Anaesthesia Flashcards
1
Q
labour neuraxial analgesia delivery
A
Indications
- maternal request
- any parity
- any dilation
- any station
Contraindications
- coagulopathy
- infection of lower back
- increased ICP
- severe spinal deformity
Techniques
- epidural
- > continuous
- > PCEA
- > programmed bolus
- combined spinal-epidural
- > intrathecal shot = rapid single shot
- > epidural catheter for maintenance
Drug combination
- low concentration, high volume LA
- > bupivicaine
- > ropivicaine
- lipid soluble opioid
- > fentanyl
- > sufefentanil
Monitoring
- initiation
- > continuous pulse ox
- > BP every 5 mins
- > continuous HFR
- maintenance
- > BP every 30 mins
- > continuous HFR
2
Q
labour neuraxial analgesia effects
A
SE
- hypotension (up to 80%)
- pruritus (very common)
- nausea/vomiting (mostly with morphine)
- urinary retention
Complications
- failure in 10-15%
- motor block
- headache
- allergy/anaphylaxis very rare
- high anaesthetic block (cardiac arrest/resp depression)
- epidural haematoma (extremely rare)
- infection uncommon (abscess/meningitis)
- LAST (seizures/CNS depression/cardiotoxicity)
Fetal effects
- placental hypoperfusion
- > only with hypotension
- > otherwise perfusion is normally improved
- bradycardia
- > hypotension
- > loss of epinephrine relaxation and uterine contractility
Effect of labour
- caesarian rate
- > not increased
- > no difference in caesarian rate with early v late timing
- instrumental rate
- > no difference
- duration of labour
- > may shorten first stage
- > may prolong second stage
- neonate
- > no effect short or long term
- breast feeding
- > likely no difference
3
Q
pudendal nerve block for labour overview
A
Indications
- episiotomy
- instrumental delivery
- perineal repair
Technique
- transvaginal/perineal approach
- aiming for ischial spine
- bilateral single shot LA
Efficacy
- maximum effect 10-20 mins
- lasts up to 1hr
- ineffective in at least one side in up to 50%
- > no effect on cervix/uterine contractions
Complications
- no adverse effect on progress or fetus
- haematoma if bleeding diathesis
- infection
- nerve injury
- LAST
4
Q
Systemic analgesia labour
A
Opioids
- techniques
- > IV/IM/subcut (IV faster and less variable)
- > PCA most effective
- drugs
- > remifentanil >long acting opioids but < neuraxial
- > fentanyl
- > morphine
- efficacy
- > 2/3rds moderate/severe pain after 2hrs
- SE
- > nausea/vomiting
- > stupor
- > resp depression (more common with remifentanil)
- > cardiac arrest
Nitrous oxide 50/50 blend
- technique
- > takes 1 minute to peak (contractions take 30s)
- > begin 30s before contraction
- > cease as it eases to prevent hypoxia
- Efficacy
- > variable and very modest effect
- SE
- > does not affect contractility
- > eliminated quickly/does not depress fetus
- > nausea/vomiting very common
5
Q
non pharm labour analgesia
A
Movement
- technique
- > no preferred position/movement
- > patient preference
- efficacy
- > appears to reduce intervention/complication risk
Exercise ball
- technique
- > relaxes trunk and pelvic floor
- efficacy
- > marginally reduces pain scores
Massage
- technique
- > no optimal technique
- efficacy
- > moderate reduction in early labour
Heat/cold exposure
- technique
- > abdo/perineum/back packs
- > showers
- > baths
- efficacy
- > limited evidence for packs
- > showers = relaxation and coping
- > baths reduce need for systemic pain relief
Breathing technique
- technique
- > rhythmic relaxation
- efficacy
- > majority report greater ability to cope with pain
Music
-no evidence
Aromatherapy
-mixed evidence
Water injection
- technique
- > subcutaneous sterile water (0.1mL) lower back
- efficacy
- > preliminary evidence is supportive
TENS
- technique
- > low voltage electrode on lower back
- > patient controlled strength
- efficacy
- > no evidence
6
Q
opioids
A
MOA
- mimic action of endogenous opioids in CNS and GIT
- act on mu receptors in CNS
- > block ascending pain transmission
- > modulate inhibitory pain pathways
SE
- drowsiness
- respiratory depression
- suppress cough reflex
- nausea/vomiting/dyspepsia
- dizziness/orthostatic hypotension
- anti-cholinergic effects
- > dry mouth
- > miosis
- > urinary retention
- > constipation
- dependence and addiction
Avoid
- combination wing CNS depressive drugs
- > coma/death
- uncontrolled endocrine abnormalities
- > titrate dose
- epilepsy/seizure provoker
- > lowers seizure threshold
- raised ICP
- hypotension/shock
- > increases hypotensive risk
- > increases risk of resp depression
- > impairs IM/sub cut absorption
Precautions
- GI
- > ileus/bowel obstruction
- > sphincter of Oddi dysfunction
- Resp
- > COPD
- > sleep apnoea
- > resp depression
- Renal dysfunction
- > accumulation of active metabolites
- Liver disease
- > increased effect = coma/death
- Elderly
- > cognitive impairment
- > falls
- Pregnancy/breastfeeding
- > withdrawal in newborn
7
Q
morphine pain dosing and specific precautions
A
Acute pain
- no maximum dose
- > dictated by SE
- > lower in elderly
- oral
- > 5-15mg every 4hrs
- IV
- > 0.5-2mg every 5mins
- subcut/IM
- > under 60 = <10mg every 2hrs
- > over 85 = <3mg every 2hrs
Chronic cancer pain
- initial liquid oral
- > 2.5-5mg every 4hrs
- maintenance
- > calculate total 24hr dose of initial
- > give half as tablet/liquid 12hr controlled release
- breakthrough pain
- > give 1/6th total 24hrs dose as oral/liquid
- > adjust total 24hr dose if required regularly
Chronic non cancer pain
- 4-8 weeks trial
- > review every 2 weeks
- > cease with tapering dose if ineffective
- controlled release
- > 5-20mg BD
- tapering dose
- > short term = <25%/week
- > long term = <25%/month
Route peaks
- oral liquid = 1hr
- subcut = 90mins
- IV = 20mins
Route equivalent dosage
-30mg oral = 10mg IM/IV/subcut
Renal
- dose reduce/avoid in moderate kidney disease
- active metabolite accumulates
- > longer half life than morphine
- > respiratory depression and delirium
Liver disease
- avoid use in severe disease
- > sedation/coma
