Bonnie Lau and Susan B. Promes
Significant trauma affects approximately 7% of pregnant women (1). In fact, trauma was reported to be the leading cause of death during pregnancy in at least one series (2). Statistically, pregnant women sustain approximately 4.1 trauma-related hospitalizations per 1,000 deliveries (3). The pregnant trauma patient presents a unique challenge to the emergency department (ED) team caring for her. Not only is the physician caring for two patients, but both of the patients have their own unique needs. In general, when faced with a pregnant trauma patient, the emergency physician should resuscitate the mother first. The well-being of the unborn fetus is dependent upon the hemodynamic stability of the mother.
It is imperative that the physician caring for the gravid woman be aware of the physiologic changes that occur during pregnancy and the impact these changes may have on the resuscitation of the pregnant woman and her unborn fetus (eTable 52.1). This knowledge will be critical to the evaluation and treatment of the woman and her unborn child.
eTABLE 52.1
Changes in Maternal Physiology During Pregnancy
Airway. Although airway anatomy does not change significantly, progesterone causes smooth muscle relaxation, affecting the lower esophageal sphincter and increasing the risk of aspiration.
Breathing. The diaphragm is gradually pushed up 3 to 4 cm during pregnancy, causing a 25% decrease in functional residual capacity and resulting in decreased maternal oxygen reserve. Pulmonary function is further compromised by increased oxygen consumption. Starting in the first trimester, stimulation of the medullary respiratory center by progesterone increases minute ventilation by up to 50% (a result of increased tidal volume). This is accompanied by a 10-mm Hg increase in PO2, a 10-mm Hg decrease in PCO2, and a compensatory decrease in bicarbonate to about 19.5 mEq/L. These physiologic changes result in less respiratory reserve in the pregnant trauma patient.
Circulation. Pregnancy is a high-flow, low-resistance state of cardiovascular homeostasis. Heart rate increases until the end of the second trimester, when it plateaus at 10 to 15 beats above baseline. Systolic, and to a greater extent diastolic, blood pressure decrease during the first and second trimesters, returning to prepregnancy baseline levels during the third trimester. Cardiac output increases by 40% by the end of the first trimester and persists at this level, causing a cardiac flow murmur in 90% of pregnant women. By the third trimester, there is increased vascular congestion in the pelvis and a 50% decrease in the velocity of venous flow in the lower limbs (4). These changes predispose the gravid patient to deep venous thrombosis as well as increased bleeding from lower extremity and pelvic trauma.
In addition, several hematologic changes accompany pregnancy. A 50% increase in blood volume and concomitant increase in red blood cell mass by only 20% to 30% results in a 3% to 6% drop in hematocrit. The white blood cell count increases to 12,000 to 18,000/μL by the second trimester and may increase to 25,000/μL with stress. The prothrombin and partial thromboplastin times are somewhat decreased. Coagulation factors rise gradually and exceed fibrinolytic activity by the third trimester.
The fetus has a higher hemoglobin concentration than the mother, and fetal hemoglobin has a higher affinity for oxygen. As a result, fetal oxygen consumption does not decrease until oxygen delivery decreases by 50% (5). This allows the fetus to tolerate brief periods of maternal hypoxia and hypoperfusion. In late pregnancy, the fetus is capable of redistributing blood to the heart and brain (6).
CLINICAL PRESENTATION
Critically ill pregnant trauma patients may present with normal vital signs due to the physiologic changes that occur in pregnancy; this should not give the emergency physician a false sense of security. Pregnant women have increased blood volume as they near term, so blood loss must be excessive before hypotension occurs. Abdominal pain in the pregnant trauma patient may be due to common intra-abdominal injuries associated with blunt trauma. Other causes of life-threatening problems include uterine rupture, placental abruption, and premature labor.
Pregnant trauma patients tend to have a slightly different injury pattern when compared to the general trauma population, with increased intra-abdominal injuries and decreased traumatic brain injuries (7). In penetrating trauma, this may be due to changes in maternal anatomy with increasing gestational age. The diaphragm and intra-abdominal contents are displaced upward by the enlarging uterus; hence, injury patterns will vary from the general population. For example, someone with a stab wound to the left upper quadrant is at increased risk for intestinal injury because the uterus displaces the intestinal contents superiorly.
