Anesthetic Pre-medications - analgesics

Question 1

what is the purpose of analgesics as premedication

Answer 1

to minimize or abolish pain during and following surgery

Question 2

opioids as pre-medications

Answer 2

• surgical manitulations produce a larghe number of pain signals and stimulate the RAS pathway in the medulla
• opioids inhibit pain signal so the patient doesnt wake up
• used because general anesthetics do not inhibit pain signal generation

Question 3

why is administering opioids as a premedication safer than maintaining unconsiousness with higher doses of general anesthetic

Answer 3

• higher doses would inhibit all brain activity including respiration and CV function

Question 4

Opium (the poppy) contains what compounds

Answer 4

• morphine
• codeine
• heroin
• hundreds of other chemicals

Question 5

major and minor sites of opioid receptors

Answer 5

major = pain pathways
minor = most other organ systems

Question 6

what are the possible uses of opioid drugs

Answer 6

Analgesia (manage pain) - most known for
sedation
cough suppression
treatment of diarrhea

Question 7

true or false: opioids are used thoughout all steps of the general anesthesia protocol

Answer 7

true

Question 8

opioid receptor families that mediate analgesia

Answer 8

Mu: mediates/prevents severe pain, most side effects
Delta
Kappa

Question 9

opiod receptor that produces dysphoria

Answer 9

sigma

Question 10

analgesia vs dysphoria

Answer 10

analgesia: pain reduction
dysphoria: terror, hallucinations, state of unease

Question 11

types of opioid drugs

Answer 11

morphine
codeine
fentanyl

heroine
oxycodone
hydrocodone
hydromorphone

Question 12

Opioids - mechanism of analgesic effects

Answer 12

• pre-synaptic stimulation: inhibits opening of Ca2+ channel - inhibit release of NT
• no Ca2+ = no neurotransmission
• post-synaptic stimulation: opens K+ channel - inhibit depolarization
• no K+ = hyperpolarozation
• overall = inhibit neurotransmission in pain pathways

Question 13

stimulation of the Mu opioid receptor leads to…

Answer 13

• analgesia - intense
• euphoria
• miosis (pupil constriction)
• respiratory depression

Question 14

stimulation of the delta opioid receptor leads to…

Answer 14

• analgesia
• respiratory depression

Question 15

stimulation of the kappa opioid receptor leads to…

Answer 15

• analgesia - moderate

Question 16

stimulation of the sigma opioid receptor leads to…

Answer 16

• dysphoria
• hallucinations
• respiratory and vasomotor stimulation
• *stimulated by some opioids and some non-opioids (e.g. ketamine)

Question 17

properties of opioid drugs

Answer 17

• can stimulate opioid receptors maximally or weakly
• some are agonists at one receptor and antagonists at another

Question 18

Fentanyl vs. Pentazocine

Answer 18

• Fentanyl = full mu agonist
• Pentazocine = full kappa agonist and partial mu agonist
• pentazocine is like a competetive antagonist to fentanyl

Question 19

Pentazocine at the Mu receptor

Answer 19

• produces weak analgesic effect
• when present, prevents fentanyl from binding which produces a string analgesic effect
• when administered together weaker effect than fentanyl alone

Question 20

pharmacokinetics of opioids

Answer 20

• weak bases
• Phase I and II metabolism with high first-pass effect
• cocaine is a “pro drug” that is metabolized to morphone - depends on persons CYP2D6 activity

Question 21

Physiological effects in the CNS of full Mu agonists

Answer 21

• analgesia
• sedation

Question 22

what opioids are known to be full Mu agonists

Answer 22

morphine
fentanyl

Question 23

Physiological effects in the CV system of full Mu agonists

Answer 23

• little effects at normal doses
• morphone may cause histamine release - causes hypotension

Question 24

Physiological effects in the respiratory system of full Mu agonists

Answer 24

• dose-dependent depression of respiratory system
• more intense effect when combined with a general anesthetic
• repiratory arrest (overdose = death)
• supress cough reflec

Question 25

how can you reverse respiratory depress caused by opioid overdose

Answer 25

naloxone

Question 26

Physiological effects in the GI system of full Mu agonists

Answer 26

- constipation: reduced propulsion in large bowel - biliary colic: bile duct sphincter constriction - nausea and vomitting

Question 27

Physiological effect in the urinary system of full Mu agonists

Answer 27

- bladder ohincter tine increased, causing urgency to urinate but difficult

Question 28

clinical use for full Mu agonists

Answer 28

treat moderate to severe pain

Question 29

clinical use for opioid (Mu agonist) + a sedative

Answer 29

profound sedation prior to surgery

Question 30

clinical use for a Kappa agonist

Answer 30

mild to moderate pain

Question 31

clinicale use for codeine

Answer 31

anti-tussive (prevent seizure)

Question 32

clinical use for loperamide

Answer 32

anti-diarrheal

Question 33

Fentanyl - example of an opioid as pre-medication

Answer 33

- full Mu agonist - used for pain releif - most common opioid for pre and post operative analgesia (IV administered) - constipation is common - for chronic pain administered as a transdermal patch

Question 34

Naloxone - example of an opioid antagonist

Answer 34

- binds and blocks Mu receptor (competitive inhibition) - treatment for opioid overdose - reverse profound sedation - treat circulatory shock due to endogenous opioids

Question 35

Carfentanyl - opioid used for sedation and imobilization

Answer 35

- used to immobilize large animals - extremely fatal - reversal agent (naloxone) required for recovery to occur - Etorphine is a drug like carfentanyl but used for wildlife

Question 36

opioids as anti-diarrheal medication

Answer 36

- e.g. Loperamide and Diphenoxylate - reduce propulsive gut motility - constrict anal sphincter - less addictive than other opioids