General Principles of Pathophysiology
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Transcript General Principles of Pathophysiology
General Principles of
Pathophysiology
Energy Metabolism
Perfusion
Shock
Topics
Define shock in terms of cellular
function
Review the requirements for adequate
cellular perfusion (Fick principle)
Review the mechanisms for starling’s
law
Preload vs. afterload
Muscle contraction
Topics Continued
Discuss the mechanisms for oxygen
transport
oxyhemoglobin dissociation curve
Define the stages of shock
Describe different causes of shock
Define multiple organ dysfunction
syndrome
Shock Defined
Inadequate tissue perfusion
Anaerobic metabolism
Final Common Pathway!
Aerobic Metabolism
6 CO2
6 O2
METABOLISM
GLUCOSE
6 H2O
36 ATP
HEAT (417 kcal)
Anaerobic Metabolism
2 LACTIC ACID
GLUCOSE
METABOLISM
2 ATP
HEAT (32 kcal)
Anaerobic? So What?
Inadequate
Cellular
Oxygenation
Inadequate
Energy
Production
Metabolic
Failure
Anaerobic
Metabolism
Lactic Acid
Production
Cell Death!
Metabolic
Acidosis
Homeostasis is maintenance of
balance
Requires proper functioning systems
Cardiovascular
Respiratory
Renal
Physiology of Perfusion
Dependant on 3 components of
circulatory system
Pump
Fluid
Container
Factors Affecting The Pump
Preload
Contractile force
Frank-starling mechanism
Afterload
Muscle Anatomy
Contraction: Sliding Filaments
image from: http://www.accessexcellence.com/AB/GG/muscle_Contract.html
What Is Blood Pressure?
BP = Cardiac Output
X Systemic Vascular Resistance
CO = Stroke Volume
X Heart Rate
What Affects Blood Pressure?
ANS balance
Contractility
Preload
Starling’s law
Afterload
Autonomic Nervous System
Review…
Quiz Time! Yeah!
Jeopardy
Controls vegetative functions,exits the
CNS at high in the neck and low in the
back.
What is the
parasympathetic nervous system?
Jeopardy
The chief neurotransmitter of the
sympathetic nervous system.
What is
Norepinephrine?
Jeopardy
The ‘cutesy’ name for the
parasympathetic nervous system.
What is
‘Feed or Breed’?
Jeopardy
Two types of parasympathetic receptors.
What is nicotinic (NMJ)
and muscarinic (organs)?
Jeopardy
Two types classes of sympathetic
receptors.
What is
alpha and beta?
Jeopardy
The ‘cutesy name’ for the sympathetic
nervous system.
What is
‘fight or flight’?
Jeopardy
Stimulation of this receptor causes an
increase in peripheral vasoconstriction.
What is alpha 1?
Jeopardy
Stimulation of this receptor causes an
increase in myocardial contractility.
What is beta 1?
Jeopardy
Stimulation of this receptor causes an
increase in bronchodilation.
What is beta 2?
Jeopardy
Stimulation of this receptor causes a
decrease in the sympathetic activation.
What is alpha 2?
Jeopardy
Two types of parasympathetic receptors.
What is nicotinic (NMJ)
and muscarinic (organs).
Changes in Afterload and Preload
Peripheral
vasoconstriction…
peripheral vascular
resistance…
afterload…
blood pressure.
Changes in Afterload and Preload
Peripheral
vasodilation…
peripheral vascular
resistance…
afterload…
blood pressure.
Changes in Afterload and Preload
fluid volume…
preload…
contractility
(Starling’s Law)…
blood pressure.
cardiac output.
Changes in Afterload and Preload
fluid volume…
preload…
contractility
(Starling’s Law)…
blood pressure.
cardiac output.
Fluid
Must have adequate
amounts of
hemoglobin
Must have adequate
intravascular volume
Maintenance of Fluid Volume
Renin-Angiotensin-Aldosterone system.
Works through kidneys to regulate balance
of Na+ and water.
Renin-Angiotensin-Aldosterone
Plasma
volume
Detected by
&/Or
Kidney
(juxtaglomerular
apparatus)
[Na+]
Via ACE
(Angiotensin
Converting
Enzyme)
Releases
Renin
Converts
Angiotensin II…
Angiotensin I…
Angiotensinogen
Renin-Angiotensin-Aldosterone
vasoconstriction
PVR
Angiotensin II…
thirst
ADH
(anti-diuretic
hormone)
Adrenal
cortex
Fluid
volume
Releases
Aldosterone
BP!
Na+
reabsorption
Hemostasis
The stoppage of bleeding.
