Anesthesia for the Difficult Cesarean Delivery
Anjum Anwar
Ted Bangert
Kristen Vanderhoef
INTRODUCTION
Providing anesthesia care for cesarean deliveries is one of the most rewarding aspects of an anesthesiologist’s career. Taking part in the celebration of a new life entering the world never gets tiresome. Keeping the mother and fetus safe leading up to delivery and taking care of mom after delivery are the anesthesiologist’s primary concerns. Unfortunately, the growing obesity epidemic and increased number of cesarean deliveries leading to abnormal placentation make this task increasingly difficult. This chapter will focus on these two groups but will also touch upon higher order repeat cesarean deliveries and the pertinent anesthesia concerns. The common theme of any difficult delivery is the need for individualized care involving optimal communication across disciplines.
Providing anesthesia for the difficult cesarean section (CS) patient requires preparation and a multidisciplinary team approach. Inclusion of the anesthesia team early in pregnancy, when possible, is of utmost importance. Together we can strive to provide the best care possible for our most challenging patients.
PHYSIOLOGICAL AND ANATOMICAL CHANGES IN HEALTHY PARTURIENTS
There are changes to nearly every organ system in healthy women during pregnancy. The respiratory system sees an increase in minute ventilation, alveolar ventilation, tidal volume, and respiratory rate with pregnancy (Figure 11-1). Cardiovascular changes include increases in blood volume, plasma volume, cardiac output, stroke volume, and heart rate. Plasma volume increases more than red cell volume leading to a physiologic anemia. There is a decrease in mean arterial blood pressure. For the nervous system, there is importantly a decrease in anesthetic requirements; this includes local anesthetics for standard vaginal delivery or CS as well as inhalational agents should general anesthesia be required. The gastrointestinal system has an increase in gastrointestinal reflux disease secondary to increased volume and acidity of gastric contents as well as diminished lower esophageal sphincter tone, increasing the risk of pulmonary aspiration.1 The kidneys present with an increase in glomerular filtration rate and a subsequent decrease in creatinine. Levels of nearly all coagulation factors also increase during pregnancy, causing a hypercoagulable state.
 FIGURE 11-1 Normal lung volume changes in pregnancy. (From Suresh M. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Philadelphia: Wolters Kluwer; 2013.) |
ANESTHESIA CHALLENGES FOR THE HEALTHY PARTURIENT
There are factors complicating the anesthetic plan for any pregnant patient. First, parturients are more likely to have an airway that is more difficult for endotracheal intubation. Also, pregnant patients greater than 20 weeks estimated gestational age are considered to have a full stomach, regardless of timing of last oral intake. Details about the airway and gastrointestinal tract are discussed later in the chapter. Pregnant women are more at risk for failed intubation and aspiration due to these airway and gastrointestinal changes, and it is due to those risks that neuraxial anesthesia is almost always preferable over general anesthesia. Intraoperatively, the obstetric anesthesiologist must always be aware of, among other complications, the potential for hypotension after neuraxial anesthesia as well as intraoperative blood loss. Postoperatively, some of the more common complications requiring vigilance include pain, nausea, and hypovolemia.
