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Flashcards in Inhaled Agents Deck (39):
1

What is the MOA of the inhaled anesthetics?

It is not completely understood, however, the Myer- Overton theory states that anesthesia occurs when a # of inhalation molecules dissolve in a lipid cell membrane which either inhibits gluatamate and aspartate or promotes GABA and glycine.  Absorption of anesthetic molecules expands the hydrophobic region within the cell membrane beyond a critical amount which distorts channels necessary for action potential and synthetic transmission.

2

Which Inhaled Agents are contraindicated in MH?

All of the Volatile anesthetics are contraindicated in MH.  Only N2O is considered safe.

3

What is the chemical structure and description of N2O?

It is the only inorganic anesthetic gas.  It is a gas at room temperature.  It is only inhaled agent that is not halogenated.  There is a double bond between two N atoms with a single bond from each to the O atom.

4

What are the Pharmacokinetics of N2O?

  • It is eliminated by exhalation
  • Biotransformation occurs with less than 1% hepatic metabolism
  • Fast on and fast off due to low BG coefficient
  • can be used to create 2nd gas effect for other IAs (turn on N2O @ 70% will increase concentration & uptake of other gases so you can decrease the MAC of the other agents.
  • 34x more soluble than N2

5

What are the side effects of N2O?

  • CNS
    • Increased CBF, ICP, and CMRO2.

    • Decreased cerebral activity, blunts cerebral autoregulation 

  • Neuromusclar
    • can cause skeletal muscle rigidity at Mac >1, potentiates the activity of NMB
  • Respiratory
    • Increased RR, Decreased TV, Increases PVR  & RAP- not a good drug for pt. with known pulm. htn, cor pulmonale, or significant lung disease
    • Unlike the other IA, it will cause BRONCHOCONSTRICTION
    • no change in resting PaCO2,
    • Decreased hypoxic drive
    • DIFFUSION HYPOXIA
  • CV
    • SNS stimulation, increased CVP,
    • no change in HR, BP, CO, SVR
    • epi induced arrhythmias
    • may reveal undiagnosed CAD
  • GI
    • NAUSEA/VOMITING
    • can cause bowel distention
  • Liver
    • decreased hepatic blood flow
  • Renal
    • Decreased RBF, GFR, UOP
  • Heme
    • inhibits B12, suppresses myelin formation and DNA synthesis in larger doses, BONE MARROW SUPPESSION, can impair response to infection
  • Other: 
    • unique: has some ANALGESIC properties

 

6

When in N2O contraindicated?

  • Related to gas expansion
    • Pneumothorax
    • Lap surgery with CO2 insufflation
    • Air embolism
    • Tympanic membrane surgery
    • Eye surgery
    • Intestinal obstruction/surgery
    • Intracranial air
  • Pregnancy
    • DNA suppression, esp. in 1st trimester
  • Pulmonary HTN/ elevated R. atrial pressure
  • Megaloblastic anemia

7

What is the dose of N2O?

  • Vapor Pressure: 38,770
  • b/g solubility: 0.47 (low- fast on)
  • MAC dose: 105%

8

What is the drug class/ chemical description of Halothane?

Inhaled Volatile Anesthetic.  It is a halogenated alkane derivative.

9

What is the MOA/ Pharmacodynamics of Halothane?

Same as all of the other IAs.

10

What are the side effects of Halothane?

