[Considerations concerning the perioperative use of metamizole]

BACKGROUND

The non-opioid analgesic metamizole (dipyrone) is approved for the treatment of severe pain and is often used in the perioperative period. As it can cause agranulocytosis, a severe adverse event, its perioperative administration is controversially discussed.

OBJECTIVE

Is there enough evidence for a high risk of metamizol-induced agranulocytosis (MIA)? What are the consequences of its perioperative use with respect to the risk profiles of alternative analgesics?

MATERIAL AND METHODS

Rapid review of the literature on the risk of MIA and adverse effects of non-opioid analgesics.

RESULTS

The incidence of MIA is estimated to be one case per million inhabitants per year. The risk seems low compared to other drugs associated with a risk of agranulocytosis, such as antithyroid drugs and ticlopidine. The risk profile of metamizole concerning hepatotoxicity, nephrotoxicity, bleeding and cardiovascular adverse effects is favorable compared to other non-opioid analgesics. None of the non-opioid analgesics are licensed to be administered intraoperatively.

CONCLUSION

The perioperative use of metamizole is possible after a thorough evaluation of the indications as it provides good analgesia with a generally favorable side effect profile and is administered intravenously. The risk of agranulocytosis is small but needs to be mentioned during patient informed consent in order to optimize early recognition. Intraoperative administration aims at reducing the expected severe postoperative pain. A documentation and justification for the evaluation of the indications are recommended.

The Effects on Platelet Aggregation and Prostanoid Biosynthesis of two Parenteral Analgesics: Ketorolac Tromethamine and Dipyrone

The pharmacokinetics and effects on platelet function of dipyrone (1.0 g; 2.5 g; i. v.) and ketorolac tromethamine (30 mg; i.m.) were studied in a three-way crossover study in twelve healthy subjects. The biosynthesis of thromboxane A2 in clotting whole blood ex vivo as well as collagen-induced platelet aggregation were determined before and up to 48 h after administration. Both prostanoid biosynthesis and platelet aggregation were inhibited by ketorolac tromethamine for a significantly longer period of time than by both doses of dipyrone. The changes in platelet functions correlated well with the serum concentrations of ketorolac or 4-methylaminoantipyrine and 4-aminoantipyrine. Using the sigmoidal Emax model the mean serum concentration (SD) of ketorolac, 4-methylaminoantipyrine and 4-aminoantipyrine inhibiting platelet TXB2 generation by 50% (EC50) in vitro was found to be 0.088 ± 0.031, 1.2 ± 0.3 and 10.2 ± 3.4 µg ml-1, respectively. In conclusion the recovery of platelet function after dipyrone administration is faster as compared to ketorolac tromethamine. This is in line with clinical observations and may be an advantage when these drugs are given as postoperative analgesics at the doses tested.

Prediction of persistent post-operative pain: Pain-specific psychological variables compared with acute post-operative pain and general psychological variables

BACKGROUND

Psychological variables and acute post-operative pain are of proven relevance for the prediction of persistent post-operative pain. We aimed at investigating whether pain-specific psychological variables like pain catastrophizing add to the predictive power of acute pain and more general psychological variables like depression.

METHODS

In all, 104 young male patients undergoing thoracic surgery for pectus excavatum correction were studied on the pre-operative day (T0) and 1 week (T1) and 3 months (T2) after surgery. They provided self-report ratings (pain-related: Pain Catastrophizing Scale, Pain Anxiety Symptoms Scale = PASS, Pain Vigilance and Awareness Questionnaire = PVAQ; general psychological: Screening for Somatoform Symptoms, State-Anxiety Inventory-X1, Center for Epidemiologic Studies Depression Scale = CES-D). Additional predictors (T1) as well as criterion variables (T2) were pain intensity (Numerical Rating Scale) and pain disability (Pain Disability Index).

RESULTS

Three months after surgery, 25% of the patients still reported clinically relevant pain (pain intensity ≥3) and over 50% still reported pain-related disability. Acute post-operative pain as well as general psychological variables did not allow for a significant prediction of persistent post-operative pain; in contrast, pain-related psychological variables did. The best single predictors were PASS for pain intensity and PVAQ for pain disability.

CONCLUSIONS

Pain-related psychological variables derived from the fear-avoidance model contributed significantly to the prediction of persistent post-operative pain. The best possible compilation of these measures requires further research. More general psychological variables may become relevant predictors later in the medical history.

SIGNIFICANCE

Our results suggest that pain-specific psychological variables such as pain anxiety and pain hypervigilance add significantly to the prediction of persistent post-operative pain and might even outperform established predictors such as acute pain and general psychological variables. Clinicians might benefit from the development of time-economic screening tools based on these variables.

[Psychological prophylaxis training for coping with postoperative pain. Long-term effects]

INTRODUCTION

The present study was performed to investigate the effect of multidimensional psychological prophylaxis training focusing on coping with cognitive-emotional pain on recovery within the first 12 months after surgery. The training included the following three components: (1) education about pain, analgesia and psychological aspects of coping with pain, (2) training for coping with pain and (3) body-centered relaxation.

MATERIAL AND METHODS

In the study 48 young male patients (surgical correction of a chest malformation) were assessed 1 day before surgery, at discharge and 3, 6 and 12 months postoperatively concerning postoperative pain intensity and pain disability as well as pain anxiety, pain catastrophizing and pain hypervigilance. Additionally, 24 of these patients received training on cognitive-emotional coping with pain 1 day before surgery and 1-3 days after surgery (each session 1 h).

