Objectively measured activity is not associated with average pain intensity 1 week after surgery: A cross-sectional study

BACKGROUND

Measures of physical activity and pain-related patient-reported outcomes are important components of patient recovery after surgery. However, little is known about their association in the early post-operative period. This study aims to increase this knowledge. Our primary objective was to determine the association between average pain intensity and activity (in steps) 1 week after surgery. Secondary objectives were the association of activity with other patient-reported outcomes, age, sex, comorbidities and body mass index.

METHODS

Data were obtained from the PROMPT sub-project of IMI-PainCare. Patients after breast and endometriosis-related surgery, sternotomy and total knee arthroplasty completed pain-related outcomes questionnaires and wore an ActiGraph activity-tracking device. We correlated steps with average pain intensity on post-operative days 6 and 7. Secondary analyses were done using correlations and t-tests.

RESULTS

In 284 cases, there was no statistically significant correlation between steps and average pain intensity. In addition, none of the 28 secondary analyses showed a statistically significant result.

CONCLUSIONS

Pain-related patient-reported outcome measures and physical activity are separate entities. Both should be measured after surgery to assess patient recovery and to identify treatment deficiencies.

SIGNIFICANCE STATEMENT

Measuring recovery is a multi-dimensional challenge. After surgery, clinicians need to be aware that neither pain intensity nor activity levels tell the whole story. Each can hint to problems and treatment requirements.

Worse health‐related quality of life, impaired functioning and psychiatric comorbidities are associated with excess mortality in patients with severe chronic pain

Background

Severe chronic pain that interferes with daily activities is associated with an increased risk of mortality. We assessed the overall mortality of tertiary chronic pain patients in comparison with the general population, with a special aim to analyse the association of health‐related quality of life (HRQoL) and its dimensions with the risk of death.

Methods

In this prospective observational follow‐up study, patients with non‐cancer chronic pain attended an outpatient multidisciplinary pain management (MPM) episode in a tertiary pain clinic in 2004–2012 and were followed until May 2019. Mortality between the patients and the general population was compared with standardized mortality ratios (SMR) in different age groups. Causes of death and comorbidities were compared among the deceased. Association of mortality and HRQoL and its dimensions, measured with the 15D instrument, was studied with Cox proportional hazards model.

Results

During a mean of 10.4‐year follow‐up of 1498 patients, 296 died. The SMR in the youngest age group (18–49 years) was significantly higher than that of the general population: 2.6 for males and 2.9 for females. Even elderly females (60–69 years) had elevated mortality (SMR 2.3). Low baseline HRQoL at the time of MPM, as well as poor ratings in the psychosocial dimensions of HRQoL, was associated with an increased risk of death.

Conclusions

Our results support the role of HRQoL measurement by a validated instrument such as the 15D in capturing both the physical and the psychological symptom burden, and consequently, an elevated risk of death, in patients with chronic pain.

Significance

Severe chronic pain is associated with elevated mortality. In patients in chronic pain under 50 years old, the mortality was 2.5–3 times higher than in the general population. Psychological distress appears to contribute to the increased mortality. Regular follow‐up by health‐related quality of life (HRQoL) measurement could be useful in identifying patients in chronic pain who are in need of intensive symptom management and to prevent early death.

Sensory profiles in women with neuropathic pain after breast cancer surgery

Purpose

We performed a detailed analysis of sensory function in patients with chronic post-surgical neuropathic pain (NP) after breast cancer treatments by quantitative sensory testing (QST) with DFNS (German Research Network on Neuropathic Pain) protocol and bed side examination (BE). The nature of sensory changes in peripheral NP may reflect distinct pathophysiological backgrounds that can guide the treatment choices. NP with sensory gain (i.e., hyperesthesia, hyperalgesia, allodynia) has been shown to respond to Na⁺-channel blockers (e.g., oxcarbazepine).

Methods

104 patients with at least “probable” NP in the surgical area were included. All patients had been treated for breast cancer 4–9 years ago and the handling of the intercostobrachial nerve (ICBN) was verified by the surgeon. QST was conducted at the site of NP in the surgical or nearby area and the corresponding contralateral area. BE covered the upper body and sensory abnormalities were marked on body maps and digitalized for area calculation. The outcomes of BE and QST were compared to assess the value of QST in the sensory examination of this patient group.

Results

Loss of function in both small and large fibers was a prominent feature in QST in the area of post-surgical NP. QST profiles did not differ between spared and resected ICBN. In BE, hypoesthesia on multiple modalities was highly prevalent. The presence of sensory gain in BE was associated with more intense pain.

Conclusions

Extensive sensory loss is characteristic for chronic post-surgical NP several years after treatment for breast cancer. These patients are unlikely to respond to Na⁺-channel blockers.

Prediction of persistent post-surgery pain by preoperative cold pain sensitivity: biomarker development with machine-learning-derived analysis

Background

To prevent persistent post-surgery pain, early identification of patients at high risk is a clinical need. Supervised machine-learning techniques were used to test how accurately the patients' performance in a preoperatively performed tonic cold pain test could predict persistent post-surgery pain.

Methods

We analysed 763 patients from a cohort of 900 women who were treated for breast cancer, of whom 61 patients had developed signs of persistent pain during three yr of follow-up. Preoperatively, all patients underwent a cold pain test (immersion of the hand into a water bath at 2-4 °C). The patients rated the pain intensity using a numerical ratings scale (NRS) from 0 to 10. Supervised machine-learning techniques were used to construct a classifier that could predict patients at risk of persistent pain.

Results

Whether or not a patient rated the pain intensity at NRS=10 within less than 45 s during the cold water immersion test provided a negative predictive value of 94.4% to assign a patient to the "persistent pain" group. If NRS=10 was never reached during the cold test, the predictive value for not developing persistent pain was almost 97%. However, a low negative predictive value of 10% implied a high false positive rate.

Conclusions

Results provide a robust exclusion of persistent pain in women with an accuracy of 94.4%. Moreover, results provide further support for the hypothesis that the endogenous pain inhibitory system may play an important role in the process of pain becoming persistent.

