14 Nov Who is a Candidate for an Intrathecal Pump Implant?
Pain is the most common reason why people visit the doctor. When pain persists, it can place much emotional, psychological, and economic strain on patients and their family members. Chronic pain affects around 15% of the general population, with 2/3 of people reporting pain that has persisted for more than 5 years.
In a recent study, 36 million people in the United States missed work because of pain. Additionally, a recent report found that of people who suffer from neuropathic pain, 75% visit the doctor at least once a month. Due to chronic pain, employment status is affected for half of people, with the average workdays lost per month being 5.5. Because chronic pain is such a problem, one solution is the intrathecal pump implant.
Intrathecal analgesia was first used for pain relief in 1900. However, continuous spinal analgesia started in the 1940s. Many studies have shown the safety and efficacy of this modality since then. The use of opioids for chronic pain is a more recent application, but it still remains controversial due to fear of drug addiction and medication tolerance. Intrathecal drug delivery systems are implanted in the body when conservative treatments have failed and surgery is ruled out.
The intrathecal pump delivers small doses of a drug directly to the spinal fluid. The device is a small battery-powered pump that is placed under the subcutaneous tissue of the lower abdomen. The pump connects to a small catheter that is tunneled under the skin and placed inside the epidural space (around the spinal cord). The pump needs to be refilled every 1-3 months.
Not everyone is a candidate for the intrathecal drug delivery system. Patients are divided into categories: those suffering from a terminal illness and those with chronic, persistent pain. Terminal cancer patients usually respond to intrathecal opioid administration. Those with chronic non-malignant pain are carefully selected for the intrathecal pain pump. The physician will first be sure that the patient has tried (and failed) numerous approaches for pain management.
Before the intrathecal drug delivery system is surgically implanted for chronic pain, the surgeon makes sure that no active or untreated addiction exists. This involves intensive psychological testing beforehand. Medical contraindications include an infection, a bleeding disorder, and an unsuccessful intrathecal drug trial.
Medications Used in Implantable Drug Delivery Systems
The first line treatment for chronic pain includes hydromorphone and morphine. Recent clinical studies support that these drugs provide effective analgesia in people with chronic refractory pain. The second line of treatment is aimed at people with prominent neuropathic pain. This consists of morphine or hydromorphone with the addiction of clonidine (adrenergic agonist) or bupivacaine (local anesthetic).
Third line agents are combinations chosen after failure on first and second line drug combinations, either from inadequate analgesia or side effects. This drug combination includes adding clonidine and bupivacaine to either hydromorphone or morphine. Fourth line agents include gamma -aminobutyric acid (GABA) agonists, such as midolazam and baclofen, and lipophilic opioid agents, such as fentanyl.
Efficacy and Outcomes
In a recent clinical study, researchers assessed long-term follow-up of quality of life and efficacy for 34 geriatric patients with intrathecal pump implants for severe, non-cancer chronic pain. According to the study, pain intensity was significantly reduced at 3-month follow-up, with a success rate of 60%. In addition, visual analog scale pain scores decreased from 8 to 1.68.
Knight KH, Brand FM, Mchaourab AS, & Veneiano G (2007). Implantable Intrathecal Pumps for Chronic Pain: Highlights and Updates. Croat Med J, 48(1), 22-34.
Raffaeli W, Righetti D, Caminiti A, et al. (2008). Implantable intrathecal pumps for the treatment of noncancer chronic pain in elderly population: drug dose and clinical efficacy. Neuromodulation, 11(1), 33-39.