ECAP-controlled closed-loop versus open-loop SCS for the treatment of chronic pain: 36-month results of the EVOKE blinded randomized clinical trial

INTRODUCTION

The evidence for spinal cord stimulation (SCS) has been criticized for the absence of blinded, parallel randomized controlled trials (RCTs) and limited evaluations of the long-term effects of SCS in RCTs. The aim of this study was to determine whether evoked compound action potential (ECAP)-controlled, closed-loop SCS (CL-SCS) is associated with better outcomes when compared with fixed-output, open-loop SCS (OL-SCS) 36 months following implant.

METHODS

The EVOKE study was a multicenter, participant-blinded, investigator-blinded, and outcome assessor-blinded, randomized, controlled, parallel-arm clinical trial that compared ECAP-controlled CL-SCS with fixed-output OL-SCS. Participants with chronic, intractable back and leg pain refractory to conservative therapy were enrolled between January 2017 and February 2018, with follow-up through 36 months. The primary outcome was a reduction of at least 50% in overall back and leg pain. Holistic treatment response, a composite outcome including pain intensity, physical and emotional functioning, sleep, and health-related quality of life, and objective neural activation was also assessed.

RESULTS

At 36 months, more CL-SCS than OL-SCS participants reported ≥50% reduction (CL-SCS=77.6%, OL-SCS=49.3%; difference: 28.4%, 95% CI 12.8% to 43.9%, p<0.001) and ≥80% reduction (CL-SCS=49.3%, OL-SCS=31.3%; difference: 17.9, 95% CI 1.6% to 34.2%, p=0.032) in overall back and leg pain intensity. Clinically meaningful improvements from baseline were observed at 36 months in both CL-SCS and OL-SCS groups in all other patient-reported outcomes with greater levels of improvement with CL-SCS. A greater proportion of patients with CL-SCS were holistic treatment responders at 36-month follow-up (44.8% vs 28.4%), with a greater cumulative responder score for CL-SCS patients. Greater neural activation and accuracy were observed with CL-SCS. There were no differences between CL-SCS and OL-SCS groups in adverse events. No explants due to loss of efficacy were observed in the CL-SCS group.

CONCLUSION

This long-term evaluation with objective measurement of SCS therapy demonstrated that ECAP-controlled CL-SCS resulted in sustained, durable pain relief and superior holistic treatment response through 36 months. Greater neural activation and increased accuracy of therapy delivery were observed with ECAP-controlled CL-SCS than OL-SCS.

TRIAL REGISTRATION NUMBER

NCT02924129.

Neurophysiological outcomes that sustained clinically significant improvements over 3 years of physiologic ECAP-controlled closed-loop spinal cord stimulation for the treatment of chronic pain

INTRODUCTION

A novel, spinal cord stimulation (SCS) system with a physiologic closed-loop (CL) feedback mechanism controlled by evoked compound action potentials (ECAPs) enables the optimization of physiologic neural dose and the accuracy of the stimulation, not possible with any other commercially available SCS systems. The report of objective spinal cord measurements is essential to increase the transparency and reproducibility of SCS therapy. Here, we report a cohort of the EVOKE double-blind randomized controlled trial treated with CL-SCS for 36 months to evaluate the ECAP dose and accuracy that sustained the durability of clinical improvements.

METHODS

41 patients randomized to CL-SCS remained in their treatment allocation and were followed up through 36 months. Objective neurophysiological data, including measures of spinal cord activation, were analyzed. Pain relief was assessed by determining the proportion of patients with ≥50% and ≥80% reduction in overall back and leg pain.

RESULTS

The performance of the feedback loop resulted in high-dose accuracy by keeping the elicited ECAP within 4µV of the target ECAP set on the system across all timepoints. Percent time stimulating above the ECAP threshold was >98%, and the ECAP dose was ≥19.3µV. Most patients obtained ≥50% reduction (83%) and ≥80% reduction (59%) in overall back and leg pain with a sustained response observed in the rates between 3-month and 36-month follow-up (p=0.083 and p=0.405, respectively).

CONCLUSION

The results suggest that a physiological adherence to supra-ECAP threshold therapy that generates pain inhibition provided by ECAP-controlled CL-SCS leads to durable improvements in pain intensity with no evidence of loss of therapeutic effect through 36-month follow-up.

Durability of Clinical and Quality-of-Life Outcomes of Closed-Loop Spinal Cord Stimulation for Chronic Back and Leg Pain: A Secondary Analysis of the Evoke Randomized Clinical Trial

Importance

Chronic pain is debilitating and profoundly affects health-related quality of life. Spinal cord stimulation (SCS) is a well-established therapy for chronic pain; however, SCS has been limited by the inability to directly measure the elicited neural response, precluding confirmation of neural activation and continuous therapy. A novel SCS system measures the evoked compound action potentials (ECAPs) to produce a real-time physiological closed-loop control system.

Objective

To determine whether ECAP-controlled, closed-loop SCS is associated with better outcomes compared with fixed-output, open-loop SCS at 24 months following implant.

