physiology of life and death Flashcards
maintenance of life
- body systems are interrelated and interdependent
- every cell and every organ work together to:
- sustain cellular energy production
- maintain vital metabolic processes
energy
- energy powers all body functions
- energy sustains cellular and organ functions
- cells make energy from oxygen and glucose
- energy is stored in the form of ATP (adenosine triphosphate molecules)
- without energy, cellular functions cease
- the goal is to help ensure that the patients body maintains energy production
ABC
- airway- must be patent
- breathing (lungs)
- circulation
breathing
- adequate oxygen must reach alveoli
- cross alveolar/capillary wall and enter the circulation
- CO2 is removed
circulation
- distributes RBCs
- ensures adequate number of RBCs
- transports oxygen to every cell in every organ
airway
-an open airway is essential to deliver air (oxygen) to the alveoli
normal air movement
- inhalation results from negative intrathoracic pressure as the chest expands (diaphragm contracts)
- air fills the alveoli`
- exhalation results from increase intrathoracic pressure as the chest relaxes (diaphragm relaxes)
- forces air out of the alveoli
when air reaches the alveoli
-oxygen crosses the alveolar capillary membrane
oxygen
- enters the RBCs
- attaches to hemoglobin for transport
CO2 in the plasma and cells
- a by product of aerobic metabolism and energy production
- crosses the alveolar capillary membrane into the alveoli
- is removed during respiration
circulation
- oxygen enriched RBCs are pumped through the blood vessels of the body to deliver oxygen to target organs
- need a certain amount of blood and pumping heart for this
- oxygen is then off loaded from the RBCs to fuel the metabolic processes of the cell
- CO2 is transferred from the cells to the plasma for elimination via the lungs
aerobic metabolism
- most efficient methods of energy production
- uses oxygen and glucose to produce energy via chemical reactions known
- produces large amounts of energy
- waste products:
- carbon dioxide
- water
aerobic metabolism is dependent on
- adequate and continuous supply of oxygen
- patent airway
- functioning lungs (pulmonary system)
- functional heart- pump blood to the cells
- intact vascular system
- adequate supply of RBCs
- carry and transport oxygen
- remove waste
anaerobic metabolism
- an injury that affects any of these three components of the oxygen delivery system will affect energy production
- anaerobic metabolism is a metabolic process that functions in the absence of oxygen
- metabolism WITHOUT adequate oxygen
- uses stored glucose in the form of glycogen for energy production
- capable of sustaining energy requirements only for a short time
- produces only small amounts of energy
- 19 fold decrease in energy
- increased lactic acid as a by product
shock
- inadequate energy production required to sustain life
- change from aerobic to anaerobic metabolism
- secondary to hypoperfusion
- delivery of oxygen is inadequate to meet metabolic demands
- decreased energy production
- cellular and organ death
consequences of hypoperfusion
- cellular hypoxia
- decreased ATP (energy) production
- cell dysfunction
cell dysfunction
- lactic acid buildup
- low pH
- autodigestion of cells- leads to cellular death and organ failure
- entry of sodium and water into the cell- cellular edema (swelling) worsens with overhydration
- continuation of cycle- unless oxygenated RBCs reach the capillaries
- if further loss of intravascular (blood) volume- the cycle continues
- inadequate ATP
- cells and organs do not function properly
- hypothermia- decreased heat production
acidosis
- what little ATP is being produced is used to shiver
- lactic acid production increases
coagulopathy
-as body temperature drops, blood clotting becomes impaired
triangle of death
- energy loss
- acidosis -> hypothermia -> coagulopathy
cascade of death
- anaerobic metabolism
- decreased energy production
- cellular death
- organ death
- patient death
types of shock
- shock is any condition that causes decreased cellular energy production
- hypovolemic
- distributive
- cardiogenic
hypovolemic shock
- dehydration
- hemorrhage
distributive shock
- neurogenic
- septic
- anaphylactic
- psychogenic
- dilation -> edema
cardiogenic shock
-pump failure (intrinsic vs extrinsic)
hemorrhagic shock*
- most common cause of hypoperfusion after trauma
- internal or external blood loss
- 4 classes of shock
- can affect mental status
- fluids are the treatment
- respiratory rate increases
- pulse increases
- urine decreases (kidneys arnt getting circulation)
- know the chart*
neurogenic shock
- associated with spinal cord injury
- interruption of the sympathetic nervous system resulting in vasodilation
