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.

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.

Anesthetic considerations

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).

Photo 1: A line block is easy to perform, and may reduce inhalant anesthetic requirements. Small boluses of 2% lidocaine are injected along the ventral midline from cranial to the umbilicus to cranial to the pubis. A 25g needle is inserted percutaneously into the linea alba. Aspirate back on the syringe to ensure that there is negative pressure and that a blood vessel has not inadvertently been entered. A bleb of anesthetic is injected as the needle is being withdrawn. Repeat process a few millimeters caudal, and for the remainder of the incision.

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.