Cell injury Cell injury

Cell injury Cell injury When the cell is exposed to any injurious agent or stress ,a consequence of events follows, that is loosely termed cell injury.cell injury. Cell injury is reversible up to certain point.

To survive, cells must have the ability for adaptationadaptation to variable conditions. This process of adaptation can involve changes in cellular size, number or type.

If the stimulus persist or severe enough from the beginning , cell deathcell death occur .

Cell Adaptation to Cell Adaptation to InjuryInjury

Five Cellular Adaptations to Injury:

1. Atrophy

2. Hypertrophy

3. Hyperplasia

4. Metaplasia

5. Dysplasia

Cell Adaptation Cell Adaptation to Injuryto Injury•It means Decrease or shrinkage in cellular size.•That is either Physiological or Pathological•Pathologic atrophy occur due to ↓ ↓ ↓ in :

• Workload( گرفته گچ (اندام• Pressure• Use• Blood supply• Nutrition• Hormonal Stimulation• Nervous Stimulation

•Atrophy is generally a reversible( پذیر ,process (برگشتexcept for atrophy caused by loss of nervous innervations to a tissue.•Causes of atrophy include prolonged bed rest, disuse of limbs or tissue, poor tissue nutrition and ischemia.

1) 1) AtrophyAtrophy

Cell Adaptation Cell Adaptation to Injuryto Injury Increase in cell size and tissue mass.

Occurs when a cell or tissue is

exposed to an increased workload(بار کاری).

Occurs in tissues that cannot

increase cell number as an adaptive response.(عضله قلبی، ورزشکاران)

Hypertrophy may be :

normal physiologic response, such as the increase in muscle mass that is seen with exercise

pathologic as in the case of the cardiac hypertrophy that is seen with prolonged hypertension.

or compensatory(ج�برانی) process, when one kidney is removed, for example, the remaining kidney hypertrophies to increase its functional capacity.

3) 3) HypertrophyHypertrophy

Cell Adaptation Cell Adaptation to Injuryto Injury Increase in number of cells resulting from increased rate of

cellular division.(افزایش سلولهای جدید)

It is either:

Physiologic process, as in the breast and uterine hyperplasia that occurs during pregnancy,

Pathologic: such as Benign Prostatic Hyperplasia (BPH) and gingival hyperplasia (overgrowth of gum tissues) that maybe seen in certain patients receiving the drug phenytoin.

or compensatory mechanism: for example, when a portion of the liver is surgically removed, the remaining hepatocytes (liver cells) increase in number to preserve the functional capacity of the liver.

2) 2) HyperplasiaHyperplasia

Cell Adaptation Cell Adaptation to Injuryto InjuryThe conversion of one cell type to another ( بالغ سلول یک (تغییر

cell type that might have a better chance of

survival under certain circumstances.

Metaplasia occurs in response to chronic irritation or inflammation.

An example of metaplasia is:

in the respiratory passages of chronic cigarette smokers.

4) 4) MetaplasiaMetaplasia

Cell Adaptation Cell Adaptation to Injuryto Injury5) 5) DysplasiaDysplasia

• A derangement(اختالل) of cell growth that leads to tissues with

cells of varying size, shape and appearance.

Dysplasia may be a strong precursor to cancer such as in the cervix or respiratory tract. However, dysplasia is an adaptive process and as such does not necessarily lead to cancer.

خود سابق عملکرد و ساختار به دیسپالستیک های سلول موارد، از بسیاری در. گردند بازمی

• Generally occurs in response to chronic irritation and

inflammation.

Physical injury• Mechanical trauma• Temperature extremes (burn injury, frostbite)• Electrical current

Chemical injury• Chemicals, toxins, heavy metals, solvents,

smoke,• pollutants, drugs, gases

Radiation injury• Ionizing radiation — gamma rays, X rays• Non-ionizing radiation — microwaves, infrared,

laser Biologic agents

• Bacteria, viruses, parasites Nutritional injury

• Malnutrition• Obesity

Classification of Cellular Classification of Cellular injury injury

Although the causes of cellular injury are many ,

the underlying mechanisms of cellular injury

usually fall into one of two categories:

free radical injury

hypoxic injury

Cellular injuryCellular injury 1)Free radical injury

Free radicals are highly reactive chemical species that have

one or more unpaired electrons in their outer shell.

