Abstract
Effective outcomes in surgical research using experimental animals are dependent on anaesthetic techniques.1,2 For operations with minimal operative stress, such as intraoral punch biopsy in minipigs, we generally perform the operation under deep sedation using intramuscular injection of a combination of medetomidine (120 μg/kg) and ketamine (10 mg/kg), because it is easier than applying general anaesthesia. However, it is difficult to control anaesthetic depth using this procedure alone. It causes hyperalgesia and perioperative awakening. These problems delay research progress. Therefore, we made a simple and temporary anaesthesia device for use under deep sedation in the pig. This device was made up of a 500 mL beaker (Iwaki Pyrex®, Asahi Techno Glass, Tokyo, Japan), three gauzes (30 × 30 cm) and a cut-off surgical glove; 5 mL of sevoflurane (sevofrane®, Abbott, Tokyo, Japan) was then added to this device (Figure 1). The device covered the pig maxilla, nose and mandible. The inhalation anesthethic agent did not leak because it was fitted to the animal's nose using the surgical glove (Figure 2). When there is insufficient muscular relaxation under deep sedation using medetomidine and ketamine, for example when a blink is recognized, we use this temporary inhalation anaesthesia. Thus, when the blink reflex disappears and the respiratory frequency is reduced, we stop this temporary anaesthesia and the anaesthesia device is wrapped with aluminium foil to prevent further escape of the volatile sevoflurane. Sevoflurane has a non-pungent odour and causes minimal irritation of the airway and eyes. It has a low blood/gas partition coefficient of 0.63, and it can be used to perform rapid induction of anaesthesia and recovery. We are able to use this procedure to perform an oral mucous membrane biopsy. Since we have been using this method, our experimental minipigs have shown almost no sensitivity to pain or perioperative awakening. Our temporary inhalation anaesthesia device will contribute to the progress of surgical research in pigs.
Temporary inhalation anaesthesia device
(A) Using the temporary inhalation anaesthesia to perform an oral mucosal biopsy in a minipig. (B) The device is closely fitted to the nose by the rubber of the surgical glove (arrows)