Moniters & Machines

Question 1

Fade seen on TOF and TS (tetanus stimulation) with NDNMB or DNMB

Answer 1

NDNMB and phase 2 block.

There is complete disappear of twitch with succinylcholine (DNMB) at once and return of twitches slowly with all 4 twitches with all same amplitude (all same hight, short/intensity felt same with all 4 twitches) this gives TOF ratio of 1.0

With TS causes stimulation for 5 min and you will see fade of twitch amplitude with NDNMB + phase2 block

No fade see with Succinylcholine with TS, after 5 min the twitch would feel less intense after administration but all same amplitude and intensity (no fading of twitch amplitude or intensity)

Question 2

When do you use PTS (post-tetanic Count stimulation)?

Answer 2

For over dosed patients (where all twitches stimulation won’t show twitches) to assess how many minutes you have to wait for first twitch to return on TOF

The more single twitch on PTS, the shorter time to wait.

It should not be used more than every 6 minutes

Question 3

DBS is more sedative in assessing fades than TOF, why?

Answer 3

Double Burst Stimulation (DBS) has 2 twitches where the first analogous to first twitch on TOF and the second twitch is analogous to the first twitch on TOF

So DBS allows better detecting the fade since you compare the feeling of only 2 twitches, where TOF has the 2 twitches between the first and forth which makes it difficult to feel difference and especially if the TOF ratio is 0.6 or more it makes it very impossible (there is study showed only 50% anesthesiologists where able to tell fade differences between TOF twitches at ratio of 0.5)

Question 4

Under GA, what group muscles paralyzed first? And what returns first?

Answer 4

Core body muscles paralayzed and retunes first (diaphragm)followed by peripheral (adductor polices)

GA causes blood flow more to body core like diaphragm first than peripheral muscles, leading to paralysis of core muscles first followed by peripheral

Then after awhile, the blood flow is equals through the body (vasodilation induced GA) and return of muscles depends on which is strongest. So core body recover first (resistance higher) then peripheral

Now if paralytics used without general anesthesia, the peripheral muscles paralyzed first because no blood flow differences and they are smaller with less need blocking enzyme or receptor than core muscles (larger muscles and more receptors or enzymes)

Question 5

3 types of defibrillation, which one has less energy therefore less side effects?

Answer 5

Current base

It is independent of both transthoracic impedance and body weight

3 types of defibrillation

1. Energy based (dependent on selected voltage and transthoracic impedance)
2. Impedance-based (allows selecting transthoracic current based on transthoracic impedance)
3. Current based (fixed dose of current)

There is 2 waves of current-based defibrillation

1. Monophasic direct current (DC)
2. biphasic alternating current (AC) -> treminates arrhythmias more consistently and at lower energy level than Monophasic

Question 6

Defibrillation device related variables. Which is better, large or small electrodes (size)? Anteriolateral or anterioposterior (electrode placement)? Hand-held or patch (electrode type)?

Answer 6

Larger pad -> decreases resistance and increase in current and less myocardial necrosis

Hand held paddle mode effective than self-adhesive patch electrodes

Success rate maybe more with anteriolateral placement of electrodes than anterioposterior placement

Question 7

Patient related variables influencing success of defibrillation?

Answer 7

Avoid delivery during inspiration and non-salt contains gel (they increase transthoracic impedance)

So best to deliver current during expiration, use salt containing gel, and chose large pad electrodes, hand-held pads (not patch electrodes) and no really clear advantage on placement of electrode (but chose anteriolateralor because some data showed success rate higher over posteriolateral).

Question 8

MAP equation

Answer 8

DBP + 1/3 (SBP + DBP)

Question 9

The most accurate measurement by oscillometry is

Answer 9

MAP > SBP > DBP

Question 10

Improper cuff size reads …

Answer 10

Low oscillometric with large cuffs

High oscillometric reads with small cuffs

Proper size is ~ 46% of arm circumference

Question 11

Estimated SBP by pulse palpating

Answer 11

Only carotid -> SBP ~ 60

Carotid + femoral -> SBP ~70

Radial -> ~ 80

Question 12

As you move away from aorta, the A-lone wave become more …

Answer 12

Defined morphology

So aortic wave form would be least defined (one bell curve morphology)

Question 13

How do you know the A-line is optimally dampened?

