Cancer pain relief using chronic morphine infusion. Early experience with a programmable implanted drug pump

Injury and Liability Associated with Implantable Devices for Chronic Pain

BACKGROUND

Due to an increase in implantable device-related anesthesia pain medicine claims, the authors investigated anesthesia liability associated with these devices.

METHODS

After institutional review board approval, the authors identified 148 pain medicine device claims from 1990 or later in the Anesthesia Closed Claims Project Database. Device-related damaging events included medication administration events, infections, hematomas, retained catheter fragments, cerebrospinal fluid leaks, cord or cauda equina trauma, device placed at wrong level, stimulator incorrectly programmed, delay in recognition of granuloma formation, and other issues.

RESULTS

The most common devices were implantable drug delivery systems (IDDS; 64%) and spinal cord stimulators (29%). Device-related care consisted of surgical device procedures (n = 107) and IDDS maintenance (n = 41). Severity of injury was greater in IDDS maintenance claims (56% death or severe permanent injury) than in surgical device procedures (26%, P < 0.001). Death and brain damage in IDDS maintenance claims resulted from medication administration errors (n = 13; 32%); spinal cord injury resulted from delayed recognition of granuloma formation (n = 9; 22%). The most common damaging events for surgical device procedures were infections, inadequate pain relief, cord trauma, retained catheter fragments, and subcutaneous hygroma. Care was more commonly assessed as less than appropriate (78%) and payments more common (63%) in IDDS maintenance than in surgical device procedure claims (P < 0.001).

CONCLUSIONS

Half of IDDS maintenance claims were associated with death or permanent severe injury, most commonly from medication errors or failure to recognize progressive neurologic deterioration. Practitioners implanting or managing devices for chronic pain should exercise caution in these areas to minimize patient harm.

Evidence-based Clinical Practice Guidelines for Interventional Pain Management in Cancer Pain

Intractable cancer pain not amenable to standard oral or parenteral analgesics is a horrifying truth in 10-15% of patients. Interventional pain management techniques are an indispensable arsenal in pain physician's armamentarium for severe, intractable pain and can be broadly classified into neuroablative and neuromodulation techniques. An array of neurolytic techniques (chemical, thermal, or surgical) can be employed for ablation of individual nerve fibers, plexuses, or intrathecalneurolysis in patients with resistant pain and short life-expectancy. Neuraxial administration of drugs and spinal cord stimulation to modulate or alter the pain perception constitutes the most frequently employed neuromodulation techniques. Lately, there is a rising call for early introduction of interventional techniques in carefully selected patients simultaneously or even before starting strong opioids. After decades of empirical use, it is the need of the hour to head towards professionalism and standardization in order to secure credibility of specialization and those practicing it. Even though the interventional management has found a definite place in cancer pain, there is a dearth of evidence-based practice guidelines for interventional therapies in cancer pain. This may be because of paucity of good quality randomized controlled trials (RCTs) evaluating their safety and efficacy in cancer pain. Laying standardized guidelines based on existing and emerging evidence will act as a foundation step towards strengthening, credentialing, and dissemination of the specialty of interventional cancer pain management. This will also ensure an improved decision-making and quality of life (QoL) of the suffering patients.

WITHDRAWN: Comparative efficacy of epidural, subarachnoid, and intracerebroventricular opioids in patients with pain due to cancer

2013: This review is now being updated by a new author team. The publication of the protocol is expected in late 2013.

October 2015: after discussion with the authors and PaPaS editors, the decision was made to halt the development of the protocol that was being planned to replace and update this review. It was felt that the review question was no longer a priority.

The editorial group responsible for this previously published document have withdrawn it from publication.

Intramedullary placement of intrathecal catheter. Report of a rare complication of intrathecal therapy

A rare complication of intrathecal drug therapy-inadvertent insertion of the intrathecal catheter into the matter of the spinal cord-is presented. The patient developed signs of progressive monoparesis immediately after implantation of an intrathecal drug delivery system. The underlying problem was diagnosed with computed tomographic (CT) myelography and magnetic resonance imaging. The symptoms resolved after the catheter was removed. The article discusses probable mechanism of the complication and possible ways of its prevention. The usefulness of CT myelography in determining the intrathecal catheter position relative to the spinal cord is emphasized.

A successful palliative care intervention for cancer pain refractory to intrathecal analgesia

Intrathecal delivery of opioid medications has been increasingly used to treat cancer pain that is refractory to conventional oral opioid therapy. We present a patient with complex and refractory cancer pain who failed both oral and intrathecal opioid therapy but responded to the interdisciplinary palliative care intervention in the acute palliative care unit. His morphine equivalent daily dose decreased by 94% over a 10-day period, and he had better pain control and improved function. This case highlights the importance of addressing and treating the psychosocial distress that contributes to the total pain expression.

