Preoperative evaluation

Performing a maternal evaluation and obtaining surgical consent are essential before the anesthesia provider administers anesthesia for a C/S. Along with performing a standard preoperative maternal evaluation, including a focused history and physical examination, the anesthesia provider should also ascertain information regarding fetal gestation and pregnancy-related complications. Laboratory studies are obtained as maternal comorbid conditions and the planned procedure dictate; however, a blood sample for type and screen or crossmatch is often standard for multiparous women or for parturients with other common physiologic alterations. Preparation for elective, urgent, and emergent C/S includes aspiration prophylaxis and establishment of adequate venous access (Box 186-1).

Regional anesthesia

Subarachnoid block and epidural anesthesia are recommended for elective C/S. When compared with general anesthesia, these techniques provide excellent anesthesia, prevent fetal depression and maternal airway management difficulties, and do not place the mother at risk for aspirating gastric contents. Local anesthetic agents, with or without the addition of an opioid, may be used for either a subarachnoid block (Table 186-1) or an epidural anesthetic (Table 186-2).

Before the anesthesia provider initiates neuraxial regional anesthesia, the patient must receive adequate hydration to prevent or attenuate maternal hypotension and uteroplacental insufficiency, regardless of whether or not an epidural anesthetic has already been instituted for labor. Intravenously administering approximately 1 L of fluid (unless preeclampsia or other maternal cardiac conditions exist) is ideal prior to infusing anesthetizing bolus doses of a local anesthetic agent. Maternal hypotensive episodes are ideally treated with intravenous hydration, and if these episodes are persistent or involve changes in fetal heart rate, an indirect-acting sympathomimetic agent (e.g., ephedrine, titrated to effect) or direct-acting sympathomimetic agent (e.g., phenylephrine) should be administered intravenously. Regardless of anesthetic technique used, patients should be positioned to provide left uterine displacement to prevent aortocaval syndrome.

Emergent or urgent cesarean section

The need for an emergency C/S is a constant threat during labor. An operating room set up for a “crash” induction must always be available. Time is critical to ensure delivery of a healthy fetus. Although general anesthesia is usually the most expedient option for use in a true emergency situation, regional anesthesia may be a viable option provided that (1) the fetal heart rate returns to normal after obstetric management of nonreassuring fetal status (e.g., optimize maternal position, provide supplemental O₂, improve maternal circulation, discontinue oxytocin, administer a tocolytic agent for uterine hypertonus) and (2) an experienced anesthesia provider can place a subarachnoid block in a timely fashion, with ongoing monitoring of the fetal heart rate. Communication between the anesthesia and obstetric teams is essential.

If general anesthesia is required, rapid-sequence induction (Box 186-2) with cricoid pressure should be initiated after the abdomen is prepped and draped. The surgical team is notified that they can safely proceed as soon as proper tracheal tube placement is confirmed. Maintenance with low-concentration inhalation anesthetic agents (e.g., isoflurane or sevoflurane), 50% O₂, and N₂O is used until the umbilical cord has been clamped and the neonate is delivered. Nondepolarizing neuromuscular blocking agents may be given once motor end plate function has recovered from the effects of succinylcholine. After the umbilical cord is clamped, opioids may be administered, given that there is no longer any concern about neonatal respiratory depression. In addition, midazolam may be administered at this time to prevent the patient from experiencing recall while simultaneously allowing for the use of a lower dose of inhalation anesthetic agents (i.e., drugs known to relax uterine smooth muscle), thereby decreasing the risk of uterine hypotonia and persistent uterine bleeding. Following delivery of the placenta, oxytocin (Pitocin, 20 to 40 IU in 1 L of crystalloid solution) may be given to facilitate uterine contractions. If hypotonia persists, oxytocin (as a slow intravenous push) or methylergonovine mesylate (Methergine, 0.2 mg intramuscularly) may be given. Both oxytocin and methylergonovine produce hemodynamic sequelae (see Chapter 189).

The prophylactic use of antibiotics has been shown to decrease the incidence and severity of infections after C/S, and, therefore, antibiotics should be administered either before the abdominal incision is made or immediately after the umbilical cord is clamped. The time of delivery and Apgar scores should be noted on the anesthetic record. Following the operation, the patient should not be extubated until she is awake to minimize the ongoing risk of aspiration.