Midterm Flashcards
Components of the preop assessment
name and DOB, verify site and procedure, labs, med history, anesthetic history, education, informed consent, H&P (airway exam)
What herbal meds increase bleeding time and when should the patient discontinue it?
garlic, gingko, ginseng- 7 days pre-op
Latex allergies are common in?
patients with spina bifida and multiple surgeries; common to also have allergy to tropical fruits
When should patients stop smoking before surgery and why?
4-8 weeks pre-op (decrease carboxyhemoglobin levels and prevent respiratory complications)- minimum 12 hours before
What does chronic alcoholism vs acute intoxication do in regards to anesthetics?
chronic alcoholism increases resistance to CNS depression, whereas acute intoxication does the opposite
components of airway evaluation
Mallampati (1 is best), thyromental distance 7 cm, intercisor distance 4 cm, good head and neck range of motion, good dentition, neck size
What are the effects of general anesthesia on the respiratory system?
decrease FRC (up to 2 weeks), alters V/Q, inhibits ilia, decreases surfactant, increased sensitivity
What are the high, intermediate, and low scores of STOP BANG?
5-8 high, 3-4 intermediate, 0-2 low
In terms of MET scores, what’s good and bad?
1- bad, 4- good
Cancel surgery if BP is over?
180/110
What antihypertensives should you continue and which ones should you stop?
continue beta blockers, stop ACEI (day of)
How long after an MI should you wait to have surgery?
60 days
What are the considerations of patients with OA, ankylosing spondylitis, and RA?
limited neck mobility, may be on steroids (may need stress dose), may be on NSAIDs/ASA- bleeding
What is an anesthetic consideration for someone with GERD?
may need RSI
What lab is the most accurate reflection of renal reserve?
creatine clearance
When should you delay surgery in regards to hyperkalemia?
over 5.5 (not absolute)
What labs should you check if someone is in renal failure?
K, creat, Hgb
Considerations about diabetics
stiff joint syndrome, may need Reglan (gastroparesis), may give half insulin the day of, try to do surgery in the AM to minimize fasting
What drugs should you use in hyperthyroidism and which ones should you avoid?
use beta blockers, avoid anticholinergics
What can you have within one hour of surgery?
meds with sip of liquid (150 mL for adults, 75 mL kids)
What can you have within two hours of surgery?
clear liquids
What can you have within 4 hours of surgery?
breast milk
What can you have within 6 hours of surery?
infant formula, nonhuman milk, light meal
Describe ASA classifications
1- normal; 2- disease w/o limitations; 3- disease w/ limitations; 4- severe dz with constant threat to life; 5- moribund, minimal chance of survival w/o surgery; 6- brain dead
What does the ASTM do?
makes anesthesia machine regulations about workstation and components
What does the FDA do?
anesthesia machine checkout, standards for gases
What does the DOT do
compressed gas regulations
What does the ICC do?
construction of cylinders
What does the CGA do?
sets safe practices for gas cylinders
What is the pressure in the breathing circuit limited to?
125 cm H20 or 12.5 kPa
What is the psi in each system on the ventilator?
high- 2000 psi; intermediate- 45-55 psi; low- 16 psi
What are the 5 tasks of oxygen?
ventilator driving gas, flush valve, O2 pressure failure alarm, O2 pressure sensor shutoff (failsafe), flowmeters
Describe a free floating valve
prevents gas leak- moves in direction pushed by gas
Describe a ball and spring valve
permits gas flow after concentration made (all or none)
Describe a diaphragm valve
decreases pressure (pressure regulator)
When should you change an O2 tank?
half full -1000 psi
What is the psi and L of an oxygen tank?
2000/ 660 L
What is the psi and L of a nitrous tank?
745 psi / 1590 L
What is the psi and L of an air tank?
200 psi/ 625 L
What is the critical temp of oxygen?
-119 C
What is the critical temp of nitrous?
