M. Margaret Knudson and Daniel Dante Yeh
Penetrating injuries to the gravid uterus date back to antiquity, when wounding instruments included spears, sticks, and animal horns. Ambroise Paré, famous for his skills as a military surgeon, was also an obstetrician and was among the first to describe the treatment of gunshot wounds to the uterus. Paré wrote, “When the womb is wounded, the blood cometh out at the privites, and all other accidents appeared …”1 Maternal deaths resulting directly from pregnancy or the complications of labor and delivery have declined sharply in recent years. In the United States, the absolute risk of pregnancy-related death is estimated currently at 11.8 deaths per 100,000 live births, a reduction in death rate by 99% since 1900.2,3 In contrast, trauma has emerged as the leading cause of death during pregnancy, accounting for nearly 50% of maternal deaths in the United States and over 1 million deaths annually worldwide.3,4An estimated 6–7% of pregnancies are complicated by trauma with 0.4% of all pregnant patients requiring hospitalization for the treatment of injuries.5 Interestingly, the incidence of trauma increases with each pregnancy trimester, with only 8% of injuries occurring during the first trimester and over 50% during the third trimester.6 The true number of injured gravid women is grossly underestimated by these figures, however, as many injuries are unreported, especially those resulting from domestic violence. Thus, it is essential that all trauma care professionals recognize the anatomic and physiologic changes unique to pregnancy and appreciate how these changes impact the evaluation and treatment of the injured gravid patient. Complete evaluation of these patients includes an assessment of the fetus, and the treating physician must not only be cognizant of the signs of fetal distress, but must also be able to make rapid interventions in the interest of saving both mother and baby.
EPIDEMIOLOGY OF TRAUMA IN PREGNANCY
Weiss et al.7 examined data from the Pennsylvania state trauma registry and found that, among a total of 16,722 women of childbearing age who required hospitalization for injuries over a 1-year period, 761 were pregnant (4.6%). The leading causes of injury among pregnant women in this series were transportation-related (33.6%), falls, and assaults. Younger women (mean age 25) appeared to be at higher risk for injuries when compared to older gravid women. In a recent study from the state of Utah, pregnant women with an injury-related visit to an emergency department (ED) were more likely than noninjured women to experience preterm labor, placental abruption, and cesarean delivery, and infants born to women who were injured were more likely to be born preterm.8 In a related study that included data from 16 states, 240 trauma-related fetal deaths were identified (3.7 fetal deaths per 100,000 live births).9 Motor vehicle crashes were again the leading mechanism resulting in fetal death (82% of cases), followed by firearms (6%) and falls (3%). Placental injury was mentioned in 100 cases, and maternal death was the cause of fetal death in 11% of the cases. Again, pregnant mothers ages 15–19 years appeared to be at greatest risk for trauma-related fetal loss.
Young pregnant women are at significant risk of sustaining injuries as the result of an assault also. Battering can begin or escalate during pregnancy, and it is estimated that between 10 and 30% of women are abused during pregnancy, with fetal death occurring in 5%.10 In a series of 41 injury-related deaths during pregnancy reported from North Carolina, half of the patients were known or suspected of having been abused.11 Physical abuse is suggested by proximal and midline injuries rather than distal injuries, trauma to the neck, breast and face, and injuries to the upper arms and lateral thighs. Cigarette burns and bites should raise the level of suspicion for the examiner also.12 A history of depression, substance abuse, or frequent visits to the ED are other factors that suggest domestic violence. Domestic violence is not dependent on age, race, or marital status and cuts across all socioeconomic classes. Thus, it is imperative that all health care providers recognize the signs and symptoms of physical abuse and the opportunity to intervene and protect both the mother and her fetus (see Chapter 46).
Chang et al.13 recently summarized data from the Pregnancy Mortality Surveillance System at the Centers for Disease Control and Prevention (CDC), focusing on risk factors for pregnancy-associated homicide. According to this report, homicide was the third leading cause of injury-related death for all women of childbearing age, pregnant or not. The pregnancy-associated homicide ratio was 1.7 per 100,000 live births. Risk factors for homicide in this group included age younger than 20 years, black race, and either late or no prenatal care, and firearms were the leading mechanism (56.5%). It is hoped that the new surveillance system developed by the CDC, the National Violent Death Reporting System, which captures information about pregnancy status, victim–perpetrator relationships, and the presence of intimate partner violence, will provide more comprehensive data on this important mechanism of injury among women. Ikossi et al.14 utilized the American College of Surgeons’ National Trauma Data Bank (NTDB) to develop a profile of mothers at risk for injury during pregnancy. Among the 77,321 women of childbearing age who were hospitalized after injury, 1,195 (1.5%) were pregnant. The major mechanism of injury among the pregnant patients was a motor vehicle crash (70%), followed by interpersonal violence (11.6%) and falls (9.3%). Young age, African American or Hispanic ethnicity, and insurance status (none or underinsured) identified women at highest risk for injury during pregnancy, and these groups are most likely to benefit from efforts at primary trauma prevention (see below).
ANATOMIC AND PHYSIOLOGIC CHANGES UNIQUE TO PREGNANCY
Although the initial assessment and management priorities for resuscitation of the injured pregnant patient are the same as those for other traumatized patients (see Chapter 10), the specific anatomic and physiologic changes that occur during pregnancy may alter the response to injury and, hence, necessitate a modified approach to the resuscitation process. Most of these anatomic, physiologic, and biochemical adaptations occur in response to physiologic stimuli provided by the fetus. An understanding of these adaptations (summarized in Table 37-1) is necessary in order to provide appropriate and timely care to both mother and unborn child. Although nearly every system in the body is affected by pregnancy, the most important changes involve the cardiovascular, pulmonary, and reproductive systems.
