Acesarean section (hysterotomy) is scheduled or performed on an emergency basis.
Hysterotomies may be scheduled for those bitches that have had previous dystocia or hysterotomy, and for those cases in which dystocia is anticipated (e.g., there is radiographic evidence that one or more of the puppies' skulls is larger than the mother's pelvic canal, such as bitches with pelvic fracture malunions).
Hysterotomy is done on an emergency basis for cases of dystocia refractory to medical management. Fetal putrefaction and maternal toxemia secondary to intrauterine fetal death are less common indications for hysterotomy.
Dogs and cats will continue to produce milk after whelping even if an ovariohysterectomy is performed, as prolactin and cortisol will maintain lactation.
Cesarean section itself does not have a negative impact on fetal survival. Other factors, such as prolonged dystocia ( greater than four hours) result in higher rates of stillbirth and neonatal death.
Patients who present for dystocia often will be dehydrated, so it is appropriate to fluid-resuscitate them before surgery. Electrolyte abnormalities should be corrected pre-operatively. Every animal must be evaluated for evidence of hypovolemic shock, and treated appropriately if necessary. The vast majority of animals, however, will require only one-third to one-quarter of their shock dose of isotonic crystalloid fluid (15-20 ml/kg), followed by a surgical rate of fluid administration (10 ml/kg/hr crystalloid unless complicating factors are present, such as heart disease or hypoproteinemia).
Nearly all analgesic and anesthetic drugs will cross the placenta and enter the fetal circulation. As such, it is important to minimize fetal exposure to cardiovascular depressant drugs by minimizing time from induction to delivery. This can be achieved by performing all pre-surgical preparatory work in advance. The operating suite should be set up with all monitoring equipment at the ready. The patient's IV catheter should be in place and the ventrum should be shaved from 1 cm rostral to the xyphoid to the level of the pubis. A preliminary scrub of the surgical field should be performed before induction of anesthesia.
Anesthesia can safely be induced with diazepam (0.25 mg/kg) and propofol (2-4 mg/kg IV), titrated to effect. The use of diazepam lowers the quantity of propofol required to achieve anesthesia. The patient should then be intubated and maintained with isoflurane or sevoflurane, at the lowest level that will maintain light anesthesia. A final surgical scrub is performed before commencing surgery.
A local anesthetic administered as a line block or via epidural can decrease the amount of inhaled anesthetic needed to keep the patient anesthetized (and therefore decrease the anesthetic load delivered to the puppies).
Alternatively, a lidocaine local anesthetic can be used after the surgery, but before complete closure of the abdominal incision (after the linea alba has been apposed). A 25g needle and syringe are handed to the surgeon in a sterile manner, and 1-2 mg/kg of 2% lidocaine are drawn into the syringe. Starting at the midline of the skin incision, inject a small amount of solution in a fan-like manner, infusing at all tissue layers from the dermis to the peritoneum. Remove the needle, and repeat a small distance away (1-2 cm). Always aspirate before injecting local anesthesia to prevent accidental intravenous administration.
Cats are much more sensitive than dogs to the toxic effects of lidocaine, so particular attention must be paid to the dose and route administered (not to exceed 2 mg/kg if used locally; 1 mg/kg if given intravenously).
If there is evidence of fetal distress (i.e., fetal heart rates drop below 180 beats/min, confirmed with ultrasound or Doppler), the local anesthetic should be performed after the hysterotomy.
There must be two teams present at every hysterotomy: one team to perform the surgery and monitor the anesthetized mother, the other to receive and resuscitate the babies.
The gravid uterus must be handled gently and with minimal traction to avoid avulsing the uterine vessels or tearing the uterine wall. The abdominal cavity is protected from spillage of uterine contents with moistened laparotomy pads placed under and around the uterus. A stab incision is made in the ventral aspect of the uterine body, and extended with Metzenbaum scissors.
This incision should be large enough to fit each puppy through without tearing of the wall. (Photo 2) The puppies are then "milked" out of the hysterotomy, from cranial to caudal. Each puppy should still be in its amniotic sac, and its placenta may be attached to the uterine wall. It is important to detach the placenta with gentle caudal traction, so as not to rupture any of the many blood vessels located superficially in the uterine wall (Photo 3). If the placenta does not detach readily, it is left in place until the end of the procedure. Each puppy is handed off to the recovery team as it is delivered (see, Addressing the puppies).
When all the puppies are removed from the first horn, it is replaced into the abdomen and the other exteriorized. The puppies are then removed from the second horn via the same uterine body incision. Palpate the pelvic canal to ensure that no puppies remain at that site. When all the puppies have been removed and before closing the hysterotomy, any remaining placentas are removed. It is preferable that the number of placentas removed equal the number of pups. Otherwise, complications associated with retained fetal membranes can later arise, such as acute metritis. (It is possible that they would pass naturally, but the incidence of complications related to retained placenta following hysterotomy is not known.)
