General Anesthesia

Question 1

Name the 4 Inhaled Anesthetic Agents.

Answer 1

1) NITROUS OXIDE
2) DESFLURANE
3) SEVOFLURANE
4) ISOFLURANE

Question 2

Name the 4 Intravenous Anesthetic Agents.

Answer 2

1) PROPOFOL
2) ETOMIDATE
3) KETAMINE
4) DEXMEDETOMIDINE

Question 3

What are the 5 Major effects of a general anesthetic?

Answer 3

1) Unconsciousness
2) Amnesia
3) Analgesia
4) Attenuation of Autonomic Reflexes
5) Skeletal Muscle Relaxation

Question 4

What are the 3 conditions of the IDEAL general anesthetic?

Answer 4

1) RAPID smooth loss of consciousness
2) RAPID reversal on discontinuation
3) WIDE margin of safety

Question 5

What is CONSCIOUS SEDATION?

Answer 5

CONSCIOUS SEDATION (3 glasses of wine analogy)

1) AMOUNT - MINIMAL amount of amnestic and opioid
2) PATIENT INTERACTION - Still able to converse, respond to stimlui and commands
3) ABC - Able to protect airway and maintain ventilation

Question 6

What is the continuum of conscious sedation -> General anesthesia?

Answer 6

Decrease in any of the 3 conditions of conscious sedation (Low amount, pt still able to interact and respond to stimuli, maintain airway and ventilation)

Question 7

What condition distinctly differentiates SEDATION from GENERAL ANESTHESIA?

Answer 7

When the pt has LOST the ability to protect the airway and maintain normal ventilation
General anesthesia is actually PREFERRED by operators bec immobility/unresponsiveness to protecting the airway (e.g. aspirating, vomiting) is desired [Prevents potential pneumonitis]

Question 8

What is BALANCED ANESTHESIA?

Answer 8

Utilizing SMALL doses of multiple agents (Inhaled, IV, Opioids, Benzodiazepines, Neuromuscular blocking drugs) to MINIMIZE side effects and MAXIMIZE efficacy

Question 9

GASEOUS vs VOLATILE: What is the one commonly used gaseous anesthetic?

Answer 9

NITROUS OXIDE - Gaseous inhaled anesthetic (Gas at room temperature) Has GOOD Amnestic, and analgesic actions

Question 10

GASEOUS vs VOLATILE: Is N2O inhaled agent used alone?

Answer 10

NO, almost ALWAYS used in addition to other agents

Question 10

GASEOUS vs VOLATILE: What are the 3 volatile inhaled agents used?

Answer 10

VOLATILE - Liquid at room temperature

1) Desflurane
2) Isoflurane
3) Sevoflurane

Question 11

GASEOUS vs VOLATILE: What is the chemical structure of volatile inhaled agents? What is its importance?

Answer 11

D,I,S are FLUORINATED ethers - Fluoride addition stabilizes the ether -> Prevents ether flammability

Question 12

INHALED ANESTHETIC ONSET: What is the major factor determining the ONSET of an INHALED anesthetic?

Answer 12

1) HIGH Fa - Alveolar fraction of anesthetic to its target organ (CNS) or Alveolar partial pressure

Question 13

INHALED ANESTHETIC ONSET: How does the anesthesiologist control for a HIGH Fa (alveolar fraction) to CNS? (2)

Answer 13

1) HIGH Fi - Inspired fraction or partial pressure (vaporizer reading)
2) HIGH ALVEOLAR VENTILATION - High respiration rate of the pt

Question 14

INHALED ANESTHETIC ONSET: What is the other factor that the anesthesiologist can NOT control for but still contributes to a HIGH Fa?

Answer 14

LOW SOLUBILITY (INSOLUBLE) of Inhaled Agent (Blood: Gas partition coefficient) 
*Solubility is INVERSELY proportional to onset*

Question 15

INHALED ANESTHETIC ONSET: Rank the onset of the inhaled anesthetics based on solubility.

