The effects of CT1341, thiopentone and induction- delivery time on the blood gas and acid-base status of lambs delivered by casesarean operation and on the onset of respiration.

Caesarean sections were performed on 18 Romney ewes on day 144 of pregnancy. Anaesthesia was induced in 9 ewes with CT 1341 and in 9 ewes with thiopentone and maintained in both groups with halothane administered with oxygen. Surgery was performed with the ewes in lateral recumbency, with respiration unassisted. Blood samples were collected from the intact umbilical artery at the time of delivery and analysed for PO2, PCO2, pH (base deficit was derived). The intervals between ewe induction and lamb delivery (lD), delivery and the onset of breathing (TSR), and delivery and the lamb standing were recorded. Lambs in the CT 1341 group both breathed and stood sooner than lambs in the thiopentone group. Significant linear relationships were only found in the CT 1341 group between TSR interval and PCO2 and pH. No significant correlations were found between the lD interval and any of the biochemical characteristics. The results of this study suggest that lateral recumbency does not interfere with uteroplacental circulation, that CT 1341 (2.2 mg/kg) is associated with less neonatal depression than thiopentone (10 mg/kg) and that severe neonatal hypercarbia may delay the onset of respiration in lambs with minimal drug depression.