Medical management should be considered if there is no evidence of obstruction, and fetal and pelvic size appear normal.
Oxytocin is a peptide hormone that increases the frequency and strength of uterine contractions by promoting influx of calcium
into myometrial cells. Oxytocin also promotes post partum uterine involution, aids in control of uterine hemorrhage, and assists
in expulsion of retained placentas. The dose for oxytocin has traditionally been reported at 5-20 units IM in the dog and
2-4 units IM in the cat. However, with an increase in the use of uterine contraction monitoring (Whelpwise, Veterinary Perinatal
Specialties Inc, Wheat Ridge, CO) in veterinary patients, there is a growing body of evidence to suggest that traditional
doses may be too high, potentially causing uterine tetany, ineffective contractions, and decreased fetal blood flow. Recent
data suggests that doses of 0.5-2 units are effective in increasing the frequency and quality of contraction. The oxytocin
dose may be repeated in 30 minutes if expulsion of a fetus has not resulted. If labor proceeds and a fetus is delivered, oxytocin
may be repeated every 30 minutes as needed to assist in expulsion of the remaining fetuses.
Calcium gluconate may be considered if weak, infrequent contractions are noted or when labwork reveals hypocalcemia. Retrospective studies have indicated that many patients who fail to respond to oxytocin
alone may respond to a combination of calcium and oxytocin. The dose for calcium gluconate (10% solution) as a uterotonic
agent is 11 mg/kg diluted in saline and given subcutaneously, or added to IV fluids and given slowly while monitoring an ECG
for arrhythmias. If hypocalcemia is documented, a dose of 50-150 mg/kg intravenously should be used. Subcutaneous administration
has been reported to result in irritation and potential granuloma formation, though this is an infrequent complication. Dextrose
infusion should also be initiated if hypoglycemia is evident on labwork.
Surgical management should be considered for the following conditions:
- Complete primary uterine inertia
- Partial primary uterine inertia or secondary uterine inertia where large numbers of fetuses remain and response to drugs is
- Fetal oversize
- Gross abnormalities of maternal pelvis (fractures, masses)
- Fetal malformations
- Malpresentation that is not amenable to manipulation
- Past history of dystocia or c-section
- Fetal putrefaction
- Maternal evidence of systemic illness
- Suspicion of uterine torsion, rupture, prolapse, or herniation
- Evidence of fetal distress with poor response to medical intervention
An anesthetic protocol for caesarian section should be selected with the goal of maximizing survival of neonates and dam.
Attempts should be made to minimize exposure of the fetus to anesthetics by keeping the time from induction to delivery as
short as possible. Ideally, the dam should be clipped and prepped prior to induction, equipment should be out, and the surgeon
should be scrubbed and ready. Induction agents should be given to effect. Regional techniques such as line blocks and epidurals may help to minimize the need for other drugs. A line block can be
performed using 2 mg/kg lidocaine infused along the ventral midline. Alternately, epidural lidocaine may be administered in
dogs at a dose of 2-3 mg/kg, not to exceed a total volume of 6 ml. Propofol (4-6 mg/kg IV) or mask inductions are most commonly
used for caesarian section at this time, and have been associated with reduced neonatal mortality in dogs. Anesthetic agents
that have been associated with increased neonatal mortality include thiopental, ketamine, xylazine, medetomidine, and methoxyflurane.