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Anesthesia > Test 1- Week 1 > Flashcards

Test 1- Week 1 Flashcards

1
Q

Analgesia

A

Analgesia is a loss of sensitivity to pain

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2
Q

Nociception

A

Nociception is the neural process of encoding noxious stimuli Does not require consciousness

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3
Q

Tranquilization

A

Tranquilization is a state of behavioral change, wherein anxiety is relieved and the patient is relaxed, although aware of its surroundings

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4
Q

Sedation

A

Sedation is a state characterized by CNS depression accompanied by drowsiness. The patient is likely unaware of its surroundings

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5
Q

Compressed gas  Oxygen

A

 Absolutely necessary!

 Delivering anesthetic gas in air (21% O2) would lead to hypoxemia due to hypoventilation and V/Q mismatch induced by anesthetics themselves

 Remember your respiratory physiology!

 30-35% O2 (FiO2=0.30-0.35) minimum acceptable for people and small animals

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6
Q

What is the metabolic requirement for oxygen?

A

 5-10 mL/kg/min
 Ex. 50-100 mL/min (0.05-0.1 L/min) in a 10 kg

dog

This would be the minimum O2 flow required

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7
Q

What colors are these correspond to green, blue, or yellow?

A

 Oxygen = green
 Nitrous oxide (N2O) = blue

 Medical air = yellow

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8
Q

Tank safety

A

Tank safety

 NEVER leave an unsecured tank sitting upright

 E cylinders – rack, rolling cage

 H cylinders – anchored to wall or in transport cart with chain

 May explode if dropped or falls over  Can become a projectile

 TO AVOID FIRE (heat is created as gas expands):

 Clean oils from hands and tank, open cylinder

valves slowly

 Open and close valve briefly before attaching to machine to remove dust from connecting port

12

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9
Q

What is cylinder pressure in vs breathing system pressure?

A

Cylinder pressure usually in psi (pounds per square inch)

 Breathing system pressure in cmH2O (centimeters water)

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10
Q

High and low pressure systems

A

High pressure (100-2200+ psi)
 Gas cylinder, yokes, pressure gauges, regulators

Intermediate pressure (50 psi)
 Central O2 supply, post-regulator, flush valve,

input to flowmeter, driving gas for ventilator

 Low pressure (<15 psi)

 Between flowmeter output and common gas outlet

 Breathing system (= pressure in patients’ lungs)

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11
Q

Oxygen cylinders

A

 E cylinder (MOST COMMON in small animal general practice)

Capacity = 660 L (memorize this number!)

 H cylinder

 Capacity = 6600 L

 Both are filled to a pressure of 2200 psi

 Pressure is proportional to volume  P1V1 = P2V2 (Boyle’s law)

 Therefore, you can figure out roughly how many liters are left in the tank if you know tank pressure

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12
Q

N2O cylinders

A

 N2O exists in both a gaseous and liquid form in the tank

—– Gauge only reads gas pressure

 Therefore, it is NOT POSSIBLE to calculate the amount of gas remaining based upon the pressure if liquid N2O remains

  • you have to weight the tank in order to figure out much is left!
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13
Q

What are the safety systems in place to make sure that you don’t put the wrong tank on the wrong?

A

Color-coded tanks
Labelling
Diameter index safety system

 Non-interchangeable gas-specific threaded connection system

 Used universally by all equipment and cylinder manufacturers

Pin index safety system

 Gas-specific pin patterns that only allow connections between the appropriate cylinder yokes and E tanks

 Commonly found on yokes mounted to anesthesia machines, also some cylinder- specific regulators/flowmeters

Quick connectors

 Manufacturer-specific

 Facilitate rapid connecting and disconnecting of gas hoses

 Useful for multipurpose work areas

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14
Q

Regulator

A

 AKA pressure-reducing valve

 Decreases tank pressure to a safe working pressure (approx. 50 psi) which is supplied to the flowmeter

 Prevents pressure fluctuations as the tank empties

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15
Q

Flowmeter

A

 Controls rate of gas flow through the vaporizer

 L/min

 Gas enters at bottom at 50 psi and exits at top at 15 psi

 Tapered glass tube with moveable float

 Narrow at the bottom, wider at top

 Single- or double-taper  Double taper for more

accuracy at lower gas flows

 Calibrated for 760 mmHg and 20 C

Reduces gas pressure from 50 psi (intermediate) to 15 psi (low)

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16
Q

Where do you read the flow?