RESULTS

The proportion of patients with clinically relevant improvement was significantly higher in the training group compared to the control group. This was the case for acute pain intensity (approximately 1 week after surgery), pain disability 3 months later and pain anxiety 12 months after surgery.

CONCLUSION

The resurgence of pain anxiety after 12 months could only be found in the control group and could be due to the upcoming surgical removal of the transsternal metal implant. The prophylaxis training can therefore be seen as a protective factor for long-term management of surgery-related consequences and future pain experiences.

[Multidisciplinary assessment for multimodal pain therapy. Indications and range of performance]

According to evidence-based German national guidelines for non-specific low back pain, a broad multidisciplinary assessment is indicated after persisting pain experience of 6 weeks in order to check the indications for an multi- and interdisciplinary pain therapy program. In this paper the necessary topics, the content and the disciplines involved as well as the extent of the multidisciplinary assessment are described as developed by the ad hoc commission on multimodal pain therapy of the German Pain Society.

[Structure and process quality of multimodal pain therapy. Results of a survey of pain therapy clinics]

Multimodal therapy has demonstrated good clinical effectiveness in the treatment of chronic pain syndromes. However, within the German health system a comprehensive and nationwide access to multimodal therapy is not available and further improvement is therefore necessary. In order to analyze the current status of multimodal therapy and specifically its structural and procedural requirements and qualities, a survey was carried out in 37 pain clinics with established multimodal treatment programs. An anonymous questionnaire was used for data collection. Results demonstrated that a substantial accordance was found between all pain clinics concerning requirements for space, facilities and staff. Structured multidisciplinary assessments were carried out by all pain clinics even though the amount of time allocated for this varied widely. The main focus of multimodal therapy in all facilities was based on a common philosophy with a cognitive-behavioral approach to reduce patient helplessness and avoidance behavior and to increase physical and psychosocial activities as well as to strengthen self-efficacy. Some differences in the ways and means to achieve these goals could be demonstrated in the various programs.

[Multimodal pain therapy: principles and indications]

Multimodal pain therapy describes an integrated multidisciplinary treatment in small groups with a closely coordinated therapeutical approach. Somatic and psychotherapeutic procedures cooperate with physical and psychological training programs. For chronic pain syndromes with complex somatic, psychological and social consequences, a therapeutic intensity of at least 100 hours is recommended. Under these conditions multimodal pain therapy has proven to be more effective than other kinds of treatment. If monodisciplinary and/or outpatient therapies fail, health insurance holders have a legitimate claim to this form of therapy.Medical indications are given for patients with chronic pain syndromes, but also if there is an elevated risk of chronic pain in the early stadium of the disease and aiming at delaying the process of chronification. Relative contraindications are a lack of motivation for behavioural change, severe mental disorders or psychopathologies and addiction problems. The availability of multimodal pain treatment centers in Germany is currently insufficient.

[Patient-controlled analgesia (PCA) in outpatients with cancer pain. Analysis of 1,692 treatment days]

INTRODUCTION

In the home-care setting, cancer pain patients in need of parenteral analgesia have to be switched to patient-controlled analgesia using portable pumps. But there is a paucity on data on the logistic requirements or the success rate of such a cost-intensive therapy performed by specialized home-care services.

METHODS

In a retrospective study we analyzed data on care intensity, logistics and outcome of 46 consecutive palliative cancer patients with patient-controlled analgesia (PCA) in a home-care setting.

RESULTS

On days 1, 2, and 3 of PCA the switch to parenteral analgesia resulted in a significant increase of the median daily opioid dose in comparison to the dose just prior to PCA. Concurrently, pain scores were significantly reduced. The median duration of PCA was 25 days (range 2-189 days). On average, each patient was seen by the home-care team every 7.4 days. The median duration of the home visits was 60 min (range, 10-190 min). Of the visits 20% were unscheduled, most of these visits being due to problems regarding analgesia. Most patients died at home. Insufficient analgesia required prefinal hospitalization in only a single case.

CONCLUSION

If the indications are correct, intravenous PCA for palliative cancer pain patients results in higher opioid consumption and better pain control. Home-care PCA requires a lot of human and financial resources, but pain-related hospitalization can be prevented.

Challenging the equipotency calculation for transdermal buprenorphine: four case studies

AIMS

Opioids produce analgesia via different pain pathways. The aim of these case studies was to address the issue of opioid rotation or switching, raising the important issue of conversion ratios between different compounds and routes of administration.

RESULTS

We present two cases of neuropathic pain and two cases of nociceptive pain with a significant neuropathic component, which were successfully treated with transdermal buprenorphine after the failure of other opioids.

CONCLUSION

In each case, effective pain relief was produced by a lower dose than the proposed equipotency ratio of 1:75 would indicate, suggesting that a ratio of 1:110 to 1:115 may be more appropriate.

The Superficial Cervical Plexus Block for Postoperative Pain Therapy in Carotid Artery Surgery. A Prospective Randomised Controlled Trial

OBJECTIVES

Rapid and reliable neurological evaluation soon after carotid artery surgery is feasible with modern methods of general anesthesia, but postoperative pain therapy remains a challenge. Use of opioids can mask neurological deficits. We investigated whether superficial cervical plexus block reduced postoperative opioid consumption after carotid endarterectomy.

DESIGN

Prospective, randomised, double-blinded, placebo controlled trial.

METHODS

46 patients undergoing unilateral carotid endarterectomy under general anesthesia were randomized to either superficial cervical block with ropivacaine (n=23) or placebo (n=23). A patient controlled analgesia device (PCA) delivering morphine was provided for all patients. Subjective pain levels (visual analog scale, VAS) were recorded. The primary outcome was total morphine consumption on discharge from the recovery room. Secondary outcomes included arterial pCO2 (as an indicator of central nervous effects of morphine) and patient satisfaction.

