David Michael Tillson Department of Clinical Sciences, Auburn University, Auburn, AL, USA The procedure called a Cesarean section (C‐section) has been around for most of human history. The term has been attributed to the legend that Julius Caesar was “cut from his mother’s womb” as she died in childbirth. While a good story, its accuracy is questioned.1 The term more likely arose from a decree from Caesar that the child of any woman dying during childbirth in Rome would be taken “by section” to maintain the population of the Empire. In veterinary medicine, a C‐section is used both as an emergency procedure in patients experiencing difficulties during delivery (i.e., dystocia) and increasingly, as an intentionally planned and scheduled procedure in breeds considered to be at high risk of dystocia. The primary indication for a C‐section is anticipated or real‐time difficulty in delivering fetuses at the time of birth. For this reason, a C‐section can be “scheduled” or emergent. A scheduled C‐section is typically used for breeds with a high risk of developing difficulties during parturition, known physical abnormalities that would negatively impact a vaginal delivery, large litter sizes, or owner preference or convenience. Neonatal survival is reportedly excellent (99%) for scheduled C‐section compared to an emergency C‐section (87%).2 An emergency C‐section is required when a patient is in stage 2 labor and unable to deliver a litter vaginally. This could mean a patient in active labor without producing any neonates, or it could be a partial delivery but incomplete parturition. The patient requiring an emergency C‐section needs to be carefully evaluated and stabilized as effectively as possible prior to anesthesia and surgery. The process of labor is divided into three stages (Table 26.1). Once the first stage of labor has begun, parturition should progress in a timely manner, and long delays without productive delivery should initiate concern. Table 26.1 Stages of labor.3,4 There are numerous conditions that can impair normal parturition. These conditions can be physical or physiological and are typically categorized as being of maternal or fetal origin. In dogs, roughly 3/4 of dystocias are of maternal origin, and in cats, 2/3 of dystocias are considered to be of maternal origin.3,5 Physical issues affecting the dam or queen are related to the pelvic canal diameter, such as small pelvic size compared to fetal size, previous pelvic trauma, as well as vaginal malformation or the presence of vaginal bands that impede the passage of the fetus. More commonly occurring in the cat, uterine torsion is another potential cause of dystocia that is rare but reported. Patients with uterine torsion have been actively in stage 2 labor (contractions and straining) but without results. They can rapidly decompensate with this condition and may present to the veterinarian as depressed or moribund, tachycardiac, exhibiting poor peripheral perfusion, and have a painful abdomen on palpation. Aggressive stabilization and rapid surgical intervention are needed to salvage these patients. Other maternal factors, such as abdominal hernias or uterine prolapse, may impair the ability of the dam to generate effective abdominal pressure for labor. Similarly, the pelvic canal diameter could be compromised by soft tissue compression or non‐osseous obstructions. Physiological or medical concerns for a dystocia patient often include physical exhaustion, hypotension, hypoglycemia, and/or hypocalcemia. Primary or secondary uterine inertia may be the most common reason for dystocia.3 Primary uterine inertia involves a failure of the uterus to begin organized, propulsive contractions. In complete primary uterine inertia, stage 2 labor is not reached, while partial primary uterine inertia results in weak, ineffective contractions only. Secondary uterine inertia can be the result of exhaustion of the uterine musculature caused by obstructions, mispositioned fetuses, or the delivery of a large litter. Fetal causes of dystocia are typically associated with fetal positioning, fetal size, or fetal abnormalities (malformation, giantism). In some patients, problems with fetal positioning or a “stuck” fetus can be managed through sedation, lubrication, and digital manipulation; however, problems created by excessive fetal size or fetal abnormalities typically necessitate surgical intervention. Low fetal numbers or the presence of a single fetus may not stimulate progression toward stage 2 labor, resulting in extended gestation. A C‐section is appropriate for gestational lengths of greater than 70 days in the dog or 71 days in the cat (day 0 being designated as the luteinizing hormone (LH) surge with ovulation happening around 48 hours after that). Medical management can be considered when the female is in