Anesthesia Exam Two Learning Objectives

What is the purpose of an anesthesia machine?

Prepare precise, variable gas mixture to breathing circuit

Name the bulk tank with its pressure and volume.

H tank

7000 L

2000 psi

Name the portable tank with its pressure and volume.

E tank

700 L

2000 psi

How do you calculate the volume remaining in an oxygen tank based on its pressure reading?

Pressure reading/2000 psi x 700 (if E) or 7000 (if H)

What is the color of an oxygen cyllinder in the US?

Green

Why are compressed gas tanks not stored upright when unsecured?

In case they blast off!

What are the units used to denote flow in an anesthesia machine flowmeter?

What is the working range in small animal?

L/min

0.2-5 L/min

What does activation of the oxygen flush valve do to the anesthetic concentration in a circle system?

Bypass vaporizer -> dilute concentration -> high flow of oxygen into breathing circuit

Why is it not recommended to use the flush valve while connected to a patient utilizing a small volume breathing circuit?

Barotrauma (buildup of pressure)

What is the purpose of an anesthesia vaporizer?

Turn liquid inhalant into vaporized form

True or False: Any agent can be used in any modern vaporizer.

False! They are AGENT-SPECIFIC to iso or sevo.

What is the common outflow for both the vaporizer and oxygen flush?

Fresh gas outlet (flowmeter of gas+/- inhalant, oxygen flush)

Where does a breathing circuit connect to an anesthesia machine?

Fresh gas outlet

What are the FOUR purposes of the breathing circuit?

1. Deliver gas mixture to patient

2. Remove carbon dioxide from patient

3. Secure airway

4. Provide ventilation

What are the FOUR classifications of breathing circuits and how are they categorized?

1. Open (not clinically used)

2. Semi-open (non-rebreathing system)

3. Semi-closed (circle)

4. Closed (circle)

What TWO features make the mechanism by which a non-rebreathing system eliminates carbon dioxide unique?

1. No recirculation of expired air

2. High fresh gas flow (washes out the CO2)

Name the SIX major components of the circle rebreathing system.

1. Fresh gas inlet (connects to fresh gas outlet)

2. One way valve (move gas one direction)

3. Breathing tube/Y-piece

4. CO2 absorber

5. APL (pop-off valve)

6. Reservoir bag

What size animal should be reserved for a non-rebreathing system?

<3 kg

Name FOUR advantages of a non-rebreathing circuit over a circle system.

1. Low resistance

2. Simple (low failure rate)

3. No distance limitation

4. Immediate control of inspired concentration

Name FOUR disadvantages of a non-rebreathing circuit over a circle system.

1. High fresh gas flow (economic issue)

2. Loss of heat and moisture

3. Environmental pollution

4. Harder to control under ventilation

Name FOUR advantages of a circle system over a non-rebreathing circuit.

1. Low fresh gas flow

2. Preservation of heat and moisture

3. Less environmental pollution

4. Easier to ventilate

Name FOUR disadvantages of a circle system over a non-rebreathing circuit.

1. Higher resistance (hypoventilation)

2. Complex (higher failure rate)

3. Constrained to distance

4. Equilibrate circuit with new concentrations

What happens to a patient when the valves of a circle system fail?

Rapid rebreathing of CO2 -> hypercapnia and resp acidosis

What is the purpose of sodasorb?

Scavenges CO2 from expired gas before returning it to a patient in a circle breathing system

What are the two byproducts of the CO2 reaction with Sodasorb?

Heat and water

What are the three ways to tell when sodasorb is expired?

1. Inspired CO2 by capnography

2. Indicator color change (purple)

3. Lack of heat in canister

What happens to the color indicator when sodasorb is released?

Reverts during rest- do not wait to change

What are the two purposes of the adjustable pressure limiting (APL/pop-off) valve?

1. Vents excess gas from circuit

2. Closed to provide

What are the two purposes of the reservoir bag?

1. Provide excess capacity to build into breaths

2. Provide manual ventilation

What makes a semi-closed and closed anesthesia circuit different?

Semi-Closed: partial rebreathing; high FGF; open APL

Closed: full rebreathing; low FGF; closed APL

Name THREE advantages of a closed over a semi-closed system.

1. Conserve gas

2. Preserve heat/moisture

3. No environmental pollution

Name THREE disadvantages of a closed over a semi-closed system.

