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PHARMACOLOGY > 12-Drugs for local and general anesthesia > Flashcards

12-Drugs for local and general anesthesia Flashcards

1
Q

What is general anesthesia?

A
  • a loss of sensation throughout the entire body, accompanied by a loss of consciousness
  • used in major surgery
  • often not just one drug (balanced anesthesia)
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2
Q

What is local anesthesia?

A
  • a loss of sensation to a limited body region, with no loss of consciousness
  • used for sutures or cavity filled
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3
Q

What is regional anesthesia?

A
  • it is a type of local anesthesia
  • a loss of sensation to a larger body area, with no loss of consciousness
  • often results in the loss of ROM and movement
  • used during labour
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4
Q

What is monitored anesthesia care?

A
  • sedation (“twilight”); client remains responsive
  • used during diagnostic procedures, or in combination with local anesthesia for minor surgeries (MRI, CT for kids, tooth extraction)
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5
Q

What is the difference between local anesthesia and local anesthetic?

A
  • anesthesia is the state we want the client to be in
  • local anesthesia is the state of the loss of sensation to a limited body region, with no loss of consciousness
  • local anesthetic is a drug class that causes the loss of sensation
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6
Q

What form of anesthesia is topical administration? Briefly describe the topical route of administration

A
  • local anesthesia
  • administration routes: sprays, cream, suppositories, drops, lozenges
  • anesthetics are applied to mucous membranes including the eyes, lips, gums, nasal membranes, and throat
  • topical route reduces systemic adverse affects
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7
Q

What form of anesthesia is spinal (intrathecal) administration? Briefly describe the spinal route of administration

A
  • regional anesthesia
  • anesthetic is injected into the cerebrospinal fluid (space beneath the dura)
  • the anesthetic affects large, regional area such as the lower abdomen and legs
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8
Q

What is one property that is EXTREMELY important for anesthetics used for spinal administration?

A
  • anesthetics that are are used for spinal administration must have a SPECIFIC GRAVITY that does not allow them to float up in the CSF
  • if the drug floats up the CSF, it could affect the heart and lungs = possible death
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9
Q

T or F: The spinal route can be used during a booked or emergency surgery.

A

FALSE! The spinal route can only be used for a booked procedure (ex: a scheduled c-section)

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10
Q

What form of anesthesia is infiltration administration? Briefly describe the infiltration route of administration

A
  • local anesthesia
  • anesthetics are directly injected into tissues immediate to the surgical site
  • anesthetic diffuses into tissue to block a specific group of nerves in a small area close to the surgical site
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11
Q

What form of anesthesia is epidural administration? Briefly describe the epidural route of administration

A
  • regional anesthesia
  • anesthetic is injected into the fat-filled epidural space of the spinal cord. This area is highly vascularised (epinephrine could be administered)
  • epidural is most commonly used in obstetrics during labour and delivery
  • epidural is used when women are in active labour
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12
Q

Which form of administration required more anesthetic – epidural or spinal? Why?

A
  • Epidurals cross through the dura, through the CSF and get to the nerves in the spinal column. For this reason, epidurals require more anesthetic compared to spinal administration
  • Less anesthetic is required for spinal administration compared to epidural because the anesthetic is being administered directly into the CSF and goes right to the nerves
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13
Q

What form of anesthesia is a nerve block? Briefly describe what a nerve block is

A
  • regional anesthesia
  • the anesthetic is directly injected into tissue that my be distant from the operation site (ex: route canal)
  • anesthetic affects nerve bundles serving the surgical area; used to block sensation in a limb or large area of the face
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14
Q

What is the mechanism of action of local anesthetics? What sensory modalities (pain, temp, touch, etc.) do local anesthetics inhibit?

A
  • blocks voltage-gated sodium channels by binding to open sodium channels (therefore no signaling for pain) –> active neurons are most susceptible
  • local anesthetics are NOT selective meaning they block the sodium channel of ANY nerve
  • inhibit both motor and sensory neuronal signalling (pain, temperature, touch, pressure)
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15
Q

What can be co-administered with local anesthetics to improve their duration of action? How is the duration of action improved?

A
  • epinephrine!!
  • epinephrine is an alpha 1 agonist that induces vasoconstriction and restricts distribution of local anesthetics
  • the more blood flow you have, the more the anesthetic will move and distribute to other tissues. We want it to stay concentrated at the surgical site
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16
Q

What are the two sub-classes of local anesthetics?

A

ester and amide

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17
Q

Describe the ester anesthetics (what are the drug properties, drug names, etc.)