TABLE 37-1 Summary of Normal Physiologic Changes During Pregnancy
Plasma volume begins to expand at 10 weeks’ gestation and increases by 45% at full-term as compared to pregravid levels.15 This hypervolemic state is protective for the mother, as fewer red blood cells are lost during hemorrhage and, hence, the oxygen-carrying capacity of her blood is less affected.16 Furthermore, the hypervolemia prepares the patient for the blood loss that accompanies a vaginal delivery (500 mL) or cesarean section (1,000 mL). This pregnancy-induced hypervolemia, however, may create a false sense of security for the resuscitating physician because almost 35% of maternal blood volume may be lost before there are signs of hypovolemic shock. This increase in plasma volume is accompanied by an erythroid hyperplasia in the bone marrow, resulting in a 15% increase in red blood cell mass and a “physiologic anemia.” This anemia of pregnancy is greatest at 30–32 weeks’ gestation and will be most significant in patients who have not received iron supplements.16 In addition, factors VII, VIII, IX, X, and XII, and fibrinogen are increased, fibrinolytic activity is reduced, and the net result is a hypercoagulable state, putting the patient at increased risk for thromboembolic events.
During the first trimester, maternal pulse rate increases by about 10–15 beats/min and remains elevated until delivery. As the diaphragm becomes progressively more elevated secondary to the enlarging uterus, the heart is displaced to the left and upward, resulting in a lateral displacement of the cardiac apex. Moreover, each pregnant woman has some degree of a benign pericardial effusion. Both of these changes result in an enlarged cardiac silhouette and increased pulmonary vasculature on the chest x-ray.17 Maternal blood pressure decreases during the first trimester, reaches its lowest level in the second trimester, and then rises toward pre-pregnancy levels during the final 2 months of gestation. The mean blood pressure values are 105/60 mm Hg for the first trimester, 102/55 mm Hg for the second trimester, and 108/67 mm Hg for the third. By the end of the first trimester, cardiac output increases to 25% above normal. In the healthy gravida, this increased workload on the heart is well-tolerated.
When the patient is in the supine position and the inferior vena cava is partially obstructed by the gravid uterus, there is a decrease in blood return to the heart resulting in a lower cardiac output and causing the “supine hypotensive syndrome.” This syndrome is marked by dizziness, pallor, tachycardia, sweating, nausea, and hypotension. Turning the mother onto her left side restores the circulation and increases cardiac output by about 30% after 20 weeks’ gestation. A point worth emphasizing is that in the supine position, the enlarged uterus also compresses the aorta, reducing the pressure in the uterine arteries and decreasing blood flow to the fetus.18 Importantly, the uterine arteries are maximally dilated during pregnancy so that autoregulation is absent and thus blood flow to the fetus is entirely dependent upon maternal mean arterial blood pressure.6
Several changes in the maternal respiratory system occur during pregnancy to meet increased oxygen requirements. As the uterus enlarges, the diaphragm rises about 4 cm and the diameter of the chest enlarges by 2 cm, increasing the substernal angle by 50%.19 Care should be taken to consider these anatomic changes when thoracic procedures such as tube thoracostomies and thoracenteses are being performed. Functional residual capacity (FRC) decreases because of a decline in expiratory reserve and residual volumes. The net result is an unchanged arterial partial pressure of oxygen (PaO2), a reduction in the partial pressure of carbon dioxide (PCO2) to 30 mm Hg, and a slight compensatory decrease in plasma bicarbonate levels.20 Therefore, pregnancy is a state of partially compensated respiratory alkalosis. Relative to these changes, the injured gravida tolerates apnea poorly because of the reduced FRC. Hence, supplemental oxygen is always indicated for these patients. Due to the weight gain associated with pregnancy, the Mallanpati score increases, making intubation more difficult and increasing the incidence of fatal failed intubation by 13 times.21,22
By the end of full-term gestation, the weight of the uterus has increased to 20 times its prepregnancy weight (i.e., from 60 to about 1,000 g). After the 12th week of pregnancy, the uterus extends out of the pelvis, rotates slightly to the right, and ascends into the abdominal cavity to displace the intestines laterally and superiorly. At 10 weeks’ gestation, uterine blood flow is estimated to be about 50 mL/min. With progressive uterine enlargement, uterine blood flow increases dramatically to approximately 500 mL/min at term, constituting up to 17% of the cardiac output.23 Uterine veins may dilate up to 60 times their size in the pre-pregnant state, allowing for adequate venous drainage to accommodate the uteroplacental blood flow. This increased vascularity carries an attendant risk of massive blood loss with a pelvic injury.
INITIAL ASSESSMENT AND MANAGEMENT
Prehospital care is an extension of the trauma system (see Chapter 4) and must be appropriately adapted to the needs of the injured gravid patient. In particular, the importance of providing an adequate airway and supplemental oxygen to prevent fetal hypoxia must take priority during field transport. Also, it is important to recognize that the relative hypervolemia of pregnancy may mask the usual signs and symptoms of acute blood loss. Thus, intravenous fluids should be given liberally during transport in these patients. A wedge placed under the right hip may help avoid the vena cava compressive syndrome described above. Any information on the length of the gestation and prenatal care and complications that can be obtained should be relayed to the receiving trauma center.
As with any other injured patient, the primary survey of the injured pregnant patient addresses the airway, breathing, and circulation, with the mother receiving treatment priority (see Chapter 10). Ensuring an adequate maternal airway with supplemental oxygen is essential for preventing maternal and fetal hypoxia (see Chapter 11). Because the oxyhemoglobin dissociation curve for fetal blood is different from that for maternal blood, small increments in maternal oxygen concentration improve the blood oxygen content and reserve for the fetus, even though the maternal arterial oxygen content does not change appreciably. Of note, because pseudocholinesterase levels decrease during pregnancy, lower doses of succinylcholine may be used during rapid sequence intubation.24 As mentioned above, due to the expansion of the intravascular volume, signs of shock in the mother may be delayed until over 35% of blood loss has occurred; however, the fetus will be in jeopardy before this point. Thus, fluid and blood resuscitation should be vigorous. In late pregnancy, it is wise to refrain from the use of femoral catheters for resuscitation. Although the role of ED thoracotomy in pregnancy remains to be defined, it is the opinion of the authors that it should be considered in conjunction with perimortem cesarean section (see below).25
Secondary Survey and Maternal Assessment
Following the primary survey of the patient and performance of life-saving measures, the secondary survey is initiated. This consists of obtaining a thorough history, including an obstetric history. An accurate prenatal history is crucial because comorbid factors such as pregnancy-induced hypertension, diabetes mellitus, and congenital heart disease may alter management decisions. Furthermore, a history of preterm labor, placental abruption, or placenta previa puts the patient at increased risk for the recurrence of these conditions. The obstetric history includes the date of the last menstrual period, expected date of delivery, and date of the first perception of fetal movement, and any problems or complications of the current and previous pregnancies. Whenever possible, the obstetrical team should be immediately notified and respond to the trauma room for patients in their second or third trimester of pregnancy.
