BASICS Exam 1 Flashcards
what increases and speeds up burning effects
oxygen
what is used in a gas autoclave that cannot tolerate exposure to high temperatures or water vapor
ethylene oxide (EtO)
what are examples of intermediate and low level disinfectants
chlorine based products
phenols
high percentage alcohols
what must you have before choosing anesthetic technique
patient consent
how do propofol and volatile agents decrease blood pressure
by decreasing SVR
what population is emergence delirium more common in
elderly
what is the biggest fear for providers with lasers
eye/retina damage
Igniting fire
why is electrocautery ultra high frequency
prevents damage or electrical interference to neuromuscular and cardio-electric system
what megahertz is electrocautery usually set at
0.1-0.3mHZ
what happens to electrocautery unit if grounding pad isnt plugged in
beeps and wont start
what is caused by 10-20miliamps
let go current
what is caused by 100-300 miliamps
vfib
what is the temperature conversion formula
C=(F-32) x 5/9
F= (C x 1.8) + 32
what is a solute
substance that is dissolved, usually a solid (think drug)
what is a solvent
The substance that dissolves the solute, usually a liquid
what is a solution
solute+solvent
what is the equation for watts
watts=volts x amps (vxi) or I^2 xR
what are volts
electrical pressure
what monitors isolated power to ensure it is isolated from the ground and alarms when it isnt
line isolation monitor
what vital monitoring equipment has the highest incidence of positive test for occult blood
ecg cables
what is the preferred skin prep
chlorhexidine
what skin prep should not be used in neuraxial procedures due to risk of neurotoxicity
chlorhexidine
what monitors both sides of the circuit for equality of current flow and shuts off power if a difference is detected
ground fault interrupter
what should not be used on eye, mucous membranes, ears, or genitals
chlorhexidine
what skin prep should be used for epidurals and neuraxial procedures
povidone iodine
prevention techniques for VAP
-HOB 30-40 degrees
-20cm H2O cuff pressure
-avoid PPI or H2 blocker if possible due to risk of acid suppression therapy enhancing bacterial colonization of aerodigestive tract
what case transmission occurs when same patient serves as the source of the pathogen and the host
within case transmission
how far can a droplet particle spread
3-6 feet
what is the most common complication associated with hospital care
hospital associated infection
what is the single most important practice in reducing transmission of infectious diseases
hand hygiene
what are examples of airborne diseases
measels, TB, varicella, shingles, smallpox
how are bacteria/viruses aerolized
sneezing
coughing
tracheal suctioning
bronchoscopy
intubation/extubation
what are diseases with droplet precautions
flu
pertussis
mumps
rhinovirus
what is the absence of potentially pathogenic microorganisms
asepsis
what are practices to minimize contamination by pathogens and prevent their spread
aseptic technique
what is a device that enters sterile tissue or vascular system
critical device
what is the absence of all microbial life
sterile
what is an animate or inanimate object that carries a pathogen and transmits the pathogen from source to host
vector
what are the most common HAI
staph
eterococci
enterobacteriaceae
when should you perform hand hygiene
before/after patient contact
before aseptic tasks
after exposure to body fluids
after contact with pt surroundings
what kind of device comes in contact with mucous membranes or nonintact skin
semi critical device
what is the most common source of pathogen transmitted through contact
an infected patient
should you re-use the same syringe on the same patient to draw up a second time from a multi dose vial
no
when should you discard a multi use vial
when empty or at the end of the procedure
what is an example of a semicritical device
laryngoscope
how big is a droplet particle
greater than 5micrometers in diameter
what case transmission occurs when infected patient serves as the source of the pathogen spread to other patients
between case transmission
what operates by generating high frequency currents passing through tissues and heat is then created by resistance of tissues to current flow
electrocautery
what is a small hand held battery operated device using electrical current to heat a metal wire
electrocautery
what is the sum of the forces that oppose electron movement in an AC circuit
impendance
what shock is delivered to an individual with an external conduit in direct contact with the heart
microshock
what does a capacitor have the ability to do
store charge
what is the equation for MAP
(systolic + (2xdiastolic))/3
how many surgical fires are in the US annually
550-650
has there been a decrease in fire risk with advent of halogenated anesthetics
no
what is the fire triad
oxidizers
ignition/heat
fuel
what are oxidizers
oxygen and nitrous oxide
what are sources of fuel
drapes
gloves
aerosols
hair
alcohol prep
skin prep
gowns
what is the most common type on on-patient fires
head and neck
why are head and neck the most common type on on patient fires
open source of oxygen and drapes
is it recommended to run open oxygen during head and face MAC
no
what is the most common type of in-patient fires
airway
what should be done with ET tube to prevent airway fires
use cuffed ET tubes
what should oxygen setting be below to prevent airway/surgical fires if possible
25% or less
how long should oxygen be turned off prior to electrocautery
1 min
what is the benefit of tenting drapes
adding volume underneath to introduce air as a buffer
what can be put in drapes to pull oxygen out
suction
how long should alcohol antiseptic be allowed to dry before electrocautery
4-5 min
what is special about a laser ETT
has 2 cuffs
one filled with methylene blue solution so surgeon knows if he hit the cuff
why can cuffed ETT now be used for pediatrics more often
high volume, low pressure cuffs
what are the steps to take during an in patient fire
disconnect circuit
turn off gas
do no ventilate
extubate
irrigate with saline
look for left over material
re-establish airway
why should you not ventilate before extubating during a fire
do not want to add positive pressure to fire to create blow torch effect
what should be poured down the airway to extinguish the fire
normal saline
what should be considered after an airway fire
bronchoscopy and ICU
steps to take for an on patient fire
turn off all gases,
remove burning material
extinguish fire
assess patient/remove from harm
what is Ohms law
V=IR
(volatge= amps x resistance)
it is easier to see that current (the rate at which the electrical charge flows through a circuit) is proportional to voltage (how hard energy is pushed through the circuit) and inversely proportional to resistance (how strongly the circuit resists the movement of electrical charge). To return to the example of the car, pushing with more force is expected to increase the speed of the car, while someone in the driver’s seat pressing the brakes (adding resistance to rolling) is expected to slow the car or require more force to maintain the same speed
what is I in Ohm’s Law
amps
what is the r in Ohms law
resistance/ohms
what is the v in Ohms law
volts
what is another word for amps
current
number of electrons flowing through
what is another formula for Ohms law
R= V/I
what are electrical diagrams used for
schematically represent electrical circuits
when does a circuit exist
when charge is able to flow around a closed path
what is an example of a direct current
battery
what is a direct current
only flows in one direction
what is an alternating current
current periodically changes direction
what is an example of an alternating current
wall outlet
what is a circuit with only one path that can be taken by the current
series circuit
how is voltage in series of batteries calculated
add voltage of each battery together
what is equivalent resistances the sum of
individual resistances
what doubles in a parallel circuit
capacity
is voltage added together in a parallel circuit
no
what is an example of a parallel circuit
the electrical system in a house
what is an advantage of a parallel circuit
you can connect loads that need different currents to the same parallel circuit
why do houses run on parallel circuits
not every individual appliance needs to be turned on to complete the circuit
what is not good at conducting electricity
insulator
what is good at conducting electricity
conductor
what is in the middle of a conductor and an insulator
semiconductor
what are semiconductors commonly used in
computers
what is a common semiconductor
silicon
what are impurities added to semiconductors to control conductivity called
doping agents
what is an electrical shock
sensation/muscular spasm caused by current passing through body
what prevents a bigger electrical shock in a 3 pronged plug in
grounding wire- circular part
does every circuit have potential to shock
yes
what is a large current resulting in serious injury or death
macroshock
what is a macro shock measured in
miliamps
what is a minor current delivered directly to the heart
microshock
