Intraspinal morphine for cancer pain

Epidural and intrathecal analgesia for cancer pain

The three-step analgesic ladder approach developed by the World Health Organization works well in treating the vast majority (70-90%) of patients suffering from pain related to cancer. In those patients who do not get pain relief by this three-step approach, intraspinal agents can be a fourth step in managing pain of malignant origin. Although morphine is the only opioid approved by the US Food and Drug Administration for intraspinal use, many different opioid analgesics are used intraspinally, including hydromorphone, fentanyl, sufentanil, meperidine and methadone in the treatment of cancer pain. Many non-opioid agents have also been used intraspinally either alone or in combination with opioids in the treatment of intractable cancer pain. This chapter summarizes the clinical use of these agents with some practical points.

Evidence-based review of the literature on intrathecal delivery of pain medication

Evidence-based medicine depends on the existence of controlled clinical trials that establish the safety and efficacy of specific therapeutic techniques. Many interventions in clinical practice have achieved widespread acceptance despite little evidence to support them in the scientific literature; the critical appraisal of these interventions based on accumulating experience is a goal of medicine. To clarify the current state of knowledge concerning the use of various drugs for intraspinal infusion in pain management, an expert panel conducted a thorough review of the published literature. The exhaustive review included 5 different groups of compounds, with morphine and bupivacaine yielding the most citations in the literature. The need for additional large published controlled studies was highlighted by this review, especially for promising agents that have been shown to be safe and efficacious in recent clinical studies.

The development of morphine tolerance and dependence in rats with chronic pain

The development of tolerance and dependence to morphine injected onto the spinal cord was examined in a model of chronic pain following spinal cord injury in rats. Intrathecal morphine completely relieved the marked pain-like response of these rats to innocuous mechanical stimuli. The analgesic effect of morphine injected twice daily was, however, diminished within a few days. Tolerance to the antinociceptive effect of morphine assessed with the tail flick test also developed similarly in rats with chronic pain and in normal controls. Both groups exhibited similar signs of naloxone-precipitated withdrawal after 3 weeks of morphine treatment. The results suggest that the presence of chronic pain-like behavior did not prevent the development of morphine tolerance and dependence, even when morphine was used to treat the chronic pain itself.

Spinal epidural metastasis: implications for spinal analgesia to treat "refractory" cancer pain

Two hundred one consecutive patients with cancer pain who received intrathecal pain treatment between 1985 and 1993 were included in this retrospective study undertaken to test the hypothesis that epidural metastasis is a common cause of "refractory" cancer pain and that its presence may affect the efficacy and the complication rates of intraspinal pain treatment. Fifty-seven (approximately 28%) patients were investigated by metrizamide myelography, computerized tomography (CT), magnetic resonance imaging (MRI), laminectomy, or neurohistopathology. Epidural metastases were found in 40 (70%) and spinal stenosis in 33 (approximately 58%); 7 patients with total and 26 with partial occlusion of the spinal canal. Presence of epidural metastasis affected catheter insertion complications, daily dosages, and complications of the intrathecal pain treatment only when it was associated with spinal canal stenosis (partial or total). During the period of the intrathecal treatment, the patients with confirmed epidural metastasis and total spinal canal stenosis needed significantly (P < 0.05) higher daily doses of opioid (means = 77 +/- 103 versus 22 +/- 29 mg) and intrathecal bupivacaine (means = 65 +/- 44 versus 33 +/- 20 mg) and had significantly (P < 0.05) higher rates (14% versus 0%) of radicular pain at injection and poor distribution of analgesia than those without epidural metastasis and spinal canal stenosis. In contrast, the rate of occurrence of post-dural puncture headache was significantly (P < 0.05) lower in patients with partial (4%) and total (14%) spinal stenosis than in those without (29%). Unexpected paraplegia occurred in four patients and was due to accidental injury during attempted dural puncture (N = 1) and collapse (due to cerebrospinal fluid leakage leading to "medullary coning" of an unknown epidural metastasis (N = 3).

Long-term intraspinal infusions of opioids in the treatment of neuropathic pain

Long-term intraspinal infusions of opioid drugs are being increasingly utilized in patients with noncancer pain. Despite this, there is a lack of long-term information, including success and failure rates for pain relief and technical problems. During a 5-year period, 18 noncancer patients underwent implantation of programmable infusion pumps for long-term intrathecal opioid infusion. Patients had (a) neuropathic pain, (b) had failed or been ineligible for noninvasive treatments, and (c) obtained greater than 50% pain relief with intrathecal trial infusions of morphine sulfate or sufentanil citrate. A disinterested third-party reviewer evaluated patients at the most recent follow-up. Sixty-one percent (11/18) of patients had good or fair pain relief with mean follow-up 2.4 +/- 0.3 years (0.8-4.7 years). Average numeric pain scores decreased by 39% +/- 4.3%. Five of the 11 responders required lower opioid doses (12-24 mg/day morphine) and the remaining six patients required higher opioid doses (> 34 mg/day morphine). Failure of long-term pain relief occurred in 39% (7/18) despite good pain relief in trial infusions and the use of both morphine and sufentanil. Technical problems developed in 6/18 patients but appeared to be preventable with further experience. Long-term intrathecal opioid infusions can be effective in treatment of neuropathic pain but might require higher infusion doses.

