In sheep undergoing general anaesthesia does inclusion of medetomidine result in hypoxaemia?

Hypoxaemia develops in healthy adult female non-pregnant sheep following intravenous medetomidine administration as part of a general anaesthetic protocol. The quality of the evidence is weak; there are four experimental studies; three cross-over studies (Raekallio et al., 1998; Celly et al., 1999a; Raisis et al, 2021) and one study which was run in parallel with primary orthopaedic research (Kästner et al., 2001). All four studies varied as to their anaesthetic and ventilatory management of the sheep. Although the evidence shows that
hypoxaemia occurs following the intravenous administration of medetomidine in sheep in the peri-anaesthetic period, the severity and clinical consequences of this hypoxaemia are difficult to determine. This is due to the variation in protocols between the studies. The evidence suggests that when intravenous medetomidine is administered to healthy adult female non-pregnant sheep hypoxaemia (partial pressure of arterial oxygen [PaO2] < 80 mmHg/10 kPa when breathing room air or a statistically significant fall in PaO2 from baseline when breathing oxygen enriched gases) develops. The drug’s effects on PaO2 are
minimised by anaesthetic techniques such as the administration of supplemental oxygen, tracheal intubation, and adequate monitoring. Therefore, intravenous medetomidine could be used cautiously alongside appropriate anaesthetic management in healthy adult female non-pregnant sheep undergoing research procedures. However, medetomidine is not licensed in food-producing animals in the UK and adherence to relevant legislation in the country of use is advised.