Design, Setting, and Participants

The Evoke study was a double-blind, randomized, controlled, parallel arm clinical trial with 36 months of follow-up. Participants were enrolled from February 2017 to 2018, and the study was conducted at 13 US investigation sites. SCS candidates with chronic, intractable back and leg pain refractory to conservative therapy, who consented, were screened. Key eligibility criteria included overall, back, and leg pain visual analog scale score of 60 mm or more; Oswestry Disability Index score of 41 to 80; stable pain medications; and no previous SCS. Analysis took place from October 2020 to April 2021.

Interventions

ECAP-controlled, closed-loop SCS was compared with fixed-output, open-loop SCS.

Main Outcomes and Measures

Reported here are the 24-month outcomes of the trial, which include all randomized patients in the primary and safety analyses. The primary outcome was a reduction of 50% or more in overall back and leg pain assessed at 3 and 12 months (previously published).

Results

Of 134 randomized patients, 65 (48.5%) were female and the mean (SD) age was 55.2 (10.6) years. At 24 months, significantly more closed-loop than open-loop patients were responders (≥50% reduction) in overall pain (53 of 67 [79.1%] in the closed-loop group; 36 of 67 [53.7%] in the open-loop group; difference, 25.4% [95% CI, 10.0%-40.8%]; P = .001). There was no difference in safety profiles between groups (difference in rate of study-related adverse events: 6.0 [95% CI, -7.8 to 19.7]). Improvements were also observed in health-related quality of life, physical and emotional functioning, and sleep, in parallel with opioid reduction or elimination. Objective neurophysiological measurements substantiated the clinical outcomes and provided evidence of activation of inhibitory pain mechanisms.

Conclusions and Relevance

ECAP-controlled, closed-loop SCS, which elicited a more consistent neural response, was associated with sustained superior pain relief at 24 months, consistent with the 3- and 12-month outcomes.

Ten kilohertz SCS for Treatment of Chronic Upper Extremity Pain (UEP): Results from Prospective Observational Study

Background

Chronic upper extremity pain (UEP) has complex etiologies and is often disabling. It has been shown that 10 kHz SCS can provide paresthesia-free and durable pain relief in multiple pain types and improve the quality of life of patients.

Objective

To gain additional evidence on the safety and effectiveness of 10 kHz SCS for the treatment of chronic UEP.

Study Design

It was a prospective, multicenter, and observational study. The study was registered on ClinicalTrials.gov prospectively (clinical trial identifier: NCT02703818).

Setting

Multicenter.

Patients Intervention and Main Outcomes

A total of 43 subjects with chronic UEP of ≥5 cm (on a 0-10 cm visual analog scale; VAS) underwent a trial of 10 kHz SCS, and subjects with ≥40% pain relief received a permanent implant. All subjects had upper limb pain at baseline, while some had concomitant shoulder or neck pain. Subject outcomes were assessed for 12 months, and the primary outcome was the responder rate (percentage of subjects experiencing ≥50% pain relief from baseline) at three months.

Results

Thirty-eight subjects successfully completed the trial (88.3% success rate), 33 received permanent implants (five withdrew consent), and 32 had device activation (per protocol population). There were no paresthesias or uncomfortable changes in stimulation related to changes in posture during the study and there were no neurological deficits. Responder rates at 12 months for upper limb, shoulder, and neck pain in per protocol population (N=32) were 78.1%, 85.2%, and 75.0%, respectively. At 12 months, 84.4% of subjects were satisfied or very satisfied with 10 kHz SCS, and 38.7% either reduced or eliminated opioid usage.

Conclusion

This study further supports the effectiveness of 10 kHz SCS for chronic UEP treatment and documents the safety profile of the therapy.

Clinical Trial Identifier

NCT02703818.

Long-term safety and efficacy of closed-loop spinal cord stimulation to treat chronic back and leg pain (Evoke): a double-blind, randomised, controlled trial

BACKGROUND

Spinal cord stimulation has been an established treatment for chronic back and leg pain for more than 50 years; however, outcomes are variable and unpredictable, and objective evidence of the mechanism of action is needed. A novel spinal cord stimulation system provides the first in vivo, real-time, continuous objective measure of spinal cord activation in response to therapy via recorded evoked compound action potentials (ECAPs) in patients during daily use. These ECAPs are also used to optimise programming and deliver closed-loop spinal cord stimulation by adjusting the stimulation current to maintain activation within patients' therapeutic window. We aimed to examine pain relief and the extent of spinal cord activation with ECAP-controlled closed-loop versus fixed-output, open-loop spinal cord stimulation for the treatment of chronic back and leg pain.

METHODS

This multicentre, double-blind, parallel-arm, randomised controlled trial was done at 13 specialist clinics, academic centres, and hospitals in the USA. Patients with chronic, intractable pain of the back and legs (Visual Analog Scale [VAS] pain score ≥60 mm; Oswestry Disability Index [ODI] score 41-80) who were refractory to conservative therapy, on stable pain medications, had no previous experience with spinal cord stimulation, and were appropriate candidates for a spinal cord stimulation trial were screened. Eligible patients were randomly assigned (1:1) to receive ECAP-controlled closed-loop spinal cord stimulation (investigational group) or fixed-output, open-loop spinal cord stimulation (control group). The randomisation sequence was computer generated with permuted blocks of size 4 and 6 and stratified by site. Patients, investigators, and site staff were masked to the treatment assignment. The primary outcome was the proportion of patients with a reduction of 50% or more in overall back and leg pain with no increase in pain medications. Non-inferiority (δ=10%) followed by superiority were tested in the intention-to-treat population at 3 months (primary analysis) and 12 months (additional prespecified analysis) after the permanent implant. This study is registered with ClinicalTrials.gov, NCT02924129, and is ongoing.