Whether the pregnant patient is involved in blunt or penetrating trauma, the fetus in addition to the mother is at risk for injury. Even minor maternal injuries can lead to placental abruption, uterine rupture, fetal–maternal hemorrhage, and premature birth. The emergency physician should look for signs of occult injury that are manifested by uterine irritability, vaginal bleeding, and fetal tachycardia.
DIFFERENTIAL DIAGNOSIS
The emergency physician caring for the pregnant trauma patient should first consider the typical injury patterns that are associated with a given mechanism of injury. The pregnant trauma patient is not immune to common traumatic injuries. While the emergency physician is evaluating the pregnant patient for common injuries, the physician should also consider the unique role the gravid uterus plays in the traumatic event. As the uterus enlarges during pregnancy, changes in intra-abdominal anatomy alter the injury pattern. For example, the diaphragm moves cephalad into the thoracic cavity. Subsequently, in a pregnant patient who sustains a penetrating injury to the chest, the physician should have a greater suspicion for a diaphragmatic injury. In addition, the large gravid uterus displaces the intra-abdominal contents, making bowel injuries less common and injury to the uterus more common in blunt trauma. A few important injuries associated with pregnancy include placental abruption, uterine rupture, maternal–fetal hemorrhage, and premature labor. The greater the severity of maternal trauma, the more likely a significant fetal insult will occur. Pearlman and Tintinalli (8) reported a fetal loss rate of 41% with life-threatening maternal injuries while the fetal loss rate was 1.6% with nonlife-threatening injuries.
Seizures in trauma patients are generally associated with head injuries. However, in the gravid trauma patient, the emergency physician must also consider eclampsia as the etiology of the seizure and subsequent trauma.
ED EVALUATION
As the survival of the fetus is dependent upon maternal resuscitation, the evaluation of the pregnant trauma patient should proceed in a step-wise fashion. Advanced trauma life support principles should be followed as in the nonpregnant trauma patient. However, during the primary and secondary trauma surveys, the emergency physician must apply a detailed understanding of the physiologic changes that occur in the pregnant state to detect potentially life-threatening conditions. The airway must be managed aggressively. All pregnant trauma patients should be placed on oxygen, since oxygen consumption is increased with pregnancy, and it is important to avoid fetal hypoxia. When evaluating the circulatory status, the physician should remember that the second-trimester pregnant patient without significant injuries may have an elevated heart rate and lower blood pressure. Conversely, she may also have significant life-threatening hemorrhage without alteration in vital signs due to the physiologic increase in cardiac output and intravascular volume.
After the primary survey, a complete history should be obtained, including last menstrual period, estimated date of delivery, previous pregnancy history, and any problems associated with the pregnancy.
The fetus is evaluated during the secondary survey. The fundal height should be assessed, recognizing that a fundal height at or above the level of the umbilicus may indicate a potentially viable fetus. The distance between the symphysis pubis and the uterine fundus measured in centimeters approximates gestational age in weeks (Fig. 52.1). The threshold for fetal viability is 23 to 24 weeks depending on the resources available at the facility to care for the neonate (9). The presence of fetal heart tones should be documented. In patients at 20 weeks or more gestation, cardiotocographic monitoring should be obtained as soon as possible. This gives the physician information regarding fetal–maternal well-being. A normal fetal heart rate is between 120 and 160 bpm. Fetal tachycardia, fetal bradycardia, contractions, loss of beat-to-beat variability, or late or prolonged decelerations after contractions may be signs of fetal distress heralding such pathologic states as placental abruption or occult maternal shock. If the patient has vaginal bleeding, then a sterile vaginal speculum examination should be performed to identify the source of bleeding, being mindful of potential placenta previa. Aside from evaluation of the pregnancy itself, a speculum examination may reveal signs of genitourinary trauma such as lacerations from pelvic fractures or penetrating trauma.
FIGURE 52.1 The height of the uterine fundus at different gestational dates.
