Bledsoe et al., Paramedic Care: Principles & Practice, Volume 1: Introduction to Advanced Prehospital Care, 3rd Ed. © 2009 by Pearson Education, Inc. Upper.

Bledsoe et al., Paramedic Care: Principles & Practice, Volume 1: Introduction to Advanced Prehospital Care, 3rd Ed.© 2009 by Pearson Education, Inc. Upper Saddle River, NJ

Paramedic Care:Principles & Practice

Volume 1Introduction to Advanced

Prehospital Care


Chapter 8 General Principles of

Physiology and Pathophysiology


Chapter 8, Part 2Disease—Causes and

Pathophysiology


Part 2 Topics

Genetic and Other Causes of Disease

Hypoperfusion

Types of Shock





Many diseases result from genetic causes.

Many diseases result from a combination of genetic and environmental factors as well as age and gender.


Genetics, Environment, Lifestyle, Age, and Gender

Inherited traits are determined by molecules of deoxyribonucleic acid, or DNA. – Form genes that reside on chromosomes– Somatic cells (all the cells except the sex cells)

contain 46 chromosomes– Sex cells contain 23 chromosomes

Offspring receive 23 from mother and 23 from father


Genetics, Environment, Lifestyle, Age, and Gender

Abnormal genes or chromosomes may cause a congenital disease or a propensity toward acquiring a disease.Some diseases are thought to be purely genetic. Other diseases are caused by a combination of genetic and environmental factors.


Disease Effects on Individuals

Related to Host, Agent, and Environment– Host

Genetic predisposition, gender, and ethnic origin are determinants related to the host.

– AgentBacterium, toxin, gunshot, or other pathophysiological process

– EnvironmentLocal climate, socioeconomic or demographic features, culture, religion, and associated factors


Disease Effects on Populations

Epidemiologists generally report disease data with three basic measures: incidence, prevalence, and mortality.

Morbidity is reported as incidence and prevalence.– Incidence is occurrence of disease– Prevalence is the proportion of total population

effected

Mortality is the occurrence of death.


Family History and Associated Risk Factors

Immunologic disorders

Cancer

Endocrine disorders

Hematologic disorders

Cardiovascular disorders

Renal disorders

Rheumatic disorders

Gastrointestinal disorders

Psychiatric disorders


Immunologic Disorders

A number of immunologic disorders are more prevalent among those with a family history of the disorder.– Rheumatic fever, allergies, and asthma


Cancer

Some types of cancer tend to cluster in families and seem to have a combination of genetic and environmental causes.– Breast cancer– Colorectal cancer– Lung cancer


Endocrine Disorders

The most common endocrine disorder is diabetes mellitus.

Both Type I and Type II diabetes can be family related.

Causes of diabetes are complex and still not well understood.


Hematological Disorders

There are many causes of hereditary hematological disorders such as gene alteration and histocompatibility (tissue interaction) dysfunctions.– Hemophilia– Hemochromatosis


Cardiovascular Disorders

The cardiovascular system can be greatly affected by genetic disorders.– Elongation of the QT interval– Mitral valve prolapse– Coronary artery disease– Hypertension– Cardiomyopathy


Renal Disorders

Caused by a variety of factors, primarily hypertension

May eventually require a patient to receive dialysis treatment several times a week – Problems with vascular access devices– Localized infection and sepsis– Electrolyte imbalances


Rheumatic Disorders

Gout is a disorder both genetic and environmental characterized by the deposit of crystals in the joints, most commonly the great toe.

The crystals form as a result of abnormally high levels of uric acid in the blood.


Gastrointestinal Disorders

Lactose intolerance

Crohn’s disease

Peptic ulcers

Cholecystitis

Obesity


Neuromuscular Disorders

Diseases of the nervous and muscular systems include:– Huntington’s disease– Multiple sclerosis– Alzheimer’s disease


Psychiatric Disorders

Genetic and biological causes of these disorders are being studied and increasingly understood.– Schizophrenia– Manic-depressive illness (bipolar disorder)


Hypoperfusion

Progressive cycle of pathophysiological events– Fatal if not corrected

Although causes differ, all forms of shock have the same underlying pathophysiology at the cellular and tissue levels.


Cellular Death

Tissue Death

Organ Death

Organ System Death

Organism Death

Progression of Shock


The Physiology of Perfusion

Body cells require a constant supply of oxygen and other essential nutrients. – Accomplished by the passage of blood through

the capillaries.