During the secondary survey, appropriate x-rays should be ordered as during any trauma evaluation, shielding the uterus whenever possible (see below). The Focused Assessment with Sonography in Trauma (FAST) examination (see Chapter 16) is strongly recommended during the secondary survey to detect pericardial or peritoneal fluid in the mother. Although there is some debate on the sensitivity of ultrasound in this setting, most report an 80% sensitivity and a 100% specificity in detecting fluid using the FAST examination during pregnancy.26 A small amount of free fluid in the pelvis may be normal during pregnancy, but this trace amount (7–21 mL) is too small to be detected during a routine transabdominal ultrasound examanition.27 Therefore, any amount of fluid seen on the FAST examination should be considered pathologic even during pregnancy.
As part of the abdominal examination, determination of the uterine size provides an approximation of gestational age and fetal maturity. Measurement of fundal height is a rapid method for estimating fetal age. If, for example, the most superior part of the fundus is palpated at the umbilicus, the fetal age is estimated to be 20 weeks. A discrepancy between dates and uterine size may result from a ruptured uterus or intrauterine hemorrhage. Determination of fetal age and fetal maturity is an important factor in the decision matrix regarding early delivery. In general, a 25-week-old fetus is considered viable if given neonatal intensive care. Fig. 37-1 contains a helpful algorithm summarizing the initial evaluation of the injured pregnant patient.
FIGURE 37-1 Algorithm for the initial evaluation and resuscitation of the injured mother and fetus.
Evaluation of the Fetal–Placental Unit
Evaluation of the state of the pregnancy focuses on the following: (a) vaginal bleeding; (b) ruptured membranes (amniotic sac); (c) a bulging perineum; (d) the presence of contractions; and (e) an abnormal fetal heart rate (FHR) and rhythm. These five conditions indicate the acute status of the pregnancy. Vaginal bleeding prior to labor is abnormal and may indicate premature cervical dilation, early labor, placental abruption (separation of the placenta from the uterine wall), or placenta previa (location of the placenta over a portion of the cervical os). A ruptured amniotic sac should be suspected when cloudy white or green fluid is observed coming from the cervical os or perineum. The presence of amniotic fluid can be confirmed by the change in color of nitrazine paper from blue–green to deep blue when the fluid is tested. Rupture of the amniotic sac is significant because of the potential for infection and prolapse of the umbilical cord, the latter being an obstetric emergency requiring immediate cesarean section. Bloody amniotic fluid is an indication of premature separation of the placenta (placental abruption) or placenta previa. In the presence of known or continuous meconium staining (green amniotic fluid), continuous electronic fetal monitoring is necessary. A bulging perineum is caused by pressure from a presenting part of the fetus. If this occurs during the first trimester, spontaneous abortion may be imminent.
Assessment of the pattern of uterine contraction is accomplished by resting the hand on the fundus and determining the frequency, duration, and intensity of contractions. Contractions are usually rated as mild, moderate, or strong. Strong contractions are associated with true labor, and assessment for their presence is important so that appropriate preparation can be made for delivery and resuscitation of the neonate if necessary.
The Kleihauer–Betke (KB) test is used after maternal injury to identify fetal blood in the maternal circulation (i.e., fetomaternal transfusion). Adult hemoglobin (HbA) is eluted in the presence of an acidic buffer, whereas fetal hemoglobin (HbF) is resistant to elution. Fetal cells containing HbF are stained with erythrosine, whereas maternal cells containing HbA fail to stain and remain as “ghost cells” in the peripheral smear. Because the KB test can determine the risk of isosensitization in Rh-negative gravidas, it is recommended for detecting imminent fetal exsanguination in injured pregnant patients who are Rh-negative in the second or third trimester. If positive, the KB test should be repeated after 24 hours to identify ongoing fetomaternal hemorrhage. The initial dose of Rh-immune globulin is 300 μg, with an additional 300 μg given for every 30 mL of fetomaternal transfusion estimated by the KB test. Although the KB test is a very sensitive marker for even a small amount of fetomaternal transfusion, its clinical utility in Rh-positive mothers is uncertain.28 Indeed, the usefulness of the KB test after injury has been challenged recently by several authors. Authors from the R Adams Cowley Shock Trauma Center in Baltimore reported that among 46 injured women who were KB-positive on admission, 44 had documented contractions.29 In that study, KB testing accurately predicted the risk of preterm labor after maternal trauma, whereas clinical assessment was insensitive in identifying women at risk for this complication. On the other hand, a recent study from Cincinnati documented that 5% of low-risk women had a positive KB test, compared to only 2.6% of injured patients.30 None of these positive results were associated with a clinical abruption or fetal distress. The authors concluded that the presence of a positive KB test alone does not necessarily indicate pathologic fetal–maternal hemorrhage in patients with trauma, and that its routine use after injury should be abandoned.31
Unfortunately, direct assessment of the fetus following trauma is somewhat limited. Currently, the most valuable information regarding fetal viability can be obtained by a combination of monitoring of the FHR and ultrasound imaging. Fetal heart tones can be detected with a Doppler device around the 12th week of pregnancy. The normal FHR is between 120 and 160 beats/min. Because the fetal stroke volume is fixed, the initial response to the stress of hypoxia or hypotension is tachycardia. Severe hypoxia in the fetus, however, is associated with bradycardia (FHR <120 beats/min) and should be recognized as fetal distress, demanding immediate attention. Initial FHR monitoring of all pregnant patients with potentially viable pregnancies (i.e., those that would survive if emergency delivery was required) is indicated, even following relatively minor abdominal trauma. This monitoring is best accomplished using cardiotocographic (CTM) devices, which record both uterine contractions and FHR. A lack of variability in heart rate may also indicate fetal distress, and if there is no response to conservative measures such as fluid administration, increasing inspired oxygen, or change in maternal position, an emergency delivery should be considered (Fig. 37-2).
