OFFERING PAIN RELIEF with fewer adverse reactions than systemic analgesia, intraspinal administration of opioids or local anesthetic agents is an effective way to control pain in patients with unrelieved chronic pain and those undergoing major surgical procedures. In this method, a catheter is inserted into the subarachnoid or epidural space at the thoracic or lumbar level (see Picturing intraspinal medication administration). With the subarachnoid route, medication infuses directly into the subarachnoid space and the cerebrospinal fluid that surrounds the spinal cord. With the epidural route, medication is deposited in the dura of the spinal canal and diffuses into the subarachnoid space.

Let's take a closer look at intraspinal medication administration, adverse reactions to be alert for, and what you need to do for your patient who's receiving it.

Pain, pain, go away

For patients who have persistent, severe pain that doesn't respond to other treatments, or who obtain pain relief only with the risk of serious adverse reactions, medication administered by a long-term subarachnoid or epidural catheter may be effective. The health care provider tunnels the catheter through the subcutaneous tissue and places the inlet (or port) under the skin. The medication is then injected through the skin into the inlet and catheter. The patient may need medication injections several times a day to maintain an adequate level of pain relief.

For patients who require more frequent doses or a continuous infusion of an opioid analgesic to relieve pain, an implantable infusion device or pump may be used to administer the medication continuously. The medication is administered in a small, constant dose at a preset rate into the subarachnoid or epidural space. The device's reservoir stores the medication for slow release and needs to be refilled every 1 to 2 months, depending on the patient's needs. This eliminates the need for repeated injections through the skin.

A new delivery method of epidural morphine has been developed that provides effective analgesia for patients who've undergone major surgical procedures. A single dose of an extended-release epidural morphine (Depodur) is administered into the epidural space at the lumbar level immediately before surgery. Depodur has been shown to provide up to 48 hours of post-op analgesia. Although patients who receive Depodur may need supplemental analgesic drugs, they tend to report less intense pain and greater satisfaction with pain relief. It's contraindicated in patients with an allergy to morphine, respiratory depression, severe asthma or upper airway obstruction, and circulatory shock.

Be on the lookout

Adverse reactions associated with intraspinal administration include:

headache from spinal fluid seeping into the spinal canal when the dura is punctured during subarachnoid administration; dural puncture may also occur inadvertently with the epidural route

oversedation and respiratory depression; generally respiratory depression peaks 6 to 12 hours after epidural opioids are administered, but it can occur earlier or up to 24 hours after the first injection

urinary retention

pruritus (itchiness)

nausea

vomiting

dizziness.

Frequent assessment is key

If you're caring for a patient who's receiving medication via intraspinal administration, here's what you need to do:

Assess the patient regularly for headache. If headache develops, keep him positioned flat in bed, give him large amounts of fluids if not contraindicated, and notify the health care provider. Keep in mind that headache from spinal fluid loss may be delayed.

Assess him frequently for decreases in blood pressure, pulse rate, and urine output. Cardiovascular adverse events, such as hypotension, may result from relaxation of the vasculature in the legs.

Monitor him closely for at least 24 hours after the first injection for signs of respiratory depression. A patient receiving opioids should be monitored regularly using a standard sedation scale. Be prepared to administer an opioid antagonist agent, such as naloxone, if respiratory depression occurs.

Administer small doses of naloxone, as ordered, to control urinary retention and pruritus. Naloxone is given as a continuous I.V. infusion that's small enough to reverse the adverse effects of the opioid without reversing the analgesic effects. Diphenhydramine (Benadryl) may also be used to relieve opioid-related pruritus.

Take precautions to prevent infection at the catheter site. Follow the Infusion Nurses Society standards of practice for site care to prevent infection. See "Bad Blood: Tips for Preventing CR-BSIs" from our September/October 2006 issue for steps you can take.

Secure the catheter. Make sure the catheter is stabilized to prevent accidental dislodgment. Commercial stabilization devices are recommended for this purpose. Routinely assess the site and report any signs of redness or fluid leak to the health care provider.

If your patient is to receive an epidural analgesic at home, teach him and his family how to administer the prescribed medication using sterile technique and how to assess for infection. Also make sure the patient and his family know how to recognize adverse reactions and what to do about them.

Spine-tastic!!

Intraspinal medication is an effective way to provide pain relief for patients with chronic pain and post-op patients who've had major surgery. And now you know what you can do to safeguard these patients from adverse effects and keep them pain free!!

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