Shock/Hypotension Flashcards
Arterial pressure dependent on
volume of blood within arterial system
rate of inflow (from LV) vs rate of runoff to veins (blood leaving)
Arterial pressure rises when
inflow is greater than outflow (rapid ejection phase of ventricular systole)
Arterial pressure falls when
inflow is less than outflow (Diastole)
Blood pressure in systemic arteries will be lower than normal when
blood volume in arteries is decreased due to decreased cardiac output or decreased TPR (inc rate of runoff from arteries to veins)
Diastolic pressure
determined by factors that alter rate or time of runoff
1) rate of runoff- how fast blood flows from arterial to vennous system (determined by TPR)
2) runoff time- runoff during diastole; determined by heart rate- dec HR longer time for runoff, diastolic pressure decreased
3) arterial systolic pressure- starting pt from which runoff causes pressure to decrease
Arterial systolic pressure determined by
1) ejection rate- from LV; how quickly blood volume in arteries increase
2) SV- arterial pulse pressure index of SV. volume increases, pulse pressure increases.
3) arterial compliance- chronic decreases in compliance increase systolic pressure
4) arterial diastolic pressure- pressure begins to increase during ejection
pulse pressure in aortic stenosis is
decreased because of rate of ejection is decreased due to high resistance of aortic valve
MAP calculation
MAP= Diastolic + 1/3 Pulse pressure
Pulse pressure= systolic - diastolic pressure
MAP=COxTPR
MAP is the driving pressure for blood flow in systemic circulation
HR controlled by
PARA and SYM on SA node
SYM nerves influence
HR, preload, afterload, inotropic state
SV determined by
preload, afterload, inotropic state
Preload
stretch on myocardial fibers before contraction
-determined by EDV
related to ventricular filling- affected by heart rate (dec hr, inc filling time, EDV greater, inc SV) and rate of venous return (inc vr, inc rate of filling, edv greater, inc sv)
Starling’s law
stroke volume inc when preload is inc due to greater stretch which results in more favorable overlap of thin and thick filaments
afterload
ventricular wall tension during ejection
-resistance that must be overcome to eject blood
pressure at start of ejection (aortic diastolic pressure) or peak pressure (aortic systolic pressure) used as indices of afterload
-changes in TPR affect afterload- inc in TPR slows rate of runoff of blood from arteries to veins- inc arterial diastolic pressure- inc afterload
inc in TPR will
slow rate of runoff from arteries to veins–> inc arterial diastolic pressure –> inc afterload
Inotropic state
represents force of contraction
dep on cytosolic calcium level
more ca- more cross bridges formed- inc contractile force
NE will
enhance calcium entry into myocytes and inc inotropic state
Venoconstriction
decrease venous compliance, increasing venous pressure- increase venous return to the heart- increasing sv on next beat
hypovolemic shock
decreased blood volume resulting in inadequate CO
skin feels cold and clammy because decreased blood flow to skin
low central venous pressure
dec blood volume–> dec venous return–> dec EDV–> dec SV–> dec CO–> dec MAP
distributive shock
generalized systemic vasodilation- dec TPR
warm shock
cardiogenic shock
inadequate cardiac output by diseased or impaired heart
high central venous pressure
skin feels cold and clammy
Blood flow to most systemic organs is reduced in hemorrhagic shock bc
map is reduced and
vascular resistance is increased due to increased sym firing to arterioles via baroreflex
how do brain and heart maintain blood flow during shock
local arteriolar dilation by local vasodilators
in other organs- arterioles constrict due to inc SYN via baroreflex
Increased myocardial O2 consumption when
inc inotropic state (beta1 activation)
inc hr
inc afterload, preload, hypertrophy