ICU Flashcards
What is an adequate cerebral perfusion pressure?
55-60 mmHg
How do we calculate CPP?
MAP - ICP = CPP
In coma pts, suspected of etoh abuse, what do we give before glucose?
thiamine 1mg/kg first
glucose after
**if glucose given first can precipitate Wernicke’s encephalopathy
In pts with opioid induced coma, what do we give?
naloxone 0.4 to 2 mg
Coma due to benzo intoxication, we give what?
flumazenil 0.2 mg
Hyperventilation is effective in lower ICPs, but this effects is lost within?
24 hrs
brain normalizes to lower PaCO2
Monro-Kelli hypothesis?
pressure inside the head will rise if any intracranial component will rise (blood, CSF, brain) because the cranial vault is fixed
Tx for status epilepticus?
benzos like lorazepam (0.1 mg/kg) followed by phenytoin 1g
Major complications assc. w/seizures?
rhabdomyolysis
hyperthermia
cerebral edema
Sedation scales used in ICU?
Richmond Agitation Severity Scale
0= alert and calm
4= combative, dangeorus to staff
-5= unarousable
When is skeletal muscle relaxation warranted in ICU setting?
minimize o2 consumption
facilitate patient-ventilator synchrony (prone positioning)
Two classes of neuromuscular blocking drugs?
depolarizing NMBs
non-depolarizing NMBs
This drug is a depolarizing NMBs:
succinylcholine
How does depolarizing NMB like succinylcholine work?
binds to ACh receptor at motor end plate
cause muscle depolarization –> seen as muscle fasciculations
Onset and half life of succinylcholine?
rapid onset
short half-life
When do we use succinylcholine?
paralytic of choice for RSI
SE of succinylcholine?
rhabdomyolysis
hyperkalemia
muscle pain
malignant hyperthermia
How do non-depolarizing NMBs work?
bind ACh receptors but do not activate them
block receptor, inhibit it’s function
What are the two types of non-depolarizing NMBs?
steroidal
non-steroidal
What are the amino steroidal non-depolarizing NMBs?
rocuronium
vecuronium
pancuronium
When do we use rocuronium?
rapid onset of action
intermediate duration
**used for short procedures and prolonged relaxation
Onset of action of vecuronium?
NMB within 1-2 minutes
lasts 30 minutes
With vecuronium we have to worry about?
renal and liver impairment
leads to prolonged response
Pancuronium contraindicated in pts with?
CAD
causes tachycardia
Non-steroidal non-depolarizing NMBs include?
atracurium
cis-atracurium
Atracurium is intermediate acting with minimal cardiovascular effects, but it does have;
histamine release
** can be used in pts with liver/kidney dysfunction
When placing arterial catheters which are preferred sites?
radial and DP arteries
thrombosis and distal ischemia can be minimized by placing a-lines in places with good collateral circulation
How do we calculate MAP?
MAP = DBP + 1/3 (SBP - DBP)
Two basic modes of positive pressure ventilation?
volume control–> tidal volume is pre-selected and automatically delivered by ventilator
pressure control–> inflation pressure is pre-selected
During volume control ventilation, whats happening to the airway pressure?
pressure rises steadily until pre-selected volume delivered
What’s Peak pressure?
airway pressure at the end of each lung inflation
pressure needed to overcome both elastic and resistive forces in the lungs and chest wall
What is the plateau pressure?
peak pressure in the alveoli at the end of inspiration
Peak pressure of alveoli at end of inspiration?
plateau pressure
How do we check plateau pressures?
prevent the pt from exhaling with an inspiratory hold (for 1 second)
What is ZEEP?
in a normal lung, there is no airflow at the end of expiration
at that time, pressure in alveoli is equal to atmospheric pressure
this is called zero-end-expiratory pressure
What do we use PEEP for?
prevents collapse of distal airspaces at the end of expiration
and to open collapsed alveoli
What is occult PEEP?
auto-PEEP
when we see continued airflow at end of expiration
lungs do not completely empty and alveoli remain positive even though proximal airway pressure falls to atmospheric pressure (0)
Where do we see auto-PEEP?
seen as result of dynamic hyperinflation in pts with COPD/asthma
or vent settings where pts have decreased time for exhalation
What’s mean airway pressure?