MORBID OBESITY
Morbid obesity in pregnancy has deleterious effects on multiple organ systems. Morbidly obese patients present with many challenges, and these patients should have a consultation with an anesthesiologist early in their pregnancy. In the United States in 2015 to 2016, the prevalence of obesity was 39.8% affecting a total of 93.3 million adults.2 The prevalence of obesity in pregnancy is similar; approximately, 24.8% of women delivering live-born infants in 2014 were obese before becoming pregnant.3 In
addition to the complications mentioned below, obesity also increases the maternal risk of venous thromboembolism, preeclampsia, gestational diabetes, wound breakdown, and infection.4 These patients generally present with other chronic non-pregnancy-related comorbidities as well, such as hypertension, hyperlipidemia, and obstructive sleep apnea (OSA) (Table 11-1). Unfortunately, these patients have a higher chance of requiring cesarean delivery, as well as higher risk of requiring emergent cesarean delivery. Several studies have shown that increasing BMI increases cesarean section rates.4
addition to the complications mentioned below, obesity also increases the maternal risk of venous thromboembolism, preeclampsia, gestational diabetes, wound breakdown, and infection.4 These patients generally present with other chronic non-pregnancy-related comorbidities as well, such as hypertension, hyperlipidemia, and obstructive sleep apnea (OSA) (Table 11-1). Unfortunately, these patients have a higher chance of requiring cesarean delivery, as well as higher risk of requiring emergent cesarean delivery. Several studies have shown that increasing BMI increases cesarean section rates.4
TABLE 11-1 Physiological and Anatomical Changes in a Morbidly Obese Parturient | ||
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THE OBSTETRIC DIFFICULT AIRWAY
The pregnant airway can be precarious for a number of reasons. The physiology of pregnancy causes venous engorgement as well as upper airway edema, which makes tracheal intubation more difficult. Enlarged breasts can hinder laryngoscope placement. A combination of decreased functional residual capacity (FRC) and increased oxygen consumption results in a decreased time to oxygen desaturation with induction of anesthesia (Figure 11-2), making rapid control of the airway
essential. A thorough physical examination of the airway includes Mallampati score (Figure 11-3), the patient’s ability to protrude the jaw anteriorly (Figure 11-4), mouth opening, thyromental distance (Figure 11-5), neck range of motion, and the presence of loose teeth. Comorbidities such as obesity can make the airway even more challenging for intubation.
essential. A thorough physical examination of the airway includes Mallampati score (Figure 11-3), the patient’s ability to protrude the jaw anteriorly (Figure 11-4), mouth opening, thyromental distance (Figure 11-5), neck range of motion, and the presence of loose teeth. Comorbidities such as obesity can make the airway even more challenging for intubation.
 FIGURE 11-2 Patient oxygenation in pregnant and nonpregnant women before and after apnea. (From Suresh M. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Philadelphia: Wolters Kluwer; 2013.) |
 FIGURE 11-3 Mallampati score is used to help predict the difficulty of intubation. A class I airway in general predicts the smallest chance of difficult intubation, and class IV airways in general give the highest likelihood of difficult intubation. (From Suresh M. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Philadelphia: Wolters Kluwer; 2013.) |
 FIGURE 11-4 Airway classes defined by patient ability to protrude the jaw anteriorly. (From Suresh M. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Philadelphia: Wolters Kluwer; 2013.) |
 FIGURE 11-5 Thyromental distance measurement and its implications for difficult laryngoscopy and intubation. (From Suresh M. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Philadelphia: Wolters Kluwer; 2013.) |
Distance Measurement and Its Implications for Difficult Laryngoscopy and Intubation
If general anesthesia is required for a cesarean delivery, adequate preoxygenation with 100% oxygen is a must. Patient positioning is also of utmost importance, with the goal of placing the patient in the “sniffing” position, see Figure 11-6. Due to the “full stomach” status of all pregnant women after 20 weeks estimated gestational age, a rapid sequence induction (RSI) is required. In this scenario, an intravenous induction agent is given immediately followed by a rapid acting paralytic without first attempting to
mask ventilate. If the airway is not secured quickly, PaO2 decreases more quickly than in a nonpregnant patient (Figure 11-2) which then necessitates mask ventilation. Figure 11-7 algorithm demonstrates proper management in the difficult obstetric airway. This specific algorithm takes into account that not one, but two lives are at stake in the obstetric setting. Figure 11-8 demonstrates the importance of adhering to the difficult airway algorithm as greater than two intubation attempts can cause serious consequences. This results from tissue trauma with laryngoscope placement as well as airway edema from attempts at passing the endotracheal tube. Airway manipulation increases salivation, and bleeding may develop with airway trauma, further inhibiting the view of airway structures, making it increasingly more difficult to secure the airway.
mask ventilate. If the airway is not secured quickly, PaO2 decreases more quickly than in a nonpregnant patient (Figure 11-2) which then necessitates mask ventilation. Figure 11-7 algorithm demonstrates proper management in the difficult obstetric airway. This specific algorithm takes into account that not one, but two lives are at stake in the obstetric setting. Figure 11-8 demonstrates the importance of adhering to the difficult airway algorithm as greater than two intubation attempts can cause serious consequences. This results from tissue trauma with laryngoscope placement as well as airway edema from attempts at passing the endotracheal tube. Airway manipulation increases salivation, and bleeding may develop with airway trauma, further inhibiting the view of airway structures, making it increasingly more difficult to secure the airway.