what can +100 microamps cause through a direct line t heart
vfib
what trips and cuts power to avoid electrocution
ground fall interrupter
what is a typical limit for a line isolation monitor
2-5 miliamps
how many miliamps is needed for human perception
1
what monitor determines degree of isolation between 2 power wires and ground wire
line isolation wire
what alarms when too much high current is going through the ground wire
line isolation monitor
does a line isolation monitor interrupt electricity
no
what is placed on the patient to ground the electrical current from electrocautery
grounding pad with gel
what might have lower resistance than grounding pad on a patient
metal of any kind
what can cause serious burns with grounding pad
inadequate contact
what are the types of non ionizing radiation
microwave
infrared
visible
UV lights
what is caused by non ionizing radiation
sunburns
skin cancer
what type of radiation results in rotation, vibration, or excitation of electrons with atoms
non ionizing
is ionizing or non ionizing radiation more destructive
ionizing
what type of radiation can break covalent bonds
ionizing radiation
what are examples of ionizing radiation
gamma rays
xrays
alpha/beta particles
what type of radiation has sufficient energy per photon to remove electrons from atoms
ionizing radiation
what type of radiation has lower energy photons that can be absorbed thus increasing internal energy
non ionizing
what should you take into account when protecting yourself from radiation
time
distance
shielding
what tissues are more rapidly affected by radiation
gonads
bone marrow
lungs
thyroid
what is the inverse square law equation
Intenssity1/Intensity 2= distance 2/distance 1
intensity= 1/distance ^2
how many rads would you receive at 2 meters if your receive 4 rads per meter
rads= 4( 1^2/2^2)=1
what is the optimal minimum distance for radiation
6 feet
what creates a fire risk especially in airways
lasers
what should be worn by patient and staff during lasers
goggles or wet 4x4s
who sets the standards for laser safety
ANSI
what technique is the patient completely unaware
general
what type of anesthesia is difficult for patients with anxiety, shortness of breath, and sitting still
MAC
what are advantages of regional anesthesia
quicker recovery
pain free
no narcotics
what is mass
the amount of matter in an object
what is the measure of electrical power
watts
what law states for every action there is an equal and opposite reaction
Newtons 3rd law
how is mass different from weight
weight is gravitational force exerted on an object by a much larger object
what is an example of force
push or pull of syringe
larger force produces more acceleration
what is another equation for MAP
(CO x SVR )+ CVP
what is the force required to move 1g of weight 1 cm per second
dyne
what unit is force measured in the body
dynes
what is normal SVR
900-1200 dynes/sec/cm^-5
what is newtons first law
an object at rest or moving at a constant speed in a straight line will continue in that state until acted on by an external force
Newtons 2nd law
force = mass x acceleration
what explains the behavior of gases, liquids and solids
kinetic molecular theory
does visible light or other electromagnetic radiation have mass
no
what is the resistance of an object to acceleration
mass
how do you re-arrange newtons 2nd law to calculate mass
mass= force/acceleration
mass in kg
force in newtons
what is the force per unit area
pressure
what is the equation for pressure
force/area
how can pressure be increased
increased applied force
decrease area over force is applied
how can pressure be decreased
decrease applied force
increase the area over which the force is applied
what is the standard unit for measuring pressure
pascal
what is the equation for pascal
102g/1sqmeter
what are the anesthesia measures of pressure
psi= pounds per square inch
mmHg
do gas molecules have volume
no
when do gas molecules exert force on each other
when they collide
what does the temperature of a gas depend on
average kinetic energy
in kinetic energy, what does more molecules in a system lead to
more transfer of energy
what must all calculations involving gas temperatures include
Kelvin
what is the formula for celsius to kelvin
Kelvin= c+ 273
what is the formula from Fahrenheit to kelvin
kelvin= ({f-32}/1.8) + 273
what measures the pressure difference between the pressure exerted by the gas and the atmospheric pressure
bourdon gauge
its a type of aneroid gauge
what happens when gas at pressure above atmospheric pressure enters coiled tube
tube slightly uncoils, causing pointer to move over a numerical scale
what needs to be exceeded before the bourdon gauge will uncoil
atmospheric pressure
what measures absolute or actual pressure
barometers
what is the pressure of a system above or below atmospheric pressure
gauge pressure
what is the equation for total pressure
atmospheric pressure + gauge pressure
what is the formula for gauge pressure
absolute pressure - atmospheric pressure
what is the pressure inside a tank at 0 psi
atmospheric pressure 14.7 psi
what is quickly affected by temperature change
gas
behaviors of gases
-no definite boundary
-mix freely with each other though not attracted
-low density
-large spaces between molecules
-readily compressible
-exert pressure equally on all sides
gas diffuses based on ….
molecular weight and viscosity
what influences the pressure exerted by gas
kinetic energy and number of molecules
do gases move based on osmotic pressure
no, move regardless of concentration
how does gas exert pressure on a molecule
same on all sides
what are adiabatic changes
the rapid expansion or compression of gas without equilibrium of energy with the surrounding environment
rapid gas expansion vs rapid gas compression results in
expansion= decrease in temp
compression = increase in tempt
what happens when gas is compressed quickly
-intensifies kinetic energy
-does not allow energy to dissipate
-temp rises proportionally to decreased volume
what happens in the energy concentration effect
Compressing a gas quickly increases temp
Joule-Thompson effect
escape of gas cylinder at high flow causes frost to accumulate on the cylinder outlet
what happens to the energy content of the gas during the Joule-Thompson effect
remains constant, temp will change
what are the two adiabatic changes
Joule-Thompson effect
energy concentration effect
name the gas pressure units
torr
mmHg
atm
pascal
physical properties of gas
pressure
volume
temperature
amount in moles (n)
what is the gas and the kinetic theory
gas particles are so far apart and moving so fast that their van der waals attractions are unimportant due to limited effect
what is gas always compared to
STP, standard temp and pressure
what is standard temp
0 degree C
273K
kinetic molecular theory
-molecules have no volume
-gas exert no force unless they collide
-gas particle collisions don not decrease the energy in the system
-molecules of gas are in constant random motion
-temp of gas depends on its average kinetic energy
what is standard pressure
760 mmHg
1 atm
1 g molecular weight (1 mole) =
22.4L in a flexible container
what is avagadros law equations
N1/V1=N2/V2
what is avagadros law
equal volumes of gases under the same conditions of pressure and temperature contain the same number of molecules
1 mole =
6.023x10^23 molecules
aka Avogadros number
avogadros hypothesis
one mole of any gas at standard temp(0 C) and standard pressure (1 atm) occupies 22.4L
what are the three variables that characterize an ideal gas behavior
absolute pressure
temp
volume
ideal gas law equation
PV=nRT
P=pressure
V=volume
n=number of moles
R= 0.0821
T= temp in kelvin
what is the constant number that is the same for all gases
0.0821
ideal gas laws demonstrate a relationship between?
temp
pressure
volume
what are the ideal gas laws
Boyles
Charles
Gay-Lussacs
equation for Boyles Law
P1V1=P2V2
what does boyles law state
volume increases pressure decreases
give an example of boyles law in anesthesia
squeezing the ambu bag increases pressure on bag and decreases volume of the bag
what increases and decreases during inspiration
volume increases
intrapulmonary pressure decreases
what increases and decreases during expiration
volume decreases
intrapulmonary pressure increases
how long will it take a cylinder to empty with 1100psi and flow of 5L/m
tank=50% full
50% of 660=330L
330l/5l/m=66min
how many liters does a full O2 E cylinder hold
660L
how much psi is a full O2 e cylinder
2000psi
Charles Law equation
V1T2=V2T1
what is charles law
Volume increase temp increase
volume varies directly with temperature when at constant pressure
give an example of charles law
ETT cuff expanding when sterilized in an autoclave
what happens in charles law
temp increases gas expands increasing the volume
temp increases volume increases
Gay-Lussacs equation
P1/T1=P2/T2
Gay-Lussacs Law
at a constant volume, pressure of a gas is proportional to its absolute temperature
as temp increases, pressure increases
give an example of Gay-Lussacs Law
tires deflating in the cold and inflates more in the warmth
For each 1 degree of celsius a gas increases, the pressure increases by?