RESULTS

No adverse effects of the superficial cervical plexus block were reported. Four patients in the placebo group were excluded because of other drug use post-operatively. Per protocol analysis compared 23 patients in ropivacaine group and 19 patients in the placebo group. The ropivacaine group had a significant reduction in morphine consumption (3.8+/-2.0 versus 12.9+/-4.0, p<0.001), lower maximal pain scores (2.6+/-2.0 versus 5.8+/-1.6, p<0.001), and paCO2 levels (39.0+/-2.6 versus 41.9+/-3.4, p=0.008) at discharge from the recovery room. Patient satisfaction (1=very good to 6=insufficient) was substantially higher in the ropivacaine group (1.7+/-0.7 versus 3.1+/-1.2, p<00.01).

CONCLUSION

The significant and clinically relevant lower morphine consumption and pain score, as well as the substantially higher patient satisfaction demonstrate that superficial cervical plexus block provides effective pain relief for patients undergoing carotid endarterectomy.

Opioidtherapie chronischer Schmerzen bei Kindern

Based on 4 case reports we focus on the peculiarities of long-term pediatric opioid based pain control. Case report #1, emphasizing the importance of adequate opioid dosing with reference to body weight, illustrates that with adequate management oral sustained-release opioid therapy is safe even in infants less than one year old. Case report #2 is the first report on the usage of buccal fentanyl citrate for pediatric break-through pain control. Case report #3 focuses on the adverse effects of opioid pain control in an infant with neurological impairment. Case report #4 reports on the successful tumor pain control using transdermal buprenorphine. We conclude that proven therapeutic strategies for opioid pain control as applied in adults may be adopted for the usage on children in pediatrics. However, it is mandatory to take into account both the pharmacokinetic and pharmacodynamic peculiarities of childhood.

Topische Applikation von Morphingel bei entzündlichen Haut- und Schleimhautläsionen

AIM

The aim of this study was to demonstrate a peripheral local opioid effect using case examples involving inflammatory mucosal and cutaneous lesions.

METHODS

A 0.1% morphine gel, mixed in the hospital pharmacy, was applied several times daily to inflammatory mucosal lesions (oral, anogenital and in one patient to a skin ulcer). The effects and side effects were documented.

RESULT

All patients experienced a significant reduction in pain with the use of topical morphine gel and no side effects were seen.

CONCLUSION

Topical peripheral application of morphine gel is a simple, effective method that can be carried out by patients several times a day with few side effects.

[Pain experience and pain therapy of tumor patients in the view of general practitioners]

AIM

The aim of the study presented in this paper is to find out how general practitioners evaluate their cancer patients' health, quality of life and type and extent of pain. In addition the study aims to get information about the training in pain therapy and palliative medicine.

METHODS

A representative sample of 440 of all Austrian general practitioners was interviewed via a standardized questionnaire. The consent for the questioning had been obtained by telephone.

RESULTS

The state of health and quality of life of the treated cancer patients are described as little satisfying and most unfavourably affected by the disease. The physicians suppose that the patients experience pain more intense than could be expected of them as endurable. Nevertheless the cancer patients appreciate pain therapy.

CONCLUSION

As a result the medical training in pain therapy and palliative medicine should be improved. At the same time the future general practitioners should gain psychological competences, which would consequently provide them with a broad spectrum of treatment needed when dealing with pain patients (suffering from cancer).

[Differentiation of peripheral and central hyperalgesic effects of systemic procaine]

OBJECTIVE

The aim of this study was to differentiate between the peripheral and central analgesic and antihyperalgesic properties of systemic procaine hydrochloride in standardized human pain models.

METHOD

Subcutaneous injections of either 150 mg procaine hydrochloride or saline solution were administered at intervals of 2 weeks on a randomized and double blind basis. During the 90-min infusion and subsequent 60-min monitoring periods, touch sensitivity was determined and in addition two experimental hyperalgesic models were analyzed.

RESULTS

While touch sensitivity was not affected by procaine hydrochloride, development of primary mechanical hyperalgesia was significantly reduced.

CONCLUSION

The concentration of procaine hydrochloride used in our experiment elicited peripheral antihyperalgesic effects without central venous side effects. These results can account for the clinical effect of low-dose procaine hydrochloride in pain conditions exhibiting pronounced hyperalgesia.

Different lipid profiles as constituencies of liquid formula diets do not influence pain perception and the efficacy of opioids in a human model of acute pain and hyperalgesia

Nutritional support and pain control by medication are often used concomitantly, but interactions are hardly investigated. A randomised, double-blind, cross-over study in ten right-handed volunteers was performed evaluating the influence of cholecystokinin (CCK)-excretion on the perception of pain in a standardised model. CCK-excretion was induced by a liquid formula diet with either long- or medium-chain triglycerides (LCT, MCT). Plasma samples were drawn over a 60 min period in 15-min intervals and CCK and somatostatin (SMS) were measured by radioimmunoassay (RIA). Gastric emptying was evaluated by C-13-breath testing. Transcutaneous electrical stimulation at a high current density (5 Hz, 70.1+/-5.8 mA) was used to provoke acute pain and stable areas of secondary mechanical hyperalgesia and pinprick allodynia for 2 h. Ongoing pain ratings as well as extension of pinprick-hyperalgesia and allodynia were compared between both liquid formula diets. In a second series of experiments, alfentanil (4.1+/-0.5 mg) was administered for 90 min using target-controlled infusions and measurements were performed as stated above. Oral administration of LCT as well as MCT may lead to different CCK blood levels, but we found no evidence for CCK-induced effects on pain sensation, touch-evoked allodynia, secondary hyperalgesia or morphine-induced anti-nociception in humans. In our studies, liquid formula diets did not influence acute pain perception or the efficacy of opioids in a human model of pain.

