Gunnvald Kvarstein

Assessment of pain

UNLABELLED Valid and reliable assessment of pain is essential for both clinical trials and effective pain management. The nature of pain makes objective measurement impossible. Acute pain can be reliably assessed, both at rest (important for comfort) and during movement (important for function and risk of postoperative complications), with one-dimensional tools such as numeric rating scales or visual analogue scales. Both these are more powerful in detecting changes in pain intensity than a verbal categorical rating scale. In acute pain trials, assessment of baseline pain must ensure sufficient pain intensity for the trial to detect meaningful treatment effects. Chronic pain assessment and its impact on physical, emotional, and social functions require multidimensional qualitative tools and health-related quality of life instruments. Several disease- and patient-specific functional scales are useful, such as the Western Ontario and MacMaster Universities for osteoarthritis, and several neuropathic pain screening tools. The Initiative on METHODS Measurement, and Pain Assessment in Clinical Trials recommendations for outcome measurements of chronic pain trials are also useful for routine assessment. Cancer pain assessment is complicated by a number of other bodily and mental symptoms such as fatigue and depression, all affecting quality of life. It is noteworthy that quality of life reported by chronic pain patients can be as much affected as that of terminal cancer patients. Any assessment of pain must take into account other factors, such as cognitive impairment or dementia, and assessment tools validated in the specific patient groups being studied.

A randomized double-blind controlled trial of intra-annular radiofrequency thermal disc therapy--a 12-month follow-up.

ABSTRACT The discTRODE™ probe applies radiofrequency (RF) current, heating the annulus to treat chronic discogenic low back pain. Randomized controlled studies have not been published. We assessed the long‐term effect and safety aspects of percutaneous intradiscal radiofrequency thermocoagulation (PIRFT) with the discTRODE™ probe in a prospective parallel, randomized and gender stratified, double‐blind placebo‐controlled study. Twenty selected patients with chronic low back pain and a positive one‐level pressure‐controlled provocation discography were randomized to either intra‐annular PIRFT or intra‐annular sham treatment. A blinded interim analysis was performed when 20 patients had been followed for six months. The 6‐month analysis did not reveal any trend towards overall effect or difference between active and sham treatment for the primary endpoint: change in pain intensity (0–10). The inclusion of patients was therefore discontinued. After 12 months the overall reduction from baseline pain had reached statistical significance, but there was no significant difference between the groups. The functional outcome measures (Oswestry Disability Index, and SF 36 subscales and the relative change in pain) appeared more promising, but did not reach statistical significance when compared with sham treatment. Two actively treated and two sham‐treated patients reported increased pain levels, and in both groups a higher number was unemployed after 12 months. The study did not find evidence for a benefit of PIRFT, although it cannot rule out a moderate effect. Considering the high number, reporting increased pain in our study, we would not recommend intra‐annular thermal therapy with the discTRODE™ probe.

Quality of life after randomization to laparoscopic versus open living donor nephrectomy: long-term follow-up.

Background. The aim of this randomized study was to compare patient-reported outcome after laparoscopic versus open donor nephrectomy during 1 year follow-up. The evidence base has so far not allowed for a decision as to which method is superior as seen from a long-term quality of life-perspective. Methods. The donors were randomized to laparoscopic (n=63) or open (n=59) nephrectomy, with follow-up at 1, 6, and 12 months. Primary outcomes were health status (SF-36) and overall quality of life (QOLS-N). Secondary outcomes were donor perception of the surgical scar, the donation’s impact on personal finances, and whether the donor would make the same decision to donate again. Results. There was a significant difference in favor of laparoscopic surgery regarding the SF-36 subscale bodily pain at 1 month postoperatively (P<0.05). Analysis based on intention to treat revealed no long-term differences between groups in SF-36 scores. When subtracting the reoperated/converted donors of the laparoscopic group, significant differences in favor of laparoscopy were revealed in the subscales bodily pain at 6 months (P<0.05) and social functioning at 12 months (P<0.05). No significant differences were found in QOLS-N scores between groups. Conclusions. Laparoscopic donor nephrectomy is an attractive alternative to open donor nephrectomy because of less postoperative pain. However, long-term comparison only revealed significant differences in favor of laparoscopy when adjusting for reoperations/conversions. Both groups reached baseline scores in most SF-36 subscales at 12 months and this may explain why possible minor benefits are hard to prove.