The constant and necessary passage of blood through the body’s tissues is called perfusion.


Components of the Circulatory System

The pump (heart)

The fluid (blood)

The container (blood vessels)


The Pump

The heart is the pump of the cardiovascular system.– Receives blood from the venous system, pumps

it to the lungs for oxygenation, and then pumps it to the peripheral tissues.

The amount of blood ejected by the heart in one contraction is referred to as the stroke volume.


Stroke Volume

Factors affecting stroke volume:– Preload

Amount of blood delivered to the heart during diastole

– Cardiac contractile forceThe strength of contraction of the heart

– AfterloadThe resistance against which the ventricle must contract


Cardiac Output

Cardiac output is the amount of blood pumped by the heart in one minute.

An increase in stroke volume or an increase in heart rate can increase cardiac output.

SV x HR = CO


Blood Pressure

Peripheral vascular resistance is the pressure against which the heart must pump.

Increasing cardiac output or peripheral vascular resistance will increase blood pressure.

CO x PVR = BP


Blood Pressure

Peripheral Vascular Resistance– Blood pressure maintained by compensatory

mechanisms and negative feedback loops– Baroreceptors

Increased pressure causes a decreased heart rate, preload, and peripheral vascular resistanceDecreased pressure stimulates vasoconstriction and adrenal hormone release


The Fluid

Blood is thicker and more adhesive than water.Blood consists of plasma and the formed elements.– Red cells, white cells, platelets

Nutritional functionAn adequate amount of blood is needed for perfusion, and volume must be adequate to fill the container.


The Fluid

Natriuretic Hormone– Endocrine function of the heart– Involved in the long-term regulation of sodium

and water balance, blood volume, and arterial pressure

– Natriuretic peptides Atrial natriuretic peptide (ANP)

Released by atrial muscle cells in response to such things as atrial distension and sympathetic stimulation

Brain natriuretic peptide (BNP) Released by ventricular muscle cells in response to ventricular dilation and sympathetic stimulation


The Fluid

Natriuretic Hormone (cont.)– Counterregulatory system to the renin-

angiotensin system Decreases aldosterone release Produces natriuresis (sodium loss) and diuresis (water loss)

Decreases renin release – BNP levels are elevated in congestive heart

failure


The Container

Blood vessels – A continuous, closed, and pressurized pipeline

by which blood moves throughout the body

Autonomic regulation

Microcirculation – Comprised of the small vessels: arterioles,

capillaries, and venules– Responsive to local tissue needs


The Container

Capillaries – The precapillary sphincter opens in response to

local tissue demands such as acidosis and hypoxia.

– The postcapillary sphincter opens when blood is to be emptied into the venous system.


Blood Flow Regulation

Blood flow through the vessels is regulated by two factors: – Peripheral vascular resistance– Pressure within the system

Vessels with larger inside diameters offer less resistance.

Vessels with smaller diameters offer more resistance.



Click here to view an animation on capillary pressure.



A significant change in peripheral resistance occurs at the arterioles and precapillary sphincters. – Local tissue needs and sympathetic stimulation

Contraction of the venous side of the vascular system – Decreased capacitance and increased cardiac

preload


Oxygen Transport

Surrounding the alveoli are capillaries that are perfused by the pulmonary circulation. – Alveolar air is far richer in oxygen than blood

that enters the pulmonary capillaries. – Oxygen from the alveoli diffuses across the

alveolar-capillary membrane.


Oxygen Transport

Oxygen binds to the hemoglobin molecules of the red blood cells. – 97% of oxygen is transported reversibly bound

to hemoglobin. – 3% of oxygen is transported as a gas dissolved

in the plasma.

Oxygen-enriched blood is pumped throughout the body via systemic circulation.


Oxygen Transport

The oxygen-rich blood interfaces with the tissues in capillary beds.– Cells in tissue are oxygen-deficient.– Partial pressure of oxygen is greater in the

bloodstream than in the cells. – Oxygen will diffuse from the red blood cells

across the capillary wall.


Oxygen Transport

The movement and utilization of oxygen in the body is dependent upon the following conditions:– Adequate concentration of oxygen– Appropriate movement of oxygen across the

alveolar/capillary membrane – Adequate number of red blood cells– Proper tissue perfusion– Efficient off-loading of oxygen at the tissue level


Waste Removal

The waste products of cellular metabolism are expelled from the cells and carried away by the blood.