good health, there are no known physical conditions to impair fetal passage, and the cervix is adequately dilated. Imaging should be used to confirm the pregnancy and fetal positioning prior to beginning treatment.6 Fetal heart rates should also be within normal limits, indicating no fetal stress at the time medical management is initiated. Medical management is typically supportive in nature, providing fluids, glucose, and a warm, safe, comfortable environment for parturition, as well as administration of oxytocin and calcium gluconate (Table 26.2) if the patient is hypocalcemic. If a stuck fetus or fetal malpositioning is determined to be the cause of the dystocia, physical manipulation can be tried to see if the fetus can be removed or repositioned, allowing parturition to continue. Despite medical intervention, it is estimated that 60–80% of dogs and cats with dystocia will still require surgical intervention.3,5 Table 26.2 Drugs used in the medical management of dystocia.3,7 Fetal heart rate is important to monitor in the patient in late stage 1 or stage 2 labor. The results give the clinician vital information that will heavily influence the decision whether or not to perform an emergency C‐section. The normal fetal heart rate is typically above 200 bpm (180–200 bpm).3,7 Lower rates, between 150 and 170 bpm, are indicative of moderate to severe fetal stress, prompting the consideration of surgical intervention. Fetal heart rates of <150 bpm signal the need for immediate surgical intervention. Care should be taken when assessing fetal heart rates during labor, as uterine contractions may lower the fetal rates during an active contraction. Heart rates should be taken over 30–60 seconds and, ideally, from multiple fetuses for the best evaluation.5 Dogs should complete labor in 3–12 hours; averaging at least one puppy per hour. Cats can present a unique challenge since they can have extended periods of inactivity between kittens, normally completing parturition in 4–16 hours; however, it has been reported that cats can deliver a final kitten up to 42 hours after the initiation of labor.3 Owners unfamiliar with that species‐specific quirk may think their cat is experiencing a dystocia when they are, in fact, having a normal parturition. It is important that feline owners understand a queen experiencing this type of labor should not be in constant distress during this period and should not be in active labor without producing a kitten in a timely manner. If the patient is determined to need surgical intervention, either after initial evaluation or after failed medical management, pre‐anesthetic management is initiated or continued. Intravenous fluids, using a balanced crystalloid solution, are started to correct dehydration and counteract hypotension. A biochemical profile and complete blood count (CBC) should be considered. At a minimum, the patient’s packed cell volume, total protein, blood urea nitrogen (BUN), lactate, glucose, and calcium should be evaluated and supplementation provided as needed. Although they are commonly encountered in dogs, neither hypoglycemia nor hypocalcemia is routinely seen in cats experiencing dystocia.8 When there is documented fetal death, extra care must be taken in surgery to avoid contamination of the surgical field or abdominal cavity. Patients suffering from multiple dead fetuses should be considered candidates for an “en‐bloc” C‐section. A scheduled (i.e., “planned” or “elective”) C‐section is different from the dystocia‐driven, emergency C‐section. Scheduled C‐sections are routine for breeds acknowledged to have a high risk of dystocia. These breeds include English and French Bulldogs, Boston Terriers, Pekingese, Pugs, and other brachycephalic breeds. Many other breeds have been reported to be susceptible to dystocias requiring a C‐section, including Labrador and Golden Retrievers, German Shorthair Pointers, Chihuahuas, and Scottish, Yorkshire, and Dandie Dinmont Terriers, as well as giant breeds like Great Danes, Boerboels, and Mastiffs.3,9,10–13 Cat breeds identified as being prone to dystocia include Domestic Shorthair, British Shorthair, Devon Rex, Birman, and Ragdoll cats and Oriental breeds.7,8,11 The use of scheduled C‐sections in breeds at low risk of dystocia eliminates the potential for dystocia‐related complications; however, it introduces the risks associated with anesthetic, surgical, and post‐operative complications. No significant difference was found in the percentage of neonates surviving to discharge (overall 93%) between brachycephalic breeds (95%) undergoing C‐sections when compared to non‐brachycephalic breeds (92%).2 The same study found that the puppies delivered by elective C‐section were significantly more likely to survive discharge (99%) than puppies delivered by emergency C‐section (87%).2 A