FIGURE 37-2 (A) Cardiotocographic strip demonstrating poor beat-to-beat variability in the fetus. (B) Return of beat-to-beat variability after resuscitation; variable decelerations with uterine contractions are within normal limits.
Blunt trauma to the abdomen can result in uterine rupture, but this event is uncommon, unlikely to be missed, and usually rapidly fatal for the fetus. A much more common event is placental separation from the uterus as the result of the shearing forces following blunt injury. This separation is termed placental abruption. Major cases of placental abruption (i.e., >50% separation) are uniformly fatal for the fetus, but more minor cases may initially go undetected. Vaginal bleeding is an unreliable sign of placental abruptions, occurring in only 35% of cases.25 On the other hand, in patients with placental abruption following trauma, CTM will detect early fetal distress, often manifested as a decelerated heart rate associated with uterine contractions. Most cases of placental abruption become evident within several hours of trauma, although late cases have been reported.25,32,33 A minimum of 24 hours of CTM is recommended for patients with frequent uterine activity (≥6 contractions per hour), abdominal or uterine tenderness, vaginal bleeding, or hypotension.34 A study of 271 pregnant patients who had sustained blunt trauma identified the following risk factors for fetal loss: ejections, motorcycle and pedestrian collisions, maternal tachycardia, abnormal FHR, lack of restraints, Injury Severity Score (ISS) >9, gestational age >35 weeks, and a history of assaults.35Patients with any of these risk factors should be monitored for at least 24 hours. In the absence of these factors, asymptomatic trauma patients should undergo at least 6 hours of CTM prior to considering discharge. These patients should be counseled to observe for decreased fetal movement, vaginal bleeding, abdominal pain, or frequent uterine contractions, as partial placental lacerations have been reported to progress over time.36
High-resolution real-time ultrasonography (US) has proven valuable for the assessment of fetal age and well-being, recognition and categorization of fetal abnormalities, and treatment of disease processes in the unborn patient. In the trauma setting, US is used primarily to identify acute problems that may be due to maternal events such as placental abruption, placenta previa, or cord prolapse. Although placental abruption is difficult to detect, US can accurately locate the lower margin of the placenta and its relation to the cervical os, hence demonstrating placenta previa.37 Additionally, it is routine to evaluate the fetus for gestational age, cardiac activity, and movement. In a study of 216 patients with high-risk pregnancies, fetal biophysical profile scores corresponded well with perinatal outcome.38 US findings consistent with uteroplacental injury may include oligohydramnios secondary to uterine injury or ruptured membranes. Oligohydramnios should be suspected if less than a 1-cm layer of amniotic fluid surrounds the fetus.
Following the secondary survey and the initial assessment of the fetus, appropriate diagnostic studies should be utilized to fully evaluate the extent of maternal injuries. Although there is much concern about radiation exposure during pregnancy, a diagnostic modality deemed necessary for maternal evaluation should not be withheld on the basis of its potential hazard to the fetus. There are three phases of radiation damage related to the gestational age of the fetus.39 During preimplantation and early implantation (less than 3 weeks’ gestational age), exposure to radiation can result in death of the embryo. During organogenesis (from 316 weeks’ gestation), radiation can damage the developing fetal tube and results in the associated anomalies of exencephaly, dysraphism, single cerebral ventricle, hydrocephaly, and the hypoplastic brain syndrome. Skeletal and genital abnormalities, retinal pigmentation, and cataracts are associated with radiation received during the third and eleventh weeks of gestation. After 16 weeks, neurologic defects are the most common complications of radiation exposure, due to the sensitivity of neuroblasts, which persist in the human embryo from 16 days postconception to about 2 weeks after birth.39 Prenatal x-ray exposure may also be associated with the later development of childhood cancers.40
Most of the human data on exposure to radiation is based on the large doses received in an atomic bomb blast (which includes neutrons and gamma ray), rather than on doses applied during normal diagnostic (x-ray) studies. The rad is the unit of measurement for absorbed radiation and corresponds to an energy transfer of 100 erg/g of tissue. Absorbed radiation is expressed in Gray (Gy) units, with 1 Gy equal to 100 rad. The dose to the uterus/fetus from x-ray procedures depends on several factors, including the x-ray tube potential, the current, the exposure time, the size of the patient, the type of procedure, the source-to-film distance, and the type of x-ray generator (Table 37-2). It is estimated that the fetal radiation dose without shielding is 30% of that to the mother.
TABLE 37-2 Estimated Fetal Exposure From Some Common Radiologic Procedures
The American College of Obstetricians and Gynecologists (ACOG) has produced a consensus statement on the use of diagnostic imaging during pregnancy.41 The authors emphasize the fact that most diagnostic radiologic procedures are associated with little, if any, known significant fetal risk. Specifically, exposure of the fetus to less than 5 rad has not been associated with an increase in fetal anomalies or pregnancy loss. A plain x-ray generally exposes the fetus to very little radiation, and the uterus is shielded for nonpelvic procedures during pregnancy. With the exception of a barium enema or small bowel series, most fluoroscopic examinations result in fetal exposure of just millirads. Radiation exposure from CT varies depending on the number and spacing of adjacent image sections (see Table 37-2). CT pelvimetry can result in fetal exposures as high as 1.5 rad but can be reduced by using a low-exposure technique as outlined by Moore and Shearer.42 Radiation exposure using helical CT is affected by slice thickness, the number of cuts obtained, and the pitch (a ratio defined as the distance the couch travels during one 360° rotation divided by the section thickness). Thus, CT can be used, when indicated to diagnose both maternal and fetal injuries as well as evaluating the placenta.
In summary, the ACOG Committee recommends the following:
• Women should be counseled that x-ray exposure from a single diagnostic procedure does not result in harmful fetal effects. Exposure to less than 5 rads is not harmful to the fetus or the pregnancy.
• Concern about possible effects of high-dose ionizing radiation should not prevent medically indicated diagnostic x-ray procedures from being performed during pregnancy.
• Other imaging procedures not associated with ionizing radiation, such as US or magnetic resonance imaging, which are not associated with known adverse fetal effects, should be utilized when appropriate.
