Refinement dell'Analgesia e dell'Anestesia negli Animali da Laboratorio

The intrinsic value of each laboratory animal requires skilled refinement procedures to minimize suffering, implementing fine sedation, analgesia and anaesthesia standards.The remarkable progress in anaesthetic techniques achieved after Directive 86/609/EEC, allowing for new dugs and better understanding of pain physiology, should be applied to the design and the execution of animal based experiments.The outcome of such new approach will reduce animal suffering, produce better experimental data and reassure public opinion.Setting higher anaesthetic/analgesic standards, while reducing mortality/morbidity losses, would not significantly increase the experiment costs or duration.We are now heading toward a deeper understanding of the physiologic mechanisms ruling awareness and cognition, enabling a broad manipulation of states of consciousness: Stress, fear and anxiety can be prevented or reduced by means of tranquillizers and anaesthetic agents.Laboratory animal anaesthesia, especially in smaller species, is still largely a “one drug” procedure, satisfying only part of the anaesthesia principles and none of “balanced anaesthesia”. Hypnotics such as Chloral Hydrate, Tribromoethanol (Avertin), Alfa-Chloralose and Urethane should not be used as the only means for producing general anaesthesia, but rather as chemical restraint agents. When loss of consciousness is necessary, anaesthesia duration and depth should be tailored for a specific experiment. Painful procedures should be implemented by pre-emptive and “multimodal analgesia”, allowing for the most effective pain prevention and treatment available.Any anaesthetic procedure should be followed by a reasonably prompt recovery, for patient safety and best experimental results.PAIN RELEVING STRATEGYA standard anaesthetic protocol should take into account:A. Pre anaesthetic medication;B. Anaesthetic induction;C. Anaesthesia maintenance and monitoring;D. Anaesthetic recovery;E. Post-operative analgesia.All of the above requisites are generally needed to perform major surgery, but non cruent procedures, even if stressful, may be correctly handled by satisfying only some of them.• Pre anaesthetic medication;The advantages of administering a pre-anaesthetic medication are:1. State of consciousness can be adjusted to the degree of stress, fear and anxiety of a specific procedure;2. Pain perception can be effectively reduced by implementing pre-emptive analgesia;3. Animal handling can be easier and more gentle;4. Physical restraint can be avoided/ minimized;5. Stressful procedures can be better endured;6. Cardiovascular (C. O.) and respiratory parameters can be normalized;7. Anaesthetic and additional CNS acting drug dosages are reduced;8. Preoperative monitoring and instrumentation can be easier and less stressful;9. Anaesthetic recovery can be more gradual and excitation free;10. Autonomic response can be prevented.When tailored for a specific experimental setup and for a specific animal model, pre-anaesthetic medication can satisfy all the needs of a minor procedure not requiring complete loss of consciousness.Since no drugs are available to meet with all the above listed requirements, pre-anaesthetic medication should be made of multiple substances to:1. prevent anxiety, fear and apprehension (tranquillizers);2. prevent pain by pre-emptive, multimodal analgesia (analgesics, local anaesthetics);3. prevent unwanted autonomic response.• Anaesthetic induction;Short lasting (< 30') minimally invasive procedures can be carried out, after pre-anaesthetic medication by the use of a single injectable anaesthetic agent, dosed to fulfil the needs of induction and of a time calculated maintenance.Thoracotomy and other artificial ventilation procedures would better be undertaken using inhalation agents.• Anaesthesia maintenance and monitoring;Long lasting (> 30') and artificial ventilation (TRACHEOTOMY) procedures should be maintained by inhalation anaesthesia, allowing for better anaesthetic depth control, reduced metabolic impact and time fitting anaesthesia duration. Such approach offers the advantage of ventilation, respiration and acid-base control allowing precise continuous, not expensive monitoring.TIVA or constant rate infusion anaesthesia fit the needs of larger species, where a vascular access is less critical, while multiple shots (boluses) i.p. (intra-peritoneal) or i.m. injections should be reserved only to smaller animals.A simplified anaesthetic record would be a useful tool for research as well as for retrospective studies.• Anaesthetic recovery;Recovery from general anaesthesia should be prompt, gradual and complete. Involuntary excitement should be prevented by adequate pre-anaesthetic medication and by a reliable anaesthetic technique.Inhalation and reversible anaesthetic agents allow for precise recovery timing. Unintentional prolonged anaesthesia and prolonged recovery is armful for the patient and for the aim of the experiment.• Post-operative analgesia.Postoperative pain depends on a precise multimodal analgesia strategy to be commenced before any painful procedure.Pre-emptive analgesia, based on multiple pain mechanisms, should become a mandatory requisite of any invasive procedure.NSAIDs, opioids, NMDA/AMPA receptors blocking drugs and local anaesthetics should wisely be combined acting on reception, transduction, transmission and perception of painful stimuli, to prevent any unnecessary suffering of the patient.Intratecal administration of local anaesthetics and/or systemic analgesics, where appropriate, should be encouraged.