avg pressure in airways during a ventilatory cycle
5-10 cm H20 in normal lungs
10-20 cm H20 in lungs w/airway obstruction
20-30 cm H20 for non-compliant lungs (stiff)
How do we prevent atelectrauma?
during normal positive pressure ventilation opening and closing of alveoli causes shear forces and damage
PEEP keeps small airways open during expiration
What is barotrauma?
positive pressure ventilation can cause leaks from rupture in airways and distal spaces
air escapes and can cause pneumothorax, pneumomediastinum, subcutaneous emphysema, pneumoperitoneum
Lung protective ventilation guidelines?
ventilation begins with tidal volume of 8cc/kg of predicted body weight, weaned down to 6cc/kg after
keep plateau pressure less than 30 cm H20
PEEP of 5 minimum, is used to prevent alveolar collapse
permissive hypercapnia allowed
How does positive pressure influence cardiac function?
positive intrathoracic pressure venous return to heart
positive pressure on outer surface of heart also decreases ventricular filling during diastole
positive pressure ventilation increases pulmonary vascular resistance which impacts right ventricular stroke output, so RV becomes distended and affects LV size, which affects LV function (also because of increased vascular resistance, you have less oxygenated blood returning to LV)
What are the two basic modes of positive pressure lung inflation?
volume control; where inflation volume is constant
pressure control; where inflation pressure is constant
What are the 6 basic modes of positive pressure lung ventilation?
Volume Control
Pressure Control
Assist Control
Pressure support
Intermittent Mandatory Ventilation
Positive end-expiratory pressure
Describe volume control ventilation?
the inflation tidal volume is pre-selected
lungs are inflated at a constant flow rate until desired volume is delivered
Advantage of volume control ventilation?
able to deliver a constant volume despite changes in mechanical properties of lungs
In volume control ventilation, how does ventilator deliver constant volume when airway resistance increase or lung compliance decrease?
ventilator will generate higher pressure to deliver preselected volume
this maintains the desired minute ventilation
Disadvantage of volume controlled ventilation?
- airway pressures and end of inspiration are higher for VC vs PC ventilation
but this does not affect barotrauma/atelectrauma
- duration of inspiration is short, can lead to uneven alveolar filling
Describe pressure control ventilation?
desired inflation pressure is selected
Advantage of pressure control ventilation?
ability to control peak alveolar pressures, which relates to alveolar overdistention and lung injury
maintain this < 30 cm H20
Why is pressure control ventilation more comfortable for pts than volume control ventilation?
high initial flow rates
longer duration of inspiration
Which is preferred by pts, PC or VC ventilation?
pressure control; has higher initial flow rates and longer duration of inspiration
Major disadvantage of pressure control ventilation?
see decrease in alveolar volume when there is increase in airway resistance or decrease in lung compliance
What is Assist-Control Ventilation?
allows pt to initiate a ventilator breath
if this is not done by pt, ventilator breaths are delivered by machine at a pre-selected rate
ventilator breaths during AC can be volume or pressure
What are the two triggers for assist-control ventilation?
- patient triggered breath via spontaneous inspiratory effort
- absence of spontaneous inspiratory effort by pt (no interaction between pt and ventilator); so ventilator will deliver breaths at a pre-selected rate
What’s the ratio of inspiration;expiration that we strive for?
inspiration; expiration ratio of 1;2
Why do we want an inspiration;expiration ratio of 1;2?
to prevent breath stacking
you want complete exhalation before you deliver another breath or else you get dynamic hyperinflation and auto-PEEP
What is SIMV?
synchronized intermittent mandatory ventilation
designed to allow spontaneous breathing between ventilator breaths
ventilator breaths in SIMV can be volume or pressure
Disadvantages of IMV?
increased work of breathing
decrease in cardiac output in pts with LV dysfunction
Major indication for Intermittent mandatory ventilation?
pts with rapid breathing and incomplete exhalation during assist control ventilation
We don’t use IMV in which pts?
pts w/resp muscle weakness and left heart failure
What is alveolar recruitment?
low levels of PEEP 5-10 cm H20 help prevent collapse of distal airspaces
high levels of PEEP 20-30 cm H20 help reopen distal airspaces that are consistently collapsed
this increases available surface area in lungs for gas exchange
What is the dilemma with alveolar recruitment?