• Consultation with an expert in dosimetry calculation may be helpful when multiple diagnostic x-rays are required.41
For a more complete review of the effects of ionizing radiation in pregnancy, readers are referred to the recent publications by De Santis et al.43 and Mann et al.44 For the injured patient, the following guidelines are suggested:
1. The minimum number of x-rays should be ordered to obtain the maximum information. Careful planning prevents duplication.
2. The patient’s abdomen should be shielded with a lead apron. This reduces fetal exposure by a factor of 8.
3. When many x-rays are required over a long period, a thermoluminescent dosimeter or “radiation badge” may be attached to the patient to serve as a guide to the dosage of radiation delivered. This is particularly valuable for the critically ill patient, who may have a prolonged stay in the intensive care unit.
MANAGEMENT OF SPECIFIC INJURIES DURING PREGNANCY
The management of thoracic trauma during pregnancy differs little from the nonpregnant state; however, strict attention to oxygenation is essential in order to avoid fetal hypoxia (see above). Additionally, during placement of thoracostomy tubes in late pregnancy, the elevated location of the diaphragm must be considered. A few cases of traumatic aortic rupture during pregnancy have been reported, and there is evidence to suggest changes in the aortic wall during this period may make women particularly prone to these injuries.45
Blunt Abdominal Trauma
Once diagnosed, the management of abdominal injuries during pregnancy differs little from the nonpregnant state. Nonoperative management of injuries to solid organs (liver, spleen, kidney) has been performed successfully in the gravid state and should be considered the treatment of choice in stable patients with these injuries (Fig. 37-3). In contrast, unstable patients or those in whom an intestinal injury is likely benefit from early operative treatment, as both hypotension and intra-abdominal infection can be harmful and potentially lethal to the fetus. As with any other emergency laparotomy during pregnancy (i.e., for acute appendicitis, cholecystitis, etc.), the uterus should be left intact, unless it is directly injured or it presents a mechanical limitation for treatment of maternal injuries. The indications for cesarean section following trauma are discussed below.
FIGURE 37-3 (A) Left upper quadrant ultrasound examination of an injured gravid patient demonstrating fluid above the spleen. (B) Ultrasound of the fetus in the same patient showing ample amount of amniotic fluid and intact pregnancy. (C) Abdominal CT of the mother showing liver laceration as cause of the free fluid (blood) seen on ultrasound. (D) CT of fetus showing no injuries. Mother and fetus recovered completely with no surgical intervention. CT = computed tomography.
Although the experience with abdominal operative procedures in injured pregnant patients is generally limited, the data about the safety and timing of other nonobstetrical abdominal surgeries in pregnancy are available. A review of 77 patients requiring laparotomy demonstrated that preterm labor occurred in 26% of the second-trimester patients and 82% of the third-trimester patients.46 Preterm labor was most common in patients with appendicitis. Although preterm labor was significantly higher in the last trimester, fetal loss was not. The authors concluded that the severity of the underlying disease, not the operation, was the most important factor in determining fetal and maternal outcome. There are also important anesthetic considerations when performing surgery during pregnancy. The basic objectives in the anesthetic management of these patients include the following: (a) maternal safety; (b) avoidance of teratogenic drugs; (c) avoidance of intrauterine fetal asphyxia; and (d) prevention of preterm labor.47Although a complete review of this subject is beyond the scope of this chapter, most studies to date indicate that surgery and anesthesia during pregnancy are unlikely to be associated with an increased incidence of congenital anomalies but may produce a slightly increased risk of miscarriage. When emergency surgery is required, the optimal anesthetic for the mother should be chosen and modified by considerations for maternal physiologic changes and fetal well-being.47 An obstetrician and/or perinatologist should be consulted if there is time, and intraoperative fetal and uterine monitoring should be standard.
The management of a pelvic fracture following blunt trauma may be particularly challenging during late pregnancy. Hemorrhage from massively dilated retroperitoneal vessels can obviously cause hemorrhagic shock.48 And, pelvic fracture is the most common injury to the mother that results in fetal death, with a fetal mortality rate as high as 35%.49 Fetal death may result indirectly from maternal shock or placental laceration or may be caused by direct injury to the head of the fetus. Although management of hemorrhage may include pelvic angiography and embolization of bleeding vessels, the dose of radiation associated with this approach usually exceeds the threshold that is considered safe during pregnancy, and these patients should be appropriately counseled. Operative fixation of unstable pelvic fractures, including acetabular fractures, has been reported during pregnancy, with good outcomes for both the mother and the fetus.50,51 The dose of radiation can be minimized and procedures chosen that do not rely heavily on radiographic control. A recent review concluded that when operative therapy for pelvic fracture is indicated, both the timing of the operation in relationship to delivery and the operative approach may need to be altered.52 Some of these patients have gone on to have normal vaginal deliveries within weeks of their surgery to fixate a pelvic fracture (Fig. 37-4).
FIGURE 37-4 X-ray of a patient in her third trimester sustaining a crush injury during the Haiti earthquake. Note the pelvic and femur fractures as well as the fetal head in the pelvis (arrow). A healthy baby was later delivered by cesarean section.
Fetal Injuries Following Blunt Trauma
The fetus is generally well protected from blunt forces by the pelvic bones (until the third trimester) and by the cushion of amniotic fluid. Only 1% of blunt injuries to the abdomen are associated with direct fetal injuries.24Occasionally, blunt trauma to the fetus may result in fractures of the extremities or skull, although these usually occur in late pregnancy, especially when the head is engaged. Severe blunt trauma occasionally causes rupture of the uterus. Manifestations of uterine rupture include severe maternal shock, a uterus small for dates, and presence of fetal parts outside the uterus. Although the diagnosis of this catastrophic event is usually not difficult, ultrasound is very sensitive in detecting uterine rupture and the presence of intraperitoneal hemorrhage in less severe cases.53
More commonly, blunt abdominal trauma causes separation of the placenta from the relatively inelastic uterine wall, a condition termed placental abruption (or abruptio placenta). Although minor placenta abruptions may be tolerated by the fetus, major abruptions are the most common cause of fetal death if the mother survives. Separation of the placenta from the uterus reduces the area for fetomaternal exchange of respiratory gases and delivery of nutrients for the fetus. Perinatal death associated with placental abruption may be due to anoxia, prematurity, or exsanguination. The manifestations of placental abruption include vaginal bleeding (which may be relatively minor), abdominal pain, uterine tenderness, and contractions.54 Disseminated intravascular coagulation is one of the most serious complications associated with abruption, as thromboplastins from the injured placenta enter into the maternal circulation. In the absence of clinical symptoms, a pelvic ultrasound examination may be useful but will miss minor abruptions. As discussed earlier in the chapter, CTM is the most useful method of detecting clinically silent cases of placental separation that result in fetal distress.
