Drugs for Surgery and Pain

Question 1

When was the first surgery using anesthesia?

Answer 1

Surgery is pretty recent, 150 years ago, because there was no safe way to put people to sleep
1846 in Boston the first operation was performed under ether anesthesia

Question 2

Why is diethyl Ether not used anymore?

Answer 2

Diethyl Ether pretty safe, works well, but its extremely flammable

Question 3

What do we use as anesthetics now?

Answer 3

1956: ether is replaced by Halothane
Now: we use sevoflurane, desflurane, isoflurane

Question 4

What are 3 main effects of general anesthesia?

Answer 4

General Anesthesia:
- Lose sensation and consciousness
- Amnesia (no memory of the time)
- Relaxation of skeletal muscles (suppression of reflexes (somatic, autonomic, endocrine) (don’t want blood pressure to change), don’t want muscles to react)

Question 5

Common to use more than one drug to get the desired effect
There is no perfect drug – combining different agents increase the effectiveness and safety
Drugs are given before a surgery to?

Answer 5

• Relax the patient
• Reduce saliva mucus
• Induce unconsciousness quickly (minimize stress)

Question 6

Common to use more than one drug to get the desired effect
There is no perfect drug – combining different agents increase the effectiveness and safety
Drugs are given after a surgery to?

Answer 6

• Reduce pain (analgesic)
• Reversal agents to be able to move after

Question 7

What do inhalation anesthetics end in?

Answer 7

They end in “ane” (isoflurane)

Question 8

Intravenous anesthetics?

Answer 8

Intravenous anesthetic agents (propofol) most common IV anesthetic knock out fast, needs to be used by professionals

Question 9

Inhalation anesthetics?

Answer 9

Can be used on their own for short procedures
Long procedures: blood gas monitoring
Halothane replaced by isoflurane

Question 10

Pharmacokinetics of Inhalation Anesthetics absorption?

Answer 10

Absorption:
Lungs are great for absorbing drugs, huge surface area in alveoli

Question 11

Pharmacokinetics of Inhalation Anesthetics distribution?

Answer 11

Distribution:
Drug delivery is determined by the partial pressure of the gas
Nitrous oxide has a big partial pressure
Partial pressure = driving force to move to alveolus then to the blood then to the brain
Blood gas solubility – how easily it dissolves in blood, if dissolves well, gets held back in blood and gets to the brain more slowly
Nitrous Oxide has low solubility
Blood flow affects the rate of anesthetic uptake, blood flow to the brain is high, get to the brain quickly
(want a high partial pressure, low blood solubility, high blood flow)

Question 12

Pharmacokinetics of Inhalation Anesthetics metabolism?

Answer 12

Many gases are not metabolized by the body, they are just removed as you breath out
In longer procedures, anesthetics are taken up by muscles, longer for the drugs to be removed

Question 13

Pharmacokinetics of Inhalation Anesthetics excretion?

Answer 13

Most volatile agents are cleared by exhalation

Question 14

Pharmacokinetic reminders

Answer 14

Increased concentration, faster anesthetic effects
Increase alveolar ventilation, increases anesthetic effects
Increased solubility, decreases build up in brain
Increased cardiac output, more blood to other organs, decrease rate of anesthesia

Question 15

What is Minimum alveolar concentrations (MAC)?

Answer 15

Produces anesthesia in 50% of people
- Useful reference level
- Not related to sex, body size
- Can be altered by disease, other drugs
- Need around 1.3 MAC for most situations
- Different aesthetics are additive (0.5 + 0.5 = 1 MAC)
Artificial respiration is used because as procedures get longer there is more respiratory depression, need to make sure they breath properly

Question 16

Nitrous oxide?

Answer 16

• MAC is greater than 100%: incomplete anesthetic
• Good analgesia
• No metabolism
• Few sides effect
  doesn’t affect blood pressure or respiration much

Question 17

Isoflurane?

Answer 17

Isoflurane (1984)
- Widely used
- No cardiac arrest
/cardiac depression

Question 18

Side effect of halothane?

Answer 18

Halothane: sensitizes heart to arrythmia

Question 19

Intravenous anesthetics?

Answer 19

• Less respiratory, cardiovascular depression compared to Inhalation anesthetics
• Quick action
• Nontoxic
• Short duration
• Stable

Question 20

Barbiturates as IV anesthetics? (2)

Answer 20

Onset is 30 seconds, redistribution terminates action
Thiopental: used for induction, half life too long for maintenance (takes too long to break down, so can’t keep giving it)
Propofol: rapid onset, half life is less than thiopental, used in procedures that don’t take too long

Question 21

Benzodiazepines used for surgery? (2)

Answer 21

Diazepam – induction is slow (minutes)
Midazolam – induction in 2-3 minutes, short duration, amnesia
Opioids + midazolam: conscious sedation

Question 22

Opioids used in surgery?

Answer 22

Fentanyl: useful for surgery and pain relief combined with other drugs, relieves pain, lowers anxiety but respiratory depression, nausea, and vomiting

Question 23

Causes of respiratory depressions?

Answer 23

Anesthetics depress
Anesthetics and opioids depress even more

Question 24

Neurolept anesthesia vs total IV anesthesia?

Answer 24

Neurolept analgesia (interfere with neurons)
Fentanyl + droperidol (antipsychotic) – diagnostic and minor surgery, with Nitrous oxide for neurolept amnesia
Total IV Anesthesia
Hypnotic (propofol) + opioid (remifentanil) + amnesic (midazolam) +/- muscle relaxant

Question 25

What is Acetamine?

Answer 25

The only IV anesthetic that stimulates CVS
Doesn’t depress cardiovascular function
Dissociative anesthesia, Dysphoria (fuzzy state of mind, nightmares)

Question 26

Why is acetamine good for burn patient use?

Answer 26

Used with other drugs, used with burn patients (sensitive CVS function, changing their dressings)
Good for use with babies/kids, protect CVS
Sensory loss, analgesia, amnesia, paralysis, still somewhat conscious, minimize CV complications

Question 27

Anesthesia pharmacodynamics?

Answer 27

Increase dose, increase anesthetic depth
Act all over the brain
No common structure between gases/ barbiturates ex
Inhalation gas – potency related to lipid solubility
Main site of action is the synapse
Decrease excitation, increase inhibition
Can act post synaptically
Presynaptic action mainly decreases neurotransmitter release

Question 28

Isoflurane pharmacodynamics?

Answer 28

Isoflurane: 2 presynaptic mechanisms, less Ca2+ comes in, less transmitter release
Postsynaptic: ligand gated ion channels, GABA, Glycine, 5HT, nicotinic Ach, NMDA, glutamate
Major inhibit GABA and glycine Cl- ion channels
Decrease excitation: neuronal nicotinic, glutamate, NMDA channels

Question 29

Anesthetics main receptor target?

Answer 29

GABA A receptors main target: increase inhibition
Increase inhibition: synaptic and extra synaptic receptors

Question 30

What is ketamine?

Answer 30

a general anesthetic that acts on the spinal cord and mainly decreases excitation

Question 31

Local anesthetics action?

Answer 31

Injected in location, only act on nerves in the area
Act on voltage gated Na+ channels (on axons) block transmission on axon
Block sensation in that area, doesn’t affect other parts of the body
Block Na influx: block propagation of action potential

Question 32

What is lidocane?

Answer 32

A classical local anesthetic

Question 33

EMLA: eutectic mixture of local anesthetic?

Answer 33

Good with kids to get vaccinations

Question 34

people who can’t breakdown succinylcholine?

Answer 34

Have trouble breathing on their own