[Preemptive randomized, double-blind study with lornoxicam in gynecological surgery]

AIM

Lornoxicam is a non opioid analgesic belonging to the oxicam group. The aim of this study was to determine whether lornoxicam has a preemptive analgesic effect.

METHODS

This study was carried out in a randomized, double-blind fashion with 66 patients divided into three groups undergoing gynecological operations. Group I was administered 8 mg of lornoxicam i.v. preoperatively followed by an 8-mg bolus every 8 h for a total dose of 24 mg in the first 24 h. Group II was administered 8 mg of lornoxicam i.v. bolus before the end of the operation followed by 8 mg every 8 h for a total dose of 24 mg in the first 24 h. Group III was administered placebo before and after the operation and for the first 24 h. The effectiveness was assessed postoperatively using the visual analogue scale (at rest, on exertion) and by calculating the total analgesic consumption of morphine hydrochloride in the first 24 h following operation. Vital signs and side effects were documented.

RESULTS

Groups I and II demonstrated significantly reduced pain scores compared to group III at various points in time. Group I also demonstrated a weakly significant reduction in analgesic consumption of morphine hydrochloride postoperatively compared to groups II and III.

CONCLUSION

Lornoxicam administered preemptively appears to improve the quality of postoperative analgesia and lead to reduced consumption of opioid analgesics postoperatively in patients undergoing gynecological operations.

[Results of a poll of cancer patients with respect to pain and quality of life]

AIM

Bernatzky et al. recently published a study on the prescribing practices of general practitioners in Austria with respect to the prescribing of opioids in cancer patients. The aim of the study was to assess the adequately of pain therapy and the resulting quality of life in chronic cancer patients.

METHODS

A representative sample of patients was taken from the Carinthian tumor register. These patient were sent a questionnaire alone with an explanatory letter and at a later date a reminder letter by mail.

RESULTS

Of the 1.895 returned questionnaires 665 (35%) were completed. In this study only the data of the 429 patients who indicated that they experienced pain were processed. More than one fifth of the patients complained of a poor or a very poor quality of life and 80% of the patients were limited in their activities of daily living by pain. There are still many prejudices and informational gaps with respect to the effects of morphine. The main focus of treatment was medication therapy and was generally carried out by the family physician. The satisfaction with pain therapy was at best moderate. This is insofar of importance, as the satisfaction with pain therapy has a massive impact on the quality of life.

CONCLUSIONS

More extensive information and education are required with respect to the various options and possibilities of pain control. Explanations of the mode of action and side-effects of pain medication in order to deal with the prejudices. Earlier and more focused use of pain therapy (long duration of pain), and use of coping aids for activities of daily living (limited through pain) and a broadening of the spectrum of treatment are all necessary. Patient satisfaction with pain therapy should be the main focus, as this is the deciding factor in terms of the quality of life.

A new model of electrically evoked pain and hyperalgesia in human skin: the effects of intravenous alfentanil, S(+)-ketamine, and lidocaine

BACKGROUND

The authors used the analgesics alfentanil, S(+)-ketamine, and systemic lidocaine to examine a new human model of experimental pain and hyperalgesia.

METHODS

Transcutaneous electrical stimulation at a high current density (5 Hz, 67.5+/-6.6 mA) was used to provoke acute pain (numeric rating scale, 5 of 10), stable areas of secondary mechanical hyperalgesia to pin prick (43.6+/-32.1 cm2), and light touch (27.5+/-16.2 cm2) for 2 h. Alfentanil, S(+)-ketamine, and lidocaine were applied for 20 min in a double-blind, placebo-controlled, crossover design in 12 subjects using target controlled infusions.

RESULTS

In the placebo session, pain ratings and areas of hyperalgesia were stable during the stimulation period, which facilitated the assessment of analgesic effects. Alfentanil effectively inhibited electrically evoked pain and reduced pin prick hyperalgesia and allodynia during its infusion. S(+)-ketamine-induced inhibition of secondary hyperalgesia was more pronounced and lasted for the whole experimental protocol. Therapeutic levels of systemic lidocaine showed only marginal analgesic effects, but lasting antihyperalgesic effects.

CONCLUSIONS

A new model of electrically induced pain and hyperalgesia was established, which enabled assessment of the time course of analgesic and antihyperalgesic effects with high temporal resolution and minimum tissue damage and which was further validated by use of common intravenous anesthetics.

[Postoperative transcutaneous electrical nerve stimulation (TENS) in shoulder surgery (randomized, double blind, placebo controlled pilot trial)]

BACKGROUND

The aim of this study was to determine whether 3 days of TENS therapy postoperatively after shoulder operations would result in better pain relief and/or reduced analgesic intake when compared to placebo.

METHOD

The study was carried out randomized, double-blind and placebo controlled. Thirty patients were randomized to two groups. The verum group received TENS SM1AKS 80 Hz 6 mA and the placebo group received TENS SM1AKS 80 Hz 0 mA. The pain was assessed pre-operatively using the Hamburg Pain Adjective List. Premedication and Anaesthesia were standardized. TENS was applied to the patients immediately postoperatively for 8 hours and then on the following days 5 times daily for 45 minutes. The effectiveness was evaluated postoperatively using a visual analogue scale (rest, activity), the Hamburg Pain Adjective List and postoperative analgesic consumption.