A machine-learned analysis of human gene polymorphisms modulating persisting pain points to major roles of neuroimmune processes

Background

Human genetic research has implicated functional variants of more than one hundred genes in the modulation of persisting pain. Artificial intelligence and machine‐learning techniques may combine this knowledge with results of genetic research gathered in any context, which permits the identification of the key biological processes involved in chronic sensitization to pain.

Methods

Based on published evidence, a set of 110 genes carrying variants reported to be associated with modulation of the clinical phenotype of persisting pain in eight different clinical settings was submitted to unsupervised machine‐learning aimed at functional clustering. Subsequently, a mathematically supported subset of genes, comprising those most consistently involved in persisting pain, was analysed by means of computational functional genomics in the Gene Ontology knowledgebase.

Results

Clustering of genes with evidence for a modulation of persisting pain elucidated a functionally heterogeneous set. The situation cleared when the focus was narrowed to a genetic modulation consistently observed throughout several clinical settings. On this basis, two groups of biological processes, the immune system and nitric oxide signalling, emerged as major players in sensitization to persisting pain, which is biologically highly plausible and in agreement with other lines of pain research.

Conclusions

The present computational functional genomics‐based approach provided a computational systems‐biology perspective on chronic sensitization to pain. Human genetic control of persisting pain points to the immune system as a source of potential future targets for drugs directed against persisting pain. Contemporary machine‐learned methods provide innovative approaches to knowledge discovery from previous evidence.

Significance

We show that knowledge discovery in genetic databases and contemporary machine‐learned techniques can identify relevant biological processes involved in Persitent pain.

Genetic variation in P2RX7 and pain

Background and aims

P2X7 is a purinoceptor and non-selective cation channel that is activated by extracellular ATP, especially in immune and glia cells. Activation of P2X7 triggers the secretion of several pro-inflammatory substances, such as IL- 1P, IL-18, TNF-α, and nitric oxide. P2X7 activation contributes to the pro-inflammatory response to injury or bacterial invasion and mediates apoptosis. It has been implicated in physiological and pathological conditions such as bone tissue remodelling, inflammation, oncogenesis, depression, and inflammatory, neuropathic and chronic pain. Here, we aim to characterize the effects of variation within the P2RX7 gene, which encodes the P2X7 receptor, on pain and opioid requirements in human patients.

Methods

Pain was assessed in Norwegian and Finnish cohorts. The Norwegian cohort represents the 6th wave of the Tromsø Study, a longitudinal and cross-sectional population based study (N = 3700), whereas the Finnish cohort (BrePainGen) consists of patients who underwent breast cancer surgery (N = 1000). For both cohorts, experimental pain data were analyzed. Pain intensity and tolerance were assessed with cold pressor test and after standardized noxious heat stimulation in both cohorts. In addition, data on acute postoperative pain and opioid requirements were analyzed in the BrePainGen cohort. Postoperative pain and opioid responses were followed during 20 h after surgery. In total, 29 single nucleotide polymorphisms (SNPs) in P2RX7 were genotyped and their association with outcome variables was assessed using linear regression and analysis of variances (ANOVA).

Results

Several P2RX7 SNPs were associated with the pain phenotypes. The strongest associations were seen with cold pain intensity and tolerance. The results of this study will be presented at the meeting.

Conclusions

Our results suggest that P2X7 and genetic varia-tion in the P2RX7-gene are involved in the modulation of human pain responses.

Normal laser-evoked cortical responses in patients with chronic hemibody pain

BACKGROUND

Patients with widespread unilateral chronic pain associated with recurrent herpes simplex virus (HSV) infections show functional and/or structural changes in the insula, anterior cingulate cortex, frontal and prefrontal cortices, as well as the thalamus, suggesting central dysfunction of the pain system in these patients. Central pain has been associated with attenuated laser-evoked cortical responses. We aimed to clarify whether the observed deficient activation of these areas to acute nociceptive stimuli is due to a lesion at a lower level of pain processing pathways.

METHODS

We explored the functional integrity of the ascending nociceptive pathways by recording the cortical-evoked responses to noxious laser stimulation using magnetoencephalography and electroencephalography in eight patients (age 41-51 years, mean 46) with recurrent HSV infections and a history of chronic, spontaneous, widespread unilateral pain, and in nine age-matched healthy control subjects.

RESULTS

The cortical-evoked fields of the HSV patients originating from the secondary somatosensory and posterior parietal cortices, as well as the evoked potentials recorded from the midline, did not differ from those of the control subjects, indicating functionally intact ascending nociceptive pathways.

CONCLUSIONS

The present results show that our patients with chronic hemibody pain do not show signs of spinothalamic tract lesion. This indicates normal processing of sensory aspects of painful stimuli, while higher pain processing areas show altered activation. We conclude that normal laser-evoked magnetic fields (LEF) or laser-evoked potentials (LEP) may not exclude central pain condition.

Why does the impact of multidisciplinary pain management on quality of life differ so much between chronic pain patients?

Aims

To assess the change in quality of life and factors predicting this change in 1425 chronic pain patients treated in a multidisciplinary pain clinic.

Methods

This is an observational follow-up study using the 15D generic health-related quality of life (HRQoL) instrument. Patients filled in the HRQoL questionnaire at baseline, and 6 and 12 months after discharge. To assess if mental factors predicted treatment success, the changes in the overall 15D score were compared and related to the baseline variables of depression and distress. The group of patients, who scored 4 or 5 on the 1–5 scale for the depression and distress dimensions of the 15D instrument, were considered mentally distressed (N =199). They were compared with the non-distressed patients (i.e. those who scored 1; N = 401).

Results

Pain was associated to depression and distress: 85.4% of mentally distressed patients scored 4 or 5 also on the discomfort and symptoms dimension, vs. 51.4% of the non-distressed (p < 0.001). The mean 15D score of the mentally distressed patients improved statistically significantly more (from 0.572 to 0.636, N =141) during the first six months after treatment compared with the 15D of those who were not mentally distressed, who improved only marginally (0.790–0.803, N = 294; p < 0.001).

Conclusions

Patients with more severe depression or distress at baseline appear to gain more from the treatment than those who have less mental distress. In our ongoing study more baseline factors will be evaluated to assess their effect on the success of treatment.