Examples of free radicals include superoxide (O−2),hydroxyl

radicals (OH−) and hydrogen peroxide(H2O2).

Free radicals are generated as by-products of normal cell

metabolism and are inactivated

Injury to cells occur when:

• excess free radicals are formed from exogenous sources or

• the free radical protective mechanisms fail.

Free radicals are highly reactive and can injure cells through:

1. Destruction(تخریب) of membrane lipids.

2. Damage of cellular proteins.

3. Mutation of cellular DNA.

Exogenous sources of free radicals include tobacco smoke, organic solvents, pollutants, radiation and pesticides.

Free (توتون و تنباکو دود، حالل های آلی، آالینده ها، تابش و سموم دفع آفات) radical injury has been implicated as playing a key role in:

1.The normal aging process.

2.Number of disease states such as diabetes mellitus, cancer,

atheroscelrosis, Alzheimer’s disease and rheumatoid arthritis.

Cellular injuryCellular injury 1)Free radical injury

Cellular injuryCellular injury 2)Hypoxic cell injury

• Hypoxia is:

a lack of oxygen in cells and tissues that generally results from

ischemia.

• The hypoxic cellular injury process is either:

1. reversible, if oxygen is quickly restored,

2. Or irreversible( ناپذیر and lead to cell (برگشت

death. Certain tissues such as the brain are

particularly sensitive to hypoxic injury. Death

of brain tissues can occur only 4 to 6 minutes

after hypoxia begins.

During periods of hypoxia:

1. Aerobic metabolism of the cells begins to fail.

2. This leads to dramatic decreases in energy production (ATP) within the cells.

3. Hypoxic cells begin to swell as energy-driven processes begin to fail, (such as ATP-driven ion pumps).

4. The pH of the extracellular environment begins to decrease as waste products begin to accumulate, such as lactic acid, a product of anaerobic metabolism.

5.Accumulation of intracellular calcium, which is normally closely regulated within cells. There are a number of calcium-dependent protease enzymes present within cells that become activated in the presence of excess calcium and begin to digest important cellular constituents.

Cellular injuryCellular injury 2)Hypoxic cell injury

Reversible and Irreversible Cell Injury

Reversible: Irreversible: Decrease generation Sever

of ATP mitochondrial Loss of cell

changes membrane integrity Persistent or Defects in protein excessive Extensive damage synthesis, and DNA injury to plasma membranes damage

Swelling of lysosomes

1. Cellular swelling1. Cellular swelling

• Caused by an accumulation of water due to

the failure of energy driven ion pumps.

Breakdown of cell membrane integrity and

accumulation of cellular electrolytes may

also occur.

• Cellular swelling is considered to be a

reversible change.

Manifestation of Cellular Manifestation of Cellular injuryinjury

2. Cellular accumulations2. Cellular accumulations

• In addition to water, injured cells can accumulate a number of different substances as metabolism and transport processes begin to fail.

• Substances that can be accumulated in injured cells may include fats, proteins, glycogen, calcium, uric acid and certain pigments such as melanin.

• These accumulations are generally reversible but can indicate a greater degree of cellular injury. Accumulation of these substances can be so marked that enlargement of a tissue or organ may occur (for example, fatty accumulation in an injured liver).

Manifestation of Cellular Manifestation of Cellular injuryinjury

Cell death falls into two main categories:

Apoptosis: Apoptosis:

controlled, “pre-programmed” cell death

Necrotic cell death: Necrotic cell death:

unregulated, enzymatic digestion of a cell

and its components.

Cell deathCell death

A controlled, “pre-programmed” cell death that

occurs with aging and normal wear and tear of the cell.

آپوپتxوز ممکن اسxت یxک مکانیسxم بxرای از بین بxردن فرسxوده و یxا سxلول

(ویxروس ویروسxی هxای عفxونت از بxرخی ژنxتیکی. دیxده آسxیب هxای

ابشxتاین بxار، بxه عنxوان مثxال) ممکن اسxت آپوپتxوز در سxلول هxای آلxوده

بxه آلxوده و میزبxان سxلول شxدن کشxته نتیجxه در نماییxد، فعxال را

It has been theorized that cancer may arise as.ویروس

a failure of normal apoptosis in damaged or mutated

cells.