1/273
what can cause an oxygen cylinder to explode
extreme increase in temp
triangle theory to remembering gas laws
Can These Guys Possibly Be Violinists
combined gas law equation
P1V1T2=P2V2T1
process of converting solids to liquids or liquids to vapors
evaporation
what is vaporization
its what happens when further addition of heat beyond boiling point is added to the system
what is boiling point
the temperature at which bulk of liquid is converted to vapor
what is vapor pressure a function of?
temperature
it will increase vapor pressure of a liquid
what is vapor pressure
vapor that accumulates in a closed container
what are the units of standard pressure
1 atm
14.7 psi
760 torr
760mmHg
1.013x10^5n/m2 (same as pascals)
when does a liquid reach its boiling point
when the vapor pressure equals the external pressure
at 1 atm, when will water boil in degrees celcius
100 C
what happens when boiling point increases
vapor pressure decreases
when vapor pressure increases
boiling point decreases
if atmospheric pressure increases what happens to the boiling point
increases
what is saturated vapor pressure
the number of molecules returning to liquid phase is equal to the number of molecules converting into gas phase
what is the energy required to boil a liquid
heat of vaporization
that is the temperature where vapor pressure of substance equals 1 atm
boiling point
what is critical pressure
pressure at which a vapor can be forced into a solid state
what is critical temp
the temp at and above which vapor of substance cannot be liquified no matter how much pressure is applied
whats the critical temp of nitrous oxide
36 c
critical temp of O2
-119C
what happens when a liquid reaches it critical temp
it turns into a gas
properties of general gas laws
-expand easily
-readily compressed
-high velocity
-weak intermolecular forces
-high degree of random motion
What is Daltons Law of partial pressure
total pressure = sum of all the partial pressures of the individual gases
what is 1 atm in weight
14.7lb/in^2
Grahams Law of Diffusion
diffusion of gases through membranes/solutions is inversely proportional to the square root of its molecular weight
Henrys Law
solubility in a liquid is directly proportional to pressure
Temp is constant
In Henrys law, what does increasing the partial pressure of a gas above a liquid do
increases the amount of gas that dissolves in the liquid
example of Henrys Law
increasing FiO2 increases arterial PaO2
what is O2 solubility coefficient
0.003ml/dl/mmHg
CO2’s solubility coefficient
0.067mL/dL/mmHg
How much O2 is dissolved in arterial blood when PaO2 is 300mg?
0.003x300mmHg= 0.9ml O2/100ml blood
how much O2 should be dissolved in arterial blood when FiO2 is 40%
40% x 5 = 200mmHg
200mmHgx 0.003= 0.6ml O2/ 100ml blood
can estimate PaO2 if given FiO2 by multiplying 5 by %
how much faster does CO2 dissolve across alveolar capillary membrane
20x faster because its 20x more soluble in fluid
what law explains the measurement of functional residual capacity by body plethysmography?
Boyles Law
what is an endothermic reaction
a reaction that uses energy
does pressure have influence on solubility of solids/liquids
NO
what happens to the solubility of gas in a liquid as the temperature increases
dissolving decreases aka solubility decreases
why does less gas dissolve in liquid at a higher temperature
kinetic energy allows gas molecules to escape from dissolving
what happens to solubility of a gas in a liquid as temperature decreases
energy is slowed
more gas dissolves into the liquid
How does hypothermia affect anesthetic gas and the patient
slower emergence bc of increased solubility of gas in the blood
What are the 5 factors of fluid permeable through a tissue
-concentration gradient
-area of the tissue
-fluid tissue solubility
-membrane thickness
-molecular weight
what is diffusion inversely proportional to
molecular weight of gas
membrane thickness
diffusion is directly proportional to
pressure gradient (membrane area)
concentration gradient
solubility
what is the second gas effect
using N2O with isoflurane speeds the uptake of isoflurane in the blood
explained by Ficks Law, as N2O leaves alveolar sack it decreases the area of the sac and increases diffusion
what is diffusion hypoxia
when turning off nitrous oxide, N2O escapes into lungs faster than O2
turn on O2 to correct
When do we avoid N2O
pneumothorax
bowel obstruction
middle ear/sinus disease
N2O will diffuse and expand in spaces
How much more soluble is N2O than nitrogen
35x more
diffuses in and out more rapidly
what are liquids and gases considered
fluids
what forces are associated with fluids
gravity
pressure
friction
how are fluids defined
response to stress
-resistant to compression= liquid
-compressible and expandable= gas
units for flow rate
m^3/s
cubic meters per second
what is laminar flow
all molecules move in an orderly, parallel path through the tube
what kind of flow is in the terminal bronchioles (smallest airways)
true luminar flow
reynolds equation
Re=velocity x density x diameter / viscosity
Re= v x p x d / N
v= velocity
d= large vessel diameter
p=density
n =viscosity
turbulent flow
chaotic flow with eddie currents
Reynolds number <2100 is
laminar flow
Reynolds number > 4000 is
turbulent flow
what is turbulent flow determined by
density
how does flow rate relate to diameter
as the diameter of a tube decreases, the speed of the fluid flowing through it increases
what kind of gas helps an upper airway obstruction
low density gas mix such as helium oxygen
decrease turbulent flow and make it more laminar
where does turbulent flow occur in the airway
trachea
upper bronchi
upper bronchioles
characteristics of turbulent flow
increased velocity
increased volume per unit time
increased energy required
where does diffusion occur in the lungs
terminal and respiratory bronchioles
what flow predominates in coughing, phonation, and periods of peak flow
turbulent flow
Poiseulles Law states
velocity of a liquid flowing through a capillary is directly proportional to the pressure of the liquid and the fourth power of the radius of the capillary
velocity of a fluid through a capillary is inversely proportional to the viscosity and the length of capillary
what does Poiseulles Law describe and what affects it most
laminar flow
radius
what 4 things determine volume over time according to Poisuelles Law
- pressure difference
- viscosity
- length of tube
- radius of tube (to the 4th power)
Poisuelle’s equation
Q= flow rate
an example of Poisuelle’s Law
16gauge infuses faster than 22gauge IV
what is flow directly proportional to
hydrostatic pressure gradient
what is flow rate inversely proportional to
fluid viscosity
length of tube
what is laminar flow determined by
viscosity
how is flow affected in polycythemic patients vs anemic patients
polycythemic have high blood viscosity so flow through vessels is reduced
anemic have decreased blood viscosity=greater flow
what are three factors that affect resistance
volume of fluid
tube length
internal diameter of tube
Bernoullis Theorem
pressure of a fluid flowing through a tube is least at the point of greatest constriction and speed is the greatest
the widest portion of is where the pressure is the greatest and speed is least
what is the Coanda effect
fluid tends to flow in a pattern that follows a curved surface surface after emerging from a constricted area
can create preferential flow in the direction of the curve and drags the other fluid with it
clinical example of the coanda effect
unequal gas distribution in the lungs past where there is a kink in the equipment
also bronchospasm leads to unequal gas flow distribution
Law of Laplace equation
T=Pr
t=wall tension
p=pressure
r= radius
Law of Laplace definition
as structure expands (increases the radius) the tension (force) in the wall increases
tension is proportional to radius
clinical example of Law of Laplace
aortic aneurysm
the larger the radius the higher the tension and more likely the vessel will rupture
threshold aneurysm 5cm
Frank Starling Law
the greater the filling the greater the tension in the left ventricle
increase in diastolic volume= increase in stroke volume
Law of Laplace equation sphere
p=2T/r
p=pressure
t=surface tension
r=radius
what is surfactant
soapy substance that lowers surface tension in alveoli and prevents laplace law effects
equilibriates surface tension among different sized alveoli and stabilizes alveoli pressures
why does pressure within the alveolus not change
because tension also increases
what is the unit for work and energy
Joule
what is a joule a combination of
newton and the meter
what is kinetic energy
the energy a mass has by virtue of being in motion
ways to prevent heat loss
fluid warmers
bair hugger
humidify inspired gas
blankets
what is energy
the capacity to do work
law of energy conservation
energy is neither created or destroyed, only converted into other kinds of energy
how many joules in one thermochemical calorie
4.184 J
how many joules in a kilocalorie
1000 cal in kilocalorie
so 4184 joules
zeroth law of thermodynamics
if A and B are the same temp, and A and C are the same temp then B and C will have no heat flow between them
1st law of thermodynamics
the change in internal energy is equal to the sum of heat that caused energy to leave the system
2nd law of thermodynamics
heat spontaneously flows from hot body to cold body when two bodies are in thermal contact
what is proportional to the average kinetic energy of particles in a sample of gas
temperature
define heat capacity
the amount of heat/energy required to raise of lower temp of an object
what is specific heat
the heat required to raise the temperature of a unit of mass of a given substance by a given amount
define conduction ( in regards to heat)
heat transfer via physically touching an object
ex: pt touching OR table
define convection
heat transferred to moving air molecules
ex: air moving around OR
define radiation heat loss
heat transfer via infrared electromagnetic wavelength from a warmer to cooler area
define evaporation heat loss
heat transfer to a liquid causing it to change to a gas
ex: expiration
what is cause of most heat loss in OR
radiation and convection
what is percent transmittance
