IN-DEPTH: CONDITIONS AND MANAGEMENT OF THE PERIPARTUM MARE


ment or attempts to stand during examination and treatment can be hazardous. The perineal area is cleansed and digital transvaginal examination is performed to allow the veterinarian to determine the degree of fetal membrane attachment to the endometrium. Most often, the gravid horn is de- tached and free within the uterus while the non- gravid horn remains attached to the endometrium. With a scissor-like action, two fingers are used to bluntly “dissect” the most caudally attached portion of the chorioallantois from the endometrium (uter- ine body and base of one or both horns). With the base of the horns free from the endometrium, the membranes of the attached horn are encircled using the thumb and forefinger. This “ring” of fingers are used in a gentle manner to move cranially up and back on the attached membranes to evenly separate the chorioallantois from the endometrium. Con- trolled pressure and digital separation are repeat- edly applied in a cranial direction toward the tip of the uterine horn. The veterinarian’s external hand should be used to relieve tension from the weight of the attached membranes to reduce the probability of membrane tearing or uterine horn eversion. If membranes do not detach readily from the endome- trium or excessive haemorrhage is noted, the proce- dure should be discontinued. Another, novel technique for actively removing


fetal membranes involves catheterization of an ex- posed umbilical vessel, infusion of water and disten- sion of membrane vasculature, which promotes detachment of the chorioallantois.22 This proce- dure leads to stretching of the umbilical vessels, degeneration of the epithelial cells due to osmotic swelling, and subsequent detachment of the mi- crovilli.23 The result is a rapid but gentle separa- tion of the fetal membranes from the endometrium. The technique is utilized after initial oxytocin ther- apy fails to result in release of retained membranes. Minimal equipment is necessary to perform the pro- cedure: a stallion catheter or foal nasogastric tube (7 mm diameter), garden hose adapter with a flow control valve, and a garden hose. Mares should be adequately restrained in stocks or in a box stall with sedation when necessary. The perineal area should be cleansed prior to the procedure and oxy- tocin (10–20 IU IM) administered immediately be- fore catheterization of the umbilical vasculature. An umbilical vessel (artery or vein) is longitudinally incised with a scalpel blade to expose the vascular lumen. The catheter, attached to the garden hose via the flow control adapter, is advanced cranially through the incision until resistance is met. Low- pressure water flow initiated and the catheter is advanced further, when possible. A variation of the technique utilizes a spray pump adapted for water infusion when a garden hose or clean water source are not available. An average of 7–8 L wa- ter is required to obtain complete stretching and swelling of the membranes.23 The veterinarian holds the tube in situ and adjusts water flow while


monitoring the clinical response and physical reac- tions of the mare. It is necessary to keep the water pressure low to reduce damage to the proximal blood vessels that are essential for infusing as much of the chorioallantois as possible. Some mares show signs of mild discomfort, and fluid flow should be slowed or discontinued allowing the mare to relax and the progress of membrane release to be as- sessed. Gentle traction is often placed on the mem- branes at the level of the mare’s vulva to assist in expulsion. In most cases, retained fetal mem- branes are expulsed within 10–15 minutes of umbil- ical vasculature infusion. However, the process takes slightly longer in somemares. When separa- tion does not occur in 30 minutes time, other treat- ment options should be considered.23 Incomplete separation, failure of the membranes


to release, and tearing of membranes during the umbilical infusion are complications of the process. The incidence of failure rate or tearing was higher in mares that retained membranes for longer than 12 hours postpartum.23 Some mares also experi- ence mild discomfort during the procedure, which is remedied by discontinuing infusion until the mare is more comfortable. Overall, umbilical vessel in- fusion is an easy technique to perform to aid in removing retained fetal membranes. The proce- dure is performed after oxytocin therapy has been unsuccessful in promoting membrane expulsion. In most cases, umbilical vessel infusion provides a good outcome with few side effects. While the pro- cedure works best within 8–12 hours of foaling, the low investment of time and resources makes it a good method for early intervention in all cases of retained fetal membranes. There are an abundant number of methods for removing retained fetal membranes in mares. In- terestingly, a survey of veterinarians (54% repro- duction specialists) found that most treatments for retained fetal membranes reported by the practitioners reflect a lack of specific treatment guidelines and management recommendations.24 Oxytocin therapy is commonly used with dose ranges between 10 and 20 IU administered intrave- nously or intramuscularly as often as 30-minute to 2-hour intervals. Calcium was only administered alongside oxytocin in 3/102 respondents. Traction and manual removal were attempted by 30% of practitioners; the Burn’s technique was utilized by 25% of practitioners surveyed. More than half of the respondents relied on a previously used tech- nique. Large-volume lavage was the most common treatment used by more than half of the survey responders. Large-volume lavage is used to re- move intrauterine fluid accumulations of inflamma- tion, debris, and bacteria. Much like the Burn’s technique, the mare’s perineum is cleaned and a sterile stomach tube is introduced through the cer- vix and into the uterus. Six to 12 L of warm, iso- tonic fluid (0.9% NaCl, lactated Ringer’s solution, or 1% providone-iodine solution (antiseptic) is infused


AAEP PROCEEDINGS  Vol. 65  2019 161


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