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Anesthesia Considerations for Complicated Pregnancies
An estimated 1% to 3% (40,000 to 120,000) of pregnant women require critical care services in the United States each year. Most admissions are related to hemorrhage, hypertension, or cardiac disease. , When a woman requires any of the following procedures, she should be admitted to an intensive care unit (ICU): (1) respiratory support such as endotracheal intubation or treatment of pneumothorax, (2) cardiovascular support with pressors or inotropic agents, (3) placement and interpretation of pulmonary artery catheterization, and (4) abnormal electrocardiographic findings requiring interpretation or cardioversion. Necessary medications and procedures should not be withheld from a pregnant woman because of fetal concerns, with the exception of prolonged use of ACE inhibitors. The management of high-risk pregnancies requires a team approach with collaboration between obstetricians, perinatologists, anesthesiologists, nursing personnel, and appropriate consultant physicians.
A classification system for levels of maternal care has been proposed, similar to previously established levels of neonatal care. It describes regionalized maternal care for pregnant women at high risk, because “although specific supporting data are not currently available in maternal health, it is believed that concentrating the care of women with the most complex pregnancies at designated regional perinatal health care centers will … achieve optimal outcomes.” The need for a board-certified anesthesiologist, subspecialty care, and an ICU that accepts peripartum women was emphasized for hospitals providing a higher level of care.
Physiologic changes of pregnancy affect disease processes and their treatments, often prompting modification of care strategies that might have been employed in a nonpregnant patient ( Table 70.1 ). Serum levels of drugs and their effects may be altered during pregnancy. Normal values for laboratory tests may change over the three trimesters of pregnancy such that normal values for a nonpregnant patient may be significantly abnormal during pregnancy. Examples include serum creatinine, hematocrit, and arterial oxygen and carbon dioxide values. Anesthetic care of pregnant women will involve vaginal or cesarean delivery at some point in their course, and delivery may need to be performed emergently due to concerns about the mother or fetus. The well-being of both patients should always be part of the risk-benefit analysis informing treatment plans. Because anesthesiologists receive training in the care of parturients in labor and delivery units and gain extensive critical care experience during their residency and fellowship education, they are uniquely able to collaborate on the care of critically ill pregnant patients.
TABLE 70.1
Physiologic Changes of Pregnancy and Their Clinical Implications
| Physiologic Variables | Change | Clinical Implications |
|---|---|---|
| CARDIOVASCULAR | ||
| Blood volume | ↑40% | Hypervolemic |
| Plasma volume | ↑50% | Dilutional anemia |
| Heart rate | ↑15 beats/min | Mild tachycardia |
| Cardiac output | ↑40% | Increased cardiac work to handle increased volume |
| Systemic resistance | ↓20% | Maintains normal blood pressure with increased cardiac output and volume |
| Aortocaval compression | Varies | Loss of cardiac preload when supine |
| RESPIRATORY | ||
| Alveolar ventilation | ↑70% | Elevated arterial P o 2 |
| Minute ventilation | ↑50% (↑15% respiratory rate) | P co 2 reduced about 10 mm Hg, mild tachypnea |
| Functional residual capacity | ↓20% | Rapid desaturation with apnea |
| Metabolic rate | ↑20% | Rapid desaturation with apnea |
| Mucosal edema, friability | Varies | Difficult intubation increases 10-fold |
| HEMATOLOGIC | ||
| Coagulation status | Prothrombotic | Risk of deep venous thrombosis and embolism |
| Hemoglobin, hematocrit | Anemic | Dilutional cause rather than iron deficiency or blood loss |
| GASTROINTESTINAL AND RENAL | ||
| Lower esophageal sphincter tone | Reduced | Reflux symptoms, potential aspiration risk, but normal gastric emptying |
| Renal blood flow and glomerular filtration rate | ↑50% | Serum creatinine decreases to 0.5–0.6 mg/dL |
| Aldosterone levels | Increased | Sodium and water retention |
| Albumin levels | Decreased | Decreased oncotic pressure leads to increased risk of pulmonary edema with increased intravascular volume or endothelial leak |
| NEUROLOGIC | ||
| Minimum alveolar concentration | ↓30%–40% | Lower requirement for volatile anesthetics during general anesthesia |
| Local anesthetic requirement | ↓30% | Use lower spinal and epidural doses |
P co 2 , Partial pressure of carbon dioxide; P o 2 , partial pressure of oxygen.
This chapter focuses on anesthesia considerations for the management of selected conditions complicating pregnancies during the intrapartum and immediate postpartum periods. More extensive discussions of each disease can be found elsewhere in this textbook.