the percentage of light that passes through a sample
what does a spectrometer measure
the number of photons per second per unit area in the light
What 3 factors affect how much light is absorbed in the Lambert-Beers Law
-greater concentration of analyte increases chance photon will encounter molecule to interact
-increasing distance the light beam travels increases the chance photon will encounter molecule with which to interact
-absorptivity describes likelihood photon will excite molecule, constant for each substance at given wavelength
Lambert Beer’s law describes the function of what
pulse oximeter
explain how pulse ox works
oxy hgb= absorbs infrared lgiht
doxy hgb= absorbs more red light
computer calculates % of oxy hgb based on the ratio of the two light wavelengths received by the detector
how many nanometers is red light
650
what is the color, psi, capacity, and weight of N2O
blue
750psi
1590
8.8kg
how many nanometers is the infrared diode (oxy)
950
how many nanometers is the red light diode (deoxy)
650
how long will 1600 psi O2 last if you deliver at a 2L and 3L
1600/2000= 80
80% of 660= 528
528/2L= 264 min
528/3L=176 min
what is the service pressure and capacity of oxygen
2000 psi
660L
what is the service pressure and capacity of nitrous oxide
~750 psi
1590L
what is the service pressure and capacity of air
1900 psi
625L
why are surgical patients at risk for positioning injuries
insensible to pain
unable to reposition
anesthesia blunts compensatory mechanisms
what is inadequate tissue perfusion caused by
Poor arterial blood supply and venous drainage
what were most common injuries due to positioning by order of frequency
ulnar neuropathy
brachial plexus injuries
ulnar have no mechanism of injury
what patient population reports/claims more injuries
men
what is a key in preventing nerve damage
thorough preoperative history
what are some other ways of preventing nerve damage
place patient in position they would tolerate if awake
pad pressure points
head/neck neutral
reassess throughout the case
when are nerve injuries more common in regards to length of time
surgery greater than 2 hrs
what are risk factors for nerve damage in positioning
asa>2
obese
low BMI
malnourishment
pre-existing neuropathy
what is imperative in pre-existing neuropathies
documentation of existing neuropathy
what are some conditions associated with pre existing neuropathies
HTN
CHF
HYPOtension
tobacco use
DM
ETOH dependency
liver disease
limited joint mobility
carpal tunnel
dough crush syndrome
radiculopathies
who should move the patient from stretcher to OR bed
the patient
what is a common complication in post op often reattributed to positioning and what causes increased risk
post op back pain
long duration of surgery
use of muscle relaxants: muscle relaxation and loss of lordosis leads to stretching of ligaments
how can you decrease post op back pain
position with knees slightly flexed
knees supported with pillow
do not cross feet
what do general anesthesia, NMB, and PPV interfere with
venous return
arterial tone
autoregulation
what position minimizes respiratory compromise but can cause CV compromise
sitting
what positions interferes with venous return and compromises functional residual capacity
lateral and prone
what is stretched or compressed causing neurovascular compromise and what can this lead to
intraneural vasa nervosum (blood supply to the nerve)
nerve ischemia
when is there a higher risk of neurovascular compromise
-when nerve has long superficial course between two fixed points
-small focused areas
-longer duration of compression
what are small focused areas neurovascular compression occur
heels and occiput
pressure is concentrated
how long can compression occur before numbness
20 minutes average
what is neurovascular compromise
compression of a nerve between internal structure and rigid objects
what can increase the risk of neurovascular compromise
tissue edema (potentially from excessive crystalloids)
what are major causes of acute peripheral nerve injury
damaged axon or myelin sheath causing dysfunctional nerve
-mechanical pressure injury
what does external compression first effect in the nerve
myelin sheath causing slow conduction
if severe enough from conduction block
what is it called when the underlying axon is injured
frame conduction block
how is nerve damage calculated
amount of pressure and amount of time
even high pressure and short time can cause large damage
example of a common mechanical compression injury
carpal tunnel
tourniquet paralysis
hematoma
cast
prolonged immobilization
when does a stretch injury occur
connective tissue of nerves stretch 10-20%
this happens before structural damage
why are stretch injuries significant in nerves
there can be severe lesions disrupting the axon
how can you avoid stretch injuries
abduct arms <90
gently flex hips and knees
maintain cervical spine neutrality
what are pressure points
parts of the body that are more prone to developing ischemia
give examples of pressure point areas
ears
scapula
occiput
elbows
hips
knees
heels
has pressure point padding shown to reduce peripheral neuropathy in the OR
NO
when moving an intubated patient, how should head and neck be positioned
neutral to prevent stretch injury
how can you prevent ETT migration/extubation
disconnect from vent
hold ETT
ALWAYS RECHECK BREATH SOUNDS especially when moving lateral or prone
what does supine positioning decrease/ increase
decrease FRC
increases preload
what is another way to describe V/Q mismatch
when closing capacity exceeds FRC -> hypoxemia
what is v/q mismatch
defect in lung ventilation/perfusion ratio
-lung receives oxygen but no blood, or receives blood but no oxygen
-leads to hypoxemia usually from a blockage
who is at increased risk for decreased FRC while supine
elderly (higher closing capacity)
obese and pregnant (already have reduced FRC)
how do you mitigate decreased FRC while supine
peep
what other illness can contribute to intolerance of supine positioning
CHF
respiratory dysfunction
how can supine affect women greater than 20 weeks
inferior vena cava/aorta compression by fetus which lowers cardiac output
tilt the table or wedge under right hip
what can reduce preload in supine patient
obesity
abdominal tumor
pregnancy
how does going from standing to supine effect a healthy patient
increases venous return and thus increases stroke volume
what can happen to occiput if not padded properly
pressure alopecia
what nerves can be damaged with hyperextension of knee
tibial/peroneal
when arms are on arm boards, how far can they be abducted
less than 90 degrees
what are benefits of Trendelenburg position
increases venous return/cvp
prevents air embolism
facilitates cannulation of IJ central line
negatives to Trendelenburg position
decreases FRC and pulmonary compliance
increases facial/laryngeal edema
what may be a complication of positioning with ETT
caudad (moving to posterior end) movement= endobrachial intubation
what does cephalad movement of diaphragm cause when supine
decreases in FRC
what complications do trendelenburg predispose patient to
atelectasis and decreased compliance= may need higher pressure to achieve adequate tidal volume
what may result from high peak inspiratory pressures
barotrauma
what increases risk of brachial plexus injury in trendelenburg
shoulder braces- not recommended
-use antislide mat or bean bag
what should PIP be kept below in trendelenburg and what is adjusted to achieve this goal
40
tidal volume and rate
how can trendelenburg exacerbate CHF
increases venous return which increases preload
what are pros and cons of reverse trendelenburg
pro: increases FRC and lung compliance (monitor lung volumes)
cons: hypotension, reduced perfusion pressure to brain
how can you assure there is no ulnar nerve compression
palpate the ulnar groove
supinate slightly and slightly flex to prevent
how can neuropathies arise in positioning
compression
ischemia
excessive stretch
what position puts most pressure on ulnar nerve
pronation
pressure increases as abduction degree increases
what can tucking at the arms at the sides lead to if hands are flexed
carpal tunnel
-hands should be in neutral position
-maintain thumbs upright
can also lead to ulnar nerve compression
what can lead to radial nerve damage
improper arm board depth
arm board lower than the table
IV sticks
where is radial nerve prone to compression
posterior surface of humerus
can also stretch brachial plexus
what are signs of radial nerve damage
wrist drop
inability to abduct thumb
inability to extend hand/forearm
loss of sensation
what is a sign of complete plexus damage
entire limb is num and flaccid
what are signs of brachial plexus injury
shoulder pain
tenderness over supraclavicular area
may be noticed POD1 or several days post op
how can brachial plexus injuries be limited
limit arm abduction to <90d
avoid external rotation and posterior displacement of arm
head in neutral position or moved toward abducted arm
what are the nerve roots injured in brachial paralysis
C5 C6 C7
what is erbs palsy
internal rotation of arm
extension of forearm
pronation of hand
C5-C7 injury
which nerve roots are rarely affected in brachial plexus injuries and what happens when they are
C8 and T1
Klumpke paralysis=loss of finger flexion
paralysis of hand
horners syndrome
when can median nerve injury occur
carpal tunnel
what is carpal tunnel characterized by
inability to abduct thumb
inability to flex distal phalax of 2nd finger
decreased sensation of lateral 3 fingers
what nerve is most commonly injured and why
ulnar nerve
superficial path along medial epicondyle of humerus
what are direct and indirect trauma of ulnar nerve
direct: compression against OR table
indirect: nerve is stretched around medial epicondyle
signs of ulnar nerve damage
decreased sensation of medial 1.5 fingers
decreased ability to grip
inability to adduct thumb
claw hand
what are signs of median nerve damage
inability to oppose thumb- ape/benediction hand thumb muscle atrophy
what are pressure points for the prone position
head
ears
eyes
nose
face
penis
testicles
breast
hips
knees
chin
mouth
what needs to be prevented with the head/neck in the prone position
excessive flexion/extension
2 fingers between neck and chin
complications for prone