- patient has normal blood volume but vascular container has enlarged, thus decreasing blood pressure
cardiogenic shock: extrinsic
- results from external compression of the heart
- ventricles cannot fully expand
- less blood is ejected with each contraction
- blood return to the heart is decreased
- causes from trauma include:
- pericardial tamponade- blood collecting in pericardial sac-> restricts
- tension pneumothorax- lung collapses and causes pressure restriction blood circulation
pathophysiology of shock
- shock is progressive
- changes in shock include:
- hemodynamic
- cellular (metabolic)
- microvascular
- compensatory mechanisms are short term and will fail without interventions
- heart must be an effective pump
- primed by return of blood through the vena cavae -> starlings law
stroke volume (SV)
- amount of blood ejected with each contraction
- depends on adequate return of blood
- if blood volume decreases:
- SV will decrease
- cardiac output (CO) will decrease unless the heart rate (HR) increase
- CO = SV x HR
adequate blood pressure
-required to maintain cellular perfusion
cardiac output (CO)
- one factor in maintaining blood pressure (BP)
- if CO falls:
- vasoconstriction occurs
- systemic vascular resistance (SVR) increases in an attempt to maintain BP
- BP = CO x SVR
vasocontriction
- leads to the ischemic phase of shock
- veins constrict to focus on pumping to the heart but the other places will become ischemic eventually
early microvascular changes
- precapillary and postcapillary sphincters constrict
- resulting in ischemia in the tissues
- must then produce energy anaerobically
as acidosis increases
- the precapillary sphincters relax
- the postcapillary sphincters remain constricted
- this results in stagnation of blood in the capillary bed
final microvascular changes
- the post capillary sphincters relax
- results in wash out
- releases microemboli
- aggravates acidosis
- causes infarction of organs by microemboli
signs associated with types of shock: hypovolemic**
- cool clammy skin (bad circulation)
- pale, cyanotic
- BP drops
- consciousness is altered
- capillary refill is slow
signs associated with types of shock: neurogenic
- warm, dry skin temp
- pink skin color
- BP drops
- lucid
- normal capillary refill
- (different from cardiogenic and hypovolemic)
signs associated with types of shock: cardiogenic
- cool, clammy skin temp
- pale, cyanotic skin color
- BP drops
- consciousness is altered
- capillary refill is slowed
organ system failure due to shock
- if not recognized and promptly corrected, shock will lead to organ dysfunction
- first oxygen sensitive organs
- then in other less oxygen sensitive organs
- this cascading effect will lead to multi organ dysfunction syndrome and patient death
- failure of one major organ system
- mortality rate of approx 40%
- as additional organ system fail, mortality approaches 100%
organ sensitivity to hypoxia
- extremely sensitive- brain, heart, lungs
- moderately sensitive- kidneys, liver, gastrointestinal tract
- least sensitive- muscle, bone, skin
acute renal failure
- may result if oxygen delivery is impaired for more than 45-60 mins
- will result in:
- decreased renal output
- reduced clearing of toxic products
acute respiratory distress syndrome (ARDS)
- Results from:
- Damage to the alveolar cells
- Hyper-resuscitation (fluid overload)
- Results in:
- Leakage of fluid into the interstitial spaces and alveoli
hemotologic failure
-Impaired clotting cascade
-May result from:
-Hypothermia
-Dilution of clotting factors from fluid
administration
-Depletion of clotting factors
hepatic failure
-results from prolonged shock
overwhelming infection
-results from decreased function of the immune system due to ischemia and loss of energy production
summary
-Cellular function depends on adequate energy
production
-Adequate energy production depends on a continuous
and adequate supply of oxygen
-A continuous and adequate supply of
oxygen depends on:
• Patent airway
• Functioning lungs
• Functioning heart
•Intact circulation
-Interruption of the oxygen supply for any reason
will lead to anaerobic metabolism
-Anaerobic metabolism provides insufficient energy
to sustain cellular function for any length of time
-This leads to cellular dysfunction and cell death,
organ dysfunction and organ death, and ultimately
patient death
-Knowledge, understanding, and early recognition of impaired energy production
resulting from airway compromise, pulmonary
injury, and impaired circulation are key to early
recognition of shock.
-Prompt intervention by prehospital care providers to correct these conditions can
prevent the cascade of cellular dysfunction that
leads to organ death.
-This will improve the survival rate for victims of
traumatic injury.
