Trauma in Pregnancy
Trauma in Pregnancy
Authors:
Ariel Clark, MD, Department of Emergency Medicine, Maine Medical Center, Portland.
Rebecca Bloch, MD, Attending Emergency Physician, Department of Emergency Medicine, Maine Medical Center, Portland.
Michael Gibbs, MD, FACEP, Chief of Emergency Medicine, Maine Medical Center, Portland.
Peer Reviewer:
Robert E. Falcone, MD, FACS, Clinical Professor of Surgery, The Ohio State University, Columbus.
Resuscitation in the pregnant patient is an uncommon occurrence, estimated at 1 in 30,000 deliveries,1 yet it is unique in its potential to save not one, but two lives. Trauma is estimated to occur in approximately 5% of pregnant patients,2,3 and it is the leading cause of nonobstetric mortality in this population.3,4 The physiologic changes of pregnancy, and the need to balance the care of mother and fetus, make the care of a critically injured pregnant patient a challenge for any physician. This article reviews physiologic changes of pregnancy and injuries unique to pregnancy, and discusses the assessment and management priorities of the pregnant trauma patient.
The Editor
Physiologic Changes of Pregnancy
To effectively manage the injured pregnant patient, it is essential to understand a number of predictable changes in maternal physiology. These changes have the potential to impact vital signs, the physical examination, and results of laboratory studies. Most importantly, physiological alterations associated with a normal pregnancy have a significant effect on cardiopulmonary reserve and injury tolerance.
Respiratory. During pregnancy, the resting oxygen requirement and minute ventilation increase to meet increasing metabolic demands. At the same time, the functional residual capacity decreases by 20%,5,6 due to elevation of the diaphragm by the gravid uterus. With greater oxygen demand, and less physical space for expansion of the lungs, the pregnant patient functions with a significantly decreased oxygen reserve.
While the pregnant patient will desaturate quickly, the fetus is even more vulnerable to hypoxia. The reason for this difference is that the umbilical vein and artery have a much lower partial pressure of oxygen than the maternal circulatory system. Maternal oxygenation is important for fetal well-being, as fetal oxygenation remains constant until maternal paO2 drops below 60 mmHg.7 As a general rule, the fetus has roughly two minutes of oxygen reserve. Animal studies reveal that significant maternal hypoxia results in a 30% reduction in uterine blood flow, further compromising fetal outcome.8
The pregnant patient is also at significant risk for aspiration. During pregnancy, progesterone acts to decrease gastrointestinal motility6 and increase laxity of the lower gastroesophageal sphincter.9 This effect, in concert with the anatomical compression of the stomach by the uterus, renders the pregnant patient more prone to aspiration. Increased and more frequent oral intake further increases the chance of aspiration.
Pregnancy is an edematous state. These changes affect the entire body, including the tongue and supraglottic soft tissues.1,10 Capillary engorgement due to increased blood volume and decreased plasma oncotic pressure causes swelling of the respiratory tract mucosa and easy bleeding that may complicate intubation. (See Table 1.)
Table 1. Changes in Respiratory Physiology
|
Alteration |
Implication |
Action |
|
|
|
|
|
|
|
|
|
Cardiovascular. Several cardiovascular changes of pregnancy should be considered when caring for the pregnant trauma patient. Beginning in the eighth week of pregnancy, increasing progesterone causes smooth muscle relaxation and a significant decrease in total peripheral resistance. By week 12, blood pressure starts to gradually decline to a nadir around week 28, with a total systolic and diastolic blood pressure drop of 5 to 15 mmHg.6,9 These effects are seen in central venous pressure as it drops 9 mmHg to around 4 mmHg in the third trimester.11 Due to an increase in alpha receptors stimulated by estrogen within the myometrium, heart rate increases 10 to 15 beats per minute, and cardiac output increases to 30-50% above normal during the second trimester.11 As gestation advances, maternal blood volume increases steadily, peaking at 40% above pre-pregnancy levels at term.