Epidural clonidine analgesia for intractable cancer pain. The Epidural Clonidine Study Group

Although the vast majority of patients with cancer pain receive effective analgesia from standard therapy, a few patients, particularly those with neuropathic pain, continue to experience severe pain despite large doses of systemic or intraspinal opioids. Animal studies suggest intraspinal alpha 2-adrenergic agonists may be effective in such cases. Eighty-five patients with severe cancer pain despite large doses of opioids or with therapy-limiting side effects from opioids were randomized to receive, in a double-blind manner, 30 micrograms/h epidural clonidine or placebo for 14 days, together with rescue epidural morphine. Pain was assessed by visual analog score (VAS), McGill Pain Questionnaire, and daily epidural morphine use. Success was defined as a decrease in either morphine use of VAS pain, with the alternative variable either decreasing or remaining constant. Blood pressure, heart rate, and degree of nausea and sedation were monitored. Successful analgesia was more common with epidural clonidine (45%) than with placebo (21%). This was particularly prominent in those with neuropathic pain (56% vs. 5%). Pain scores were lower at the end of the treatment period in patients with neuropathic pain treated with clonidine rather than placebo, whereas morphine use was unaffected. Clonidine, but not placebo, decreased blood pressure and heart rate. Hypotension was considered a serious complication in 2 patients receiving clonidine and in 1 patient receiving placebo. This study confirms the findings from previous animal studies which showed the effective, potent analgesic properties of intraspinal alpha 2-adrenergic agonists and suggests that epidural clonidine may provide effective relief for intractable cancer pain, particular of the neuropathic type.

Intrathecal morphine and bupivacaine in advanced cancer pain patients implanted at home

Fifteen patients with pain due to advanced cancer who no longer obtained relief from conventional treatment using oral or parenteral opioids were administered morphine and bupivacaine by continuous intrathecal infusion. Thirteen patients were implanted at home due to poor medical condition or refusal to be hospitalized. A summary score was derived to monitor the effects of the treatment. Thirteen patients required low doses of intrathecal morphine and bupivacaine and all reported good pain relief until death. Only minor side effects were evidenced. Implantation at home of an intrathecal catheter to administer morphine and bupivacaine provided a degree of pain relief during the last days of life that would have otherwise been impossible and did so without producing important complications.

Pathophysiology of pain

OBJECTIVE

To review the pain pathways in the central and peripheral nervous system and the actions of drugs used to treat pain.

DESIGN

An overview of pain pathways is presented, beginning in the periphery and progressing centrally, and the ascending and descending pathways are described in detail.

RESULTS

The nociceptive pathway, consisting of the classic three-neuron chain, is now understood to be a dual system at each level, and the sensation of pain is thought to arrive in the central nervous system with the discriminative component of pain ("first pain") carried separately from the affective-motivational component of pain ("second pain"). In addition to spinal control mechanisms of nociceptive transmission, descending pathways that originate in three major areas--the cortex, thalamus, and brain stem--can modify functions at the spinal level. At every level of the nervous system, a close relationship prevails between somatic pain pathways and visceral pathways. This relationship likely accounts for the transmission of visceral pain and also for autonomic responses to somatic pain and somatic responses to visceral pain.

CONCLUSION

By understanding the pathways of pain and the transmitters involved, prevention and treatment of pain will be improved.

Long-term intrathecal infusion of morphine and morphine/bupivacaine mixtures in the treatment of cancer pain: a retrospective analysis of 51 cases

A retrospective analysis of 51 patients with cancer pain treated with a continuous i.t. morphine infusion through a tunnelled percutaneous catheter was undertaken. Because of insufficient pain relief with morphine only, 17 of these patients received a morphine/bupivacaine mixture. Pain relief subsequently improved significantly in 10 patients and a moderate improvement was present in 4 patients. An additional analgesic effect of bupivacaine was not shown in 3 patients with clinical signs of severe mental depression. Bupivacaine-induced side effects were absent below a daily dosage of 30 mg by continuous infusion. In all patients a gradual dose increment was observed. No serious complications, neurologic sequelae or meningitis occurred. It is concluded that long-term i.t. infusion of morphine through a tunnelled catheter can provide adequate pain relief in cancer patients with an acceptable risk-benefit ratio. The effects of long-term intrathecal co-administration of local anesthetics, especially bupivacaine, await further prospective evaluation.

