to the wound bed as compared to young.

Nutrition plays a pivotal role in wound healing process.

Protein is required for all the phases of wound healing, particularly important for collagen synthesis. Hypoproteinemia slows healing by decreasing wound tensile strength, delaying fibroplasia and producing edema.

Glucose balance is essential for wound healing. Hyperglycemia delay wound healing.

Iron is required to transport oxygen.

Minerals like zinc, copper are important for enzyme systems and immune systems. Zinc deficiency contributes to delay epithelisation and disruption in granulation tissue formation by inhibiting fibroblastic cellular proliferation.

Vitamins A and B complex are responsible for supporting epithelialization and collagen formation. It is also important for the inflammatory phase of wound healing.

Vitamin C is essential for formation of intercellular cementing substances as it is needed for hydroxylation of the lysine and proline moieties of collagen.

Carbohydrates and fats: These provide the energy required for cell function. When the patient does not have enough, the body breaks down protein to meet the energy needs. Fatty acids are essential for wound healing.

Medications affecting wound healing

Anti-inflammatory, cytotoxic, immunosuppressive and anticoagulant drugs all reduce healing rates.

Anti-inflammatory drugs like corticosteroids if used in long term and at higher doses impair the inflammatory phase, decrease fibroplasia, collagen synthesis and neovascularisation.

Chemotherapeutic agents like methotrexate, doxorubicin and cyclophosphamide delay the wound healing process by inhibiting cell division or collagen synthesis. In addition, healing process is adversely affected by depressing immune function, epithelialization and contraction.Anticoagulant drugs retard the healing by interrupting clotting mechanism and thus making a wound more prone to infection due to presence of blood clots.

Most NSAIDs lower resistance to infection and ultimately delay healing.

Systemic disease affecting wound healing

Systemic diseases like malignancy, uncontrolled diabetes, renal and hepatic disturbances delay healing process.

A malignancy in the body retards wound healing by altering metabolism, producing chachexia, and minimizing inflammatory cell division.

Uremia delays fibroblastic proliferation, granulation tissue formation, epithelial proliferation and subsequently strength of healing wund.

In patients with uncontrolled diabetes, there is delayed healing as hyperglycemia impairs collagen formation, neovascularisation, granulocytes cell functions and ultimately leading to wound dehiscence.