1. Equilibration

2. Accuracy of vaporizer

3. Monitoring

How would you determine when an activated charcoal canister needs to be replaced?

Weight gain

What are the FOUR purposes of an ET tube?

1. Provide patent airway

2. Reduce aspiration risk

3. Aid in positive pressure

4. Allows expired gas sampling

What is the purpose of the Murphy eye on an ET tube?

Secondary, alternative vent for gas flow

What is the purpose for the cuff on an ET tube?

Reduce leakage for positive pressure ventilation

Name TWO reasons not to put excessive pressure in an ET cuff.

1. Tracheal ischemia

2. Severe, long-term tracheal injury

How much should you inflate the ET cuff in small dog/cats, large dogs, and horses?

Small dog/cat: 10-15 cm

Large dog: 15-20 cm

Horse: 25-40 cm

What are the THREE advantages of inhalant anesthetics?

1. Predictable/rapid adjustment

2. Part of complex system

3. Inexpensive after initial investment

What FOUR things make up the complex system that is needed for inhalant anesthetics?

1. Pressure vaporizer

2. O2 source

3. Ability to control ventilation

4. Removal of CO2

Name the order of events that occurs when giving a patient inhalant anesthesia. (6)

Unconscious -> muscle relaxation -> loss of nociception (feeling) -> loss of sympathetic response -> respiratory distress -> cardiovascular collapse

What are the FOUR major disadvantages of inhalant anesthetics?

1. Narrow therapeutic window

2. Expensive initial investment

3. Does not block nociceptive input

4. Side effect (CV collapse and respiratory distress)

What is the primary advantage of iso over sevo?

Less expensive

What is the primary advantage of sevo over iso?

Less soluble (quicker up/down or recovery)

True or False: Both iso and sevo are liquid at room temp and administered as a vapor.

True!

Why does an inhalant anesthetics with a high vapor pressure pose a risk to a patient?

Delivered very quickly -> can lead to respiratory depression/hypotension/apnea (higher overdose risk)

What is the clinically useful way to record the amount of inhalant being administered to a patient?

Volume % (concentration of one gas in mixture)

___: the amount of pressure exerted by one gas if occupied the space alone

Partial pressure

How do you calculate the partial pressure of a gas?

% volume x pressure (total)

What controls the clinical effect of inhalants on the patient?

PC (solubility)

How do changes in partial pressure effect inhalant anesthetics and their clinical application?

Driving force in inhalants -> determines how quick goes to sleep

What clinical property is dictated by blood:gas solubility?

Induction/recovery

What clinical property is dictated by oil:gas solubility?

Potency

What would a lower blood:gas ratio indicate?

Fast induction/recovery with fast changes in depth

(less soluble in blood means faster changes)

What would a lower oil:gas ratio indicate?

Less lipid soluble (more concentration needed for effect)

What inhalant has a blood:gas PC of 0.6 and oil:gas PC of 50?

Sevoflurane

What inhalant has a blood:gas PC of 1.4 and oil:gas PC of 99?

Isoflurane

Does sevoflurane have better induction/recovery or potency? Why?

Sevoflurane- lower blood:gas (faster induction/recovery)

Does isoflurane have better induction/recovery or potency? Why?

Isoflurane- higher oil:gas (more potent- need less for same effect)

Know how to do all the math on Inhalants 3.

ok

What is the formula for time constant?

Volume/flow

How can you predict rate of change based on the two major time constants?

1 time change = 63%

4 time changes = 98%

Time constants are only in (open/closed) systems.

Closed

Rank the FOUR order distributions of inhalants to the four tissue groups from first to last saturated.

Vessel rich (brain/viscera) -> muscle -> fat -> vessel poor (bone/cartilage)

What is the undesired effect caused by distribution of inhalant to tissues other than the vessel rich group?

Delayed uptake to other groups -> delays equilibrium

What are the TWO factors that affect the delivery of inhaled anesthetics to the alveoli and how changes in these factors will change the clinical effect?

1. Inspired concentration (increased leads to increased alveolar partial pressure -> faster induction)

2. Alveolar ventilation (faster induction)

What THREE factors affect removal of inhaled anesthetics from the alveoli and how changes in these factors will change the clinical effect?