A
  • they are not used often
  • they rapidly metabolized in the bloodstream
  • they have a short half-life (1-2 minutes)
  • pKa ranges from 8.6-8.9
  • ex: procaine, benzocaine
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18
Q

Describe the amide anesthetics (what are the drug properties, drug names, etc.)

A
  • metabolized in the liver (CYP 450)
  • longer half-lives (60-240 min)
  • pKa ranges from 7.5-8.0)
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19
Q

What is the connection between drug pKa and the onset of action? How does this impact the ester and amides?

A
  • the closer the pKa of drugs are to physiological pH (7.3), the faster the onset of action (like absorbs like)
  • The amide pKa (7.5-8) is close to biological pH and will have a quicker onset of action compared to the ester (8.6-8.9)
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20
Q

What are the three main options for regional anesthesia for labour?

A
  • nerve blocks (pudendal block)
  • epidural or intrathecal (spinal) injection of local anesthetics
  • epidural administration of opioids
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21
Q

What is the clinical outcome of an epidural or spinal injection of a local anesthetic?

A
  • the pt will not feel pain, sensation or be able to move

- the pt often has to be told when to push

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22
Q

What is the clinical outcome of an epidural administration of opioids?

A
  • opioids are not local anesthetics – they do not induce a complete blockage of nerve impulses (don’t block voltage gated Na+ channels), rather they attenuate both the emotional and sensory aspects of pain
  • pt can feel touch, sensation, pressure and can move
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23
Q

What is the clinical procedure/outcomes of using Bupivacaine, a local anesthetic, for epidural regional anesthesia?

A
  • injection into the fat-filled epidural space (cross dura and exerts an effect on any nerve that it comes into contact with)
  • the client will not feel any pain, pressure, or touch and will not be able to move
24
Q

What is the clinical procedure for the administration of intrathecal (spinal) regional anesthesia? When would this type of anesthesia be used?

A
  • injection of a local anesthetic directly into the CSF
  • administered in the space BELOW the second lumber vertebra but before the coccyx
  • there is a clear endpoint with spinal anesthesia bc you should be able to withdrawal clear CSF
  • typically administered during scheduled surgical procedures (rarely used during labour)
25
Q

What is significant about injecting below the second lumber vertebra for spinal regional anesthesia?

A
  • the cauda equina is located around L2
  • the nerves there are not tightly bundled so when the needle is administered, the nerves can move, which decreases the risk of mechanical damage
26
Q

Which procedure has the higher risk of damage – intrathecal or epidural anesthesia?

A

intrathecal

27
Q

Which procedure has a higher rate of efficacy – intrathecal or epidural anesthesia?

A

intrathecal bc the anesthetic is administered directly into the CSF

28
Q

What would happen if an epidural anesthetic was administered intrathecally (spinal)?

A
  • POSSIBLE DEATH!!
  • the gravity of the epidural anesthetic is not great enough and the drug will travel up the CSF and affect the lungs/heart
29
Q

What is the clinical procedure/outcome for administering an opioid for regional analgesia?

Where is the opioid administered?

A
  • opioid is administered in the epidural space or in the CSF
  • no effect on the activity of motor neurons (mobility, preconception and a sense of touch are maintained)
  • very effective in controlling visceral pain
  • can be co-administered with local anesthetics
30
Q

What is the mechanism of action of opioid analgesia? (what does the opioid inhibit presynpatic/postsynaptic, etc.)

A
  • bind to presynaptic receptors in the substantia gelatinosa, inhibiting the release of pain signalling neurotransmitters in the spinal cord
  • bind to postsynaptic receptors in the brain decreasing neuronal excitability
31
Q

What are some adverse effects of opioid regional analgesia?

A

pruritus is common and can be treated with antihistamines

  • nausea and vomiting may occur if the drug reaches the area postrema in the brain stem (this often occurs if too much drug is given)
  • respiratory depression (rare in regional anesthesia; more common in IV)
32
Q

What are the adverse effects of epidural and spinal anethesia?

A
  • backache
  • infection («1%) (severe infection needs 6-8wks of antibiotics)
  • inadequate anesthesia (ketamine is a non-competitive antagonist)
  • spinal headache
33
Q

What are the adverse effects of epidural and spinal anethesia?

A
  • backache
  • infection («1%) (severe infection needs 6-8wks of antibiotics)
  • inadequate anesthesia (ketamine is a non-competitive antagonist)
  • spinal headache
34
Q

What causes the «1% infection in spinal anesthesia?

A

CSF does not have the same immune cells to protect against pathogens

35
Q

What causes the spinal headache in spinal anesthesia? What’s the treatment?