Upon completion of the primary and secondary surveys, the clinician should tailor further diagnostic studies to the individual patient. As the fetus is dependent on maternal well-being, diagnostic tests and therapy should be directed primarily at the care of the mother and should not be delayed because of the pregnancy. As classic signs of shock may present late, a more detailed initial workup may be appropriate in pregnancy. The hematologic changes of pregnancy must be considered when evaluating any laboratory results. It is important to remember that pregnant women have a “dilutional anemia” due to their increased blood volume (eTable 52.2). They also have an elevated white blood cell count and sedimentation rate. Fibrinogen levels are increased, as are coagulation factors. All pregnant trauma patients should have blood type determination as all Rh-negative women require Rho(D) immune globulin (RhoGAM). The recommended dose for all Rh-negative gravidas is 300 μg unless there is risk of massive isoimmunization. Based on the results of a Kleihauer–Betke (KB) test, additional RhoGAM (300 μg per 30 mL of estimated fetomaternal hemorrhage) may be warranted (10,11).
eTABLE 52.2
Hemoglobin Values in Pregnancy
The Eastern Association for the Surgery of Trauma (EAST) recommends a major change in the management of pregnant trauma patients in which physicians would order a KB test for all pregnant patients ≥20 weeks of gestation, regardless of Rh status (10–12). This recommendation is based on the results of two class II and one class III studies in which investigators found that a positive KB test regardless of Rh status detected all cases of preterm labor (5,10,12). Given that the EAST level II recommendation was based on only three studies, no change in ED management can be suggested at this time. Therefore, patients with a potentially viable fetus (i.e., ≥20 weeks of gestation) sustaining a traumatic injury should have cardiotocographic monitoring for a minimum of 6 hours (12).
Ultrasound examination (13) can be used to evaluate for a traumatic pericardial effusion and tamponade or to demonstrate free fluid in the abdomen. In addition, it may help determine fetal age, position, and amniotic fluid volume. However, its limitations must be recognized. Ultrasound may miss placental abruption; the reported sensitivity is only 24% (14). This diagnosis is made by signs of maternal compromise or fetal distress on cardiotocographic monitoring and not generally by ultrasound.
As fetal outcome is dependent upon maternal condition and resuscitation, radiographic studies should not be withheld to prevent fetal radiation exposure. However, knowledge of the underlying principles of fetal radiation exposure must be understood by the practitioner to address patient concerns and guide appropriate evaluation (eTable 52.3). The issues of concern include risk of fetal demise, fetal malformation, childhood cancer, and fetal neurodevelopment versus the risk of missed injury that would require intervention. In the first 10 days of pregnancy, the response to significant radiation exposure is an all-or-none response. From 10 days to 10 weeks, the fetus is at greatest risk for radiation-related malformation. After 20 weeks, the fetus does not appear to be at increased risk of malformation (15). Fortunately, exposure to <5 to 10 rads does not increase the baseline risk of malformation. The increased risk of childhood cancers from prenatal radiation exposure is unclear. However, the associated risk of in utero radiation with childhood cancers has been estimated at 8% increase in childhood cancers per 100 rads. To place this in perspective, this is equivalent to an excess absolute risk of childhood cancer from 0.00006 to 0.00008 for each 100 mrad (16,17). The risk of growth restriction, microcephaly, and mental retardation are highest at 8 to 15 weeks and appear to be associated with high-dose radiation of at least 20 to 40 rad (10). Most shielded plain film radiographs, brain computed tomography (CT), and chest CT scans are well below these concerning levels. The risk of a significant missed injury is usually higher than the risk of adverse sequelae from radiation in injured patients. However, an abdominal CT scan may deliver 3 to 9 rads to the fetus. The emergency physician may consider shielding the uterus and scanning only the upper abdomen to rule out solid organ injury and subsequently observing the patient and monitoring her clinically for signs of increasing abdominal pain, worsening anemia, fetal distress, or maternal hemodynamic changes.
eTABLE 52.3
Estimated Radiation Dose to Fetus per Radiograph
Diagnostic peritoneal lavage (DPL) may be performed in pregnancy using the supraumbilical technique. As with ultrasound, DPL cannot be used to evaluate the retroperitoneum. Exploratory laparotomy may be necessary during pregnancy, especially in patients with penetrating trauma to the upper abdomen. Although surgical exploration was previously recommended for all pregnant patients with penetrating trauma, some authors advocate nonoperative management with observation for penetrating wounds directly to the uterus if the patient is hemodynamically stable and there are no signs of fetal distress (18–20). The determination of whether to perform a cesarean section at the time of exploration is based on evidence of fetal–maternal compromise detected on cardiotocographic monitoring.
