July/August 2006
Volume 2, Issue 4

      In this Issue:

• Pain Management in the Geriatric Patient Population: Part I
• Intradiscal Electrothermal Therapy (IDET) for Treatment of Discogenic LBP

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Pain Management in the Geriatric Patient Population: Part I

An Original Contribution by Frank J. E. Falco, M.D.

The incidence of pain in the elderly community (= 65 years of age) has been reported between 20 and 50%. Up to 80% of the institutionalized elderly complain of pain.

The physiological changes of aging (cognitive, hepatic, and renal) that have an impact on the pharmacological approach for pain management in the elderly are summarized in the following table:

		Factor		Drug Dosing Effect
		renal clearance		drug & metabolite levels
		hepatic metabolism		drug accumulation
		serum albumin		levels unbound active drug
		compliance		therapeutic end points
		or organ senstivity		iatrogenic effects
		drug interactions		or drug levels

Acetaminophen intervals should be increased with renal dysfunction. It is not recommended with severe liver disease.

CAUTION when using an NSAID as an analgesic for arthritis and inflammatory pain. Sulindac has fewer renal effects and ibuprofen is best for cancer with thrombocytopenia. Never combine NSAIDs with K+ sparing diuretics or ACE inhibitors which will lead to rapid and potentially fatal hyperkalemia. Ibuprofen has been associated with aseptic meningitis in SLE.

Tramadol dosing is limited to < 300 mg/day in those > 75 years old; 200 mg/day for creatinine clearance (CrCl) = 30 ml/min; and 100 mg/day with cirrhosis. Some antidepressants and MAOI can increase the risk of seizures and serotonin syndrome. The analgesic of codeine and tramadol is lost with all SSRIs.

In general, opioid doses for the elderly should be initiated at 25 to 50% of adult doses, started with short acting drugs, advanced slowly, titrated to pain relief or side effects, adjusted for hepatic or liver function and administered with a stool softener. Monitor for side effects especially during the first six half-lives. Opioids do not cause end organ damage and have no direct hepatic or renal toxic effects. They do not irritate the gastric mucosa or inhibit platelet aggregation.

Codeine can release antidiuretic hormones. Morphine dose adjustments are not needed with mild hepatic disease but should be reduced with cirrhosis. Oxycodone is contraindicated in hypercarbia and paralytic ileus. Meperidine and propoxyphene produce nonopioid metabolites that can lead to severe toxic effects and should not be used for managing pain in the elderly. Hydromorphone can lead to myoclonus, increased CSF pressure, and hyperglycemia. Some forms contain tartrazine and should be avoided in hepatic and renal dysfunction. Fentanyl starting doses should be no > than 12.5 to 25 mcg/hr and decreased to 25% of normal doses with CrCl < 50 ml/min. Adverse effects include hypotension, bradycardia, seizures, and muscle rigidity. Methadone clearance is 15 to 25 hours with each dose, therefore use 50 to 75% or less of normal doses if the CrCl is low. Side effects include miosis, lower extremity edema, hypotension, bradycardia, peripheral vasodilation, and choreic movements.

Intradiscal Electrothermal Therapy (IDET) for Treatment of Discogenic LBP

An Original Contribution by Frank J. E. Falco, M.D.

Discogenic low back pain (DLBP) is responsible for at least 40% of chronic LBP. Radial or circumferential tears (IDD) in the outer third of the posterior annulus lead to nociceptor stimulation through inflammatory or mechanical means resulting in acute DLBP. Over time, subsequent nerve in-growth into the annular tears is correlated with the expression of substance P leading to chronic DLBP.

DLBP results from IDD that leads to nerve irritation within the disc. In contrast, a herniated disc leads to mechanical or chemical irritation of nerve roots within the spinal canal resulting in LBP and sciatica.

The symptoms of DLBP are LBP worse with axial loading (sitting, standing or lifting) and better with recumbency. The pain can be referred into the legs but not in a sciatic distribution. Exam findings include muscle spasms, painful range of motion, and painful palpation. The neurological exam and imaging studies are often unremarkable. Discography is the only reliable means of diagnosing DLBP.

The IDET procedure consists of placing a semi-rigid catheter within the posterior annular tear of the painful disc. The area is then heated from 65 to 90°C over 16.5 minutes. The IDET mechanism of action in reducing DLBP is unknown at this time.

Indications for the IDET procedure mandate a positive lumbar discogram. Contraindications include disc degeneration with >50% disc height loss and a previously operated disc. Potential complications include bleeding, infection, and nerve root injury.