39.5 C
F to C
5/9(F-32)
C to F
(9/5 x C) + 32
How often do medical cylinders need to be tested, and who sets that regulation?
every 5 years; ICC
Describe the Joule Thompson effect
compressed gas escapes- process is adiabatic and cooling occurs (if cylinder is opened rapidly, temperature increases rapidly- why we “crack” cylinder)
What are the PISS configurations of all 3 cylinders?
air- 1,5
oxygen- 2,5
nitrous- 3,5
What does the free floating valve of the hanger yoke do?
prevents full cylinder or pipeline from emptying into empty cylinder
Do the Bourdon pressure gauges measure absolute or relative pressure?
relative
What does the oxygen pressure failure device do, and what are its limitations?
if PRESSURE drops below 30 psi, 2nd gas turns off- only senses pressure, only prevents problems upstream
What does the oxygen failure alarm do?
alerts to loss of oxygen pressure (<20 psi)- audible whistle
What should you do if you suspect a pipeline crossover?
disconnect pipeline, turn on cylinder, use low flows, conserve O2, manually ventilate, use TIVA
Describe the O2 flush valve
bypasses the vaporizers, delivers 35-75 L/min of oxygen- should use only on expiration
Describe the design of the flowmeters
Thorpe tube- has variable orifice- specific for each gas
Describe laminar flow
parallel, orderly; dependent on viscosity and Pouisueille’s law; Reynolds <2000
Describe turbulent flow
nonorderly; dependent on density and Graham’s law; Reynolds <4000
What changes flow from laminar to turbulent?
change in direction >20 degrees, corrugated tubing, increased velocity
What does the hypoxic mixture prevention device do?
keeps mandatory O2 flow 50-250 ml; limits nitrous to 3x that of O2
what kind of breathing system is the anesthesia machine?
semi-closed
What is the order of efficiency from best to worst of Mapleson circuits for spontaneous ventilation?
ADCB
What is the order of efficiency from best to worst of Mapleson circuits for mechanical ventilation?
DBCA
What is the purpose of the reservoir bag and what is the characteristics of its connector?
prevents excessive pressure from getting to the patient- 22 mm female connector
If you turn the APL clockwise, what are you doing?
increasing limiting pressure
CO2 absorbers are a ? neutralizing a ?
base; acid
How much CO2 is absorbed with NaOH?
26 L per 100 g
What is the product of the first absorber reaction?
carbonic anhydrase
Is the second absorber reaction fast or slow? And what are its products?
fast- water and heat
Is the third absorber reaction fast or slow?
slow
Compare soda lime to calcium hydroxide
soda lime absorbs more CO2 and forms more compound A and CO; whereas CaOH produces less but absorbs less CO2 (only 10.6 L perr 100 g)
What is the mesh size of CO2 absorber granules?
4-8
What is compound A formed from, and what is it toxic to?
sevo; kidneys
What is carbon monoxide formed from?
des, iso, enflurane
How do you reduce the amount of Compound A made?
use at least 2 L/min FGF, lower concentrations of sevo, fresh CO2 absorber
What are some signs of CO2 absorber exhaustion?
hypercarbia, acidosis, inreased RR, SNS discharge, dysrhythmias
What does vapor pressure depend on?
temperature- if you add heat, more molecules enter vapor phase
Difference between flow over and draw over vaporization methods?
flowover- stream passes over liquid; draw over uses patient breath
How do the variable bypass vaporizers compensate for changes in temperature?
bimetallic strip (opens more when cold, closes more when hot)
Which way do the vaporizer knobs turn?
counter clockwise
What prevents using more than 1 agent at a time?
interlock system
What is the Tec 6 heated and pressurized at?
39 degrees and 2 atm/1300 psi
What did we add to the machine that minimizes the risk of incorrect concentrations of gases?
gas analyzer
What would happen if you put sevo in an iso vaporizer?
lower output (and vice versa)
What would happen if you put iso in a halothane vaporizer?
nothing- similar VP
Does the Tec 6 compensate for changes in altitude?
no
What bellows is better?
ascending- shows disconnect
What happens with a leak in the bellows?
increased FiO2, barotrauma
Which drive mechanism is more likely to have FGF decoupling?
piston
How do you calculate TV if your ventilator does not have decoupling and does not compensate for compliance?
(TV+FGF) - compliance
How do you calculate compliance?
compliance x PIP
How do you calculate FGF per breath?
FGF divided by I:E ratio divided by RR
Should you use a cylinder for your driving gas?
no
Describe volume control
delivers preset TV, time initiated
In VC, what do plateau pressure and PIP reflect?
plateau pressure- compliance; PIP- resistance
Describe pressure control
Delivers programmed pressure- TV variable- may need to alter I:E ratio
What ventilation method is good for emergence?
SIMV
What are advantages and disadvantages of the non-diverting gas monitor?
advantages- fast, no scavenging needed; disadvantages- circuit weight, increased DS, needed cleaning, only measured O2 and CO2
Describe diverting gas analyzers
siphons 50-250 ml/min of gas up to main unit- requires zero calibration, but needs scavenging and has a greater difference between PaCO2 and EtCO2
Does infrared analysis measure O2?
no- measures CO, nitrous, and halogenated agents
What part of the machine uses paramagnetic O2 analysis?