A variety of techniques have been employed to close the hysterotomy, and all seem equally efficacious (Photo 4). It can be closed in one or two layers, with either interrupted or continuous-suture patterns. A two-layer closure entails an appositional closure of the mucosa and submucosa, followed by an appositional or inverting pattern in the seromuscular layers.
Employ a synthetic monofilament absorbable suture [such as 3-0 or 4-0 polydioxanone (PDS), polyglyconate (Maxon) or poliglecaprone 25 (Monocryl)] with a taper needle. Local lavage is generally sufficient, unless gross contamination of the abdomen with uterine contents has occurred. If this is the case, the laparotomy pads are removed and the peritoneal cavity is copiously lavaged with warm, 0.9% saline. At this point it is appropriate to change contaminated gloves and instruments. It will now be easy to identify and arrest any persistent hemorrhage, such as from a traumatized uterine vessel. Inspect the other abdominal organs for evidence of disease or injury. Finally, the omentum should be drawn over the ventral aspect of the uterus.
If the owners do not plan future breedings, an ovariohysterectomy can be performed after hysterotomy. Alternatively, an en bloc ovariohysterectomy can be performed, with the puppies removed from the uterus by the recovery team.
The abdominal wall is closed routinely in three layers (rectus sheath, subcutaneous tissue and skin), using local anesthetic if not previously performed. It is preferential to close the skin with a subcuticular suture pattern with a synthetic absorbable monofilament suture material (such as Monocryl).
External skin sutures are a source of irritation for the mother and the puppies, and puppies will frequently suckle or scratch at them, increasing the chance of incisional irritation or infection. This also obviates the need to remove the sutures at some point in the future.
Addressing the puppies
Each pup is handed off to an assistant, generally with the amniotic sac and placenta still attached. The amniotic sac is ruptured and peeled away from the puppy. The umbilicus is clamped with a mosquito hemostat and transected. The puppy is rubbed vigorously, both to dry it off and to stimulate breathing. The nares and nasopharynx are gently suctioned with a bulb syringe to remove residual amniotic fluid.
If the puppy is not breathing spontaneously, or if the heart rate is low (<180 bpm), doxapram is administered sublingually (one drop per puppy). If opioids have been administered to the bitch prior to delivery, they should be antagonized with a drop of naloxone, sublingually. If this does not stimulate respiration, epinephrine is administered, also one drop sublingually. Flow-by oxygen is administered if the puppy is cyanotic and/or brachypneic.
For orally administered mediations to achieve any effect, there must be adequate perfusion of the oral mucosa. If the heart rate is low or absent, compression of the thoracic wall is performed; mouth-to-mouth artificial respiration may be necessary.
Once the puppy is stable, the umbilicus can be ligated with a single, encircling ligature of absorbable suture material. The umbilical stump is disinfected with povidone-iodine solution. The puppy is examined for evidence of birth defects (such as cleft palate, umbilical hernia, atresia ani or limb deformities) and placed in an incubator set at 90 degrees to 95 degrees.
The puppies are introduced to the mother only after she has completely recovered from anesthesia, to minimize the risk of her traumatizing them. The bitch and litter should be discharged from the hospital as soon as they are stable. This will minimize the chance of nosocomial infection, and will minimize the stress on the bitch, thereby increasing the likelihood of her engaging in appropriate mothering behavior.
Antibiotics generally are not necessary for hysterotomies. Exceptions include cases of fetal putrefaction, uterine infection and gross contamination of the peritoneal cavity with uterine contents. If fetal putrefaction or uterine infection is suspected, a broad-spectrum antibiotic (such as cefazolin, 22 mg/kg IV) should be administered pre-operatively. Post-operative antibiotic therapy is only warranted if there has been gross contamination during surgery.
For healthy bitches and puppies undergoing hysterotomy, reported neonatal survival rates are 70 percent to 90 percent. The rates are considerably lower if the mother is in poor condition or has undergone a prolonged dystocia pre-operatively. Maternal mortality rates are reportedly 0 to 2 percent in dogs and cats.
Intra-operative endometrial hemorrhage is possible, especially at sites of placental attachment. If this occurs, administer oxytocin and apply pressure. If bleeding is profuse and intractable, ovariohysterectomy should be recommended.
Potential post-operative complications include persistent hemorrhage, pyometra, mastitis, wound infection and peritonitis.
See description of technique in Toombs, JP and Clarke, KM: Basic Operative Techniques. In Slatter, DH (ed): Textbook of Small Animal Surgery. WB Saunders, Philadelphia, 2003, p. 215.