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57 Cards in this Set

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Why wasn't ARDS seen in patients b/f the '60s?
B/c patients didn't survive the events that can trigger ARDS.
Define ARDS.
Syndrome characterized by acute onset of dyspnea, bilateral infiltrates on CXR/CT, hypoxemia, absence of HF, and presence of an appropriate trigger.
If patient is laying supine, where does ARDS predominately occur.
Posterior portion of lungs
P/F ratio
arterial oxygen (PaO2) divided by FiO2 (21% in B'ham)
Normal P/F ratio.
450
What is the cutoff for P/F ratio for acute lung injury?
300
What is the most common cause of bilateral infiltrates?
CHF
ARDS will not respond to ____, but CHF will.
diuretics
A ___ PCWP suggests that volume overload is not the cause of bilateral infiltrates.
low (<18)
Direct triggers of ARDS
near-drowning, aspiration, pneumonia, pulmonary contusion, emboli, or reperfusion
Indirect triggers of ARDS
sepsis, severe non-thoracic trauma, blood transfusion, cardopulmonary bypass for surgery, drug overdose, pancreatitis
How do indirect triggers cause ARDS?
release cytokines and other pro-inflammatory mediators that cause lung to react by inflamming
In general, indirect triggers of ARDS are _____ than direct triggers.
worse...sepsis the worst
Pathophysiology of ARDS.
Injury to alveolar endothelial membrane causes the alveoli to floow w/ fluid, protein, RBCs, WBCs, etc. Alveoli are no longer functional.
Proteinacious conglomerations that line inside of alveolar wall.
hyaline membranes
Pathognomonic lesion of ARDS
hyaline membranes
Late stages of ARDS.
More inflammatory cells move into lung. Type I cells die and Type II cell attempt to repopulate by hyperplasia. Fibrosis/scarring ensue, or inflammation resolves.
First day or two of ARDS.
non-cardiogenic edema
Final step of ARDS.
Inflammatory filtrate followed by fibrosis.
During the initial phase of ARDS what is the primary problem?
a shunt, creating hypoxemia
In the 7-20 day period, what is a problem caused by the fibrosis?
wasted ventilation/dead space, patient has difficulty eliminate CO2
Most common pattern on biopsies seen in ARDS patients. (pathologist's definition of ARDS)
Diffuse Alveolar Damage (DAD)- pathognomonic finding for ARDS
How DAD lungs appear grossly?
heavy, full of blood, inf. cells, protein
What is involved w/ general supportive care in ARDS?
CV support, infection control, nutrition, fluid and electrolytes
What is involved in the conservative fluid mngt in ARDS patients?
dry out the lungs to accelerate removal of ventilatory support, major risk of dysfxn of other organs due to dehydration, over 7 days match fluid intake to fluid output
What is the liberal fluid mngt of ARDS patients?
give plenty of fluids to prevent failure of other organs
What was the finding in the study comparing conservative vs. liberal fluid mngt?
Low fluid strategy was not associated w/ organ failure as was feared. Patients on both strategies survived equal amt of time w/ conservative patients having fewer days on ventilator and in the ICU.
What is the benefit of using a pulmonary catheter as opposed to a central line in managing an ARDS patient?
no difference in outcome
How does NO improve ventilation/perfusion matching?
preferentially goes to well ventilated areas and dilates pulmonary vasculature in that area, diverting blood from poorly ventilated areas
How does NO improve lung fxn?
improves V/Q matching, improves oxygenation, reduces pulmonary artery pressures, anti-inflammatory properties
Why does improving oxygenation have no proven benefit for ARDS?
most people don't die from resp failure
What are some cons for using NO for ARDS patients?
1) doesn't improve survival
2) response not sustained
3) expensive
4) when you back off, pulm. HTN gets worse than it was b4
5) requires sophisticated equipment
T/F: Corticosteroids can be quite effective if given in the acute phase (24-48 hrs) of ARDS.
False. May actually hurt patient.
How does the use of corticosteroids improve the long term outcome for ARDS?
no improvement in 60 day mortality
increase in ventilator free days
decrease in ICU days
reduce incidences of shock
Complications of using corticosteroids in ARDS.
development of polyneuropathy and neuromuscular disease
Main strategy for dealing w/ ARDS.
ventilatory mngt
What form of ventilatory mngt is most often used in ARSD?
invasive positive pressure
Advantages of invasive positive pressure ventilation.
1) can give very high Fi02
2) can give high pressures
Disadvantages of invasive positive pressure ventilation.
1) easy to catch infection
2) uncomfortable
3) sedation required
4) limited mobility
Five modes of mechanical ventilation.
1) Certain volume at certain rate (volume control)
2) Certain pressure at certain rate (pressure control)
3) patient triggered
4) machine triggered
5) hybrids
How does PEEP maintain oxygenation?
prevents alveoli from collapsing at the end of expiration by staying above atmospheric pressure
Problems associated w/ mechanical ventilation in ARDS.
1) high airway pressure which can cause additional injury and pneumothoracies
2) due to shunting, have to use high FiO2 which can be toxic to lung
Compliance is low in ARDS. Large change in pressure results in a _____ change in volume.
small
Complications of mechanical ventilation:
1) infection & pneumonia
2) hypotension
3) barotrauma (caused by pressure)
4) sinusitis (prevents adequate sinus drainage)
5) ventilator induced lung injury
What is the problem w/ giving a damaged lung high tidal volumes at high pressures to maintain normal gas exchange?
causes additional damage to lung causing spilling of cytokines and mediators causing a systemic inf. response --> hypotension, etc.
What is the ARDSnet strategy for mechanical ventilation?
low tidal volumes (6cc/kg)
low airway pressures
tolerate poor gas exchange
Which position improves PO2?
prone
What is ECMO?
extra corporeal membrane oxygenation, basically coronary-pulmonary bypass
What is the present mortality for ARDS?
30%
What trigger for ARDS generally has the best outcome?
trauma -- fewer other problems, generally young patients
What trigger for ARDS has the worst outcome?
sepsis - mortality for ARDS due to sepsis is 50%
T/F Mortality for ARDS can be determined by the initial gas exchange.
False
Causes of death in ARDS
1) sepsis and multi-organ failure
2) resp. causes (<25%)
T/F: At a year, most people who survive ARDS have near-normal pulmonary fxn.
True
T/F: ARDS is associated w/ significant weight loss.
true
What is the most likely PFT to remain impaired long-term in an ARDS patient?
carbon monoxide diffusing capacity
T/F: ARDS patients, if they survive, generally do well long term.
False. Although they usually have normal pulmonary fxn., but other organs don't do as well.