The addition of opioids to local anaesthetic solution has gained popularity as opioids have synergistic effect by acting directly on opioid receptors in the spinal cord.Opioids such as morphine ,fentanyl and diamorphine have been used both alone and in combination with local anasthetic drugs, during labour, for intraoperative use and for postoperative analgesia. The combination of low concentration local anasthetic and low-concentration of opioids has shown to be very very effective in the management of postoperative pain. the amount of opioid eg. diamorphine should be decreased when there is a increased risk of respiratory depression, ie. the elderly, very frail patients or in patients with significant chronic obstructive airway disease. Caution should be exercised when morphine is administered epidurally, as it is associated with delayed respiratory depression. Opiods have also been used on their own in epidural space. Pethidine , in particular has a structure similar to local anasthetics and is effective in providing surgical anasthesia and postoperative analgesia.
The advantages of epidural opioids:
Only sensory block is produced
The effect of single dose lasts long obviating the need for frequent injections.
No sympathetic block.
The disadvantages of epidural opioids:
Nausea and Vomitting