RESULTS

The visual analogue scale at rest and on activity showed no significant difference between the groups. Postoperative analgesic consumption of morphine hydrochloride in the first 24 hours was at time 8 hours postoperative significantly and at all other time points markedly less in the verum group compared to the placebo group. The sensory secondary scale score of the "Hamburg Pain Adjective List" was significantly lower postoperatively compared to preoperatively in the verum group.

CONCLUSION

We were able to show in this study that TENS applied postoperatively after shoulder surgery clearly reduced analgesic consumption in the first 72 hours. Furthermore there was a significant difference in the pain scores using the "Hamburg Pain Adjective List" in favour of the verum group. TENS applied postoperatively is a effective, simple modality with few side-effects.

Efficacy of peripheral morphine analgesia in inflamed, non-inflamed and perineural tissue of dental surgery patients

In a clinical model of dental pain, the analgesic efficacy of local morphine treatment was examined under three different conditions. Patients undergoing dental surgery were randomly assigned to an injection of local anesthetic (articaine) plus 1 mg morphine either into inflamed (n = 14; trial 1) or non-inflamed (n = 24; trial 2) submucous tissue or perineurally n = 19; trial 3). Patients in the control group for each condition (n = 13, trial 1; n = 26, trial 2; n = 16, trial 3) received articaine plus saline. Postoperative pain intensity was assessed by the visual analog scale (VAS) and numeric rating scale (NRS) at 0, 2, 4, 6, 8, 10, 12, 16, 20, and 24 h. In addition, patients recorded the occurrence of side effects and the supplemental consumption of diclofenac. Immediately after the operation, pain scores were reduced to a similar extent in all groups, most likely due to the local anesthetic effect. Thereafter, pain scores and supplemental consumption of diclofenac were significantly lower in patients receiving 1 mg morphine into inflamed submucous tissue than in the control group for up to 24 h. Patients receiving 1 mg morphine into non-inflamed tissue or perineurally did not show any further reduction in pain scores compared to each control group. Our results show in patients undergoing dental surgery that injection of 1 mg of morphine into inflamed tissue results in significant and prolonged postoperative analgesia, whereas administration into non-inflamed tissue or perineurally is not effective. Thus, consistent with experimental studies, the requirement of an inflammatory process for the occurrence of peripheral opioid effects is also found in the clinical setting.

[Monitoring of patient-controlled analgesia by the nursing staff]

OBJECTIVE

Patient-controlled analgesia (PCA) is employed successfully on surgical wards. Continuous monitoring is important for the safety of the patient and the efficiency of this form of pain therapy. In the study we evaluated the regularity and completeness of monitoring data which had been collected by the nursing staff on the surgical wards.

METHODS

Data on pain intensity, vital signs, and side effects were collected. Additionally, in the case of epidural analgesia, sensory and motor function were tested. In the first four hours after starting the PCA-pump, the nursing staff was instructed to document this data hourly (phase I), followed by a two hour interval until 8 am the next day (phase II). In general, monitoring was continued every four hours up to the discontinuation of the PCA; whereas in our study only forty hours (10 measurements) were included (phase III). Documentation protocols of 637 patients were evaluated and tested for the completeness of the data.

RESULTS

In phase I, the data of 128 patients (20%) were complete. In 173 patients (27%) less than 50% of the data were documented. During phase II, only in 98 patients (15%) the data collection was complete. In 237 patients (37%) less than 50% of the measurements were determined. In phase III, in 205 patients (32%) all measurements, and in 104 patients (16%) less than 50% of the measurements were documented.

CONCLUSION

Complications during PCA become manifest mainly during the first hours after starting the PCA-pump. Especially during these phases, documentation was found to be quite poor. This underlines the importance of an intense cooperation between acute-pain service and nursing staff with periodical training of the staff.

[Management of postoperative pain in children]

TREATMENT OF PAIN: Undertreatment of postoperative pain in children is a problem in clinical practice. This is due to a lack of both knowledge about age-specific aspects of physiology and pharmacology, and routine pain assessment. For example, the fear of side-effects prevents the adequate usage of opioids. It is of major importance to select a route of drug administration where the child feels comfortable with (avoid intramuscular injections). NON-OPIOID ANALGESICS: Non-opioid analgesics are recommended for basic pain treatment after minor surgical procedures. Instead of using the whole multitude of drugs available, the doctor should stick to those drugs he is familiar with (acetaminophen, ibuprofen, diclofenac, dipyrone).

OPIOIDS

Opioid usage requires individual dose titration and careful monitoring of side-effects (respiratory monitoring, sedation score). The strong opioids piritramide and morphine may advantageously be administered as either continuous, or patient-controlled iv- infusion (PCA).

FORMS OF THERAPY

In addition to infiltration anesthesia, intraoperatively applied nerve blocks provide excellent pain relief. Epidural analgesia with local anesthetics and/or opioids via a thoracic or lumbar epidural catheter is a therapeutic option after thoracic or abdominal surgery, or after extensive orthopedic or urological interventions. Adjuvant analgesics and nonpharmacologic interventions, i. e. transcutaneous electrical nerve stimulation (TENS), are primarily indicated in patients suffering from neuropathic pain.

CONCLUSION

The establishment of pain services and the comprehensive education of both the nursing and the medical staff should help to improve postoperative pediatric pain therapy.

