FRCA Notes

Remifentanil PCA for Labour Analgesia

The curriculum requires us to demonstrate the "ability to provide intravenous opiate analgesia including PCA for labour".

Remifentanil PCA was the subject of a CRQ in September 2020, but the 29% pass rate had examiners decrying "little knowledge or experience" of its use. Marks were lost on dosing, timing and the safety aspects of its use.

Resources

  • Neuraxial techniques remain the gold standard for labour analgesia
  • They are, however, contraindicated in certain patient populations and some parturients may prefer other modes of analgesia

  • Remifentanil PCA may be a suitable alternative
  • The Swiss RemiPCA SAFE Network was initiated in 2009 and from 10,000 reported users, 82% were either satisfied or very satisfied with their labour analgesia
  • Remifentanil's pharmacokinetic characteristics make it ideal for labour analgesia:
    • Onset in 30-60s
    • Peak effect in 2-3mins
    • Short half-life (context-sensitive half-time 3mins)

  • There are high rates of placental transfer owing to the high lipophilicity of the drug and high placental perfusion
  • However, the drug undergoes rapid metabolism and redistribution in the foetus and is therefore felt to be safer than other opioids for the foetus

  • Bolus dose: 40μg (30 - 50μg)
  • Lockout period: 2mins

  • Background infusions are rarely used due to the incidence of severe, adverse effects
  • Furthermore, one study demonstrated significantly lower pain scores for PCA vs. continuous infusion


Contraindications
<36 weeks gestation
IUFD (as better drugs available)
Parenteral opioids within 4hrs
Allergic to opioids
Multiple (twin) pregnancy
Severe cardiorespiratory disease
Extremely raised BMI (>40kg/m2)
  • Initial studies of remifentanil PCA use were beset by adverse maternal effects, including:
    • Facial/generalised pruritus
    • Sedation
    • Desaturation and apnoea
    • Airway obstruction
  • There is no increased incidence in minor adverse effects such as pruritus, nausea or vomiting compared to epidural analgesia

Respiratory depression

  • Respiratory depression is common, although the prevalence is reported as a hopelessly wide rage from 5% - 93%
  • Compared to neuraxial analgesia, remifentanil produces:
    • More apnoea events (defined as RR <8bpm or no ventilation >20s)
    • Greater incidence of maternal desaturation <94% (the RemiPCA Safe Network data suggests the incidence of hypoxaemia is 26%)

  • Life-threatening respiratory complications can ensue and are potentially under-reported
  • Methods to monitor for, prevent and manage respiratory adverse effects include:
    • 1:1 nursing by midwife, which decreases incidence of adverse events
    • Continuous pulse oximetry
    • Oxygen supplementation
      • Routine application may not prevent hypoxia or apnoea
      • Some protocols advocate only once SpO2 <95%
    • Capnography, which increases the chance of identifying respiratory depression and apnoea
    • Anaesthetic support readily available
    • Routine collection of data pertaining to adverse events with remifentanil PCA

vs. epidural analgesia

  • Epidural analgesia tends to provide superior analgesia (Grade 1 evidence)
    • As evidenced by higher pain intensity scores for those using remifentanil PCA
    • This difference is apparent at 1hr and becomes more pronounced by 2hrs
    • In one study there was a 13% conversion rate from PCA to epidural analgesia (but only 1% vice versa)
    • Despite this, there is similar maternal satisfaction

  • There are similar rates for spontaneous, instrumental or LSCS deliveries
  • Adverse effects are not significantly different, with respect to nausea, vomiting and pruritus
  • There are higher rates of maternal respiratory depression, oxygen desaturation or apnoea
  • Neonatal APGAR scores are similar at 1min and 5min, though umbilical artery pH is higher in women receiving remifentanil PCA

vs. nitrous oxide

  • One study demonstrated significantly better pain intensity scores with remifentanil PCA, though there was a higher subjective sedation score

vs. pethidine

  • Compared to pethidine PCA:
    • Greater decreases in mean pain score in the first hour, but not after 1hr
    • Lower rate of conversion to epidural analgesia

  • Compared to IM pethidine:
    • Remi PCA produces greater reduction in pain scores
    • Lower conversion to epidural analgesia (RESPITE trial)
    • Higher proportion of women using remifentanil PCA had SVD, but rates of LSCS were the same

  • There tends to be higher rates of sedation, desaturation and use of supplementary oxygen in those using remifentanil
  • There is no difference in: haemodynamics, adverse GI effects or neonatal APGAR scores at 1min or 5mins
  • Remifentanil PCA may result in comparatively:
    • Higher neonatal neurological and adaptive capacity score (NACS)
    • Lower incidence of non-reassuring foetal heart rates requiring interventional delivery

vs. fentanyl PCA

  • Greater reduction in pain in the first hour for those using remifentanil PCA, but not beyond 1hr
  • Higher conversion to epidural analgesia in those using fentanyl

  • Remifentanil produced comparatively:
    • Higher sedation scores
    • Higher frequency of maternal desaturations
    • Higher neonatal APGAR scores
    • Lower need for neonatal PPV/I&V