Cell deathCell death 1) ApoptosisApoptosis

Cell deathCell death Occurs as a result of irreversible cellular injury.

Involves the unregulated, enzymatic digestion (“autolysis”) of a

cell and its components.

Different types of tissues tend to undergo different types of

necrosis.

Three main types of necrosis have been identified:

Liquefaction necrosis

Caseous necrosis

Coagulative necrosis

2) NecrosisNecrosis

Cell deathCell deathMain types of necrosis have been identified:

Liquefaction necrosis

Digestive enzymes released by necrotic cells soften

and liquefy dead tissue.

Occurs in tissues, such as the brain, that are rich in

hydrolytic enzymes.

2) NecrosisNecrosis

Cell deathCell death

Caseous necrosisنکروز پنیری

Occurs in conditions

like tuberculosis

where there is

prolonged inflammation

and immune activity.

2) NecrosisNecrosis

Cell deathCell death

Coagulative necrosis

Often occurs when cell death results from

ischemia and hypoxia. The acidosis denatures

cellular proteins and hydrolytic enzymes.

Seen with myocardial infarction, for example.

2) NecrosisNecrosis

Gangrene

. عنوان به است ممکن قانقاریا است نکروز تحت بافت از وسیعی منطقه که

گردد می بندی طبقه مرطوب گانگرن یا و خشک گانگرن

Effects of necrosis

Loss of function of dead area (kidney, brain). Necrotic area can become a focus for infection. May evoke certain systematic changes (inflammation, fever).

Necrotic tissue often leak its constituent enzyme in to the blood stream (CPK,ESR, AST).

Wound Care

27

Wound Repair

The process of wound repair proceeds in three sequential phases:

inflammation,

proliferation

remodeling.

28

Inflammation

Inflammation, the physiologic defense immediately after tissue injury, lasts approximately 2 to 5 days. It’s purposes are to

limit the local damage, remove injured cells and debris, and prepare the wound for healing.

Inflammation progresses through several stages

29

30

blood vessels constrict to control blood loss and confine the damage

. Shortly after, the blood vessels dilate to deliver platelets that form a loose clot.

The membranes of the damaged cells become more permeable, causing release of plasma and chemical substances that transmit a sensation of discomfort.

The local response produces the characteristic signs and symptoms of inflammation: swelling, redness, warmth, pain , and decreased function.

31

A second wave of defense follows the local

changes when leukocytes and

macrophages (types of white blood cells)

migrate to the site of injury, and the body

produces more and more white blood cells

to take their place.

32

Proliferation

Proliferation (period during which new cells fill and

seal a wound) occurs from 2 days to 3 weeks after the

inflammatory phase. It is characterized by the

appearance of granulation tissue (combination of

new blood vessels, fibroblasts, and epithelial cells),

which is bright pink to red because of the extensive

projections of capillaries in the area.

33

Granulation tissue grows from the wound margin toward

the center. It is fragile and easily disrupted by physical or

chemical means. As more and more fibroblasts produce

collagen (a tough and inelastic protein substance), the

adhesive strength of the wound increases.

34

Remodeling

Remodeling (period during which the wound

undergoes changes and maturation) follows the

proliferative phase and may last 6 months to 2 years.

During this time, the wound contracts, and the scar

shrinks.

35

1. Nutrition

2. Metabolic status

3. Circulatory status

4. Hormones

Systemic factors influencing

wound healing

1. Infection

2. Mechanical factors

3. Foreign bodies

4. Size, location

and types of wound

Local factors influencing

wound healing

Tissue repairTissue repair

1. Malnutrition

2. Poor blood flow and hypoxia

3. Impaired immune response (immunosuppressive drugs, diseases affecting immune function such as HIV and diabetes)

4. Infection of wound

5. Foreign particles in the wound

6. Old age (decreased immune activity, poor circulation, poor nutrition)

Factors That Impair Wound Healing:

Wound Healing

Several factors affect wound healing:

Type of wound injury

Expanse or depth of wound

Quality of circulation

Amount of wound debris

Presence of infection

Status of the client's health

38

Wound Healing Complications

Factors that may interfere include compromised circulation;

infection; purulent, bloody, or serous fluid accumulation that

prevent skin and tissue approximation, and drugs like

corticosteroids, and obesity.