A review of intrathecal morphine therapy related granulomas

The development of catheter associated granulomatous masses in intrathecal morphine therapy is an uncommon, but potentially serious problem. While these systems have historically been used in patients with short life expectancies, more recently patients with pain from a benign source have benefited from this therapy, and new complications are being encountered secondary to the patients' longer life spans. Morphine is the most commonly used intrathecal opioid and evidence exists that the formation of granulomatous masses are related to the use of higher doses. When the patients' requirement of morphine increases significantly, the physician should be alert for signs of spinal cord compression, such as new neurological deficits, myelopathy, or radiculopathy. Patients that require these higher doses should be properly informed of the association with granulomas and their associated risks. Indolent infection may also be the etiology of granulomatous masses, and the presence of organisms, both aerobic and anaerobic, should be routinely investigated. Patients with catheter-associated granulomas appear to share several features. They exhibit the onset of symptoms several months following the initiation of intraspinal opioids and commonly present with an increase in pain that precedes signs and symptoms of neurological deterioration. While MRI might be the preferred method of detection of intrathecal granulomas, its cost and availability are prohibitive for routine screening. CT myelogram via pump side port injection of contrast can also be performed to detect catheter tip related granulomas/obstructions. Serial neurological examinations for new deficits may be performed and recorded during pump refill visits to recognize a granulomatous mass in its early stages. If an abnormality is identified, imaging studies are appropriate. Awareness of the condition and vigilance are the keys to successful management of this complication.

Spinal opioids in adult patients with cancer pain: a systematic review: a European Palliative Care Research Collaborative (EPCRC) opioid guidelines project

BACKGROUND

A systematic review, undertaken according to an initiative to revise European Association for Palliative Care guidelines on the use of opioids for cancer pain, which aimed to analyse analgesic efficacy and side effects of spinal opioids in adult cancer patients previously treated with systemic opioids.

METHODS

Search strategy elaborated with MeSH terms and words related to cancer, palliative care, pain, spinal route and opioids. PubMed, Embase and Cochrane assessed in Nov 2009. Studies were analysed and classified according to quality of evidence and strength of recommendation.

RESULTS

Out of 2939 abstracts, 44 articles were selected (nine randomized controlled trials (RCTs), two non-randomized cohort studies, 28 uncontrolled prospective studies, and five case series). Relief of pain and/or side effects were reported in 42 articles; however, there were few studies of high quality design (RCTs) and these studies had methodological limitations that reduced their quality of evidence to very low.

CONCLUSION

There are few RCTs and these are of very low quality. As a result, they provide weak recommendation for using spinal opioids in adult cancer patients. Further studies are clearly needed.

Long term intrathecal infusion of opiates for treatment of failed back surgery syndrome

Failed Back Surgery Syndrome (FBSS) is a multidimensional painful condition and its treatment remains a challenge for the surgeons. Prolonged intrathecal infusion of opiates for treatment of noncancer pain also remains a controversial issue. The authors present a prospective study about the long-term treatment of 30 patients with nonmalignant pain treated with intrathecal infusion of morphine from February, 1996 to May, 2004. Self-administration pumps were implanted in 18 patients and constant-flow pumps in 12. The mean intensity of pain reduced from 9.5 to 4.6 according to the visual analogue scale (p < 0.001); the mean daily dose of morphine necessary for pain control became constant after the sixth month of treatment. No difference was observed in the results between patients treated with bolus or constant infusion. Side effects were more frequent at the beginning and became tolerable after the first month of treatment. There was improvement of the quality of life measured by SF-36 (30.8-49.6) and in all dimensions of the Treatment of Pain Survey, except for working capacity. The follow-up period ranged from 18 to 98 months (mean = 46.7 months). It was concluded that intrathecal infusion of morphine is a useful and safe tool for long-term treatment of chronic nonmalignant pain.

Micropump based on electroosmosis of the second kind

A microfluidic pump based on electroosmosis of the second kind was designed and fabricated. Experimental results using DC and AC voltages showed a close to second-order relationship between flow and voltage, in good agreement with theory. The experimental flow rates were considerably lower than the predicted maximum for the micropumps, which can be attributed to the hydrodynamic resistance of the channel network. This also indicates that higher flow velocities are obtainable for modified pump designs.

