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Flashcards in General Anesthetics Deck (34):
1

Components of Anesthetic State

Amnesia
Unconsciousness
Analgesia
Immobility in response to noxious stimuli

2

Define MAC

Minimal alveolar concentration --> Measured by concentration of anesthetic in the end-tidal expired air (correlates well with concentration at the site of action -- brain)

3

Molecular Targets of Anesthetics

GABA(A) receptors
NMDA receptors
Other membrane associate proteins

4

Stages of General Anesthesia

1. Pre-medicatoin
2. Induction
3. Maintenance

5

Parenterally administered Anesthetic
Barbiturate
Activates GABA(A) receptors; used to induce anesthesia; 1/2 life = 12 hours (hangover)

Sodium Thiopental

6

SE of Sodium Thiopental

CNS depression (decrease O2 demand, decrease BF, decrease intracranial P); CV vasodilator; Respiratory depression

7

Most commonly used anesthetic in the US; GABA(A) mechanism; Used to induce and maintain anesthesia; anti-emetic; Half-life in body: 3.5 hrs (less hangover)

Propofol

8

SE of Propofol

Pain on injection; Can cause initial excitation on induction; CNS effects; CV Effects more severe reduction in BP than thiopental and depression of myocardial contractility; Respiratory: more depression than Thiopental

9

Used to induce anesthesia in patients at risk for hypotension

Etomidate

10

SE of Etomidate

Pain on injection, myoclonus; N/V; Suppression of adrenocortical response to stress -- only used to induce anesthesia in patients with hemodynamic problems

Also CNS SE; CV: less than thiopental; Respiratory: less than thiopental

11

Produces dissociative anesthesia; NMDA receptor antagonist; No effect on respiration

Ketamine

12

SE of Ketamine

Nystagmus, salivation, lacrimation, increase muscle tone and spontaneous movement;
Increased intracranial pressure d/t increased cerebral blood flow;
Emergence delirium; Hypertension (sympathomimentic)

13

What populations is Ketamine useful for?

Patients with bronchospasm; Children undergoing short, painful procedures

14

Short acting benzodiazepine; GABA(A) activator; Used for conscious sedation, anxiolysis, amnesia during short procedures; Used preoperatively to decrease anxiety

Midazolam

15

How does Midazolam differ from Sodium Thiopental?

Slower induction and longer duration; Metabolized by hydroxylation to active metabolite

16

SE of Midazolam

Respiratory depression and arrest (IV); Use with caution in patients with NM disease, Parkinson's, Bipolar; CV effects similar to Thiopental

17

What does it mean if a anesthetic has a low blood:gas PC?

1. Need high amounts in inspired air
2. Induction is quick (equilibrium is reached quickly)
3. Recovery will be quick (drug moves out of blood into gas readily)

18

What does it mean if a anesthetic has a high blood:gas PC?

1. Need less in inspired air
2. Induction and recovery are slow (equilibria is reached slowly)

19

What does it mean if an anesthetic has a high fat:blood PC?

Half-life will be long (hang over) d/t slow release into blood; enough gets into brain to make the patient feel sleepy

20

What are some factors that affect induction with a gaseous anesthetic?

1. Anesthetic concentration in the inspired air
2. Pulmonary Ventilation
3. Pulmonary BF
4. Arteriovenous concentration gradient

21

When is anesthesia achieved with gaseous anesthetics?

Anesthesia is achieved when the brain partial pressure is equal to MAC

22

How does elimination of the gas occur?

Reverse of induction: gas moves from blood into inspired air
Rate of elimination is dependent upon the blood:gas partition coefficient (lowest eliminated fastest)
Gas needs to get into the blood to be eliminated

23

Moderate blood:gas PC; Excreted unchanged in expired air

Isoflurane

24

What is Isoflurane used for?

Can be used to induce and maintain; but mostly for maintenance

25

SE of Isoflurane

Airway irritant, coughing, decreases tidal volume and increases respiratory rate; CV: myocardial depression, decreases BP, arrythmias, cerebral vessel vasodilation

26

Very low solubility in blood; induction and recovery are rapid; Excreted unchanged in expired air

Desflurane

27

What are the clinical uses of Desflurane?

Outpatient surgeries/maintenance; Skeletal muscle relaxation

28

SE of Desflurane

CV; Respiratory: worse irritant, can produce bronchospasm

29

Very low blood: gas partition coefficient; 5% of administered does is metabolized to fluoride ion in the liver; Degraded to compound A by absorbents

Sevoflurane

30

What are the clinical uses of Sevoflurane?

Very popular; Inpatient and outpatient, can be used to induce and maintain in children and adults; NOT a respiratory irritant

31

Very insoluble in blood, rapidly equilibrates; Uptake from air results in increased concentration of other anesthetics; Useful for induction

Nitrous Oxide

32

Why do you patients need to breathe 100% O2 during emergence when given N2O?

N2O can dilute oxygen

33

What are some clinical uses of N2O?

Weak anesthetic; Good for sedation and analgesia; Used together with other inhaled anesthetics to reduce dose needed

34

What is N2O CI for?

Pneumothorax