 FIGURE 11-6 A “ramp” of blankets behind the shoulders and occiput of the parturient as seen before (A) and after (B) ramp placement helps place the patient in the sniffing position, which improves intubating conditions. (From Suresh M. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Philadelphia: Wolters Kluwer; 2013.) |
 FIGURE 11-7 Unexpected difficult airway algorithm in the obstetric patient. (From Suresh M. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Philadelphia: Wolters Kluwer; 2013.) |
In case of airway difficulty, it is imperative that the obstetric operating suite has emergency airway equipment readily available. This includes an assortment of endotracheal
tube sizes, with focus on smaller tubes. Laryngeal mask airways (LMAs) should be available as rescue devices. A video laryngoscope is essential and frequently the intubation equipment of choice in the obstetric setting. A difficult airway cart containing a fiberoptic scope should remain on the labor and delivery floor at all times. A cricothyroidotomy kit should be placed on the difficult airway cart should a surgical airway become necessary.
tube sizes, with focus on smaller tubes. Laryngeal mask airways (LMAs) should be available as rescue devices. A video laryngoscope is essential and frequently the intubation equipment of choice in the obstetric setting. A difficult airway cart containing a fiberoptic scope should remain on the labor and delivery floor at all times. A cricothyroidotomy kit should be placed on the difficult airway cart should a surgical airway become necessary.
 FIGURE 11-8 Visual representation demonstrating risk of increased intubation attempts. The chance of all listed potential complications increases with greater than two intubation attempts. (From Suresh M. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Philadelphia: Wolters Kluwer; 2013.) |
Adding to the increased difficulty of any pregnant airway, obesity results in anatomical changes due to increased fat in the breasts and neck. Placing towels behind the shoulders and occiput helps align the patient into sniffing position for intubation, as seen in Figure 11-9. A short-handled laryngoscope assists in laryngoscopy when the chest and breasts are obstructing access to the airway. As stated earlier in the chapter, additional airway equipment should be available including a video-assisted laryngoscope, an LMA, a bougie, a fiberoptic bronchoscope, oral airways, and an assortment of smaller endotracheal tube sizes.
PULMONARY CHANGES
Pulmonary changes during pregnancy for the obese patient include an exaggerated decrease in FRC and increase in oxygen consumption. These changes happen in addition to the normal lung changes of pregnancy shown in Figure 11-1. Both of the two mentioned changes contribute to dramatically shortening time to oxygen desaturation in an apneic patient during intubation. Another possible consequence of changes of lung volumes is that a decrease in FRC may make the FRC smaller than closing capacity, the volume at which airways close, leading to closure of dependent airways during tidal volume respirations pictured in Figure 11-10. The airway closure then results in increased shunt (perfusion without ventilation) fraction, which then leads to hypoxemia.
 FIGURE 11-9 An obese parturient with towels placed behind her shoulders and occiput to improve laryngoscopic view. (Used with permission Robert D’Angelo, MD, Wake Forest University Baptist Medical Center, Winston-Salem, North Carolina.) |
 FIGURE 11-10 Lung volumes in nonobese and obese patients, further demonstrating the effects of position on lung volumes. When closing capacity (CC) is greater than functional residual capacity (FRC), alveolar closure happens during tidal volume ventilations, therefore decreasing oxygenation. This figure also demonstrates how patient positioning in the obstetric operative suite can also affect lung volumes. (From Suresh M. Shnider and Levinson’s Anesthesia for Obstetrics. 5th ed. Philadelphia: Wolters Kluwer; 2013.) |
CARDIAC CHANGES
Cardiac changes compound the difficulty of a cesarean section for an obese patient. As stated above, obese individuals are at increased risk of other medical conditions such as hypertension which can lead to cardiac changes such as left ventricular hypertrophy and impaired diastolic function. Obese young adults have a 12-fold increase in
the risk of death from cardiovascular disease. This includes 25-to 34-year-olds; many parturients fall into this age group. Pregnancy further compromises cardiac status. Cardiac output may double, compared to the 35% to 45% increase for nonobese parturients.5 In addition, aortocaval compression occurs not only from the gravid uterus but from abdominal fat as well.