These changes, which help the pregnant patient tolerate the increasing metabolic demand of the fetus and prepare her for the expected hemorrhage of childbirth,12 may easily conceal the presence of shock. Hemodynamic changes are often not apparent until 35% total blood volume loss.11 Therefore, tachycardia and hypotension should be viewed as late signs of severe hemorrhage in the pregnant patient. To preserve maternal circulation during hemorrhage, blood is shunted away from the uterus and fetus via uteroplacental vasoconstriction,6,11 making fetal distress, such as decelerations or low variability of the fetal heart rate (the fifth vital sign in obstetrics6), a subtle sign of compensated shock in the mother.
When a pregnant patient is in a supine position, uterine compression of the great vessels (inferior vena cava, abdominal aorta, and iliac arteries) can cause a significant decrease in venous return. This aortocaval compression, or "supine hypotension syndrome," can result in a 30% decrease in cardiac output.9 It also should be noted that the increased venous pressure caused by the gravid uterus may contribute to dangerous hemorrhage from lower-extremity wounds.11 (See Table 2.)
Table 2. Changes in Cardiovascular Physiology
|
Alteration |
Implication |
Action |
|
|
|
|
|
|
|
Supine hypotension syndrome:
|
|
Gastrointestinal. The anatomic changes that develop within the pregnant abdomen may hide significant injury despite a reassuring abdominal exam. As the uterus gradually enlarges, the stretched peritoneal cavity becomes less sensitive to irritation, and the attenuated rectus muscles may prevent guarding.2,13 The spleen becomes engorged and is at greater risk of rupture. The small bowel is displaced cephalad, increasing the risk of bowel injury after penetrating trauma.13,14 (See Table 3.)
Table 3. Changes in Gastrointestinal Physiology
|
Alteration |
Implication |
Action |
|
|
|
|
|
|
|
|
|
Genitourinary. The most significant genitourinary change during pregnancy is the gradually enlarging uterus. During the first trimester, it remains encased and protected by the bony pelvis. By the 12th week of gestation, the uterus rises above the pelvic brim, becoming an abdominal organ. The fetus is small and well-cushioned by a large amount of amniotic fluid throughout the second trimester. In the third trimester, however, the uterus is larger and thin-walled, making it more susceptible to injury.12,13 Further, the marked increase in uterine blood flow in late pregnancy potentiates rapid exsanguination following an injury to the uterus or uterine vessels.14
Toward the end of pregnancy, the fetal head drops into the pelvis and may be injured with maternal pelvic fractures.9 The bladder is more susceptible to injury as the uterus pushes the bladder into the abdomen and out of the protective bony pelvic rim.
Pelvic radiographs may be difficult to interpret in later pregnancy as the pelvis changes in preparation for delivery. These changes include widening of the pubic symphysis and sacroiliac joint space. These areas, therefore, may appear abnormal on pelvic radiographs.
Renal changes include increased renal blood flow by 60% and increased glomerular filtration rate (GFR). As a result, serum creatinine decreases by half. Thus, a "normal" creatinine in a pregnant trauma patient is an important marker of renal impairment.12 In addition, the increased GFR results in an increased urination frequency and renders urine output a poor indicator of shock.13
The elevated levels of progesterone in pregnancy stimulate the medullary respiratory center, increasing ventilatory drive. The physiologic effect is a decrease in pCO2 to 25-30 mmHg, and a compensatory renal excretion of sodium bicarbonate to maintain a normal pH. As a result, maternal buffering capacity is impaired, placing the patient at greater risk for lactic acidosis following hemorrhage.11 (See Table 4.)
Table 4. Changes in Genitourinary Physiology
|
Alteration |
Implication |
Action |
|
|
|
|
|
|
|
|
|
|
|
|
Hematology. During pregnancy, there is a disproportionate increase in red blood cells by 20-30% and plasma volume by 50%, resulting in a "physiologic anemia of pregnancy." A normal hematocrit in pregnancy ranges from 31-34%.11 Pregnancy also causes an increase in all coagulation factors and a decrease in fibrinolysis, creating a hypercoagulable state. This protects against hemorrhage but increases the risk of thromboembolism.13 (See Table 5.)
