Erik Vandermeulen

Characterization of a rat model of incisional pain.

&NA; In this study, we developed a rat model of incisional pain. A 1‐cm longitudinal incision was made through skin, fascia and muscle of the plantar aspect of the hindpaw in halothane‐anesthetized rats. Withdrawal responses were measured using von Frey filaments at different areas around the wound before surgery and for the next 6 days. A cumulative pain score based on the weight bearing behavior of the animals was also utilized. The results of tests for withdrawal responses and scores based on weight bearing suggest that a surgical incision of the rat foot causes a reliable and quantifiable mechanical hyperalgesia lasting for several days after surgery. An incision that only included skin and fascia but not muscle in the foot caused less severe hyperalgesia during the initial postoperative period. Distinct areas around the wound had different withdrawal thresholds during the study period. Even remote sites as much as 10 mm from the wound showed persistent mechanical hyperalgesia. Selective denervations of the rat hindpaw prior to foot incision revealed both the sural and tibial nerves were responsible for transmitting input from the incision that produces hyperalgesia. This model should allow us to understand mechanisms of sensitization caused by surgery and investigate new therapies for postoperative pain in humans.

Regional anaesthesia and antithrombotic agents: recommendations of the European Society of Anaesthesiology

Background and objectives Performing neuraxial anaesthesia in patients receiving antithrombotic drugs is controversial due to the increased risk of spinal epidural haematoma. Strict adherence to the recommended time intervals between the administration of anticoagulants, neuraxial blockade and the removal of catheters is thought to improve patient safety and reduce the risk of haematoma. Appropriate guidelines have been prepared by a number of national societies of anaesthesiologists, but they do not have universal acceptance. The introduction of new anticoagulants together with recent reports of stent thrombosis in patients with perioperative cessation of antiplatelet drugs have considerably broadened the issue and made revision necessary. To overcome deficiencies in content and applicability, the European Society of Anaesthesiology has taken the initiative to provide current and comprehensive guidelines for the continent as a whole. Methods Extensive review of the literature. Results and conclusions In order to minimise bleeding complications during regional anaesthetic techniques, care should be taken to avoid traumatic puncture. If a bloody tap occurs when intraoperative anticoagulation is planned, postponing surgery should be considered. Alternatively, catheters can be placed the night before surgery. Regional anaesthesia in patients receiving full anticoagulation treatment continues to be contraindicated. Catheter manipulation and removal carry similar risks to insertion and the same criteria should apply. Appropriate neurological monitoring is essential during the postoperative recovery period and following catheter removal. The final decision to perform regional anaesthesia in patients receiving drugs that affect haemostasis has to be taken after careful assessment of individual risks and benefits.

A Nurse-Led Interdisciplinary Intervention Program for Delirium in Elderly Hip-Fracture Patients

OBJECTIVES: To develop and test the effect of a nurse‐led interdisciplinary intervention program for delirium on the incidence and course (severity and duration) of delirium, cognitive functioning, functional rehabilitation, mortality, and length of stay in older hip‐fracture patients.

Effect of plantar local anesthetic injection on dorsal horn neuron activity and pain behaviors caused by incision

&NA; Hypersensitivity after tissue injury is an expression of neuronal plasticity in the central nervous system. This has been explored most extensively using in vitro preparations and animal models of inflammatory pain and chemical irritation. For pain after surgery, a similar process has been proposed. In the present study, we examined dorsal horn neuron (DHN) sensitization using the plantar incision model for post‐operative pain. In behavioral experiments, the effect of a local anesthetic injection (or saline vehicle) 15 min before plantar incision on pain behaviors several days after incision was studied. Bupivacaine injection before incision prevented pain behaviors until 4 h afterwards; injection after incision produced the same effect. One day after incision, pain behaviors were not different between rats injected with saline or bupivacaine. In neurophysiologic experiments, however, bupivacaine injection blocked activation of DHNs during incision. One hour after incision, expansion of receptive fields (RFs) to pinch and increased background activity occurred in 14 of 16 neurons in the saline group but only in two of 22 neurons in the bupivacaine group. The difference was not due to a systemic effect of bupivacaine. Ten sensitized neurons were studied using the injection of bupivacaine 90 min after incision. Increased background activity (n=7) and expanded RFs (n=7) were reversed by bupivacaine. Sensitization was re‐established in seven of eight neurons 2 h after injection as the local anesthetic dissipated. These results indicate that activation of DHNs during plantar incision and sensitization 1 h later are not necessary for subsequent pain behaviors. Because sensitization was reversed 90 min after plantar incision and then re‐established as the local anesthetic effect diminished, enhanced responsiveness of DHN requires ongoing afferent input during the first day after incision.

