Obstetric Epidural Management with Opioid Use Disorder

You are the obstetric anaesthetist on duty at a major public hospital. A 22-year-old primigravida is undergoing an induction of labour at 37 weeks gestation for fetal intrauterine growth restriction. Her BMI is 17 kg/m2. Her medical history includes previous oxycodone substance use disorder, for which she takes Suboxone (buprenorphine-naloxone 32 mg/8 mg sublingually every second day). She has no other medical or obstetric history. She had an epidural catheter inserted in early labour by a colleague for analgesia. Although she has difficult venous access, an ultrasound-guided 18-gauge cannula was successfully sited in her cubital fossa. The morning handover indicates that the patient has required two clinician epidural top-ups overnight due to unsatisfactory analgesia. There is now reduced fetal heart rate variability on cardiotocogram (CTG) and the obstetric team would like to place a fetal scalp electrode. The patient is refusing this intervention due to persisting discomfort. The obstetric team requests your assistance to improve her analgesia.