Author(s): Gary M. Reisfield, M.D. and George R. Wilson, M.D.
Background
Intrathecal drug delivery can be an invaluable adjunct in the management of severe pain when meticulous application of conventional drug therapy proves ineffective or produces intolerable side effects. Intrathecal analgesia is distinguished from epidural analgesia by catheter location within the neuraxis (see Fast Fact #85). In the former, the catheter lies within the subarachnoid space, where small quantities of medication have direct access to spinal drug receptor sites. In the latter, larger doses of medication (necessitated by epidural fat and vascular uptake) must diffuse across the dura to reach these receptors.
Epidural vs. Intrathecal Analgesia
Potential advantages of intrathecal – relative to epidural – techniques are:
Choice of System
There exists a spectrum of intrathecal system options – from a simple, percutaneous catheter/external pump to a totally implanted system. Choice is based on life expectancy, performance status, and available professional expertise. Pharmacoeconomic modeling suggests that the percutaneous catheter may be the most economic option for patients with prognoses of days to a few months.
Drug Choice
Arner and Arner (1985) demonstrated a relative responsiveness of pain mechanisms to intraspinal opioids as follows: continuous somatic pain > continuous visceral > intermittent somatic > intermittent visceral > neuropathic > cutaneous (ulcers or fistulas). An opioid alone is likely to be effective for nociceptive pain syndromes. The addition of coanalgesics, including local anesthetics and/or clonidine, is usually necessary for neuropathic pain syndromes. Ziconotide, a relatively new N-type calcium channel blocker, may have a role in pain syndromes refractory to traditional intrathecal opioids and coanalgesics. Frequency of adverse CNS effects (e.g. confusion, somnolence, dizziness), may be attenuated by slow titration. Experience with this drug in the palliative care setting is limited.
Complications and Side Effects
Complications may occur from a) the procedure (e.g. post-spinal headache), b) medications (e.g. opioid-related respiratory depression, sedation, urinary retention, pruritis), and c) hardware (e.g. catheter kinking/disconnection/dislodgement, infection). Major contraindications to intrathecal catheter placement include coagulopathy, infection at catheter insertion site, and sepsis.
Fast Facts are edited by Drew A. Rosielle MD, Palliative Care Center, Medical College of Wisconsin. For comments/questions write to: drosiell@mcw.edu. The complete set of Fast Facts is available at EPERC: www.eperc.mcw.edu.
Copyright/Referencing Information: Users are free to download and distribute Fast Facts for educational purposes only. Reisfield GM and Wilson GR. Fast Fact and Concept #98. Intrathecal Drug Therapy for Pain. 2nd Edition. November 2007. End-of-Life/Palliative Education Resource Center ( www.eperc.mcw.edu).
Disclaimer: Fast Facts provide educational information. This information is not medical advice. Health care providers should exercise their own independent clinical judgment. Some Fast Fact information cites the use of a product in dosage, for an indication, or in a manner other than that recommended in the product labeling. Accordingly, the official prescribing information should be consulted before any such product is used.
Creation Date: 1/2008
Purpose: Instructional Aid, Self-Study Guide, Teaching
Audience(s)
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Training: Fellows, 3rd/4th Year Medical Students, PGY1 (Interns), PGY2-6, Physicians in Practice |
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Specialty: Anesthesiology, Emergency Medicine, Family Medicine, General Internal Medicine, Geriatrics, Hematology/Oncology, Neurology, OB/GYN, Ophthalmology, Pulmonary/Critical Care, Pediatrics, Psychiatry, Surgery |
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Non-Physician: Nurses |
ACGME Competencies: Medical Knowledge, Patient Care
Keyword(s): Addiction, Chronic non-malignant pain, Controlled substance regulations, Pain, Pain assessment, Pain treatment