Chapter 16 - Critical Care Flashcards
How do you calculate MAP?
CO x SV
How do you calculate CI?
CO/BSA
How do you calculate SVRI?
SVR x BSA
what percentage of CO does the brain, kidney, heart get?
Brain 15%
Kidney 25%
Heart 5%
Preload is linearly related to what?
end diastolic volume and filling pressure
What is afterload?
resistance against the ventricle contracting
What is stroke volume determined by?
LVEDV, contractility and afterload
How do you calculate ejection fraction?
stroke volume/end diastolic volume
What is end systolic volume determined by?
contractility and afterload
At what heart rated does CO start to decrease?
150- decreased diastolic filling time
What % of LVEDV does atrial kick account for?
15-30%
What is the Anrep effect?
automatic increase in contractility secondary to increased afterload
What is the Bowditch effect?
automatic increase in contractility secondary to heart rate increase
what is the radial diastolic and systolic pressure in relationship to aortic mean pressures?
diastolic slightly lower, systolic slightly higher
How do you calculate O2 consumption (VO2)
CO x (CaO2 - Cvo2)
What is the normal O2 delivery to consumption ratio?
5:1
Is O2 consumption supply dependent?
No, does not change until levels of delivery are very low
What causes a right shift in the O2 dissociation curve?
increased CO2 increased temperature Increased ATP production increased 2,3-DPG production increased H+ (decreased pH)
What is the normal p50 (O2 at which 50% of O2 receptors are saturated)?
27mmhg
When does SvO2 go up?
shunting or decreased extraction
When does SvO2 go down?
increased extraction, decreased delivery
What can make wedge pressures inaccurate?
pulmonary htn aortic regurg mitral stenosis/regurg high peep poor LV compliance
Where should a swan-ganz catheter be placed?
zone III (lower) lung
What do you do with hemoptysis after flushing a swan-ganz catheter?
increase PEEP which will tamponade the pulmonary arter bleed, mainstem intubate non-affected side
can try to place fogarty balloon down the affected side- may need thoracotomy and lobectomy
What are contraindications to swan?
previous pneumonectomy, left bundle branch block
What is the only way to measure pulmonary vascular resistance?
swan
What are the primary determinants of myocardial O2 consumption?
ventricular wall tension and HR
what has a higher PO2- pulmonary capillaries or LV?
pulmonary capillaries- LV gets unsaturated bronchial blood
what is the normal aa gradient?
10-15mmhg
What blood has the lowest venous saturation?
coronary venous (30%)
What are the signs of acute adrenal insufficiency?
cardiovascular collapse
unresponsive to fluids and pressors
signs of chronic adrenal insufficiency?
hyperpigmentation, weakness, weight loss, GI sx
decreased K
increased Na
fever, hypotension
what steroids are at 1x potency of endogenous?
cortisone, hydrocortisone
What steroids are at 5x potency of endogenous?
prednisone
prednisolone
methylprednisolone
What steroids are at 30x strength of endogenous steroids?
dexamethasone
What do you get with neurogenic shock?
loss of sympathetic tone decreased HR decreased BP warm skin tx: volume then phenylephrine steroids for blunt spinal trauma
what is the initial alteration in hemorrhagic shock?
increased diastolic pressure
what is beck’s triad?
hypotension, jugular venous distention, muffled heart sounds
what does echo show in tamponade?
decreased RA filling pressures
What is the early sepsis triad?
hyperventilation, confusion, respiratory alkalosis