The Role of Interventional Therapies in Cancer Pain Management

Cancer pain is complex and multifactorial. Most cancer pain can be effectively controlled using analgesics in accordance to the WHO analgesic ladder. However, in a small but significant percentage of cancer patients, systemic analgesics fail to provide adequate control of cancer pain. These cancer patients can also suffer from intolerable adverse effects of drug therapy or intractable cancer pain in advance disease. Though the prognosis of these cancer patients is often very limited, the pain relief, reduced medical costs and improvement in function and quality of life from a wide variety of available interventional procedures is extremely invaluable. These interventions can be used as sole agents or as useful adjuncts to supplement analgesics. This review will discuss interventional procedures such as epidural and intrathecal drug infusions, intrathecal neurolysis, sympathetic nervous system blockade, nerve blocks, vertebroplasty and the more invasive neurosurgical procedures. Intrathecal medications including opioids, local anaesthetics, clonidine, and ziconotide will also be discussed. Key words: Intractable pain, Intrathecal analgesia, Neurolysis

Interventional pain treatments for cancer pain

Cancer pain is prevalent and often multifactorial. For a segment of the cancer pain population, pain control remains inadequate despite full compliance with the WHO analgesic guidelines including use of co-analgesics. The failure to obtain acceptable pain or symptom relief prompted the inclusion of a fourth step to the WHO analgesic ladder, which includes advanced interventional approaches. Interventional pain-relieving therapies can be indispensable allies in the quest for pain reduction among cancer patients suffering from refractory pain. There are a variety of techniques used by interventional pain physicians, which may be grossly divided into modalities affecting the spinal canal (e.g., intrathecal or epidural space), called neuraxial techniques and those that target individual nerves or nerve bundles, termed neurolytic techniques. An array of intrathecal medications are infused into the cerebrospinal fluid in an attempt to relieve refractory cancer pain, reduce disabling adverse effects of systemic analgesics, and promote a higher quality of life. These intrathecal medications include opioids, local anesthetics, clonidine, and ziconotide. Intrathecal and epidural infusions can serve as useful methods of delivering analgesics quickly and safely. Spinal delivery of drugs for the treatment of chronic pain by means of an implantable drug delivery system (IDDS) began in the 1980s. Both intrathecal and epidural neurolysis can be effective in managing intractable cancer-related pain. There are several sites for neurolytic blockade of the sympathetic nervous system for the treatment of cancer pain. The more common sites include the celiac plexus, superior hypogastric plexus, and ganglion impar. Today, interventional pain-relieving approaches should be considered a critical component of a multifaceted therapeutic program of cancer pain relief.

Nonstationary electroosmotic flow in open cylindrical capillaries

A theoretical model of the EOF established in a wide capillary after the application of a stepwise voltage has been developed. Both periodical and aperiodical flow regimes were studied with arbitrary pulse/pulse or pulse/pause durations and amplitudes. The numerical analysis performed for a few types of periodical regimes showed the peculiarities of the profiles of liquid velocity and its displacement both for the transition to the stationary regime and for the quasi-stationary periodical and aperiodical regimes.

Comparative efficacy of epidural, subarachnoid, and intracerebroventricular opioids in patients with pain due to cancer

BACKGROUND

Since the 1970s, when endogenous opioids and opioid receptors were first isolated in the central nervous system, attempts have been made to optimize opioid therapy by delivering the medication centrally rather than systemically. Although the vast majority of cancer patients obtain satisfactory pain relief from individualized systemic treatment, there remain the few whose pain is refractory to systemic treatments. These patients may obtain relief from neuraxial opioid therapy: intracerebroventricular, epidural or subarachnoid.

OBJECTIVES

To compare intracerebroventricular therapy with other neuraxial treatments and to determine whether intracerebroventricular (ICV) has anything to offer over epidural (EPI) and subarachnoid (SA) catheters in terms of efficacy, adverse effects, and complications.

SEARCH STRATEGY

A number of electronic databases were searched to retrieve information for inclusion in this review. Non-English language reports are awaiting assessment. Unpublished data were not sought.

SELECTION CRITERIA

Randomised studies of intracerebroventricular therapy for patients with intractable cancer pain were sought. However, this level of evidence was not available so data from uncontrolled trials, retrospective case series and uncontrolled prospective cohort studies were assessed.

DATA COLLECTION AND ANALYSIS

Our search did not retrieve any controlled trials. We therefore used data from uncontrolled studies to compare incidences of analgesic efficacy, adverse effects, and complications. We found 72 uncontrolled trials assessing ICV (13 trials, 337 patients), EPI (31 trials, 1343 patients), and SA (28 trials, 722 patients) in cancer patients. From these we extracted data on analgesic efficacy, common pharmacologic adverse effects, and complications.

MAIN RESULTS

Data from uncontrolled studies reported excellent pain relief among 73% of ICV patients compared with 72% EPI and 62% SA. Unsatisfactory pain relief was low in all treatment groups. Persistent nausea, persistent and transient urinary retention, transient pruritus, and constipation occurred more frequently with EPI and SA. Respiratory depression, sedation and confusion were most common with ICV. The incidence of major infection when pumps were used with EPI and SA was zero. There was a lower incidence of other complications with ICV therapy than with EPI or SA.

