Peripartum Analgesia (Preston day 3) Flashcards
What is the IV dose for fentanyl in labour?
0.5-1 mcg/kg dosing repeated to max 4 mcg/kg
What is the Maximum safe local anesthetic doses with/without epinephrine for lidocaine 1% and bupivacaine 0.25%. ?
Lidocaine 4-5 mg/kg plain, 7 mg/kg with epi
Bupivicaine 175 mg plain or 335 mg with epi
What is the early labour morphine dose?
IM 5-15 mg
SC 5-10 mg (most common)
IV 2-5 mg
PO 15-60 mg
How are prostaglandins formed?
By arachidonic acid - that forms COX 1 and COX2
Which NSAIDs are in the proproinic acid category (4)?
ibuprofen, naproxen, diclofenac, ketoprofen
What are examples of prostaglandin inhibitors?
NSAIDS ex asprin and ibuprofen - COX 1 and COX 2
COX 2 inhibtors (just COX 2)
What does COX 1 do (2)?
Constitutional
* 1) Protects gastric mucosa
2) Aids in making platelets sticky
What does COX 2 do?
Inducible
* Recruit inflammatory cells
* Sensitize skin to pain receptors
Regulate hypothalamic temperature control
Why does NO work well for contraction pain?
Fast on, fast off - reaches height concentration level in 3 mins
What is nitrous oxide?
A weak inhalational anesthetic agent with very poor solubility (doesn’t distribute to all other tissues but builds to a good concentration in lungs and gets into blood and effects brain)
What is Entonox?
- 50:50 mixture of N2O used labour LAUGHING GAS
- Used by 35% birthers in Canada (higher where epidural not available)
- Very weak, maybe no benefit over air, but many ppl obtain relief (psychosocial benefit likely real - focus on breathing technique)
Breathing at start of contraction to maximize N2O [ ] at peak of contraction - avoid hyperventilation because it shifts maternal oxyhemoglobin dissociation curve to left and reduced fetal O2 uptake
What is MOA of NO?
CNS depressant thought to alter main perception through descending spinal cord pathway
How is NO used with labouring person?
Quick uptake - fast on fast off (poor lipid solubility and low potency) makes it good for contraction pain
What are the safety measures w/Nos in labour (6)?
- Scavenging system - exhale into device and sent outside (to prevent exposure to HCP in room)
- Demand valve (only flows when inhales)
- Regular maintenance
- Greenhouse gas (limit use in other contexts)
- Patient ONLY administered
- Mouthpiece better than mask
Benefits of NO (6)?
- Safe for fetus/neonate as poor lipid solubility therefore transfer low and onset of spontaneous respirations at birth quickly eliminates residual N2O (only goes lung->blood->brain->back again) [breathing gets rid of the NO]
- No effect on uterine tone
- Inexpensive
- Minimal toxicity, minimal cardiac depression
- No known effect on breastfeeding
i.e. relatively benign
Side effectes of NO?
- Side effects dizziness, nausea, sedation, hypoventilation (breath less often)
- Loss of consciousness from OD - rare but happens 0.4 % with the 50:50 mixture
Possible sedation with prior parental opioid use (morphine/fentanyl)
What are the sedatives (2)?
Benzodiazepines and Phenothiazines
What did ‘twilight sleep’ have?
Benzos and opioids :(
What are benzodiazepines?
- Most commonly used for sedation and anxiolysis (sedated but awake)
- Useful to reduce excessive anxiety peri-procedure:
- Anxiety is linked to increased pain
- Anxiety is linked to increased nausea/vomiting
What are possible effects of benzos on dyad?
May affect neonatal neurobehavioral scores if used regularly in pregnancy
- Pregnancy Class D:
- 1st trimester – cleft lip/palate (valium specifically)
3rd trimester – neonatal benzodiazpine withdrawal syndrome
- 1st trimester – cleft lip/palate (valium specifically)
What receptor does benzos act on?
indirect GABA A – enhance effects of GABA
What are the traits of benzos?
- Hepatic metabolism
- Highly protein bound
What are the effects of Benzodiazepines (7)?
- Sedation
- Hypnosis
- Anxiolysis
- Anti-convulsant
- Amnesia (bigger doses)
- Muscle relaxant
Co-analgesic
What are the side-effects of benzos (8)?
- Drowsiness
- Amnesia
- Depression
- Balance impairment
- Dependence
- Cognitive impairment
- Paradoxical reactions
Respiratory Depression (insignificant in healthy adult if sole agent; enhances respiratory depressant effects of co-administered opioid)
What are GABA (A) receptors (3)?
- GABA is the primary inhibitory neurotransmitter in the CNS
- GABA-receptor allows Cl- to cross into the cell, hyperpolarizing the membrane and inhibiting neural transmission
Benzodiazepines INCREASE frequency of channel opening - inhibits anxiety