neuraxial opioids

Question 1

outside the dura, can have a sensory block - a motor block - or both

Answer 1

epidural anesthesia

Question 2

directly in CSF - quick side of effect

Answer 2

subarachnoid

Question 3

what is the point of ERAS protocols?

Answer 3

to decrease amount of opioids being used by moving towards multimodal administration of meds

Question 4

what is receptor distribution in spinal cord

Answer 4

All three (mu, kappa, delta) are present in high 
concentrations in the dorsal horn of the spinal concentrations in the dorsal horn of the spinal Cord
-gelatinosa mainky mu

Question 5

where else are mu receptors found in spinal?

Answer 5

substantia gelatinosa

Question 6

a grey matter structure of the dorsal spinal cord primarily involved in the transmission and modulation of pain, temperature, and touch

Answer 6

substantia gelatinosa

Question 7

what requires a higher dose of neuroaxial opioids?

Answer 7

epidural dose 5-10X subarachnoid dose

Question 8

dose of morphine epidural vs subarachnoid:

Answer 8

epidural dose up to 5 mg

- spinal dose 0.25 – 1 mg

Question 9

what type of pain are neuroaxial opioids best for?

Answer 9

visceral (organ) pain

Question 10

MOA of Opioids placed in the epidural space

Answer 10

diffuse
across the dura to affect mu receptors on
the spinal cord AND are absorbed to
produce the effects like IV opioids

Question 11

what opioid has slower onset in epidural space and why?

Answer 11

morphine because of lower lipid solubility so will have an increase in duration

Question 12

what opioids will absorb more systematically?

Answer 12

fentanyl and sufentanil r/t higher lipid solubility

Question 13

Fentanyl – CSF peak concentration

Answer 13

20 mins

Question 14

Sufentanil – CSF peak concentration

Answer 14

6 mins

Question 15

Morphine – CSF peak concentration

Answer 15

1-4 hours

Question 16

what % of morphine epidural dose enters CSF?

Answer 16

3%

Question 17

how are epidural opioids absorbed?

Answer 17

via the extensive venous plexus

in the epidural space

Question 18

Fentanyl – peak blood conc epidural administration

Answer 18

5-10 mins

Question 19

Sufentanil - peak blood conc epidural admin

Answer 19

<5 mins

Question 20

Morphine - peak blood conc epidural admin

Answer 20

10-15 mins

Question 21

how can absorption be decreased with epidural opioids?

Answer 21

add epinephrine to mixture: the epi vasoconstricts the venous plexus

Question 22

does epinephrine affect the diffusion across the dura?

Answer 22

NO

Question 23

what happens when epinephrine and morphine is injected into subarachnoid space?

Answer 23

the analgesia is enhanced compared to injection

of morphine alone.

Question 24

duration of epidural fent?

Answer 24

50-100 mcg – lasts 1-3 hours

Question 25

duration of epidural morphine

Answer 25

2-5 mg – lasts 4-24 hours | this is scary bc SE could last this long!

Question 26

how does Higher lipid solubility affect mvmt of opioids in epidural space?

Answer 26

limits the movement cephalad as the | drug is taken up by the spinal cord

Question 27

how does lower lipid solubility affect mvmt of opioids in epidural space?

Answer 27

allows longer time in the CSF and movement cephalad (think morphine)

Question 28

what two things effect mvt of epidural opioids cephalad?

Answer 28

coughing and increase in pressure (straining) NOT BODY MVMT

Question 29

4 classic side effects of neuroaxial opioids?

Answer 29

pruritus nausea and vomiting urinary retention Resp depression

Question 30

most COMMON side effect of neuraxial opioids?

Answer 30

pruritis

Question 31

MOA of pruritis with neuraxial opioids

Answer 31

Likely due to opioids in CSF moving up to interact with OR in the trigeminal nucleus

Question 32

what type of patients does pruritis affect more and why?

Answer 32

OB pts due to estrogen

Question 33

treatment of pruritis? (3)

Answer 33

-Opioid antagonist like Narcan – Antihistamines – Gabapentin

Question 34

type of patients that urinary incontinence is more prevelant?

Answer 34

young males

Question 35

what is urinary retention caused by?

Answer 35

interaction of opioid with opioid receptors of the sacral spinal cord inhibition of sacral parasympathetic outflow causing detrusor muscle relaxation, increased bladder capacity

Question 36

treatment of urinary retention?

Answer 36

narcan

Question 37

With epidural morphine, how long can urinary retention last?

Answer 37

15 mins of admin to 16 hrs

Question 38

describe the onset of ventilatory depression with neuraxial morphine

Answer 38

unpredictable and delayed - may be within minutes or 6-12 hours after affects receptors in ventral medulla

Question 39

describe onset of ventilatory depression with neuraxial fent and sufent

Answer 39

within 2 hours due to systemic absorption more than cephalad movement of opioid

Question 40

risk factors for ventilation depression? (6)

Answer 40

``` – Larger dosages – Geriatric age – Receiving other opioids or sedatives – Prolonged or extensive surgery – Presence of co-morbidities – Thoracic surgery ```

Question 41

2 things that cause an Increased risk of delayed depression

Answer 41

– Patient also receiving IV opioid or sedative | – Patient coughing to move opioid cephalad

Question 42

what pt population does vent depression affect least

Answer 42

OB bc of progesterone !!!!

Question 43

what is Most reliable sign of ventilatory depression and why?

Answer 43

decreased LOC bc pao2 late sign

Question 44

treatment of vent depression?

Answer 44

narcan 0.25 mcg/kg/hr (maybe)

Question 45

what neuraxial opioid is most r/t to sedation

Answer 45

sufent

Question 46

explain the MOA of CNS excitation from neuraxial opioid (rare)

Answer 46

cephalad migration of opioid in CSF and interaction with non-opioid receptors in the brainstem or basal ganglia

Question 47

what two neurotransmitters can opioids potentially block inhibition

Answer 47

GABA and glycine (meaning there is more)

Question 48

what virus is reactivated by neuraxial morphine 2-5 days after admin?

Answer 48

herpes due to trigeminal nucleus interaction

Question 49

will you see vent depression in neonate?

Answer 49

YES Related to systemic absorption of opioid –– Minimal opioid found in breast milk Don’t withhold analgesics from C-section patients

Question 50

what can neuraxial opioids do to the eyeballs

Answer 50

Miosis, nystagmus, vertigo

Question 51

other side effects of neuraxial opioids?

Answer 51

- delayed gastric emptying - decreased body temp - water retention (vaso)