Anesthesia for Research on Reconstructive Facial Surgery in Rats

Anesthesia for maxillofacial surgery requires as specialized a technique in rats as in humans because the surgical site is close to the airway. However, no reports can be found that provide a detailed description of effective anesthesia in rats. This study describes an anesthesia technique for the maxillofacial region. Intraperitoneal anesthesia with pentobarbital is the most common type of anesthesia for rats.[1] However, this procedure frequently causes hyperalgesia and postoperative death, and it does not allow a lengthy operation such as reconstructive surgery. Inhalation anesthesia using isoflurane with an inhalation device would be the safest anesthesia procedure for rats. However, it is not possible to use this device for surgery on the oral and maxillofacial region, as the anesthesia connector covers the entire face of the rat. Therefore, a simple nasal mask is required. This study attempted to make a nasal mask from a 50-mm balloon (internal diameter: 15 mm), 40 mm of plastic tubing cut from a conical 15-mL tube (17 × 120 mm, BD Biosciences, Bedford, Massachusetts, USA), and adhesive plastic tape ([Fig. 1]). The mask was connected to an anesthesia device (Univentor 400 Anesthesia Unit, Univentor, Malta) and covered only the nose and maxillary incisors of rats.[2]

Fig. 1 Photograph of rat maxillofacial surgery with a small-size nasal mask fitted to the rat nose and maxillary incisors. IAU, inhalation anesthesia unit.

For easy handling of the rat, presedation was performed by placing the rat in a desiccator (internal diameter: 245 mm; height 296 mm) (ASONE, Osaka, Japan) with a sheet of filter paper impregnated with isoflurane (Forane, Abbott, Tokyo, Japan). After confirming sedation by gently shaking the desiccator, the rat was transferred to the operating bench, and the nasal mask connected to the inhalation device was placed over the rat's nose. Inhalation anesthesia with isoflurane was performed at an airflow of 600 mL/min. The concentrations of isoflurane during the induction and maintenance phases were 4% and 2 to 3%, respectively. Approximately 4% isoflurane was used during the first induction phase until reduction of respiratory frequency and loss of blink reflex were observed. The concentration was reduced to 2 to 3% during the maintenance phase, at which time the operation was started ([Fig. 1]). However, during the induction and after changing the empty anesthesia bottle, overdoses of the anesthetic agent sometimes caused apnea in the rat. When apnea was observed, the nasal mask was removed from the nose; the rat was shifted from the prone position to the supine position; and the tongue was retracted to prevent airway obstruction. A rubber bulb used as a pipette (internal diameter: 7 mm) was then placed over the nose and compressed at a rate of 30 times per min until spontaneous breathing was recovered ([Fig. 2]). If cardiac arrest accompanied apnea, cardiac massage of the rat chest was also performed by manual bag ventilation.[3]

Fig. 2 Cardiopulmonary resuscitation using a rubber bulb as a pipette to treat anesthesia-induced apnea in the rat.

The anesthesia techniques described above facilitated the performance of facial nerve surgery,[4] [5] oral mucous correction and transplantation, periodontal surgery, and cranial surgery in rats. Moreover, this technique allowed reconstructive facial nerve surgery with a duration of approximately 400 minutes. The method demonstrated by our study contributes to the progress of maxillofacial surgical research in rats.

• References

• 1 Shen ZL, Lassner F, Becker M, Walter GF, Bader A, Berger A. Viability of cultured nerve grafts: An assessment of proliferation of Schwann cells and fibroblasts. Microsurgery 1999; 19: 356-363
• 2 Sasaki R, Yamato M, Aoki S , et al. Rat nasal mask for oral and maxillofacial surgical research. Tech Talk 2008; 13: 2
• 3 Sasaki R, Yamato M, Sekine H , et al. Ambu-bag for the treatment of anesthesia-induced apnea in experimental rat. Tech Talk 2008; 13: 1-2
• 4 Sasaki R, Aoki S, Yamato M , et al. Tubulation with dental pulp cells promotes facial nerve regeneration in rats. Tissue Eng Part A 2008; 14: 1141-1147
• 5 Sasaki R, Aoki S, Yamato M , et al. PLGA artificial nerve conduits with dental pulp cells promote facial nerve regeneration. J Tissue Eng Regen Med 2011; 5: 823-830