A

MIDDLE OF BALL

TOP OF BOBBIN

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17
Q

Are flowmeters gas specific or can they be used for any gas?

A

 Gas-specific
 Ex. O2 flowmeter NOT accurate if used for N2O

or medical air

 If there are multiple flowmeters, O2 should be on the far right (downstream of all other gases) to prevent delivery of a hypoxic gas mixture

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18
Q

Quick flush

A

 Delivers O2 from the intermediate pressure area of the machine (50 psi)

 BYPASSES vaporizer
 Contains NO anesthetic agent

 Delivers gas at a rate between 35-75 L/min directly to the patient circuit

 Appropriate use:

 Quickly decrease anesthetic gas % in the circuit  Emergency

 Recovery
 Remember this is pure O2 as it has bypassed the

vaporizer

 Patient should be disconnected from the circuit temporarily before the O2 flush valve is utilized

 Can result in dangerous increases in breathing circuit pressures

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19
Q

What is a possible complication of quick flush?

A

 Possible complication = PNEUMOTHORAX

Small circuit, high pressure, small patient

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20
Q

Anesthetic vaporizers

A

 Change liquid anesthetic into vapour
 Deliver selected % of anesthetic vapour to

the fresh (common) gas outlet

 “Volumes percent”

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21
Q

Inhalants

A

 Vapor = Gaseous state of substance that is liquid at ambient temp and pressure

 Halothane, Isoflurane, Sevoflurane, Desflurane  Gas = exists in gaseous state at ambient T

and P
 N2O, Xenon

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22
Q

Vapor pressure

A

 Vapor pressure = Pressure exerted by vapor molecules when liquid and vapor phases are in equilibrium

 Depends on temperature
Increases with increasing temperature

 Inversely related to boiling point

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23
Q

saturated vapor pressure

A

Vapors have a maximum administration percentage = saturated vapor pressure- most amount of anesthestic that can be in vapor gas

 Vapor pressure/Barometric pressure

 Ex. Iso 32%

 Vaporizers needed to reduce this to clinically useful doses

24
Q

Anesthetic vaporizers

A

 Modern vaporizers are:

 Agent-specific

 Concentration-calibrated

 Variable-bypass

 Flow-over

 Out-of-circuit

 High resistance

 Compensated for temperature, flow, and back- pressure

25
Q

variable-bypass

A

A specific concentration is created by variable-bypass system, where fresh gas flows over a reservoir of liquid anesthetic and mixes with carrier gas

26
Q

out-of- circuit (VOC)

A

All modern vaporizers are out-of- circuit (VOC)

 Carrier gas is from flowmeter

 Anesthetic % is known = precision vaporizer

VAPOR IS NOT IN THE PT CIRCUIT

27
Q

VIC vaporizers – Non-precision

A

 In the past, vaporizers were in the circuit (VIC) – non-precision

 Glass jar containing wicking material

 Increase surface area for vaporization  Ensures saturation with anesthetic gas

 Variable bypass

 Carrier gas is patient’s expired gases  Cannot produce a known anesthetic %
 Not temperature compensated
 Not currently recommended

28
Q

Precision vs non-precision

A
29
Q

Modern vaporizers compensate for:

A

 Temperature between 15-35 C.
 Flow rate between 0.5 and 10 L/min

 Back pressure associated with positive pressure ventilation and use of flush valve

30
Q

Vaporizers

A

 Require no external power (except desflurane)

 Routine maintenance is required and must be performed by a qualified technician

 Mounted on a “back bar” on the machine

 Cannot be tipped – must be emptied before transporting

31
Q

Filled with wrong agent?  What would happen?

