CRNA Boards Questions And Verified Answers

CRNA Boards – Questions And Verified Answers How much does the PaO2 decrease as we age? Correct Ans - PaO2 = 100 - (0.3 x age) An increased shunt (as seen with eldery) will further decrease PaO2 Oxygen delivery equation Correct Ans - DO2 = CO x CaO2 x 10 = 20mL/dL x 5L/min x 10) = 1000mL/min Oxygen carrying capacity of blood Correct Ans - • When 100% saturated, 1 gram hemoglobin carries 1.34 mL oxygen • CaO2 = (1.34 x hgb x SaO2) + (PaO2 x 0.003) = 20ml/dL Calculate Bicarb Deficit Correct Ans - Kg x 0.3 x Base Excess or (Desired bicard - measured bicarb).Divide by 2 for first dose CO2 production per minute Correct Ans - 200ml CO2/min 200ml CO2/250 ml O2 per min = 0.8

• This is the respiratory quotient used in the alveolar gas equation

oxygen consumption equation Correct Ans - VO2 = CO x (CaO2 - CvO2) VO2 = 3.5 ml/kg/min VO2 = ~250 ml/min or (FiO2I - FiO2E) x Mv = ml of O2 required Alveolar Gas Equation (PAO2) Correct Ans - - PAO2 = FiO2 x (Pb - PH2O) - (PaCO2/0.8)

• Subtract given A-a gradient to get expected PaO2 (arterial)

-PAO2 = 0.28(760-47)-(50/0.8)--> (-) A-a gradient FRC equation Correct Ans - FRC = ERV + RV (~2.5L) FRC = 35ml/kg of IBW Name what's in the high, intermediate, and low pressure system on the

anesthesia machine Correct Ans - -High: yolk, PISS, check valve,

pressure regulator 1 / 4

-Intermediate: master switch, pipeline inlet and pressure indicator, gas power

outlet, O2 flush valve, O2 pressure failure sensor, flow control valves

-Low: flowmeters, vaporizers, hypoxia prevention device, unidirectional

valves, pressure relief, common gas outlet

Nerves for an Ankle Block Correct Ans - Saphenous (from femoral:

medial foot)

• "saph=calf"

Deep Peroneal: webspace 1st & 2nd toe

Superficial Peroneal: dorsum of foot

Sural: lateral aspect of the foot

Posterior Tibial: Heel

Ankle block Mneumonic Correct Ans - TIPPED

- Tibial: Inversion, Plantar flexion

-Peroneal (deep): Eversion, Dorsiflexion

Femoral n. = patellar twitch Obturator n. = Adductor twitch Which nerve of the ankle provide motor/sensory to the foot? Correct Ans

• - Nerves with an "S" are sensory. The other 2 are sensory and motor

- Terminal branch of femoral N: Saphenous

• Terminal branch of sciatic N: Superficial peroneal, Sural, deep peroneal, tibial

Lower extremity sensory distribution Correct Ans - How much CO2 is produced after 1 minute of apnea Correct Ans - 12 mmHg for the first minute and 3.4 mmHg for every minute after Where do we monitor our NMBA? Correct Ans - Obicularis oculi (Facial nerve) - more sensitive. Relaxes first, comes back last Adductor Pollicis (Ulnar nerve) - in sync with the diaphragm Diaphragm vs Pharyngeal muscle sensitivity to paralytics Correct Ans - Diaphragm is resistant to NMBA

• will see a return of spont. breathing before we see a return of pharyngeal

muscle tone 2 / 4

Hence why even with a 4/4 twitch, we still reverse so the pt can breathe fully on their own Why would you not give succinylcholine to a stroke patient with residual (continued weakness/paralysis) symptoms Correct Ans - Upregulation of postsynaptic nicotinic cholinergic receptors can cause a profound hyperK response Where do the coronary sinuses dump into? Correct Ans - Right Atrium What percent does the MAC drop for each age group? Correct Ans - Drops by 6% per decade after 1 Where are the cardioaccelerator nerves Correct Ans - T 1 - T4

Intrinsic muscles of the larynx:

Posterior Cricoarytenoid Lateral cricoarytenoid Thyroarytenoid Cricothyroid

Aryepiglottic Correct Ans - -PCA: abduct (pulls cords apart)

-Lateral CricoArytenoid: adduct, Lets Close Airway

-ThyroaRytenoid: They Relax, shorten/adduct VC

-CricoThyroid: Cords Tense, elongate VC

-Aryepiglottic: Closes glottic opening

What is the #1 cause of M/M in post SAH pts? Correct Ans - Vasospasm What is the Law of Laplace? Correct Ans - Wall tension = Radius x Pressure -Increased tension when radius increases -increased pressure can then rupture an aneurysm What % of nerves are block with TOF twitches? Correct Ans - 4 twitches = 0 - 75% of receptors are still blocked

• twitches = 80-85% are still blocked 3 / 4

• twitches = 85-90%
• twitch = >90%

Correlation between clinical signs and train of four ratio Correct Ans -

Sustained head lift for 5 seconds: TOF = 0.6

Sustained leg lift: TOF 0.6

Retained tongue depressor: TOF 0.85

What are the 6 orbital muscles, their function, and their motor innervation?Correct Ans - -Superior rectus - surpraduction (CN3) -Inferior rectus - infraduction (CN3) -Medial rectus - Adduction (CN3) -Lateral rectus - Abduction (CN6) -Superior oblique - intorsion and depression (CN4) -Inferior oblique - Extorsion and elevation (CN3) What is methemoglobinemia? Correct Ans - - Iron in heme is oxidized to Fe3+ (cannot bind oxygen)

• "Fe2 binds O2"
• Classic finding is cyanosis with chocolate-colored blood, hypoxia, and

lethargy

- Causative drugs: Nitrates, Antineoplasatics, local anesthetics (benzocaine,

lidocaine), Sulpha, Antimalarial, Abx (dapsone), metoclopramide, valproate, phenytoin

- Tx: Methylene blue

What is methylene blue used for? Correct Ans - -For metHgb: Reduces Fe3 to Fe2 -For vasoplegia: Inhibits the nitric oxide cGMP pathway, --> vasoconstriction

• 1-2mg/kg over 10 minutes, not to exceed 7mg/kg

Why keep BP up in aortic stenosis Correct Ans - -Heart muscle has to compensate for the stiff AS by getting bigger -Hypotension will decrease coronary perfusion pressure and cause ischemia-- > worsens HF -Need to break the critical Peak systolic gradient of 50mHg

• / 4