Anaesthesia in small rodents

The order Rodentia has more than 2000 species and these can be divided into the sub-orders Anomaluromorpha (springhares, rodents native to the semiarid steppes and dry savannas of Kenya and Tanzania as well as in southwestern Africa), Castorimorpha (beavers, pocket gophers, kangaroo rats and kangaroo mice), Hystricomorph or Caviomorpha (guinea pigs, chinchillas, degus), Myomorpha (mouse-like rodents to include mice, rats, hamsters and gerbils), and Sciuromorpha (squirrels and prairie dogs) (Bennett, 2022; Bennet and Lewis, 2022). This article will concentrate on anaesthesia in the smaller species seen commonly in general practice within the Myomorpha order such as mice, rats, hamsters, and gerbils.

Anaesthesia of these rodents is associated with a higher risk compared with anaesthesia of cats and dogs. This risk is a result of several anatomical and physiological characteristics in addition to the relatively short life span of these species (Richardson and Flecknell, 2009). Rodents are prone to hypothermia because of their high body surface area to volume ratio, the cooling effects of anaesthetic gases and reduced movement (Flecknell, 2009a). Rodents are also prone to hypoglycaemia because of their low glycogen reserves. A rodent's high metabolism means that drug metabolism and excretion are very fast, oxygen demands are very high, and central nervous system damage occurs within seconds of respiratory arrest (Hawkins and Pascoe, 2021a).