As the uterus expands out of the pelvis in the later stages of pregnancy, it frequently becomes the target for penetrating trauma. The maternal death rate from both gunshot wounds and stab wounds is lower than that of nonpregnant patients, likely due to the fact that the uterus is frequently targeted rather than other abdominal organs.24 Low-velocity stab wounds rarely penetrate the thick uterine wall and usually present little risk to either the mother or her unborn child. Death of the mother after abdominal gunshot wounds is similarly uncommon, as only 20–30% have injuries outside of the uterus.55 In contrast, gunshot wounds to the upper abdomen can result in severe maternal damage, as the abdominal organs and vasculature are compressed into this small space. Up to 70% of fetuses will sustain injuries following abdominal gunshot wounds, and 40–65% will die, depending on the injury and the degree of prematurity.56 If the bullet has penetrated the uterus and the fetus is both viable and alive, cesarean section should be performed and the baby’s injuries addressed surgically, if indicated. Successful outcome with this approach has been reported. A nonoperative approach has been advocated when the entry site of a penetrating wound is anterior and below the uterine fundus, and when there is no evidence of fetal distress, but this approach should be restricted to high-volume trauma centers with close collaboration between experienced trauma surgeons and obstetricians.25 There have also been isolated reports of successful damage control laparotomy with open abdomens in pregnant patients.57
Neurologic Injury During Pregnancy
The multi-institutional study by Kissinger et al.58 was the first to demonstrate the adverse effect of moderate and severe (Glasgow Coma Scale Score <12) trauma to the brain on fetal outcome. Severe injury to the brain was a significant risk factor for pregnancy loss in the investigation conducted by Ikossi et al.14 also. Certainly, maternal hypothalamic and pituitary dysfunction may accompany catastrophic brain injuries, and replacement of cortisone, thyroid, and vasopressin hormones may be required.59 Kelly et al.60 examined the function of both the anterior and posterior pituitary glands of 22 trauma patients of both sexes and demonstrated some degree of hypopituitarism in 40% of patients with moderate-to-severe traumatic brain injuries. Growth hormone and gonadotrophic deficiencies were the most commonly observed disorders. In addition, nutritional support, seizure control, and avoidance of infections and thrombotic complications are required in the care of the pregnant patient with a traumatic brain injury to ensure normal growth and development of the fetus. Because severe hyperventilation leads to a reduction in uterine blood flow through a mechanical reduction in venous return and subsequent decrease in cardiac output, the effective range of hyperventilation is reduced in pregnancy. Hypothermia and mannitol should both be avoided in pregnancy, whereas hypertonic saline has no known deleterious effects.61
The care of the pregnant patient with an acute injury to the spinal cord (see Chapter 23) is challenging, as well. For an extensive review of this subject, readers are referred to the excellent articles by Popov et al.62 and Gilson et al.63In brief, inotropic agents such as dopamine and dobutamine may be required for blood pressure support in patients in spinal shock. These agents appear to be safe in pregnancy, as they do no reduce uterine perfusion and are not associated with a teratogenic effect on the fetus. Finally, patients with an injury to the spinal cord are at risk for unattended delivery secondary to unrecognized contractions.64
Thermal Injuries in Pregnancy
Burns occurring during pregnancy are not uncommon, particularly in major burn centers and in developing countries. A burn increases spontaneous uterine activity and it affects circulatory exchange in the uteroplacental unit due to volume changes, which can have an adverse effect on the fetus. The maternal outcome of burns during pregnancy is related to the total body surface area involved as in nonpregnant patients, but fetal survival depends upon the gestational age, the extent of maternal injury, and maternal outcome.65 Although the treatment of the burned patient during pregnancy does not differ significantly from the patient in the nongravid state (see Chap. 48), there are certain caveats to be considered. First, fluid resuscitation should be particularly vigorous, given the expanded intravascular volume during normal pregnancy. Second, hypoxia must be avoided, and this may be particularly challenging in patients with inhalational injury associated with the burn. Due to the Bohr effect on oxygen dissociation curves, the fetus preferentially takes up carbon monoxide (CO) into its circulation. It is estimated that the fetus takes up to five times longer than the mother to remove CO; therefore, oxygen therapy should be prolonged for up to five times that needed to normalize maternal CoHb levels.66 Additionally, the use of tocolytic drugs may worsen the pulmonary complications of inhalation injuries. For care of the burn wounds, silver sulfadiazine cream should be used sparingly because of the risk of kernicterus associated with sulfonamide absorption, whereas pain medications should be used liberally.
Cesarean Section Following Injury
Guidelines for performing cesarean section following trauma as developed by the ACOG for the mother in extremis following a medical disaster (i.e., amniotic fluid embolism, major cardiac event) are summarized in Table 37-3. These guidelines apply to infants who are at least 25 weeks of gestation and would have a reasonable chance of surviving outside of the womb. The data suggest that, if a fetus is delivered within 5 minutes of maternal death, the anticipated fetal survival rate is 70%.67 In the trauma situation, if the mother presents in extremis, prompt cesarean section should be performed and combined with ED thoracotomy as described above.68 In a study representing nine major trauma centers, 441 pregnant trauma patients were described, including 32 patients who required cesarean section for either maternal or fetal distress.69 Fifteen (45%) of the fetuses and 23 (72%) of the mothers survived. Thirteen of the fetuses delivered had no fetal heart tones and none survived, whereas 20 infants with both fetal heart tones and an estimated gestational age of ≥26 weeks or more had a 75% survival rate. Five of the infants who died were potentially salvageable (i.e., had both fetal heart tones and an estimated gestational age of 26 weeks), but there was delayed recognition of fetal distress among mothers with moderate injuries (ISS ≤16). The use of CTM was not universal among these patients even in these experienced trauma centers. The algorithm proposed from this study for emergency and perimortem cesarean section following maternal trauma is shown in Fig. 37-5.