Transforming pain medicine: adapting to science and society

The field of chronic pain medicine is currently facing enormous challenges. The incidence of chronic pain is increasing worldwide, particularly in the developed world. As a result, chronic pain is imposing a growing burden on Western societies in terms of cost of medical care and lost productivity. This burden is exacerbated by the fact that despite research efforts and a huge expenditure on treatment for chronic pain, clinicians have no highly effective treatments or definitive diagnostic measures for patients. The lack of an objective measure for pain impedes basic research into the biological and psychological mechanisms of chronic pain and clinical research into treatment efficacy. The development of objective measurements of pain and ability to predict treatment responses in the individual patient is critical to improving pain management. Finally, pain medicine must embrace the development of a new evidence-based therapeutic model that recognizes the highly individual nature of responsiveness to pain treatments, integrates bio-psycho-behavioural approaches, and requires proof of clinical effectiveness for the various treatments we offer our patients. In the long-term these approaches will contribute to providing better diagnoses and more effective treatments to lessen the current challenges in pain medicine.

Effect of pain on autonomic nervous system indices derived from photoplethysmography in healthy volunteers

BACKGROUND

Photoplethysmographic pulse wave amplitude (PPGA) and heart rate (HR) can be used to measure cold, nociception-induced autonomic responses, or both. The aim of our study was to correlate the intensity of experimental pain to changes in physiological variables reflecting the autonomic nervous system response to pain.

METHODS

PPGA, HR, and subjective measurements of pain intensity were measured in 29 healthy male volunteers during two heat stimuli (43°C and 48°C) and the cold pressor test (CPT). Surgical pleth index (SPI), autonomic nervous system state (ANSS), and ANSS index (ANSSi) were calculated using PPGA and HR.

RESULTS

Pain intensity scores increased on the average by 1.6, 3.5, and 8.1 for the 43°C, 48°C, and CPT stimuli, respectively. The pain intensity scores for all three stimuli groups were significantly different from each other (P<0.001). All three stimuli changed HR, PPGA, SPI, ANSS, and ANSSi values significantly from their respective baseline values (P<0.001 for all). Heat stimuli-induced pain intensity did not correlate with the magnitude of the respective changes in HR, PPGA, SPI, ANSS, and ANSSi. CPT-induced pain intensity correlated with the magnitude of the respective changes in HR, PPGA, SPI, ANSS, and ANSSi. PPGA, ANSSi, ANSS, and SPI differentiated between heat and cold stimuli-induced pain.

CONCLUSIONS

All three thermal stimuli produced a significant change in photoplethysmograph-derived parameters. All photoplethysmograph-derived parameters appear to be suitable to study autonomic nervous system activation.

Inhibitors of catechol-O-methyltransferase sensitize mice to pain

BACKGROUND AND PURPOSE

Catechol-O-methyltransferase (COMT) inhibitors are used in Parkinson's disease in which pain is an important symptom. COMT polymorphisms modulate pain and opioid analgesia in humans. In rats, COMT inhibitors have been shown to be pro-nociceptive in acute pain models, but also to attenuate allodynia and hyperalgesia in a model of diabetic neuropathy. Here, we have assessed the effects of acute and repeated administrations of COMT inhibitors on mechanical, thermal and carrageenan-induced nociception in male mice.

EXPERIMENTAL APPROACH

We used single and repeated administration of a peripherally restricted, short-acting (nitecapone) and also a centrally acting (3,5-dinitrocatechol, OR-486) COMT inhibitor. We also tested CGP 28014, an indirect inhibitor of COMT enzyme. Effects of OR-486 on thermal nociception were also studied in COMT deficient mice. Effects on spinal pathways were assessed in rats given intrathecal nitecapone.

KEY RESULTS

After single administration, both nitecapone and OR-486 reduced mechanical nociceptive thresholds and thermal nociceptive latencies (hot plate test) at 2 and 3 h, regardless of their brain penetration. These effects were still present after chronic treatment with COMT inhibitors for 5 days. Intraplantar injection of carrageenan reduced nociceptive latencies and both COMT inhibitors potentiated this reduction without modifying inflammation. CGP 28014 shortened paw flick latencies. OR-486 did not modify hot plate times in Comt gene deficient mice. Intrathecal nitecapone modified neither thermal nor mechanical nociception.

CONCLUSIONS AND IMPLICATIONS

Pro-nociceptive effects of COMT inhibitors were confirmed. The pro-nociceptive effects were primarily mediated via mechanisms acting outside the brain and spinal cord. COMT protein was required for these actions.

Dexamethasone decreases oxycodone consumption following osteotomy of the first metatarsal bone: a randomized controlled trial in day surgery

BACKGROUND

Dexamethasone may improve multimodal pain management following painful orthopedic day surgery procedures, and decrease the need for post-operative opioids. We hypothesized that dexamethasone would reduce the need for oxycodone after surgical correction of hallux valgus.

METHODS

Sixty patients planned to undergo unilateral osteotomy of the first metatarsal as a day surgery procedure were randomized to receive pre-operatively and 24 h afterwards, orally either dexamethasone 9 mg or placebo. For pain medication, paracetamol and oxycodone capsules for rescue medication were given. The study ended on the evening of the third post-operative day (POD). The primary endpoint was the cumulative oxycodone consumption. Secondary endpoints were maximal pain scores before oxycodone intake and daily oxycodone doses. In addition, adverse effects were documented.

RESULTS

Twenty-five patients in both groups completed the study. The total median (range) oxycodone consumption during the study period was 45 (0-165) mg in the dexamethasone group and 78 (15-175) mg in the placebo group (P=0.049). The major differences in oxycodone consumption were seen on PODs 0-1. In the dexamethasone group, patients reported significantly lower pain scores on PODs 0-1, and significantly less nausea on POD 1. On PODs 2-3 no differences were seen. However, at 2 weeks post-operatively, patient satisfaction to drug therapy did not differ - in both groups 81% would have chosen the same medication again.

CONCLUSION

Oral dexamethasone combined with paracetamol significantly reduced total oxycodone consumption following surgical correction of hallux valgus.