39

The nurse assesses the wound to determine whether it is intact or shows evidence of unusual swelling, redness, warmth, drainage, and increasing discomfort.

Two potential surgical wound complications include dehiscence (separation of wound edges) and evisceration (wound separation with protrusion of organs) (Fig. 28-4).

40

41

Figure (28-4 • (A) Wound dehiscence (B) Wound evisceration).

Wound Management

Wound management involves changing dressings, caring for drains, removing sutures or staples when directed by the surgeon, applying bandages and binders, and administering irrigations.

42

Dressings A dressing purposes:

Keeping the wound clean Absorbing drainage Controlling bleeding Protecting the wound from further injury Holding medication in place Maintaining a moist environment

The most common wound coverings are gauze, transparent, and hydrocolloid dressings.

43

Gauze Dressings

Gauze dressings are made of woven cloth fibers. Their highly absorbent nature makes them ideal for covering fresh wounds that are likely to bleed or wounds that exude drainage.

Unfortunately, gauze dressings obscure the wound and interfere with wound assessment.

44

Gauze dressings usually are secured with tape. If gauze dressings need frequent changing, Montgomery straps (strips of tape with eyelets) may be used (Fig. 28-5).

45

46

Figure 28-5 • (

A) The adhesive outer edge of Montgomery straps are applied to either side of a wound.

B) The inner edges of Montgomery straps are tied to hold a dressing over a wound. They prevent skin breakdown and wound disruption from repeated tape removal when checking or changing a dressing.

Transparent Dressings

Transparent dressings are clear wound coverings. One of their chief advantages is that they allow the nurse to assess a wound without removing the dressing (Fig. 28-6).

47

48

Figure 28-6 • Transparent dressing.

Hydrocolloid Dressings

Hydrocolloid dressings are self-adhesive, opaque �و�ن) �م�د� ( الل ْك

� air- and water-occlusive wound ,َأcoverings (Fig. 28-7). They keep wounds moist. Moist wounds heal more quickly because new cells grow more rapidly in a wet environment. If the hydrocolloid dressing remains intact, it can be left in place for up to 1 week.

49

50Figure 28-7 • A hydrocolloid dressing absorbs drainage into its matrix.

Dressing Changes

Nurses change dressings when a wound requires assessment or care and when the dressing becomes loose or saturated with drainage.

51

Drains

Drains are tubes that provide a means for removing blood and drainage from a wound. They promote wound healing by removing fluid and cellular debris

52

Open Drains Open drains are flat, flexible tubes that provide a pathway for

drainage toward the dressing. Draining occurs passively by gravity and capillary action. Sometimes a safety pin or long clip is attached to the drain as it extends from the wound.

As the drainage decreases, the physician may instruct the nurse to shorten the drain, (Fig. 28-8).

53

54

Figure 28-8 • An open drain is pulled from the wound, and the excess portion is cut. A drain sponge is placed around the drain, and the wound is covered with a gauze dressing.

Closed Drains

Closed drains are tubes that terminate in a receptacle. Some examples of closed drainage systems are a Hemovac.

Closed drains are more efficient than open drains because they pull fluid by creating a vacuum or negative pressure.

55

Sutures and Staples

Sutures, knotted ties that hold an incision together, generally are constructed from silk or synthetic materials such as nylon.

Staples (wide metal clips) perform a similar function. Staples do not encircle a wound like sutures; instead, they form a bridge that holds the two wound margins together.

56

Sutures and staples are left in place until the wound has healed sufficiently to prevent reopening. Depending on the location of the incision, this may be a few days to as long as 2 weeks.

57

58

Figure 28-10 • (A) Technique for suture removal. (B) Technique for staple removal.

Bandages and Binders

A bandage is a strip or roll of cloth wrapped around a body part. One example is Crib bandage.