edema
post op vision loss
retinal ischemia from eye pressure
ischemic optic neuropathy-avoid trendelenburg, maintain arterial BP
what can be obstructed in prone position
external jugular veins
what would you give to help secretions while prone
robinol 0.2mg, give before case starts
how to protect eyes while prone
lacrilube and tape
NO PADDING
what can happen to the vena cava during prone
compression leading to decreased preload
increased surgical bleeding and paravertebral pressure
how does prone affect FRC
increase it if no pressure on abdomen
what is functional residual capacity (FRC)
volume of air in lungs after expiration
pro and con of kneeling position
pro: decreases surgical blood loss for spine surgery
con: increases venous pooling in lower extremities, increases risk of air embolism
what is lateral decubitus
position that refers to the side of the body which comes into contact with the OR table
what can cause hypoxemia in the lateral decubitus position
positive pressure
what happens in lateral decubitus position with nonspontaneous ventilation
perfusion greater in dependent and ventilation greater in independent lung
VQ mismatch
what are considerations for removing pressure in lateral decubitus position
remove pressure from humerus
palpate radial artery pulse
put axillary roll below axilla to support rib cage
what nerves most commonly damaged in lateral decubitus
radial and common peroneal nerve
how can you protect peroneal nerve and saphenous nerve while in lateral decubitus
saphenous: pillow between legs
peroneal: pillow underneath dependent leg
what can cause hypotension in beach chair position
anesthetic blunts baroreceptor response and may decrease SVR
sit up slowly
how much lower is BP in the brain than in the arms
15-20mmHg
potential complication of beach chair position
venous air embolism due to negative pressure at surgical site
what is a risk of sitting position
air embolism due to entrained air during spontaneous respiration
how can you detect venous air embolism
capnography
precordial dopplar listening for mill wheel
TEE
treatment for venous air embolism
flood surgical site with saline
withdraw air from CVP (doesnt usually work)
Left lateral decubitus trendelenburg
where do you zero art line to measure brain perfusion
tragus
conversion factor for brain map vs arm map
1cm rise= 0.75 mmHg drop in MAP
so if brain is 20cm higher than arm, 15mmHg drop
complications of sitting position
blood pooling in lower extremities
decreased vent preload
empty heart
hypotension
decreased end diastolic volume
what can happen when epi is mixed in a regional block in sitting
epi increases sympathetic tone/myocardial contractility can cause body to reflexively decrease HR and BP
complication of lithotomy from central blood volume
pulmonary edema
most common nerve injury in lithotomy
peroneal nerve from candy cane stirrups
footdrop, sensory loss to sole of foot
what can lithotomy position exacerbate
heart and respiratory disease
nerves that can be damaged in lithotomy
obturator-adductors
saphenous- medial thigh
femoral- hip flexion/knee extension
lateral femoral cutaneous- anterior lateral thigh
sciatic- any muscle below foot-hamstring
what is a rare complication from lithotomy
compartment syndrome
preop documentation should include
neuro deficits
parathesia
neuropathies
positioning aspects that need to be documented
response to position
padding (location and type)
position changes
people present during positioning
post op neurological function
ways to prevent ulnar injuries
avoid pressure on postcondylar groove of humerus
keep hand/forearm supinated or neutral
ways to prevent brachial plexus injuries
-keep axillary roll out of axilla in decubitus position
-ultrasound for IJ placement
-avoid shoulder braces in trendelenburg
-avoid excessive lateral rotation of head
-limit arm abduction to less than 90degrees
ways to avoid sciatic/peroneal injuries
-minimize time in lithotomy
-avoid excessive pressure on fibular head (peroneal)
-use two people to move both legs in/out of lithotomy
-avoid excess flexion of hips, extension of knees, torsion of lumbar spine
incidence of median/radial nerve injuries
25% from IV insertion/infiltration
25% from axillary block
4 applications for Daltons Law
-calculate pressure of an unmeasured gas
-calculate total pressure of a gas mixture
-convert partial pressures into volumes percent
-convert volumes percent into partial pressures
which component of the oxygen delivery equation is MOST affected by Henry’s Law
PaO2
APEX
three applications of Henry’s Law
-anesthetic emergence is prolonged in hypothermic patient
-overpressuring the vaporizor
-increase the FiO2 increases the PaO2
3 Applications of Fick’s Law
-cardiac output calculation
-placental drug transfer
-diffusion hypoxia
how does partial pressure affect gas solubility
pressure decreases = solubility decreases
pressure increases=solubility increases
how does temperature affect gas solubility
temp decreases=increases solubility
temp increases= solubility decreases
Grahams Law states
molecular weight of a gas determines how fast it can diffuse through a membrane
-rate of diffusion of gas is inversely proportional to the square root of the gas’s molecular weight
-smaller molecules diffuse through a membrane faster than larger molecules
2 applications of Grahams Law
2nd gas effect- using N2O to speed up onset of a volatile anesthetic
high fresh gas flow is turbulent as it passes through the annular space
how does knowing the O2 solubility coefficient help us calculate O2 delivery
multiplying the PaO2 by the solubility coefficient (0.003mL/dL) allows us to calculate how much oxygen is dissolved in the blood
what are two applications of Boyles Law
-pneumatic bellows used for positive pressure ventilation
-diaphragm contraction increases tidal volume
-squeezing a bag valve mask
-using bourdon gauge to calculate how much O2 left in a cylinder
what is an application of Charles’ Law
LMA cuff ruptures when placed in an autoclave
What is an application of Gay-Lussac’s Law
O2 tank explodes in a hot environment
what is the r constant in PV=nrT
0.0821 liter-atm/K/mole
Ohm’s Law states
the current passing through a conductor is directly proportional to the voltage and inversely proportional to the resistance
what is viscosity
the result of friction from intermolecular forces as a fluid passes through a tube
what is viscosity inversely proportional to?
temperature
decrease temp= increased viscosity and resistance
increased temp=decreased viscosity and resistance
Reynolds number is lowest in which part of the airway?
terminal bronchioles
which areas of the airway have turbulent air flow
glottis
carina
medium-sized airways
equation for reynolds number
Reynolds #= (density x diameter x velocity) / viscoscity
what is laminar flow dependent on
gas viscosity
Poiseuilles Law
what is turbulent flow dependent on
gas density
Grahams Law
what gas mixture reduces turbulence and improves gas flow in the setting of bronchospasm
Helium/oxygen
Heliox
what are two physical principles that applies to the operation of a jet ventilator
venturi effect- if the pressure inside the tube falls below atmospheric then air in entrained into the tube
bernoulli- as airflow moves past the point of constriction the pressure at the constriction decreases
When applied to the left ventricle, which variables are included in the Law of Laplace?
Wall tension
Wall thickness
apex
Surface tension of a sphere equation and example
Tension= (pressure x radius)/ 2
Ex: alveolus, ventricle, saccular aneurysm
Surface tension of a cylinder equation and example
Tension= pressure x radius
Ex: blood vessels, aortic aneurysm
Pressure is a ____ force
Pushing
Tension is a _____ force
Pulling
Laplace equation in reference to heart
Wall stress= (ventricular pressure x radius) / ventricular thickness
The risk of ionizing radiation exposure to the anesthesia provider is:
Inversely proportional to the square of the distance of the source
Define specific heat
The amount of heat required to increase the temp of 1g of a substance by 1 degree C
What is an adiabatic process
A process that occurs without gain or loss of energy (heat)
Define critical pressure
The minimum pressure required to convert a gas to a liquid at its critical temp
Define critical temp
The highest temperature where a gas can exist as a liquid
1 atm = ____ cm H2O
Nagelhout says 1020
Apex says 1033
Fahrenheit to celcius
C= (F-32) x 5/9
Celsius to Fahrenheit
F= ( C x 1.8) + 32
Celsius to kelvin
K= C+ 273
Kelvin to Celsius
C= K-273
1 atm =
760mmHg
760 torr
1 bar
100 kPa
1033 cmH2O
14.7 lb/in^2
1mmHg= ____ cmH20
1.36
1cmH2O = _____ mmHg
0.74
What is the vapor pressure of sevo
170mmHg
What is the vapor pressure of enflurane
172mmHg
What is the vapor pressure of isoflurane
240 mmHg
What is the vapor pressure of halothane
244 mmHg
What is the vapor pressure of desflurane
669 mmHg
1 psi= ____mmHg
54
Reynolds number is directly proportional to
Fluid velocity
Fluid density
Tube diameter
Reynolds number is inversely related to
Fluid viscosity
Meaning when flow is turbulent it’s the density not the viscosity that determines the flow
Relationship of volume and pressure in boyles law
Volume decreases = pressure increases
Constant temp
Inverse relationship
Relationship between temperature and volume in charles law
Temp increase volume increase
Directly proportional
Constant pressure
Relationship of temperature and pressure in Gay Lussacs law
Temp increase pressure increase
Directly proportional
Constant volume
Forces associated with fluids
Gravity
Pressure
Friction
Which temperature monitoring site offers the best combination of accuracy and safety over an extended period of time
Esophageal
5 Laser safety steps
-use < 30% FiO2
- do not use N2O
-use laser resistant ETT
-fill cuff with saline
-protect patients eyes by taping closed, covering with saline soaked gauze and using protective glasses specific to laser being used
What positions increase cardiac preload
Trendelenburg
Lithotomy
What positions reduce cardiac preload
Reverse trendelenburg
Sitting
Flexed lateral
02 flow equation
O2 flow= (total flow) x ( FiO2- .21)/ (1-0.21)
What electrical system are ORs on
most ORs are built with an isolated power system (IPS).
