Polyanalgesic Consensus Conference--2012: recommendations to reduce morbidity and mortality in intrathecal drug delivery in the treatment of chronic pain

Programmable intrathecal pumps for the management of chronic pain: recommendations for improved efficiency

The management of chronic pain can be very challenging. Often, physicians employ intrathecal (IT) drug delivery systems as a last resort to relieve intractable pain. The system consists of an implantable pump that stores and delivers medication through a catheter to the IT space. Programmability is achieved by positioning an external devise over the implanted pump to change the mode of drug delivery. The innovations in programmable IT drug delivery systems are expanding more rapidly than ever before. Unfortunately, the rapid expansion is accompanied by a lack of prospective randomized trials examining these new options. In an effort to improve results and reduce side effects, publications by experts or expert consensus panels provide guidance for the community. The purpose of this article is to provide a summary of high interest topics in recent publications.

The Accuracy of Template-Guided Refill Technique of Intrathecal Pumps Controlled by Fluoroscopy: An Observational Study

OBJECTIVES

Intrathecal drug therapy is being utilized increasingly for the treatment of chronic refractory pain. However, performing the regular pump refill procedures caries the potential risk of medication injection into the subcutaneous tissue. The aim of this study was to assess the accuracy of this template-guided refill technique by means of fluoroscopic evaluation.

MATERIALS AND METHODS

In 23 patients, the difference between the identification of the reservoir fill port center using the manufacturer's template and fluoroscopic guidance was assessed on four consecutive refill procedures by a two physicians. A distance surpassing that between the center and the margin of the port (3.5 mm) was considered a clinically relevant deviation. Analyses were performed with a one-sample t-test, with p < 0.05 indicating statistical significance.

RESULTS

The mean difference distance between identification markings of the target with fluoroscopic guidance and with the template was 8.2 mm, with limited variance (2.7 mm). For all individual refill procedures, the port center identification accuracy differed significantly from zero (all p < 0.001) and from the clinically relevant cut-off point of 3.5 mm (all p < 0.001). Only seven attempts (6.4%) were within the margins of the fill port.

CONCLUSIONS

Our results suggest poor accuracy of insertion point identification using the template. This highlights the potential risk of errors related to identification of the puncture site using the template-guided technique.

Intrathecal delivery of analgesics

Targeted intrathecal (IT) drug delivery systems (IDDS) are an option in algorithms for the treatment of patients with moderate to severe chronic refractory pain when more conservative options fail. This therapy is well established and supported by several publications. It has shown efficacy and is an important tool for the treatment of spasticity, and both cancer and nonmalignant pain. Recent technological advances, new therapeutic applications, reported complications, and the costs as well as maintenance required for this therapy require the need to stay up-to-date about new recommendations that may improve outcomes. This chapter reviews all technological issues regarding IDDS implantation with follow-up, and pharmacological recommendations published during recent years that provide evidence-based decision making process in the management of chronic pain and spasticity in patients.

"Sonology" of programmable intrathecal pumps

OBJECTIVE

The study aims to demonstrate the unique sonographic features of the commercially available intrathecal drug delivery systems.

METHODS

"Not-for-human-use" pumps were obtained, placed in a tray, and covered with an ultrasound phantom gel. The anterior surface of each pump was scanned and the sonographic features were observed and recorded.

RESULTS

All systems have a centrally located reservoir port (RP) and a peripherally located catheter access port (CAP) that are observable on ultrasound. The RP of the SynchroMed II system (Medtronic, Minneapolis, MN, USA) appears as an anechoic depression and a break in the bright echogenic line of the superior pump surface. The CAP appears as smaller diameter conical depression outside the circular perimeter of the pump. The RP of the MedStream system (Codman & Shurtleff, Inc., Raynham, MA, USA) has a dome-shaped appearance. The CAP appears as a smaller dome-shaped object that is off center but still contained within the circular perimeter of the pump. Similarly, the RP of the Prometra system (Flowonix Medical Inc, Mt. Olive, NJ, USA) is a dome-shaped object. The CAP visually appears similar to the reservoir access port of the SynchroMed II system, namely a small depression and a break in the bright echogenic line of the pump surface, outside the perimeter of the pump.