Itraconazole, a potent inhibitor of P-glycoprotein, moderately increases plasma concentrations of oral morphine

BACKGROUND

Individual variation in opioid response is considerable, partly due to pharmacokinetic factors. Transporter proteins are becoming increasingly interesting also in the pharmacokinetics of opioids. The efflux transporter P-glycoprotein can affect gastrointestinal absorption and tissue distribution, particularly brain access of many opioids. The aim of this study was to evaluate whether itraconazole, which is a potent inhibitor of P-glycoprotein and CYP3A4, would change the pharmacokinetics or the pharmacodynamics of oral morphine.

METHODS

Twelve healthy male volunteers ingested, in a randomized crossover study, once daily 200 mg itraconazole or placebo for 4 days. On day 4, 1 h after the last pre-treatment dose, the subjects ingested 0.3 mg/kg morphine. Blood samples for the determination of plasma morphine, morphine-3-glucuronide (M3G), morphine-6-glucuronide (M6G) and itraconazole concentrations were drawn up to 48 h after morphine ingestion. Pharmacodynamic effects were evaluated using a questionnaire, visual analogue scales, a reaction time test, the Digit Symbol Substitution Test and the Critical Flicker Fusion Test.

RESULTS

Itraconazole increased the mean area under the plasma concentration-time curve [AUC (0-9)] of morphine by 29% (P=0.002), its AUC (0-48) by 22% (P=0.013) and its peak plasma concentration by 28% (P=0.035). Itraconazole did not significantly affect the pharmacokinetic variables of M3G or M6G or the pharmacodynamic effects of morphine.

CONCLUSIONS

Itraconazole moderately increases plasma concentrations of oral morphine, probably by enhancing its absorption by inhibiting intestinal wall P-glycoprotein. A possible improvement of morphine penetration to the brain could not be observed.

Effect of paracetamol and coxib with or without dexamethasone after laparoscopic cholecystectomy

BACKGROUND

Pain after laparoscopic cholecystectomy (LCC) is multifactorial. Effective post-operative pain control is necessary in LCC performed as day-case surgery. We studied the efficacy of paracetamol or valdecoxib with or without dexamethasone after LCC.

METHODS

One hundred sixty patients were randomized to four groups of 40 patients. Groups 1 and 3 received parecoxib 40 mg intravenously (IV) during surgery and valdecoxib 40 mg x 1 per os (PO) for 7 post-operative days. Groups 2 and 4 received paracetamol 1 g x 4 IV during surgery and 1 g x 4 PO for 7 days. In addition, Groups 3 and 4 were given dexamethasone 10 mg IV intra-operatively. Propofol and remifentanil were used during surgery. The patients were given oxycodone 0.05 mg/kg IV in phase 1 post-anaesthesia care unit (PACU 1) or 0.15 mg/kg PO in phase 2 post-anaesthesia care unit (PACU 2) as needed to keep visual analogue scale <3/10. The patients were supplied with the study drugs for 7 post-operative days.

RESULTS

Pain intensity, nausea and the need of oxycodone in phase 1 PACU were similar in all groups. Dexamethasone reduced the need of oral oxycodone in phase 2 PACU (7.0 +/- 1.0 mg vs. 9.1 +/- 1.0 mg, P<0.05). Pain intensity was similar in all groups at home. More patients in the parecoxib/valdecoxib groups needed rescue medication on the 1st post-operative day (P<0.001) than paracetamol-treated patients.

CONCLUSION

Paracetamol was as effective as parecoxib/valdecoxib for pain after LCC. Dexamethasone decreased the need of oxycodone in phase 2 PACU. The effect of dexamethasone was similar in paracetamol and parecoxib/valdecoxib patients.

Controlled clinical trials in cancer pain. How controlled should they be? A qualitative systematic review

This qualitative systematic review of the clinical methodology used in randomised, controlled trials of oral opioids (morphine, hydromorphone, oxycodone) for cancer pain underlines the difficulties of good pain research in palliative care. The current literature lacks placebo-controlled superiority trials. Recommendations for future research are discussed.

Perioperative ketamine for acute postoperative pain

BACKGROUND

Postoperative pain management is often limited by adverse effects such as nausea and vomiting. Adjuvant treatment with an inexpensive opioid-sparing drug such as ketamine may be of value in giving better analgesia with fewer adverse effects.

OBJECTIVES

To evaluate the effectiveness and tolerability of ketamine administered perioperatively in the treatment of acute postoperative pain in adults.

SEARCH STRATEGY

Studies were identified from MEDLINE (1966-2004), EMBASE (1980-2004), the Cochrane Library (2004) and by handsearching reference lists from review articles and trials. The manufacturer of ketamine (Pfizer) provided search results from their in-house database, PARDLARS.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of adult patients undergoing surgery, being treated with perioperative ketamine or placebo. Studies where ketamine was administered in addition to a basic analgesic (such as morphine or NSAID) in one study group, and compared with a group receiving the same basic analgesic (but without ketamine) in another group, were also included.

DATA COLLECTION AND ANALYSIS

Two independent reviewers identified fifty five RCTs for potential inclusion. Quality and validity assessment was performed by two independent reviewers. In the case of discrepancy, a third reviewer was consulted. Patient reported pain intensity and pain relief was assessed using visual analogue scales or verbal rating scales and adverse effects data were collated.

MAIN RESULTS

Thirty-seven trials were included (2240 participants). Eighteen trials were excluded.Twenty-seven of the 37 trials found that perioperative subanaesthetic doses of ketamine reduced rescue analgesic requirements or pain intensity, or both. Quantitative analysis showed that treatment with ketamine reduced 24 hour PCA morphine consumption and postoperative nausea or vomiting (PONV). Adverse effects were mild or absent.

AUTHORS' CONCLUSIONS

Ketamine in subanaesthetic dose (that is a dose which is below that required to produce anaesthesia) is effective in reducing morphine requirements in the first 24 hours after surgery. Ketamine also reduces postoperative nausea and vomiting. Adverse effects are mild or absent.