Answer 13

Flush test and examine the oscillation frequency

Optimal if you see 2-3 oscillation after flush

Over dampened-> 0-1 oscillation

Under dampened -> > 3 oscillations after flush

Question 14

BP cuff or a-line transducer, if placet above the heart, it will give …. pressure reading.

Answer 14

Lower as you you measure above heart

Question 15

Morphology of A-line changes as we age, it would look like?

Answer 15

Higher systolic limb and lower diastolic limb

Explained by decreased arrival wall compliance with aging as artery calcifies

Question 16

Most sensitive leads for detection of ischemia?

Answer 16

Lead 2 + V5 + V6 -> 96%

V5 + V6 -> 90%

Lead 2 + V5 -> 80%

We use V5 & lead 2 even it’s the lowest sensitivity because has better P waveforms

Question 17

What dose vapor pressure depend on? And what’s its relationship?

Answer 17

On temperature

Proportionally related, as temp increases, the vapor pressure increases.

Question 18

What would low fresh gas vs high fresh gas will have effect on vaporizer output of inhaled anesthetics?

Answer 18

Both will decrease the output

With low FG -> causes low turbulent flow inside chamber that will decrease the mobilizations of vapor upwardly to be uptakes by FG -> therefore decreases output

With high FG -> causes incomplete mixing of FG with vapor due to excessive FG velocity -> leads to decrease output

Question 19

How dose N2O in FG flow affect vaporizer output?

Answer 19

It decreases vapor output

Because some of N2O that goes to vapor chamber will solubilizes the volatile-gas -> therefore it will be unavailable to act as carrier with FG -> decreases output

This is transit upon starting N2O and very minor and insignificant clinically effect

Question 20

If you had to fill isoflurane into a different gas chamber intentionally for example if you have no isoflurane Danger 19 vaporizer, which gas chamber would you choose?

Answer 20

Halothane chamber

Because halothane and isoflurane has same partial pressure 243 and 243 torr respectively

And if you had to fill enuflurane to another gas chamber, it would be sevoflurane (their partial pressure are 172 and 160 torr respectively)

However keep in mind that the potency is different for each gas even though they have same partial pressure and so MAC% should be adjusted accordingly to filled gas.

Question 21

What’s Tex 6 vaporizer

Answer 21

It’s Desflurane especial vaporizer

1) electronically heated
2) thermostatically controlled
3) constant temp
4) dual circuit
5) gas-vapor blender
6) electromechanically coupled

Question 22

With altitude, you …. the setting of variable bypass vaporizer

Where the Tec 6 Desflurane, you … the setting in high altitude

Answer 22

For Tec 6 Desflurane -> the concentration dial should be set higher than 1 MAC (increase the dial above sea level, and decrease dial if below sea level)

Where with all other gases that uses variable bypass vaporizer -> the concentration should be set near 1 MAC (you do not change the dial setting)

Question 23

The most soluble gas is

Answer 23

Carbon monoxide

Question 24

Diffusion of gas is … and the rate I’d dependent on …

Answer 24

Is the movement of particles from high to low concentration

Depends on viscosity, size, and temperature

Question 25

Breathing system clarification

Answer 25

Non-rebreathing valve

• open
• semi open (when bag present like NRB mask)

Rebreathing

• closed (like ventilator with CO2 absorbent)
• semi-closed (mapleson circuits)

Open: no reservoir or rebreathing
Semi-open: has reservoir but no rebreathing
Semi-closed: reservoir with partial rebreathing
Closed: reservoir with complete rebreathing.

Question 26

The least amount of FGF required for spontaneous breathing with mapleson system is ….

And the greatest amount of FGF required for SV is …

Answer 26

Mapleson A (also is the best for spontaneous ventilation, A=Alive)

Mapleson D needs highest FGF (best for CV, D=Dead)

Question 27

What other factors needs to be controlled to relay on CVP as the monitor for volume status?

