Although many mares with RFM do not become clinically ill, early prophylactic intervention is widely practiced because the complications associated with RFM may be severe and potentially life threatening. Many farm managers and horse owners with a veterinary client-patient relationship may be instructed to begin intramuscular (IM) injections of oxytocin 2 to 4 hours postpartum if the fetal membranes have not been passed. The membranes should be tied up above the hocks to prevent soiling and tearing. Tying a weight (e.g., a brick) to the membranes is not recommended because it may predispose the mare to development of a uterine horn intussusception. Injections of oxytocin should be given every hour for at least 6 treatments. The half-life of oxytocin in the mare is brief (12 min).
The initial starting dose of oxytocin should be on the low side (10-20IU/500 kg) because sensitivity to oxytocin varies widely. The dose of oxytocin can then be tailored to each individual mare. A positive response will result in passage of uterine fluid from the vagina. Mares should be monitored following injection because any obvious cramping will begin within 10 minutes of IM injection. If a 10- to 20-IU oxytocin treatment does not result in an outward manifestation of discomfort by the mare, such as sweating and restlessness, then the dose can be increased in 10- to 20-IU increments until an effect is noticed. The dose should only be high enough to elicit mild colic signs. Mares with uterine inertia because of dystocia may be initially very resistant to the effect of oxytocin and may become more sensitive in the subsequent hours. If cramping and rolling result then the dose should be reduced. Some mares become inattentive mothers during the time when they are distracted by RFM or uncomfortable from the oxytocin-induced cramping. Thus the foal should be kept in a safe place when the mare is in pain. Nursing should be encouraged to stimulate the natural release of oxytocin associated with milk letdown.
If the mare fails to respond to six oxytocin injections or if she is clinically ill, a thorough veterinary examination is indicated. One option is to start an intravenous (IV) drip of oxytocin at 0.1 IU/ml of saline (i.e., 100 IU oxytocin per 1 L saline). The IV flow rate should be set so that the mare has visible signs of contractions every S to 10 minutes. The oxytocin drip treatment protocol will, in effect, revert the mare back into labor for about 1 hour.
The technique described by Burns and colleagues () works best when the membranes are fresh. Some clinicians perform the procedure prophylacti-cally after a dystocia to reduce the likelihood of membrane retention. The clinician should wear waterproof clothing and a sterile surgical glove over a clean rectal sleeve. The perineum of the mare and external portion of the membranes are washed thoroughly. The opening at the cervical star, which leads into the allantoic cavity, is identified. A clean large-bore stomach tube is introduced, and the membranes are gathered around the tube. In addition, 4 L or more of a warm 1% povidone iodine solution is pumped or gravity fed into the chorioallantois until the fluid overflows. The tube is withdrawn as the RFM are tied shut with umbilical tape. Oxytocin may then be administered so that the uterus contracts against the distended membranes. This technique distends the endometrial crypts and often permits release of the microcotyledons. If the procedure is unsuccessful then it may be repeated several hours later. However, the retained membranes soon become autolytic and tend to tear as soon as distention starts.
If partial retention of the membranes is diagnosed, or if the membranes are badly torn, the uterus may be distended with 1% povidone iodine solution as described previously. The fluid distention and uterine contractions may help loosen the membranes. If the piece of membrane can be reached, it may be gently teased off the en-dometrium and removed. However, if the membrane tag is firmly adhered then continued traction is contraindicated. Once or twice daily flushing and the process of au-tolysis will eventually loosen the membranes. This procedure also may be carefully performed in mares that retain the membranes after a cesarean section. However, it is important to use a lower volume of infusate so that the uterine closure and fibrin seal are not disrupted.
Toxemic mares that are clinically ill and are passing a fetid uterine discharge may require systemic support with IV fluids, frequent IV treatments with oxytocin, and twice daily high-volume uterine lavage. Gentle manual removal of the fetid membranes may be necessary in these mares. Back and forth uterine lavage is performed with a clean stomach tube, bilge, or stomach pump. A dilute (1%) povidone iodine solution or sterile fluids are used to remove bacteria and inflammatory debris from the uterus. The clinician should hold the end of the tube cupped in the hand within the uterine cavity to prevent the tube from forcefully sucking against the wall when the fluid is being siphoned back. During the first few lavage procedures, persistence and patience in obtaining a clean return from the uterus is often rewarded with rapid clinical improvement and uterine involution. Lavage should be repeated once or twice daily until all debris is removed, the lavage is clear, and the uterus is well involuted.
Prophylactic administration of antibiotic and antiinflammatory medication is often prescribed early in the course of RFM in an attempt to prevent complications. Common antimicrobial choices are trimethoprim sulfa (30 mg/kg, q24h PO), or procaine penicillin G (22,000 IU/kg ql2h IM) for a minimum of 3 to 5 days. If the mare is systemically ill then broad-spectrum medications such as penicillin-aminoglycoside combinations are recommended. The formulations or derivatives of penicillin include the following: procaine penicillin (22,000 IU/kg ql2h IM), sodium and potassium penicillin (22,000 IU/kg q6h IV), ampicillin (50 mg/kg q8h IV), or ticarcillin (44 mg/kg q8h IM) for resistant cases. Aminoglycosides such as gentamicin (6 mg/kg q24h IM or IV) or amikacin (6.6 mg/kg ql2h IV or IM) are used for mixed and gram-negative infections or resistant cases. Appropriate antibiotic use is confirmed by uterine culture and sensitivity results.
The mostly commonly used antiinflammatory medication for endotoxemic mares is flunixin meglumine, 1.1 mg/kg IV. In milder cases, flunixin meglumine (0.25-0.5 mg/kg q8h IV), ketoprofen (2 mg/kg ql2h IV), vedaprofen (2 mg/kg ql2h PO), or phenylbutazone (4 mg/kg IV or PO) are used. Hyperimmune plasma is administered if it is available.
Laminitis in mares with RFM is a serious complication. Lateral radiographs of the distal phalanx will help establish the degree of rotation, and the prognosis. Symptomatic care such as hosing the hooves with cold water, or application of foam pads or special shoes to the hooves can provide extra support and promote comfort. Phenylbutazone at 2 g every 24 hours by mouth is sometimes used prophylactically.
Mares with lactation failure should be treated with domperidone at 1.1 mg/kg orally every 12 hours to encourage lactation.