Table 5. Changes in Hematologic Physiology
|
Alteration |
Implication |
Action |
|
|
|
|
|
|
Injuries Unique to Pregnancy
Placental Abruption. The uterus is made of elastic tissue that can respond to the acceleration and deceleration forces involved in blunt trauma. In contrast, the placenta does not contain elastic tissue and lacks the ability to expand and contract. As a result of the differing properties of these two adjacent structures, trauma may lead to a shearing force that causes a separation of the placenta from the uterus with bleeding into this space, known as placental abruption. Placental abruption is not uncommon and is noted in 40% of cases of severe maternal trauma.6 In these cases, the rate of fetal demise can be as high as 60%,6 making placental abruption the second most common cause of fetal death in trauma after maternal injury.
Concern should be high for placental abruption in the patient with abdominal pain, uterine contractions, back pain, or vaginal bleeding. A rigid uterus or "large for dates" fundal height is highly suggestive of the diagnosis. When uterine abruption is strongly suspected, uterine sonography and cardiotocographic monitoring are recommended. Ultrasound is highly specific for placental abruption, but has a sensitivity of only 50%. This is especially true for small abruptions and those located along the posterior wall of the uterus.3 Abnormalities on fetal monitoring are a highly sensitive marker of fetal distress in the setting of placental abruption, although these findings are nonspecific. The complementary use of these two tools is logical in the ED evaluation of placental abruption. (See Figures 1 and 2.)
Figure 1. Marginal Abruption
Figure 2. Retroplacental Abruption
Placental abruption can also occur after a minor mechanism of injury, with a rate as high as 5%.3 The absence of clinical findings in this setting does not reliably exclude the diagnosis. For stable patients with a viable pregnancy suffering minor trauma, 4-6 hours of continuous fetal monitoring are recommended.
Uterine Rupture. During pregnancy, the uterus enlarges to accommodate the growing fetus. As this occurs, the uterus extends out of the pelvis and into the abdomen, where it is much more susceptible to trauma. Uterine rupture occurs in less than 1% of pregnant trauma patients.10 While this is a rare event, it almost always results in fetal demise, and carries a 10% maternal mortality rate.10 Uterine rupture most commonly occurs in patients who have had a previous cesarean section. Patients will typically present with severe abdominal pain, clinical signs of peritonitis, and hemodynamic instability. Often, fetal parts or uterine irregularity can be palpated on abdominal exam. The combination of shock and an acute abdomen in a pregnant trauma patient should prompt immediate evaluation for uterine rupture, in addition to the traumatic abdominal injuries seen in the general population.
An abdominal radiograph will typically show an uncoiled fetus, and this diagnosis may be confirmed by ultrasound. As time to diagnosis and definitive surgical treatment is critical, time-consuming diagnostic studies should be avoided. The diagnosis of uterine rupture should prompt immediate actions to stabilize the mother and obtain emergent obstetrical consultation.
Fetal-Maternal Hemorrhage. Fetal-maternal hemorrhage occurs when injury provokes the mixing of fetal and maternal blood. This becomes clinically relevant when Rh-positive fetal blood is introduced into the circulation of an Rh-negative mother. As little as 0.001 mL of Rh-positive fetal blood can cause maternal sensitization in the Rh-negative mother.9 If sensitization occurs, future pregnancies could be complicated by erythroblastosis fetalis, resulting in fetal anemia, hypoxia, and even death. Rh status should be determined in all pregnant trauma patients unless the injury is isolated and remote from the uterus (for example, a penetrating injury to the extremity). Universal determination is particularly important, as injury severity is not related to the incidence of fetal-maternal hemorrhage.
