Preoperative considerations: All patients are considered to have full stomachs. These patients are also usually allowed to have small amounts of clear liquids during labor. For elective cesarean sections, patients should have fasted for 6 hours after a light meal and 8 hours after a heavy meal. Administration of a clear antacid such as sodium citrate may be given approximately 30 minutes before surgery to reduce the possibility of severe aspiration pneumonitis. Patients may also be given an H₂-blocker such as ranitidine to reduce the gastric volume and pH or metoclopramide to promote gastric emptying, decrease gastric volume, and increase the lower esophageal sphincter tone.

Regional anesthesia: Preferred technique because general anesthesia is associated with a higher mortality rate (typically as a result of airway problems). Cesarean section requires a T4 sensory level. Because of the associated sympathetic blockade, patients should receive a bolus of crystalloid or colloid at the time of neural blockade.

General anesthesia: Take all precautions to prevent pulmonary aspiration and failed endotracheal intubation. Parturients may be difficult to intubate because of airway edema, full dentition, or large breasts. In a difficult airway situation in which the fetus is not in distress, the patient should be awakened and an awake intubation performed. If the fetus is in distress and spontaneous or positive-pressure ventilation (by mask or laryngeal mask airway) with cricoid pressure is possible, delivery of the fetus may be attempted.

Suggested steps for cesarean section under general anesthesia: (1) Place a wedge under the right hip for left uterine displacement. (2) Preoxygenate with 100% oxygen for 3 to 5 min. (3) Prepare and drape the patient. (4) When surgeons are ready, perform a rapid-sequence induction with cricoid pressure using propofol, thiopental, or ketamine and succinylcholine. (5) Begin surgery after proper placement of the endotracheal tube is confirmed (avoid excessive hyperventilation). (6) Use 50% nitrous oxide in oxygen with up to 0.75 minimal alveolar concentration (MAC) of a volatile agent for maintenance. A muscle relaxant of intermediate duration is used for relaxation. (7) After the neonate and placenta are delivered, 20 to 80 U of oxytocin is added to the first liter of IV fluid followed by 20 U in the next liter of IV fluid. Additional IV agents can be given to ensure amnesia. (8) If the uterus does not contract readily, provide an opioid and discontinue the halogenated agent. Methylergonovine (Methergine) or 15-methylprostaglandin F_2α (Hemabate) may also be used. (9) Place an oral gastric tube to decrease the likelihood of pulmonary aspiration on emergence. (10) At the end of surgery, reverse muscle relaxants and extubate the patient while she is awake.

Anesthesia for the Complicated Pregnancy

Umbilical cord prolapse: Risks may include excessive cord length, malpresentation, low birth weight, grand parity (more than five pregnancies), multiple gestations, and artificial rupture of membranes. Sudden fetal bradycardia and significant decelerations may occur.

• Treatment: Place the patient in Trendelenburg or knee–chest position and manually push the presenting aspect of the fetus into the pelvis. Proceed to emergency cesarean section under general anesthesia. If the fetus is not viable, then vaginal delivery can proceed.

Primary Dysfunctional Labor

Multiple gestations: Breech presentation and prematurity are common risks. Regional anesthesia may shorten the interval between the birth of the first and second baby and possibly improve the acid–base status of the second twin. These patients are prone to hypotension from aortocaval compression.

Breech Presentation

• The shoulders or head can become trapped after vaginal delivery of the body; therefore, some perform cesarean deliveries on all breech fetuses. If vaginal delivery is performed, manual or forceps-assisted partial breech extraction is usually needed.

• Epidural anesthesia may decrease the likelihood of a trapped head because of relaxation of the perineum. If the head becomes trapped in the uterus during cesarean section under regional anesthesia, general anesthesia or nitroglycerin may be required to attempt to relax the uterus.

• External cephalic version (ECV) may be attempted after the 34th week of gestation and before the onset of labor. A tocolytic agent might be administered during the ECV, and an epidural may be placed to facilitate it.

Abnormal Vertex Presentations

• Abnormal presentations such as occiput posterior may cause prolonged and painful labor and sometimes require manual, vacuum, or forceps rotation. Regional anesthesia may be used to provide perineal analgesia and pelvic relaxation.

• Face presentation generally requires cesarean section. A vaginal delivery may still be possible in a compound presentation (an extremity enters the pelvis along with either the head or the buttocks).

• Shoulder dystocia: Sometimes relieved by obstetric maneuvers, but a prolonged delay in delivery could result in fetal asphyxia. General anesthesia may be needed if there is no epidural in place.

Antepartum Hemorrhage

A 22-year-old G3P1011 at 37 weeks of gestation and medical history of cocaine abuse presents with vaginal bleeding and abdominal pain. She has had one spontaneous vaginal delivery in the past. Upon arrival, the patient’s blood pressure is 88/40 mm Hg and heart rate is 117 beats/min. Fetal heart rate (FHR) monitoring demonstrates late decelerations with decreased variability. The obstetricians decide to perform an emergency cesarean section on the patient.

What is the most likely diagnosis in this patient?

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