scheduled C‐section can also be chosen for the convenience of the breeders and veterinarian, although the ethics of such a choice has been questioned.13 It is preferable to get a scheduled C‐section patient as close to full‐term gestation as possible to maximize neonatal survival. Gestation lengths can vary based on breed, litter size, and species. Normal gestation ranges from 57 to 72 days in the dog and 54–74 days in the cat.4 If the decision for a C‐section in a dog is to be based on breeding dates alone, it is recommended to do the C‐section at full term (61–65 days) based on the last successful breeding with careful client counsel regarding breeding, ovulation, and fertilization timing (e.g., measuring LH surge). Clients should understand that in using breeding dates alone, individual variance could still potentially result in prematurity at the time of C‐section.3 Litter size can influence the duration of gestation, and larger litters tend to have a shorter gestational period. Using this criterion, puppies should be viable but there is a risk that the dam could go into labor prior to the C‐section. The veterinarian should make sure the owner is aware of the clinical signs of parturition: nesting behaviors, a drop in body temperature, milk let‐down, and other signs of early labor, in order for the patient to present to the veterinarian prior to the development of active labor. The measurement of a serum progesterone level in the bitch increases the accuracy of the timing decisions associated with a scheduled C‐section. Serum progesterone levels typically fall 12–24 hours prior to onset of parturition, in conjunction with the reported body temperature drop (less than 99 °F). A progesterone concentration of less than 2.0 ng/ml in a late‐gestational bitch is used at the author’s institution to signal the scheduled C‐section should occur within the next 12–18 hours. As with all such testing, not all dogs follow the rules, and attention must also be focused on the patient for other signs of impending parturition as previously discussed. A dystocia‐prompted C‐section is considered an urgent or emergent surgical procedure. As with many surgical emergencies, the status of the patient needing the procedure can vary from anxious, yet stable, to moribund based on the duration of labor, fetal viability, and overall health status of the patient. Once it is determined that medical management is not appropriate or not working, there should be rapid progress toward surgical intervention. Considerations in when to begin anesthesia and surgery include the current health status of the dam, the stage of labor, and fetal heart rates as an indicator of intrauterine stress. Specific indications for surgical intervention in a dystocia are presented in Table 26.3. Pre‐operative management for a patient with dystocia requiring a C‐section is typically aimed at making the patient a better, more stable candidate for anesthesia and surgery. Many of these measures, including fluid administration, pain management, sedation, and correcting hypocalcemia or hypoglycemia, would be undertaken during initial assessment and stabilization of the patient. Table 26.3 Indications for surgical management of a dystocia.6 Table 26.4 Client communications.
26
Cesarean Section
Introduction
Indications
Dystocia
Stage 1
Silent; cervical dilation, increasing uterine contractions; typically, less than 12 h; both the bitch and queen delay the onset of labor when in unfamiliar or stressful environments; panting, restless, nesting behavior (bitch); vocalization and loud purring in the queen
Stage 2
Active contractions and process of fetal expulsion; 3–12 h in bitch; averaging a puppy/hour; queen can take longer 4–16 h but occasionally hours between kittens
Stage 3
Final stage – complete expulsion of placental membranes; often passed between fetuses
Drug
Dosage
Comment
Crystalloid fluids
2.5 mL/kg/hr (60 ml/kg/day) – standard maintenance fluid rate; additional fluid volume added to compensate for dehydration (see comments)
Bolus dose of 90 mL/kg (shock dose) can be given divided over an hour; patient should be checked every 15 min for responsiveness to resuscitation (blood pressure, heart rate, mucous membrane color, etc.) and for any signs of fluid overload.
Calcium gluconate (10%)
0.2 mL/kg IV (dog/cat)
1–5 mL per dog SQ
Intravenous administration can cause cardiac arrhythmias if given too rapidly; cardiac auscultation should be performed prior to administration and during administration.
Use of calcium in queens is controversial; use with care.
Oxytocin
0.1 units/kg IM (current recommendation – dog/cat)
Other dosing includes:
0.5–2.0 U/dog or cat IM; or 5–20 U/dog IM.
Scheduled C‐Section
Emergent C‐Section
Maternal (majority of dystocia etiologies)
Fetal
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