TABLE 37-3 Postmortem Cesarean Section
FIGURE 37-5 Algorithm for emergency cesarean section following trauma in pregnancy. CPR = cardiopulmonary resuscitation; EGA = estimated gestational age; FHT = fetal heart tones. (Reproduced with permission from Morris JA, Rosenbower TJ, Jurkovich GH, et al. Infant survival after cesarean section for trauma. Ann Surg. 1996;223:481.)
In most trauma centers, an obstetrician should be readily available to perform a cesarean section for fetal or maternal distress. Should the trauma surgeon be in the position to perform this operation, the key to success is the use of large incisions. A long, vertical abdominal incision is used to access the uterus, followed by a midline vertical incision through the upper uterine segment. The infant is removed immediately and suctioned, the cord is clamped and cut, and resuscitation initiated on the baby while the surgeon simultaneously tamponades bleeding from the placenta and uterine wall of the mother.
In the study using data from the NTDB cited above, Ikossi et al.14 reported that among the 1,195 pregnant women on whom data were available, 1,178 survived, 17 died, and 66 pregnancies were lost. Of those patients who delivered their infant during the admission after trauma, 75% underwent cesarean section. This is a 3-fold greater rate than the national average of 13–22%. Also, 75% of these cesarean sections were performed within 24 hours of admission, implying urgent operations. The indications for delivery (fetal or maternal distress etc.) are not currently available in the NTDB, nor are the outcomes of the fetuses. Only 3% of records included fetal monitoring in the data submitted, but this is likely under-reported, as there is no separate coding field for CTM data in the NTDB. The data capture fields on both the infant and the mother contained in the NTDB will need to be expanded in order to get a more complete picture of the impact of trauma on fetal outcome.
CRITICAL CARE OBSTETRICS
Although a complete description of the care of the critically ill or injured obstetrical patient is beyond the scope of this chapter, a few conditions that might be encountered by the critical care surgeon in the postinjury state are worthy of mention. The first is pregnancy-induced hypertension, which in its most severe form includes preeclampsia and eclampsia. The risk factors for preeclampsia include first pregnancy, multiple gestations, and a positive family history. The criteria for preeclampsia include a sustained systolic blood pressure >160 mm Hg, a sustained diastolic pressure of >110 mm Hg, proteinuria >5 g/24 hours. Oliguria, pulmonary edema, and thrombocytopenia.70Symptoms might also include headache and right upper quadrant pain in the abdomen. Although in its mild stages, preeclampsia can be managed expectantly, this syndrome has been associated with intrauterine growth retardation. If near term, delivery should be considered. Conservative measures include treatment of the hypertension (i.e., hydralazine or beta-blockade) and administration of magnesium sulfate. In its most severe form, preeclampsia progresses to eclampsia with the onset of seizures. Eclampsia, in turn, may be associated with intracerebral hemorrhage, blindness, acute tubular necrosis, cardiac failure, and disseminated intravascular coagulation for which the only cure is evacuation of the uterus.
Both amniotic fluid and pulmonary embolism remain major causes of morbidity and mortality during pregnancy. Amniotic fluid embolism is a catastrophic event that presents as severe hypoxia and cardiovascular collapse. Typically occurring during labor, the etiology was presumed to be the introduction of amniotic fluid into the maternal circulation inducing disseminated intravascular coagulation, pulmonary hypertension, and right heart failure. Recent data suggest that it may not be the components of the fluid itself that are detrimental, but rather an immunopathologic response to these components that leads to the listed complications.70 Treatment is largely supportive and includes cardiovascular support and correction of any coagulopathy. As previously mentioned, pregnancy is normally a hypercoagulable state due to increased production of clotting factors and fibrinogen directed at preventing hemorrhage during delivery. Additionally, the increased pressure on pelvic veins by the enlarged uterus increases the risk of both deep venous thrombosis and pulmonary embolism. The injured pregnant patient has the added thrombotic risk factors associated with trauma (pelvic and lower extremity fractures, immobility, neurologic injury, etc.). Prophylactic doses of enoxaparin should be utilized in all hospitalized pregnant patients. Enoxaparin is both safer and more effective than standard heparin, and it presents low risk to the fetus because it does not cross the placenta.
Another potential complication following severe trauma during pregnancy is premature labor. Premature labor is defined as uterine contractions combined with cervical change (effacement or dilation). In one study of relatively minor trauma, less than 1% of patients demonstrated preterm labor. In contrast, following severe trauma, most patients will exhibit some degree of uterine contractile activity.32,34 Although most of these contractions will resolve spontaneously over time, some patients may benefit from the pharmacologic inhibition of labor by the administration of tocolytic drugs. Drugs currently available for tocolysis include sympathomimetics such as terbutaline, indomethacin, and calcium channel blockers (nifedipine).5 All these drugs have side effects that may complicate their use in injured patients. Magnesium sulfate may cause hypotension and mental status changes, whereas indomethacin has been associated with oligohydramnios and promotes closure of the ductus arteriosus in the fetus.5Additionally, indomethacin may produce bleeding in the trauma patient. Alpha-adrenergic drugs produce tachycardia, may mask blood loss, and may induce chest pain. The use of calcium channel blockers is associated with hypotension.5 Tocolytic drugs should not be used in patients with active vaginal bleeding or suspected placental abruption because blood may accumulate inside a relaxed uterus. Other contraindications to tocolysis include preeclampsia, eclampsia, uncontrolled diabetes mellitus, serious cardiac disease, and cervical dilatation greater than 4 cm. In patients in the last trimester of pregnancy who develop contractions or premature labor, betamethasone is administered in order to hasten lung maturation in the premature baby should delivery be necessary.
