Shock, Immunity, Hypersensitivy, -Nursing notes

Shock

• the life-threatening clinical syndrome of cardiovascular collapse
• characterized by hypotension and hypoperfusion
• An acute reduction of effective circulating blood volume (hypotension)
• Inadequate perfusion of cells and tissues (hypoperfusion)
• If uncompensatedàlead to impaired cellular metabolism and death

Shock Definition

• clinical state of circulatory collapse resulting in hypo-perfusion of tissues with subsequent impaired tissue oxygenation

Types of Shock- 5 types

Hypovolemic Shock

• Due to acute reduction in circulating blood volume or inadequate circulatory blood volume
• Causes
• severe hemorrhage (loss of red cell mass and plasma) or
• massive loss of fluid
• dehydration

Pathophysiology of Hypovolemic Shock

• Severity à clinical features
• The severity of clinical features depends upon the degree of blood volume
• Less than 1000 ml: Compensated
• 1000-1500 ml: Mild
• 1500-2000 ml: Moderate
• Greater than 2000 ml: Severe

Hypovolemic Shock Clinical Features

• increased heart rate (tachycardia),
• hypotension,
• low urinary output,
• altered mental state (agitated to confused to lethargic)
• Restlessness
• Sweating and cold
• Rapid shallow breathing

Cardiogenic shock

• No actual reduction of blood volume
• Caused due to Heart disease like severe left ventricular dysfunction such as myocardial damage
• Acute circulatory failure Due to decreased cardiac output

Septic/Toxaemic Shock-septicimia

• Caused by systemic microbial or bacterial infection in a whole system
• Two types of shock
• Endotoxic shock or Gram negative septicemia
• Exotoxic shock or gram positive septicimia

Neurogenic Shock

• Associated with accident or spinal cord injury, severe trauma
• Results from causes of interruption of sympathetic vasomotor supply
• Neurogenic Shock  pathophysiology

Anaphylactic Shock

• It is hypersensitivity reactions
• It is initiated by generalized by IgE mediated hypersensitivity reaction leading to systemic vasodilatation and increased vascular permeability
• Pathophysiology of Anaphylytic Shock
• 3 Stages of shock
• Progressive disorder that leads to death if uncorrected
• Compensated  Shock/ Non-progressive/ Initial/ Reversible
• If good treatment recovery and becomes normal
• Compensatory mechanism activatedà perfusion of vital organs maintained
• Activation of various neuro-hormonal mechanisms
•  widespread vasoconstriction and
•  fluid conservation by the kidney
• The purpose is to maintain adequate  cerebral and coronary blood supply by redistribution of blood so that the vital organs (brain and heart) are adequately perfused and oxygenated
• Widespread vasoconstriction
• Fluid conservation by the kidney
• To compensate for the actual loss of blood volume in hypovolaemic shock, the following factors may assist in restoring the blood volume and improving venous return to the heart
• Release of aldosterone from the hypoxic kidney by activation of the renin-angiotensin-aldosterone mechanism
• Release of ADH due to decreased effective circulating blood volume
• Shifting of tissue fluids into plasma due to lowered capillary hydrostatic pressure (hypotension)

Stimulation of adrenal medulla

• In response to low cardiac output, adrenal medulla is stimulated to release excess of catecholamines (epinephrine and non-epinephrine)
• This increases heart rate as well as increase cardiac output

Progressive decompensated shock

When the patient suffers from some other stress or risk factors (e.g pre-existing cardiovascular and lung diseases) besides the persistence of the shock there is a progressive deterioration

• It worsens pulmonary perfusion (pulmonary hypoperfusion) and increase vascular permeability resulting in tachyponea and ARDS
• Impaired tissue perfusion causes switch from aerobic to anaerobic glycolysis resulting in metabolic lactic acidosis
• Lactic acidosis lowers the tissue pH which cause vasomotor response ineffective. This results in vasodilatation and peripheral pooling of blood
• Clinically, patient develops confusion and worsening of renal function

Irreversible decompensated shock

• When the shock is severe that in spite of compensatory mechanisms and despite therapy and control of etiology agent (shock) and no recovery takes place

Immunity

• Types of Immunity
• Natural or innate immunity

Non-specific Immnity

• Considered as the first line of defense without antigenic specificity

Specific  immunity or adaptive immunity

• Characterized by antigenic specificity

Immune deficiency disorders

• Deficiencies of host defense systems result in an immunologic imbalance that can lead to a susceptibility to infection, an autoimmune disease, or a predisposition to malignancies
• Characterized by deficient cellular and/or humoral immune functions
• Includes
• Primary immune deficiency disorder
• Secondary immune deficiency disorder