Peri-operative ketamine for acute post-operative pain: a quantitative and qualitative systematic review (Cochrane review)

BACKGROUND

Post-operative pain management is usually limited by adverse effects such as nausea and vomiting. Adjuvant treatment with an inexpensive opioid-sparing drug such as ketamine may be of value in giving better analgesia with fewer adverse effects. The objective of this systematic review was to evaluate the effectiveness and tolerability of ketamine administered peri-operatively in the treatment of acute post-operative pain in adults.

METHODS

Studies were identified from MEDLINE (1966-2004), EMBASE (1980-2004), the Cochrane Library (2004) and by hand searching reference lists from review articles and trials. The manufacturer of ketamine (Pfizer AS, Lysaker, Norway) provided search results from their in-house database, PARDLARS. Randomized and controlled trials (RCTs) of adult patients undergoing surgery, being treated with peri-operative ketamine, placebo or an active control were considered for inclusion.

RESULTS

Eighteen trials were excluded. Thirty-seven trials were included. Twenty-seven out of 37 trials found that peri-operative ketamine reduced rescue analgesic requirements or pain intensity, or both. Quantitative analysis showed that treatment with ketamine reduced 24-h patient-controlled analgesia (PCA) morphine consumption and post-operative nausea and vomiting (PONV). Adverse effects were mild or absent.

CONCLUSION

In the first 24 h after surgery, ketamine reduces morphine requirements. Ketamine also reduces PONV. Adverse effects are mild or absent. These data should be interpreted with caution as the retrieved studies were heterogenous and the result of the meta-analysis can not be translated into any specific administration regimen with ketamine.

The outcome of pain related undergraduate teaching in Finnish medical faculties

Little is known about how other than cancer pain related issues are represented in medical education. A standardised questionnaire was mailed to all medical students who graduated from the five Finnish medical schools in 2001. A total of 387 students received the questionnaire and 41% responded. The students had to evaluate the quantity and the quality of pain teaching. The availability and the participation in the advanced courses or research in pain medicine were asked. The students reported how the IASP curriculum on pain had been covered during the studies. Two clinical cases were presented for diagnosis and treatment. In addition to integrated pain teaching, specific pain education was received by 27% of the students. The departments of anaesthesiology were reported as the major deliverers of teaching of pain. The overall ratings of the pain-related teaching of the faculties varied from 3.4 to 4.6 on a scale of 10. Anatomy, biochemistry, physiology and pharmacology of pain were covered well. The definitions of pain, pain research, sociological issues, paediatric, geriatric and mentally retarded patients' pain were taught most poorly. Only 34% of the students had been offered advanced studies and 15% had been offered research projects in pain medicine. The lack of teaching about the concept of a multidisciplinary pain clinic was recognised by almost all students. The clinical problems were excellently solved. In conclusion, the IASP curriculum is well covered in the present programmes in the Finnish medical faculties. However, the quality and the methods of teaching still need improvement.

Breakthrough pain characteristics and syndromes in patients with cancer pain. An international survey

Breakthrough pain (BKP) is a transitory flare of pain that occurs on a background of relatively well controlled baseline pain. Previous surveys have found that BKP is highly prevalent among patients with cancer pain and predicts more severe pain, pain-related distress and functional impairment, and relatively poor quality of life. An international group of investigators assembled by a task force of the International Association for the Study of Pain (IASP) evaluated the prevalence and characteristics of BKP as part of a prospective, cross-sectional survey of cancer pain. Fifty-eight clinicians in 24 countries evaluated a total of 1095 patients with cancer pain using patient-rated items from the Brief Pain Inventory (BPI) and observer-rated measures. The observer-rated information included demographic and tumor-related data, the occurrence of BKP, and responses on checklists of pain syndromes and pathophysiologies. The clinicians reported BKP in 64.8% of patients. Physicians from English-speaking countries were significantly more likely to report BKP than other physicians. BKP was associated with higher pain scores and functional interference on the BPI. Multivariate analysis showed an independent association of BKP with the presence of more than one pain, a vertebral pain syndrome, pain due to plexopathy, and English-speaking country. These data confirm the high prevalence of BKP, its association with more severe pain and functional impairment, and its relationship to specific cancer pain syndromes. Further studies are needed to characterize subtypes of BKP. The uneven distribution of BKP reporting across pain specialists from different countries suggests that more standardized methods for diagnosing BKP are needed.

Post-thoracotomy pain after thoracic epidural analgesia: a prospective follow-up study

BACKGROUND

Pain becomes chronic in 22-67% of patients who undergo a thoracotomy. Thoracic epidural analgesia (TEA) has replaced less invasive methods to manage postoperative pain. We wanted to find out if active use of TEA, combined with extended pain management at home, reduces the incidence of chronic post-thoracotomy pain.

METHODS

All consecutive thoracotomy patients during a 16-month period were included. On the ward, pain was measured daily by VAS during rest and coughing and the consumption of analgesics was registered. The patients were interviewed one week after discharge by telephone and by a questionnaire after 3 and 6 months to find out how much pain they had.

RESULTS

A total of 114 patients were recruited. The data were analysed from 89 patients who had had TEA and 22 who had had other methods. TEA was effective in alleviating pain at rest and during coughing. In the TEA patients the incidence of chronic pain of at least moderate severity was 11% and 12% at 3 and 6 months, respectively. One week after discharge 92% of all patients needed daily pain medication.

CONCLUSIONS

TEA seems effective in controlling evoked postoperative pain, but technical problems occurred in 24% of the epidural catheters. The incidence of chronic pain was lower compared with previous studies where TEA was not used. The patients had significant pain and needed regular pain medication and instructions during the first week after discharge. Extended postoperative analgesia up to the first week at home is warranted.

Effects of intrathecally administered dexmedetomidine, MPV-2426 and tizanidine on EMG in rats

BACKGROUND

When administered intrathecally, alpha-2 adrenergic agonists produce spinally mediated antinociception, but also rapidly redistribute to supraspinal sites. This investigation the compared EMG effects of intrathecally administered dexmedetomidine, MPV-2426 (fadolmidine), and tizanidine in Sprague-Dawley rats, which has not been previously described.