KEY TESTING
• Type and screen (especially for Rh status)
• Consider Kleihauer–Betke test
• Any necessary radiographic studies
• Bedside ultrasound (pericardial effusion, free fluid in abdomen, fetal age/position, amniotic fluid volume)
• Cardiotocographic monitoring for at least 6 hours
ED MANAGEMENT
As with all trauma patients, the initial management of the pregnant trauma patient occurs simultaneously with the ED evaluation. Emphasis is placed on maternal resuscitation to maximize both maternal and fetal outcomes. Special care should be taken if the patient requires intubation. The pregnant patient’s airway may be edematous. The gravid woman is at increased risk of aspiration secondary to delayed gastric emptying and decreased lower esophageal sphincter tone. In addition, gravidas have decreased oxygen reserves and may require early intubation to maximize oxygenation and ventilation; also, they may desaturate rapidly after paralysis (21). In later pregnancy, if a chest tube is necessary, it should be placed one to two rib spaces higher than usual, as the diaphragm will be elevated. This, along with palpation of the diaphragm with a finger during thoracostomy placement, will prevent inadvertent intra-abdominal placement of the tube.
After the 20th week of pregnancy, the trauma patient is at risk for the supine hypotensive syndrome, the result of uterine compression of the inferior vena cava by the gravid uterus, leading to decreased venous return to the heart. All pregnant trauma patients of 20 weeks or greater gestation who are supine should, therefore, be placed in 15 degrees of left lateral tilt to prevent this compression (10,11,20). Aggressive early resuscitation is particularly important as gravid patients may not develop overt signs of hypovolemia until they are in the late stages of shock. Changes in uterine blood flow, which can lead to fetal distress, occur before maternal vital signs change. Crystalloid fluid replacement should be started, and blood administered as necessary. Vasopressor support should be avoided as pressors significantly decrease uterine blood flow and do not address the likely underlying cause of hypotension, namely hemorrhage. Hemodynamic instability secondary to dysrhythmias that are amenable to defibrillation or cardioversion should be treated as such without concern for fetal injury.
There are several unique situations that the emergency physician must consider in the gravid trauma patient. Pelvic fractures may be particularly dangerous during pregnancy. They may lead to increased blood loss from dilated pelvic veins. They also may lead to direct fetal injury, resulting in a high incidence of fetal morbidity and mortality. Medical antishock trousers have no role in the management of the gravid trauma patient.
Uterine injury is uncommon in the first trimester, as the bony pelvis protects the small gravid uterus. However, later in pregnancy minor uterine injury, such as contusion, is relatively common. This usually presents with uterine contractions, which resolve spontaneously in 90% of cases. Rarely, blunt abdominal trauma can cause uterine rupture, which can present with catastrophic blood loss and fetal demise (5,8). This may be diagnosed on physical examination by palpating a flattened uterus or fetal parts free in the abdominal cavity. Ultrasound can also be used to identify a traumatic uterine rupture.
Placental abruption, a premature separation of the placenta from the uterine wall, is common with blunt abdominal trauma and can cause fetal distress. It occurs in 1% to 3% of pregnant women with minor trauma and in 40% to 50% of pregnant women with major life-threatening trauma (6,8). Abruption may present with vaginal bleeding, abdominal pain and tenderness, uterine contractions, or fetal distress. However, it may be occult and, moreover, may be missed on ultrasound examination. The most sensitive test for the evaluation of placental abruption is cardiotocographic monitoring to detect uterine irritability and fetal distress. Cesarean section may be necessary to save the fetus in severe cases of placental abruption.
Amniotic fluid embolism can occur with trauma and placental abruption. Debris and amniotic fluid become lodged in the maternal respiratory system, causing sudden dyspnea, hypoxia, and hypotension. These patients are also at risk for developing disseminated intravascular coagulation. Treatment of amniotic fluid embolism in patients is supportive, but the mortality rate unfortunately is high. Cardiopulmonary bypass has been used successfully to treat severe cases.