Answer 27

1) Ventricular compliance (intrinsic myocardial state, PVR, valve integrity, rhythm)
2) extrinsic transmural pressure (pericardium, pleura, chest wall, abdomen, patient position, lungs&respiration)
3) Actual intravascular volume (hydrostatic and colloid pressure, capillary leak, venous tone, balance btw vasodilators and catecholamines).

Question 28

CVP waveform

Answer 28

a: RA contraction
c: RV contraction
x: Pulm valve opening
v: VR to RA (increased RA pressure during diastole)
y; Tricuspid opening

Question 29

Abnormal waveforms with

• Afib
• AV dissociation
• TR
• RV ischemia
• Pericarditis

Answer 29

• Afib -> loss A wave
• AV dissociation -> cannon A wave
• TR -> tall c-v wave (no x decent)
• RV ischemia + Pericarditis -> tall A & V waves (M or W configuration)

Question 30

PVR =

Answer 30

80 (PAP -PCWP)/CO

Question 31

what abnormal CVP waveform is seen with LV ischemia

Answer 31

Tall V wave

Question 32

What does PCWP waveform look like?

Answer 32

Similar to CVP but reversed the location

a: LA contraction
c: LV contraction
x: AV opening
v: venous return to LA
y: Mitral opening

Question 33

CVP waveform expected upon swan-Ganz placement

Answer 33

in RA -> looks like cvp
in RV -> large systolic upstroke
in PA -> diastolic stepdown (lower complaint system)
in PCW -> looks like cvp

Question 34

What are the determinants of myocardial O2 demand? and supply?

Answer 34

Demand

1) HR
2) contractility
3) afterload
4) preload (T = pxr/2L)

Supply

1) HR
2) O2 content [CaO2= (Hbx1.39xSO2) + PaO2x0.003]
3) vascular tone
4) CPP (CoPP= AoDBP - LVEDP)

Question 35

contraindication to IABP

Answer 35

1) AR

2) previous aortic or coronary aneurysms

Question 36

IABP function

Answer 36

inflates during diastole:

• pushes proximal blood to coronary -> increase coronary O2 supply
• pushes distal blood to the periphery -> decrease myocardial O2 demand

Question 37

What’s the rate of bacterial colonization of CVL compared to the arterial line? and whats the incidence of infection rate

Answer 37

both have same rate of colonization, but venous line has 5% infection rate compared to arterial

Question 38

Phases of capnographs

Answer 38

Phase 1: exhaled gas from dead space airway (zero CO2, no rise curve)

Phase 2: transition between airway & alveolar (some CO2 rise)

Phase 3: is the alveolar plateau, normally flat

Phase 4: is the end highest point of phase 3 where EtCO2 measured on screen.

Phase 0: downslope, onset of inspiratory.

Question 39

Which is the most commonly employed to detect CO2 in OR

Answer 39

Infrared absorption

The colorimetric analysis which used for emergent intubation, only detects if there is CO2 or not, but dose not measure how much CO2

Question 40

What’s the safest CO2 absorbent? Why?

Answer 40

Ca Hydroxide (Amsorb)

Because it has mainly Ca hydroxide (70%) and added Ca Chloride (0.7%) and 2 other agents which improves hardness and porosity

1) it decreases formation of compound A with Sevo
2) minimal formation of carbon monoxide with Desflurane and Enflurane or isoflurane
3) minimal destruction of inhaled agents

Question 41

Factors increases compound A?

Answer 41

• increasing inspired Sevo %
• increasing absorbent temperature
• decreasing absorbent water content (desiccation)
• decreasing FGF

Question 42

Carbon monoxide toxicity associated which which volatiles? And what are related factors

Answer 42

Desflurane > Enuflurane > isoflurane

This is the case behind “first case on Monday morning”

1) greatest with Barium hydroxide lime absorbent (no longer used)
2) increasing temperature (3aks compound A)
3) decreasing hydration state of absorbent (desiccation)
4) increasing volatile agent and type (Desflurane is most)

Question 43

There are 2 types of relief valves used in scavenging system?