METHODS

We studied electromyographic (EMG) responses of the head and gastrocnemius muscles, antinociception using the tail-flick test, and sedation by using observer assessment. Saline, dexmedetomidine (0.5 microg, 2.5 microg and 12.5 microg), MPV-2426 (2 microg, 10 microg and 50 microg) and tizanidine (2 microg, 10 microg and 50 microg) were administered intrathecally.

RESULTS

Tizanidine 50 microg, MPV-2426 10 microg and 50 microg, and dexmedetomidine 2.5 microg and 12.5 microg, decreased EMG activity (P < 0.005). Dexmedetomidine 12.5 microg, MPV-2426 50 microg, and tizanidine 10 microg and 50 microg increased tail-flick latencies (P < 0.01). Dexmedetomidine alone significantly increased the magnitude of observer-assessed sedation (P < 0.0001).

CONCLUSION

We conclude that in rats, intrathecally administered dexmedetomidine, MPV-2426 and tizanidine have dose-dependent effects on EMG. At antinociceptive doses, the EMG effects of these three alpha-2 adrenergic agonists differ (dexmedetomidine > MPV-2426 > tizanidine).

Radiofrequency denervation for neck and back pain. A systematic review of randomized controlled trials

BACKGROUND

The diagnosis of cervical or lumbar zygapophyseal joint pain can only be made by using local anesthesia to block the nerves supplying the painful joint. There is a lack of effective treatment for chronic zygapophyseal joint pain or discogenic pain. Radiofrequency denervation appears to be an emerging technology, with substantial variation in its use between countries.

OBJECTIVES

To assess the effectiveness of radiofrequency denervation for the treatment of musculoskeletal pain disorders.

SEARCH STRATEGY

We searched MEDLINE, PsycLIT, and EMBASE from start to February 2002, plus the Cochrane Library 2002, Issue 2. The references of identified articles were checked and three experts in the field of radiofrequency treatment were consulted to identify studies we might have missed.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of radiofrequency denervation for musculoskeletal pain disorders, with no language or date restrictions.

DATA COLLECTION AND ANALYSIS

Two reviewers selected RCTs that met predefined inclusion criteria, extracted the data, and assessed the main results and methodological quality of the selected trials, using standardized forms. Qualitative analysis was conducted to evaluate the level of scientific evidence.

MAIN RESULTS

We found only nine articles, reporting on seven relevant RCTs. Six of the seven were considered to be high-quality. The selected trials included 275 randomized patients, 141 of whom received active treatment. One study examined cervical zygapophyseal joint pain, two cervicobrachial pain, three lumbar zygapophyseal joint pain, and one discogenic low-back pain. The study sample sizes were small, follow-up times short, and there were some deficiencies in patient selection, outcome assessments, and statistical analyses. The level of scientific evidence for the short-term effectiveness of radiofrequency denervation was limited for cervical zygapophyseal joint and cervicobrachial pain, and conflicting for lumbar zygapophyseal joint pain. There was limited evidence suggesting that intradiscal radiofrequency thermocoagulation was not effective for discogenic low-back pain.

REVIEWER'S CONCLUSIONS

The selected trials provide limited evidence that radiofrequency denervation offers short-term relief for chronic neck pain of zygapophyseal joint origin and for chronic cervicobrachial pain; conflicting evidence on the short-term effect of radiofrequency lesioning on pain and disability in chronic low-back pain of zygapophyseal joint origin; and limited evidence that intradiscal radiofrequency thermocoagulation is not effective for chronic discogenic low-back pain. There is a need for further high-quality RCTs with larger patient samples and data on long-term effects, for which current evidence is inconclusive. Furthermore, RCTs are needed in non-spinal indications where radiofrequency denervation is currently used without any scientific evidence.

Ketamine as an adjuvant to opioids for cancer pain

BACKGROUND

Ketamine is a commonly used anaesthetic agent, and in subanaesthetic doses is also given as an adjuvant to opioids for the treatment of cancer pain, particularly when opioids alone prove to be ineffective. Ketamine is known to have hallucinogenic side effects. To date no systematic review of the benefits and harms of adjuvant ketamine for cancer pain has been undertaken.

OBJECTIVES

To determine the effectiveness and adverse effects of ketamine as an adjuvant to opioids in the treatment of cancer pain.

SEARCH STRATEGY

Studies were identified from MEDLINE (1966-2001), EMBASE (1980-2001), CancerLit (1966-2001), the Cochrane Library (Issue 1, 2001); by handsearching reference lists from review articles, trials, and chapters from standard textbooks on pain and palliative care. The manufacturer of ketamine (Pfizer Parke-Davis) provided search results from their in-house database, PARDLARS.

SELECTION CRITERIA

RCTs of adult patients with cancer and pain being treated with an opioid, and receiving either ketamine (any dose and any route of administration) or placebo or an active control.

DATA COLLECTION AND ANALYSIS

Two independent reviewers identified four RCTs for possible inclusion in the review, and 32 case studies/case series reports. Quality and validity assessment was performed by three independent reviewers, and two RCTs were excluded because of inappropriate study design. Patient reported pain intensity and pain relief was assessed using visual analog scales, verbal rating scales or other validated scales, and adverse effects data were collated.

MAIN RESULTS

Two trials were eligible for inclusion in the review and both concluded that ketamine improves the effectiveness of morphine in the treatment of cancer pain. However, pooling of the data was not appropriate because of the small total number of patients (30), and the presence of clinical heterogeneity. Some patients experienced hallucinations on both ketamine plus morphine and morphine alone and were treated successfully with diazepam. No other serious adverse effects were reported.

REVIEWER'S CONCLUSIONS

Current evidence is insufficient to assess the benefits and harms of ketamine as an adjuvant to opioids for the relief of cancer pain. More randomized controlled trials are needed.

Chronic post-sternotomy pain

BACKGROUND

Chronic postoperative pain is a well-recognised problem. The incidence of severe incapacitating pain is about 3-5% after various types of surgery such as thoracotomy, repair of inguinal hernias and mastectomy. Sternotomy causes considerable postoperative pain and patients with chronic post-sternotomy pain are often referred to pain clinics. Epidemiological studies on chronic post-sternotomy pain are scarce, however. The aim of this paper was to study the incidence and possible risk factors of chronic pain following sternotomy operations performed for coronary bypass grafting or thymectomy.

