Oxygen delivery by mask improves the PaO(2) of pregnant ewes during short term anaesthesia for caesarean delivery of preterm lambs

The aim of this study was to determine if oxygen supplementation improved the PaO(2) of pregnant ewes during short anaesthesia, when compared to a previous study where oxygen was not provided (Musk and Kemp, 2018). Twenty-six pregnant Merino cross ewes at 121–123 days of gestation were anaesthetised with intravenous midazolam and ketamine for subarachnoid administration of 60 mg of lignocaine and caesarean delivery of the preterm lamb. 100% oxygen was administered to the ewe by a face mask. Arterial blood samples were collected from the ewe immediately after delivery of the foetus. The ewes weighed 60.7 ± 5.5 kg and received 0.51 (0.47–0.58) mg/kg of midazolam and 10.3 (9.4–11.6) mg/kg of ketamine intravenously. The PaO(2) of ewes receiving oxygen by face mask was higher than previously reported [92.6 ± 44.0 mmHg compared to 45.2 ± 11.8 mmHg (Musk and Kemp, 2018) (p = 0.0007)]. Oxygen delivery by mask improved the PaO(2) of pregnant ewes during short term anaesthesia.