A
  • CSF leaks, causing traction on the brain from the meninges
  • Brain on bony processes will result in severe headache
  • treated with a blood patch (15-20ml autologous blood transfusion to the puncture site – forms clot and patches up the hole)
36
Q

What are the four stages of general anesthesia?

A

Stage 1 - Analgesia
Stage 2 - Disinhibition
Stage 3 - Surgical Anesthesia
Stage 4 - Medullary Depression

37
Q

Describe Stage 1: Analgesia (general anesthesia)

A
  • loss of pain: the client loses general sensation but may be awake. This stage proceeds until the client loses consciousness
38
Q

Describe Stage 2: Disinhibition (general anesthesia)

A
  • excitement and hyperactivity: the client may be delirious and try to resist treatment.
  • heart rate and breathing may become irregular and BP can increase
  • IV agents are administered here to calm the client
  • “manic stage”
39
Q

Describe Stage 3: Surgical Anesthesia (general anesthesia)

A
  • surgical anesthesia: skeletal muscles become relaxed and delirium stabilizes
  • cardiovascular and breathing stabilize
  • eye movement slow and the client becomes still
  • surgery is preformed during this stage
40
Q

Describe Stage 4: Medullary Depression (general anesthesia)

A
  • paralysis of the medulla region in the brain (responsible for controlling respiratory and cardiovascular activity)
  • if breathing or heart stop, death could result
  • this stage is usually avoided during general anesthesia
41
Q

What are the 6 goals of general anesthesia?

A
  1. analgesia
  2. sedation
  3. relaxation
  4. hypnosis
  5. amnesia
  6. loss of reflexes
42
Q

No single drug can safely accomplish all 6 goals, thus a combination of drugs are used. What are those drugs?

A
  • neuromuscular blockers (reflexes)
  • short-acting benzodiazepines (hypnosis)
    ex: lorazepam, midazolam
  • opioids
    ex: alfentanil, fentanyl, sufentanil
  • general anesthetics (loss of consciousness)
43
Q

What is the clinical outcome of intravenous anesthetics for general anesthesia?

A
  • induce analgesia, sedation, muscle relaxation and loss of consciousness
  • allows pt to quickly move through stages 1&2

Possible drug options:

  • Fentanyl (opioid)
  • Midazolam (benzodiazepine)
  • Propofol (barbiturate)
44
Q

Which administration route is used to maintain anesthesia?

A
  • IV route is usually used to initiate the procedure and then anesthesia is maintained with inhaled anesthetics
  • IV anesthetics decrease the dose of inhaled anesthetic required to maintain anesthesia
45
Q

When could IV anesthetics be used alone without the inhaled anesthetic?

A

IV could be used alone if surgical procedures require less than 15 minutes of anesthesia

46
Q

What is the mechanism of action of inhaled general anesthetics?

A
  • used to maintain anesthesia
  • highly lipid soluble
  • prevent flow of sodium ions into neurons in the CNS, reducing neural activity
47
Q

Describe the gaseous inhaled anesthetics for general anesthesia (ex: nitrous oxide) When would gaseous inhaled anesthetics most likely be used?

A
  • high minimum alveolar concentration (no loss of consciousness), but strong analgesic properties
  • high MAC (molecular alveolar concentration)
  • not used very much
  • used in dental procedures, during labour and minor surgical procedures
48
Q

Describe the volatile liquids for general anesthesia (ex: isoflurane)

A
  • more commonly used for general anesthesia
  • low MAC (minimum alveolar concentration), poor analgesic properties
  • high safety profile – does not induce the same respiratory and cardiovascular depression as other drugs in this class (isoflurane)
49
Q

After being under general anesthesia, patients should be monitored for…. (4 things)

A
  • nausea and vomiting
  • CNS depression
  • respiratory depression
  • changes in vital signs
50
Q

Why would benzodiazepines be prescribed preoperative for general anesthesia?

A

for anti-anxiety and mild sedative effects

51
Q

Why would anticholinergics be prescribed preoperative for general anesthesia?

A

to dry respiratory and oral secretions

52
Q

Why would histamine receptor antagonists be prescribed preoperative for general anesthesia?

A

to decrease gastric fluid volume

53
Q

Why are neuromuscular blockers prescribed during surgery?

A

to induce relaxation of skeletal muscles (for surgery and intubation)

54
Q

What can be given postoperative for pain management?

A

opiates and NSAIDs

55
Q

Why would an antiemetic be prescribed postoperative?

A

to reduce the nausea and vomiting associated with general anesthetics

56
Q

Why would cholinergics be prescribed postoperative?

A

to stimulate smooth muscle contraction in the GI tract and bladder to induce peristalsis and urination

PHARMACOLOGY (27 decks)

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