METHODS

Two groups of patients were studied for persistent pain following sternotomy operations. A questionnaire was sent in January 1997 to 71 patients with myasthenia gravis (MG) who had undergone a thymectomy during 1985-1996 and 720 patients who had had coronary bypass grafting (CABG) in 1994 were interviewed by letter. The patients were asked about the presence of pain and other symptoms in the chest, shoulders, arms or legs that they thought were connected to surgery. They were also asked about the quality of the pain and its evolvement with time. The patients' records were checked for details about surgery, anaesthesia and the state of the coronary disease.

RESULTS

The response rate was 87%. The interval between the interview and surgery varied from 6 months to 12 years in the MG group and it was 2-3 years in the CABG group. In the MG group, 27% of the patients reported chronic post-sternotomy pain, which was moderate to severe in 48% of the patients. In the CABG group, 28% of the patients still had post-sternotomy pain, which was moderate to severe in 38% of patients. Of the patients who had post-sternotomy pain, one-third reported sleep disturbances due to the pain.

CONCLUSION

Chronic post-sternotomy pain is an important complication that may have a significant impact on the patient's everyday life. Future studies will show whether minimising complications, improving postoperative care and starting early adequate pain management will reduce the incidence of this problem.

Disodium clodronate in the treatment of diffuse sclerosing osteomyelitis (DSO) of the mandible

Diffuse sclerosing osteomyelitis (DSO) of the mandible is a chronic condition, the cause of which is not known. Jaw pain, occurring irregularly, is a typical symptom. The aim of the study was to assess the effectiveness of disodium clodronate for relieving pain in patients with DSO. Disodium clodronate is a bisphosphonate used to treat diseases of bone and calcium metabolism. Ten DSO patients experiencing pain received disodium clodronate or placebo intravenously on a randomized double-blind basis. Both minimum (300 mg) and maximum (900 mg) doses were well tolerated. Disodium clodronate administration did not result in better immediate pain relief than placebo administration. However, 6 months after treatment there was a statistically significant difference in pain intensity between the groups, with the disodium clodronate group experiencing significantly less pain.

Randomised crossover trial of transdermal fentanyl and sustained release oral morphine for treating chronic non-cancer pain

OBJECTIVES

To compare patients' preference for transdermal fentanyl or sustained release oral morphine, their level of pain control, and their quality of life after treatment.

DESIGN

Randomised, multicentre, international, open label, crossover trial.

SETTING

35 centres in Belgium, Canada, Denmark, Finland, the United Kingdom, the Netherlands, and South Africa.

PARTICIPANTS

256 patients (aged 26-82 years) with chronic non-cancer pain who had been treated with opioids.

MAIN OUTCOME MEASURES

Patients' preference for transdermal fentanyl or sustained release oral morphine, pain control, quality of life, and safety assessments.

RESULTS

Of 212 patients, 138 (65%) preferred transdermal fentanyl, whereas 59 (28%) preferred sustained release oral morphine and 15 (7%) expressed no preference. Better pain relief was the main reason for preference for fentanyl given by 35% of patients. More patients considered pain control as being "good" or "very good" with fentanyl than with morphine (35% v 23%, P=0.002). These results were reflected in both patients' and investigators' opinions on the global efficacy of transdermal fentanyl. Patients receiving fentanyl had on average higher quality of life scores than those receiving morphine. The incidence of adverse events was similar in both treatment groups; however, more patients experienced constipation with morphine than with fentanyl (48% v 29%, P<0.001). Overall, 41% of patients experienced mild or moderate cutaneous problems associated with wearing the transdermal fentanyl patch, and more patients withdrew because of adverse events during treatment with fentanyl than with morphine (10% v 5%). However, within the subgroup of patients naive to both fentanyl and morphine, similar numbers of patients withdrew owing to adverse effects (11% v 10%, respectively).

CONCLUSION

Transdermal fentanyl was preferred to sustained release oral morphine by patients with chronic non-cancer pain previously treated with opioids. The main reason for preference was better pain relief, achieved with less constipation and an enhanced quality of life.

Morphine and alternative opioids in cancer pain: the EAPC recommendations

An expert working group of the European Association for Palliative Care has revised and updated its guidelines on the use of morphine in the management of cancer pain. The revised recommendations presented here give guidance on the use of morphine and the alternative strong opioid analgesics which have been introduced in many parts of the world in recent years. Practical strategies for dealing with difficult situations are described presenting a consensus view where supporting evidence is lacking. The strength of the evidence on which each recommendation is based is indicated.

Role of the delta-opioid receptor in (1DMe)NPYF mediated antinociception

A selective delta-opioid antagonist, naltrindole, was used to study the role of the delta-opioid receptor in the antinociceptive actions of a synthetic NPFF analog, (1DMe)NPYF. I.t. (1DMe)NPYF (5 nmol) produced antinociception in the tail flick test and (1DMe)NPYF (0.5 nmol) potentiated the antinociceptive effect of i.t. morphine 7.8 nmol. (1DMe)NPYF (5 nmol) had an antihyperalgesic effect in carrageenan inflammation and it significantly reduced mechanical allodynia in the spinal nerve ligation model. All these effects were prevented or significantly reduced by pretreatment with naltrindole (28 nmol) (P < 0.01-0.001). These data suggest that activation of spinal delta-opioid receptors plays an important role in mediating the spinal antinociceptive effects of (1DMe)NPYF.

Methadone, ciprofloxacin, and adverse drug reactions

Ciprofloxacin, given to a patient successfully treated with methadone for more than 6 years, caused profound sedation, confusion, and respiratory depression. We suggest that this was caused by ciprofloxacin inhibition of CYP1A2 and CYP3A4 activity, two of the cytochrome p450 isozymes involved in the metabolism of methadone.

