Wound healing

wounded tissues are striving to achieve what?

homeostasis

what are the 3 phases of wound healing and their timeline?

• inflammatory phase: 1-10 days (damage control)

• proliferative phase: 3-20 days (repair begins)

• remodeling phase: 9 days-2 years (scar matures)

if someone has a paper cut from 9 days ago, what phase of healing are they in? how does this change if it is a much bigger wound?

they are in the remodeling phase; the bigger wound would still be in the inflammatory phase

what types of cells are not permanent residents but migrate through healthy tissue and collect at the site of tissue injury?

• fibroblasts

• fibrocytes

• myofibroblasts

• lymphocytes

• macrophages

• mast cells

• keratinocytes

• specialized cells such as platelets

what are fibroblasts?

baby cells from where connective tissue derive

what are fibrocytes?

grown up fibroblasts

what are myofibroblasts?

fibroblasts that contract

what is the role of macrophages? what happens if macrophage levels drop?

they dissolve dead tissue and keep the patient alive ; the chances of the patient surviving their wound also decreases

what is the role of mast cells?

they hang around the base of blood vessels dormant and when called upon they produce histamine

what are the cells that make skin strong?

keratinocytes

why are platelets essential in wound healing?

they release serotonin

what are the fibrous elements of CT?

• collagen

• elastin

• reticulin

the most abundant part of connective tissue is ___ and the patient has to have it in order for the wound to ___ because?

collagen; close and heal because it is very strong

what does elastin do to connective tissue? why is it important in wound healing?

adds elasticity to CT; if you don’t have it the scar will be stiff

what is reticulin? why is it important ?

a protein substance that creates a net-like protein that cradles vessels such as arteries, veins, and lymph vessels; if you didn’t have this, when you raise your arms all vessels would drop to the bottom of your arm

what is ground substance? what are some characteristics of ground substance?

a filler substance that surrounds cells and fibers;

• it is clear, viscous, and colorless

• it is the consistency of maple syrup but can be more or less thick

• thickness will slow the movement of bacteria, makes them easier to catch

what is unique about the viscous properties of ground substance?

in hot temps, it becomes liquid-y and in cold temps it thickens but in wounds, you want it to be in the middle and not too liquid-y because its role is to slow down pathogens as it flows through so don’t put extreme warmth on the wound

what happens in the inflammatory phase?

• platelets release serotonin to cause vasoconstriction to control the bleeding and give the body a chance to think about what to do next which is why it takes a minute to feel pain and to know how deep a wound is

• mast cells release histamine to bring more lymph fluid and blood into the area to bathe the wound and help cells become more permeable

• more fluid means edema and prostaglandins are being released to manage the swelling and enhance healing via signal regeneration

• necrosis occurs and macrophages get the signal to come in to eat the dead cells

• pathogens also get the same signal and WBCs come to fight the pathogens which may cause WBCs to elevate in lab tests

___ accounts for 65% of all circulating WBC and buy time for the other cells to get to the wound site in the inflammatory response

macrophages

which WBCs rush to the wound site during the inflammatory response to fight the pathogens?

• granulocytes-polymorphonuclear leukocytes (PMNLs): the first WBCs on the scene

• erythrocytes

• leukocytes

• platelets

• plasma protein

what do plasma proteins do? what is significant about plasma proteins?

they stop leaks; it is another lab test to see if the patient is likely to heal the wound on time

lymph nodes may swell during the ___ phase due to ___. what is significant about this?

inflammatory phase; the WBCs rushing to the site to fight pathogens; you don’t want to take antibiotics too soon because the WBCs need to do their job so only be concerned about the lymph node swelling if its been past 4 weeks

do you want to aggressively clean the wound in the inflammatory phase?

if it is infected, then yes to get rid of the pathogens but if it is not and its just inflammation, don’t clean too much because you don’t want to disrupt the healing

what happens in the proliferative stage?