The majority of carbon dioxide (approximately 70%) is transported in the form of bicarbonate ion (HCO3¯).


Waste Removal

Some cellular waste products are picked up by the lymphatic system.

Waste is cleansed from the blood by the kidneys and excreted as urine.

Some cellular waste products are expelled in the feces.


Waste Removal

There is some local control of both tissue perfusion and waste removal.

Local acidosis causes nearby pre-capillary sphincters to relax.

Increases perfusion of the affected tissues – Provides increased capacity for waste

elimination


Hypoperfusion


Causes of Hypoperfusion

Inadequate pump– Decreased preload, inadequate contractile

strength, inadequate rate, or excessive afterload

Inadequate fluid– Hypovolemia

Inadequate container– Dilated container without change in fluid volume

(inadequate systemic vascular resistance)– Leak in the container


Shock at the Cellular Level

Shock is inadequate tissue perfusion.

Ultimate outcome is impairment of cellular metabolism.

Two characteristics of impaired cellular metabolism:– Impaired oxygen use – Impaired glucose use


Impaired Use of Oxygen

When cells don’t receive enough oxygen or cannot use it effectively, they change from aerobic to anaerobic metabolism.– A far less efficient means of producing energy.



Glycolysis– Stage 1

AnaerobicInefficient

– Stage 2AerobicEfficient

Hypoperfusion does not allow stage 2 glycolosis



Accumulation of lactic acid– The acidic condition of the blood reduces the

ability of hemoglobin in red blood cells to bind with and carry oxygen.

– Cellular stores of ATP are used up much faster than they can be replaced.

– Cellular death then occurs.


Impaired Use of Glucose

Factors that reduce delivery of oxygen to the cells also reduce delivery of glucose to the cells.– Also by:

Fever Cell damageThe presence of bacteria or toxinsHistamine or other substances produced by the body’s immune and inflammatory responses


Impaired Use of Glucose

Glucose that is prevented from entering the cells remains in the blood.– Certain body cells can create fuel for energy

production by converting other substances to glucose.

Glycogenolysis Lipolysis

Waste products of metabolism build up in the cells, further impairing cell function and damaging cell membranes.


Compensation and Decompensation

Usually the body is able to compensate for metabolic processes in order to maintain homeostasis through perfusion.

When the various compensatory mechanisms fail, shock develops.


Compensation Mechanisms

The fall in arterial blood pressure is a negative feedback mechanism.– Catecholamines, epinephrine, and

norepinephrine may be secreted– The renin-angiotensin system aids in

maintaining blood pressure– Secretion of anti-diuretic hormone (ADH)– Splenic discharge– Shunting


Shock Variations

Compensated shock– The early stage of shock when the body’s

compensatory mechanisms are able to maintain perfusion

Decompensated shock– Compensatory mechanisms may not be able to

restore normal function – Intervention may still be able to correct the

condition


Shock Variations

Irreversible shock– Correction is no longer possible– Cardiac depression

Myocardium has a greatly increased demand for oxygen Coronary blood flow is reduced; cardiac output falls more

– Cellular deterioration progresses to tissue deterioration, which progresses to organ failure.


Types of Shock


Types of Shock

Cardiogenic

Hypovolemic

Neurogenic

Anaphylactic

Septic


Cardiogenic Shock

The heart loses its ability to supply all body parts with blood

Usually the result of left ventricular failure secondary to acute myocardial infarction or CHF

Many patients will have normal blood volume


Cardiogenic Shock

Evaluation – Difference between cardiogenic shock and other

types of shock is the presence of pulmonary edema

Wheezes or crackles (rales) may be heard

There may be a productive cough with white or pink-tinged foamy sputum

– Cyanosis, altered mentation, and oliguria


Cardiogenic Shock

Treatment – Treat for shock

Assure an open airway, administer oxygen, assist ventilations as necessary, keep the patient warm

– Elevate the patient’s head and shoulders– Establish IV access with minimal fluid

administration– Monitor the heart rate– Dopamine or dobutamine may be administered