Catecholamine-induced excitation of nociceptors in sympathetically maintained pain

Abstract Sympathetically maintained pain could either be mediated by ephaptic interactions between sympathetic efferent and afferent nociceptive fibers or by catecholamine‐induced activation of nociceptive nerve endings. We report here single fiber recordings from C nociceptors in a patient with sympathetically maintained pain, in whom sympathetic blockade had repeatedly eliminated the ongoing pain in both legs. We classified eight C‐fibers as mechano‐responsive and six as mechano‐insensitive nociceptors according to their mechanical responsiveness and activity‐dependent slowing of conduction velocity (latency increase of 0.5 ± 1.1 vs. 7.1 ± 2.0 ms for 20 pulses at 0.125 Hz). Two C‐fibers were activated with a delay of several seconds following strong endogenous sympathetic bursts; they were also excited for about 3 min following the injection of norepinephrine (10 μl, 0.05%) into their innervation territory. In these two fibers, a prolonged activation by injection of low pH solution (phosphate buffer, pH 6.0, 10 μl) and sensitization of their heat response following prostaglandin E2 injection were recorded, evidencing their afferent nature. Moreover, their activity‐dependent slowing was typical for mechano‐insensitive nociceptors. We conclude that sensitized mechano‐insensitive nociceptors can be activated by endogenously released catecholamines and thereby may contribute to sympathetically maintained pain. No evidence for ephaptic interaction between sympathetic efferent and nociceptive afferent fibers was found.

Detection of organ ischemia during hemorrhagic shock.

Background:  In a porcine hemorrhagic shock model we aimed to determine: (a) whether blood flow to the intestine and kidney was more reduced than cardiac output; (b) whether parameters of anaerobic metabolism correlated with regional blood flow; and (c) whether metabolic parameters in intestine, kidney and skeletal muscles detected a compromized metabolic state at an earlier stage than did systemic parameters.

Tissue gas tensions and tissue metabolites for detection of organ hypoperfusion and ischemia

The aim of this study was to evaluate how tissue gas tensions and tissue metabolites measured in situ can detect hypoperfusion and differentiate between aerobic and anaerobic conditions during hemorrhagic shock. We hypothesized that tissue PCO2 (PtCO2) would detect hypoperfusion also under aerobic conditions and detect anaerobic metabolism concomitantly with or earlier than other markers.

Behandling av postoperativ smerte i sykehus

BACKGROUND Relief of post-operative pain has a bearing on the patients well-being, mobilisation and time confined to bed. The article discusses indications, contraindications and the efficacy of the various treatment modalities. MATERIAL AND METHOD We have examined review articles, meta-analyses and randomised controlled trials, identified through literature searches in PubMed. RESULTS The use of several medicines and techniques (multimodal pain treatment) is necessary to achieve a good balance between pain relief, side effects and risk. Systemic administration of paracetamol, NSAIDs, opioids and glucocorticoids is effective for post-operative pain. The same applies to epidural analgesia, peripheral nerve blocks and local anaesthetic wound infiltration. Subanaesthetic doses of ketamine have an opioid-sparing effect, but the optimal dosing regimen is uncertain. Gabapentinoids have an effect on post-operative pain, but the effect appears to vary depending on the type of operation and analgesic regimen. The effect of one analgesic will depend on which other drugs are used in multimodal pain treatment. Epidural analgesia, peripheral nerve blocks or extensive local infiltration analgesia is often necessary to relieve movement-related pain. INTERPRETATION Many treatment modalities are effective for post-operative pain. It is crucial that the treatment is well organised and that it includes routines for systematic pain assessment, efficacy and side effects of the pain management.

Pulsed radiofrequency—Time for a clinical pause and more science

In this issue of the Scandinavian Journal of Pain Akural et al. [1]publish an important study on pulsed radiofrequency, a high qual-ity randomized controlled, double blind study with unfortunately,negative outcome. Their study necessitates a review of the back-ground and history of this fairly recent addition to the tools ofinterventional pain medicine.Thermal radiofrequency neurotomy or continuous radiofre-quency (CRF) has been widely used for chronic pain. Pulsedradiofrequency (PRF) was introduced in 1998 as a non-destructivealternative,andsincethenithasgainedhighpopularityamongpainphysicians. Via a thin needle high voltage radiofrequency currentis delivered in short 20ms bursts, two per second, to the target [2].The long pause between each burst prevents heat accumulating,and the temperature can be kept below 42

Detection of ischemia by PCO2 before adenosine triphosphate declines in skeletal muscle.