Immune globulin should be administered to all Rh-negative trauma patients within 72 hours of injury. During the first trimester, a dose of 50 mcg may be used instead of the traditional dose of 300 mcg, which is used after 13 weeks gestation. If significant fetal-maternal hemorrhage (> 30 mL) is suspected, higher doses of immune globulin may be required. In these cases, a Kleihauer-Betke test may be useful to quantify the degree of transplacental hemorrhage. Recent data also suggest that a positive Kleihauer-Betke test is correlated with uterine contractions and with risk for preterm labor following trauma.15 Patients with a positive Kleihauer-Betke test, therefore, may require more extensive monitoring following trauma.
Assessment and Management
Initial Assessment. The assessment of the injured pregnant patient should be nearly identical to that of the injured nonpregnant patient, with the following important exceptions:
1. The pregnancy must be immediately recognized. This is especially relevant in women who may not realize they are pregnant and in those unable to communicate due to head injury, intoxication, severe respiratory distress, or profound shock. When pregnancy is not clinically obvious, a urine pregnancy test should be done in 100% of injured women of childbearing age. When pregnancy is clinically obvious, the assessment of the fetus occurs during the secondary survey.
2. The normal changes in physiology resulting from the pregnancy must be interpreted in the context of injury.
3. The ability of the pregnant mother to tolerate and respond to specific injuries must be understood.
4. The team must not be distracted by an obviously gravid uterus when a focused assessment and critical interventions are needed to stabilize the mother.
5. Once the mother has been assessed, an appraisal of fetal viability should be performed.
Unique features of the primary assessment and the secondary survey are outlined below.
Airway. The physiologic and anatomic changes of pregnancy significantly affect the respiratory system and airway management. These changes necessitate aggressive airway management and preparation for a potentially difficult airway. All steps should be taken to maximally oxygenate mother and fetus. During advanced stages of pregnancy, the airway will be difficult for two reasons: the upward excursion of the uterus reduces lung volumes, functional residual capacity, and respiratory reserve; and increased intragastric pressure increases the risk of regurgitation. When intubating the pregnant trauma patient, precautions for both aspiration and cervical spine injury should be taken.
Rapid sequence intubation (RSI) is the preferred method for intubation. Traditional RSI medications are safe in pregnancy in the absence of other contraindications. Both depolarizing and non-depolarizing paralytic agents cross the placenta and may result in a flaccid, apneic infant if immediate delivery were to ensue.
Once paralyzed, rapid desaturation is the rule rather than the exception. This is worsened in the presence of acute chest injury. As such, all trauma airways in the pregnant patient should be considered high-risk. To decrease this risk of aspiration, cricoid pressure is vital during airway management.9 Keep in mind that a smaller endotracheal tube than usual may be necessary for successful intubation in the setting of edematous periglottic tissue. Once intubation is accomplished, gastric decompression should be performed to decrease the risk of aspiration.
Breathing. For the reasons outlined above, significant trauma in the second or third trimester of pregnancy is associated with a potentially compromised respiratory status. With limited respiratory reserve, blunt or penetrating chest injuries are not well tolerated. The goal of the physical examination is to identify clinical findings suggestive of chest injury, i.e., tachypnea or respiratory distress, external chest trauma, and clinical signs of rib fractures, flail segments, pneumothorax, or hemothorax. The gradual 4 cm elevation of the diaphragm by the growing uterus is important to remember when placing a chest tube. It should be inserted one to two intercostal spaces higher than standard to avoid diaphragmatic, liver, or spleen injury. Prior to insertion, the chest-tube tunnel should be digitally palpated to ensure proper placement.7
Circulation. In the first trimester, the assessment of circulation is unchanged. In the second and third trimesters, predictable increases in blood volume will mask the typical response to hemorrhage, i.e., hypotension and tachycardia. In essence, the maternal "tank" is over-filled; thus, proportionally larger volumes of blood loss will be required to mount a detectable cardiovascular response. It is equally important to understand that while maternal heart rate climbs in the third trimester, tachycardia (a heart rate ≥ 100 bpm) is not a normal finding.