The threshold for the depressive effect of intrathecal morphine on the spinal nociceptive flexor reflex is increased during autotomy after sciatic nerve section in rats

The effect of intrathecal (i.t.) morphine on the spinal nociceptive flexor reflex in doses ranging between 10 ng and 10 micrograms was studied in decerebrate, spinalized, unanesthetized rats with intact sciatic nerves or in rats in which the sciatic nerve had been unilaterally sectioned. In rats with intact nerves the initial effect of i.t. morphine on the flexor reflex was a brief facilitation followed by depression. The threshold dose of morphine for reflex depression was 100 ng. In animals which did not develop autotomy after nerve section or in which autotomy had ceased for several days prior to the acute experiments, i.t. morphine had a similar depressive effect on the flexor reflex as in animals with intact nerves. However, in rats which were autotomizing at the time of the acute experiment, the threshold dose of the depressive effect of morphine was increased 3-5 fold. With higher doses of morphine (1-3 micrograms), similar depression of the reflex was found in all groups. The present results revealed a decreased sensitivity of spinal reflex mechanisms to low, but not high, doses of morphine after sciatic nerve section accompanied by autotomy. Nerve section per se did not alter opioid sensitivity. Thus, decreased effectiveness of morphine in this model for neuropathic pain may be partially due to a desensitization to the analgesic action of opioids in the spinal cord. Since after sciatic nerve section there is a differential sensitivity to the antinociceptive effect of i.t. morphine between autotomizing and non-autotomizing rats, it is further suggested that autotomy after peripheral nerve section in rats is a useful model for the study of neuropathic pain.

Long-term intrathecal morphine and bupivacaine in "refractory" cancer pain. I. Results from the first series of 52 patients

Neither epidural (EDA) or intrathecal (IT) morphine nor EDA opiate + bupivacaine provides acceptable relief of some types of cancer pain, e.g. pain originating from mucocutaneous ulcers, deafferentation pain, continuous and intermittent visceral and ischaemic pain, and that occurring with body movement as a result of a fracture. To improve pain relief in such conditions, we gave combinations of morphine and bupivacaine through open IT-catheters to 52 patients with "refractory", severe (VAS 7-10 out of 10), complex cancer pain (Edmonton Stage-3), for periods of 1-305 (median = 23) days. The efficacy of the treatment was estimated from: 1) daily dosage (intraspinal and total opiates, and intraspinal bupivacaine), and 2) scores of non-opiate analgesic and sedative consumption, gait and daily activities, and amount and pattern of sleep. Forty-four patients obtained continuous and acceptable pain relief (VAS 0-2), 26 of them with daily doses of IT-bupivacaine of less than or equal to 30 mg/day (less than or equal to 1.5 mg/h). Higher IT-bupivacaine doses (greater than 60-305 mg/day), not always giving acceptable pain relief, were necessary in 13 patients with deafferentation pain from the spinal cord or brachial or lumbosacral plexuses or pain from the coeliac plexus, or from large, ulcerated mucocutaneous tumours. By combining IT-bupivacaine with IT-morphine, it was possible to use relatively low IT-morphine doses (10-25 mg/day during the first 2 months of treatment) in more than half of the patients. The IT-treatment significantly decreased the total (all routes) opiate consumption and significantly improved sleep, gait and daily activities. For the whole period of observation (6 months), the IT-treatment was assessed as adequate in 3.8%, good in 23.1%, very good in 59.6% and excellent in 13.5% of the cases. Adverse effects of the IT-bupivacaine (paraesthesiae, paresis, gait impairment, urinary retention, anal sphincter disturbances and orthostatic hypotension) did not occur with doses of 2.5-3.0 mg/h (approx. 60-70 mg/day).

Constant infusion of morphine for intractable cancer pain using an implanted pump

In the past, pain control for chronic pain syndromes using narcotic infusion has been carried out primarily via the intrathecal (subarachnoid) route. This report presents one of the first large series of terminally ill cancer patients with intractable pain treated with continuous epidural morphine infusions by means of implanted pumps and epidural spinal catheters. The purpose of the study was to demonstrate that the epidural route is effective with minimal complications, and that screening with temporary epidural catheter infusions results in a high rate of subsequent pain relief. A multidisciplinary team (neurosurgeon, anesthesiologists, psychiatrists, oncologists, and nurse clinicians) evaluated and treated all of the patients studied. Percutaneous placement of temporary epidural catheters for a trial assessment was performed by the anesthesiologists. Pain evaluations were conducted independently by psychiatrists using both verbal and visual analog scales. From 1982 to 1988, 41 (59.4%) of 69 patients evaluated for eligibility experienced good pain control during trial assessment and were subsequently implanted with Infusaid infusion pumps. Preinfusion pain analog values were 8.6 +/- 0.3 and postimplantation values at 1 month were 3.8 +/- 0.4 (p less than 0.001). Over this same 1-month period. requirements of systemic morphine equivalents decreased by 79.3% with epidural infusions as compared to preinfusion requirements (p less than 0.001). There were no instances of epidural scarring, respiratory depression, epidural infections, meningitis, or catheter blockage. One patient developed apparent drug tolerance and three patients required further catheter manipulations. This series strongly suggests that significant reductions in cancer pain can be obtained with few complications and a low morphine tolerance rate using chronic epidural morphine infusion. Anesthesiology and psychiatry input, along with temporary catheter infusion screening and quantitative pain evaluations using analog scales, are essential.