  • CNS
    • Increased CBF, ICP
    • Decreased CMRO2 (uncoupling), dec. cerebral activity, cerebral autoregulation blunted
  • NM
    • Halothane has the least amount of relaxant effect
    • Most likely agent to cause MH
    • Poteniates NMDRs
  • Resp
    • Potent brochodilator
    • Increased RR, inc. resting PaCO2
    • Decreased TV, severe depression of hypoxic drive
    • Hypoxic pulmonary vasoconstriction inhibited
  • CV
    • Inc. CVP
    • Myocardial depressant
    • No change in SVR- the others  volatiles decrease it
    • Baroreceptor reflex is blunted.  You'll see no inc. in HR when BP drops.
    • Decreased BP and CO
    • coronary vasodilator
    • Significant risk of arrhthmia (prolonged QT, decreased AV conduction, HIS, purkinje, common junctional rhythm, VF/VT)
    • Increased sensitivity to EPI
  • GI
    • All IA can cause N/V
  • Liver
    • Halothane hepatitis (IgG mediated immune response from trifluroacetic acid)
  • Renal
    • Decreased RBF, GFR, and UOP

11

What are the contraindications to using Halothane?

  • Liver failure
  • caution in Cholecystitis
  • CCB (increases myocardial depression)
  • BBlockers (increases myocardial depression)
  • TCAs (causes unstable BP)
  • MAOIs (causes unstable BP)
  • Aminophylline (inc. vent. arrhythmias)
  • Hx. of MH (Halothane the most potent trigger)
  • Aortic Stenosis
  • avoid in kindey disease
  • avoid in neuro cases
  • avoid in pheochromocytoma

12

What is the dose of Halothane?

  • Vapor Pressure : 243
  • b/g coefficient 2.4 (intermediate onset)
  • MAC: 0.74% (high potency)

13

What are the pharmacokinetics/ metabolism of Halothane?

  • It is a nonflammable, sweet gas
  • It has thymol as a preservative (can gum up the vaporizer)
  • It is eliminated by exhalation and biotransformation
  • It depends largely on hepatic metabolism (15-20%)

14

What is the mechanism of action/ pharmacodynamics of Enflurane?

  • Enflurane has the same MOA as the other IAs

15

What is the drug class/ chemical structure of Enflurane?

Enflurane is a Volatile Anesthetic.  It is an isomer of Isoflurane.  It is a halogenated methyl ethyl ether.

16

What are the side effects of Enflurane?

  • CNS
    • Increased CBF, ICP, IOP
    • Decreased cerebral activity, dec. CMRO2, cerebral autoregulation is blunted
    • Increases CSF production and dec. CSF outflow= high ICP
    • Seizures- do not use in pt. with seizure d/o
    • DO NOT HYPERVENTILATE TO DECREASE ICP- hypcarbia makes a more favorable condition for seizures.
  • NM
    • potentiates NMDR
  • Resp
    • Increased RR, inc. resting PaCO2
    • Decreased TV
    • Marked resp. depression at 1 MAC
    • Abolishes hypoxic drive
    • Decreases mucociliary function
    • Bronchodilator
  • CV
    • Decreased SVR, BP, CO
    • Increased HR (baroreceptor)
    • depressed myocardial contractility
    • Pronlongs QT
    • Increased risk of arrhythmia with epi use
  • GI
    • N/V
  • Liver
    • decreased HBF
  • Renal
    • decreased RBF, GFR, UOP
    • Fluoride levels could lead to high ouput renal failure

17

What the contraindications to using Enflurane?

  • Renal dysfunction
  • Seizures
  • MH

18

What is the dose of Enflurane?

  • Vapor Pressure: 175
  • b/g coefficient: 1.8 (intermediate solubility)
  • MAC- 1.7% (high potency)

19

What are the pharmacokinetics/ how is enflurane metabolized?

  • Enflurane is a mild, sweet gas
  • It is eliminated by biotransformation and exhalation
  • It is 2-5% metabolized by the liver
  • It has the potential for nephrotoxicity d/t fluorine content

 

20

What are the pharmacodynamics/ mechanism of action of N2O?

The same as the other IAs

21

What are the pharmacokinetics/ how is N2O metabolized?

  • It is eliminated by exhalation and biotransformation
  • < 1% metabolized by the liver

22

What is the drug class/ chemical structure of Isoflurane?