FINDINGS

Between Feb 21, 2017, and Feb 20, 2018, 134 patients were enrolled and randomly assigned (67 to each treatment group). The intention-to-treat analysis comprised 125 patients at 3 months (62 in the closed-loop group and 63 in the open-loop group) and 118 patients at 12 months (59 in the closed-loop group and 59 in the open-loop group). The primary outcome was achieved in a greater proportion of patients in the closed-loop group than in the open-loop group at 3 months (51 [82·3%] of 62 patients vs 38 [60·3%] of 63 patients; difference 21·9%, 95% CI 6·6-37·3; p=0·0052) and at 12 months (49 [83·1%] of 59 patients vs 36 [61·0%] of 59 patients; difference 22·0%, 6·3-37·7; p=0·0060). We observed no differences in safety profiles between the two groups. The most frequently reported study-related adverse events in both groups were lead migration (nine [7%] patients), implantable pulse generator pocket pain (five [4%]), and muscle spasm or cramp (three [2%]).

INTERPRETATION

ECAP-controlled closed-loop stimulation provided significantly greater and more clinically meaningful pain relief up to 12 months than open-loop spinal cord stimulation. Greater spinal cord activation seen in the closed-loop group suggests a mechanistic explanation for the superior results, which aligns with the putative mechanism of action for spinal cord stimulation and warrants further investigation.

FUNDING

Saluda Medical.

Multicenter, Randomized, Double-Blind Study Protocol Using Human Spinal Cord Recording Comparing Safety, Efficacy, and Neurophysiological Responses Between Patients Being Treated With Evoked Compound Action Potential-Controlled Closed-Loop Spinal Cord Stimulation or Open-Loop Spinal Cord Stimulation (the Evoke Study)

BACKGROUND

The spinal cord (SC) response to stimulation has yet to be studied in a pivotal clinical study. We report the study design of an ongoing multicenter, randomized, double-blind, controlled, parallel-arm study of an evoked compound action potential (ECAP) controlled closed-loop spinal cord stimulation (SCS) system, which aims to gain U.S. Food and Drug Administration approval.

METHODS

This study will enroll 134 SCS candidates with chronic trunk and limb pain from up to 20 United States sites. Subjects are randomized 1:1 to receive ECAP-controlled closed-loop or open-loop, conventional SCS. The primary objective is noninferiority of closed-loop stimulation determined by the proportion of subjects with ≥50% reduction in overall trunk and limb pain and no increase in pain medications at the three-month visit. If noninferiority is met, superiority is tested. In addition, measures recommended by IMMPACT (e.g., pain intensity, functional disability, emotional functioning, quality of life, impression of change, and sleep), neurophysiological properties (e.g., SC activation, conduction velocity, chronaxie, and rheobase), and safety are analyzed.

DISCUSSION

All approved SCS therapies, regardless of the presence or absence of stimulation induced paresthesias, produce fixed-output stimuli; that is, the energy delivered from the electrode array has a defined output irrespective of the neural response of SC fibers. An SCS system has been developed that directly measures the neurophysiologic activation of the SC to stimulation (i.e., ECAP amplitude) and uses this information in a feedback mechanism to produce closed-loop SCS to maintain optimal and stable activation of the SC. This study represents the first randomized, double-blind, pivotal study in the field of neuromodulation to measure SC activation in ECAP-controlled closed-loop versus open-loop stimulation and is expected to yield important information regarding differences in safety, efficacy, and neurophysiological properties. The potential clinical utility of these objective measurements of SC activation and other neurophysiological properties promises to improve outcomes of SCS for chronic pain patients.

Quantum gravity and taoist cosmology: Exploring the ancient origins of phenomenological string theory

This paper carries forward the author's contribution to PBMP's previous special issue on Integral Biomathics (Rosen 2015). In the earlier paper, the crisis in contemporary theoretical physics was described and it was demonstrated that the problem can be addressed effectively only by shifting the foundations of physics from objectivist Cartesian philosophy to phenomenological philosophy. To that end, a phenomenological string theory was proposed based on qualitative topology and hypercomplex numbers. The current presentation takes this further by delving into the ancient Chinese origin of phenomenological string theory. First, we discover a deep connection between the Klein bottle, which is crucial to the theory, and the Ho-t'u, an old Chinese number archetype central to Taoist cosmology. The two structures are seen to mirror each other in expressing the curious psychophysical (phenomenological) action pattern at the heart of microphysics. But tackling the question of quantum gravity requires that a whole family of topological dimensions be brought into play. What we find in engaging with these structures is a closely related family of Taoist forebears that, in concert with their successors, provide a blueprint for cosmic evolution. Whereas conventional string theory accounts for the generation of nature's fundamental forces via a notion of symmetry breaking that is essentially static and thus unable to explain cosmogony successfully, phenomenological/Taoist string theory is guided by the dialectical interplay between symmetry and asymmetry inherent in the principle of synsymmetry. This dynamic concept of cosmic change is elaborated on in the three concluding sections of the paper. Here, a detailed analysis of cosmogony is offered, first in terms of the theory of dimensional development and its Taoist (yin-yang) counterpart, then in terms of the evolution of the elemental force particles through cycles of expansion and contraction in a spiraling universe. The paper closes by considering the role of the analyst per se in the further evolution of the cosmos.