Fetal outcomes in pregnant patients with burns are directly related to the extent of the burn and the gestational age of the fetus. A burn of <20% total body surface area usually does not lead to pregnancy complications, but extensive burns may lead to fetal demise or premature labor (22). Conversely, maternal outcomes in the setting of burns are not affected by pregnancy.
The burn patient should also be assessed for carbon monoxide exposure. There is increased binding of carbon monoxide by fetal hemoglobin, resulting in increased carbon monoxide exposure to the fetus. All symptomatic patients or those with a carboxyhemoglobin level greater than 15% should be placed on 100% oxygen by mask and should be considered for hyperbaric oxygen therapy (23).
If the pregnant trauma patient arrests, the clinician should consider a perimortem cesarean section if there is a potentially viable fetus (≥23 weeks of gestation). As time is critical to the survival of the fetus, the procedure should be initiated promptly and should be performed by the most experienced physician available. Delivery within 5 minutes of maternal arrest leads to a higher rate of fetal survival with good neurologic outcome. Survival rapidly declines to 5% (usually with neurologic sequelae) if the procedure is not performed until 15 minutes after maternal arrest (24). Using a number 10 blade, a midline vertical incision should be made from the epigastrium to the pubic symphysis. Ideally, the clinician should make one incision that goes from the skin down to the uterus. The uterine incision is then performed vertically from the fundus to the reflection of the bladder. The placenta is incised if necessary. The child is delivered and the cord clamped and cut. Neonatal resuscitation should be aggressive and should begin immediately. With delivery of the infant, maternal hemodynamics may actually improve because of increased venous return. It is thus important to continue maternal resuscitative efforts (airway management and CPR) during and after perimortem cesarean section.
CRITICAL INTERVENTIONS
• Resuscitate the mother adequately to resuscitate the fetus.
• Identify and treat early shock prior to development of abnormal vital signs.
• Position the patient in a 15-degree leftward tilt to prevent the supine hypotensive syndrome.
• Any pregnant trauma patient with a potentially viable fetus should be admitted for cardiotocographic monitoring for at least 6 hours, even when there are only minor injuries.
• Administer RhoGAM 300 μg intramuscularly (IM) to all Rh-negative patients.
DISPOSITION
Routine obstetric (OB) consultation in all pregnant trauma patients has been recommended by various organizations, although the evidence of improved outcomes with this intervention is lacking. Clearly, appropriate consultation is necessary for the best management of the pregnant trauma patient. Trauma surgery, OB and gynecology, and neonatology may be necessary for the multidisciplinary care of the pregnant trauma patient. The need for consultation is determined by the patient’s potential injuries and the estimated gestational age of the fetus. At a minimum, pregnant trauma patients with a viable fetus (≥20 weeks) should receive OB consultation and 6 hours of cardiotocographic monitoring (10). This includes gravid trauma patients with little or no evidence of maternal injury. If monitoring detects an abnormality (vaginal bleeding, abdominal pain, contractions, or fetal heart rate abnormalities) during this initial observation period, the period of monitoring should be extended to 24 to 48 hours (6,10,25). Although the fetus is not viable until 23 weeks at the earliest, some sources recommend monitoring for all patients who are more than 20 weeks pregnant (9). This recommendation is based on the fact that some obstetricians will attempt tocolysis if there is evidence of premature labor in this group.
Prior to disposition, injury prevention issues must be addressed. The possibility of interpersonal violence or intentional injury cannot be overstated. Data suggest that there is a rise in the rate of domestic violence as the pregnancy progresses. The health care provider should also discuss appropriate seatbelt use prior to discharge. The lap belt should be worn low over the iliac crest, and the shoulder restraint should cross above the uterus. When indicated, the emergency physician must remember tetanus prophylaxis. Standard guidelines for tetanus prophylaxis should be followed. No adjustments are needed in pregnancy.
Common Pitfalls
• Inadequate early maternal resuscitation.
• Failure to perform cardiotocographic monitoring.
• Failure to perform necessary radiographs for fear of fetal complications.
• Failure to treat fetal–maternal hemorrhage in Rh-negative trauma patients.
• Delay in performing a perimortem cesarean section with maternal cardiopulmonary arrest.
ACKNOWLEDGMENTS
The authors gratefully acknowledge the contributions of Charles J. Gerardo, the coauthor of this chapter in the previous edition.
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