Anesthetics

💉 GENERAL ANESTHETICS - BASICS

Q: What are the 4 conditions general anesthetics produce?
A: Unconsciousness, sedation, analgesia, amnesia.

Q: What’s the difference between general and local anesthetics?
A: General: affects whole CNS. Local: numbs a specific area.

⚡️MECHANISM OF ACTION

Q: Which receptors do general anesthetics affect?
A:

  • GABA receptors: ↑ inhibition (CNS depression)

  • NMDA receptors: ↓ excitation (glutamate block)

🩸PARENTERAL ANESTHETICS (IV)
Mnemonic: “The Pretty Elegant Karate”
Thiopental, Propofol, Etomidate, Ketamine

THIOPENTAL (Barbiturate)
Q: Uses?
A: Induction, ↓ ICP
Q: Caution?
A: Bronchoconstriction (not for asthmatics)
Q: Side effects?
A: Hypotension, respiratory depression, histamine release

MIDAZOLAM (Benzodiazepine)
Q: Side effects?
A: Amnesia, sedation, post-op respiratory depression
Q: Antidote?
A: Flumazenil

PROPOFOL
Q: Why popular for outpatient?
A: Fast recovery
Q: Serious risk?
A: Propofol infusion syndrome (bradycardia, acidosis, fatty liver)

ETOMIDATE
Q: Best for which clients?
A: CV disease, CAD, hypovolemia (less ↓ BP)
Q: Main risk?
A: Adrenal suppression

KETAMINE
Q: Main action?
A: NMDA blocker
Q: Good for who?
A: Asthmatics, hypotensive patients
Q: Unique effects?
A: Dissociative anesthesia, hallucinations

🌬INHALED ANESTHETICS
Mnemonic: “N2O and the -ANEs”

NITROUS OXIDE (N2O)
Q: Properties?
A: Fast onset/offset, weak anesthetic
Q: Unique effects?
A: Analgesia, “second gas effect”, expands closed spaces
Q: Safe?
A: Yes – only inhaled anesthetic that doesn’t cause malignant hyperthermia

HALOGENATED ANESTHETICS (-ane suffix)
Drugs: Halothane, Enflurane, Methoxyflurane, Desflurane

All cause:

  • CV & respiratory depression

  • ↑ ICP

  • Malignant hyperthermia (⚠ emergency)

HALOTHANE
Q: Side effect?
A: Hepatotoxicity (“halo = liver rot”)

METHOXYFLURANE
Q: Side effect?
A: Nephrotoxicity (“ox chewing kidney”)

ENFLURANE
Q: Contraindication?
A: Epilepsy (↓ seizure threshold)

DESFLURANE
Q: Side effects?
A: Pungent smell, airway irritation

🔥 MALIGNANT HYPERTHERMIA
Q: Triggered by?
A: All halogenated inhaled anesthetics + succinylcholine
Q: Symptoms?
A: Muscle rigidity, ↑ temp, acidosis, tachycardia
Q: Treatment?
A: Dantrolene

📚 NURSING TIPS

Q: Monitor for?
A: Respiratory rate, BP, signs of MH, O2 sat
Q: Teaching point?
A: Watch for delayed emergence, memory loss, sedation

💊 LOCAL ANESTHETIC BASIC CONCEPTS

Q: What is the main use of local anesthetics?
A: Reversibly block pain sensation in a specific body part.

Q: Common suffix for local anesthetics?
A: "-caine" (e.g., lidocaine, tetracaine)

Q: Main mechanism of action?
A: Block voltage-gated Na⁺ channels → prevent action potentials.

🔍 CLASSIFICATION: ESTERS vs AMIDES

Q: How do you tell esters vs amides apart by name?
A:

  • Esters have 1 “i” in their name (e.g., procaine).

  • Amides have 2 “i”s (e.g., lidocaine).

MNEMONIC: Salt Mine Story

  • Miner = blocks inactive Na⁺ channels

  • Acid puddle = acidic tissue (↓ drug entry)

  • Blanket + skinny miner = small, myelinated nerves affected first

  • Easter Island head = esters

  • Gold Midas statue = amides

🌴 ESTER ANESTHETICS

Q: Drugs in ester class?
A: Cocaine, benzocaine, procaine, tetracaine

Q: Cocaine unique effect?
A: Blocks reuptake of catecholamines + dopamine → ↑ BP, euphoria

Q: Benzocaine risk?
A: Methemoglobinemia → chocolate-colored blood, cyanosis

Q: Tetracaine use?
A: Long-acting; used in spinal/corneal anesthesia

Q: Procaine features?
A: Short-acting; high risk for CNS & CV side effects

💛 AMIDE ANESTHETICS

Q: Drugs in amide class?
A: Lidocaine, mepivacaine, bupivacaine

Q: Lidocaine use?
A: Most common; intermediate duration; all types of anesthesia

Q: Mepivacaine risk?
A: Contraindicated in newborns + pregnant women

Q: Bupivacaine key caution?
A: Cardiotoxic – can cause myocardial depression

📉 EFFECT ORDER (from first to last)
Q: What functions are blocked in order by local anesthetics?
A:

  1. Pain

  2. Temperature

  3. Touch

  4. Pressure

  5. Motor

💥 SIDE EFFECTS – All Local Anesthetics

Q: CNS side effects?
A: Early: restlessness, seizures → Later: CNS depression, coma

Q: CV effects?
A: Bradycardia, ↓ CO, vasodilation → hypotension

📍ADMINISTRATION NOTES

Q: Why is epinephrine often co-administered?
A: Vasoconstricts → slows absorption → ↑ duration, ↓ toxicity

Q: What reduces effectiveness of local anesthetics?
A: Acidic environments (e.g., infection, hypoxia)

🧠 TEST TIPS

Q: What if patient is allergic to esters?
A: Use an amide (and vice versa)

Q: What class is safest for pregnant patients?
A: Lidocaine – most commonly used and safestfor obstetric anesthesia, as it has a well-established safety profile.