A

What would happen?

 Depends on vapour pressure and potency of each agent

 Iso in sevo vaporizer could produce a lethal concentration (higher vapour pressure AND higher potency)

 Drain and run 1 L/min O2 until completely dry

32
Q

Vaporizer tipped
 What would happen?

A

Vaporizer tipped
 What would happen?

 Anesthetic may enter the bypass channel and deliver a high concentration

 Run 1 L/min O2 through machine with vaporizer off

33
Q
A

Re-breating System

 i.e. Circle/Y-piece

34
Q
A
  1. Re-breating System

 Universal “F”

35
Q
A
  1. Non-rebreathing System

 i.e. Mapleson D

36
Q

The Re-breathing System

A

 One-way (circular) gas flow

 Inspiratory and expiratory breathing limbs

 CO2 absorber prevents rebreathing of excessive CO2

 Patient re-breathes inhalant and O2 via inspiratory limb

37
Q

The Re-Breathing System Advantages Vs disadvantages

A

 Advantages

 Lower fresh gas flow rate
 Saves $$$
 Decreases environmental pollution
 Patient breaths warm, humidified gases (re-breathes)

 Disadvantages
 More components  more potential for leaks  ↑resistance for smaller patients (< 3-10 kg)

 [anesthetic gas] changes SLOWLY
 Due to lower O2 flow rate (more on that in the inhalant lecture!)

38
Q

How do rebreathining systems work?

A

One-way or Unidirectional Valves

 Inspiratory
 Expiratory

39
Q

Oxygen Flush Valve:

A

Oxygen Flush Valve:

 Bypasses vaporizer!

 DILUTES gases in breathing system and reservoir bag  Delivers oxygen directly to the breathing system 35-75 L/minof100%oxygen

CAUTION:
 Avoid activation with patient attached to system  NEVER NEVER NEVER w/non-rebreathing system!

40
Q

Fresh Gas Inlet:

A

Fresh Gas Inlet:
 fresh gas (not breathed)

= Hose that provides breathing system with:

oxygen +/- inhalant

 MUST check this connection when changing breathing systems

 It is SHARED btw re-breathing and non-rebreath

41
Q

Adjustable Pressure-Limiting (APL) Valve:

A

 Adjustable Pressure-Limiting (APL) Valve:

 Aka pop-off valve

 Limits pressure buildup in breathing system

OPEN ALWAYS unless:

 Pre-use machine check (MUST OPEN when done!)

 Must close to administer positive pressure ventilation  Manual or controlled

 Closed APL valve  ↑ pressure in breathing system cardiopulmonary injury

 Can result in patient DEATH!

42
Q

Breathing System Pressure Gauge:

A

 Breathing System Pressure Gauge:

 Measures pressure in the breathing system

 Should be ZERO (0)!

 Exceptions:
 unless performing leak checks (pre-use check)  providing positive pressure ventilation (IPPV)

43
Q

Carbon Dioxide Absorber:

A

 Soda lime most commonly used today

 Absorber assembly has canister to hold soda lime, 2 ports for connecting breathing tubes, fresh gas inlet, +/- unidirectional valve mount and bag mount

 What is soda lime?
 Calcium hydroxide with small amount of sodium hydroxide

and color indicator
 Indicator = ethyl violet (fresh white; exhausted purple)

 Carbon Dioxide Absorber (continued…)  Monitor time (limited)
 Heat reaction and color change when active

 When filling:

 Do not pack tightly, avoid dust of broken particles

 Check gaskets & seals as a source of leaks (esp if dust particles present)

 Signs of Exhaustion

 Increase end tidal CO2

 If at a light enough plane of general anesthesia:  Increased ventilation
 Increase in HR & BP initially (then decrease)

 Rebreathing (seen on ETCO2)

 Respiratory acidosis

 Red mucous membranes (carbon monoxide production and inhalation)

44
Q

Reservoir Bag:

A

 Functions

 Observe ventilation, inspiratory reserve, administer manual positive pressure ventilation

 Calculation of bag size:
 Formula = tidal volume (10-20 mL/kg) x 6  Round UP if in between sizes

 Example:
 10 kg canine patient x 10-20 mL/kg x 6

= 600mLround up to 1L bag

45
Q

Oxygen Flow Rates:

A

Oxygen Flow Rates:
 MANY different flow rates may be used with this type

of system

 Typically in small animals
 Induction & Recovery = (HIGH)50-100 mL/kg/min O2

 Maintenance =(SEMI-CLOSED)20-50 mL/kg/min O2

 Typically in large animals
 Induction & Recovery = 20-50 mL/kg/min O2

 Maintenance = (LOW)10-20 mL/kg/min O2

46
Q

The Non-rebreathing System

A

 Components:
 Fresh gas
 Nonrebreathing tubes
 APL (Mapleson D) OR open/close (Mapleson F) valve  Reservoir bag

 Missing components:
 Soda lime canister
 Unidirectional valves
 O2 flush button (NEVER USE WITH THIS SYSTEM!)

47
Q

Advantages and Disadvantages of Non-rebreathing system

A

 Advantages
 Very light, with minimal dead space or resistance to

ventilation (good for patients < 3-10 kg; 5kg @ RUSVM)  Fewer components = fewer potential for leaks
 [anesthetic gas] changes rapidly (high gas flow)

Disadvantages

 High gas flow rates
 $$$ to run in larger patients
 ↑ environmental pollution
 No rebreathing = gases not as warm or humidified

48
Q

The Non-rebreathing System

 Oxygen Flow Rates:

A

Oxygen Flow Rates:
 HIGH when compared to rebreathing systems

 *O2 flow is mechanism for eliminating CO2 !*
 Must be a least 2-3 x tidal volume in most cases

 200-300 mL/kg/min O2

 What monitor would help determine if rebreathing CO2 via O2 flow rate too low?

49
Q

Endotracheal Tubes and Intubation

Indications:

A

Indications:

 Maintain patent airway

 Protect airway from foreign material

 Blood, regurgitation

 Provide intermittent positive pressure ventilation

(IPPV)

 Apply tracheal or bronchial suction

 Administer oxygen

 Deliver inhalant anesthesia

50
Q

Benefits of Intubation:

A

 Reduced anatomical dead space
 IF correct size and position of tube
 Dead space = air WITHOUT gas exchange

 Maintain inhalant anesthesia with minimal environmental contamination

 Properly inflated cuff

51
Q

Routes of Intubation:

A

 Oral
 Nasal
 External Pharyngotomy

 Tracheostomy

52
Q

What is the most common type of ET tube?

A

Murphy

53
Q

Laryngoscope:

A

Laryngoscope:

 Makes intubation safer and easier!

 Allows visualization of airway

 Light source

 Apply light pressure to base of tongue, just rostral to epiglottis

 Apply gentle pressure ventrally, this tilts larynx, opens glottis, & frees soft palate from epiglottis (if it was entraped)

 Do NOT apply significant pressure directly on epiglottis!  Risk = fracture of hyoid apparatus

54
Q

Scavenging Waste Gases

PASSIVE SYSTEMS:

A

 Non-recirculating room ventilation system

 Charcoal absorption (F air canisters)*  Does NOT scavenge nitrous oxide

 Piping direct to atmosphere (i.e. via window)

55
Q

ACTIVE Scavenging systems

A

Piped vacuum (white drop and tubing)*

56
Q

SCAVENGING GASES: CHARCOAL ABSORPTION

A

ADVANTAGES:

  • Absorbs hydrocarbons
  • Does not release to ozone

• Portable

DISADVANTAGES:

  • Does not adsorb N2O
  • Absorbs hydrocarbons only!
  • Flow- limited
  • Added Resistance
  • Weigh before use
  • record number of grams
  • Discard when 50 grams + or 8-12 h of use

thus, FINITE USE

57
Q
A

Anesthesia (14 decks)

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