AUTHORS' CONCLUSIONS

Neuraxial opioid therapy is often effective for treating cancer pain that has not been adequately controlled by systemic treatment. However, long-term use of neuraxial therapy can be complicated by problems associated with the catheters. The data from uncontrolled studies suggests that ICV is at least as effective against pain as other neuraxial treatments and may be a successful treatment for patients whose cancer pain is resistant to other treatments.

Stability of clonidine in clonidine-hydromorphone mixture from implanted intrathecal infusion pumps in chronic pain patients

Clonidine is frequently added to opioids in implantable intrathecal pumps for the management of chronic pain. In such devices, a small non-retrievable volume is always present in the reservoir, and its effect on drug stability is unknown. Furthermore, stability of clonidine, when mixed with hydromorphone, has not been previously determined. This study examined the stability of clonidine when co-administered with hydromorphone in implanted intrathecal pumps. Samples of hydromorphone-clonidine before pump refill and from residual solution at subsequent refill were obtained from chronic pain patients. Clonidine concentration was measured using HPLC. Twenty paired samples from 3 patients were analyzed. All 3 patients had a SynchroMed pump implanted for 3-5 years. We found no loss in clonidine concentration during the time between refills (35 +/- 13 days), and no correlation between clonidine concentration and time interval between refills. In conclusion, clonidine, mixed with hydromorphone, is stable when delivered by implantable intrathecal pump for long-term use.

Evolving spinal analgesia practice in palliative care

Intraspinal analgesia can be helpful in some patients with intractable pain. Over 15 years palliative care professionals evolved their spinals policy through a repeated series of evaluations, discussions and literature reviews. One hundred intraspinal lines were then reviewed. Notable changes in policy were the switch from epidurals to intrathecals, and the insertion of lines during working hours rather than as emergencies. Our efficacy, and frequency of adverse effects, is equal or better to published studies. Key issues in reducing adverse effects were the improved care of the spinal line exit site, a change from bolus administration to continuous infusions, and modifying line insertion techniques. Current policy is to use continuous infusions of diamorphine and bupivacaine in a 1:5 ratio through externalized intrathecal lines. The lines are effective in approximately two thirds of patients and can be kept in place for up to 18 months. The policy continues to be updated and common documentation is now in place.

Streaming potential and electroosmotic flow in heterogeneous circular microchannels with nonuniform zeta potentials: requirements of flow rate and current continuities

Real surfaces are typically heterogeneous, and microchannels with heterogeneous surfaces are commonly found due to fabrication defects, material impurities, and chemical adsorption from solution. Such surface heterogeneity causes a nonuniform surface potential along the microchannel. Other than surface heterogeneity, one could also pattern the various surface potentials along the microchannels. To understand how such variations affect electrokinetic flow, we proposed a model to describe its behavior in circular microchannels with nonuniform surface potentials. Unlike other models, we considered the continuities of flow rate and electric current simultaneously. These requirements cause a nonuniform electric field distribution and pressure gradient along the channel for both pressure-driven flow (streaming potential) and electric-field-driven flow (electroosmosis). The induced nonuniform pressure and electric field influence the electrokinetic flow in terms of the velocity profile, the flow rate, and the streaming potential.

Lattice Boltzmann model of microfluidics in the presence of external forces

We present here a lattice Boltzmann model in the presence of external force fields to describe electrokinetic microfluidic phenomena and consider pressure as the only external force to drive liquid flow. Our results from a 9-bit square lattice Boltzmann model are in good agreement with recent experimental data in a pressure-driven microchannel flow that could not be fully described by electrokinetic theory. The differences between the predicted and the experimental Reynolds numbers from pressure gradients are well within 5%. Results suggest that the lattice Boltzmann model described here is an effective computational tool for predicting the more complex microfluidic systems that might be problematic using conventional methods.

Optimisation of treatment by applying programmable rate-controlled drug delivery technology

A number of programmable rate-controlled drug delivery technologies have been developed during the last two decades with the aim of regulating the rate of drug delivery, sustaining the duration of therapeutic action and/or targeting the delivery of drug to a specific tissue. As a result, several therapeutically beneficial outcomes can be achieved, such as: (i) controlled delivery of a therapeutic dose at a desirable rate of delivery; (ii) maintenance of drug concentrations within an optimal therapeutic range for prolonged duration of treatment; (iii) maximisation of efficacy-dose relationship; (iv) reduction of adverse effects; (v) minimisation of the need for frequent dose intake; and (vi) enhancement of patient compliance. The treatment of illness can thus be optimised. To gain a better understanding of how to optimise the treatment of illnesses by applying programmable rate-controlled drug delivery technologies, this article reviews the scientific concepts and technical principles behind the development of various programmable rate-controlled drug delivery systems that have been marketed or are under active development. Finally, the roles of these technologies in optimising therapeutic outcomes in nine therapeutic areas are discussed.

