week 3 shock Flashcards
oxygenation
diffusion of oxygen from lungs into blood
Ventilation:
gas exchange in the respiratory system (i.e., mechanics of air moving in and out of the lungs)
2 types of ventilation:
Pulmonary ventilation: total exchange of gases between atmosphere & lungs
Alveolar ventilation: exchange of gases within gas exchange portion of lung
Perfusion:
-adequate blood circulation through pulmonary blood vessels
-If blood supply inadequate, oxygenation is inadequate
-Perfusion is generated & maintained by three functions:
Pumping action of heart
Blood vessels
Blood volume
cellular effect of shock
-Impaired cellular metabolism causes:
Release of vasoactive inflammatory mediators, including histamine
Increased production of oxygen free radicals
Excessive lactic acid & hydrogen ions causing intracellular acidity
-promoting cellular dysfunction and death
shock
-Shock: derangement of oxygen delivery & consumption at a cellular level.
why body changes to anaerobic
Anaerobic- body has lack of blood (not being pumped fast enough or loss of blood) therefore lack of oxygen- so must convert to anaerobic-
what happens in anaerobic metabolism
- glycolysis is to slow to make enough ATP that body needs
- so Pyruvate is converted into lactic acid which heart can use as fuel.
- however this accumulates in cell & diffuses into extracellular fluid, damaging internal and external portions of cell as to acidic (E.g. lactic acidosis in shock)
conversion out of anaerobic
Conversion of pyruvate to lactic acid is reversible if oxygen supply is restored
Lactic acid converted back to pyruvate, & used for energy or to synthesis glucose
WHY DO WE CARE ABOUT ATP PRODUCTION
because lactic acid impairs Sodium-Potassium pump operation
-this results in excess sodium in cells- causes cellular oedema & increased cell membrane permeability
-Results in cellular death & release of intracellular contents to extracellular space causing further damage
-Lactic acid accumulates in intracellular & extracellular spaces
Causes further damage
Sympathetic response
Extrinsic reflexes and Higher neural control centre (chemo and baro receptors) activate sympathetic response.
-epinephrine & norepinephrine released, AND activation of alpha & beta (adrenergic) receptors
-Alpha receptors: vasoconstriction
Constriction of small arterioles & arteries, increased peripheral vascular resistance
-Beta 1 receptors: increase in heart rate and force of contraction
-B2 receptors: vasodilatation of skeletal muscle & relaxation of bronchioles
Increasing HR & systemic vasoconstriction, as well as dilation of bronchioles in the lung – fight or flight!
REnin angiotensin aldosterone system
Kidneys: major role in regulating arterial BP & altering blood volume
Kidney perfusion decreases when arterial BP drops
In response, kidneys produce & release renin from juxtaglomerular apparatus (JGA)
Renin catalyses reactions producing Angiotensin 2 (in blood)
Angiotensin II acts on blood vessels, causing vasoconstriction
Also acts on adrenal gland, causing aldosterone release
Causes kidney tubules to increase sodium reabsorption, resulting in more fluid being retained (water follows salt; thus, vascular blood volume & arterial blood pressure increased)
Contributes to long-term BP regulation
hypovalemic shock
- Diminished blood volume resulting in inadequate vascular filling – i.e. no blood/fluid in the circulatory system
- Most common form of shock
- May also cause third-space losses, where extracellular fluid shifts from the vascular compartment to interstitial space (surrounding tissues)
- Occurs with acute loss of 15-20% of circulating volume (70kg adult 850mls
- Acute, fatal haemorrhagic shock categorised by metabolic acidosis, hypothermia & coagulopathy
hypovaleic shock compesatory mechanisms
Compensation- your bodies little (periphreal) vessels tighten up to try and keep up O2 levels
hypovalemic shock-The “Deadly” Trauma Triad:
as core temperature decreases, so does body’s ability to stop bleeding as cold temp increasing blood viscosity. which the body then tries to correct by vasodilating- causing more bleeding
coagulopathy-(lactic acidosis)-acidosis(decreased myocardial efficiency)-hypothermia(inhibiting coagulation cascade)
cardiogenic shock
- Heart pumps blood insufficiently to meet body’s demands
- Stroke volume & cardiac output is reduced
- Coronary artery perfusion eventually impaired due to increased preload and afterload so no oxygenation occurs around body
- observed with-Decreased cardiac output, Hypotension, Hypo-perfusion, Indications of tissue hypoxia