Answer 15

N2O (Least soluble) > DESFLURANE > SEVOFLURANE > ISOFLURANE (Most soluble)
“No doctor sounds ill”

Question 16

INHALED ANESTHETIC EMERGENCE: What is the Fi during emergence

Answer 16

ZERO - No more of the anesthetic is being delivered to the pt

Question 17

INHALED ANESTHETIC EMERGENCE: What is the major determining factor of an inhaled anesthetic’s emergence? What is a minor factor?

Answer 17

1) MAJOR: Alveolar Ventilation - The quicker the pt breathes, the more the gas can be removed from the lungs
2) MINOR: Metabolism

Question 18

What is MAC? What does it measure?

Answer 18

Minimal Alveolar Concentration - Measures potency

Ex: 1MAC&raquo_space; 10MAC in potency

Question 19

How is MAC experimentally determined?

Answer 19

Basically P50 - ALVEOLAR partial pressure of the inhaled anesthetic at which 50% of the population of non-muscle relaxed pts remain immobile at skin incision

Question 20

What is the effect of inhaled agents on major organ systems (CV, Respiratory, Hepatic, Uterine SM)

Answer 20

1) CV: DECREASE BP (Due to decreased SVR and negative inotropy)
2) Respiratory: Very shallow rapid breathing, INCREASED RR, DECREASED Vt = Decrease in minute ventilation (Respiratory Minute Volume)
* *Respiratory minute volume (minute ventilation) = Vt * RR
3) Hepatic: DECREASED Portal Vein flow but increase in liver enzymes are rarely seen
4) Uterine SM: DECREASED Uterine tone (Helpful for C section- can deliver baby via small incision) BUT potential painful risk due to INCREASED Uterine bleeding

Question 21

What is malignant hyperthermia (MH)?

Answer 21

Rare hypermetabolic syndrome that presents in GENETICALLY susceptible pts after toxicity due to exposure of triggering agents (Volatile inhaled agents + Succinylcholine)

Question 22

What are the top 4 triggering agents that induce MH?

Answer 22

1-3) VOLATILE AGENTS - Desflurane + Sevoflurane + Isoflurane

4) Succinylcholine

Question 23

What is the physiological event of MH?

Answer 23

Decrease in Ca2+ reuptake from the sarcoplasmic reticulum -> Excess Ca2+ buildup -> Prolonged muscle contraction

Question 24

What are the 4 resulting events of MH? (4 H's)

Answer 24

1) HYPOXIA - Increased BMR 2) HYPERCAPNIA - Increased metabolism 3) HYPERTHERMIA - Feverish 4) HYPERKALEMIA - Rupture of constantly contracting cells

Question 25

What is the antidote of MH? What is its mechanism of action?

Answer 25

DANTROLENE - Inhibits Ca2+ release from the sarcoplasmic reticulum (Very work intensive and time intensive, very short shelf-life)

Question 26

What is the PREFERRED method of ANESTHETIC INDUCTION?

Answer 26

IV

Question 27

IV (PROPOFOL/ ETOMIDATE/ KETAMINE): What is the nature of the onset of these IV anesthetics?

Answer 27

RAPID ONSET OF ACTION These three IV agents are LIPOPHILIC -> Preferentially partitions into highly perfused lipophilic tissues (Brain + Spinal cord)

Question 28

IV (PROPOFOL/ ETOMIDATE/ KETAMINE): What is the nature of emergence of these three IV anesthetics?

Answer 28

RAPID EMERGENCE - Based on concentration gradient IV anesthetics will rapidly redistribute from highly perfused tissues (e.g. brain) -> Lean tissues = Quick offset of action RAPID LIVER METABOLISM (occurs later)

Question 29

What is context sensitive half time? Is a high or low context sensitive half time desired?

Answer 29

Elimination half time after a prolonged continuous infusion | LOW Context sensitive half time is desired

Question 30

IV AGENTS: What is the mechanism of action of PROPOFOL and ETOMIDATE?

Answer 30

GABA Agonist - Promote synaptic inhibitory neurotransmission

Question 31

IV AGENTS: What are the amnestic and analgesic properties of PROPOFOL?

Answer 31

Non-analgesic | AMNESTIC

Question 32

IV AGENTS: What is the effect of PROPOFOL on CV, Respiratory, and Nausea?

