Principles of wound management
Healing and care
Learning outcomes
Having read this chapter, the reader should be able to:
A wound is any break in the skin and underlying tissues. Wound classifications mainly consider the extent, depth and causative factor. Midwives will be familiar with surgical clean contaminated wounds (caesarean section), lacerations (perineal tears or trauma to nipples) and punctures (cannulation, venepuncture, capillary sampling). Wound care is underpinned by an appreciation of the physiology of wound healing. This chapter considers wound healing and the factors that influence it, the care of caesarean section wounds, and the removal of wound closures. The reader will gain a holistic understanding by reading this chapter in conjunction with asepsis (Chapter 10) and perioperative skills (Chapter 51).
Physiology of wound healing
Healing of wounds begins following any injury to the body; an intact skin provides an efficient first line of defence against invading microorganisms. Wounds whose edges are in apposition (e.g. surgical wounds) heal quickly by first intention. Deeper, gaping wounds take longer to heal by secondary or tertiary intention. The process of wound healing is well documented, but sometimes the terminology used can vary (Nobbs & Crozier 2011). There are four phases of wound healing, using commonly recognized terms:
The length of time to progress through these phases varies for each wound and can be influenced by factors such as wound size, suturing, the clinical condition of the person, and the presence/absence of infection.
Haemostasis
This vascular phase begins immediately there is tissue damage. Vasoconstriction occurs to minimize bleeding (also initiating the coagulation process) and forming an obstacle to potential microorganism invasion. A fibrin clot forms, temporarily closing the wound. While the clot is forming, blood or serous fluid may exude from the wound as the body tries to cleanse the wound naturally.
Inflammation
The blood vessels around the wound dilate, causing localized erythema, oedema, heat, discomfort, throbbing, and sometimes functional disturbance. Macrophages clear the wound of debris in preparation for new tissue growth. A small necrotic area forms around the wound margin where the blood supply was interrupted. Epithelial cells from the wound margin move under the base of the clot, the surrounding epithelium thickens and a thin layer of epithelial tissue forms over the wound. As the clinical signs of the inflammation phase are similar to those of infection (see below), it is important the midwife can distinguish between a wound that is healing normally and one that is infected. Provided the wound is clean, this phase lasts between 1–3 days, but is prolonged in the presence of infection or necrosis (Sharp & Clark 2011).
Proliferation
This phase begins within 3 days in acute wounds and involves the growth of new tissue through three processes:
During granulation, capillaries from the surrounding vessels grow into the wound bed. At the same time, fibroblasts produce collagen fibres, providing the framework for new connective tissue formation. Collagen increases the tensile strength and structural integrity of the wound. Healthy granulation tissue has a bright red, moist, shiny appearance, a ‘pebbled’ looking base and does not bleed easily.
Once the wound is filled with connective tissue, fibroblasts collect around the edges of the wound and contract, pulling the edges together. A firmer, fibrous epithelial scar forms as the fibroblasts and collagen fibres begin to shrink, resulting in contraction of the area and obliteration of some of the capillaries. This only occurs with healthy tissue that has not been sutured.
During epithelialization, new epithelial cells grow over the wound surface to form a new outer layer, recognized by the whitish-pink, translucent appearance of the wound. The process is enhanced in a moist, clean environment.
Maturation
Once epithelialization is complete, the new tissue undergoes a time of maturation when it is ‘re-modelled’ to increase the tensile strength of the scar tissue. In lightly pigmented skin, the scar initially appears red and raised, and then with time changes to a paler, smoother, flatter appearance. Scar tissue in darkly pigmented skin has a lighter appearance initially when compared with lightly pigmented skin. Mature scar tissue is avascular and contains no sweat or sebaceous glands or hairs. Boyle (2006) suggests that scar tissue has 80% strength of the original tissue. The maturation phase begins after about 21 days and can take up to 2 years to complete. This may be the reason why some wounds that appear to have healed suddenly break down (Keast & Orsted 1998).