The Polyanalgesic Consensus Conference (PACC): Recommendations for Trialing of Intrathecal Drug Delivery Infusion Therapy

INTRODUCTION

Intrathecal (IT) drug infusion is an appropriate and necessary tool in the algorithm to treat refractory cancer and noncancer pain. The decision-making steps/methodology for selecting appropriate patients for implanted targeted drug delivery systems is controversial and complicated. Therefore, a consensus on best practices for determining appropriate use of IT drug infusion may involve testing/trialing this therapy before implantation.

METHODS

This current Polyanalgesic Consensus Conference (PACC) update was designed to address the deficiencies and emerging innovations since the previous PACC convened in 2012. A literature search identified publications available since the previous PACC publications in 2014, and relevant sources were contributed by the PACC members. After reviewing the literature, the panel determined the evidence levels and degrees of recommendations. The developed consensus was ranked as strong (>80%), moderate (50-79%), or weak (<49%).

RESULTS

The trialing for IT drug delivery systems (IDDS) remains an area of continued controversy. The PACC recommendations for trialing are presented in 34 consensus points and cover trialing for morphine, ziconotide, and medication admixtures; starting doses and titration practices; measurements of success; trial settings and monitoring; management of systemic opioids during trialing; and the role of psychological evaluation. Finally, the PACC describes clinical scenarios in which IT trialing is required or not required.

CONCLUSION

The PACC provides consensus guidance on best practices of trialing for IDDS implants. In addition, the PACC recommends that no trial may be required in certain patient populations.

Editorial

Preparing this ambitious Special Issue has challenged everyone involved: authors, reviewers, and guest editors. The editors solicited contributions from many leading figures in a broad array of scientific and philosophical disciplines, with emphasis on phenomenological approaches to philosophy (see Section I). The motivating force was the conviction that if we could find a viable bridge for the gap between the "two cultures"(1) of science and philosophy, fundamental problems in each camp could be addressed more fruitfully than ever before and a new kind of science be born. We believe the unprecedented cross-fertilization of ideas from this initiative may furnish seeds from which that new, better integrated, and more effective approach to science may arise. This Special Issue consists of forty papers. For each one, multiple reviewers were solicited, with at least one reviewer from each "culture" (a scientist and a philosopher). In many cases, several rounds of revision were carried out. Needless to say, this required great patience and dedication of all participants. The editors gratefully acknowledge the contributions of our authors, and of our anonymous reviewers, who worked long and hard on the papers we sent them with no compensation for their efforts. We also wish to thank the Elsevier editorial and production team for the support they gave us in bringing this project to fruition. We would now like to offer a synoptic overview of the Special Issue, proceeding section by section and paper by paper. Our hope is that the reader will find this unique effort to marry science and philosophy both meaningful and enjoyable.

Increased pain catastrophizing associated with lower pain relief during spinal cord stimulation: results from a large post-market study

BACKGROUND

Pain catastrophizing is a negative cognitive distortion to actual or anticipated pain. Our aim was to determine if greater catastrophizing has a deleterious relationship with pain intensity and efficacy outcomes in patients receiving SCS.

METHODS

As part of an ongoing Institutional Review Board-approved, multi-site, single arm post-market study, 386 patients were implanted with an Eon Mini™ SCS system and had follow-up visits at 3, 6, and 12 months post-implant. Outcomes collected during the study included, but were not limited to pain intensity using the numeric rating scale (NRS), patient reported pain relief (PRP), satisfaction with their SCS system, quality of life (QOL), pain catastrophizing scale (PCS) and state-trait anxiety index (STAI).

RESULTS

NRS scores were associated with higher PCS scores at six months (r = 0.50, p < 0.001). The PCS was a strong predictor of the NRS when controlled for known confounders. Patients with PCS ≥30 at 6-months post-implant had a lower six-month PRP (p < 0.001) and were five times more likely to report dissatisfaction with their SCS device (p < 0.001, OR = 5.46, 95% CI: 2.51-6.35). Additionally, at six months, those who were clinically catastrophizing were three times more likely to report deterioration in QOL (p < 0.002, OR = 3.12, 95% CI: 1.62-5.51). These findings were similar at the 12 months follow visit.

CONCLUSIONS

Our results indicate that patients with greater catastrophizing, post-implant, were more likely to report higher pain intensity and lower pain relief, quality of life and satisfaction with SCS. These results indicate that associations between pain intensity and pain-related mental health may contribute to influence the overall efficacy of SCS.