Large-bore IV access should be obtained as in any trauma patient, and aggressive resuscitation with crystalloid should be initiated if shock is either evident or suspected. If hemodynamic compromise continues despite this, transfusion of type-specific blood is recommended. If time does not allow for this, however, type O, Rh-negative blood should be used.
Vasopressor therapy should be avoided whenever possible. The disadvantage of vasopressor therapy in the pregnant patient is that this compromises perfusion to the uteroplacental unit and, therefore, the fetus.10 If aggressive volume replacement and blood products are ineffective, vasopressor therapy should be initiated at the lowest possible dose to maintain maternal perfusion. Ephedrine and mephentermine offer a theoretical advantage, as these agents do not compromise uterine perfusion to the same extent that epinephrine and norepinepherine do.10
When hypotension is noted in a patient who is greater than 20 weeks gestation, attempts should be made to displace the uterus from the great vessels and restore cardiac output. This is typically achieved by placing the patient in the left lateral decubitus position. In circumstances where spinal precautions must be maintained, displacement of the gravid uterus from the vena cava may be achieved with manual displacement or by raising the backboard to a 15- to 30-degree angle.11 Manual displacement is achieved by manually lifting the uterus and displacing it to the left and toward the patient's head.
If CPR is required, chest compressions should be modified in the pregnant patient. These patients require deeper compressions (1.5-2 inches) with more force than the general population. This is due to decreased chest-wall compliance caused by elevation of the diaphragm. The position of chest compressions also should be shifted from the traditional mid-sternum to slightly above the mid-sternum. Standard ACLS protocols for pharmacologic agents and defibrillation should be followed in the pregnant patient. Electrical therapy with standard joule delivery has never been found to have injurious effects on the fetus.1,16
When obtaining central venous access, lower-extremity sites should be avoided if possible. Drugs administered to sites below the uterus will have difficulty reaching the central circulation due to aortocaval compression.
The Secondary Survey. The secondary survey should be done in the same order and with the same cadence as in any other trauma patient. A methodical head-to-toe examination will help identify injuries posing a threat to both patients.
The examination of the abdomen is especially relevant. Severe tenderness may reflect an injury to maternal viscera or to the enlarged uterus. A large-for-dates uterus may occur following uterine abruption and retroplacental hemorrhage. (See Figure 2.) Palpation of fetal parts outside the uterus reflects uterine rupture.
In the pregnant patient suffering severe multisystem trauma, the pelvic examination should not be overlooked. The exam may reveal vaginal bleeding, rupture of membranes, or vaginal lacerations resulting from pelvic-ring fractures.
It is important to recognize that the physical assessment of the trauma patient has limitations. For example, large studies describe a 5% to 10% rate of "occult" abdominal injuries when patients are evaluated with physical examination alone.17-19 Missed abdominal injuries are especially common in: patients with neurological impairment due to brain injury or alcohol; patients with multiple coincident injuries; and patients with severe or "distracting" injuries. It is logical that the same would apply to the pregnant trauma patient.
Fetal Assessment. Fetal assessment is initiated during the secondary survey of the pregnant trauma patient. Initially, the presence of fetal cardiac activity should be confirmed by Doppler ultrasound. Once this has been established, if a fetus is viable (> 23 weeks gestation), continuous external fetal monitoring should be initiated. Fetal monitoring can be useful for both fetal and maternal assessment, as fetal distress is often an early marker of impending maternal hemodynamic compromise. When significant hemorrhage or hypotension occurs, blood is first shunted away from the uteroplacental unit,1 and fetal distress may be seen before maternal vital signs become abnormal. It is for these reasons that the fetal heart rate is often considered the "fifth vital sign" in the pregnant patient.10
Normal fetal heart rate varies between 120 and 160 beats per minute. Fetal distress can be manifested by bradycardia, tachycardia, loss of beat-to-beat variability, or heart-rate decelerations. A fetal monitoring strip showing a late deceleration is shown in Figures 3 and 4.
