Perioperative Protection of the Pregnant Woman

Introduction

Maternal safety surrounding nonobstetrical surgery, labor, and delivery has been seen as one of the greatest triumphs of 20th century medicine. Within living memory, nearly 1% of women in the United States died during or in the immediate aftermath of childbirth. As recently as 1900, maternal mortality was six to nine per 1000 live births, and of those 1000 births, 100 infants died before the age of 1 year. From 1900 through 1997, maternal mortality declined almost 99%, to less than 0.1 reported deaths per 1000 live births (7.7 deaths per 100,000 live births in 1997). Environmental interventions, improvements in nutrition, advances in clinical medicine, improvements in access to health-care, improvements in surveillance and monitoring of disease, increases in education levels, and improvements in standards of living contributed to this remarkable decline.

However, despite these significant improvements, a startling trend has arisen. Between 2000 and 2014, maternal mortality has steadily risen in the United States; the United States now has the highest maternal mortality among industrialized nations and is one of the only such nations to have a maternal mortality that continues to climb ( Fig. 29.1 ). Clearly, significant preventable causes of maternal death still persist. Here, we attempt to offer recommendations toward what authorities consider best practice in an effort to stem the tide and improve maternal morbidity and mortality in the perioperative and peripartum periods.

Causes of Maternal Morbidity and Mortality

Since 1952, the most thorough and reliable data on maternal mortality have come from the Confidential Enquiry into Maternal Death, now called Confidential Enquiry into Maternal and Child Health (CEMACH), and the Centers for Disease Control’s Maternal Mortality Survey. However, more recent data are available from the World Health Organization, with the most recent period covering data from 2003–2009 ( Fig. 29.2 ). The WHO reviewed a total of over 60,000 deaths from 115 countries. Among both developed and developing countries, obstetric hemorrhage remains the most common direct cause of maternal death, with rates of 16.3% and 27.1% of deaths respectively. The majority of hemorrhage deaths continue to occur in the postpartum period and do not appear to be decreasing in frequency worldwide. In developed nations, embolic events were the second-leading direct cause of death with hypertensive diseases third (13.8% and 12.9% respectively), and in developing regions, hypertensive diseases and sepsis (14% and 10.7%) were second and third. In both developed and d;eveloping regions, indirect causes of maternal death, primarily preexisting medical conditions, comprise a large proportion of all deaths (24.7% and 27.5% respectively).

Anesthetic Causes of Morbidity and Mortality

Serious anesthesia-related complications are thankfully rare in the perioperative and peripartum period. Historically, perioperative mortality fell significantly through the 1980s and 1990s, although it regressed slightly in the beginning of the 2000s to a rate of about 1 in 20,000. The overwhelming majority of these deaths were a result of failures in airway management: unidentified esophageal intubation and hypoventilation. Obesity, aspiration, and the lack of capnography were commonly associated with these deaths.

With the expansion of regional anesthesia use in these patients, the risk of anesthesia mortality has decreased significantly. The Society for Obstetric Anesthesia and Perinatology’s Serious Complications Repository Project reviewed more than 257,000 anesthetics between 2003 and 2009 and identified 157 serious complications, 85 of which were deemed to be anesthesia-related ( Fig. 29.3 ). No anesthesia-related deaths were reported in this group; however, comparatively common severe complications included failed intubation, with an incidence of 1:533 and high neuraxial block, with an incidence of 1:4336. Other routinely discussed complications of obstetric anesthesia were significantly less common: serious neurologic injury, with an incidence of 1:35,923, epidural abscess/meningitis, with an incidence of 1:62,866, and epidural hematoma, with an incidence of 1:251,423 are all comparatively rare.

Thromboembolism and Thrombophilia

Pregnancy and its hormonal changes are known to promote coagulation. Clotting factors increase with gestational age and, together with rapid myometrial contraction at delivery, help prevent excessive blood loss. Platelet production, consumption, and activation increase. Thromboelastography demonstrates accelerated clot formation, which further increases the risk of thromboembolism in pregnancy. Risk factors associated with maternal thromboembolism include older age, immobility, prolonged travel, surgery, family history, patient history, oral contraceptive use, and obesity. Risk factors for thromboembolism in pregnancy are outlined in Fig. 29.4 .

With the continually significant risk of embolic disease in pregnant patients, recent recommendations have widely expanded the use of thromboprophylaxis; the California Maternal Quality Care Collaborative’s Maternal Venous Thromboembolism Toolkit recommendations include significant expansions in the use of prophylactic and therapeutic heparins in the antepartum, peripartum, and postpartum periods.

Thrombophilia is emerging as an important cause of maternal thromboembolic risk. It is found in up to 17% of white North Americans. Thrombophilia can be divided into three general categories: familial, acquired, and mixed. Familial causes include protein C, protein S, and antithrombin III deficiencies, as well as factor V Leiden and prothrombin gene polymorphism. Conditions that increase the risk of thrombophilia include antiphospholipid antibodies and lupus anticoagulant. Mixed thrombophilia risk includes methylene tetrahydrofolate reductase polymorphism and hyperhomocysteinemia. Genetic thrombophilia is associated with other complications of pregnancy such as gestational hypertension, intrauterine growth restriction (IUGR), placental abruption, and stillbirth. In one study, 52% of women with severe gestational hypertension and associated problems also had thrombophilia. Preventing these thrombophilia-related side effects has proven to be difficult; antepartum dalteparin prophylaxis has shown no effect in preventing thromboembolic events, pregnancy loss, or placenta-mediated pregnancy complications in patients with thrombophilia in pregnancy.

Hypertensive Disorders of Pregnancy

Chronic hypertension complicates between 1% and 5% of pregnancies. It is defined as a blood pressure greater than 140/90 mmHg that either predates pregnancy or develops before 20 weeks of gestation. Gestational hypertension develops after 20 weeks of gestation and complicates between 5% and 10% of pregnancies. Gestational hypertension may reflect a familial predisposition to chronic hypertension or it may be an early manifestation of preeclampsia.

Preeclampsia is the most common disease that is unique to human gestation, occurring in 6% to 8% of pregnancies. In developed regions 12.9 % of deaths and 14% in developing regions were attributable to hypertensive disorders of pregnancy, most commonly preeclampsia. Diagnostic criteria are listed in Fig. 29.5 and include hypertension and symptoms of end-organ dysfunction.

The etiology is unknown, but the defining feature of preeclampsia is vasospasm affecting organs throughout the body. Cellular damage can be seen in endothelium, platelets, and trophoblasts. Vasoactive amines and prostaglandins are then released. Blood vessel narrowing and decreased elasticity are associated with increased vascular resistance. Women who become preeclamptic, unlike those with a normal pregnancy, do not lose sensitivity to angiotensin and catecholamines. Uterine Doppler studies show evidence of high vascular resistance and flow abnormalities.

An immune reaction involving trophoblast material and basement membrane, prostacyclin imbalance, and vascular nitric oxide dysfunction have all been suggested as important parts of the puzzle. A genetic analysis of its aspects is underway. General risk factors for the development of gestational hypertension can be found in Table 29.1.

As hypertensive disorders of pregnancy remain a significant cause of maternal morbidity and mortality, significant efforts have been made to improve, standardize, and expand appropriate and early care for gestational hypertension and preeclampsia. Core to these efforts are to standardize antepartum care and to monitor closely those at elevated risk of preeclampsia, early evaluation and treatment of all hypertension in pregnancy, early implementation of magnesium sulfate therapy for the treatment of preeclampsia, and improved education for patients and health-care professionals in both identification and treatment strategies.