The Effects of Angiotensin II on Renal Water and Electrolyte Excretion in Normal and Caval Dogs

The effects of intravenous administration of angiotensin II on renal water and electrolyte excretion were examined during hydropenia, water diuresis, and hypotonic saline diuresis in anesthetized normal dogs and dogs with thoracic inferior vena cava constriction and ascites (caval dogs). The effects of unilateral renal artery infusion of a subpressor dose were also examined.During hydropenia angiotensin produced a decrease in tubular sodium reabsorption, with a considerably greater natriuresis in caval dogs, and associated with a decrease in free water reabsorption (T(c) (H(2)O)). Water and hypotonic saline diuresis resulted in an augmented angiotensin natriuresis, with a greater effect still observed in caval dogs. In these experiments free water excretion (C(H(2)O)) was limited to 8-10% of the glomerular filtration rate (GFR), although distal sodium load increased in every instance. In the renal artery infusion experiments a significant ipsilateral decrease in tubular sodium reabsorption was induced, particularly in caval dogs.These findings indicate that angiotensin has a direct effect on renal sodium reabsorption unrelated to a systemic circulatory alteration. The attenuation or prevention of the falls in GFR and effective renal plasma flow (ERPF) usually induced by angiotensin may partially account for the greater natriuretic response in caval dogs and the augmentation during water or hypotonic saline diuresis. However, a correlation between renal hemodynamics and the degree of natriuresis induced was not always present and, furthermore, GFR and ERPF decreased significantly during the intrarenal artery infusion experiments. Therefore, the present experiments indicate that another mechanism is operative in the control of the angiotensin natriuresis and suggest that alterations in intrarenal hemodynamics may play a role.The decrease in T(c) (H(2)O) and the apparent limitation of C(H(2)O) associated with an increase in distal sodium load localize the site of action of angiotensin to the ascending limb of Henle's loop and the proximal tubule.

Development of a microparticle-based on-site immunoassay for the detection of atrazine in soil and water samples

Atrazine is widely used as a herbicide in agriculture and has been identified as a major groundwater contaminant in the US. Because of the possible hazard associated with its usage, there is a need for an efficient and economic screening method for on-site field testing of atrazine and other s-triazine herbicides in soil and water. We have developed a rapid, on-site test for the detection of atrazine based on the principle of microparticle agglutination inhibition immunoassay. The test detects 50 microg kg(-1) (0.050 ppm) atrazine in soil samples with direct extraction and 1.0 microg L(-1) atrazine in water samples when coupled with solid phase extraction.

Preparation of pentachlorophenol derivatives and development of a microparticle-based on-site immunoassay for the detection of PCP in soil samples

Pentachlorophenol (PCP) is used as a herbicide in agriculture and as an insecticide for termite control. Because of the apparent hazard associated with its usage, there is a need for an efficient and economic on-site screening method. A 5-min on-site test has been developed for the detection of PCP based on the OnTrak format, a successful Roche on-site test format for drugs of abuse, utilizing the principle of latex agglutination immunoassay. The test detects 1 ppm of PCP in soil samples.

Chronic post thoracotomy pain

Chronic post-thoracotomy pain (CPP) is a vexing clinical problem whose management has received scant attention. In order to identify the risk factors associated with CPP and determine the optimal treatment, the records of 238 consecutive patients who underwent thoracotomy were reviewed. CPP was defined as discomfort requiring the regular administration of analgesics that continued more than three months following surgery. CPP was present in 25 (11%) patients: 10/20 (50%) chest wall resections, 5/25 (20%) pleurectomies, 10/193 (5%) pulmonary resections. Among the 23 patients who required preoperative narcotics, 12 (52%) developed CPP. Improved pain control and decreased narcotic use was achieved via the administration of nonsteroidal anti-inflammatory medication and tricyclic anti-depressants. In addition, 10/25 patients required 11 pain procedures: trigger-point injection, intercostal blocks, injections of epidural steroids, stellate ganglion block. Recurrent pain occurred in 20 patients following initial control. All were found to have tumor regrowth. We conclude that CPP occurs more commonly following chest-wall resection and pleurectomy, and that preoperative narcotic use is a predictor of CPP. Worsening pain following initial relief should prompt a vigorous search for recurrent cancer.

Supportive care in oncology

Pain management, nutritional support, and psychosocial support are fundamental services that enhance patients' ability to cope with their cancer and its therapy. The common goal of symptom prevention mandates that each of these supportive services be provided to all patients throughout their cancer experience. Comprehensive cancer pain management begins with identifying the origin of all of the patient's pains and treating each one specifically. Pain prevention can be achieved through around-the-clock opioid administration with as-needed supplements for breakthrough pain and dose titration. Common narcotic side effects such as constipation and nausea also must be prevented. Successful opioid analgesia requires that patient and family concerns regarding addiction and tolerance be dispelled at the outset. Cancer pain prevention can be further optimized with the use of appropriate coanalgesics in response to the pathophysiology of the patient's pains. Cognitive and behavioral therapies may also be useful adjuncts to reduce both pain and suffering. Procedure-oriented pain control should be considered when systemic pharmacologic therapy does not provide adequate pain relief or is associated with intolerable side effects. The only absolute contraindications for pain-relieving procedures are untreatable coagulopathy and a decrease in mental status not related to medical pain management. Useful neurodestructive techniques include radiofrequency lesioning, cryoanalgesia, and chemical neurolysis with agents such as phenol, alcohol, and hypertonic saline. The most beneficial pain-relieving procedures and percutaneous cordotomy, spinal narcotics, celiac and hypogastric plexus ablation, spinal neurolysis, and epidural injection of steroids and hypertonic saline. Procedure selection depends on the cause of the pain and the patient's prognosis. Common indications for pain-relieving procedures include unilateral pain below the shoulder, upper abdominal visceral pains, pelvic visceral pain, perineal pain, vertebral body metastasis, discogenic pain, and spinal stenosis. As results of well-conducted scientific trials begin to appear in the literature, the indications for these procedures will be better understood, resulting in their more appropriate use. Principles of nutritional support in patients with cancer include an awareness of the problem of malnutrition and its impact on performance status, quality of life, prognosis, and treatment; identification of those patients at risk; prophylactic versus therapeutic intervention; and analysis and management of the specific impediment(s) to adequate nutrient intake and absorption. The primary goals for nutritional support in cancer patients are prevention of weight loss and maintenance of adequate protein status. Appreciation of practical issues of nutritional support will enable the practicing physician to achieve these goals using primarily oral nutrition options.(ABSTRACT TRUNCATED AT 400 WORDS)