Answer 32

CV: Vasodilatory, negatively inotropic - Do NOT want to use on a pt who has cardiac myopathy Respiratory: Decreased RR, Decreased Vt, Decreased Minute Volume, DECREASED upper airway reflexes - can intraoperatively vomit -> risk for aspirative pneumonitis Antiemetic: Reduces nausea

Question 33

IV AGENTS: What is the use of ETOMIDATE?

Answer 33

Induction | Short Sedation

Question 34

IV AGENTS: Which pt pool is it most beneficial to use ETOMIDATE?

Answer 34

Pts who have heart pathology OR can go into shock | Reason: ETOMIDATE has minimal hemodynamic effect (HR, BP, inotropy)

Question 35

IV AGENTS: **Why can you NOT use ETOMIDATE for PROLONGED SEDATION?

Answer 35

Because Etomidate has a dose-dependent inhibition of 11-b-hydroxylase (important for cholesterol -> cortisol) = INHIBITION OF CORTISOL PRODUCTION

Question 36

IV AGENTS: What are two distinct uncomfortable factors of using ETOMIDATE?

Answer 36

1) Burns on injection | 2) Post-operative nausea/vomiting (Also known as "vomidate")

Question 37

IV AGENTS: What is the mechanism of action of KETAMINE?

Answer 37

NMDA Receptor ANTAGONIST

Question 38

IV AGENTS: What is the anesthesia state after administering KETAMINE?

Answer 38

Dissociative Anesthesia (Cataleptic State) With HORIZONTAL NYSTAGMUS - Not complete unconsciousness

Question 39

IV AGENTS: What is the analgesic property of KETAMINE?

Answer 39

YES, ANALGESIC - Very helpful to treat burns

Question 40

IV AGENTS: What is the effect of KETAMINE on CV, Respiratory, and upper airway reflexes

Answer 40

CV: INCREASED HR, Inotropy, and CO Respiratory: MINIMAL if any respiratory depression Upper Airway Reflexes: Preserved

Question 41

IV AGENTS: What are the negative effects of using KETAMINE?

Answer 41

1) Hallucinations and unpleasant emergence may occur -> Therefore, coadminstration of benzodiazepine is recommended 2) INCREASED Lacrimations and Secretions (saliva)

Question 42

IV AGENTS: What is KETAMINE'S potential drug interaction that can be utilized with regards to opioids?

Answer 42

Ketamine in SUBANALGESIC doses can LIMIT or REVERSE opioid tolerance

Question 43

IV AGENTS: What is the use of DEXMEDETOMIDINE?

Answer 43

Sedation | Adjunct to General Anesthesia

Question 44

IV AGENTS: What is the mechanism of action of DEXMEDETOMIDINE?

Answer 44

Alpha-2 agonist receptors located in the locus ceruleus and spinal cord

Question 45

IV AGENTS: What are the sedative and analgesic properties of DEXMEDETOMIDINE?

Answer 45

Yes, sedative | Yes, analgesic

Question 46

IV AGENTS: Which two IV agents are analgesic, and which two are NON-analgesic

Answer 46

NON-analgesic: Propofol + Etomidate | Analgesic: Ketamine + Dexmedetomidine

Question 47

IV AGENTS: What is the effect of DEXMEDETOMIDINE on CV and respiratory?

Answer 47

CV: DECREASED BP, HR, CO Respiratory: Preserved respiratory drive

Question 48

IV AGENTS: Does the context sensitive half time of DEXMEDETOMIDINE make it a preferable drug or non-preferred?

Answer 48

NON-PREFERRED | Context sensitive time of dexmedetomidine is SIGNIFICANTLY INCREASED after 8hrs of infusion

Question 50

IV AGENTS: What are the respiratory effects of all the inhaled agents PROPOFOL, ETOMIDATE, KETAMINE, DEXMEDETOMIDIINE?

Answer 50

Propofol + Etomidate = Respiratory Depressants | Ketamine + Dexmedetomidine = Preserved Respiratory Drive

Question 58

IV AGENTS: What is the CV effect of PROPOFOL, DEXMEDETOMIDINE, ETOMIDATE, and KETAMINE?

Answer 58

Propofol + Dexmedetomidine - DECREASE CO Etomidate - Neutral, no hemodynamic effect Ketamine - INCREASE CO