Wound Healing Flashcards
four stages of wound healing
- hemostasis
- inflammation
- proliferation
- remodeling
hemostasis
formation of a blood clot to plug bleeding, provide a barrier to infection and fluid loss, and provide an initial substrate for wound healing
- immediate
- involves vasoactive substances, platelets, clotting factors, clotting proteins
steps of hemostasis
- bleeding
- release of vasoactive substances
- vasoconstriction
- vasodilation
- blood cells move into wound
- clotting cascade
- blood clot stabilizes wound
inflammation
bacteria and extracellular debris are removed from the wound by WBCs; blood clot stabilizes
- 1-7 days after injury
- involves neutrophils, macrophages
- minimal hemorrhage, less sharp wound edges, scab formation
steps of inflammation
- WBCs migrate to wound
- neutrophils kill bacteria, degrade debris, release cytokines
- monocytes proliferate and differentiate
- macrophages debride, kill, and strengthen clot
proliferation
granulation tissue (collagen and blood vessels) fill the defect to provide a barrier to infection
facilitates wound closure via contraction and epithelialization
- 3-35 days after injury
- involves macrophages, fibroblasts, ECM proteins, capillary endothelial cells, new epithelial cells
- rounded wound edges, granulation tissue forms, resistant to infection
steps of proliferation
- fibroblasts and endothelial cells migrate to wound
- new capillaries form and collagen accumulates
- ECM is replaced by red granulation tissue
- myofibroblasts contact wound edges
- epithelial cells grow inward from edges of wound
remodeling
collagen reorganizes to strengthen the closed wound; unneeded cells undergo apoptosis
- weeks to years
- involves macrophages, fibroblasts, matrix metalloproteinases, collagen
steps of remodeling
- wound loses vascularity
- type III collagen is replaced with type I collagen
- collagen reorganizes along tension lines
- wound gains tensile strength
- unnecessary cells undergo apoptosis
wound strength during inflammation
minimal strength
wound strength during proliferation
rapid strength gain
wound strength during remodeling
slow strength gain
how strong is the final scar
70-80% as strong as original tissue
ways of classifying wounds
- inciting injury
- degree of bacterial contamination
- type of closure
contusion
bruise
blunt trauma causes an accumulation of blood secondary to ruptured vessels
abrasion
partial thickness epithelial injury caused by blunt or shearing forces
minimal hemorrhage
rapidly healed by re-epithelialization
puncture wound
penetration of an object into the tissue
small opening with deep tissue contamination and damage
laceration
sharply incised skin edges that may extend into deep tissues
minimal peripheral trauma to wound edges
degloving injury
extensive loss of skin and underlying tissue
caused by scraping across a hard surface or excessive traction on extremity
thermal burn
close proximity of direct application of heat to skin
described by depth (superficial partial, deep partial, full thickness)
high risk of infection
radiation burn
secondary to external beam radiation therapy
takes weeks to present
decubital ulcer
compression of skin and soft tissue between a bony prominence and a hard surface leading to skin loss over bony protuberance
classifications by degree of contamination
- clean
- clean contaminated
- contaminated
- dirty
clean
controlled surgical wound into STERILE tissue compartments
clean contaminated
controlled surgical wound into GI, UG, or respiratory tracts
contaminated
- open, fresh, accidental wounds
- gross spillage from GI, UG, or respiratory tracts
- acutely inflamed tissues
dirty
- established infection
- old, traumatic wound
- devitalized tissues
- GI, UG, or respiratory perforations
when do surgical wound infections occur
when bacterial numbers and virulence exceed the host’s immune response
> 10^5 CFUs per gram of tissue
what are local or surgical factors that lead to infection
- amount of bacteria
- necrotic/devitalized tissues
- ischemia
- foreign material
- excessive hematoma or dead space
what are local or surgical factors that lead to impaired healing
- excess tension
- excess motion
- prior radiation at wound site
what are systemic factors that lead to infection or impaired healing
- long surgery/anesthesia
- hypotension
- hypothermia
- concurrent diseases
- immunosuppressive medications
what are steps of basic wound care
- clip and clean
- clean surrounding skin
- remove foreign material
- debride infected/necrotic tissue
- lavage with sterile saline
- repair
wound repair types
- open: cover with banadge
- closed: suture edges closed +/- drain
what are the types of closure
- first intention
- primary vs delayed primary - second intention
- third intension (secondary closure)
first intention healing
wound is closed SURGICALLY and BEFORE granulation tissue forms
IDEAL - fast, less new tissue formation
first intention - primary closure
immediate debridement, lavage, and closure
used on FRESH (<12 hours) and CLEAN wounds (ideally golden period)
golden period
the first 6 hours after the injury occurs
too soon to allow sufficient replication of microorganisms to cause wound infection
first intention - delayed primary closure
1-5 days of open wound management with bandaging followed by surgical closure (still before granulation tissue forms)
used on OLDER (>12 hour) and CONTAMINATED wounds with devitalized tissue
second intention healing
wound is closed NATURALLY via 4 stages of healing (contraction + re-epithelialization)
can used debridement and bandaging to support natural processes
SLOW with lots of new tissue formation
when to use second intention healing
large areas of tissue loss
dirty/contaminated
infected surgical wounds
financial limitations
third intention healing
wound is closed SURGICALLY and AFTER granulation tissue forms
open wound management followed by skin flaps/grafts/appositional closure
faster than second intention
when to use third intention healing
- severely contaminated, infected, or traumatized wounds
- large wounds in high motion areas
bandaging primary contact layer
sterile material applied directly to the wound surface
adherent or non-adherent
adherent
used for DIRTY/CONTAMINATED effusive wounds during inflammatory phase
provides mechanical debridement when removed
ex. gauze 4x4 sponges
non-adherent
used on HEALTHY GRANULATION TISSUE or minimally contaminated wounds
ex. Telfa pads or Adaptic gauze
bandaging secondary layer
holds the primary layer in place over the wound
ex. cotton wrap, cast padding
bandaging tertiary layer
provides support and protection
ex. vet wrap, elastikon
tie over bandages
bandage material applied and secured by umbilical tape tied through skin sutures
used when concentric bandages would be difficult to apply or maintain
ex. face, axilla, inguinal area, abdomen, proximal limbs, perineum
what are the two greatest indicators that primary closure is appropriate
- viability of tissues
- low contamination
what is the number one indicator that a wound will heal well
vascularization of the tissues
higher vascularization = greater ability to heal