Oscillating laminar electrokinetic flow in infinitely extended rectangular microchannels

This paper has addressed analytically the problem of laminar flow in microchannels with rectangular cross-section subjected to a time-dependent sinusoidal pressure gradient and a sinusoidal electric field. The analytical solution has been determined based on the Debye-Hückel approximation of a low surface potential at the channel wall. We have demonstrated that Onsager's principle of reciprocity is valid for this problem. Parametric studies of streaming potential have shown the dependence of the electroviscous effect not only on the Debye length, but also on the oscillation frequency and the microchannel width. Parametric studies of electroosmosis demonstrate that the flow rate decreases due to an increase in frequency. The obtained solutions for both the streaming potential and electroosmotic flows become those for flow between two parallel plates in the limit of a large aspect ratio.

Oscillating laminar electrokinetic flow in infinitely extended circular microchannels

This article addresses the problem of oscillating laminar electrokinetic liquid flow in an infinitely extended circular microchannel. Based on the Debye-Huckel approximation for low surface potential at the channel wall, a complex variable approach is used to obtain an analytical solution for the flow. The complex counterparts of the flow rate and the current are linearly dependent on the pressure gradient and the external electric field. This property is used to show that Onsager's principle of reciprocity continues to be valid (involving the complex quantities) for the stated problem. During oscillating pressure-driven flow, the electroviscous effect for a given value of the normalized reciprocal electrical double-layer (EDL) thickness is observed to attain a maximum at a certain normalized frequency. In general, an increasing normalized frequency results in a reduction of EDL effects, leading to (i). a volumetric flow rate in the case of streaming potential approaching that predicted by the theory without EDL effects, and (ii). a reduction in the volumetric flow rate in the case of electroosmosis.

Effect of liquid slip in electrokinetic parallel-plate microchannel flow

Liquid slip at hydrophobic surfaces in microchannels has frequently been observed. We present here an analytical solution for oscillating flow in parallel-plate microchannels by combining the electrokinetic transport phenomena with Navier's slip condition. Our parametric results suggest that electrokinetic transport phenomena and liquid slip at channel walls are both important and should be considered simultaneously. Their significance depends on channel wall material, electrolyte concentration, and pH. For pressure-driven-flow, liquid slip counteracts the effect by the electrical double layer and induces a larger flow rate. A higher apparent viscosity would be predicted if slip is neglected. For electroosmotic flow, liquid slip alters the flow rate by about 20% for a thick electrical double layer. Our results provide design guidelines to precisely control time-dependent microflow in hydrophobic microfluidic microelectromechanical system devices.

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.

Withdrawal symptoms in a patient receiving intrathecal morphine via an infusion pump

We describe a case of a failed implanted, programmable, intrathecal infusion pump-and its external programmer-leading to morphine withdrawal symptoms, in a patient with failed back syndrome.

Chronic blockade of melanocortin receptors alleviates allodynia in rats with neuropathic pain

We investigated the involvement of the spinal cord melanocortin (MC) system in neuropathic pain. Because we recently demonstrated that MC receptor ligands acutely alter nociception in an animal model of neuropathic pain, in this study we tested whether chronic administration was also effective. We hypothesized that chronic blockade of the spinal MC system might decrease sensory abnormalities associated with this condition. The effects of the MC receptor antagonist SHU9119 (0.5 microg/d) and agonist MTII (0.1 microg/d) were evaluated in rats with a chronic constriction injury of the sciatic nerve. Drugs were continuously infused into the cisterna magna. Antinociceptive effects were measured with tests involving temperature (10 degrees C or 47.5 degrees C) or mechanical (von Frey) stimulation. The administration of MTII increased mechanical allodynia, whereas SHU9119 produced a profound cold and mechanical antiallodynia, altering responses to control levels. The antiallodynic effects of SHU9119 were very similar to those produced by the alpha(2)-adrenergic agonist tizanidine (50 microg/d). The effects of SHU9119 and MTII are most likely mediated through the MC4 receptor, because this is the only MC-receptor subtype present in the spinal cord. We conclude that the chronic administration of MC4-receptor antagonists might provide a promising tool in the treatment of neuropathic pain.

IMPLICATIONS

In this study we demonstrated that continuous intrathecal infusion of the melanocortin-receptor antagonist SHU9119 reduces cold and mechanical allodynia in rats with a chronic constriction injury of the sciatic nerve, a lesion producing neuropathic pain.

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.