[The Bier block as an experimental tool to differentiate peripheral and central effects of analgesics on people]

AIMS

In this study the technique of intravenous regional anesthesia (Bier block) was evaluated as an experimental tool to differentiate peripheral and central effects of analgesics.

METHODS

Touch and pain thresholds were assessed under control conditions and during a prolonged Bier block. In addition, models of experimental pain and hyperalgesia were used (Capsaicin injection, histamine iontophoresis, pinch).

RESULTS

No signs of impaired function of Adelta- und C-fibers were found during a Bier block of up to 30 min after onset of ischemia. In contrast, Abeta-mediated touch sensation declined significantly. On the basis of these results, peripheral mechanisms of action could be verified for low-dose lidocaine and for morphine in the Bier block setting.

CONCLUSIONS

The Bier-block setting can be successfully employed to differentiate peripheral and central modes of action of analgesics.

Low-dose lidocaine reduces secondary hyperalgesia by a central mode of action

Sodium channel blockers are approved for intravenous administration in the treatment of neuropathic pain states. Preclinical studies have suggested antihyperalgesic effects on the peripheral as well as the central nervous system. The objective of this study was to determine mechanisms of action of low-dose lidocaine in experimental induced, secondary hyperalgesia. In a first experimental trial, participants (n=12) received lidocaine systemically (a bolus injection of 2 mg/kg in 10 min followed by an intravenous infusion of 2 mg kg(-1)h(-1) for another 50 min). In a second trial, a modified intravenous regional anesthesia (IVRA) was administered to exclude possible central analgesic effects. In one arm, patients received an infusion of 40 ml lidocaine, 0.05%; in the other arm 40 ml NaCl, 0.9%, served as a control. In both trials capsaicin, 20 microgram, was injected intradermally and time course of capsaicin-induced pain, allodynia and hyperalgesia as well as axon reflex flare was determined. The capsaicin-induced pain was slightly reduced after systemic and regional application of the anesthetic. The area of pin-prick hyperalgesia was significantly reduced by systemic lidocaine, whereas the inhibition of hyperalgesia was absent during regional administration of lidocaine. In contrast, capsaicin-induced flare was significantly decreased after both treatments. We conclude that systemic lidocaine reduces pin-prick hyperalgesia by a central mode of action, which could involve blockade of terminal branches of nociceptors. A possible role for tetrodotoxin resistant sodium channels in the antihyperalgesic effect of low-dose lidocaine is discussed.

The effects of intradermal fentanyl and ketamine on capsaicin-induced secondary hyperalgesia and flare reaction

In this study, we evaluated the effects of intradermal fentanyl and ketamine on capsaicin-induced hyperalgesia and axon-reflex flare. In addition, we obtained dose-response curves for possible local anesthetic effects. Saline (200 microL) and either fentanyl (1 microg or 10 microg in 200 microL) or ketamine (100 microg or 1000 microg in 200 microL) were injected simultaneously into the central volar forearm of 12 healthy volunteers. Nine minutes later, capsaicin (10 microg in 20 microL) was injected intracutaneously exactly between the two injection sites. Areas of touch-evoked allodynia and pinprick hyperalgesia, as well as intensity of pinprick hyperalgesia at the injection sites and axon-reflex flare, were evaluated. Fentanyl did not affect the area or intensity of secondary hyperalgesia. Only the larger concentration of fentanyl locally diminished axon-reflex flare without affecting mechanical detection thresholds. Inhibitory effects of ketamine on intensity of secondary hyperalgesia and axon reflex flare were observed only in the larger concentration. However, this concentration also clearly elevated mechanical detection thresholds. No inhibitory effects of ketamine in the smaller concentrations were observed. We conclude that fentanyl inhibits neuropeptide release on peripheral application without modulating secondary hyperalgesia. Ketamine failed to inhibit both secondary hyperalgesia and axon reflex flare as long as nonlocal anesthetic concentrations were applied.

IMPLICATIONS

We investigated the peripheral effects of fentanyl and ketamine on capsaicin-induced hyperalgesia and axon-reflex flare. In large concentrations, the opioid diminished axon-reflex flare without effects on secondary hyperalgesia. We found no evidence for the involvement of endogenous glutamate in secondary hyperalgesia or axon reflex flare.

[Pre-emptive analgesia with ropivacaine in adult tonsillectomy]

AIM OF INVESTIGATION

We examined whether a pre-emptive analgesic effect could be achieved with ropivacaine, which has less cardiovascular and central nervous system toxicity than bupivacaine, in adults undergoing tonsillectomy.

METHODS

The study was carried out in 80 patients in a randomised, double-blind fashion. The patients were randomly assigned to one of four groups. In group I, 3 ml ropivacaine 7.5 mg/ml were injected pre-operatively 5 minutes before the start of OR into each tonsil bed. In group II, 3 ml ropivacaine 7.5 mg/ml were injected post-operatively into each tonsil bed. In group III, 3 ml NaCl were injected pre-operatively 5 minutes before the start of OR into each tonsil bed. In group IV, 3 ml NaCl were injected post-operatively into each tonsil bed. The analgesic effectiveness was measured post-operatively by the use of a visual analogue scale, a numeric rating scale (at rest and during activity) and by measuring the total analgesic consumption (mefenamic acid) in the first 192 hours. In addition the time of first analgesic request was noted. Vital parameters and side-effects were documented.

RESULTS

There was no significant difference between the groups in the time of first analgesic request. Likewise, there was no significant difference in the post-operative cumulative analgesic consumption between the four groups. The post-operative administration of ropivacaine resulted in significantly lower pain scores at certain time points compared with the other groups as measured both with the visual analogue scale and the numeric rating scale (at rest). It must be emphasized, that the pain scores both at rest and with exertion remain high and that the net analgesic consumption (per day) remains constant for the first 8 post-operative days.