Maternal Morbidity and Mortality Trends
The US Centers for Disease Control and Prevention (CDC) report on trends in pregnancy-related deaths in the United States from 2014 to 2017 showed that pregnancy-related deaths have increased from 7.2 per 100,000 in 1987 to 17.3 deaths per 100,000 live births in 2017. Considerable racial and ethnic disparities in mortality exist, with maternal mortality ranging from 11.6 deaths per 100,000 live births for Hispanic or Latina women to 41.7 deaths per 100,000 live births for non-Hispanic Black women. Deaths due to cardiovascular causes, cerebrovascular accidents, and other medical conditions have increased, while deaths from hemorrhage, hypertensive disorders, embolism, and anesthesia complications have declined. For deaths occurring after a live birth (compared with stillbirth, ectopic pregnancy, or abortion), indirect cardiovascular and medical causes predominate. The most common causes were cardiovascular conditions (15.5% of maternal deaths), infection (12.7%), noncardiovascular medical conditions (12.5%), and cardiomyopathy (11.5%). The other leading causes of maternal death were hemorrhage (10.7%), thrombotic pulmonary or other embolism (9.6%), cerebrovascular accident (8.2%), and preeclampsia/eclampsia (6.6%) ( Table 70.2 ).
TABLE 70.2
Causes of Pregnancy-Related Death in the United States, 2014–2017
Modified from Centers for Disease Control and Prevention. Pregnancy mortality surveillance system. https://www.cdc.gov/reproductivehealth/maternal-mortality/pregnancy-mortality-surveillance-system.htm . Accessed March 18, 2022.
| Causes of Death After Live Birth a | Percent (%) of Total Deaths |
|---|---|
| Other cardiovascular conditions | 15.5 |
| Infection or sepsis | 12.7 |
| Other noncardiovascular medical conditions | 12.5 |
| Cardiomyopathy | 11.5 |
| Hemorrhage | 10.7 |
| Thrombotic pulmonary or other embolism | 9.6 |
| Cerebrovascular accidents | 8.2 |
| Hypertensive disorders of pregnancy | 6.6 |
| Amniotic fluid embolism | 5.5 |
| Anesthesia complications | 0.4 |
a Compared with stillbirth, ectopic pregnancy, or abortion. The cause of death is unknown for 6.7% of all 2014–2017 pregnancy-related deaths.
The United Kingdom’s Centre for Maternal and Child Enquiries audit of maternal mortality for 2015 through 2017 found that their overall maternal mortality rate fell slightly but improvements in care could have made even more of a difference in outcome in 20% of cases. Leading causes of death in the United Kingdom and Ireland associated with pregnancy were heart disease (23%), thromboembolism (16%), epilepsy and stroke (13%), other medical conditions (11%), sepsis (10%), mental health conditions (10%), hemorrhage (8%), cancer (4%), and hypertensive disorders (2%). As in the United States, they also found large racial disparities, including a five fold increase in maternal mortality rates among Black women compared to White women. Interestingly, their review from 2009 to 2012 found that of the women who died, 68% died from medical and mental health problems versus only 32% from direct complications of pregnancy. The authors emphasized the multifactorial causes of death, the need for multidisciplinary review of all deaths, and the importance of including an anesthesiologist in all investigations. Specific to anesthesiology, they emphasized the value of practicing airway drills, including managing bronchospasm, maintaining postoperative standards in the postanesthesia care unit, and prompt action with good communication between teams during unexpected catastrophes. They also noted that early warning systems should be implemented, followed, and audited for actions. While mothers in the United States are becoming older, heavier, and perhaps sicker, at least 40% of maternal morbidity and mortality is deemed preventable. Data from California found that 70% of deaths due to hemorrhage were preventable and 60% of deaths due to preeclampsia were preventable, the highest rates of preventable death from any cause.
Mortality is only a small portion of adverse maternal outcomes. In a review of more than 32 million deliveries between 1998 and 2006, rates of severe obstetric morbidity were found to have increased. These authors found that rates of mechanical ventilation, adult respiratory distress syndrome, renal failure, shock, pulmonary embolism, and blood transfusion all increased over the time period studied, while cesarean delivery rates also increased from 21% to 30%. Much of the morbidity was related to performance of more cesarean deliveries. Another review using the Nationwide Inpatient Sample examined near-miss morbidity, defined as end-organ injury associated with length of stay greater than the 99th percentile or discharge to a second medical facility from 2003 through 2006 to determine maternal characteristics predicting parturients at risk. The highest rates of morbidity or death were found among women with pulmonary hypertension, malignancy, and lupus, but many other preexisting conditions and antenatal obstetric complications, such as placenta accreta, put women at risk. The investigators suggested convening a multidisciplinary care conference for such patients before delivery in an effort to reduce poor outcomes. One institution reviewed all deliveries over 18 months for evidence of severe morbidity using the following criteria: prolonged length of stay, ICU admission, transfusion of 4 or more units of packed red blood cells, or hospital readmission within 30 days. They found 0.9% of cases had true severe maternal morbidity, with hemorrhage and preeclampsia being the most common causes. There were opportunities to improve care in 44% of cases with opportunities/gaps distributed among provider factors (79%), patient factors (29%), and system factors (14%).