Stability of meperidine in an implantable infusion pump using capillary gas chromatography-mass spectrometry and a deuterated internal standard

A capillary gas chromatographic-mass spectrometric (GC MS) method is described for the analysis of meperidine using 3,3,5,5-[2H4]-meperidine as an internal standard. Chromatography was performed on a (5% phenyl) methylpolysiloxane column (30 m x 0.32 mm I.D., 0.25 microm film thickness) operated at 195 degrees C; helium carrier gas-50 cm/s(-1), tR = 2.3 min. Ionization was by electron impact (EI) and detection by selected ion monitoring of the molecular ions. The method provided high response linearity (mean r = 0.9982) and precision (< 6.5% C.V.). Application of this method to a pilot study of aqueous meperidine x HCl (10 mg/ml(-1)) stability in a surgically implantable infusion pump at 37 degrees C for 90 days revealed no demonstrable drug degradation.

Does intrathecal morphine in the treatment of cancer pain induce the development of tolerance?

OBJECTIVE

This retrospective study was designed to investigate whether chronic lumbar intrathecal administration of morphine leads to the development of opioid tolerance in patients suffering from intractable cancer pain.

METHODS

Between 1978 and 1995, 159 patients with refractory cancer pain were treated with intrathecal morphine in our Multidisciplinary Pain Center. The treatment consisted of preservative-free morphine administered through an access port as a single bolus. In this series of patients (n = 159), the daily doses of intrathecal morphine were determined as a function of duration of follow-up.

RESULTS

The mean follow-up period was 95 days (range, 5-909 d), the mean starting daily dose of intrathecal morphine was 2.69 mg (range, 1-7.5 mg), and the mean terminal dose was 7.82 mg (range, 1-80 mg). The results demonstrated that only a moderate increase in daily dose of intrathecal morphine was required during the course of treatment (a two- to threefold increase for a 3-mo period). Furthermore, the dose increment was similar for patients followed up for more or less than 60 days. This increase did not result in any central opioid-related side effects, and the pain was managed satisfactorily.

CONCLUSION

The requirement for a moderate increase in intrathecal opioid doses reflects the development of tolerance but did not limit the patients' ability to obtain adequate analgesia during the course of their painful disease.

Intraspinal morphine for chronic pain: a retrospective, multicenter study

Intraspinal opioids are frequently used in the treatment of cancer and noncancer pain, but few studies have evaluated the efficacy of this technique. This multicenter, retrospective study surveyed physicians in the United States regarding their standard practices when using intraspinal opioids delivered via an implanted drug administration device. Thirty-five physicians (50.0%) responded, providing 429 usable patient forms (52.4%), which sought information about screening, outcomes, dosing, and adverse effects. Patients with malignant (32.7%) and noncancer (67.3%) pain had been treated for an average of 14.6 +/- 0.57 months (range, 8-94 months) at the time of form completion. For all patients, the mean percent relief was 61.0% +/- 1.35%. Patients with somatic pain tended to have greater relief, as measured by a global rating of pain relief, than did patients with other types of pain (Mann-Whitney test, P = 0.0003). After titration during the first 3 months, intrathecal morphine doses increased only twofold from 6.84 +/- 0.65 mg/day at 3 months to 13.19 +/- 1.76 mg/day at 24 months. Compared to those with noncancer pain, malignant pain patients had a higher average initial dose. The average dose used by cancer patients escalated quickly and then stabilized, whereas the average doses used by noncancer pain patients exhibited a more gradual, linear increase in dose. Long-term adverse drug effects were uncommon, but system malfunction, usually catheter related, occurred in 21.6% of patients. Prospective, randomized, controlled clinical studies of long-term efficacy and adverse effects are warranted.

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.

Intracerebroventricular administration of morphine for control of irreducible cancer pain

Intracerebroventricular morphine analgesic for the treatment of cancer pain was administered, using implanted access ports, in 82 patients from 1984 to January 1994. All of the patients who were selected for treatment were no longer responsive and had developed drug side effects to oral or parenteral opiates in varying doses (60-400 mg/d). The mean follow-up was 66 days (range, 12-443 d) for this series of 82 patients. The effective control of pain was achieved in nearly all of the patients, with only two failures. During the treatment, the daily morphine doses were moderately increased. The initial doses of morphine were a mean of 0.30 mg (range, 0.10-2 mg), and the final doses were a mean of 2.5 mg (range, 0.10-60 mg). The results show that the ratio of the terminal dose to the initial dose increased more rapidly for patients who had a follow-up of over 60 days. However, the increase seems to have been because of the progress of the disease rather than because of drug tolerance.