A binder is a type of bandage generally applied to a particular body part such as the abdomen or breast.

59

Débridement

Some wounds require débridement (removal of dead tissue) to promote healing. The four methods for débriding a wound are sharp, enzymatic, autolytic, and mechanical.

60

Sharp Débridement

Sharp débridement is the removal of necrotic tissue (nonliving tissue) from the healthy areas of a wound with sterile scissors, forceps, or other instruments.

61

Enzymatic Débridement

Enzymatic débridement involves the use of topically applied chemical substances that break down and liquefy wound debris.

This form of débridement is appropriate for uninfected wounds or for clients who cannot tolerate sharp débridement.

62

Wound Irrigation

Wound irrigation generally is carried out just before applying a new dressing. This technique is best used when granulation tissue has formed. Surface debris should be removed gently without disturbing the healthy proliferating cells.

63

Heat and Cold Applications

Heat and cold have various therapeutic uses (Box 28-1).

The terms hot and cold are subject to wide interpretation Table 28-2

64

65

66

Therapeutic Baths

Therapeutic baths (those performed for other than hygiene purposes) help to reduce a high fever or apply medicated substances to the skin to treat skin disorders or discomfort.

67

The most common type of therapeutic bath is a sitz bath (soak of the perianal area). Sitz baths reduce swelling and inflammation and promote healing of wounds after a hemorrhoidectomy (surgical removal of engorged veins inside and outside the anal sphincter) or an episiotomy (incision that facilitates vaginal birth).

68

Pressure Ulcers

A pressure ulcer is a wound caused by prolonged capillary compression that is sufficient to impair circulation to the skin and underlying tissue. The primary goal in managing pressure ulcers is prevention. Once a pressure ulcer forms, however, the nurse implements measures to reduce its size and to restore skin and tissue integrity

69

Pressure ulcers or sores, also referred to as decubitus ulcers, most often appear over bony prominences of the sacrum, hips, and heels. They also can develop in other locations such as the elbows, shoulder blades, back of the head, and places where pressure is unrelieved because of infrequent movement (Fig. 28-17).

70

71

Figure 28-17 • Locations where pressure ulcers commonly form. (A) Supine position. (B) Side-lying position. (C) Sitting position.

The tissue in these areas is particularly vulnerable because body fat, which acts as a pressure-absorbing cushion, is minimal. Consequently, the tissue is compressed between the bony mass and a rigid surface such as a chair seat or bed mattress. If the compression on local capillaries continues without intermittent relief, the cells die from lack of oxygen and nutrition.

72

Stages of Pressure Ulcers

Pressure ulcers are grouped into four stages according to the extent of tissue injury (Fig. 28-18).

73

74

Figure 28-18 • Pressure sore stages. (A) Stage I. (B) Stage II. (C) Stage III. (D) Stage IV.

Stage I is characterized by intact but reddened skin. The hallmark of cellular damage is skin that remains red and fails to resume its normal color when pressure is relieved.

A stage II pressure ulcer is red and accompanied by blistering or a skin tear (shallow break in the skin). Impairment of the skin may lead to colonization and infection of the wound.

75

A stage III pressure ulcer has a shallow skin crater that extends to the subcutaneous tissue. It may be accompanied by serous drainage (leaking plasma) or purulent drainage (white or greenish fluid) caused by a wound infection. The area is relatively painless despite the severity of the ulcer.

Stage IV pressure ulcers are life threatening. The tissue is deeply ulcerated, exposing muscle and bone (Fig. 28-19). The dead or infected tissue may produce a foul odor. The infection easily spreads throughout the body, causing sepsis (potentially fatal systemic infection).

76

77

Figure 28-19 • Example of stage IV pressure sore.

Prevention of Pressure Ulcers

The first step in prevention is to identify clients with risk factors for pressure ulcers (Box 28-2). The second step is to implement measures that reduce conditions under which pressure ulcers are likely to form. See Nursing Guidelines 28-2.

78

79

80

Nursing Implications

Acute Pain

Impaired Skin Integrity

Ineffective Tissue Perfusion

Impaired Tissue Integrity

Risk for Infection

81