Alterations in ascending dorsal horn neurons by a surgical incision in the rat foot

BackgroundLittle is known about the mechanisms of pain caused by a surgical incision. The authors have developed a rat model of postoperative pain characterized by decreased withdrawal thresholds to punctate mechanical stimuli after plantar incision. The present studies examined the response characteristics of dorsal horn neurons receiving input from the plantar aspect of the foot before and after a plantar incision placed adjacent to the low threshold area of the receptive field (RF). MethodsIndividual dorsal horn neurons from the lumbar enlargement were antidromically identified and characterized as low threshold, wide dynamic range (WDR), and high threshold (HT) based on their responses to brush and pinch. Thresholds (in millinewtons), the pinch RF, and stimulus–response functions (SRFs) to von Frey filaments characterized the neurons. SRFs were analyzed using area under the curve. Changes in background activity, punctate mechanical thresholds, SRFs, and RF were recorded after an incision was made adjacent to the most sensitive area of the RF. ResultsIn all cells, an incision increased background activity; this remained elevated in 3 of 9 HT and 16 of 28 WDR neurons 1 h later. The SRFs were enhanced in 10 of 27 WDR neurons and in 2 of 8 HT cells after incision. Only the WDR neurons were responsive to filaments that produced withdrawal responses after incision in behavioral experiments. Increases in the RFs outside of the injured area occurred after incision in 15 of 29 WDR and 2 of 9 HT cells. ConclusionA plantar incision caused dorsal horn cell activation and central sensitization. Because the threshold of HT neurons did not decrease to the range of the withdrawal responses in behavioral experiments, particular WDR dorsal horn neurons likely contribute to the reduced withdrawal threshold observed in behavioral experiments. Both WDR and HT neurons are capable of transmitting enhanced responses to strong punctate mechanical stimuli after incision.

Monitoring and reversal strategies for new oral anticoagulants

Thrombin inhibitor dabigatran and factor Xa inhibitors rivaroxaban, apixaban and edoxaban form a new class of non-vitamin K antagonist oral anticoagulants and have been extensively studied in patients with venous thromboembolism and atrial fibrillation. They offer anticoagulation that is as effective and at least as safe compared to warfarin without the need for routine laboratory monitoring; however, no reversal strategies are currently validated in case of a non-vitamin K antagonist oral anticoagulant-associated bleed. In emergency situations, laboratory drug measurement and well-defined management for non-vitamin K antagonist oral anticoagulant-induced hemorrhage may improve clinical outcome. In this review, the merits and limitations of the routine coagulation tests and some of the more specific laboratory assays are compared. Furthermore, prohemostatic measures are reviewed and the recommended strategies in case of bleeding are summarized. Specific reversal agents are currently under development (idarucizumab for dabigatran, andexanet alfa for Xa inhibitors, and PER977 for both Xa- and thrombin inhibitors), which will facilitate clinical management of severe bleeding and emergency surgery.

Ein Konzept zur Verbesserung der postoperativen Schmerzbehandlung

ZusammenfassungDas Ziel dieser Arbeit bestand darin, mit den heute zur Verfügung stehenden Möglichkeiten eine praktikable, effektive, sichere, kostengünstige Akutschmerztherapie auszuarbeiten. Dazu wurden verschiedene Prinzipien zugrunde gelegt: Kontinuierliche Überwachung des Patienten während des gesamten Krankenhausaufenthalts, Einführung eines einfachen vier Punkte Scores zur Erfassung und Dokumentation des Schmerzes, Einführung eines Sedierungsscores, Anwendung der balancierten Analgesie und der „pre-emptive analgesia“, bedarfsorientierte Verabreichung von Medikamenten sowie das Übertragen einer wesentlich höheren Verantwortung und Befugnis für die Schmerztherapie auf die Pflegekräfte. Diese Prinzipien fanden ihren Niederschlag in Plänen und Algorithmen, die es den Pflegekräften und den Anästhesisten erlauben, die oben genannten Gedanken in die Tat umzusetzen. Abschließend wird die Verbesserung der Schmerzbehandlung mit einer Studie dokumentiert.AbstractMany articles in the literature document the fact that postoperative pain therapy has not improved for decades despite new insights into pain physiology, the availability of powerful analgesics and the development of new techniques. This project was set up to develop practical, effective, safe, and easy to run acute pain therapy. Methods. Postoperative pain management had to be optimized according to the facilities available today. Therefore, the legal background is presented first. Second, several medical and organizational principles were chosen to serve as a basis for the new organizational structure:– Continuously monitoring the patients pain during the whole stay in hospital– Introduction of a simple verbal 4-point pain score for determination and documentation of pain allowing the nurses to differentiate pain that should be treated or not.– A simple sedation score– Use of „balanced analgesia“ and „pre-emptive analgesia“– Drug administration according to the needs of the patient– Partial transfer of the responsibility for pain treatment to nurses. Plans and algorithms were expanded to allow nurses and anaesthesiologists to reach the previously determined goals. Results. In a small study including 107 patients, it was demonstrated that the quality of pain treatment improved significantly. Furthermore, patients, nurses and physicians are much more content with the new pain treatment regimen. Discussion. The difficulties in realizing such a concept are described. The importance of thorough teaching is underlined in a nurse-based system. However, it is not yet clear whether this pain treatment has resulted in reduced morbidity, reduced mortality and a shortened hospital stay of the patients.