Three methods
Vascular constriction
Platelet plug formation
Coagulation
Coagulation
Formation of blood clots
Prothrombin activator
Prothrombin thrombin
Fibrinogen fibrin
Clot retraction
Fibrinolysis
Plasminogen
Tissue plasminogen activator (tPA)
Plasmin
Disseminated Intravascular
Coagulation
“A systemic thrombohemorrhagic disorder
… with evidence of:
1) Procoagulant activation
2) Fibrinolytic activation
3) Inhibitor consumption
4) End-organ failure”
Bick, R.L. Seminars in Thrombosis and Hemostasis 1996
Pathophysiology of DIC
Uncontrolled acceleration of clotting
cascade
Small vessel occlusion
Organ necrosis
Depletion of clotting factors
Activation of fibrinolysis
Ultimately severe systematic
hemorrhage
Container
Vasculature is continuous, closed and
pressurized system
Microcirculation responds to local tissue
needs
Blood flow dependent on PVR
Fick Principle
Effective movement and utilization of O2
dependent on:
Adequate fio2
Appropriate O2 diffusion into bloodstream
Adequate number of RBCs
Proper tissue perfusion
Efficient hemoglobin ‘loading’
Fick Principle
Perfusion = Arterial O2 Content Venous O2 Content
Affected by:
Hemoglobin levels
circulation of RBCs
distance between alveoli and capillaries
pH and temperature
Onloading Oxygen in Lungs
oxyhemeglobin
pH 7.45
Remember:
CO2 [H+]
pH 7.4
• pH shifts curve to left
• ‘onloading’ in lungs
deoxyhemeglobin
Pressure
Offloading Oxygen in Tissues
pH 7.4
Remember:
CO2 [H+]
oxyhemeglobin
pH 7.35
•pH shifts curve to right
• ‘offloading’ to tissues
deoxyhemeglobin
Pressure
Causes of Inadequate Perfusion
Inadequate pump
Inadequate preload
Poor contractility
Excessive afterload
Inadequate heart rate
Inadequate fluid volume
Hypovolemia
Inadequate container
Excessive dilation
Inadequate systematic vascular resistance
Responses to Shock
Normal compensation includes:
Progressive vasoconstriction
Increased blood flow to major organs
Increased cardiac output
Increased respiratory rate and volume
Decreased urine output
Cellular Response to Shock
O2
use
Anaerobic
metabolism
ATP
synthesis
Na+ Pump
Function
Tissue
perfusion
Stimulation of
clotting cascade &
inflammatory
response
Intracellular Na+
& water
Impaired cellular
metabolism
Impaired
glucose
usage
Cellular edema
Vascular volume
Stages of Shock
Compensated
Uncompensated
Irreversible
Compensated Shock
Defense mechanisms are successful in
maintaining perfusion
Presentation
Tachycardia
Decreased skin perfusion
Altered mental status
Uncompenstated Shock
Defense mechanisms begin to fail
Presentation
Hypotension
Prolonged Cap refill
Marked increase in heart rate
Rapid, thready pulse
Agitation, restlessness, confusion
Irreversible Shock
Complete failure of compensatory
mechanisms
Death even in presence of resuscitation
Types of Shock
Hypovolemic
Cardiogenic
Neurogenic
Anaphylactic
Septic
Hypovolemic Shock
“Fluid failure”
Decreased intravascular volume
Causes?
“Third spacing”
Cardiogenic Shock
R.A.S.
Activation
Volume/
Preload
Impaired
myocardial function
Catecholamine
Release
CO
Myocardial
O2 demand
Dyspnea
SVR
O2
supply
Peripheral
& pulmonary
edema
Neurogenic Shock
Sympathetic Tone
Or
Parasympathetic Tone
Tissue
perfusion
Cardiac Output
Vascular Tone
Massive Vasodilation
SVR & Preload
Anaphylactic Shock
“Container failure”
Massive & systemic allergic reaction
Large release of histamine
Increases membrane permeability &
vasodilation
Septic Shock
“Container failure”
Systemic infection
Multiple Organ Dysfunction
System
Progressive dysfunction of two or more
organ systems
Caused by uncontrolled inflammatory
response to injury or illness
Typically sepsis
References
New York Presbyterian hospital hypertension center:
Http://pc101186.Med.Cornell.edu/htchome/htbk/Htbkindex.ht
m
Biographics Gallery:
http://www.accessexcellence.com/AB/GG/#AnchorBuilding-11481
RAS (Renin-Angiotensin-Aldosterone System):
http://www.science.mcmaster.ca/Biology/4S03/RAS.HTM
A graduate student’s hypertension page:
http://www.teachingbiomed.man.ac.uk/student_projects/2000/mnpm6ven/default.h
tm