Physiology of wound healing

2. Physiology of wound healing Definition: A wound is a defect or break in the skin. • Wound causes • physical, • mechanical or • thermal damage • May also develop as a result of the presence of underlying medical pathology (circulation or nerve impairment, DM) http://www.en.elastoplast.ca/med-info/wound-care-and-advanced-healing/types-of-wounds.html

3. Mechanism of healing and repair • Healing is the replacement of destroyed tissue by living tissue. • Causes of tissue loss / destruction • Excision (surgical or accidental) • Necrosis (following inflammation, ischaemia, infarction, frostbite)

4. Regeneration and Repair of cells • Regeneration • Replacement of dead cells by proliferation of surviving cells of the same type. • Repair • Replacement of dead cells by scar tissue. In many cases regeneration and repair both occur. • Not all cells can regenerate (whereas some cells proliferate throughout life).

5. Cells can be divided into three types based on their ability to proliferate • Labile cells (mitotic cells) • Multiply throughout life examples include: • epidermis, • uterine endometrium, • blood cells, • epithelium of intestinal, respiratory and urinary tracts • Stable cells multiply to repair eg liver • Non-dividing cells eg nerve cells in the CNS (not glial cells)

6. PHASES OF normal WOUND HEALING

7. Inflammation Response The inflammatory response is triggered whenever body tissues are injured The response: Prevents the spread of damaging agents Disposes of cell debris Sets the stage for tissue repair 7

8. Phases of wound healing • The inflammatory phase • Blood vessels are the most likely structure to be damaged in case of injury. • First objective of the repair process of the body is to stop the bleeding. • Platelet aggregation and activation of the coagulation cascade result in blood clotting http://www.en.elastoplast.ca/med-info/wound-care- and-advanced-healing/types-of-wounds.html

9. Phases of wound healing: Inflammatory exudative 1-3 days approx • Damaged cells release histamine. • Histamine causes vasodilatation of the surrounding capillaries • Increased blood supply brings about oedema & engorgement resulting in the inflammatory appearance. • The exudate assists in dilution and flushing out of microbes and toxins • This is a natural response to injury and does not indicate infection • S&S: heat, redness, pain, swelling, loss of function http://www.en.elastoplast.ca/med-info/ wound-care-and-advanced-healing/types-of-wounds.html

10. Signs of Inflammation 10

11. Wound exudate • Is normal in the inflammatory stage and the substances present nourish and promote healing. • These substances are essential for healing. • If the inflammatory stage is impaired in some way then wound healing will be affected.

12. Phases of wound healing: • White blood cells, neutrophils and macrophages, begin the breakdown of any invading bacteria by phagocytosis. Destructive stage 1-6 days

13. Phases of wound healing Proliferative regeneration stage 2-3 days after injury (can last for weeks!) • Granulation • Contraction • Epithealisation • In this phase of normal healing the wound remains red and raised • New blood vessels formed • Wound contraction begins • Later stages proliferation occurs • Epithealisation occurs http://www.en.elastoplast.ca/med-info/wound-care-and-advanced-healing/types-of-wounds.html

14. Phases of wound healing Proliferative regeneration stage cont.. • Epithelial cells migrate and proliferate from the wound edges and hair – follicle remnants • The migration process can only occur in viable tissue and occurs until similar cells from the opposite edge are met

15. Phases of wound healing: Maturation (reparative) • In this phase tensile strength increases. This can take considerable time - 12 months or longer. • The maximum tensile strength (following wound breakdown and repair) that can be obtained is 80% of previous skin strength. • At first the wound is pink, but gradually contracts to become a pale scar. • Hair follicles and sweat glands that are lost in open wounds are usually not replaced. • These wounds cannot be thought of as completely healed and can break down again.

16. Categories of wounds • Wounds fall into two main categories • Acute • Chronic • This will have an impact on how the wound heals • Primary intention – minimal loss of tissue • Secondary intention – loss of tissue and healing is achieved through granulation • Tertiary intention (also called delayed primary closure) – closure is delayed (because of foreign body or infection) then closed CHISHOLM INSTITUTE 2012

17. Categories of wounds Acute wound • An acute wound is any surgical wound that heals by primary intention. • It is also any traumatic or surgical wound that heals by secondary intention that follows an orderly process of repair which results in restoration of anatomical integrity.

18. Categories of wounds Chronic wound • Occurs when the process of wound healing does not occur in an orderly fashion. • Healing is complicated by factors that impact on the patient, the wound or the environment.

19. Factors influencing wound healing

20. Factors influencing healing • Local factors • Blood supply • Persistent irritation • Direction of wound • Previous wounds • Systemic factors • Age • Nutrition • Health • Temperature

21. Factors influencing wound healing • Immunosuppression • Reduced immune response contributes to poor healing. • Cortisone depresses fibroblast activity and capillary growth and impairs wound closure. • Steroids mask inflammatory response • Chemotherapeutic drugs and some cancerous disease interfere with leukocyte production and immune response.

22. Factors influencing wound healing • Obesity • Less abundant supply of blood vessels in fatty tissue. • Suturing of adipose tissue difficult. • Prone to dehiscence or evisceration (and subsequently infection) • Extent of Wound • Deeper wounds with more tissue loss heal more slowly and by secondary intention and thus are more vulnerable to complications.

