Dystocia, caesarean section, and foetotomy in the mare Flashcards
(21 cards)
Incidence of dystocia
Occurs in about 4% of TB mares, higher in Shetlands and heavy horses
Higher in primiparous and very old mares
Most are fetal maldisposition
Fetal maldisposition
Commonest reason for difficult foalings
Damage to uterine wall minimised by cupping sharp points of the deviated extremity while manipulating back into place
Premature separation of the allantochorion
‘Red bag’
Rupture the sac and aid delivery quickly
Ensure not prolapsed bladder or vagina - look for cervical star
Uterine inertia
Primary uterine inertia: voluntary suppression of parturition caused by disturbance, either leave alone or induce and monitor closely
Secondary uterine inertia: follows another primary cause of dystocia
Weak abdominal contractions
Varying degrees
May be related to weakened musculature due to overstretching e.g. hydrops and twins, or some infirmity
May be no underlying cause
Foaling should be aided by controlled traction
Failure to get down
Occasionally they foal standing up
Support the weight of the foal during delivery and for a few minutes after to prevent premature breaking of the cord
Bony tissue obstruction of birth canal
Uncommon
May require c-section
Distortions of pelvic canal can follow pelvic fractures
Watch closely for indication of elective c-section
Soft tissue obstruction of birth canal
Open Caslicks at start of 2nd stage labour (or as close to foaling as possible)
Vaginal obstruction uncommon
Cervix rarely a cause of dystocia unless previous damage
Relative oversize of foal
Rare
When first foaling mares strain powerfully without adequate relaxation, there is a danger of recto-vaginal fistula formation
Fetal monsters and abnormalities
Rare
Schistosomus reflexus is rare but one of the most common forms
Foetotomy useful
Indications for c-section
The commonest reason for c/section in the mare is dystocia. Elective c/sections are carried out less frequently, but may be indicated for a variety of reasons including pelvic abnormalities, ventral abdominal rupture, or untreatable long bone fracture.
Surgical approach to c-section
Most clinicians prefer the use of general anaesthesia for the operation as it is safer for the mare and allows a more controlled approach to the procedure.
Post operative care after a c-section
If the placenta has been retained, oxytocin treatment is continued, and the mare’s uterus is manipulated per rectum on a daily basis to prevent adhesion formation. Postoperative intra-uterine lavage is carried out if there is evidence of or concern about endometritis. Parenteral antibiotic therapy should also be considered. The mare should be offered a light laxative diet and limited but regular exercise for the first few days. The foal is managed as deemed appropriate by its clinical status.
Complications associated with c-section (mare)
Retention of placenta
Fatal haemorrhage
Peritonitis
Adhesions
Ventral oedema
Incisional herniation
Drying up subsequent to the box rest
Infertility may occur but rare
Complications associated with c-section (foal)
Hypoxia
Effects of anaesthesia
Clamping of the cord and associated problems
Lack of compression which it would have received in birth canal
Prognosis for c-section
Good for mare if the decision to operate is made early in dystocia and prolonged attempts at manual vaginal delivery haven’t been made. However, unless it was an elective operation, the foal is often likely to be dead at the start of surgery since survival during the second stage of labour is short
What are the two techniques for a foetotomy
Percutaneous foetotomy: tubular fetotome through which a flexible wire saw is passed
Sub-cutaneous foetotomy: Involves dissecting parts of the fetus out within its skin
Factors used to decide between fetotomy and c-section
Extent of foetotomy likely to be required
Accessibility of foetus
Experience of vet and availability of equipment
Future fertility of the mare (c-section if fertility is paramount)
Moderate to mild asphyxia causes
- Maternal systemic disease
- Placental disease
- Foetal disease
- Intrapartum problems
Chain of events following increased hypoxaemia and acidaemia
- Decrease pulmonary blood flow
- Decreasing left atrial return
- Dropping left atrial pressure
- Resulting in increasing right to left shunting through the foramen
Early severe asphyxia results in:
- Stimulation of the foetus to breath while still in utero
- If gasping does not resolve asphyxia it will stop causing primary apnoea
- Then a second series of gasping (more irregular)
- Secondary apnoea, irreversible unless resuscitation is initiated
- May pass through these stages while still in utero
