The Graseby 9500 Epidural Pump
This technique is similar to IV patient controlled analgesia, the difference being that the mother self-administers small boluses of a local anaesthetic-opioid mixture via her epidural.
PCEA was introduced because it was predicted that it would offer several potential advantages over continuous infusion or bolus administration methods. These include patient autonomy in determining level of pain relief, more easily titrated sensory level with minimisation of drug dose, optimal analgesia with minimal side-effects, high patient satisfaction and a reduced demand on professional time. PCEA has become the standard method of epidural pain relief in some centres, or is offered as an alternative to continuous infusion.
Clinical use of PCEA
Satisfactory epidural blockade must be established before the PCEA regimen is instituted. The epidural catheter is connected to a syringe containing a dilute mixture of local anaesthetic and opioid that is loaded onto a special delivery pump (e.g. Graseby 9500). The delivery of the drug from the pump is controlled by the mother with a push button. When the pain of contractions begins to be felt, she presses the button and a small amount of pain relieving medication is delivered via the epidural catheter. The pump will release the dose of drug only after a certain time has elapsed. This is the lockout period and is usually 10-15 minutes. The lockout time ensures that the drug has had enough time to work before the next dose is given, because there is usually a lag of 5-10 minutes between delivery of drug into the epidural catheter and onset of effect. The lockout time protects the mother from giving herself too much drug. If she still feels discomfort from her contraction after the lockout period has elapsed, she may access another dose of medication from the pump by pressing the button.
If analgesia is inadequate, the bolus dose and lockout interval can be adjusted, and/or extra local anaesthetic can be given. Sometimes a continuous background infusion is administered in addition. The mother’s level of comfort and degree of sensory and motor blockade must be assessed on an ongoing basis, particularly as the nature, site and severity of labour pain will vary.
PCEA is a useful and safe alternative for labour analgesia, provided that bolus doses of dilute local anaesthetic are small, that the lockout period and hourly maximum dose are appropriate and that the mother is regularly assessed by the labour ward anaesthetist.
i] Patient-controlled epidural analgesia versus continuous infusion for labour analgesia: a meta-analysis.
van der Vyver M et al.
Br J Anaesth 2002; 89: 459-465.