Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa.
Reprod Domest Anim. 2020 Jul;55 Suppl 2:38-48. doi: 10.1111/rda.13669. Epub 2020 May 6.
Elective caesarean section (CS) is the safest means of delivering the litter in bitches in specific situations. Timeously performing elective pre-parturient CSs at a fixed time would be convenient and prevent emergency CSs and foetal demise. This review proposes a method of performing elective pre-parturient CSs which is safe for both the bitch and puppies. Brachycephaly, small litters and large litters, preceding litter delivered by CS and trial of labour after a preceding CS are identified as factors increasing the need for CS whereas emergency CS is identified as factor increasing foetal demise. The first day of cytological dioestrus more precisely predicts the day of onset of spontaneous parturition than the first day of the LH surge or the dates during oestrus on which progesterone (P4) first exceeds 6 nM or 16 nM. Foetal biparietal diameter at the time of onset of spontaneous parturition varies too much to accurately predict readiness for CS. During the last few days of gestation, P4 with cut-off concentrations at 15.8, 8.7 and 3.18 nM, but not plasma cortisol concentrations, hold promise as predictors of onset of parturition and when to perform pre-parturient CSs. A protocol associating medetomidine hydrochloride as premedicant with propofol as induction agent and sevoflurane as maintenance is safe for scheduled CS and yields good maternal and puppy survival rates at delivery, 2 hr and 7 days after CSs. Clinicians have to pay attention to the haematocrit of bitches at the time of cervical dilatation which is at the lower end of the normal reference ranges for non-pregnant dogs and to the decline in haematocrit during CS (as a proxy for blood loss) which is approximately 7% for both parturient (open cervix) and pre-parturient (closed cervix) CSs. Pre-parturient CSs can be scheduled and performed 57 days after onset of cytological dioestrus with puppy survival rates of 99%. Collectively, these studies provide a protocol to safely perform elective CSs in a large proportion of the obstetric population at a convenient time of the day but more research is required with larger numbers to establish whether this practice is routinely safe and safe in all breeds.
择期剖宫产（CS）是在特定情况下为犬只分娩的最安全方式。在固定时间及时进行择期产前 CS 将方便且可预防紧急 CS 和胎儿死亡。本综述提出了一种对母犬和幼犬均安全的择期产前 CS 方法。短头型、小胎数和大胎数、之前通过 CS 分娩的胎数以及之前 CS 后试产被确定为增加 CS 需求的因素，而紧急 CS 被确定为增加胎儿死亡的因素。细胞学发情期的第一天比 LH 峰的第一天或发情期间孕酮（P4）首次超过 6 nM 或 16 nM 的日期更准确地预测自发分娩的开始日期。自发分娩开始时的胎儿双顶骨直径变化太大，无法准确预测 CS 的准备情况。在妊娠的最后几天，P4 的截止浓度为 15.8、8.7 和 3.18 nM，但血浆皮质醇浓度除外，有望成为预测分娩开始和进行产前 CS 的指标。将盐酸右美托咪定作为术前用药与丙泊酚作为诱导剂和七氟醚作为维持剂联合使用的方案用于计划 CS 是安全的，并且在 CS 后 2 小时和 7 天，母犬和幼犬的存活率均较高。临床医生必须注意在宫颈扩张时母犬的红细胞压积，此时处于未怀孕犬的正常参考范围的低端，以及在 CS 期间红细胞压积下降（作为失血的替代指标），无论是分娩（宫颈张开）还是产前（宫颈闭合）CS，下降约 7%。可以在细胞学发情期开始后 57 天安排并进行产前 CS，幼犬存活率为 99%。总的来说，这些研究提供了一种在一天中的方便时间安全地对大部分产科人群进行择期 CS 的方案，但需要更多的研究来确定这种做法是否在更大数量的犬种中常规安全。