• first is fibroplasia where fibroblasts and myofibroblasts are attracted to wound site via a chemical mediator from the inflammatory phase

• fibroblasts follow behind macrophages to make a new clean path as they clean up the dead cells

• myofibroblasts attract endothelial cells to lay down the ground work for closing of the wound and to make new blood vessels

• epithelial cells make new skin cells

• granulation and angiogenesis occur, and granulation tissue allows the cells to cross over to the other edge of the wound

• then re-vascularization occurs only over healthy granulation tissue and lymph vessels also form nearby

• finally wound closure occurs where skin is growing over the wound but it is not yet healed

angiogenesis occurs in the ___ phase and is the result of what?

proliferative phase; the result of endothelial cells forming new capillaries to perfuse the collagen matrix so that it can provide a base for epithelial cell migration

what is granulation tissue and which phase do you see it in?

a tissue which is highly vascularized with capillaries and consists mainly of macrophages, fibroblasts, and endothelial cells that are all embedded in a matrix of fibronectin, proteoglycans, hyaluronic acid, and collagen; proliferative phase

our job is to encourage ___ in wound healing because?

granulation tissue formation ; cell proliferation can only happen across granulation tissue and if it does not form, it can cause a patient to be stuck in the inflammation phase for months

___ is essential for wound healing

revascularization

a wound can close by what 3 ways?

• primary intention: surgeon closes wound by bringing edges together

• secondary intention: contraction and re-epithelization

• tertiary intention: delayed primary intention where it attempted to heal via secondary intention but had to be closed by the surgeon, usually due to infection

what is dehiscense?

a wound closed by primary intention that later opens up again due to maceration or infection has opened by the process of dehiscence

is wound closure the same as wound healing?

NO

big abrasions and burns are always closed via which intention?

secondary intention

what are the 2 ways secondary intention wound closure can occur?

• closure by contraction where the peri-wound tissue moves toward the center via myofibroblast activity

• closure by re-epithelialization where epithelial cells form around the edges of the wound and migrate towards the middle

the deeper the wound is, the more likely it is going to close via which way if it is left to close by secondary intention and why?

contraction rather than re-epithelialization because it is quicker. if it is a shallow wound it will likely close via re-epithelialization

what is unique about secondary intention closure via re-epithelialization?

• it can only occur over healthy, clean, and moist granulation tissue which is why it takes longer than contraction

• it begins within hours of wounding

what can go wrong with secondary intention closure via re-epithelialization?

• presence of eschar (have to remove it before wound can close)

• dry wound environment (don’t dry out the wound via hair dryer or in the sun)

• too much cleansing

• toxicity (too much hydrogen peroxide, alcohol, etc)

• confused cellular messaging in inflammatory phase which can cause epithelial cells to go back to the edges and form a pre-mature scar

are you supposed to use hydrogen peroxide or alcohol to clean a wound?

you can use it on the first or second day but don’t do it too much because it can prevent re-epithelialization

what are the 4 phases of re-epithelialization

• mobilization of epithelial cells

• migration of epithelial cells

• proliferation of epithelial cells

• differentiation of epithelial cells according to the skin they came from

what is contact inhibition?

when epithelial cells that migrate across a wound bed during re-epithelialization come in contact in the middle and are prevented from piling on top of each other in the middle of the wound bed

what are some considerations for wound closure and healing?

as deeper wounds heal, the repair process does not replace lost muscle, fat, or dermis with like tissue but instead with granulation or scar tissue that is made up of mainly collagen, meaning a wound that is closed and healed does not return to its pre-wounded state

what happens in the remodeling phase of wound healing? what is significant about the remodeling phase?

collagen is remodeling, creating cross links, and increasing in tensile strength ; connective tissue heals back to 80% of its original strength

what are things that can go wrong during the remodeling phase?

• hypertrophic scarring

• keloid scarring

what is hypertrophic scarring? how is it different than keloid scarring?

scar tissue that triggers excess collagen deposition most likely due to faulty chemical messaging; the excess collagen stays just in the wound area

what is keloid scarring? how is it different than hypertrophic scarring? can you shave it off?

when connective tissue starts to creep outside the wound area due to excess collagen deposition; it exceeds the margins of the original wound; you can surgically shave it off but it will most likely come back

what are intrinsic factors that affect wound healing?