Effects of radolmidine, a novel alpha2 -adrenergic agonist compared with dexmedetomidine in different pain models in the rat

BACKGROUND

Intrathecally administered alpha2-adrenoceptor agonists produce effective antinociception, but sedation is an important adverse effect. Radolmidine is a novel alpha2-adrenoceptor agonist with a different pharmacokinetic profile compared with the well-researched dexmedetomidine. This study determined the antinociceptive and sedative effects of radolmidine in different models of acute and chronic pain. Dexmedetomidine and saline served as controls.

METHODS

Male Sprague-Dawley rats were studied in acute pain (tail flick), carrageenan inflammation, and the spinal nerve ligation model of neuropathic pain. Mechanical allodynia was assessed with von Frey filaments, cold allodynia with the acetone test, and thermal hyperalgesia with the paw flick test. Locomotor activity-vigilance was assessed in a dark field. Dexmedetomidine and radolmidine were administered intrathecally in doses of 0.25 microg, 2.5 microg, 5 microg, and 10 microg.

RESULTS

In the tail flick test, radolmidine showed a dose-dependent antinociceptive effect, being equipotent compared with dexmedetomidine. In carrageenan inflammation, intrathecal doses of 2.5 microg or 5 microg of dexmedetomidine/radolmidine produced significant antinociception compared with saline (P < 0.01). The two drugs were equianalgesic. In the neuropathic pain model, an intrathecal dose of 5 microg dexmedetomidine-radolmidine had a significant antiallodynic effect compared with saline (P < 0.01). The two drugs were equipotent. Intrathecal administration of both dexmedetomidine and radolmidine dose dependently decreased spontaneous locomotor acitivity-vigilance, but this effect was significantly smaller after intrathecal administration of radolmidine than after intrathecal dexmedetomidine.

CONCLUSIONS

Radolmidine and dexmedetomidine had equipotent antinociceptive effects in all tests studied. However, radolmidine caused significantly less sedation than dexmedetomidine, probably because of a different pharmacokinetic profile.

The dissociation of sedative from spinal antinociceptive effects following administration of a novel alpha-2-adrenoceptor agonist, MPV-2426, in the locus coeruleus in the rat

BACKGROUND

MPV-2426 is a novel alpha-2-adrenoceptor agonist developed for spinal pain therapy. In the present study we characterized its sedative and antinociceptive properties following microinjections into the brainstem and intrathecally at the lumbar spinal cord level.

METHODS

Sedative effects of MPV-2426 were assessed in a locomotion measuring device following unilateral microinjection into the locus coeruleus (LC) of the brainstem or 1-2 mm rostral to the LC in rats. Antinociceptive effects induced by MPV-2426 in the brainstem, and for comparison intrathecally at the lumbar spinal cord level, were determined with a tail-flick test. Dexmedetomidine was used as the reference alpha-2-adrenoceptor agonist.

RESULTS

MPV-2426 produced a dose-related hypolocomotive/sedative effect, which was significantly stronger following microinjection into the LC than 1-2 mm rostral to the LC. The sedation induced by MPV-2426 was reversed by atipamezole (1 mg/kg s.c.), an alpha-2-adrenoceptor antagonist. The sedative potency of dexmedetomidine, the reference alpha-2-adrenoceptor agonist, was stronger and less dependent on the exact injection site in the brainstem. Following microinjections at sedative doses in the brainstem, only dexmedetomidine produced a significant antinociceptive effect in the tail-flick test. When microinjected into the lumbar spinal cord, MPV-2426 and dexmedetomidine had an equally strong antinociceptive effect in the tail-flick test.

CONCLUSION

The results indicate that the sedative potency of MPV-2426 is considerably weaker than that of dexmedetomidine. Additionally, the spread of MPV-2426 within the central nervous system is more limited than that of dexmedetomidine. This could explain why MPV-2426 is sedative only when injected into the LC while antinociceptive effect is obtained when it is injected intrathecally at the lumbar spinal cord level.

Neuropeptide FF and modulation of pain

Neuropeptide FF (NPFF) and the related longer peptide neuropeptide AF (NPAF) derive from a single gene in several mammalian species. The gene product is expressed mainly in the CNS, where the posterior pituitary and dorsal spinal cord contain the highest concentrations. Evidence from biochemical and immunohistochemical studies combined with in situ hybridization using NPFF gene-specific probes suggest that all NPFF-like peptides may not derive from the characterized NPFF gene, but that other genes can exist which give rise to related peptides. Intraventricular NPFF exerts antiopioid effects, but intrathecal NPFF potentiates the analgesic effects of morphine. NPFF mRNA expression is upregulated in the dorsal horn of the spinal cord after carrageenan-induced inflammation in the hind paw of the rat, but not in the neuropathic pain model induced by ligation of the spinal roots. NPFF produces a submodality-selective potentiation of the antinociceptive effect induced by brain stem stimulation in the spinal cord during inflammation, and this effect is independent of naloxone-sensitive opioid receptors. In neuropathic animals, NPFF injected into the periaqueductal grey produces a significant attenuation of tactile allodynia, which is not modulated by naloxone. NPFF thus modulates pain sensation and morphine analgesia under normal and pathological conditions through both spinal and brain mechanisms.

Systemic physostigmine shows antiallodynic effects in neuropathic rats

The aim of this study was to examine the antiallodynic and antinociceptive effects of subcutaneously administered physostigmine (50, 100, 200 micrograms/kg), compared with morphine (2.5, 5, 10 mg/kg) and NaCl after spinal nerve ligation in rats. The following stimuli were used: acetone (cold allodynia), von Frey hairs (mechanical allodynia), and paw flick test (thermal nociception). Motility boxes were used to investigate the effects of the drugs on motor performance. Physostigmine attenuated both mechanical and cold allodynia dose-dependently but had no effect on the paw flick test. The effect was antagonized by atropine (muscarinic receptor antagonist) but not by mecamylamine (nicotinic receptor antagonist) or naloxone (opioid receptor antagonist). Morphine produced dose-dependent antiallodynic and antinociceptive effects. In the antiallodynic doses, morphine caused severe rigidity. Physostigmine 200 micrograms/kg impaired locomotor activity, but no rigidity was observed.

IMPLICATIONS

Physostigmine has different effects on allodynia and nociception, which suggests that different cholinergic (muscarinic) mechanisms may be involved in neuropathic and nociceptive pain.