Figure 3. Fetal Monitoring Strip
Figure 4. Fetal Monitoring Strip
Assessment of Gestational Age. During the secondary survey, palpation of the fundal height provides a crude assessment of whether the fetus is viable outside of the uterus (≥ 20 weeks gestation) or unlikely to survive outside the uterus (≤ 20 weeks gestation; "pre-viable"). A fundal height at or above the umbilicus identifies a fetus at greater than or equal to 20 weeks gestation. Bedside sonography with measurement of crown-rump length and/or biparietal diameter is a useful adjunct when making this determination.
Pharmacology
Acknowledging limited data, most medications used in the trauma setting have not been proven to be harmful in the human fetus. The pharmacologic strategy used during the resuscitation of the pregnant patient should follow standard American Heart Association guidelines. Successful resuscitation of the mother provides the greatest potential for fetal survival. The following are the safety categories in pregnancy:
A: Controlled studies in pregnant women fail to demonstrate a risk to the fetus in the first trimester with no evidence of risk in later trimesters. The possibility of harm appears remote.
B: Animal studies show no risk or adverse fetal effects, but controlled, human, first-trimester studies are not available; no evidence of second- or third-trimester risk; fetal harm possible but unlikely.
C: Animal studies show adverse fetal effects, but no controlled human studies OR no animal or human studies; weigh possible fetal risk vs. maternal benefit.
D: Positive evidence of human fetal risk; maternal benefit may outweigh fetal risk in serious or life-threatening situations. (See Table 6.)
Table 6. Medications20,21
|
Resuscitative Medications |
Analgesics |
Sedatives/Paralytics |
Other |
|
|
USED |
||||
|
Magnesium (B) |
Acetamino-phen (B) |
Rocuronium (B) |
Ondansetron (B) |
|
|
Atropine (C) |
Oxycodone (B) |
Vecuronium (B) |
Cefazolin (B) |
|
|
Epinephrine (C) |
Fentanyl (C) |
Propofol (B) |
Promethazine (C) |
|
|
Etomidate (C) |
Morphine (C) |
Succinylcholine (C) |
||
|
Lidocaine (C) |
Hydromor-phone (C) |
|||
|
Bicarbonate (C) |
||||
|
Dopamine (C) |
||||
|
Dobutamine (C) |
||||
|
Adenosine (C) |
||||
|
Bretylium (C) |
||||
|
AVOIDED |
||||
|
Ketamine (D) |
Imaging in Pregnancy
Choosing appropriate imaging modalities for the pregnant patient can be anxiety-provoking for the emergency physician (EP) due to concerns about fetal radiation exposure. The imaging strategy should carefully balance the need to rapidly detect and prioritize injuries with the radiation dose required to achieve this goal. Because trauma is the leading non-obstetric cause of maternal death, fast, accurate diagnostics are imperative for both maternal and fetal well-being. Ultimately, injury detection takes priority, and concerns about radiation exposure should neither deter nor delay radiographic imaging in the pregnant trauma patient.22,23
Table 7. Imaging and Fetal Exposure Levels22,23,26,27
|
Modality |
Fetal Exposure |
|
Chest X-ray |
0.0002-0.0007 mGy |
|
Abdominal X-ray |
1 mGy |
|
Pelvis X-ray |
2 mGy |
|
CT Scan Head or Chest |
< 10 mGy |
|
CT Scan Abdomen or Pelvis |
35 mGy |
Effects of Ionizing Radiation Exposure to the Fetus. The effects of ionizing radiation exposure to the fetus depend on gestational age and radiation dose. Most effects are seen at doses that far exceed those typically used for diagnostic imaging. See Table 7 for an overview of the estimated mean fetal-absorbed dose from various radiologic studies. Before implantation (0-2 weeks after conception), there is an all-or-none risk of either death of the embryo or no consequence at all at threshold doses 50-100 mGy.22,24 There is some variable evidence to suggest increased risk of childhood leukemia by a factor of two with a single pelvic CT scan within the first two weeks after conception, but the increase in absolute risk is very low.25 During organogenesis (2-8 weeks after conception), congenital anomalies are seen at 200 mGy and growth retardation at 200-250 mGy. At 8-15 weeks, the risk of severe mental retardation is seen in doses of 60-310 mGy, and at 16-25 weeks in doses of 250-280 mGy.22