This is an ungrounded power delivery system, also called a floating ground.
What is a line isolation monitor
The LIM is fundamentally an ohmmeter (resistance meter) between earth ground and each line of the IPS.
It measures the impedance between these two lines and earth ground to assess the extent to which the IPS is isolated
National Institute for Occupational Safety and Health (NIOSH) in 1977 recommended exposure limits (RELs)
2 ppm for halogenated anesthetic agents (Sevo, Iso, Desflurane) when used alone
0.5 ppm for a halogenated agent and 25 ppm of nitrous oxide when used together
N20 alone = 25ppm
1st trimester exposure inhibits DNA synthesis
how is N2O harmful for exposure
Nitrous oxide irreversibly inhibits the vitamin B-12 dependent enzyme methionine synthase, which has key roles in the folate and S-adenosyl methionine (SAM) cycles
Risks to Pregnancy with WAG
NIOSH Study:
-Increased risk of spontaneous abortion and congenital abnormalities in children of women who worked in the operating room
-an increased risk of congenital abnormalities in offspring of unexposed wives of male operating room personnel.
Follow Up Studies: Other job-associated conditions besides exposure to trace anesthetic gases, such as stress, infections, long work hours, shift work, and radiation exposure, may account for many of the adverse reproductive outcomes
Proper Work Practices for the Management of Waste Anesthetic Gases
-Ensure tight fit of anesthetic mask
-Ensure tight fit of endotracheal tube cuff or laryngeal mask airway
-Ensure absence of leaks in anesthetic machine and tubing
-Use low-flow techniques when appropriate (e.g., during maintenance phase of anesthetic)
-Do not administer inhaled anesthetic until scavenging system is active
-Ensure that anesthetic vaporizer(s) are turned off when anesthetic machine not in use
surgical smoke risk in OR
Electrocautery smoke can contain mutagenic, carcinogenic, and toxic compounds
“verage plume created in a single day in the OR is equivalent to smoking as many as 30 unfiltered cigarettes.”- AORN
USE N95 or smoke evacuators
what are the limits for ionizing radiation
Annual limit = 50 mSv
Allowable lifetime limit = 10
mSv X Age in years
Pregnant or lactating worker monthly limit = 5 mSv
what does ALARA stand for
As Low As Reasonably Achievable
TIME
DISTANCE
SHIELDING
what does the Inverse square Law apply to
applies to radiation, light, pressure waves and electricity
what are some ways to shield from ionizing radiation
thyroid shield
lead apron
lead lines glasses
what is recommended for anesthesia machine for TB/COVID patients
TB/COVID – Must have viral filter on expiratory limb to protect machine from contamination
Recommended airway filter before Y-piece and before ETCO2 sampling
Inspiratory filter only if machine has been contaminated
incidence of surgical fires
550-650 in US annually
5-10% associcated with serious injury or death
what percentage of fires are in patient fires
airways 38%
surgical fire prevention steps
-Reduce O2 concentration to less than 30%
-Do not use open O2 administration sources
-Use of adequate tenting technique with scavenging
-Communicate with surgical team
-Use cuffed/Laser ETT’s
-Pay attention
what kind of O2 is flammable
FiO2 and FeO2
inspired and expired O2
steps for airway fire
-Look for early warning signs
-Stop Ventilation, turn off gas, disconnect circuit, do not ventilate, and extubate
-Pour saline into airway to extinguish fire
-Remove any left over materials
-Ventilate patient, re-establish airway
-Assess injury
-Consider bronchoscopy
what are some chemical makeups of CO2 absorbent
Chemical makeup of the absorbent
Fresh gas flow rates
Minute ventilation
Anesthetic itself
what can lead to accelerated degradation of CO2 absorbent
High fresh gas flows accelerate the desiccation of absorbent, and this leads to accelerated degradation
Because this is an exothermic process, temperature of the absorbent may increase dramatically
what is a risk with CO2 absorbent and volatile anesthetics
Exothermic reaction results from interaction of desiccated carbon dioxide absorbent and volatile anesthetics (especially sevoflurane) can produce extremely high temperatures inside of the absorbent canister
Temperature increase may lead to explosion and fire in the canister or anesthetic circuit
How To ensure maintenance of adequate hydration in the absorbent?
-Change the absorbent regularly
-Turn fresh gas flow down or off on unattended anesthesia machines
-Limit fresh gas flows during anesthesia
-When in doubt about hydration of the absorbent. . . Change it!
what is ohms law used for
Used to predict that ↑ resistance over constant voltage will ↓ current
For electricity to flow there must be a completed circuit. The ground is a conductor connected to the earth (ground) providing a low resistive alternate route for the electricity to flow in the case of electrical surge.
what physiological equation is the ohms law a basis for
BP= CO x SVR
Blood pressure is analgous to the voltage (V)
Cardiac output to current (I)
SVR to resistance (R)
what are some unintentional sources of electrical shock
cardiac pacing wires
invasive monitoring catheters
what is a macroshock
current large enough to cause injury to the bodys surface
what is an electrical shock
body contact with two conductive materials at different voltage potentials that complete a circuit
how many microamps does it take to stop the heart
10 microamps if current bypasses the skin and conducted within the body
what are some of the bodys natural resistance to electrical currents
dry intact skin
what is impedence
resistance to current of electricity
what helps electrical shock prevention
Isolation transformer
GFI or GFCI
Usually not installed in OR’s
Line isolation monitors
explain the 1993 National electrical code
Requires either GFCI or isolated power systems in wet locations
Isolated power systems are more likely used in ORs, because a GFCI would interrupt power to other equipment (lighting, ventilators, monitors)
what is the prime function of a circuit breaker
fire prevention
describe Isolated Power System (IPS)
No direct connection to power supplied to the hospital and isolated from the ground
Electrical potential difference between the energized wire and ground is 120 v in a typical household circuit
Potential difference between either line of an isolated power system and ground is 0 v
Person who is grounded and in contact with a live wire in OR with an isolated power system should suffer no ill effects
what is used in wet locations to lessen the possibility of macroshocks
GFCIs
Isolated power systems
what is a line isolation monitor
Assesses the integrity of the isolated power system and alarms when more than 2-5 mA of current flows to ground
what are line isolation monitors used to protect from
MACRO shocks not micro shocks
what are the frequencies of electrosurgery
Frequencies 300 kHz to 2 MHz
what is unipolar electrocautery
One tip to deliver an electric current
Needs a return pad (dispersive electrode) to complete its circuit
Path from the unipolar device to the return pad should never cross the patient’s heart
Placement of the pad should be away from bony prominences and metal objects as well to minimize risks for burns
what is bipolar electrocautery
Two tips, one to supply the electric current and the other to return the current
Do not require a return pad and are less likely to cause burn or injury away from the local area of use
Especially effective during abdominal surgery as in tube/ovary surgery to prevent possible fatal bowel injury
Prevents widespread tissue coagulation
Part held by surgeon like a forceps with current entering one prong and leaving by the other – no grounding plate required
what is the safest approach when AICD and electrocautery used
The safest approach is to disable the AICD’s ability to defibrillate.
