Which opioids and adjuvants are commonly used in the subarachnoid and epidural spaces?

Which opioids and adjuvants are commonly used in the subarachnoid and epidural spaces?

Morphine and fentanyl are the opioids most commonly used for neuraxial epidural analgesia. Because of its longer duration of action, morphine is the drug of choice when subarachnoid analgesia is desired. Although both epidural morphine and fentanyl can be used with a bolus dosing technique, a continuous infusion of either is desirable to provide continuous, titratable analgesia. Fentanyl has gained tremendous popularity for epidural use because of its quick onset of action and shorter duration, once adminis-tration is terminated. Neuraxial hydromorphone has been used by some practices, as an opioid with properties in between those of morphine and fentanyl in terms of duration of action.

Current practice is to use the lowest dose possible to obtain the best analgesia with the lowest incidence of side effects. Table 72.2 outlines dosage guidelines.

For enhanced analgesia, 0.0625–0.1% bupivacaine is often added to continuous epidural fentanyl infusions. Even with such low concentrations, partial sensory, autonomic, and motor dysfunction may occur, recovery from which must be documented before allowing the patient to ambulate.

Epidural clonidine has been investigated for the use in the treatment of postoperative pain. Although it is an effective analgesic, its widespread use has been limited because of associated hypotension.