CONCLUSIONS

We could demonstrate no significant pre-emptive analgesic effect with ropivacaine in adults undergoing tonsillectomy in our study. One can, however, recommend the administration of ropivacaine post-operatively after tonsillectomy, since a reduction of pain scores can thereby be achieved. For post-operative analgesia we recommend the combination of a non-opioid analgesic with a weak opioid.

[Structure quality in outpatient care of chronic pain patients]

BACKGROUND

Outcome quality of medical treatment depends on structure quality of the treatment facility. In the present study we tried evaluate structural parameters of outpatient treatment facilities relating to management of headache, low back pain and cancer pain.

METHODS

109 outpatient treatment facilities (104 offices, 3 outpatient departments of hospitals, 2 pain ambulances of hospitals) in middle franconia, one of the larger Bavarian administrative division (population: 1,6 Mio.), have been evaluated by questionnaires. Questions examined certain structural conditions of the treatment facility as compared to german guidelines for outpatient treatment of pain patients ("Schmerztherapievereinbarung").

RESULTS

Only one treatment facility worked within an interdisciplinary setting. Less than 25% (median) of total patients of an outpatient treatment facility suffered from acute or chronic headache, low back pain or cancer pain. 38% of physicians participated regularly on pain conferences. Established methods for diagnosis and documentation of patients suffering from chronic headache, chronic back pain and cancer pain were regularly used by 16%, 12% and 10% of physicians, respectively. Regular interdisciplinary cooperation in the management of patients with chronic headache, chronic back pain and cancer pain was indicated by 28%, 24% and 41% of physicians, respectively. However, personal discussion of patient related problems took place in less than 5% of physicians. Although a considerable number of different therapies (included as standard therapy for outpatient management of chronic pain in the "Schmerztherapievereinbarung") can be applied in each outpatient treatment facility (median:5), psychological therapy for management of chronic headache, chronic back pain and cancer pain was used regularly by 5%, 2% and 7% of physicians, respectively. Scoring of all examined structural parameters provides a measure for the quality of the parameters of a certain outpatient treatment facility as compared to that of an optimal outpatient facility for pain treatment (quality score=100%). However, 75% of examined outpatient treatment facilities reached quality scores only up to 43%.

CONCLUSIONS

There are considerable structural deficits in outpatient treatment facilities involved in management of patients suffering from chronic headache, chronic back pain and cancer pain. Realisation of standards according to the "Schmerztherapievereinbarung" needs organisation of an interdisciplinary network between the different specialties necessary for pain management. Interdisciplinary cooperation should be supported by the official organization of the medical self-government in Germany--the Kassenärztliche Vereinigung--which has to assure optimal conditions for outpatient treatments.

Peripheral antihyperalgesic effect of morphine to heat, but not mechanical, stimulation in healthy volunteers after ultraviolet-B irradiation

The objective of this study was to evaluate direct peripheral analgesic effects of morphine using a peripheral model of hyperalgesia and the technique of IV regional anesthesia (IVRA), thus allowing the differentiation between central and peripheral mechanisms of action. Two spots on the ventral sides of both forearms in 12 volunteers were irradiated with ultraviolet (UV)-B to induce thermal and mechanical hyperalgesia. One day after the induction of the inflammatory reaction, 40 mL of morphine hydrochloride 0.01% was administered via IVRA. Calibrated heat and phasic mechanical stimuli were applied to differentially determine impairments of tactile and nociceptive perception. Touch and phasic mechanical stimuli of noxious intensity to normal skin did not reveal altered responsiveness caused by morphine. In contrast, the administration of morphine significantly increased heat pain thresholds in the UV-B-pretreated skin areas. The peripheral antihyperalgesic effects of morphine were demonstrated only in inflamed skin areas. Direct central analgesic effects were ruled out by the lack of measurable plasma concentrations of morphine and its metabolites. Morphine 0.01% significantly diminished thermal, but not mechanical, hyperalgesia by a peripheral mode of action, which suggests inhibition of effector pathways leading to heat, but not mechanical, sensitization.

IMPLICATIONS

The peripheral analgesic effects of morphine were studied using modified IV regional anesthesia. When administered 1 day after the induction of dermal inflammation, morphine 0.01% diminished heat, but not primary mechanical, hyperalgesia. Therefore, suppression of mechanical hyperalgesia seen in previous studies could be predominantly due to inhibition of secondary (central) mechanical hyperalgesia.

Low-dose lidocaine suppresses experimentally induced hyperalgesia in humans

BACKGROUND

The antinociceptive effects of systemically administered local anesthetics have been shown in various conditions, such as neuralgia, polyneuropathy, fibromyalgia, and postoperative pain. The objective of the study was to identify the peripheral mechanisms of action of low-dose local anesthetics in a model of experimental pain.

METHODS

In a first experimental trial, participants (n=12) received lidocaine systemically (a bolus injection of 2 mg/kg in 10 min followed by an intravenous infusion of 2 mg x kg(-1) x h(-1) for another 50 min). In a second trial, modified intravenous regional anesthesia was administered to exclude possible central analgesic effects. In one arm, patients received an infusion of 40 ml lidocaine, 0.05%; in their other arm, 40 ml NaCl, 0.9%, served as a control. In both trials, calibrated tonic and phasic mechanical and chemical (histamine) stimuli were applied to determine differentially the impairment of tactile and nociceptive perception.