Each manufacturer uses a magnet to apply modalities to their specific device, so it is safest to consult with the representative before surgery and to interrogate the AICD postoperatively
steps to take with an external pacemaker
Wrap wires with rubber gloves
Use non-electric OR bed
Avoid sources that might cause external interference with the pacemaker’s function
Do not touch intracardiac leads of any kind unless wearing gloves – especially not while touching a metal surface or piece of equipment
Contact precautions
Prevents transmission of infectious agents by contact with the patient or environment
Droplet precautions
Prevents transmission of infectious agents spread by close contact with respiratory secretions
Airborne precautions
Prevents transmission of infectious agents suspended in the air
Ex: TB, measles, varicella, Covid
Venous pressure increases:
-hydrostatic pressure -> edema of face, eye and airway
-intracranial htn
What 4 body positions are associated with a higher incidence of hemodynamic instability under GA
Reverse trendelenburg
Sitting
Flexed lateral
Prone
Name 5 common anesthesia techniques that attenuate the body’s compensatory mechanisms for maintaining CV stability in trendelenburg
General anesthesia
Neuraxial anesthesia
Positive pressure ventilation
Peep
Muscle relaxants
The trendelenburg position (4)
Reduces pulmonary compliance
Increases risk of endobronchial intubation
Diaphragm moves cephalad
FRC is resuced
How does head down affect the patient
Compressed lungs
Impairs function of diaphragm
Decreases pulmonary compliance
Increases peak inspiratory pressure
Decreases total lung volume
Decreases FRC
How does head up affect the patient
Improves diaphragm function
Lungs expand freely
Increases pulmonary compliance
decreases peak inspiratory pressure
Increases total lung volume
Increases FRC
What happens to the endotracheal tube tip during neck flexion
Pushes ETT tip towards carina
Increases risk of endobronchial intubation
What happens to ETT tip with neck extension?
Moves tip towards vocal cords
Increase risk for inadvertent extubation
Where could ETT tip settle in trendelenburg
Mainstem bronchus
Pushes diaphragm towards ETT increasing risk of endobronchial intubation
In a patient with facial edema, what are two ways you can assess airway patency before extubation
Perform leak test for air movement around ETT
Visually inspect larynx with DL
What type of brachial injury can occur when a bean bag is used for positioning
Compression injury
A patient is unable to abduct his 5th digit after a prolonged stay in ICU. Which nerve sustained an injury
Ulnar nerve
Ulnar nerve injury presentation
Impaired sensation of the 4th and 5th digits
Inability to abduct or oppose the pinky finger
Chronic injury presents with claw hand
What’s the most common nerve injury
Ulnar nerve
Which nerve is most likely to be injured following a traumatic IV insertion in the AC
Median nerve
What is the only nerve to pass through the carpal tunnel
Median nerve
Median nerve injury presents with
Reduced sensation over palm
Inability to oppose the thumb
What can cause radial nerve injury
Excessive BP cycling
Upper extremity tourniquet
External compression of IV pole
How does radial nerve injury present
Wrist drop
Inability to extend the hand
How does a common peroneal nerve injury present
Foot drop
Inability to every the foot
Inability to extend toes dorsally
Which complications are most commonly associated with the sitting position (2)
Midcervical tetraplegia
Paradoxical air embolism
In a patient with a mediastinal mass what are 3 things that worsen tracheobronchial compression
Supine
Induction of GA
Loss of spontaneous ventilation
name the injury
Median n
name the injury
radial nerve injury
name the injury
ulnar nerve injury
what are the most common nerve injuries in the OR
ULNAR NERVE 1st
brachial plexus injuries
lumbosacral injuries
CPP=
CPP= MAP - ICP
Normal CPP
60-80 mmHg
Normal MAP
70-100 mmHg
Normal ICP
7-15 mmHg
What nerve root is dark purple area
C8
What nerve root is the hot pink area
C7
What nerve root is the light blue
C6
What nerve root is the yellow
T1
What nerve root is the dark blue
C5
what nerve supplies the dark yellow section
femoral nerve (anterior cutaneous root)
what nerve supplies the light yellow section
saphenous nerve
what nerve supplies the pink area
lateral cutaneous
what nerve supplies light blue and dark blue
common fibular/peroneal nerve
what nerve supplies the green area
posterior cutaneous
what nerve supplies the purple areas
tibial nerve
what nerve supplies the red area
lateral femoral cutaneous
what nerve supplies the dark purple
posterior cutaneous
what nerve supplies the light purple
saphenous
what nerve supplies the blue area
common peroneal
what nerve supplies the brown area
tibial nerve
where does the femoral nerve supply
green area
what area does the obturator nerve supply
orange area
where does the medial cutaneous nerve supply
purple areas
where does the axillary nerve supply
red areas
where does the median nerve supply
blue areas
which nerve supplies the brown area
ulnar nerve
which area does the radial nerve supply
green areas
which nerve supplies the musculocutaneous nerve supply
yellow areas
What are the roots of the musculocutaneous nerve
C5 C6 C7
axillary nerve roots
C5 C6
radial nerve roots
C5 C6 C7 C8 T1
median nerve roots
C5 C6 C7 C8 T1
ulnar nerve roots
C7 C8 T1
Risk of compartment syndrome increases with:
-hypotension
-advanced age
-obesity
-anemia
-connective tissue disease
What kind of injury is compartment syndrome
A reperfusion injury
Tissues swell due to reperfusion of an ischemic area
Your patient reports decreased sensation over the dorsal surface of the lateral three and one half fingers. Which nerve has been injured
Radial nerve
valley
After surgery, your patient states they are unable to flex their arm and that they had decreased sensation over the ventral surface of their forearm. Which nerve is injured?
Musculocutaneous nerve
Weakened skeletal muscle function below the knee is a symptoms of injury to which nerve
Sciatic nerve
Your patients foot has been in plantar flexion during a very long surgery. What nerve injury is most likely to result from this?
Anterior tibial nerve
The surgeon places a self-retaining retractor which can cause compression of this nerve against the pelvic brim
Femoral nerve
What 3 nerves may cause foot drop when injured
Sciatic
Common peroneal
Anterior tibial
Gases that are more blood soluble will diffuse across a liquid/gas interface such as the alveolar capillary membrane in greater or lesser quantities than a less soluble gas? What law applies?
Gases that are more blood soluble diffuse in greater quantities across liquid/gas interfaces, as described by Fick’s law of diffusion
Describe the second gas effect. What law applies?
When one gas delivered at a high inspired concentration (first gas such as N2O) accelerates the blood uptake of a concurrently administered companion gas (second gas such as isoflurane, halothane, desflurane, sevoflurane, or enflurane), this is the second gas effect. Fick’s law of diffusion explains this phenomenon.
What happens to the volume of the cuff of the endotracheal tube when N2O is turned on? Explain this phenomenon. Whose law applies?
The cuff will expand. More N2O will diffuse into the cuff from the surface of the trachea than will N2 diffuse from the cuff because N2O is much more soluble in blood than N2. Fick’s law of diffusion applies
If you have 500 ml of oxygen at a pressure of 1520 mmHg (two atmospheres) what volume would be present at 760 mm Hg (one atmosphere) if temperature did not change? What law applies?
1000 ml.
Halving the pressure to 760 mm Hg while maintaining pressure constant doubles the volume.
Boyle’s law applies.
A patient is sitting in a chair and breathing spontaneously. Whose gas law applies?
Boyle’s Law.
At constant temperature, the volume of a gas in the lungs varies inversely with intrapulmonary pressure.
When intrapulmonary pressure becomes negative (decreases) intrapulmonary volume increases
Whose law explains the operation of a bellows ventilator?
boyles law
A full E cylinder of oxygen will empty 625–675 liters into the atmosphere. What law applies? Explain.
Boyle’s law applies.
Pressure and volume are inversely related, if temperature is constant. A relatively small volume of gas is found at high pressure in the cylinder. When the gas is released into the atmosphere (relatively low pressure), a large volume results.
How do you calculate the partial pressure of a gas mixture if you know its percent concentration?
Partial pressure = ( % concentration/100) x total pressure
What is the partial pressure of nitrogen at one atmosphere? Whose law permits this calculation to be made?
N2 is 79% of the atmosphere. Partial pressure of N2 at 1 atm. = 0.79 x 760 = 600 mmHg. Dalton’s law of partial pressure applies
Henrys Law is used for what two purposes?
Henry’s law is used to calculate:
(1) the amount of oxygen dissolved in blood (O2 dissolved = PO2 x 0.003)
(2) the amount of carbon dioxide dissolved in blood (CO2 dissolved = 0.067 x PCO2).
What happens to the temperature of a liquid as vaporization occurs?
