The successful use of fentanyl/fluanisone ('Hypnorm') as an anaesthetic for intracranial surgery in neonatal rats

This study reports on the successful use of fentanyl citrate and fluanisone ('Hypnorm') anaesthesia for intracranial surgery in neonatal (7-day-old) rats. Provided the anaesthetic was administered subcutaneously, the animals showed a very high survival rate in the short term (81/85, 95%) and showed no ill effects in the long term. The depth of anaesthesia was sufficient to allow the operation to be carried out without the animal reacting to any painful stimuli. However, the animals did make random movements during the period of surgical anaesthesia which were not related to any painful stimuli. Although these movements did not interfere with the surgery performed here, such movements would interfere with operations requiring greater precision, such as the localized micro-injection of neural tracers.