how do we know if high PEEP is promoting alveolar recruitment vs alveolar overdistention in the already normal parts of lung?
when PEEP is causing alveolar recruitment; lung compliance increase
when PEEP causing alveolar overdistention; lung compliance decreases
What does the PaO2/Fio2 ratio signify?
efficiency of gas exchange in lungs
How can we use PaO2/Fio2 ratio to help us use PEEP for alveolar recruitment?
when PEEP is causing recruitment, the ratio will increase
when PEEP is not causing recruitment, the ratio will remain the same or decrease
Assist control AKA?
CMV; continuous mandatory ventilation
How does assist control (CMV) work?
patient triggers the vent
pt takes a breath, and negative pressure sensor is detected in ventilator
ventilator then delivers a specific volume
if pt does not take a breath, ventilator is already preset to a specific rate, say 12, and will deliver those 12 regardless
How does pressure support work?
pt initiates all the breaths
occurs only during inhalation
popular weaning mode
pt receives anywhere from 5-15 cm H20 pressure
In AC mode, we program in a set volume for delivery into lungs, what is variable?
pressure is variable depending on lung compliance
What is peak vs plateau pressure?
peak pressure==> pressure when there is airflow going into lungs, resistance felt along the airways as air is moving in
plateau pressure–> measured when airflow stop, air is in alveolis, and has to do with lung compliance
What can give you high peak pressures?
problem with the airways
bronchospasm
secretions
mucus plug
ETT occluded
What can give you high plateau pressures?
things that decrease lung compliance;
pneumo
Pulmonary edema
ARDS
pneumonia
What is the rapid shallow breathing index?
tobin index for extubation
RR/TV (20/.5)= 40
tobin index > 105 is not good
tobin index < 105 is good
Explain air leak test;
when you put ETT down trachea and inflate balloon, that balloon can cause inflammation around the trachea, when someone is ready to be extubated you do an air leak test
balloon is deflated and you listen for air to come up around the tube, if no air leak is heard, means there is some inflammation and if you pull tube out, risk of closing off trachea
THings to check before weaning pt from ventilator?
secretions?
oxygenating well? Pao2/Fio2 >200, Fio2 <40? PEEP < 5-8?
can pt protect their airway
pulmonary function adequate ?
One of the most effective means of preventing stress gastritis?
early enteral feeding
What is abdominal compartment syndrome?
increased intra-abdominal pressure assc with adverse physiological consequences
What is secondary abdominal compartment syndrome?
ACS in absence of abdominal/pelvic pathology
usually due to shock and edema from aggressive resuscitation
Cardiovascular effects of abdominal compartment syndrome?
decreased CO due to diminished venous return because of increased abdominal pressures
Increased abdominal pressures effects on lungs?
decreased diaphragmatic excursion
decreased pulm compliance
high airway pressures
decreased tVolumes
resp acidosis
Most common cause of oliguria in surgical icu pts is?
pre-renal hypovolemia
How can a spot urine sodium tell us if AKI is pre-renal vs intrinsic AKI?
U sodium less than 20== pre-renal
U sodium > 40 == intrinsic
RIFLE criteria used for what?
assess for AKI
FeNA < 1% means what?
pre-renal cause of AKI
FeNA >3% means what?
renal parenchymal or post-renal problem of AKI
Primary bacterial peritonitis occurs in >20% of cirrhotic pts with ascites and usually has what type of bacteria?
monomicrobial (pneumococcus)
polymicrobial peritonitis usually indicative of intra-abdominal abscess or perforated viscus
What is hepato-renal syndrome?
renal problem seen in pt with end-stage liver disease due to systemic vasodilation, hypovolemia, and increased RAAS
pts have azotemia, oliguria, low urine Na (<10), high urine osmolality
In AC mode ventilation, what type of breaths can the pt get?
pt can get a breath delivered by the machine, triggered by a set time (every 6 seconds, machine delivers 500cc of volume for example)
pt can get a breath when they trigger it on their own (aside from set volume delivered every 5-6 seconds by machine, pts can themselves trigger a breath, when it’s triggered machine will deliver another breath to pre-set volume, only difference is this is not triggered by time, but by the patient)