Overview of current development in patient-controlled analgesia

Over the past two decades, numerous trials have assessed the safety and efficacy of patient-controlled analgesia (PCA). Advantages over conventional parenteral narcotics reported from these trials include equivalent to superior pain relief, superior patient satisfaction, decreased sedation and anxiety, faster return to normal functional status, and reduction in nursing time and hospitalization. The majority of these trials have been conducted in the postoperative patient population. In the mid to late 1980s, interest arose in applying PCA technology to the management of cancer pain. Factors that served as an impetus for the use of PCA in cancer pain included favorable reports from the postoperative setting and the often-cited statistics regarding the magnitude of the cancer pain problem. Advances in PCA technology coupled with advances in vascular access technology that allow the placement of long-term ports and catheters to facilitate intravenous, epidural, or intrathecal administration of opioid analgesics have made the applicability of PCA in ambulatory cancer patients an attractive option. The greatest breakthrough in PCA technology came with the introduction of devices making it possible to choose between intermittent (demand bolus) and continuous administration (continuous infusion) or both intermittent and continuous modes. A comparison of these types of PCA devices is described. The limitations of the literature involving PCA therapy in cancer patients make it difficult to identify optimal patient selection criteria, PCA administration schedules, drug selection and dosing, and optimal route of administration. The current status and pertinent issues related to these topics are addressed.

Intrathecal narcotics in cancer pain--a case report

A 61 year old female patient presented with metastatic bone pain three years post mastectomy. Standard oral analgesics and epidural morphine were ineffective in achieving pain control. Her pain was eventually controlled with morphine sulphate 48 mg daily via a self administered intrathecal pump. These devices are being used with increasing frequency and this case report highlights some of the problems encountered in this patient's management.

Chronic epidural bupivacaine-opioid infusion in intractable cancer pain

This study examined the efficacy and toxicity associated with chronic epidural opioid-bupivacaine infusions. In a series of 68 patients with cancer pain refractory to epidural opioids alone, analgesia was effectively regained by infusing a opioid-bupivacaine combination. Sixty-one patients (90%) were considered treatment successes, according to conventional criteria. Median length of therapy was 60-120 days, with the longest infusion lasting 277 days. Chronic bupivacaine infusion concentrations ranged from 0.1 to 0.5% with infusion rates varying from 4 to 18 ml/h. The majority of patients experienced pain relief with little or no sympathetic or sensorimotor impairment after the first 24 h at bupivacaine concentrations of 0.125-0.25% and were managed in home or chronic care settings without the need for re-hospitalization. In patients receiving higher bupivacaine concentrations, sympathetic, sensory and motor blockade were well tolerated during chronic infusion. Sensory loss was consistently observed only at bupivacaine concentrations exceeding 0.25%, and motor impairment occurred only at concentrations exceeding 0.35%. Postural hypotension was observed in 6 patients (9%) for the first 24 h only, which supports the requirement for monitoring and fluid therapy during initiation of the bupivacaine infusion. No patient experienced CNS or systemic toxicity, despite plasma total bupivacaine concentrations as high as 10.8 micrograms/ml. Serial plasma bupivacaine levels were measured in 15 patients during chronic infusion. There was considerable inter- and intra-individual variability in plasma bupivacaine concentrations and bupivacaine clearance. We conclude that epidural opioid-bupivacaine infusion is an effective and safe technique for long-term administration of analgesics in the refractory cancer patient.

Response of intractable pain to continuous intrathecal morphine: a retrospective study

We have treated 37 patients with intractable pain (35 with cancer-related pain) by continuous intrathecal morphine infusion via implanted pump. These patients were carefully selected according to specific criteria, and each demonstrated a significant reduction in pain following a test dose of intrathecal morphine. All patients had good pain relief from intrathecal morphine infusion, even with pain located in cervical dermatomes. Systemic narcotics could be withdrawn from most patients. Significant side effects were rare and typically self-limited. Many patients required gradually increasing doses, seemingly related to disease progression. Two patients with non-malignant pain have had variable dose requirements over 28 and 44 months without clear tolerance. In these patients we observed a reduction in side effects associated with systemic opioids when continuous intrathecal opioid infusion was instituted. Intrathecal opioid administration may have fewer complications than ablative pain relief procedures. In properly selected patients, this method offers an effective alternative for pain relief.

Octreotide: a potent new non-opiate analgesic for intrathecal infusion

Somatostatin-14 has been reported to relieve severe cancer pain when given intraspinally. We have studied a stable analog, octreotide, which is suitable for long-term infusion by a drug pump. In preclinical trials in dogs, chronic intrathecal and intraventricular perfusion at 40 micrograms/h did not produce neurotoxicity. On the basis of these findings cancer patients with pain unrelieved by oral opiates were treated for periods of 13 to 91 days with intrathecal octreotide 5-20 micrograms/h. During octreotide infusion, pain scores were lower while oral opiate usage was reduced. No central or systemic side effects of intrathecal administration were seen. The pain relief occurred in patients who had previously not obtained satisfactory pain control with systemic or intrathecal opiates, which is consistent with a non-opiate spinal pathway. These preliminary findings, if confirmed, suggest that octreotide is a potent non-opiate analgesic appropriate for long-term intrathecal infusion.