ObjectiveIschemia is a serious problem in clinical medicine, and effective methods are needed to detect ischemia before the injury becomes irreversible. In experimental studies on several organs, Pco2 was found to increase rapidly after the onset of supply-dependent anaerobic metabolism. A shortcoming of these studies was that Pco2 was not correlated with tissue concentrations of lactate and the energy status in the cell. Thus, in this study we have measured tissue concentrations of lactate, phosphocreatine, and adenosine triphosphate. We hypothesized that during ischemic conditions, Pco2 reflects lactate generation in the cell and not exhausted energy stores per se. If this is the case, Pco2 can be used to detect ischemia before the energy stores are depleted. Consequently, therapy can be instituted at a time when the organ is salvageable. DesignProspective laboratory study. SettingUniversity research laboratory. SubjectsSeven pigs. InterventionsIn a porcine model, gluteal skeletal muscles with no-flow ischemia were examined. Pco2 was measured both in situ and in vitro at increasing periods of time. Concomitantly, tissue lactate, adenosine triphosphate, and phosphocreatine were analyzed. Measurements and Main ResultsTissue surface CO2 tension (PtCO2) increased rapidly after onset of ischemia. From a baseline of 63 ± 3 torr (8.4 ± 1.2 kPa) under aerobic conditions, it increased to 157 ± 6 torr (21 ± 2.2 kPa) after 30 mins of ischemia and 386 ± 9 torr (51.5 ± 3 kPa) at 120 mins. The rapid increase of PtCO2 correlated well with increasing values of lactate (r2 > .9) in the tissue. Adenosine triphosphate was essentially unchanged for 45 mins after onset of ischemia, after which it declined. Phosphocreatine decreased earlier than adenosine triphosphate in accordance with the notion that high-energy phosphate groups are transferred from phosphocreatine to adenosine triphosphate. ConclusionIn this porcine model of skeletal muscle ischemia, PtCO2 correlates well with tissue lactate and increases long before the energy stores of phosphocreatine and most notably adenosine triphosphate are severely reduced. Thus, PtCO2 could be monitored to detect and treat earlier stages of ischemia.

A new target for radiofrequency neurotomy

Knee osteoarthritis (OA) is one of the most common disabling conditions in the senior population. Pharmacological treatment is often ineffective and the most commonly used treatments, e.g. NSAIDs, are associated with significant adverse effects [1]. Surgery, like joint replacement has become a common approach even among elderly patients. The procedures, however, are still associated with increased mortality and morbidity [8], and for younger patients one has to take into account the increased risk of revisions due to a limited lifetime of the knee joint prostheses [8]. New and potent alternatives to surgery are therefore warranted. Radiofrequency neurotomy has for the last two decades been applied to medial nerve branches of the ramus dorsalis or the dorsal root ganglia although the scientific evidence supporting its use is still limited [4,5]. For non-spinal applications there, in fact, is no scientific evidence available. In this issue of Pain Choi et al. [2] present the first randomized placebo-controlled trial of radiofrequency (RF) neurotomy for severe tibiofemoral OA. Three out of five major genicular nerve branches were coagulated. Although the study is small (n: 38), and the follow up is short (3 months), the results are still highly interesting. The RF group (n: 19) reported significant pain reduction, approximating 50%, and better functional status compared to the control group. The proportion of patients, who reported more than 50% pain relief, was also significantly higher in the RF group (59% vs. 0%). Compared to the effect of RF neurotomy for zygapophyseal joint related pain [3,4] these results are notable. In a highly selected group of neck pain patients, Lord et al. [3] found seven out of 12 patients (58%) pain free after 27 weeks, but among low back patients (n: 20) Nath et al. [4] observed an average pain reduction of only one third or two points on an 11-point numeric pain scale. In both the studies patients were carefully selected, with repeated (total three) test blocks to reduce the risk of false positive results [7]. Furthermore, the patients were only considered eligible for RF treatment when the test blocks respectively provided complete or P80% pain relief [3,4], and, importantly, the neurotomy included several and parallel RF lesions due to interindividual variation of the anatomy. Choi et al. by contrast applied only a single test block, offered RF treatment when the block provided P50% pain relief and performed only a single RF lesion for each nerve. With these less rigorous selection criteria and the simpler RF procedure, a responder rate of 59% (with P50% pain relief) is remarkable. One explanation could be the relatively precise anatomical location of the nerves and careful localization of needles for neurostimulation. Choi et al. moreover applied RF cannulae with a 10 mm active