Transdermal fentanyl: seeding trial in patients with chronic cancer pain

In this study, 6 patients with pain from advanced cancer were enrolled in a multicenter, open-label seeding trial of transdermal fentanyl. Following equianalgesic dose conversion, transdermal fentanyl patches were applied every 3 days. Mean fentanyl dosage doubled by week 2 and tripled by week 4. Pain control improved in all patients. There were no significant changes in mood, constipation, nausea, sedation, daily activities, or interpersonal relationships from pretrial to posttrial analyses. Following the study period, 5 patients were monitored for a mean total of 55 days with a mean final fentanyl dose of 240 micrograms/hr. As part of a comprehensive cancer pain management program, transdermal fentanyl appears to be safe and effective, and should prove to be a useful addition to currently available opioid analgesics.

Degree of heterogeneity of binding specificities of antibodies to the phenylarsonate group that share a common idiotype

We have investigated the microheterogeneity of hybridoma products (HP) expressing the major idiotype (CRIA) associated with A/J antibodies to the p-azophenylarsonate (Ar) hapten group. The properties investigated were affinity for a phenylarsonate derivative and the fine specificity of the combining sites of the various HP. The fine specificity was approached by measuring relative affinities for a series of related haptens. It was found that, although variations exist, there are strong similarities in affinities and fine specificities of the antigen-binding sites of CRI+A HP. The range of affinities for (p-azobenzenearsonic acid)-N-3H-acetyl-L-tyrosine was 0.41 x 10(6)-2.2 x 10(6) M-1. In all cases the addition of a second ring structure (benzene or histidine) and an azo group greatly increased the binding affinity. Some differences in fine specificity among the HP were seen with respect to affinities for o-arsanilate or the arsanilate derivative of histidine. However, the two HP which are the strongest inhibitors in the conventional assay for CRIA were virtually identical to one another and to induced A/J anti-Ar antibodies in their fine specificities. Together with previous data on amino acid sequences and serological properties, the results indicate that, despite their microheterogeneity, members of the CRIA family are closely related in structure and hapten-binding specificity.

Voice pitch as an aid to lipreading

The totally deafened adult, unable to make use of a hearing aid, has no alternative to lipreading for everyday communication. Lipreading, however, is no substitute for hearing speech. Many lipreaders have great difficulty in ideal conditions and even the best lipreaders find the task demanding and tiring. Prosthetic attempts to substitute for lost hearing have centred on three distinct types of intervention, visual, tactile, and electrocochlear. As none of these is likely to yield a good understanding of a speech independent of lipreading in the near future, we have attempted to isolate relatively simple patterns of stimulation that, although not intelligible in themselves, well aid lipreading. From this point of view, the fundamental frequency or 'pitch' of the voice is the most important pattern element because if provides both segmental and suprasegmental information and is practically invisible. It thus complements the visual information already available on the face. As we show here, with the voice pitch presented acoustically, normal listeners can lipread a speaker reading continuous text at up to two and a half times the rate possible on the basis of lipreading alone. The pitch signal by itself, of course, is completely unintelligible. Although our work is primarily concerned with methods of electrical stimulation of the cochlea, it has implications for other sensory substitution techniques, the design of special purpose hearing aids and current theories of speech perception.

External electrical stimulation of the cochlea: clinical, psychophysical, speech-perceptual and histological findings

Our progress towards the development of a particular form of cochlear implant for the totally deaf is described. A single channel stimulation at the round window or promontory is used. This involves a minimum of surgical intervention and infective risk, preserves the possibility of remission and allows the application of later developments. The signal used for stimulation is designed to be matched both to the deaf lip-reader's needs and to his new, restricted, auditory ability. This is done by concentrating on the acoustic pattern components of speech which carry intonation and voiced-voiceless information. Surgical electrophysical, psychoacoustic and speech perceptual aspects of our work with twelve patients are described. The tests involve responses, for example, relating to: threshold for sinusoids; frequency difference limens; periodic -aperiodic discrimination; stress placement; and consonant labelling using combined visual and electrical inputs. Relatively extensive measurements were made with six patients. Significant individual differences were found and the sets of responses provide an essential basis for an appraisal of the potential usefulness of our work to the individual patient. Possible reasons for the individual differences are discussed. A brief indication is given of the techniques which we have developed for the future speech training and speech production evaluation of patients with electro-cochlear voice monitoring. The final section of our paper mentions our histological investigation of the effects of this type of stimulation in the guinea pig.