the risk of death from cardiovascular disease. This includes 25-to 34-year-olds; many parturients fall into this age group. Pregnancy further compromises cardiac status. Cardiac output may double, compared to the 35% to 45% increase for nonobese parturients.5 In addition, aortocaval compression occurs not only from the gravid uterus but from abdominal fat as well.
GASTROINTESTINAL CHANGES
For the gastrointestinal system, the most acute concern is aspiration, for which the risk increases. A decreased lower esophageal sphincter tone and delayed gastric emptying occur for all pregnant women, and these effects are exacerbated by an increased incidence of hiatal hernias and increased intragastric pressure in obesity. An H2 antagonist, metoclopramide, and sodium citrate all decrease morbidity if aspiration occurs.
ANATOMICAL CHANGES FOR NEURAXIAL PLACEMENT
Positioning for neuraxial anesthetic placement is challenging for almost all term parturients but can be especially difficult for morbidly obese parturients at term. New positioning devices are available which can assist morbidly obese parturients with safely assuming an ideal form for placement of neuraxial anesthetics; see Figure 11-11 for an example of a neuraxial positioning device. The anatomical landmarks can be difficult to palpate, making proper positioning even more important (Figure 11-12). Ultrasound can be helpful in finding the midline and estimating the depth of the epidural space.
DIFFICULT INTRAVENOUS LINE PLACEMENT
Intravenous (IV) line placement can be very difficult in a morbidly obese parturient. Many hospitals now utilize midlines in patients with difficult peripheral access. A midline is a peripheral catheter inserted under ultrasound guidance into a larger vein than is typically utilized for IV placement. These catheters are longer than standard IV catheters, and placement into larger veins decreases the risk of phlebitis as well as infiltration.6 If IV access proves to be difficult, an intraosseous (IO) line can be placed in an emergency.
CESAREAN SECTION ANESTHESIA FOR THE OBESE PARTURIENT
IMPORTANCE OF ANTEPARTUM CONSULTATION
Obese parturients should have a preanesthesia consultation at the start of their third trimester. This will give anesthesia providers an opportunity to obtain a detailed history and perform a physical examination as well as assess the airway. If further workup is deemed necessary, this provides plenty of time to obtain additional testing
and consultation with pulmonary or cardiology services. If the patient has a diagnosis of OSA, the use of continuous positive airway pressure (CPAP) should be discussed. CPAP may be required intraoperatively or postoperatively depending on severity of obstruction. Patients should be screened for OSA and sent for sleep studies, if necessary. If OSA is confirmed, CPAP should be initiated.1 This visit also provides an opportunity for the patient to talk about her options for analgesia or anesthesia. The anesthesiologist can provide counseling on the importance of requesting an epidural early in labor to facilitate better positioning and ensure a functioning catheter as the risk of cesarean section is increased. The anesthesia options for emergency versus elective cesarean section should be discussed during this visit as well.
and consultation with pulmonary or cardiology services. If the patient has a diagnosis of OSA, the use of continuous positive airway pressure (CPAP) should be discussed. CPAP may be required intraoperatively or postoperatively depending on severity of obstruction. Patients should be screened for OSA and sent for sleep studies, if necessary. If OSA is confirmed, CPAP should be initiated.1 This visit also provides an opportunity for the patient to talk about her options for analgesia or anesthesia. The anesthesiologist can provide counseling on the importance of requesting an epidural early in labor to facilitate better positioning and ensure a functioning catheter as the risk of cesarean section is increased. The anesthesia options for emergency versus elective cesarean section should be discussed during this visit as well.
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