Answer 43

Positive pressure relief valve (PPRV) used for the closed interface scavenger -> prevents barotrauma

Negative pressure relief valve (NPRV) for Active scavenger -> prevent negative pressure pulmonary edema

Question 44

Which of the blood gas analysis not measured instead calculated?

Answer 44

HCO3

Where pH, PaCO2, and O2 are measured

Question 45

What happens when analyzing ABG below 37C?

Answer 45

Cold causes gas to dissolve into liquid state -> decreases PaCO & PaO2 resulting into relative alkalosis

Question 46

4 mechanisms of heat loss are

Answer 46

1) radiation: loss of infrared light (loss of photon )when body surface exposed to environment (not heat loss by contact) MOST SIGNIFICANT
2) convection: heat loss when solid transform to gas (2nd most significant). This loss is proportional to air speed, so bearhugger/drapes and clothes are effective by trapping the warm air near skin. Also explains the heat loss by large skin incision
3) conductive: loss of heat by touching (solid to solid object)
4) evaporation: loss of heat when liquid transform into gas

Question 47

The gold standers to measure core body temperature is

Answer 47

Pulmonary arterial blood by PA catheter.

But other also assess core body are
1) tympanic membrane (close to carotid artery, and artery supplies tympanic membrane approximate hypothalamus temp). Placing probe in external auditory is safer and works well if u cover it.

2) nasopharyngeal approximates hypothalamus
3) distal esophagus (45cm away from nose, makes it close to major vessels in heart)

Question 48

Best methods to prevent hypothermia is

Answer 48

Prewarming 30 min prior induction.

Fluid warmer only prevent hypothermia, won’t actively warm patient.

Question 49

The forced air warming device warms the patient by what heat prevention mechanism

Answer 49

By conVection (not conductive) it warms the air to surface/skin)

Question 50

When N2O tank pressure starts to fall?

Answer 50

When 75% of N2O consumed and 25% left in tank

Since there is 1600 L in tank. When pressure falls, you know there is 400L (25%) of N2O in tank left or less.

Question 51

Vocal cord injury

Fully abducted open vocals ->

Partially addicted vocals ->

Fully adducted vocals —>

Answer 51

Fully abducted open vocals -> bilateral vagus nerve damage

Partially addicted vocals -> bilateral recurrent injury (partially where 2-3 mm open between vocals and that results from unopposed cricothyroid muscle) this results into stridor

Fully adducted vocals —> layngospasm

Question 52

A 33-year-old woman is having a laparoscopic gynecologic procedure. The scavenging system at the back of the anesthesia system has gradually become covered with dust over the course of several months and all of the openings to the atmosphere have become occluded. An active suction system draws scavenged gases out of this system. Thus, active suction is now being applied directly to the ventilator system. What is the primary threat to the patient with this active suction system being applied directly to the ventilatory system?
A. Barotrauma
B. Hypocapnia
C. Negative pressure pulmonary edema
D. Hyperthermia

Answer 52

A is incorrect because a scavenging system with pressure being pushed into it (positive pressure applied to system) could possibly cause barotrauma. But this system has negative pressure applied to it, so barotrauma from “overpressuring the system” will not occur.
B is incorrect because negative pressure applied to the system will likely “pull the bellows flat” and result, if anything, in hypoventilation, which would lead to hypercapnia, rather than hypocapnia.
C is correct because negative pressure applied directly to the ventilatory system can transmit negative pressure directly to the tracheobronchial tree. This is the exact same mechanism as the more common reason for negative pressure pulmonary edema: a patient obstructing post-extubation and making a strong inspiratory effort against a closed glottis. Negative pressure can pull pulmonary edema fluid into the alveoli in both cases.
D is incorrect because a malfunctioning scavenging system will affect respiratory function but will not cause an increase in temperature.