Tune recognition with reduced pitch and interval information

Twenty subjects were tested on their ability to recognize simple tunes from which rhythm information had been removed. Only the first phrase of each tune was presented. The purpose of the experiment was (a) to determine whether stimuli containing only high harmonics can evoke a sense of musical pitch, and (b) to provide a set of data in normal subjects with which the performance of deaf subjects whose auditory nerve is stimulated electrically can be compared. Each subject was tested on five sets of stimuli presented in a counterbalanced order. These stimuli were (I) pulse trains high-pass filtered at 2 kHz, with repetition rates in the range of 100–200 p.p.s.; (2) as in (I) but high-pass filtered at 4 kHz; (3) sinusoids with musical intervals compressed, so that the “octave” was a ratio of I:I·3; (4) sinusoids with the musical intervals expanded, so that the “octave” was a ratio of I:4; (5) sinusoids of a constant frequency in which the normal frequency changes were translated into intensity changes, each semitone being represented by a 3 dB change in level. The results indicate that a pattern of intensity changes does not support tune recognition, and that, although the pitch contour alone allows reasonable performance, subjects do use musical interval information in recognizing tunes. Stimuli containing only high harmonics can provide such interval information, and thus can evoke a sense of musical pitch. Preliminary results from a deaf subject stimulated electrically with an electrode on the surface of the cochlea indicate that such stimulation can also evoke a sense of musical pitch. It is concluded that musical pitch information can be carried in the time-pattern of nerve impulses in the auditory nerve.

Nephrotoxicity of paraquat in man

Renal function studies were performed in three cases of paraquat poisoning. Acute renal failure was observed in all three cases. Glomerular filtration rate improved for two patients who survived three weeks, illustrating the reversible nature of paraquat-induced acute renal failure. A mild to moderate transient proteinuria was observed during the first and second weeks following paraquat ingestion. Renal glucosuria, marked amino aciduria, and increased fractional excretion of phosphorus, sodium, and uric acid were observed. These findings, which have not been previously described in man, are indicative of proximal tubular dysfunction and parallel observations previously made in experimental animals.

Serum ferritin level. Determinant of iron requirement in hemodialysis patients

Seventeen patients without renal failure and 14 patients receiving long-term hemodialysis were studied. Serum and bone marrow ferritin determinations were made at the time of bone marrow aspiration. A good correlation was found between serum ferritin levels and bone marrow iron stores, as well as between bone marrow ferritin levels and iron stores. Serum ferritin determinations appear to give an accurate estimation of bone marrow iron stores, thereby providing a reliable guide for iron replacement therapy and reducing the need for repeated bone marrow aspirations. Serum ferritin levels of less than 105 ng/ml suggest decreased iron stores, and values greater than 120 ng/ml indicate adequate or increased iron stores. Preliminary data also suggest that bone marrow ferritin determinations may be useful in quantitating bone marrow iron stores.

Use of expanded polytetrafluoroethylene grafts for vascular access in hemodialysis: laboratory and clinical evaluation

Vascular access for chronic hemodialysis has evolved considerably over the past 10 years with development of vascular substitutes. The bovine heterograft is the choice of most dialysis centers when a subcutaneous conduit is needed in lieu of an in situ arteriovenous fistula. Bovine grafts have solved some problems, but further improvement in blood access prostheses is needed. Polytetrafluoroethylene (PTFE) grafts were evaluated in a laboratory and clinical study. In animals, PTFE proved to be satisfactory for fistula construction based on patency, incorporation into tissue, and ease of puncture. Ten patients underwent 11 vascular access procedures using PTFE grafts as a conduit. There were no technical operative complications. One graft was occluded by extravasation during dialysis and flow could not be restored. Otherwise, all grafts are patent 9 to 18 months postoperatively. Grafts of 8.0 mm in diameter have not given desirable flow rates, whereas 6.0 mm grafts have. Prolonged bleeding from puncture has been a problem in some cases. Otherwise, PTFE appears to be a satisfactory conduit for hemodialysis vascular access.

Hemodialysis in treatment of acute chloral hydrate poisoning

A young pregnant (32 weeks' gestation) woman with severe chloral hydrate intoxication was treated with hemodialysis. This resulted in dramatic improvement of her profound central nervous system depression, protracted ventricular arrhythmias, fetal distress, and resumption of spontaneous respiration. The blood concentration of trichloroethanol was measured hourly during the dialysis and its dialysance was calculated. This experience suggests that hemodialysis may be a useful adjunct in the treatment of severe chloral hydrate poisoning.

Maintenance hemodialysis in myeloma kidney disease

Maintenance hemodialysis and chemotherapeutic agents were used in the treatment of seven patients with end-stage myeloma kidney disease. Results indicate that with the use of such therapy life can be prolonged substantially. It appears that patients with myeloma-with or without serious extrarenal complications-are suitable candidates for maintenance hemodialysis and should not be denied the treatment even in the face of systemic neoplasm.

