Dystocia Management Factors for Neonatal Viability

The goal is maximum cleanliness and minor trauma to the mare (to prevent subsequent fertility problems), combined with a system for rapid correction of the dystocia or immediate referral to an experienced team if close by. Foal survival is linked to duration of time to correct the dystocia. 15 min longer duration makes a difference in number of live foals. One study showed that less than 50% of dystocias have live foals [1].
Editor's Comment - A new technique using garden hose running water inserted into the placenta to distend the uterus and create room for manipulation has been described.

I. History

1. Duration of the time since abdominal cramping or rupture of membranes occurred.
2. Determine what intervention has occurred and when.
3. Reproductive history of the mare: previous dystocia, cervicovaginitis, twins, gestational age, medication administered.
4. If 10 minutes have elapsed after breaking water and strong abdominal contractions produce no evidence of a nose and forefeet, have qualified help assess position by vaginal exam. If feet and nose are present, allow an additional 10 minutes of labor. If 20 minutes have elapsed, have owner walk mare until veterinarian arrives.

II. Determine Cause

1. Abnormal presentation, position, posture, presence of twins.
2. Incompatibility of fetal size and birth canal.
3. Uterine inertia or other maternal factors.

III. Make Plan for Correction and Set Time

1. If not making significant progress in 10-15 minutes, consider alternative approach, e.g. anesthesia or cesarean, etc.
2. Epidural Block

1. Used to prevent straining.
2. Administer 5-6 cc 2% carbocaine hydro-chloride, or 2% lidocaine, with 4-7 cm 18 gauge spinal needle at the junction of tail hairs and caudal folds of the tail.
3. Avoid larger volume because it may make the mare unstable in the rear quarters and complicate recovery if general anesthesia is subsequently required.

3. Twitch and/or leg tied up for restraint.
4. Proceed with caution because the risk to the veterinarian is high in these circumstances. Always attempt to protect yourself.
5. Drugs to calm the mare.

Editor's Comment - None of the drugs listed below will make it completely safe to work with the mare.

4. All drugs affect the fetus to a greater or lesser degree.
5. Xylazine (0.5-1.0 mg/kg) can cause sedation. Mares can arouse from xylazine and kick violently. Causes fetal bradycardia.
6. Xylazine (0.5-1.0 mg/kg) plus butorphanol (0.01-0.02 mg/kg).
7. Detomidine (5-10 mg/mare; 20 ug/kg IV) longer lasting -mare can still kick.

IV. Equipment

1. Resuscitation equipment should be available (See Resuscitation).
2. Obstetrical equipment consists of four chains (2 long, 2 short), nylon straps, two obstetrical handles, snare (calf snare or hog snare), Krey's hook, towel clamp (to grasp ear or skin), fetotome and wire, knife, sleeves, lubricant (mineral oil or methylcellulose), stomach pump and tube (to lubricate foal), stainless steel bucket.

V. Tocolysis

1. Agents that paralyze or reduce myometrium activity may be useful in preventing straining to repel fetus.
2. Clenbuterol hydrochloride (a Beta-2 sympathomimetic) administered at 0.4-0.5 ug/kg intra-muscularly may provide some benefit.

1. This drug delays parturition for 5-10 hours in cattle [3].
2. Limited use in the horse at this time.

VI. Anesthesia Consideration for Neonatal Viability

1. Intravenous xylazine (l mg/kg) and ketamine (2 mg/kg) anesthesia can produce short-term cessation of maternal straining and allow correction of many malposition problems with minimal fetal depression.

1. Used in conjunction with a hoist (block and tackle) to raise the rear quarters, (see Fig. 1).
2. If hoist is unavailable, a 3/4" thick plywood board, elevated at one end on a bale of straw, can elevate mare's rear quarters if sufficient help is present to place the mare properly.

2. General anesthesia for cesarean section.

1. Prep ventral abdomen before anesthesia.
2. Use local infiltrative block in ventral abdominal wall
3. Use nonbarbiturate induction such as xylazine, diazepam/ketamine and provide endotracheal intubation and maintenance or with low levels of isoflurane.
4. Make all arrangements to allow the shortest time between induction and delivery of the foal.

3. Arrange for basic emergency equipment for foal resuscitation upon delivery.

1. Have a separate group to work with foal while surgeons handle the mare.
2. Intubate the foal before clamping umbilical cord with cesarean or complicated dystocia.
3. Provide immediate post birth evaluation for high-risk foal (See Initial Evaluation and Minimum Data Base).

Figure 1. Short acting general anesthesia and hoist (mechanical or power) for dystocia management.