inhalation, local, and topical anesthetics

Question 1

Ideal Properties

Answer 1

Produce unconsciousness, analgesia, muscle relaxation, amnesia; brief pleasant induction/emergence; easily adjustable depth; minimal adverse effects; large safety margin

Question 2

Balanced Anesthesia

Answer 2

Combines inhalation agents with IV drugs (opioids, CNS depressants) for optimal effect

Question 3

Minimum Alveolar Concentration (MAC)

Answer 3

Measure of potency; low MAC = high potency

Question 4

Uptake

Answer 4

From lungs; faster uptake with greater concentration

Question 5

Distribution

Answer 5

Based on regional blood flow; rapid to brain, heart, liver, kidneys

Question 6

Elimination

Answer 6

Mostly via lungs (exhalation); minimal liver metabolism

Question 7

Adverse Effects of inhalation anesthetics

Answer 7

Respiratory/cardiac depression, aspiration risk, malignant hyperthermia (except nitrous oxide)

Question 8

Malignant Hyperthermia Treatment

Answer 8

Stop succinylcholine, cool the patient, IV dantrolene

Question 9

Adjunct Medications – Preanesthesia

Answer 9

Benzodiazepines, opioids, clonidine, anticholinergics (↓ secretions, prevent bradycardia)

Question 10

Neuromuscular Blockers (used during)

Answer 10

Succinylcholine, pancuronium – relax skeletal & respiratory muscles

Question 11

Postanesthesia Meds

Answer 11

Analgesics (opioids, acetaminophen), antiemetics (ondansetron, promethazine, droperidol), muscarinic antagonists (e.g., bethanechol to stimulate urination)

Question 12

Categories of Inhalation Agents

Answer 12

1. Volatile liquids (high potency, low analgesia) 2. Gases (low potency, high analgesia)

Question 13

Volatile Liquid Characteristics

Answer 13

Lipid-soluble, cross BBB, vaporized easily at low temp/pressure, delivered via anesthesia machine, used to induce/maintain deep anesthesia

Question 14

Common Volatile Agents

Answer 14

Isoflurane (Forane), Desflurane (Suprane), Sevoflurane (Ultane) – all have high potency, fast induction/emergence, but low analgesia & weak muscle relaxation

Question 15

Volatile Agent AEs

Answer 15

Hypotension, respiratory depression, nausea/vomiting, ↓ urine output

Question 16

Sevoflurane Advantage

Answer 16

Rapid induction/emergence – great for outpatient procedures

Question 17

Nitrous Oxide (“Laughing Gas”)

Answer 17

Low anesthetic potency, high analgesic effect; never used alone; 20% = morphine strength; commonly used adjunct

Question 18

Nitrous Oxide AEs

Answer 18

Post-op nausea and vomiting (PONV)

Question 19

Definition of local anesthetics

Answer 19

Block pain transmission in peripheral nerves by blocking sodium channels.

Question 20

Effect of local anesthetics

Answer 20

Loss of sensation to small or limited area near site of administration.

Question 21

Advantages of local anesthetics

Answer 21

Avoids N/V, tremors, anxiety associated with general anesthesia. Minor risks compared to GA.

Question 22

Delivery Methods of local anesthetics

Answer 22

• Topical (surface)
• Infiltration (directly to site)
• Nerve block (away from site)
• IV Regional (for extremities)
• Epidural
• Spinal

Question 23

Limitations of local anesthetics

Answer 23

• Less control over onset/duration
• Depends on drug’s diffusion from application site
• Termination depends on blood flow to the region

Question 24

Duration Extension of local anesthetics

Answer 24

Epinephrine (vasoconstrictor) may be added to:
- Limit blood loss
- Prolong duration
- Reduce systemic distribution

Question 25

Classes of local anesthetics

Answer 25

- Esters - Amides (lower incidence of allergic reactions)

Question 26

Adverse Effects of local anesthetics

Answer 26

- CNS: excitation followed by depression - CV: bradycardia, heart block, ↓contractility, cardiac arrest, hypotension - Allergic reactions - May prolong labor - Methemoglobinemia

Question 27

Ester Examples

Answer 27

- Procaine [Novocain] • Only injection • Epinephrine delays absorption • Now seldom used - Benzocaine (topical) - Tetracaine (topical) - Cocaine (first widely used, topical)

Question 28

Amide Examples

Answer 28

- Lidocaine [Xylocaine] • Epinephrine prolongs effect • Rare allergic reaction • CNS/CV toxicity possible • Hepatic metabolism • Also treats dysrhythmias • Forms: cream, ointment, jelly, solution, aerosol, patch - Dibucaine [Nupercainal]

Question 29

Other Topicals

Answer 29

- Dyclonine [Sucrets spray] - Pramoxine [Tronothane]

Question 30

Topical Use Safety Tips

Answer 30

- Use smallest amount needed - Avoid large areas - Avoid broken/irritated skin - Avoid wrapping, heating, or strenuous exercise at application site