Computed Tomography. Computed tomography (CT) is often the imaging modality indicated in trauma evaluation, and this imaging should be pursued without hesitation, although with efforts to use the lowest dose possible to achieve necessary information. When the fetus is out of the imaging field, such as with CT of the head, cervical spine, chest, and extremities, the radiation exposure to the fetus is low, and these images can be safely obtained during any trimester of pregnancy. Because the fetus is in the direct line of radiation for CT of the abdomen and pelvis, the theoretic risk to the fetus is greater, and the EP should work with the radiologist to minimize the radiation dose.23,24 When possible, studies such as ultrasonography and magnetic resonance imaging (MRI) that do not have ionizing radiation should be used for the pregnant patient.22 Shielding of the fetus should be performed for all radiographs, with the exception of pelvic X-rays. Careful attention should be paid to avoid radiographic redundancy.25
Focused Assessment with Sonography for Trauma (FAST). Ultrasound is not associated with known adverse fetal effects.23 Both the technique and the areas of fluid accumulation are the same. The sensitivity and specificity for detection of intra-abdominal injury in the pregnant patient range from 61-83% and 94-100%, respectively.22 Given the possibility of false negatives, a CT scan is often needed for further examination.28
Concluding recommendations from the 2010 EAST practice management guidelines work group as published in The Journal of Trauma are as follows:
"Level II: clinical studies in which data were collected prospectively and retrospective analyses that were based on clearly reliable data. Types of studies so classified include observational studies, cohort studies, prevalence studies, and case-control studies.
1. Concern about possible effects of high-dose ionizing radiation exposure should not prevent medically indicated maternal diagnostic X-rays whenever possible.
2. Exposure to < 5 rad has not been associated with an increase in fetal anomalies or pregnancy loss and is herein deemed to be safe at any point during the entirety of gestation.
3. Ultrasonography and magnetic resonance imaging are not associated with known adverse fetal effects. However, until more information is available, magnetic resonance imaging is not recommended for use in the first trimester.
4. Consultation with radiology should be considered for the purposes of calculating estimated fetal dose when multiple diagnostic radiographs are performed."25
Special Considerations
Perimortem Cesarean Section. A perimortem cesarean section should be performed in cases of traumatic arrest if there is a potentially viable fetus (> 23 weeks). It should be performed by a provider trained and credentialed to perform the procedure. If gestational age is unknown, a rapid method to estimate gestational age is to assume viability if the fundus is palpable above the level of the umbilicus. A bedside ultrasound also may be used to rapidly assess for fetal cardiac activity if immediately available; however, this should not delay the procedure. A study assessing fetal outcome in 33 infants following perimortem cesarean section found that there were survivors as early as 26 weeks gestation, and that none of the 13 infants delivered despite absent fetal heart tones survived.29 This suggests that a rapid assessment for gestational age and fetal heart tones can help the physician determine if a patient is appropriate for perimortem cesarean section.
