Critical Care Flashcards by Lauren Buhl

What is the first step in resuscitation of a drowning victim?

rescue breathing

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How should CVLs placed under emergency conditions be managed?

replaced within 24 hours at a new site

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Why is propofol infusion syndrome associated with lactic acidosis?

propofol prevents mitochondria from using fatty acids as an energy source, so after glucose and amino acids stores are used up, lactic acidosis develops

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What is the equation for arterial oxygen content?

CaO₂ = (1.34 x Hgb x SaO₂) + (0.003 x PaO₂)

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What is the equation for oxygen delivery?

DO₂ = CaO₂ x CO

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What is the equation for oxygen consumption?

VO₂ = 1.34 x (SaO₂ - SmvO₂) x Hgb x CO

SmvO2 = SaO2 - [VO2/(1.34 x Hgb x CO)]

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What is the oxygen extraction ratio?

ER = VO₂/DO₂

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What is the alveolar gas equation?

PA_O2 = FiO2(P_atm - P_H2O) - Pa_CO2/RQ

P_atm = 760 mmHg

P_H2O = 47 mmHg

RQ = 0.8

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What factors affect the Hgb dissociation curve?

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What is a normal value for VO₂?

250 mL/min

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What is dysoxia?

When oxygen consumption (VO2) decreases because oxygen delivery (DO2) is so low (i.e., no more oxygen can be extracted from what is delivered)

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What is the Bohr effect?

Increased CO₂ binding to Hgb reduces its affinity for O₂ (i.e., a right shift in the hgb dissociation curve)

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What is the Haldane effect?

oxygenated Hgb has a lower affinity for CO₂ (facilitating CO₂ unloading in the lungs)

deoxygenated Hgb has a higher affinity for CO₂ and can act as a buffer

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What is the law of LaPlace?

pressure = 2 x wall tension x wall thickness/radius

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How is the majority of CO2 carried in the blood?

as bicarbonate in the plasma and RBCs

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Where does carbonic anhydrase act to store CO2 as bicarbonate in the blood?

in endothelium and RBCs

What is the P/F ratio in ARDS?

Berlin criteria for PaO₂/FiO₂*

200-300 = mild ARDS

100-200 = moderate ARDS

< 100 = severe ARDS

*with PEEP of at least 5

What are the components of ARDSnet ventilation?

low tidal volumes: 6 mL/kg and titrated down

keep plateau pressures < 30

PEEP for oxygenation and reduced atelectrauma

permissive hypercapnea

What is airway pressure release ventilation?

Two levels of CPAP with long periods spent at the high level (oxygenation) and brief periods spents at the low level (ventilation). Spontaneous respiration remains possible at both levels.

What is an RSBI? How is it used in the ICU?

rapid shallow breathing index = frequency*/TV**

*frequency in breaths/min

**tidal volume in liters

RSBI < 100 is predictive of successful extubation

What is the risk of ETTs left in place for more than 2-3 weeks?

subglottic stenosis

What are the SIRS criteria?

hypo/hyperthermia

tachypnea

tachycardia

high or low WBCs or left shift

What should be done if a patient aspirates on intubation?

suction the oropharynx
place the ETT
suction the lungs (to prevent pushing particulate matter into smaller airways)
begin ventilation

What is negative inspiratory force? What is the minimum value necessary for extubation?

a test of inspiratory force

-20 to -25 cm H₂O is minimum for extubation

What are the independent risk factors for stress ulcers requiring H2 blocker prophylaxis?

mechanical ventilation for \>48 h coagulopathy (plt \< 50, INR \> 1.5, PTT \> 2x control)

What is the most distinguishing receptor difference between norepinephrine and epinephrine?

only epinephrine is a clinically significant ß2 agonist

Which causes a greater increase in diastolic BP, norepinephrine or epinephrine?

norepinephrine \*ß2 agonist effects of epinephrine cause vasodilatation in some vascular beds, resulting in minimal change in diastolic BP\*

What receptors do the enantiomers of dobutamine agonize?

one enantiomer is a ß1 \>\>\> ß2 agonist one enantiomer is an a1 agonist

What is increased dromotropy?

increased conduction speed within the heart (particularly the AV node)

What is lusitropy?

diastolic relaxation achieved by decreasing cytosolic Ca²⁺ levels via SERCA-mediate Ca²⁺ uptake into the sarcoplasmic reticulum

How do alpha adrenergic receptors and beta adrenergic recpetors differ in the way they increase cytosolic calcium?

alpha adrenergic receptors: activate G_aq going through PLC \> DAG + IP3 \> release of intracellular Ca²⁺ stores beta adrenergic receptors: activate G_as going through adenylate cyclase \> cAMP \> PKA and increased intracellular Ca²⁺

How does inhaled NO result is smooth muscle relaxation?

NO \> guanylate cyclase \> cGMP \> smooth muscle relaxation \*PDE-5 breaks down cGMP and is inhibited by sildenafil\*

What is nesiritide, and how is it useful in treating decompensated heart failure?

recombinant BNP activates guanylate cyclase \> cGMP \> vasodilatation, thus encouraging forward flow

How can nitroprusside affect hemoglobin?

oxidizes the the heme iron from the 2⁺ to 3⁺ state, creating met-hemoglobin breaks down into CN^-, which can bind met-hemoglobin and create cyan-met-hemoglobin

How does cyanide toxicity result in acidosis?

CN- binds to cytochrome oxidase, preventing ATP production through the electron transport chain, necessitating anaerobic metabolism a resultant lactic acidosis

What happens to mixed venous O₂ during cyanide toxicity?

increases due to inability of tissues to utilize oxygen in the electron transport chain

How is cyanide toxicity treated?

Increasing the "sinks" for cyanide: 1) increasing methemoglobin with sodium nitrite 2) sodium thiosulfate, generating sodium thiocyanate which can be excreted by the kidneys

Which vasodilator is associated with improved subendocardial perfusion during periods of ischemia?

nitroglycerin

How is methemoglobinemia treated?

methylene blue