Improving Patient Safety
Patient safety requires teamwork and open communication. A national survey of labor and delivery personnel asked whether they had experienced any of four patient safety concerns: dangerous shortcuts, missing competencies, disrespect, or performance problems. Although 92% of physicians and 98% of nurses said yes, only 9% of physicians, 13% of midwives, and 13% of nurses had shared their concerns with the person involved, indicating a culture of organizational silence. Studies from several institutions have shown that implementing comprehensive obstetric patient safety programs can lead to significant improvements in multiple metrics, including improved workforce perceptions of safety and an improved patient safety climate, while also decreasing sentinel events and reducing liability payments, a significant savings for the institution. These safety programs focus on crew resource management training and often involve multidisciplinary simulations of rare events. Yale–New Haven Hospital implemented a comprehensive obstetric patient safety program and later reviewed liability claims for 5 years before and 5 years after the program was in place. Median annual claims dropped in half from 1.31 to 0.64 and median annual payments per 1000 deliveries decreased sharply from $1,141,638 to $63,470. In contrast, the surrounding insurance market experienced stable claims and increased cost per claim during the same period. Obstetric patients expect and deserve maximal safety and optimal communications. All labor and delivery units should implement simulation drills and communication interventions, adapted to their individual needs and resources.
Management of Individual Conditions
Amniotic Fluid Embolism
Amniotic fluid embolism (AFE) is difficult to study and document because of its rare, sporadic, and unpredictable nature. As a spectrum disorder, manifestations can range from subclinical to fatal, making its incidence difficult to ascertain as well. A working group under the auspices of a committee of the Society for Maternal-Fetal Medicine and the Amniotic Fluid Embolism Foundation developed uniform diagnostic criteria for research on AFE to avoid overdiagnosis and confusion with other medical conditions. They proposed a diagnostic triad of hemodynamic and respiratory compromise accompanied by strictly defined disseminated intravascular coagulopathy and established a registry to collect clinical information and laboratory specimens in the hopes of identifying unique biomarkers.
Currently, AFE can be neither predicted nor prevented. It is not precisely an embolism nor amniotic fluid related, although the timing suggests a breach between the normal physiologic barrier of the mother and fetus with an abnormal maternal response to fetal tissue exposure. Early recognition and aggressive resuscitation are critical to management. The clinical picture is similar to the systemic inflammatory response syndrome and to anaphylaxis, but the diagnosis is purely clinical and treatment is supportive. Early intubation and ventilation with 100% oxygen and positive end-expiratory pressure are needed to correct hypoxia. High-quality cardiopulmonary resuscitation (CPR) should be immediately initiated for cardiac arrest, which occurs commonly during AFE. If AFE occurs before delivery, cesarean delivery should be performed to improve resuscitation of the mother and survival of the fetus. Large-bore intravenous access and arterial line placement are needed to treat and monitor hemorrhage and coagulopathy. After intubation, transesophageal echocardiography may be helpful to manage pulmonary hypertension and cardiac failure with pressors, inotropes, or pulmonary vasodilators. Consider extracorporeal membrane oxygenation (ECMO) after prolonged arrest or severe ventricular dysfunction unresponsive to medical management. ,
Blood products, including packed red blood cells, fresh-frozen plasma (FFP), and platelets in a 1:1:1 ratio, are used to resuscitate the patient and treat coagulopathy. Point-of-care testing such as thromboelastography (TEG) or rotational thromboelastometry (ROTEM) may be helpful in determining the best ratio of transfusion products. Such tests provide a global assessment of hemostasis in whole blood that includes contributions of platelets, fibrinogen, fibrinolysis, and coagulation factors. They can be performed at the bedside so results are available within minutes and products can be administered to address specific deficiencies. This strategy has been shown to reduce total allogeneic blood product administration. Coagulopathy is likely related to uteroplacental-derived tissue factor similar to that seen with placental abruption. As in severely ill patients with trauma, burns, or sepsis, there may be impaired clearance of circulating microaggregates and immune complexes, leading to hemodynamic instability and coagulopathy. Use of recombinant activated factor VIIa during treatment of AFE is controversial, because a systematic review of case reports found that its use during coagulopathy and hemorrhage associated with AFE led to worse outcomes due to major organ thrombosis and death.
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