Isoflurane-associated penile erection in two bats: a Savi’s pipistrelle (Hypsugo savii) and a Kuhl’s pipistrelle (Pipistrellus kuhlii)

This report describes two cases of persistent penile erection in vespertilionid bats (Hypsugo savii and Pipistrellus kuhlii) during anaesthesia with isoflurane. The bats, presenting with wing fractures, were anaesthetised setting the vaporiser at 5% isoflurane for induction and 2% for maintenance. Both subjects developed penile erection upon induction of anaesthesia, which persisted for the duration of the procedures, lasting approximately 20 minutes. The condition resolved spontaneously after isoflurane discontinuation in both cases. No complications were observed and recovery was uneventful. This phenomenon has been reported in other species and in human medicine, often linked to the use of drugs exhibiting vasodilating properties. However, the exact underlying mechanisms remain unclear. Isoflurane is widely used in bats since it has several advantages, including rapid induction of and recovery from anaesthesia. Sevoflurane, which shares similar benefits but has a less pungent odour, could be an alternative choice, and investigating a potential dose-dependent effect of this agent might provide valuable insights. This is particularly relevant given the possible role of the anaesthetic's smell as a psychogenic trigger for penile erection.