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Shock (Boards and Beyond) (Major types of Shock (Obstructive…
Shock (Boards and Beyond)
Life-threatening fall in BP
BP = CO X TPR
if either CO or TPR falls then shock
lo CO from
loss of contractility
low intravascular volume
low TPR
Peripheral vasodilation
Major types of Shock
Cardiogenic
cardiac disorder leading to a fall in CO
pts w/ massive MI often get shock due to fall in contractility
Signs
Hallmark: when LV is not working (MI, advanced HF w/ depressed LV EF)
high cardiac pressures
low CO
Hi SVR
SNS response
Treatment:
inotropes
increase contractility
milrinone
dobutamine
Hypovolemic
fall in intravascular volume
fall in CO
signs
poor fluid intake, +vomiting + diarrhea
High fever: pts have losses in lungs
classic: massive hemorrhage
Low cardiac pressures
Hi SVR: normal SNS response to low tissue perfusion
Treatment
add volume
RBC transfusion
IV fluids
Distributive
massive peripheral vasodilation: blood is in periphery but not in vessels
Classic/common: septic shock
infection leads to peripheral vasodilation
Anaphylactic
allergic rxn causes shock
Hallmark
low SVR
only type w/ low SVR
Diffuse vasodilation and or endothelial dysfunction
leaks out of vascular space into tissue beds
classically: CO is high
lowering vascular resistance, lowering afterload in LV
CO goes up
Reality: CO is variable in distributive shock
Cardiac pressures are variable
Neurogenic
intercerebral bleed
Treatment:
pressors
phenylephrine
Epinephrine
norepinephrine
Obstructive
special: outflow is obstructed
Low CO despite normal contractility in LV
Tamponade
LV and RV are normal but restricted so CO falls
Tension pneumothorax
hi P in thorax impairs ability of heart to fill, despite normal heart
Massive PE
poor blood flow from RV to LV, CO drops
Hi SVR
Like Cardiogenic shock but ventricles are working normally
Diagnosis: Imaging
shows fluid around heart, pneumothorax, PE. not from swan Ganz.
Treatment
relieve the obstruction
Different treatments are effective for different types of shock
determine from history
eg MI : cardiogenic
massive bleeding: hypovolemic shock
if cause remains unknown: Test
Swan Ganz Catheter
pulmonary artery catheter
moving the Cath thru chambers, can measure RA, RV and PA pressure
Then wedge the catheter: inflate balloon at tip into Pulmonary artery- will sense pressure beyond the balloon (LA)
back flow from LA "wedge Pressure"
Measures pressures in RA, RV, PA, LA
can often determine the cause of shock
Can also take blood sample from PA
mixed venous O2 sat
use value w/ Fick eqn to determine CO
Fick equation
O2 consumed must equal O2 that leaves lungs after fully oxygenated minus O2 returned to lungs in venous blood
we further say this is = to CO (Art O2- Ven O2)
Zoom in to see this equation
3 more items...
knowing CO can be used to calculate SVR
Commonalities
High
BP
HR
Differences
Cardiogenic
low CO
RA, RV, Wedge P all hi
SVR is high (SNS)
Hypovolemic
low CO
Hi SVR
RA, RV, Wedge P all low
Distributive shock
Hi CO
Low SVR
RA, RV, Wedge P are variable or low
PEx
Cold skin
Hi SVR and low CO
poor perfusion of skin, esp hands
Cardiogenic shock
Hypovolemic shock
Warm or flushed skin
Low SVR and Hi CO
Distributive shock
Elevated JVP
Hi RA pressure
Cardiogenic shock
Pulmonary Rales
Hi LA pressure
Cardiogenic shock
Swan Ganz in Valvular Heart Disease
Normal pressures on L side of table
However notice the wedge pressure and LV pressure is different
MS
High LV pressure
AS
Venous Pressure tracings
tracing for RA and LA are roughly the same(just LA is higher)
see this tracing on a Wedge pressure
See giant V waves in mitral regurgitation