Primary Immune deficiency disorder

• -Causes in immune system component
• a. According of component
• i) Complements
• ii) Phagocytic
• iii) B cells (Humoral)
• iv) T Cells (cellular)

• b. According to the etiology
• i) Congenital (X-linked disease)
• ii) Acquired (AIDS)
• iii) Embryogenesis (Digoerge syndrome)
• iv) Idiopathic

Secondary immune deficiency disorder

• -Non Immunogenic causes
• Prematurity
• Mal nutrition
• Malignancy
• Injury, Burns, Splenectomy
• Drugs

Hypersensitivity reactions

• Defined as the state of exaggerated immune response to an antigen
• Characterized by hyperfunction of the immune system and cover the various mechanisms of immunologic tissue injury

Types of hypersensitivity reactions

Type I hypersensitivity reactions

• Known as Anaphylactic reaction
• Defined as a state of rapidly developing or anaphylactic type of immune response to an antigen to which the individual is previously sensitized
• Reaction occurs within 15-30 minutes of exposure to antigen
• IgE mediated reactions
• Associated with allergens such as bee stings, peanuts

Type II hypersensitivity reactions

• Known as cytotoxic reaction
• Defined as reactions by humoral antibodies that attack cell surface antigens on the specific cells and tissues and cause lysis of target cells
• Reaction occurs within hours to days of exposure to antigen
• IgG or IgM mediated reactions
• Examples- autoimmune haemolytic anaemia, transfusions reaction, myasthenia gravis

Type III hypersensitivity reactions

• Known as Immune Complex Mediated Reaction
• Result from deposition of antigen-antibody complexes on tissues which is followed by activation of the complement system and inflammatory reaction, resulting in cell injury
• Reaction occurs within 1-3 weeks of exposure to antigen
• Immune complex mediated reactions
• Examples- SLE, Immune complex glomerulonephritis
• Type IV Hypersensitivity Reactions
• Known as delayed hypersensitivity reaction
• Defined as a tissue injury by cell mediated immune response without formation of antibodies but a slow and prolonged response of specifically sensitized T lymphocyctes
• Reaction occurs after 24 hours to days and weeks of exposure to antigen
• T cell mediated reactions
• Examples- tuberculin reaction, leprosy (reaction against mycobacterial infection), transplant rejection

Auto immune disorders

• Normally lymphocytes recognize body’s own proteins, so antibodies are not developed against them
• However, sometimes body suffer from antibody or cell mediated attack against its own, causing damage of normal cells and their function leading to autoimmune disease
• example- rheumatic heart disease
• Defined as a state in which the body’s immune system fails to distinguish between ‘self’ and ‘non self’ and reacts by formation of autoantibodies against one’s own tissue antigens
• There is loss of tolerance to one’s own tissues (autoimmunity)
• Caused by immunological factors, genetic factors and microbial factors

Types of autoimmune diseases

Organ specific diseases

• Autoantibodies formed react specifically against an organ or target tissue component and cause its chronic inflammatory destruction
• Example-thyroid, pancreatic islets of langerhans

Organ non-specific (systemic) diseases

• Autoantibodies formed which reacts with antigens in many tissues and thus causes systemic lesions
• Example- Systemic lupus erythematous, Rheumatoid arthritis, Sjogren’s syndrome

Genetic disorders

• Genetic disorder is due to inherited defects in chromosomes

Classification of genetic disorders

• Single gene defect
• Multifactorial disorder
• Cytogenetic (Karyotypic) disorder or chromosomal abnormalities

Single gene disorders

• Know as mendelian disorders
• These disorders are due to defect in a single gene or result of mutation of a single gene
• Example- sickle cell anemia, Beta thalassaemia

Multifactorial genetic/inheritance disorders

• Those disorders which result from the combined effect of genetic composition and environmental influences
• Example- congenital heart disease, diabetes mellitus, cleft palate, congenital heart disease

• Cytogenetic or chromosomal disorders
• This disorder may be due to aberrations in the number of structure of chromosomes
• A chromosomes number which is an exact multiple of the haploid number and exceeds the diploid number is called polypoidy and which is not an exact multiple is called aneuploidy
• Examples Down’s syndrome (Trisomy 21), Edward’s syndrome (Trisomy 18)