Hypovolemic Shock

Shock due to loss of intravascular fluid

Causes of hypovolemia– Internal or external hemorrhage– Trauma– Long-bone or open fractures– Dehydration– Plasma loss from burns– Excessive sweating– Diabetic ketoacidosis with resultant osmotic

diuresis


Hypovolemic Shock

Hypovolemic shock can also be due to internal third-space loss. – Bowel obstruction, peritonitis, pancreatitis, or

liver failure resulting in ascites


Hypovolemic Shock

Evaluation – Altered level of consciousness– Pale, cool, clammy skin– Blood pressure may be normal, then fall– Pulse may be normal then become rapid, finally

slowing and disappearing– Urination decreases– Cardiac dysrhythmias may occur


Hypovolemic Shock

Treatment – Airway management, supplemental oxygenation,

assisted ventilations (if necessary), hemorrhage control, and rapid transport

– Administer a bolus of crystalloid solution for fluid replacement

Non-trauma or no blood loss:Bolus crystalloid or colloid solutions

Trauma or blood loss:“Permissive hypotension.” – SBP of 70-85 mmHg

PASG if part of local protocol


Neurogenic Shock

Injury to brain or spinal cord causes an interruption of nerve impulses to the arteries– The arteries dilate causing relative hypovolemia– Sympathetic impulses to the adrenal glands are

lost Prevents the release of catecholamines with their compensatory effects


Neurogenic Shock

The arteries lose tone and dilate, causing a relative hypovolemia

A disproportionate amount of blood collects in the capillary bed– Reduces venous return, cardiac output, and

arterial blood pressure


Neurogenic Shock

Evaluation – Warm, dry, red skin– Low blood pressure– Slow pulse

The lack of compensatory stimulation from catecholamine release


Neurogenic Shock

Treatment – Airway control– Maintain body temperature– Immobilization of patient– Consider other possible causes of shock– IV access and medications that increase

peripheral vascular resistanceNorepinephrine (Levophed) and dopamine (Intropin)


Anaphylactic Shock

A severe immune response to a foreign substance

Signs and symptoms most often occur within a minute

The most rapid reactions are in response to injected substances:– Penicillin injections– Stings from bees, wasps, hornets


Anaphylactic Shock

Evaluation – Because immune responses can affect different

body systems, signs and symptoms vary widely.Skin:

Flushing, itching, hives, swelling, cyanosis

Respiratory system:

Breathing difficulty, sneezing, coughing, wheezing, stridor, laryngeal edema, laryngospasm

Cardiovascular systemVasodilation, increased heart rate, decreased blood pressure


Anaphylactic Shock

Evaluation – Gastrointestinal system:

Nausea, vomiting, abdominal cramping, diarrhea

– Nervous system:Altered mental status, dizziness, headache, seizures, tearing


Anaphylactic Shock

Treatment – Airway protection

May include endotracheal intubation

– Establish an IV of crystalloidsolution

– Pharmacological intervention:Epinephrine, antihistamines, corticosteroids, vasopressors, inhaled beta agonists


Septic Shock

An infection that enters the bloodstream and is carried throughout the body

Toxins released overcome the compensatory mechanisms

Can cause the dysfunction of an organ system or result in multiple organ dysfunction syndrome


Septic Shock

Evaluation – The signs and symptoms are progressive

Increased to low blood pressureHigh fever, no fever, or hypothermicSkin flushed, pale, or cyanoticDifficulty breathing and altered lung soundsAltered mental status


Septic Shock

Treatment – Airway control– IV of crystalloid solution– Dopamine to support blood pressure– Monitor heart rhythm


Multiple Organ Dysfunction Syndrome

Progressive impairment of two or more organ systems – An uncontrolled inflammatory response to a

severe illness or injury

Sepsis and septic shock are the most common causes of MODS



Stages of MODS– Primary Stage

Results directly from a specific cause

Neutrophils and macrophages as well as mast cells are thought to be “primed” by cytokines



Stages of MODS– Secondary Stage

Primed cells are activated, producing an exaggerated inflammatory response

Inflammatory response enters a self-perpetuating cycle

Triggers an exaggerated neuroendocrine response

A massive immune/inflammatory and coagulation response develops


Clinical Presentation of MODS

Usually will develop over a period of 2, 3, or more weeks

There is no specific therapy for MODS

MODS will usually be detected in the hospital– EMS may encounter patient following discharge

or during transfer


Part 2 Summary


Hypoperfusion

Types of Shock

Bledsoe et al., Paramedic Care: Principles & Practice, Volume 1: Introduction to Advanced Prehospital Care, 3rd Ed. © 2009 by Pearson Education, Inc. Upper.

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