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
what do you get in early gram negative sepsis?
decreased insulin, increased glucose
impaired utilization
What do you get in late gram negative sepsis?
increased insulin, increased glucose
secondary to insulin resistance
what is the MOA of Xigris?
fibrinolysis (activated protein C)
What are the signs of fat emboli? where do they usually come from?
petechia hypoxia confusion sudan red may show fat in sputum and urine lower extremity fx
What will echo show in pulmonary thromboemboli?
RV strain
When do you suspect PE?
PA systolic >40 decreased PO2 and PCO2 respiratory alkalosis chest pain cough dyspnea, increased heart rate
Air Emboli- what do you do?
place pt. head down and roll to left, aspirate air out with central line or PA catheter to RA/RV
When does an intra-aortic balloon pump inflate, deflate?
Inflates on T-wave (diastole); deflates on P-wave or start of q wave (systole)
What is a contraindication for an IABP?
Aortic regurgitation
When is an IABP placed?
Cardiogenic shock after CABG, MI or in patients with refractory angina. Decreases afterload.
Improves systolic blood pressure which improves coronary perfusion
Where are alpha-1 receptors
Vascular smooth muscle constriction; gluconeogenesis, glycogenolysis
What do alpha-2 receptors do?
Venous smooth muscle constriction
What do beta-1 receptors do?
Increase myocardial contraction and rate
What do beta-2 receptors do?
Relaxes bronchial smooth muscle, relaxes vascular smooth muscle, increases insulin, glucagon, rennin
What do dopamine receptors do?
Relax renal and splanchnic smooth muscle
What is the rate of low dopamine administration and what does it affect?
05 µg per kilogram per minute acts on dopamine receptors -renal
What is the medium dose for dopamine drip and what does it affect?
6 to 10 µg per kilogram per minute-beta-adrenergic acts on heart contractility
What is the dose for high-dose dopamine and what does it affect?
Greater than 10 µg per kilogram per minute acts on alpha-adrenergic receptors causes vasoconstriction and increased blood pressure
What is the initial drip rates for dobutamine and what does it do?
3 µg per kilogram per minute initially. 5 to 10 µg per kilogram per minute causes beta-1 activation increasing contractility. Greater than 15 µg per kilogram per minute causes alpha adrenergic activation -vasodilation and increased heart rate
What does milrinone do?
Phosphodiesterase inhibitor increases cAMP
Results in increased calcium influx and increased myocardial contractility
Also causes vascular smooth muscle relaxation and vasodilation
What does phenylephrine do?
Acts on alpha-1 receptors causes vasoconstriction
What does norepinephrine do?
Low-dose causes beta-1 activation increasing contractility
High-dose causes alpha-1 and alpha-2 activation
Potent splanchnic vasoconstrictor
What does epinephrine do?
Low-dose causes beta-1 and beta-2 activation causing increased contractility and vasodilation. Can decrease blood pressure at low doses
High-dose causes activation of alpha-1 and alpha-2 causing vasoconstriction. Increased cardiac ectopic pacer activity and myocardial O2 demand
What does isoproterenol do?
Beta-1 and beta-2 activation, increases heart rate and contractility, vasodilates.
Side effects are extremely arrhythmogenic, increased heart metabolic demand, may actually lower blood pressure
What does vasopressin do?
V1 receptors cause vasoconstriction of vascular smooth muscle
V2 receptors are intrarenal and cause water reabsorption at collecting ducts
V2 receptors are extrarenal and mediate release of factor VIII and von Willebrand factor
What does nipride to do?
Arterial and venous dilator. Can cause cyanide toxicity. Check thiocyanate levels
What does nitroglycerin do?
Predominantly veno dilation, modest effect on coronaries; decreased myocardial wall tension by decreasing preload
What does hydralazine do?
Alpha blocker
How do you measure lung compliance?
Change in volume divided by change in pressure.
High compliance means lungs easy to ventilate. Pulmonary compliance decreases in patients with ARDS, fibrotic lung disease, reperfusion injury, pulmonary edema.
What does aging do to lungs?
Decreases FEV1 and vital capacity, increases functional residual capacity
Where is the V/Q ratio highest?
Highest in upper lobes, lowest in lower lobes
What does increasing peep do?
Improves oxygenation through alveoli recruitment. Improves FRC.
How do you decrease CO2 on a ventilator?
Increase rate or volume
What does pressure support do?
Decreases the work of breathing
Why do you want to keep FI O2 below 60%?
Prevent 02 radical toxicity
When do you have a risk of barotrauma?
Plateaus greater than 30 and peaks greater than 50
What are the complications of hi Peep?
Decreased right atrial filling Decreased cardiac output Decreased renal bloodflow Decreased urine output Increased pulmonary vascular resistance
When do you use high-frequency ventilation?
Kids; tracheoesophageal fistula, bronchopleural fistula
What does inverse ratio ventilation do?
Helps reduce barotrauma
What is total lung capacity?
Lung volume after maximal inspiration. TLC equals FVC plus RV
What is forced vital capacity
Maximal exhalation after maximal inhalation
What is residual volume
Lung volume after maximal expiration
What is tidal volume?
Volume of air with normal inspiration and expiration
What is functional residual capacity?
Long volume after normal exhalation. FRC equals ERV plus RV
Surgery, sepsis, trauma all decrease FTC
What is expiratory reserve volume?
volume of air that can be forcefully expired after normal expiration
What is inspiratory capacity
maximum air breathed in from FRC
What is FEV1?
forced expiratory volume in 1 second after maximal inhalation
What is minute ventilation?
TV x RR
What does restrictive lung disease do to lung function tests?
decreased TLC
decreased RV
Decreased FVC
FEV1 can be normal or increased
What does obstructive lung disease do to lung function tests?
increased TLC
increased RV
decreased FEV1
FVC can be normal or decreased
What is dead space?
normally to the level of the bronciole (150mL)
increases with drop in cardiac output, PE, pulmonary HTN, ARDS, excessive PEEP
can lead to high CO2 buildup
-area of lung that is ventilated but not perfused
What does COPD do to lung function?
increases work of breathing because of prolonged expiratory phase
work of breathing normally 2% of total body VO2
what is ARDS and what does it do to lungs?
mediated by cellular inflammatory process increased proteinaceous material increased gradient increased shunt most common in sepsis
Diagnosis of Acute lung injury?
acute onset
bilateral pulmonary infiltrates
paO2/FiO2 </= 18 or no clinical evidence of LAH
Diagnosis of ARDS
acute onset
bilateral pulmonary infiltrates
PaO2/FiO2 <200
What is SIRS mediated by? Criteria?
TNF alpha and IL-1
temp >38 or 12 or 90
Most potent stimulus for SIRS?
lipopolysacharide (Lipid A)
Diagnosis of Sepsis?
SIRS with clinical evidence of infection
sepsis with organ disfunction
Septic shock?
Sepsis and arterial hypotension despite adequate volume resuscitation
Muti organ dysfunction?
progressive but reversible dysfunction of 2 or more organs
