Simple Summary Anaemia during pregnancy is commonly reported in humans and is considered a significant health issue as it is associated with adverse neonatal outcomes including low birth weight, preterm birth and possible perinatal mortality. Pregnant sheep are a common model for research investigating the causes and consequences of preterm birth, but the incidence and significance of anaemia during pregnancy is not known. However, intraoperative anaemia in pregnant sheep has been reported previously. In addition, it has been demonstrated that the cause of intraoperative anaemia is not pregnancy alone as pregnant sheep in a farm environment did not develop anaemia. The aim of this study was to document the red blood cell and protein content of maternal blood before, during and after anaesthesia and surgery to elucidate the cause and duration of intraoperative anaemia in pregnant sheep in a research context. The concentration of red blood cells and protein decreased during anaesthesia and were attributed to the use of anaesthetic drugs and fluids as opposed to the pregnancy status of the sheep.
Abstract The aim of this study was to document the packed cell volume (PCV), haemoglobin concentration and total protein concentration of maternal blood before, during and after anaesthesia. Six singleton Merino-cross pregnant ewes at 116-117 days of gestation were premedicated with intramuscular acepromazine (0.02 mg/kg) and buprenorphine (0.01 mg/kg), and anaesthesia was induced with intravenous midazolam and ketamine. Anaesthesia was maintained with isoflurane in 100% oxygen. Serial blood samples were collected the day before anaesthesia (baseline), immediately prior to induction of anaesthesia (pre-op), at the end of the procedure (intra-op) and the following day (post-op). There was a significant change in the PCV during the study (p = 0.003) with an initial decrease of 12.5% from the baseline (0.36 (0.36-0.4) to 0.315 (0.29-0.34), p = 0.044), a further intraoperative decrease of 41.7% from the baseline (0.21 (0.195-0.245), p = 0.002) and an increase the day afterwards (0.3 (0.285-0.35), p > 0.99 compared with baseline). The haemoglobin concentration also changed (p <0.0001) (baseline: 114 (111.8-123); pre-op: 97 (77.25-104.5), 14.9% decrease, p = 0.022; intra-op: 70 (61.5-83.25), 38.5% decrease, p = 0.0009; post-op: 101.5 (96.25-114) g/L, p > 0.99). Likewise the change in total protein during the study was significant (p = 0.0003) and decreased from the baseline [70 (67.25-70.75) g/L] prior to anaesthesia (61 (58.25-64.5) g/L, 12.9% decrease, p = 0.0437) and further during anaesthesia (55.5 (53.75-63.25) g/L, 20.7% decrease, p = 0.0021) with an increase [63 (61.25-67) g/L, p > 0.99] on the first post-op day. In conclusion, intraoperative anaemia and hypoproteinaemia occurred in this study. These alterations are attributed to a combination of the side effects of acepromazine and haemodilution.