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Pharmacology > General Anesthesia > Flashcards

General Anesthesia Flashcards

1
Q

The state of “general anesthesia” includes:

A
  • Analgesia
  • Amnesia
  • Loss of consciousness
  • Suppression of reflexes
  • Skeletal muscle relaxant
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2
Q

Balanced anesthesia

A

Used of several drugs to produce an anesthetic state

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3
Q

Types of General Anesthesia

A
  1. Inhaled anesthesia
    - Gases
    - Volatile halogenated hydrocarbons
  2. IV anesthesia
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4
Q

Common features of Inhaled anesthetics

A
  • Inc brain perfusion
  • Bronchodilation
  • Dec minute ventilation
  • Potency correlates w/ liposolubility
  • Rate of onset inversely correlates to Blood solubility
  • Recovery is due to redistribution from the brain
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5
Q

Minimum Alveolar Concentration (MAC)

A

Conc. that results in immobility in 50% of pts. when exposed to a noxious stimulation

Greater the MAC — Lower the Potency
Lower the MAC — Greater the Potency

NB: MAC values are additive

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6
Q

MOA of Inhaled Anesthetics

A
  • +ve modulators of GABAa & glycine receptors
  • Inhibit nicotinic receptors

Direct interaction w/ ligand gated ion channel

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7
Q

Meyer-Overton Correlation

A

Oil: Gas Partition co-efficient —-ratio of conc. of a compound in one solvent to the conc. in another solvent

-Measure of liposolubility
High liposolubility = High potency

High oil:gas = Low MAC = High potency

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8
Q

Factors that determines the rate of anesthesia induction

A
  • Solubility of anesthesia (Low Blood: Gas = Faster onset of action)
  • Conc. in inspired air (Higher = Faster rate of induction)
  • Pulm. ventilation rate (Higher = Inc rate of induction)
  • Pulm. blood flow (Higher = Dec rate of induction)
  • AV conc. gradient (Higher = Dec rate of induction)
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9
Q

Blood: Gas Partition Coefficient

A

Relative solubility of an anesthetic in blood compared to air

  • Index of Solubility
  • Inverse relationship between blood solubility & rate of rise of its tension in arterial blood

Low Blood: Gas = Fast onset of anesthetic

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10
Q

Increases in the rate of induction

A
  • Inc in anesthetic conc
  • Inc in ventilation rate
  • Dec Pulmonary blood flow –> Dec Cardiac output
  • Inc AV conc (Inc in arterial blood & tissue)
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11
Q

Elimination of inhalation anesthetics

A

Low Blood & tissue solubility - Recovery mirrors induction (regardless of duration of administration)

High blood & tissue solubility - Recovery depends on duration of anesthetic administration (bc anesthetic accumulates in fat)

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12
Q

CVS effects of Inhaled anesthetics

A
  1. Depress normal contractility (Dose-dependent)
  2. Vasodilation –> Dec MAP
    - Halothane & Enflurane - Dec MAP by myocardial depression; little effect on PVR
    - Isoflurane, Desflurane & Sevoflurane - Vasodilation; little effect on CO (Better choice for pts. w/ impaired myocardial function + less risk of ventricular arrhythmias)
  3. Sensitization of Myocardium to circulating catecholamines –> Ventricular arrhythmias
    - Halothane
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13
Q

Resp. effects of Inhaled Anesthetics

A
  • Bronchodilation
  • Resp. depressant

Mostly w/ Isoflurane & Enflurane
Least w/ N2O

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14
Q

CNS effects of Inhaled anesthetics

A
  • Inc ICP (least w/ N2O)
  • Tonic-clonic seizures @ high conc. (Enflurane)
  • EEG changes
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15
Q

Other effects of Inhaled Anesthetics

A

Inc V/P of cavity
- Avoid in pts. w/ pneumothorax, obstructed middle ear, air embolus, obstructed bowel, intra-ocular air bubble, pulmonary bulla & Intracranial air

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16
Q

Toxicities of Inhaled Anesthetics

A
  1. Hepatotoxicity
    - Halothane
  2. Nephrotoxicity
    - Methoxyflurane
  3. Malignant Hyperthermia
    - Halothane & Succinylcholine (Depolarizing skeletal muscle relaxant)
  4. Hematotoxicity (Megaloblastic anemia)
    - N2O chronic use
17
Q