CONCLUSION

In all programmable intrathecal pumps, the RP can be readily identified sonographically. Potentially, the dome-shaped configuration of RP for the Prometra and MedStream systems make the access easier, when compared with SynchroMed II system. Ultrasound could potentially be utilized to localize the RP and CAP for all the systems as each of the three systems has a unique sonographic appearance.

Ziconotide

Questions from patients about pain conditions and analgesic pharmacotherapy and responses from authors are presented to help educate patients and make them more effective self-advocates. The topics addressed in this issue are ziconotide, a novel approach to pain management that is derived from a snail toxin, its uses and possible side effects.

Role of Catheter's Position for Final Results in Intrathecal Drug Delivery. Analysis Based on CSF Dynamics and Specific Drugs Profiles

Intrathecal drug delivery is an effective and safe option for the treatment of chronic pathology refractory to conventional pain therapies. Typical intrathecal administered drugs are opioids, baclofen, local anesthetics and adjuvant medications. Although knowledge about mechanisms of action of intrathecal drugs are every day more clear many doubt remain respect the correct location of intrathecal catheter in order to achieve the best therapeutic result. We analyze the factors that can affect drug distribution within the cerebrospinal fluid. Three categories of variables were identified: drug features, cerebrospinal fluid (CSF) dynamics and patients features. First category includes physicochemical properties and pharmacological features of intrathecal administered drugs with special attention to drug lipophilicity. In the second category, the variables in CSF flow, are considered that can modify the drug distribution within the CSF with special attention to the new theories of liquoral circulation. Last category try to explain inter-individual difference in baclofen response with difference that are specific for each patients such as the anatomical area to treat, patient posture or reaction to inflammatory stimulus. We conclude that a comprehensive evaluation of the patients, including imaging techniques to study the anatomy and physiology of intrathecal environment and CSF dynamics, could become essential in the future to the purpose of optimize the clinical outcome of intrathecal therapy.

Randomised, double-blind controlled trial by dose reduction of implanted intrathecal morphine delivery in chronic non-cancer pain

OBJECTIVE

This study aimed to investigate the efficacy of intrathecal morphine in the long term by hypothesising that a reduction of the intrathecal opioid dose following long-term administration would increase the level of pain intensity.

DESIGN

Randomised, double-blind, controlled, parallel group trial.

SETTING

Department of Pain Management, Russells Hall Hospital, Dudley, UK.

PARTICIPANTS

24 patients with non-cancer pain implanted with morphine reservoirs were assessed for eligibility.

INTERVENTIONS

Participants were randomly allocated to one of two parallel groups in which one of the groups had no change in morphine dose and the other group had a small reduction (20%) in dosage every week during a 10-week follow-up.

OUTCOME

Primary outcomes were visual analogue scale (VAS) pain score change and withdrawal from the study due to lack of efficacy.

RESULTS

9 of the patients assessed for eligibility declined to participate in the study. 15 patients were randomised to control (n=5) or intervention (n=10) and included in an intention-to-treat analysis. Owing to worsening of pain, seven patients withdrew from the study prematurely. None knew prior to withdrawal which arm of the study they were in, but all turned out to be in the dose-reduction arm. The calculation of dropout rates between groups indicated a significant statistical difference (p=0.026) and recruitment was ceased. The VAS change between baseline and the last observation was smaller in the control group (median, Mdn=11) than in the intervention group (Mdn=30.5), although not statistically significant, Z=-1.839, p=0.070; r=-0.47. Within groups, VAS was significantly lower at baseline (Mdn=49.5) than at the last observation (Mdn=77.5) for the reduction group, Z=-2.805, p=0.002; r=-0.627 but not for the control group (p=0.188).

CONCLUSIONS

This double-blind randomised controlled trial of chronic intrathecal morphine administration suggests the effectiveness of this therapy for the management of chronic non-cancer pain. However, owing to the small number of patients completing the study (n=8), further studies are warranted.

TRIAL REGISTRATION

International Standard Randomised Controlled Trials Centre (ISRCTN 33733462).