RESULTS

Mechanical sensitivity to touch, phasic mechanical stimuli of noxious intensity, and heat pain thresholds remained unchanged after systemic and regional application of the anesthetic. In contrast, histamine-induced itch (intravenous regional anesthesia), axon reflex flare (systemic treatment), and development of acute mechanical hyperalgesia during tonic pressure (12 N; 2 min) of an interdigital web was significantly suppressed after both treatments.

CONCLUSIONS

Increasing painfulness during sustained pinching has been attributed to excitation and simultaneous sensitization of particular Adelta- and C-nociceptors. This hyperalgesic mechanism seems to be particularly sensitive to low concentrations of lidocaine. These findings confirm clinical experience with lidocaine in pain states dominated by hyperalgesia.

[Pain therapy in pediatric oncology]

Malignancy-related pain is of similar frequency in children and adolescents as in adults. In children too evaluation of pain intensity, character and location is the basis for individually adapted pain therapy. The choice of medication is determined by the pathophysiological cause and the intensity of the pain. In addition to non-opioid analgesics, tramadol is used for moderate, and morphine for severe, pain. In the case of neuropathic pain, coanalgesics are employed. If oral treatment with morphine is no longer possible, pain pumps for continuous parenteral treatment must be used in children too. Provided the appropriate medical care is possible, parenteral treatment with potent opioids can also be applied at home. In children, every effort must be made to make painful diagnostic and therapeutic measures as painfree as possible.

Peripheral morphine analgesia in dental surgery

The recent identification of opioid receptors on peripheral nerve endings of primary afferent neurons and the expression of their mRNA in dorsal root ganglia support earlier experimental data about peripheral analgesic effects of locally applied opioids. These effects are most prominent under localized inflammatory conditions. The clinical use of such peripheral analgesic effects of opioids was soon investigated in numerous controlled clinical trials. The majority of these have tested the local, intraarticular administration of morphine in knee surgery and have demonstrated potent and long-lasting postoperative analgesia. As the direct application of morphine into the pain-generating site of injury and inflammation appears most promising, we examined direct morphine infiltration of the surgical site in a unique clinical model of inflammatory tooth pain. Forty-four patients undergoing dental surgery entered into this prospective, randomized, double-blind study. Before surgery they received, together with a standard local anesthetic solution (articaine plus epinephrine) a submucous injection of either 1 mg of morphine (group A) or saline (group B). Postoperative pain intensity was assessed using the visual analog scale (VAS) and numeric rating scale (NRS) at 2, 4, 6, 8, 10, 12, 16, 20 and 24 h after surgery. In addition, patients recorded the occurrence of side effects and the supplemental consumption of diclofenac tablets. Results of 27 patients were analyzed (group A: n=14, group B: n=13). Pain scores which were moderate to severe preoperatively were reduced to a similar extent in both groups up to 8 h postoperatively. Thereafter, pain scores in group A were significantly lower than those in group B for up to 24 h, demonstrating the analgesic efficacy of additional morphine. The time to first analgesic intake and the total amount of supplemental diclofenac were less in group A than in group B. No serious side effects were reported. Our results show that 1 mg of morphine added to a local anesthetic for dental surgery results in significant improvement of postoperative analgesia. Since the majority of dental surgeries is accompanied with an inflammatory reaction, supplemental morphine may be of benefit for the relief of postoperative dental pain.

[Tramadol infusion for pain therapy following bladder exstrophy surgery in pediatric wards]

We investigated in 17 children (mean 7.1 years) the continuous administration of tramadol following augmentation cystoplasty or exstrophy reconstruction. Mean duration of the tramadol administration on the pediatric ward was 3.8 +/- 1.1 days (initial dosage 0.25 mg/kg/per hour, dose adjustment by the nursing staff). Mean tramadol consumption was 0.21 mg/kg/h on day 1 and was reduced to 0.08 mg/kg/per hour on day 4. Median pain score (assessed with ten-step scales) was 5 before treatment and between 2.5 (day 1) and 0.5 (day 5) during therapy. Lowest oxygen saturations (mean) ranged from 93.8% to 95.2%. Three patients (17.6%) suffered from nausea/vomiting on 3 of 64 treatment days (4.7%). Pruritus and extreme sedation did not occur. The continuous administration of tramadol is a simple and safe procedure following major urological surgery in children.

Intraarticular morphine analgesia in chronic pain patients with osteoarthritis

Controlled clinical studies have shown that local administration of morphine can significantly relieve acute postoperative pain. This analgesic effect is long-lasting (up to 48 h) and is mediated by peripheral opioid receptors. Experimental evidence shows that analgesic effects of peripheral opioids and the density of opioid receptors on peripheral sensory nerves increase with the duration of painful inflammatory processes. This study examines the analgesic effects of 1 mg of morphine injected into the arthritic knee joints of two groups of chronic pain patients (n = 23) suffering from osteoarthritis. Using a randomized, double-blind cross-over design, patients received either an intraarticular injection of morphine and intravenous saline (Group A, n = 13) or an intraarticular injection of saline and intravenous morphine (Group B, n = 10) during Phase I. Seven days later, patients crossed over to the opposite treatment (Phase II). During Phase I, intraarticular morphine resulted in significantly greater pain relief than intraarticular saline, and this effect was present at rest as well as during movement. The analgesic effect was surprisingly long-lasting and extended into Phase II, a carry-over effect that prevented the analysis of Phase II. No side effects were reported. The treatment of arthritic pain by peripherally acting opioids may be a promising alternative to currently available medications that have serious side effects.