[Laboratory animal anaesthesia: influence of anaesthetic protocols on experimental models]

The use of experimental animals requires anaesthesia to provide immobility and analgesia. Animals require anaesthesia not only for ethical reasons but also because pain and stress can alter the quality of research results. Recognition of pain, and its treatment is important throughout the procedure. Before anaesthesia, animals are acclimated and rehydrated. Except in small rodents and in ruminants, in order to avoid vomiting, a fast of 8 to 12 hours before anaesthesia is recommended. In order to protect animals against suffering and distress during transfer, restraint and management, a premedication is administered. Most human anaesthetic products can be used in animals. There are some specific veterinary anaesthetics. Moreover, the anaesthetic effects could be different from specie to an other. In most big animals, induction is realized by intravenous administration. In small rodents, venous puncture and contention could be difficult, and anaesthetic agents may be injected via intraperitoneal or intramuscular way. The principal inconvenient of these administration routes is the impossibility to adjust dose to animal response. In large animals, human anaesthesia material can be used. Some technical adaptations could be necessary in smaller animals. In rodents or in neonatology, specific devices are recommended. ECG, arterial pressure, tidal volume, expired CO(2) and oxygen saturation monitoring assess quality of, and tolerance to anaesthesia. If animals are awaked after anaesthesia, postoperative management is closed to human clinical problems. During animal experimentations, anaesthesia may interact with results. All anaesthetic drugs alter normal physiology in some way and may confound physiologic results. In the literature, most publications do not mention this possible interaction. Investigators need to understand how animals are affected by anaesthetic drugs in order to formulate anaesthetic protocols with minimal effects on data. Extrapolation between different animal species and human and animals about the effects of anaesthetic agents are very hazardous. Great differences exist between the effects observed in vitro and in whole animals. The effects of the anaesthetics could be totally different if they are used alone or in association. The same anaesthetic could have opposite effects from an organ to another. For results validation, the anaesthesia side effects (hypoventilation, hypotension, cooling em leader ) have to be minimized. All new experimental models should require discussing the possible interferences between anaesthesia and results and to compare results obtained with different anaesthetic protocols.