This healing process also occurs around sutures. When the sutures are removed, the epithelial cells can be dislodged and may be visible on the sutures as debris.
Assessing a wound identifies which of the healing stages the wound is in, as well as the appearance of the surrounding tissue and any observations for abnormalities, e.g. swelling, heat, pain, etc.
Wound healing by secondary intention occurs with deeper, wider wounds, whose edges cannot be brought into apposition. Inflammation may be chronic, with more granulation tissue forming at the expense of collagen during proliferation. Granulation tissue gradually fills the wound with re-epithelialization beginning at the edges. Healing by secondary intention takes longer, resulting in more scar tissue forming.
Factors that affect wound healing
• Temperature: a fall and a rise in wound temperature both cause vasoconstriction and so impair wound healing. Dixon et al (2014) found that the surgical site skin temperature post caesarean section was much lower than for other surgical interventions. The origins of this are as yet unknown, but they theorize that this is one reason for the higher incidence of surgical site infection for this group, a startling 10% (Wloch et al 2012). Milne et al (2012) also suggest that body temperature should remain above 36°C for the duration of the surgery.
• Infection: infection causes increased inflammation and necrosis, which delays wound healing. Many factors appear to contribute to infection, these are a few: poor surgical techniques (with an increased risk of haematoma (Olsen et al 2008)), poor dressing techniques, a larger number of people in theatre (Reilly 2002), inadequate or mistimed antibiotic prophylaxis (Kaimal et al 2008) and wounds that are too dry or too wet predispose to colonization or infection. A wound that is critically colonized has sufficient bacteria competing for oxygen and nutrients at the expense of healthy cells. It may not appear infected but will fail to heal.
• Psycho-social factors: good management of pain will reduce the woman’s anxiety, improve her acceptance of the wound, and so reduce stress. Anxiety, isolation, and altered body image all reduce wound healing (South et al 2008).
• Medical disorders: particularly those which impair circulation or tissue perfusion can delay wound healing. Diabetes mellitus includes the additional risk of hyperglycaemia, this can inhibit phagocytosis and predispose to fungal and yeast infection. Malignancy or the need for chemotherapy was also shown to have an adverse influence on wound infection rates (Reilly 2002).
• Impaired oxygenation: a low arterial oxygen tension may alter collagen synthesis and inhibit epithelialization. Poor tissue perfusion may occur in the presence of hypovolaemia, anaemia, obesity, smoking, poor mobility, and alcohol. Oxygen is necessary for fibroblast activity. Johnson et al (2006), Olsen et al (2008), the Joint Commission Perspectives on Patient Safety (JCPPS) (2008), and Nobbs & Crozier (2011) all relate obesity particularly with an increased risk of wound infection.
• Surgery-related care: NICE (2011) suggest specific surgical techniques for caesarean section surgery. Failure to undertake these procedures increases the risk of poor healing post-surgery.
The factors listed above are sometimes categorized as either intrinsic or extrinsic factors. These refer to the internal issues that relate to the woman, e.g. age, health, smoking, out of normal parameters for body mass index, presurgical rupture of membranes and those that relate to the external issues such as surgical technique, wound care, environmental hygiene, planned surgery and antibiotic prophylaxis. It becomes clear that the factors affecting wound management are considerable, significant and multidisciplinary.
Complications of wound healing
Haemorrhage
Haemostasis usually occurs within several minutes of an acute wound occurring. However, bleeding may occur if a bleeding point is not tied off, as a result of the clot or suture dislodging or infection, and may occur internally and externally. Internal bleeding can lead to haematoma formation.
Infection
Infection usually appears within 2–3 days following a traumatic injury or 4–5 days following a surgical wound. The wound site will appear red (often a spreading or tracking cellulitis), hot, swollen and painful. There may also be weeping from the wound, usually a yellow, green or brown discharge (depending on the infecting organism), it may also be malodorous. The woman may have pyrexia, tachycardia, a raised white cell count and a general malaise (Boyle 2006).
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