FETAL OUTCOME FOLLOWING TRAUMA AND PREGNANCY
Although it is generally recognized that the most common cause of fetal death following trauma is maternal death, the actual ratio of fetal to maternal deaths ranges from 3:1 to 9:1.58,71 Several attempts have been made to identify factors that would predict a poor fetal outcome following trauma during pregnancy.14,58,71–81 Although not all studies are in agreement, it appears that maternal physiologic variables are poor predictors of fetal outcome. Factors generally associated with risk to the fetus include maternal hypotension, severe traumatic brain injury, high ISS, pelvic fracture, ejection from the vehicle, severe abdominal trauma, elevated serum lactate on admission, need for transfusion, low gestational age, and fetal tachycardia or bradycardia.
A recent 10-year population-based study by Schiff et al. 77 examined the outcomes of both mother and infant after injury during pregnancy. Patients included 266 nonseverely injured gravid women (ISS of 1–8) and 28 severely injured women (ISS >9) who delivered during their hospitalization after injury. Even the nonseverely injured pregnant women were at increased risk of placental abruption, and their infants were at increased risk of suffering hypoxia and fetal death. Severely injured pregnant women were at a 17-fold increased risk of placental abruption and their infants were at increased risk of prematurity, low birth weight, and fetal distress, and had a 30-fold greater risk of fetal death. In a similar study from California, women who delivered at the trauma hospital (Group 1) were compared with women who had a history of trauma during their pregnancy but delivered during a second hospitalization (Group 2), and with nontrauma controls.78 As would be anticipated, women in Group 1 had the worst outcomes, with an odds ratio (OR) of 60 for maternal death, 4.7 for fetal death, 43 for uterine rupture, and 9.2 for placental abruption. Women in Group 2 sustained a 2.7-fold increase in premature labor and a 4-fold increased risk of maternal death compared with uninjured women. In addition, they had higher rates of premature delivery and low birth weight at delivery compared with uninjured pregnant women, raising the suggestion that chronic abruptions secondary to trauma may lead to placental insufficiency and fetal compromise. In the large study compiled from data in the NTDB, the ORs for loss of a pregnancy after trauma were calculated based on the nature of the injury.14 As can be seen in Table 37-4, injuries to the head and abdomen carried the highest risk, as did an overall ISS of >15.
TABLE 37-4 Risk Factors for Loss of Pregnancy After Trauma
INJURY PREVENTION DURING PREGNANCY
These poor outcomes for both the mother and her fetus associated with even relatively minor trauma highlight the need for attention to injury prevention during pregnancy, and three areas of injury prevention deserve specific attention. The first involves the use of drugs and alcohol (see Chapter 42). An alarming number of women test positive for illegal drugs and/or alcohol when they are injured during pregnancy. Ikossi et al.14 reported that 13% of pregnant women tested positive for alcohol at the time of their trauma admission and 20% were using illicit drugs. In a more recent study of 84 injured pregnant women, an alarming 45 (>50%) tested positive for alcohol.82 Patients who tested positive for alcohol were more likely to exhibit other risk-taking behaviors such as lack of restraints while driving also. Not only are these substances known to be harmful to the unborn child, but the association between their use and both intentional and unintentional injuries has been well documented.83 Prenatal care must include education on the subject of substance abuse and provide opportunities for treatment for those women with a history of alcohol abuse.
Intimate partner violence is the most common cause of trauma-related maternal death during pregnancy, and maternal deaths due to homicide exceed those due to any obstetric cause. It is estimated that between 6 and 22% of gravid women experience intimate partner violence during pregnancy.70 McLeer and Anwar reported that after staff in the ED were trained to recognize signs of battery, the number of women seeking emergency care who were identified as being physically abused rose from 6 to 30%.84 Similarly, McFarlane et al.12, using a three-question Abuse Assessment Screen, detected a 17% prevalence of physical or sexual abuse during pregnancy, with 60% of women reporting two or more episodes of assault. Pregnant women reporting current violence were significantly more likely to report depressive symptoms, higher levels of psychosocial stress and substance abuse, as well.85 Other risk factors for pregnancy-related violence include low socioeconomic status, low levels of social support, first-time parenting, and carrying an unexpected or unwanted pregnancy.25 In another study of 203 injured pregnant patients, 32% were victims of intentional injury.84 In most cases, the husband or boyfriend was the offender. The incidence of fetal loss is surprisingly high in this group of battered women. In addition to fetal loss, abuse during pregnancy has been associated with low fetal birth weight, low maternal weight gain, maternal infections, anemia, and maternal alcohol and drug abuse.
Interpersonal violence is not dependent on race, age, marital status, or socioeconomic status (see Chapter 46), thus making all pregnant women potential victims of abuse.86 A history of depression, substance abuse, or multiple visits to the ED should raise the level of suspicion for abuse, as should the presence of an overprotective partner.86 Abused women may initially delay seeking medical attention or give an implausible explanation for injuries. A history of “spontaneous” abortion, miscarriages, and premature labor may indicate violence occurring during pregnancy, also. Physical signs of abuse may include bruises on the breasts, abdomen, head, neck, genitals, or upper extremities, as well as the presence of injuries at multiple sites in various stages of healing.24 Because pregnancy is often the only time that healthy women come into frequent contact with health care providers, it presents a unique opportunity to intervene in cases of intimate partner abuse and possibly prevents this tragic cause of homicides.
Despite the recognition that fetal deaths are far more common in women who are ejected from moving vehicles, multiple studies have documented that pregnant women are frequently unrestrained, even if they have received specific information about seatbelt use in their prenatal visits. As mentioned above, those who are unrestrained are more likely to exhibit other risk-taking behaviors such as alcohol and drug use and smoking during pregnancy, also. Sadly, fetal death is 3-fold more common in women who are unrestrained compared to their restrained gravid counterparts.87 Unrestrained pregnant women are also 1.9 times more likely to have a low birth weight baby and 2.3 times more likely to give birth within 48 hours of a crash.88 Although the experience with air bags is limited, maternal and perinatal outcomes appear to be at least similar with or without air bag deployment. Also, there is no evidence that placental abruption is associated with air bag injuries.89,90 A comprehensive biomechanical program aimed at improving the safety of pregnant women and their fetuses in motor vehicle crashes is currently under way in several states.91,92 This type of research, combined with education and primary enforcement of seatbelt laws, could have a major impact on preventing maternal and fetal deaths following motor vehicle crashes during pregnancy.
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