Since vaporization requires energy, the temperature of a liquid decreases as vaporization proceeds. As the liquid temperature falls, a gradient is established between the liquid and the surrounding environment. Energy flows from the warmer area (surroundings) to the cooler area (liquid)—this flow of thermal energy is called heat. At some point, an equilibrium is reached at which the energy lost (heat) to vaporization is matched by the energy supplied from the surroundings (heat)
What is heat of vaporization? What is the latent heat of vaporization?
A liquid’s heat of vaporization is the number of calories (a measure of energy) necessary to convert 1 mL liquid into a vapor.
The latent heat of vaporization is more precisely defined as the number of calories required to change 1 g of liquid into vapor without a temperature change.
Describe what may happen to vapor pressure if a carrier gas flows through the vaporizer container.
As a flow of gas (carrier gas) passes through the vaporizer container, molecules of vapor are carried away. This causes the equilibrium to shift so that more molecules enter the vapor phase. Unless some means of supplying heat is available, the liquid will cool.
As the temperature drops, so does the vapor pressure of the liquid, and the carrier gas will pick up fewer molecules so that there is a decrease in concentration in the gas flowing out of the container.
Will saturated vapor pressure change with a change in altitude?
Vapor pressure is a function of temperature. Thus, vapor pressure will not change with a change in altitude if the temperature remains constant.
A volatile agent is poured into a flask containing 100% oxygen. Explain how to calculate the % volatile agent and the % oxygen above the liquid.
% volatile agent = (saturated vapor pressure of volatile agent)/(760) x 100. % oxygen = 100 - % volatile agent.
What will happen to the gas concentration delivered to the patient if enflurane or sevoflurane is placed in an isoflurane vaporizer? Why?
The delivered concentration of enflurane or sevoflurane will be less than expected by the dial setting because enflurane and sevoflurane have lower vapor pressures than isoflurane.
When considering flow through a tube, the gradient in hydrostatic pressure (inflow pressure minus outflow pressure) equals flow times resistance. Mathematically, Pin - Pout = F x R. Whose law describes this relationship?
Ohm’s law.
How are flow and resistance related?
Flow through a tube is inversely proportional to resistance.
For example, if resistance doubles, flow is halved. If resistance is halved, flow is doubled
What happens to flow and what happens to resistance when the radius of a tube increases? When radius of a tube decreases?
When the radius of a tube increases, resistance to flow decreases and flow increases.
when the radius of a tube decreases, resistance to flow increases and flow decreases
Hagen-Poiseuille’s law states that laminar flow is proportional to what two factors? Inversely proportional to what two factors?
Flow is directly proportional to:
(1) the pressure drop along the tube;
(2) the fourth power of the radius (r4) of the tube.
Flow is inversely proportional to:
(3) the length of the tube;
(4) the viscosity of the fluid.
If the radius of a tube is doubled, how much does laminar flow increase? If the radius of a tube is tripled, how much is laminar flow increased? What law applies?
Flow increases 16 times if the radius of a tube is doubled
81 times if the radius is tripled.
Hagen-Pouiseulle’s law describing laminar flow through tubes applies
Assuming laminar flow through a tube, how much does flow through a tube decrease if the radius of the tube decreases to one-third of its original value? Whose law applies?
If the radius of a tube decreases to one-third of its original size, flow will decrease to 1/81 of its original value. Flow is proportional to the radius to the fourth power (r4). 1/3 x 1/3 x 1/3 x 1/3 = 1/81. Hagen-Poiseuille’s law applies. Note also that if radius is halved, flow is reduced to 1/16th of its original value. If radius is doubled, flow increases 16-fold. If radius is tripled, flow increases 81-fold.
If flow through a tube is laminar (streamlined), explain how resistance and flow are changed if radius is: doubled, halved, tripled, or reduced to one-third of its original value.
According to Hagen-Poiseuille’s law, when radius is doubled, resistance is decreased to 1/16th of its original value and flow is increased 16-fold; when radius is halved, resistance is increased 16-fold and flow is decreased to 1/16th of its original value; when radius is tripled, resistance is decreased to 1/81 of its original value and flow is increased 81-fold; when radius is decreased to 1/3rd of its original value, resistance is increased 81-fold and flow is decreased to 1/81 of its original value.
In order to decrease peak inspiratory pressure, you change the endotracheal tube from a 6.0 to an 8.0. Whose law explains this decreased resistance?
Hagen-Poiseuille’s law. The greater the radius of a tube, the lower the resistance.
Peak inspiratory pressure is greater when inflow resistance is higher, and vice versa
Is the viscosity of a fluid (gas or liquid) important during laminar or turbulent flow?
Viscosity is a determinant of gas flow when flow is laminar. Flow is inversely proportional to viscosity (the greater the viscosity, the lower the flow) when flow is laminar (non-turbulent)
Identify three conditions that can change laminar to turbulent flow during anesthetic administration.
(1) Gases changing direction (bend in tube of more than 20 degrees)
(2) increased velocity
(3) rough walled (corrugated) tubes.
When flow of gas through a nasal cannula is low, flow is determined by what property of the gas? Whose law applies?
When flow of a gas through a tube such as a nasal cannula is low, flow is laminar. For laminar flow, the viscosity of the gas is a determinant of flow. This is shown by Poiseuille’s law
What property of a gas determines gas flow rate through a variable orifice flow meter at low flow rates?
Viscosity.
Flow through a variable orifice flow meter is laminar when flow is low, so flow rate is inversely proportional to viscosity.
What property of a gas determines gas flow rate through a variable orifice flow meter at high flow rates?
Density.
With high flows, flow through a variable orifice flow meter is turbulent, and flow rate is inversely proportional to gas density.
Venturi extended whose work? What observations did Venturi make?
Venturi extended Bernoulli’s work on the relationship between the velocity of flow of a fluid and the lateral pressure exerted on the wall of a tube.
What principle of physics explains the operation of the high frequency jet ventilator?
The Venturi effect explains high frequency jet ventilation. In fact, high frequency jet ventilation is sometimes referred to as jet Venturi ventilation.
The Law of Laplace relates tension in the wall of a tissue, the pressure inside the wall, and the radius of the structure. How do radius and tension generally relate to each other?
According to the law of Laplace, the tension in the wall of a hollow structure (blood vessel, left ventricle, or normal alveolus) is proportional to the radius.
The greater the radius in a chamber or vessel, the greater the tension in the walls of the chamber or vessel.
T is proportional to P x r, where T is tension, P is pressure, and r is radius.
Does a dilated ventricle exert more tension compared with a normal ventricle? What law applies?
Yes, a dilated ventricle has greater tension in its wall.
This is the law of Laplace. The greater the radius of a chamber, the greater the tension in the wall.
Define and differentiate between macroshock and microshock.
Macroshock refers to a large voltage applied to skin or tissue.
Microshock refers to small voltages or currents applied directly to the heart
How many microamps are required to cause microshock-induced ventricular fibrillation?
A minimum of 50 microamps can cause microshock-induced ventricular fibrillation
How many milliamps are required to cause macroshock-induced ventricular fibrillation?
100–2,500 milliamps can cause macroshock-induced ventricular fibrillation
Is the electrical equipment in the operating room grounded or isolated? Electrical equipment in the operating room is monitored by what?
Electrical equipment in the operating room is isolated with isolation transformers.
It is monitored by a line isolation monitor (LIM)
What is the function of a line isolation monitor, and how does it work?
Line isolation monitors monitor isolation of the transformer in every operating suite. Every operating room has electricity that is isolated from the main power by an isolation transformer.
What triggers the alarm of the line isolation monitor?
The line isolation monitor alarms if either isolated power line is less than 60,000 ohms or if a fault would draw more than 2 milliamps (mA). Newer LIMs may be set to trigger at 5 mA.
What should be done if the alarm of the line isolation monitor goes off?
If the LIM alarm goes off, check the gauge to determine if it is a true fault. The other possibility is that too many pieces of electrical equipment have been plugged in and the 2-mA limit has been exceeded.
If the gauge is between 2 and 5 mA, it is probable that too much electrical equipment has been plugged in.
If the gauge reads >5 mA, most likely there is a faulty piece of equipment present in the OR.
The next step is to identify the faulty equipment, which is done by unplugging each piece of equipment until the alarm ceases. If the faulty piece of equipment is not of a life-support nature, it should be removed from the OR. If it is a vital piece of life-support equipment, it can be safely used.
Long thoracic nerve injury roots and result in what?
C5 C6 C7
Serratus anterior muscle dysfunction with winging of the scapula