O2 analyzer- O2 is the only paramagnetic gas
What should you be able to do with the suction catheter?
occlude and hold at waist height
What are some hazards of suctioning?
hypoxemia (avoid during stage 2), trauma, infection, increased ICP, negative pressure pulmonary edema
Electrical currents usually not perceived if less than…
1 mA
What is the threshold for electrical current with and without skin?
skin- 100 mA; without- 100 microA
Why are ORs ungrounded?
does not allow for completed circuit through which equipment may be grounded
When does the line isolation monitor alarm?
2-5 mA
What could be some causes of hypoxia?
short gas supply, O2 leak, air entrapment
What could be some causes of hypoventilation?
disconnection, supply issues, leaks, increased scavenger suction
What could be some causes of hypercarbia?
absorbent failure, unidirectional valve problem, coaxial leak, increased dead space
What could be some causes of high airway pressure?
spill valve or APL malfunction, plastic left on, O2 flush valve
What could be some causes of anesthetic agent overdose?
tipped vaporizer, transfilled, overfilled, failed interlock
What could be some causes of inadequate anesthetic delivery?
entrapment, faulty vaporizer, empty vaporizer
What is the most important part of the scavenging system?
interface- protects patient from positive or negative pressure from scavenging
In a closed scavenging system, when do the positive and negative P valves open?
positive- 5 cmH2O
negative- -0.25 cmH2O
What should your reservoir bag look like in the scavenging system?
partially filled
What are the allowable trace gas levels?
nitrous- 25 ppm
halogenated agents- 2 ppm
both- nitrous 25/halogenated 0.5
Oxyhemoglobin absorbs more ? light and deoxygenated Hgb absorbs more ?
infrared; red
What is the “law” of pulse oximetry?
Beer Lambert
Is pulse oximetry in real time?
no- 15 second delay
What are some things that could cause a false higher SpO2 reading?
carboxyhemoglobin and methemoglobin
What can cause methemoglobin?
congenital issues or acquired (nitrobenzenes)
What is the treatment of methemoglobinemia?
methylene blue
Hgb has ? x affinity for CO than O2
200
What population has a normal 5-6% level of carboxyhemoglobin?
smokers
What drugs cause a transient decrease in SpO2?
methylene blue, indigo carmine
What is oxygraphy used for?
measure preoxygenation efficiency
What is the normal FiO2 and FeO2
21% and 16%
Describe phases of capnography
1- inspiratory baseline
2- expiratory upstroke
3- expiratory plateau- uneven emptying
4- inspiration
normal alpha and beta angle
100-110; 90
What is the dividing point between the upper and lower airway?
cricoid cartilage
At what cervical levels are the hyoid, thyroid, and cricoid cartilages?
C3; C4-5; C6
What nerves innervate the muscles of the larynx, pharynx, and soft palate?
vagus, glossopharyngeal, and spinal accessory
What innervates all muscles that move the VC, (except for the cricothyroid muscle)?
RLN
What innervates the motor function of the cricothyroid muscle?
external branch of SLN
What innervates the sensory portion of the larynx above the vocal cords?
internal laryngeal nerve (branch of the SLN)
What innervates the sensory portion of the larynx below the vocal cords?
RLN
What are the RLN and SLN branches of?
vagus nerve
What does the R RLN wrap around?
brachiocephalic artery
What does the L RLN wrap around
aorta
Describe RLN and SLN injury
SLN and unilateral RLN damage causes hoarsness, whereas bilateral RLN damage causes stridor
What does the only motor branch of the glossopharyngeal nerve innervate?
stylopharyngeus
What arteries supply blood to larynx?
SLN- branch of superior thyroid artery; RLN- branch of inferior thyroid artery
Which muscles pull the pharynx down?
omohyoid, sternohyoid, sternothyroid
How many cartilagenous rings make up the trachea?
16-20
What are the “false” vocal cords?
vestibular folds
What abducts the vocal cords?
posterior criocoarytenoids
What adducts the vocal cords?
lateral thyroarytenoids
What is the only intrinsic muscle not innervated by the RLN, and what is it innervated by?
cricothyroid- external laryngeal branch of X
What innervates the diaphragm
C3-5- phrenic nerves
What are some signs of correct ETT placement?
bilateral breath sounds and chest rise, positive end tidal CO2, O2 sat, tube condensation, CXR, blood gas
What are some techniques for airway management?
head tilt (leave pillow), jaw thrust, Sellicks (cricoid pressure), RSI