Question 53

A 35-year-old man is struck in the head in a construction accident. Concern is raised, by his fluctuating mental status, that he may have intracranial hypertension. How is this condition defined?
A. An increase in intracranial pressure above 5mm Hg
B. An increase in intracranial pressure above 15mm Hg
C. A decrease in intracranial pressure below 15mm Hg
D. An increase in intracranial pressure above 40mm Hg

Answer 53

Intracranial hypertension (IH) is defined as a sustained rise in intracranial pressure above (ICP) 15 mm Hg (B) which is the threshold. As the brain is located in the rigid, bony skull, compliance is limited. As a result, tiny volume changes cause major increase in ICP. The rise in pressure of the cerebrospinal fluid or a rise in the pressure within the brain itself can lead to ICP. The old terminology for IH was benign intracranial hypertension or pseudo tumor cerebri. Sudden onset IH can be due to severe head injury, stroke or brain abscess while chronic IH is caused by brain tumor, subdural hematoma, meningitis, encephalitis, arteriovenous malformations or sinus venous thrombosis.
An increase in ICP above 40mm Hg (D) represents severe intracranial hypertension. As there is no fall in pressure, the option (C) is incorrect. The normal intracranial pressure is 5-10mm Hg in adults and 3-7 mm Hg in children. A rise in ICP by 5mm Hg (A) is not representative of intracranial hypertension.

Question 54

Which of the following does not contribute to worsening exposure to carbon monoxide with desiccated CO2 absorbent?
A. High concentration of volatile anesthetic
B. High temperatures
C. Small mesh size of CO2 granules
D. Use of desflurane
E. Use of Baralyme

Answer 54

Baralyme use, desflurane use, high temperatures, and high volatile concentrations are all known to contribute to desiccated CO2 absorbent. Mesh size does impact desiccation of absorbent but it primarily affects resistance or “channeling”.

Question 55

After completing a ruptured abdominal aortic aneurysm repair on a 55-year-old male, the team is preparing to transport the extubated patient to the ICU. As the patient is transported from the OR table to the stretcher you place a face mask and connect it to the oxygen e-cylinder. The cylinder pressure reads 400 psi. If you have the flow set to 6 liters per minute, how much time do you have to get from the OR to the ICU before the tank runs empty?

Answer 55

E-cylinders store compressed gases. The color, pressure, and quantity of gas in each cylinder is commonly tested. Oxygen cylinders are green color coded, are fully pressurized at 2000 psi and have approximately 625 liters of gas. The contents of oxygen e-cylinders are easily calculated as a ration of x psi/2000= liters/625.
B is the correct answer. 400 psi/2000 psi = 0.2. 0.2 x 625 liters = 125 liters remain. Divide by 6 liters per minute = 20 minutes of oxygen delivery left at that rate.

Nitrous oxide e-cylinders are blue colored and more difficult to calculate the remaining amount of gas. Full nitrous oxide tanks hold 1590 liters and because their pressure does not fall below 750 until 3/4 of the tank is empty it can be assumed that approximately 400 liters are left once the pressure gauge begins to fall.

Carbon dioxide tanks are gray colored and hold 1590 Liters at a psi of 838.

Air is kept in yellow e-cylinders and hold 625 liters at 1800 psi.

Question 56

During lunch one day your colleague comes over and begins to talk about the workplace hazards of anesthesia and potential exposure to nitrous oxide and volatile anesthetics. The Occupational Safety and Health Administration (OSHA) recommends that nitrous oxide concentration in the OR as waste gas not exceed?

A. 25 parts per million
B. 2 parts per million
C. 225 parts per million
D. 15 parts per million

Answer 56

Exposure to nitrous oxide and volatile anesthetics in the workplace poses health hazards to operating room personnel. Waste gas scavenger systems ensure that the closed circle system circuit clears waste gases out of the OR.
A is the correct answer because OSHA recommends that nitrous oxide concentrations not exceed 25 parts per million (ppm) and volatile anesthetics not exceed 2 ppm. Exposure to nitrous oxide has been shown to put pregnant women at higher risk for spontaneous abortion.
B is incorrect because that is the OSHA recommendation for volatile anesthetics.