Development of Variable Volume Automated Mandatory Boluses for Patient-controlled Epidural Analgesia During Labour (VVAMB)

Development of Variable Volume Automated Mandatory Boluses for Patient-controlled Epidural Analgesia During Labour

Development of Variable Volume Automated Mandatory Boluses (VVAMB) for Patient-controlled Epidural Analgesia During Labour and Delivery

A novel epidural delivery regimen was developed: Variable volume automated mandatory bolus (AMB) (VVAMB) will advance individualisation of labour epidural analgesia, by which a larger volume of bolus may contribute to better spread of the local anaesthetics within brief period and thereby reduces the chances of motor blockade that could reduce instrumental deliveries.

Epidural analgesia is the gold standard of pain relief for labour pain. Despite this, up to 50% of parturients continue to experience pain leading to suffering and increased caregiver workload. There is also higher risk of motor blockade found in those receiving epidural analgesia, and these factors is associated with dysfunctional labour requiring obstetric intervention (instrumental delivery). Automated mandatory bolus (AMB) of variable-frequency (VAMB) has been shown to provide better pain relief as compared with conventional patient-controlled epidural analgesia (PCEA) with basal infusion, however its long lockout time per hour is associated with unsuccessful patient bolus requests, with similar motor block to conventional regimens. The investigators therefore proposes to develop a novel epidural delivery regimen: Variable volume AMB (VVAMB) will advance individualisation of labour epidural analgesia, by which a larger volume of bolus may contribute to better spread of the local anaesthetics within brief period and thereby reduces the chances of motor blockade that could reduce instrumental deliveries. This algorithm development including pilot and clinical trial will compare VVAMB with VAMB regimens, in reducing the incidence of motor block in 216 term women requesting for labour epidural analgesia.

The anaesthetic drug and pain medication are prepared in an epidural infusion pump with the VVAMB programme. The programme uses higher doses with lower frequency of medication (ropivacaine and fentanyl), and a patient control button for the patient to control the additional pain relief demands depending on the requirements during labour.

The anaesthetic drug and pain medication are prepared in an epidural infusion pump with the VAMB programme. The programme uses lower doses with more frequency of medication (ropivacaine and fentanyl), and a patient control button for the patient to control the additional pain relief demands depending on the requirements during labour.

Epidural delivery system for maintenance of labour epidural analgesia using 0.1% ropivacaine (amide local anaesthetic) with 2mcg/ml fentanyl (opioid) as maintenance solution.

Epidural delivery system for maintenance of labour epidural analgesia using 0.1% ropivacaine (amide local anaesthetic) with 2mcg/ml fentanyl (opioid) as maintenance solution.

Epidural delivery system for maintenance of labour epidural analgesia using 0.1% ropivacaine (amide local anaesthetic) with 2mcg/ml fentanyl (opioid) as maintenance solution.

The number of event of motor block throughout the labour. Previous studies have shown that epidural analgesia using high concentrations of local anaesthetics could lead to decreased motor functions, and are subsequently associated with an increased incidence of instrumented delivery and longer second stage of labour. In this study, the intensity of motor block is assessed by the patient's ability to move their lower extremities via a modified Bromage scale. In the modified version, a scoring of 0 implies no motor block (Free movement of both legs and feet), scoring of 1 implies partial block (Just able to flex knees with free movement of feet), 2 implies almost complete block (Unable to flex knees but with free movement of feet) and 3 implies a full block (Unable to move legs/ feet).

The number of subjects in each group having unscheduled epidural supplementation by anaesthetist due to labor pain

The Appearance, Pulse, Grimace, Activity, and Respiration (APGAR) score is a test given to newborns soon after birth. In the test, five are being evaluated: Appearance (skin color), Pulse (heart rate), Grimace response (reflexes), Activity (muscle tone) and Respiration (breathing rate and effort). Each is scored on a scale of 0 to 2, with 2 being the best score; a total score of ten represents the best possible condition.

Inclusion Criteria: Healthy (American Society of Anesthesiologists (ASA) physical status 1 and 2) primiparous parturient at term (≥36 weeks gestation); Singleton fetus; In early labor stage (cervical dilation ≤5cm); Request labor epidural analgesia and able to administer combined spinal epidural analgesia (CSEA) according to protocol. Exclusion Criteria: Non-cephalic fetal presentation; Obstetric (e.g. pre-eclampsia, premature rupture of amniotic membranes for more than 48 hours, gestational diabetes on insulin, pregnancy-induced hypertension on medication) and uncontrolled medical (e.g. cardiac disease) complications; Have contraindications to neuraxial blockade or have received parenteral opioids within last 2 hours; Dural puncture/ suspected dural puncture at initiation of CSEA.