Risiken und Komplikationsmöglichkeiten der Periduralanästhesie

ZusammenfassungPostoperative neurologische Ausfälle bei Patienten, die eine Epiduralanästhesie erhalten haben, sind nicht notwendigerweise auch durch diese hervorgerufen. Zusammenfassend können neurologische Defizite nach Epiduralanästhesien in 3 Kategorien eingeteilt werden. Eine 1. Kategorie beinhaltet Ereignisse, die unabhängig von einer Epiduralanästhesie auftreten. Eine 2. Kategorie beinhaltet Nebenwirkungen wie Rückenschmerzen, Arachnoiditis und postspinale Kopfschmerzen, die ausschließlich durch das Regionalanästhesieverfahren hervorgerufen werden. Schließlich kann eine Epiduralanalgesie mit dazu beitragen, daß bei bestimmten vorbestehenden Erkrankungen Komplikationen auftreten, die durch die Anästhesie, eine Operation oder die Geburt eines Kindes mit ausgelöst wurden. Hierunter fallen einige sehr dramatische Folgen einer Nervenblockade, nämlich Epiduralabszesse, spinale Infarkte und spinale Hämatome. Obwohl diese Folgen extrem selten sind, führen sie jedoch häufig zu permanenten neurologischen Defiziten. In dieser Übersichtsarbeit soll über die aktuelle Literatur bezüglich der Komplikationsraten, ihrer Inzidenz sowie Pathophysiologie, Prävention, Diagnose, Krankheitsverlauf und Therapie berichtet werden.AbstractPostoperative neurological sequelae in patients that have received epidural anaesthesia are not necessarily caused by the epidural anaesthetic technique. As a whole, adverse neurological outcomes following epidural anaesthesia may be subdivided into 3 different ethiological categories. A first category involves events that are not at all caused by the epidural, but merely due to the interference of anaesthesia and/or surgery with a preexisting medical condition. A second category includes mishaps such as backache, arachnoiditis, and post-dural puncture headache that are solely due to the epidural anaesthesia. Finally, epidural anaesthesia may be a contributory factor in the development of post-anaesthetic complications attributable to a pre-existing medical condition that are triggered by anaesthesia, surgery or childbirth. These complications include some of the most dramatic sequelae of major neuraxial blockade, such as spinal epidural abscess, spinal infarction, and spinal hematoma. Although extremely rare, the latter complications often result in permanent major neurological deficits. The present manuscript is a review of the most recent, literature addressing post-anaesthetic sequelae, and will discuss their incidence, pathophysiology, clinical course, diagnosis, prevention, and treatment.

Labor pain relief using bupivacaine and sufentanil: Patient controlled epidural analgesia versus intermittent injections

OBJECTIVES To determine whether the use of patient-controlled epidural analgesia (PCEA) versus intermittent injections (CIT) resulted in local anesthetic dose reduction. STUDY DESIGN PCEA and CIT using a mixture of 0.125% bupivacaine with sufentanil 1 or 0.75 microgram/ml were compared in 60 and 195 parturients, respectively. Assessments included pain scores, local anesthetic consumption, degree of motor blockade, type of delivery and neonatal outcome. Statistical analysis was done using Students t test and Chi-squares. RESULTS PCEA and CIT provided effective analgesia during labor and delivery. A higher dose of opioid significantly reduced the use of local anesthetic solution in PCEA-patients. There was no difference in motor blockade, type of delivery and neonatal outcome. CONCLUSION Patient-controlled epidural analgesia is an effective, safe and acceptable alternative to conventional intermittent epidural injections for pain relief during labor and delivery.

Epidural and spinal anaesthesia in patients receiving anticoagulant therapy

Summary The use of locoregional anaesthesia in anticoagulated patients has been and still is a controversial subject. Numerous publications have commented upon such a combination. The expressed opinions range from a categorical refusal to a more liberal approach. This chapter does not aim to gather all the information on this subject, nor does it plan to give answers to all the questions that might arise when anaesthetizing an anticoagulated patient. However, we have tried to review existing information and confront this with recently published (and even unpublished) data. The first part is a brief discussion of the different anticoagulant drugs that the anaesthetist is most likely to be confronted with. The second section shows that many anticoagulated patients would benefit greatly from a major regional technique. In the following discussion, existing and newer case series of spinal haematoma complications after CNB are presented, while risk factors in the development of such a complication are discussed. Finally, general and also more specific remarks about the use of EA and SA in patients receiving anticoagulant therapy are made. It is concluded that an all-round solution does not exist. A good knowledge of the drugs used, the anaesthetic techniques, and a risk-benefit analysis for each patient should enable the anaesthetist to make better and safer decisions.