23. Factors influencing wound healing • Oxygenation • Reduced oxygen delivery inhibits wound repair. • Low arterial oxygen tension alters synthesis of collagen and formation of epithelial cells. • Wound heals more slowly when local blood flow is reduced and wound not exposed to oxygen. • Low hemoglobin levels (anaemia) reduce oxygenation and impede tissue repair.

24. Factors influencing wound healing • Smoking • Functional haemoglobin levels decrease. • Oxygen release in tissues is impaired. • Radiation • This may cause fibrosis and vascular scarring. • Irradiated tissues are fragile and poorly perfused. • Wound Stress • Sustained stress (eg vomiting, abdominal distension, coughing) disrupts wound layers and tissue repair.

25. Factors influencing wound healing • Diabetes Mellitus • People with Diabetes Mellitus, especially long-standing or unstable DM (type 1), have small vessel disease that impairs tissue perfusion. • Elevated blood glucose level impairs macrophage function. • Risk of infection is increased because of poor wound healing.

26. Nutrition • Tissue repair and infection resistance depend on a balanced diet – both macro and micro nutrients • Surgery, severe wound, serious infections, and preoperative nutritional deficits increase nutritional requirements.

27. Factors that affect wound healing in older adults • Changes in the anatomical structure of the skin • Reduction in the thickness of the epidermal and the subcutaneous layers • Skin loses turgor and is more fragile • Increased risk for injury from cleaning agents and tape

28. Factors that affect wound healing in older adults • Nutrition • Decreased secretion of enzymes and absorption of nutrients and minerals which may alter nutrition and delay wound healing • Potential for infection • Age reduces antibody production and functioning of endocrine system which increases susceptibility to infection • Chronic illnesses compromise circulation and oxygenation of tissues which further decreases resistance.

29. Factors affecting healing time: • Age of the person -Younger people heal more quickly than older people • Size - Smaller wounds heal faster than larger ones • Location - Epithelial tissue heals rapidly compared to other tissue types • Nutrition - Protein and vitamin C are essential to healing • Immobility - Wound tissue heals more rapidly if kept immobile

30. Factors affecting healing time • Circulation - Tissue with good blood supply heals faster • Organism virulence of infected wounds – wounds infected with virulent microbes are slower to heal than those that are not infected • Steroids – steroid therapy inhibits the inflammatory response giving the invading microbe the opportunity to thrive

31. Complications of wound healing

32. Complications of wound healing • Infection • Haemorrhage • Dehiscence • Evisceration • Fistula formation

33. Infection • firstaid.about.com

34. Dehiscence http://www.oup.com/uk/orc/bin/9780199534456/01student/scenarios/scenarios_ch08/page_02.htm

35. Evisceration • ijcasereportsandimages.com

36. Fistula formation http://www.ejomr.org/JOMR/archives/ 2010/3/e2/e2pic/Figure4.htm http://www.eakin.eu/casestudies/83/management_of_ a_complex_open_abdominal_wound.aspx

37. Keloid scar http://bestpractice.bmj.com/best-practice/monograph/629/resources/image/bp/12.html http://www.surgicalnotes.co.uk/node/370 http://doctorsgates.blogspot.com.au/2010/09/ keloids-pictures-and-therapy.html

38. Aseptic principles

39. Aseptic principles • Microorganisms are present in and travel on air currents. • Organisms from the oral cavity are spread into the air when talking or coughing may drop onto the sterile field. • Sterilisation indicators are used to demonstrate whether an object has been exposed to the sterilisation process. http://www.medical-evergreen.com/news/77/ ETO-Gas-Indicator-Tape.asp

40. Aseptic principles • Sterility expiration date indicates the last possible date on which the contents of the package can be assumed to be sterile. • Only intact wrappings protect sterile objects from contamination. http://dentistryandmedicine.blogspot.com.au/ 2011/09/equipments-instruments-and-materials.html

41. Aseptic principles • Any object is considered contaminated if its sterility is in question. • Sterile objects that are out of the line of vision are considered questionable or their sterility cannot be guaranteed. • Waist level and table levels are considered margins of safety that can be uniformly enforced and that promotes maximum visibility of the sterile objects.

42. Aseptic principles • A sterile object cannot contaminate a sterile field. • When a non-sterile object is held above a sterile object, gravity causes microorganisms to fall onto the sterile object. • A sterile object becomes contaminated when touched by a non-sterile object. http://www.medicalbox.org/dressingpacks.html

43. Aseptic principles • A general rule is that there is a 2.5cm margin of safety around the outside edge of a sterile field. http://www.farlamedical.co.uk/category_Wound-Care- Pack/Farla-National-Wound-Care-Pack/

44. Aseptic principles • That which is sterile remains sterile unless contaminated, but one part of an instrument may be sterile and another part contaminated as long as there is no question about what is sterile and what is not. http://www.wounds-care.com/manage/ uploadfile/20101011144504_890.jpg

45. Aseptic principles • Fluid flows downward by gravity. • Fluid that flows into a contaminated area becomes contaminated. • Fluid that is contaminated can flow back into a sterile area and contaminate it. • When a liquid connects a non-sterile surface to a sterile one, microorganisms may be transferred from the non-sterile area to the sterile area. • Microorganisms do not pass easily through a dry surface.