Halothane-induced Hepatotoxicity

A

Can develop severe & life-threatening hepatitis

  • No specific treatment
  • Liver transplant may be needed
18
Q

Methoxyflurane-induced Nephrotoxicity

A

Due to fluoride released during metabolism

19
Q

Malignant Hyperthermia

A

AD disorder of skeletal muscles

- Main cause of death due to anesthesia

20
Q

CFs of Malignant Hyperthermia

A
  • tachycardia
  • HTN
  • Severe muscle rigidity
  • Hyperthermia
  • Hyperkalemia
  • Acidosis
  • Acute kidney failure (Myoglobinuria + Hyperkalemia)
21
Q

MOA of Malignant Hyperthermia

A

Defect in Ryanodine Receptor gene (RYR1) –> Unregulated Ca release from the SR –> Inc muscle contraction –> Heat

Depletion of O2 & ATP & Inc CO2 (aerobic) –> Switch to anaerobic –>Inc acidosis & lactate –> Depletion of energy stores –> Muscle fiber death –> Hyperkalemia & Myoglobinuria

22
Q

Treatment of Malignant hyperthermia

A

Dantrolene
- Blocks Ca2+ release form SR

  • Measures to dec body temp & restore electrolytes and acid-base balance
23
Q

How does the use of Succinylcholine & Halogenated anesthetic affect pts w/ Muscular dystrophies?

A

Can develop life-threatening Hyperkalemia & Rhabdomyolysis due to upregulation of extra-junctional Ach receptors depolarizing the whole cell

24
Q

What tests is used to establish susceptibility to Malignant hyperthermia?

A

Caffeine-halothane muscle Contracture test
- Muscle sample removed from thigh –> Halothane & caffeine response assessed

Genetic testing

25
Q

N2O-induced Hematotoxicity

A

Prolonged exposure to N2O –> Dec Methionine synthase activity –> Megaloblastic anemia

RF: Working in poorly ventilated dental operating suites

26
Q

IV Anesthesia (names)

A
  1. Propofol
  2. Ketamine
  3. Etomidate
  4. Barbiturates (Ultra-short acting)
    - Thiopental
    - Methohexital
27
Q

Use of ultra-short acting Barbiturates

A

Induction of anesthesia for short surgical procedures

28
Q

Metabolism of Ultra-short acting Barbiturates

A

Anesthetic effects are terminated by redistribution from brain to other tissues

Elimination from body requires hepatic metabolism

29
Q

Actions of Ultra-short Barbiturates

A
  • Dec ICP

- Do NOT produce analgesic

30
Q

AEs of Thiopental & Mathohexidate

A
  • Hyperalgesia
  • Apnea
  • Coughing
  • Chest wall spasm
  • Laryngospasm
  • Bronchospasm

Concern for asthmatics

31
Q

Actions of Propofol

A
  • Induction & maintenance of anesthesia
  • Antiemetic (Post-operative vomiting uncommon)
  • NO analgesia

Liver metabolism

32
Q

AEs of Propofol

A
  • Resp. depression
  • CV depression (Dose dependent)
  • Hypotension (Dec PVR)
  • Dec ICP
33
Q

Prodrug of Propofol

A

Fospropofol

34
Q

Actions of Etomidate

A
  • Anesthetic induction of pts. w/ RISK FOR HYPOTENSION

- NO analgesic effects

35
Q

AEs of Etomidate

A
  • Minimal CV & Resp depression
  • Dec ICP
  • Nausea & vomiting
  • Inhibits 11-beta-hydroxylase
  • Adrenal suppression (prolonged infusions)
36
Q

Actions of Ketamine

A

Dissociative anesthesia - Catatonia, amnesia, analgesia, w/ or w/o loss of consciousness

  • Blockade of NMDA receptors
  • Analgesic effects
  • CV stimulation
37
Q

AEs of Ketamine

A
  1. Inc ICP

2. “Emergence phenomena” - sensory & perceptual illusions & vivid dreams

38
Q

Drugs used to reduce “Emergence phenomena”

A
  • Diazepam
  • Midazolam
  • Propofol
39
Q

Adjuvant drugs to General anesthesia

A
  1. Benzo - Anxiolytic & Anterograde amnesia
  2. Opioids - Analgesic
  3. Neuromuscular blockers - Muscle relaxation
  4. Antiemetic (Ondansetron) - Post-op N&V
  5. Antimuscarinics
    - Scopolamine - Amnesic effect
    - Glycopyrrolate - Prevent salivation & bronchial secretions
    - Atropine - Prevent Bradycardia caused by inhalation agents & neuromuscular blockers

Pharmacology (16 decks)

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