  • It is an inhaled volatile anesthetic
  • It is a halogenated methyl ethyl ether
  • It is an isomer of enflurane

23

What is the MOA/ pharamacodynamics of Isoflurane?

The same as the other IAs

24

What are the side effects of Isoflurane?

  • CNS
    • Increased CBF, ICP
    • Decreased CMRO2
    • Increased CSF reabsorption
  • NM
    • potentiates NM blockade
  • Resp
    • bronchodilator
  • CV
    • Decreased SVR but BP  and CO maintained
    • Increased HR, mild Beta stimulation, but CV stable
    • Coronary artery dilation BUT may cause CORONARY STEAL
  • GI
    • N/V
  • Liver
    • no change in hepatic blood flow (good drug for liver and kidney disease)
  • Renal
    • decreased RBF, GFR, UOP

25

What are the contraindications to using Isofluane?

  • Pediatrics- has a  pungent odor, may cause coughing and laryngospasm
  • MH

26

What are the pharmacokinetics/ metabolism of Isoflurane?

  • Isoflurane is eliminated by exhalation and biotransformation
  • Isoflurane has <0.2% hepatic metabolism

27

What is the dose of Isoflurane?

  • Vapor pressure: 239
  • b/g coefficient: 1.4 (intermediate solubility)
  • MAC: 1.2% (potent)

28

What is the MOA/ pharmacodynamics of Desflurane?

Same as the other IAs

29

What is the drug class/ chemical structure of Desflurane?

  • Desflurane is a volatile inhaled anesthetic
  • It is a flurinated methyl ethyl ether
  • It has a similar structure to Isoflurane

30

What are the Pharmacokinetics/ metabolism of Desflurane?

  • Eliminated by exhalation and biotransformation
  • Hepatic metabolism <1%
  • May create CO with low flows
  • Uses a TEC 6 vaporizer
  • Fast on and fast off

31

What are the side effects of Desflurane?

  • CNS
    • Increased CBF, ICP
    • Decreased CMRO2
  • NM
    • potentiates NMB
  • Resp
    • bronchodilation
    • irritating to the airway- pungent odor can cause coughing, bucking and laryngospasm
    • Carbon monoxide risk of used with low flows (check your CO2 absorber, keep it fresh)
  • CV
    • Decreased BP, SVR
    • Increased HR (no change in CO)
    • DOES NOT DILATE THE CORONARY ARTERIES
  • GI
    • Nausea and vomiting
  • Liver
    • decreased HBF
  • Renal
    • decreased RBF, GFR, and UOP

32

What are the contraindications to using Desflurane?

  • MH
  • Pediatrics induction

33

What is the doe of Desflurane?

  • Vapor Pressure: 664
  • b/g coefficient: 0.42
  • Mac 6%

34

What is the drug class/ chemical structure of Sevoflurane?

  • Fluorinated methyl isopropyl ether

35

What is the mechanism of action of Sevoflurane?

same as the other IAs

36

What are the side effects of Sevoflurane?

  • CNS
    • Increased CBF, ICP
    • Decreased CMRO2
  • NM
  • Resp
    • Bronchodilation
  • CV
    • Decreased SVR, BP, CO
    • Increased HR
    • no change in CVP
  • GI
    • Nausea/Vomiting
  • Liver
    • Hepatic blood flow maintained
  • Renal
    • Can cause accumulation of Compund A and nephrotoxicity with low flows (keep flows 2L)
    • Decreased RBF, GFR, UOP

37

What are the contraindications to using Sevoflurane?

  • MH
  • Severe renal disease

38

What is the dose of Sevoflurane?

  • Vapor pressure: 157
  • b/g coefficient: 0.69
  • MAC: 3%

39

What is the metabolism/ pharmacokinetics of Sevoflurane?

  • Ideal for pediatrics- sweet & non-pungent
  • minimal airway irritation
  • expensive
  • eliminated via exhalation and biotransformation
  • Hepatic metabolism 2-3%