Book Text

Failed Endotracheal Intubation (also see Chapter 42 )

A study of anesthesia-related deaths in the United States between 1979 and 1990 revealed that the case fatality rate with general anesthesia was 16.7 times greater than that with regional anesthesia.^[191] Most anesthesia-related

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**TABLE 58-8** -- Suggested technique of general anesthesia for cesarean section
1. Administer a nonparticulate antacid. Additional agents such as metoclopramide or an H₂ -blocker should be considered in patients at high risk for aspiration or failed intubation.
2. Apply routine monitors, including electrocardiography, pulse oximetry, and capnography. Ensure that suction is functioning and that equipment to correct failed intubation is readily available.
3. Position the patient in a manner to achieve left uterine displacement and optimal airway position.
4. Denitrogenate with a high flow of oxygen for 3–5 minutes or 4 vital capacity breaths.
5. After the drapes are applied and the surgeon is ready, initiate a rapid-sequence induction with thiopental, 4–5 mg/kg, and succinylcholine, 1–1.5 mg/kg. Apply cricoid pressure and continue until correct position of the endotracheal tube is verified and the cuff is inflated. In hypotensive crises, ketamine, 1–1.5 mg/kg, should be substituted for thiopental. A defaciculating dose of muscle relaxant is not necessary.
6. Ventilate with 50% oxygen and 50% nitrous oxide and a volatile anesthetic as necessary. Maintain normocarbia and use muscle relaxation as necessary with either a nondepolarizing muscle relaxant or succinylcholine infusion.
7. After delivery, increase nitrous oxide to 70%, discontinue or reduce the volatile anesthetic, and administer an opioid and a benzodiazepine. Add oxytocin to intravenous fluids.
8. Insert an orogastric tube before completion of surgery.
9. Reverse neuromuscular blockade as necessary at completion of surgery.
10. Extubate when the patient is awake, the anesthesia is adequately reversed, and the patient is following commands.

deaths were due to hypoxemia when difficulty securing the airway was encountered. The most commonly occurring adverse respiratory events are failure to intubate, failure to recognize esophageal intubation, and failure to ventilate. Physical factors seen in pregnancy, including weight gain, enlarged breasts, and oropharyngeal edema, can complicate endotracheal intubation. In addition, certain disease states such as preeclampsia may predispose to failed intubation. Central to decreasing the risk associated with general anesthesia is early assessment of the mother's airway. It has been reported that airway evaluation can often identify a parturient with a difficult airway, but it was not performed in upward of 10% of cases in which maternal mortality occurred.^[192] Others have evaluated the risk factors associated with difficult intubation, and it has been suggested that the greatest risks are associated with a Mallampatti class 4 airway, a short neck, protruding maxillary incisors, and mandibular recession.^[193] From these data, an estimated prediction of a difficult airway has been calculated and highlighted in Figure 58-12 . Regardless of the initial assessment, all patients must have a repeat airway examination performed before initiation of anesthesia for cesarean section because it has been demonstrated that labor may be associated with changes in the maternal airway.^[194] In addition, the experience of the anesthesiologist appears to be a key factor in anesthetic-related maternal mortality. A recent study reviewing a 17-year experience in a teaching hospital reported that most cases of failed intubation occurred when patients were cared for by less experienced anesthesiologists.^[195]

The series of triennial Confidential Enquiries into Maternal Deaths in the United Kingdom have documented numerous cases of maternal mortality associated with general anesthesia^[196] ; in particular, cases have been associated with difficult intubation and pulmonary aspiration. However, it has been suggested that the continuing downward trend of anesthetic mortality in the United Kingdom is associated with a stable number of general anesthetics. ^[197] Therefore, factors other than general anesthesia must also play a role.