Hemodialysis of acute arsenic intoxication with transient renal failure

A striking reduction in serum arsenic level was achieved after four hours of hemodialysis in a patient with acute arsenic intoxication and transient renal failure. Quantitative dialysance of arsenic and a comparison of daily urinary excretion of arsenic with amount removed by dialysis suggested that hemodialysis is indicated in the treatment of acute arsenic intoxication if there is concomitant renal failure. In the presence of normal renal function, supportive measures, including dimercaprol (BAL in Oil) therapy, constitute the best available treatment.

Effect of dialysate calcium concentration on bone disease in patients on hemodialysis

Plasma biochemistry, bone radiology and morphometry were studied in a group of 20 patients receiving maintenance hemodialysis. The aim was to determine if increasing the dialysate calcium concentration would decrease plasma parathyroid hormone and improve the radiologic appearances of bone in patients without producing serious side effects. Dialysate calcium concentration was increased stepwise from 4.5 to 6.0 and then to 7.0 mg/100 ml. Mean predialysis plasma calcium concentration increased from 9.4 to 9.7 and then to 10.0 mg/100 ml and mean predialysis phosphate concentration increased from 5.3 to 5.6 mg/100 ml. Parathyroid hormone concentration was elevated in all patients but the mean concentration did not change significantly although in seven patients a decrease occurred. Six patients had radiologic signs of renal bone disease, two patients showed improvement and three patients developed bone disease during the study. The patients with radiologic bone disease had the highest parathyroid hormone concentrations and the majority were female. Morphometric bone measurements showed that bone loss during the study occurred mainly in the male patients. Soft tissue calcification continued to appear during the study. Although the response to some patients to an increased dialysate calcium concentration was favorable, it was impossible to predict which types of patient would benefit from the use of a dialysate calcium concentration of 7.0 mg/100 ml.

Toward Relativization of Psychophysical “Relativity”

A paradoxical feature of Weber's law is considered. The law presumably states a principle of psychophysical relativity, yet a pre-relativistic physical measurement model has been traditionally employed. Classical physics, Einsteinian relativity and a newer interpretation of the relativity concept are discussed. Their relation to psychophysics is examined. The domain wherein Weber's law breaks down is noted as suggestively similar to that in which physicists report relativistic effects. A tentative hypothesis is offered to stimulate further thought about a more meaningful integration of psychophysics with modern physical science.

Compression neuropathy subsequent to renal transplantation

Compression neuropathy occurred in 7 patients who underwent renal transplantation. The neuropathy occurred on the same side as the surgery and was associated with the use of selfretaining retractors. Other contributing factors were presence and degree of uremia and diabetes. We suggest that self-retaining retractors be used carefully and length of application reduced to a minimum. Efficient dialysis prior to transplantation may decrease the incidence and severity of neurologic deficit by reducing the extent of uremia.

Insulin and growth hormone secretion in the nephrotic syndrome

Carbohydrate metabolism was studied in a series of patients with the nephrotic syndrome and compared with a similar number of normal controls. The nephrotic syndrome was associated with a smaller secretion of insulin in response to intravenous glucose and tolbutamide than occurred in normals. In the syndrom fasting serum growth hormone (G.H.) concentrations were increased and did not show the characteristic suppression after glucose administration, and the disappearance rate of glucose (k value) was lower. well marked correlation existed between serum G.H. concentrations and the total urinary protein excreted. These abnormal findings returned to normal in a patient who underwent a repeat study when the nephrotic syndrome had resolved.

Establishing Validity of Anagram Verbalization

Underwood's (1965) false recognition procedure was adapted to validate the method of anagram verbalization. Overt anagram verbalizations collected from 10 Ss during an earlier study were presented with varying frequency as sound stimuli to a second sample, after the same anagrams were attempted covertly. Following the stimulus list, the second sample of Ss ( N = 29) estimated the number of times each sound had been read. Frequency judgments of sounds which had occurred commonly among Ss in the previous study were significantly greater than judgments of sounds occurring only once in the first sample. It is concluded that sounds which appeared frequently on an overt basis also occurred covertly, inflating subsequent estimates of list occurrence. The findings are interpreted as validating the method of anagram verbalization.

Interdependence of exchangeable sodium and plasma renin concentration in determining blood pressure in patients treated by maintenance dialysis

Plasma renin concentration and exchangeable sodium were measured in 13 patients with terminal renal failure maintained by dialysis therapy. Blood pressure in seven "responsive" patients was controlled by ultrafiltration but was not controlled in six "resistant" patients. Plasma renin concentration was inversely related to exchangeable sodium in the responsive group but was inappropriately high for the level of exchangeable sodium in the resistant group. There was a better correlation between mean blood pressure and the product of plasma renin concentration and exchangeable sodium than with renin concentration alone.These results indicate that a severely diseased kidney can respond to changes in exchangeable sodium by alterations in renin secretion and they also support the concept that the potential pressor effect of renin is modified by exchangeable sodium. The product of the two factors might be used to determine the "effective" plasma renin concentration in respect of blood pressure.