1. Blood:gas PC (lower = faster anesthesia control)

2. Cardiac output (lower CO speeds up induction)

3. Alveolar-venous concentration diff (low speeds induction)

What measurable variable reflects partial pressure of an inhalant present in the brain?

End tidal partial pressure

What is the MOA of inhalants?

GOT YA! They don't know. Idiots.

What THREE potential things are proposed MOAs of inhalants in the thalamus and cortex?

1. GABA

2. K+ channels

3. Glycine receptors

___: the standard infex of potency used to compare inhalants and to predict effect

MAC (minimum laveolar concentration)

MAC is an index of ---.

Potency

What THREE factors make MAC difficult to translate from research to clinical settings?

1. Only in inhalant

2. Healthy animals

3. MAC is an average

What are the MAC of isoflurance and sevoflurane?

Iso: 1.3-1.6

Sevo: 2.3-2.6

Based on MAC, which inhalant is the most potent?

Sevoflurane (needs smallest MAC to reach effect)

What are TWO things that increase MAC?

1. Hyperthermia

2. CNS stimulants (amphetamines)

What FOUR things decrease MAC?

1. Late-term pregnancy

2. Hypothermia

3. Extremes of age

4. Other agents (premed inj)

Name SEVEN things that do not change MAC.

1. Duration of anesthesia

2. Gender

3. Anticholinergics

4. pH

5. PaCO2

6. PaO2

7. Blood pressure

Name the FOUR potential benefits of inhalants and place them in order of increasing dose.

Unconsciousness -> Muscle relaxation -> Loss of response to nociception -> Loss of sympathetic response

The major cardiovascular effect of inhalants is the dose dependent drop in -------, which decreases CO and SVR.

Blood pressure

What are the TWO major respiratory side effects of volatile anesthetics?

1. Decrease minute ventilation

2. Decrease response to O2 (resp acidosis)

Malignant hyperthermia involves the inability to resorb what?>

Ca2+

What FIVE clinical signs are most associated with malignant hyperthermia?

1. Increase muscle activity

2. Uncontrolled hyperthermia

3. Uncontrolled CO2

4. Acidosis

5. Arrhythmia

Malignant hyperthermia is thought to be genetically related to a defect in --- and is what seen in which animal?

RYR1

Pigs

True or False: Modern inhalants are metabolized by the body.

False! They are NOT metabolized by the body.

What is the regulatory limit for workplace eposure to waste anesthetic gases?

<2 ppm (if smelled, it's much higher)

What population is at greatest risk for health problems due to exposure to waste anesthetic gases?

Healthcare professionals (especially preggers)

What are the FOUR goals of small animal anesthesia?

1. Unconsciousness

2. Loss of movement

3. Loss of nociception

4. Homeostasis

--- consists of age, breed, and sex.

Signalment

What is the 8 step plan of small animal drug selection?

1. Asses patient

2. NSAID

3. Sedative

4. Opioid

5. Induction

6. Maintenance

7. Intra-operative analgesia

8. Post-op analgesia

Why is anesthetizing young (<1 1 weeks) and old (>80% life expectancy) different than middle aged healthy patients?

Delayed metabolism of drug

What FOUR major vital signs are assessed in a physical exam?

1. Temp

2. Pulse rate

3. Respiratory rate

4. Pain

What pre-anesthetic diagnostic test has been shown to reduce anesthetic mortality in otherwise healthy patients?

DIDNT GET THIS ONE SOMEONE TELL ME

What are the laboratory findings that are DIRECT indicators of heaptic function which may indicate delayed drug metabolism?

Best= bile acids

Secondary= pseudofunction (BUN, glucose, cholesterol, albumin) ammonia, bilirubin

What ASA classification is a healthy patient for an elective procedure (spay, neuter, dental)?

ASA I

What ASA classification is a systemically healthy or mildly systemic patient undergoing a necessary procedure (fracture, mass removal)?

ASA II

What ASA classification is a severe but stable systemic disease (renal failure, CHF, controlled DM)?

ASA III

What ASA classification is a systemically decompensated patient with a constant threat to life (GDV, hemoabdomen, septic)?

ASA IV

What ASA classification is morbid with a life expectancy <24 hours (shock, trauma)?

ASA V

What are THREE advantages for incorporating NSAIDs into an anesthetic plan?

1. Long acting

2. Central and peripheral effects

3. No reaction with anesthetics