This study is a prospective cohort study aiming to evaluate an improved VPIA remifentanil algorithm which would benefit labouring mothers who are unable or unwilling to receive epidural analgesia

This study trials a new Vital signs-controlled patient-assisted intravenous analgesia (VPIA) regimen using a purpose-built pump that aims to enhance the efficacy, safety and personalization of remifentanil therapy for labouring women. The system studies the parturient's pattern of analgesic use in 15 minute epochs and titrates the demand doses and basal infusion rate to maintain a plasma level of remifentanil that is appropriate for the degree of pain felt.

The system incorporates vital signs (pulse oximetry and heart rate values) into the algorithm which would temporarily stop the pump and step down doses accordingly when predefined critical values are reached.

Inclusion Criteria:

• Patients who choose to use parenteral opioid for pain relief with informed consent
• Patients who refuse labour epidural analgesia or with contraindication to epidural analgesia (eg. thrombocytopaenia, previous thoraco-lumbar spinal instrumentation)
• Gestational age of >= 36 weeks

Exclusion Criteria:

• Patients who are unable to understand instructions given regarding the use of patient controlled analgesia (PCA) or unable to self administer PCA boluses
• Patients with difficulty in communication due to language differences
• Patients with known hypersensitivity to remifentanil or any component of its formulation or to other fentanyl analogue
• Patients with severe respiratory disease
• Patients with history of drug dependence of recreational drug abuse
• Patients with unmanaged foetal bradycardia