IN-DEPTH: CONDITIONS AND MANAGEMENT OF THE PERIPARTUM MARE


mare will have to be monitored closely overnight to ensure she does not start foaling prematurely so it may be best avoided in an ambulatory setting. There is the disadvantage if this does occur that controlled drainage will be made more difficult. The mare’s tail is bandaged her perineum cleaned and Caslick’s suturing opened if necessary. The cervix is then treated to produce relaxation by ap- plying directly either 1 mg prostin E-2 (PGE-2 gel)a, 400–600 g misoprostol (PGE-1)b mixed in saline and sterile lubricant or hyoscine butylbromide (60 mg)c mixed with sterile lubricant. The cervix can be manually evaluated (after 30 min to a few hours, depending on the product used) for softening prior to induction of delivery. The cervix can be manually dilated further, but it is important not to over dilate the cervix thus compromising controlled drainage of fluid. If only partial drainage is desired, then cer- vical dilation should be avoided. Once the chorio- allantois can be palpated, transcervically, a sharp trocar (24–32F)d is used to carefully puncture the membrane. In the case of hydramnios, the amni- otic membrane will also have to be penetrated. A small-bore stomach tube or cuffed cathetere is placed in the fetal fluid compartment and fluid slowly siphoned off. The tube can be capped peri- odically to slow fluid removal, which should take at least 30 minutes but 1–2 hours is more ideal. The mare’s heart rate is monitored during the procedure and drainage can be reduced or stopped if she be- comes tachycardic or shows signs of potential col- lapse. Systemic support is provided, concurrently with fluid drainage, in the form of colloids (plasma, whole blood) or hypertonic saline followed by crys- talloid fluids. With careful drainage it may be un- necessary to treat the mare with fluid therapy; however, approximately 25% of the fluid volume re- moved generally has to be replaced. The fetal fluid is collected in buckets to allow approximate calcula- tion of the total volume of fluid removed. Samples of fluid can be submitted for laboratory analysis and microbial culture. When sufficient fluid has been drained and the


mare is stable, then assisted vaginal delivery can be undertaken to deliver the fetus. With hydropic conditions, the mare usually experiences uterine in- ertia due to the extreme stretching of the uterine musculature. The fetus is likely to suffer from po- sitional and postural abnormalities requiring inter- vention and assistance with delivery. Oxytocin (10–20 IU, IV) may be needed to encourage uterine contractions; however, uterine stretching with hy- drops can affect responsiveness to oxytocin (Mc- Gladdery, personal observation). Depending on the stage of gestation that the pregnancy termination is performed, the response to oxytocin can be reduced relative to that at full term when there is upregula- tion of oxytocin receptors and the mare’s uterus becomes very sensitive to even very low doses of oxytocin.20,21 Although the foal is likely to be rela- tively small, care is needed to ensure the mare’s


152 2019  Vol. 65  AAEP PROCEEDINGS


cervix is sufficiently dilated to avoid cervical tearing when delivering the fetus. In some cases, a con- trolled vaginal delivery under general anesthetic may be necessary to deliver the fetus. Undergoing a general anesthetic when the mare is at risk of circulatory collapse is clearly not ideal. Most mares will retain their fetal membranes after deliv- ery, and this condition will need to be managed carefully to avoid the risk of toxic metritis-laminitis syndrome. Medication with broad-spectrum anti- biotics, anti-inflammatory agents, and oxytocin is likely to be necessary. Some mares experience varying degrees of colic following delivery, possibly due to the creation of a large amount of space within the abdominal cavity following removal of the huge volume of fluid and large-bowel repositioning. De- spite the potential for problems, mare survival is normally very good. The incidence of recurrence in a subsequent pregnancy is low although, the author does have experience of one mare that had hydrops amnion on 3 separate occasions. If the hydrops mare presents in late pregnancy (within 2–4 weeks of full term) some clinicians have attempted partial fluid drainage to reduce the vol- ume of fetal fluids thus lessening the risks to the mare while also salvaging the pregnancy. The mare is carefully monitored and managed until de- livery with the hope that the foal may have reached sufficient maturity by the time of delivery so that it will be able to survive.22 If partial fluid drainage is chosen, the procedure is


very similar to that described for fluid drainage prior to pregnancy termination. Following partial fluid removal, administration of broad-spectrum an- timicrobials to mares is prudent to combat infection that may be introduced during drainage, particu- larly because the cervical plug is compromised with the procedure. Treatment with non-steroidal anti- inflammatory drugs, either flunixin meglumine or firocoxib, and double-dose altrenogest (0.044–0.088 mg/kg PO q24h) to maintain uterine quiescence and modify the inflammatory response is necessary. This study reported no success in treating 10 mares, who were 2–4 weeks from full term, with partial drainage from the allantoic compartment and all delivered nonviable foals. The authors suggested fetal demise was most likely from iatrogenic fetopla- cental infection and fetal asphyxia due to associated placental separation.22 In any mare that appears imminently at risk of rupturing her prepubic tendon or suffering a severe abdominal wall rupture, the best option may be to terminate the pregnancy rather than risk the mare’s future usefulness as a broodmare. The mare’s ability to carry a future foal and deliver normally again would be highly questionable and resorting to embryo transfer or other assisted reproduction techniques might be the only option available if the relevant breed regulations allowed. However, pregnancy management can be successful.23 This study reported on managing 13 pregnant mares


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