• infection

• poor nutritional status of the wound

• medications such as chemical inhibitors

• skin aging

• radiation/chemotherapy

• abnormal wound repair

• uncontrolled pathology such as DM

if you suspect a wound of infection what should you do?

you have to do a tissue culture because it is the only way to confirm a true infection as all wounds are contaminated but only some are infected

what does a tissue culture tell us?

what the bioburden of the wound is or the number of organisms with which an object is contaminated

what is biofilm ? is its present in ___% of chronic wounds and ___% of acute wounds

a complex communities of bacteria that adhere to solid surfaces and can prevent you from doing your treatments; 60% chronic, 6% acute

what are things that can happen if a wound is infected that can slow down healing?

• infection slows down cellular activity and decreases collagen metabolism

• decreased oxygen availability because pathogens are absorbing it

• increased rate of cellular necrosis because macrophages can’t keep up

• wound sepsis (septicemia)

• osteomyelitis

• gangrene

if a wound is swollen and red does that indicate infection? what about odors?

it can but you need a tissue culture to confirm; odors do not always mean it is infected so you would need a tissue culture

if you read the lab results and the patient’s WBC count is decreasing, what does that mean?

that there might be a decrease in cellular activity due to infection because you want to see some elevation in WBC

what is wound sepsis? is it the same as infection?

when micro-organisms overpower the wound and affect blood flow to vital organs which can kill the patient ; no

what is osteomyelitis?

inflammation of the bone marrow, adjacent bone, and epiphysial cartilage

what is gangrene? what are the 2 types and what is the difference between them?

necrosis due to obstruction of blood supply; dry and wet; dry is more common and stays local so if you amputate it it will be okay. wet is much worse because it can spread throughout the body

what population is at risk of delayed wound healing due to poor nutritional status?

• elderly who don’t eat well

• the unhoused

• the neglected

what meds can become chemical inhibitors that delay wound healing?

• aspirins

• steroids

• NSAIDs

why is skin aging a challenge to normal wound healing?

• the epidermis and dermis is stuck together via rete pegs and as you get older, the moisture goes down and the pegs wear down so the epidermis is just hanging onto the dermis and allows for tearing/shearing injuries to happen more easily

• the dermis has decreased collagen production starting at age 30, meaning the skin is less elastic and has impaired angiogenesis so they don’t close wounds as quickly

• subcutaneous adipose tissue begins to decrease which causes less padding on bony prominences and increases risk of pressure injuries

what is photoaging?

premature aging of skin caused by repeated exposure to UV

what are clinical considerations of skin aging?

• results of irritation linger longer

• sheering risks

• difficult to diagnose infection

• decrease in pain sensation

• propensity for pressure injuries

how does radiation and chemo affect wound healing? what is the clinical implication if someone has had surgical resection of a tumor?

both stimulate intrinsic delays in healing because they change tissue composition because radiation destroys cells and chemo slows healing ; if they had surgery to remove a tumor and have radiation/chemo after, their chances of delayed wound healing is big

what are the 2 types of abnormal wound repair?

• hypergranulation where granulation gets out of control and epithelial cells form a scar around the edges

• hypo-granulation where the chemical messaging is off

what are environmental factors that can affect healing?

• incontinence

• smoking, alcohol, recreational drugs, poor diet

if a patient smokes, it can take ___ minutes for the foot to get normal blood flow again

7 minutes

what are iatrogenic factors affecting healing?

• risk of infection

• choice of dressings and handlings of dressings

• choice of cleansing method

• repeated or unprotected pressure

• use of topical agents, misuse of cytotoxic agents

every time a wound is flushed/cleaned, it takes ___ hours to warm up again. what is the implication of this?

3-6 hours; if you or a patient is cleaning a wound 3 times a day or more, the wound never gets back to normal blood flow which can impact healing

a wound that is not infected can be cleaned once and covered for up to how many days?

5 days

should you debride a wound until it bleeds?

no it is against the law, we should only debride dead tissue so we should never see blood

should we be packing a wound to get it to granulate?

no because new tissue is very fragile and does not like a lot of pressure and it will slow down closure

what are some considerations about inflammation?

• inflammation is necessary but must end on schedule

• the timing of the end of inflammation is often delayed due to human error

should you be removing endogenous fluids out of a wound?

no, it should be managed but not entirely removed

wound ___ occurs long before wound ___

closure; healing

___ is essential to wound healing and a major part of treating patients in wound care is how to get more ___

blood flow; blood flow