Comparison of continuous subcutaneous and intravenous hydromorphone infusions for management of cancer pain

To compare the safety and efficacy of subcutaneous and intravenous infusion of opioid analgesics, a randomised, double-blind, crossover trial was carried out in inpatients. 15 patients with severe cancer pain received two 48 h infusions of hydromorphone--one subcutaneously and one intravenously in randomly allocated order. The study was made double-blind by the use of two infusion pumps throughout; during the active subcutaneous infusion the intravenous pump delivered saline and vice versa. Serial measurements of pain intensity, pain relief, mood, and sedation by means of visual analogue scales showed no clinically or statistically significant difference between the two infusion routes. Side-effects were slight, and the mean number of morphine injections for breakthrough pain did not differ significantly between the routes (4.8 [SD 4.5] for intravenous vs 5.3 [5.6] for subcutaneous). Plasma hydromorphone concentrations measured at 24 h and 48 h of infusion showed stable steady-state pharmacokinetics; the mean bioavailability from subcutaneous infusion was 78% of that with intravenous infusion. Because of the simplicity, technical advantages, and cost-effectiveness of continuous subcutaneous opioid infusion into the chest wall or trunk, intravenous opioid infusion for the management of severe cancer pain should be abandoned.

Drug delivery systems. 4. Implants in drug delivery

In comparison with many of the other drug delivery systems, implantable pumps and implants for variable rate delivery are at a crude stage of development. Although exceptions exist, the typical implantable pump consists of an electromechanically complex mechanism to regulate drug delivery from a percutaneous refillable reservoir, while power to drive the system comes from a transcutaneous energy transmission system. The potential for electrical or mechanical failure is high, and the systems are not yet sufficiently convenient or easy to use to recommend in a routine therapy. Problems with refilling of an apparently well designed implanted reservoir have been observed while, at the same time, cutaneous energy transmission systems are not well established. In most instances, the development of an elementary osmotic pump system dosage form follows a well defined path of physical-chemical formulation and clinical testing. The benefits most often provided by the dosage form are expected to be (1) increase in selectivity of drug action achieved by the system's zero-order release rate, and (2) decrease in frequency of administration. The success in achieving these values is quantifiable from the pharmacology of the drug substance and its pharmacokinetics. Osmotic and other technical approaches to producing economical, rate-controlled dosage forms will make it possible for all new pharmaecutical products to carry kinetic specification of rate as well as static specification of content. This review considers the characteristics of the ideal implantable pump, the clinical situations which require pumps, the limitations of portable pumps, and the detailed characteristics of existing implantable pumps and implants. Most of the review, however, focuses on insulin delivery because of the importance of this subject.

CT-fluoroscopy link-up (CTF): potential for special procedures

Some interventional radiological procedures call for unrestricted axial vision and monoplanar fluoroscopy at different angles. We have mounted a fluoroscopic image intensifier in front of the gantry of a CT scanner to assess whether the combination would be useful. This link-up has been tested in a variety of situations and, even with the shortcomings of makeshift equipment, the combination filled some gaps in our vision of what is going on inside the patient, especially before an invasive procedure. It also proved useful in the planning of multiple procedures in a single session, especially when they had to be performed under general anesthesia in children or in the management of critical cases. We feel that the possibilities afforded by CTF (computed tomography plus fluoroscopy) need further exploration prior to the construction of purpose-built equipment. The interim information supplied suggests that it will be worth developing.

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.

Implantable drug delivery systems: practical considerations

Spinal opioids have dramatically changed the way acute, obstetrical and pain of malignant origin is managed. The development of various implantable narcotic delivery systems has complemented and facilitated the growth of this treatment modality. By interfacing appropriate patient selection with the unique advantages and disadvantages of each of the six types of implantable narcotic delivery systems, improved results both in terms of pain relief and patient satisfaction can be achieved.

Subarachnoid buprenorphine administered by implantable micropumps

This report concerns 23 patients, the majority of whom are suffering from low back and chest pain caused by chest, urological or gynaecological cancer. These patients were treated with subarachnoid buprenorphine, administered in a single bolus or by slow infusion from micropumps, at a daily dose adapted to patients need (0.06-0.15 mg). The painful symptomatology was successfully controlled in all the cases treated, allowing the patients to live a virtually normal life. In no cases was respiratory depression or tolerance observed.