A perimortem cesarean not only allows for further resuscitation of the infant, but it also relieves uterocaval compression; this increases maternal venous return and cardiac output. In this situation, return of maternal circulation may also occur. CPR and ACLS protocols should be continued during the procedure. Ideally, perimortem cesarean section should begin within 4 minutes of maternal cardiac arrest, with a goal of delivery within 5 minutes of maternal cardiac arrest. This timing is recommended because improved fetal outcome has been demonstrated when delivery is within 5 minutes of maternal cardiac arrest.30,31 Data from Katz's study demonstrate that 70% of infants who survived perimortem cesarean section were delivered within 5 minutes of maternal arrest. However, there have been case reports of return of spontaneous maternal circulation and normal fetal neurologic outcome after more than 15 minutes following maternal arrest, so arrest time greater than 5 minutes is not a contraindication to perimortem cesarean delivery.32
Domestic Violence During Pregnancy. When caring for the pregnant trauma patient, careful consideration should be made for the possibility of physical abuse. Domestic violence rates are increased during pregnancy, as this is frequently a time of both emotional and financial strain. The rate of violence during pregnancy is estimated at 10-15%.3 Furthermore, the vast majority of physical assaults on pregnant patients are perpetrated by boyfriends and spouses, and are likely to be significantly underreported. Assaults on pregnant patients tend to recur and to increase in severity throughout the pregnancy. Common areas of injury during pregnancy include the abdomen, breasts, and genitals.32 Other warning signs include frequent office or emergency department visits, depression, substance abuse, and a history inconsistent with injury. It is recommended that all pregnant trauma patients be screened for domestic violence. If possible, screening should be performed without the presence of partners or family members.
Burns. Approximately 7% of women seen for the treatment of burns in the United States are pregnant. Most of these events occur in the workplace.26 Fetal outcomes are closely linked to burn severity. As the total body surface area (TBSA) of the burn increases, so does the risk of poor fetal outcomes and fetal death. In general, uncomplicated burns of less than 20% TBSA will have little effect on fetal well-being. Burns greater than 30% can lead to fetal distress and premature labor. Fetal survival is uncommon when burns exceed 60% TBSA.34
There are insufficient data in the literature to develop specific guidelines for the management of burns in the pregnant patient. Most recommendations are based on small case series or are extrapolated from nonpregnant patients. With that in mind, several recommendations can be made with regard to airway management and fluid resuscitation.
In the patient suffering major burns and/or smoke inhalation, careful and early attention to airway management is of paramount importance. In the third trimester, tidal volume and minute ventilation both increase by 30% to 50%. As such, impaired ventilation and gas exchange due to upper airway edema, inhalation injury, or concomitant chest injury can profoundly impair maternal and fetal physiology.
RSI is the technique of choice when intubation is required. Because gravid patients desaturate rapidly following paralysis, careful preparation and planning are fundamental. It is important to recall that acute burns are not a contraindication to the use of succinylcholine as the preferred neuromuscular blocking agent. Conversely, succinylcholine should be avoided in subacute burns (i.e., ≥ 72 hours old) to avoid drug-induced hyperkalemia. When upper-airway burn edema threatens the success of laryngoscopy, alternative techniques should be considered as the primary approach, or immediately available as part of a "double set-up."
Table 8. Parkland Formula26,34
- Fluid requirement = TBSA burned (%) × Weight (kg) × 4 mL
- Half given in the first 8 hours and half over the next 16 hours
- Normal saline or lactated Ringer's solution
Use of the Parkland formula (see Table 8), which has not been validated in the pregnant patient, is controversial. Pacheco and colleagues35 argue that predictable physiologic changes occurring during pregnancy create an inherent risk of under-resuscitation if the Parkland formula is used: pregnancy is a hyperdynamic state with an increase in cardiac output, a drop in systemic vascular resistance, and increased overall metabolic demands; intravascular volume requirements increase by 50% at term; decreases in colloid osmotic pressure increase tissue fluid extravasation; and total body surface area is increased, promoting burn-surface fluid loss. Without outcome data or guidance to the contrary, the Parkland formula seems like a logical starting point. To ensure adequate resuscitation, ongoing monitoring of vital signs, urine output, cardiotocographic monitoring, and objective measures of tissue perfusion (e.g., serial serum lactate or base deficit) is important.
Burn cleansing and debridement should be done in standard fashion. Topical antibiotics, such as bacitracin and silver sulfadiazine, and biosynthetic dressings (e.g., Biobrane®, TransCyte®, Aquacel®) are not associated with fetal malformations and are considered safe in pregnancy.36
Victims of major burns, and all those burned in an enclosed space, should be assessed for carbon monoxide (CO) poisoning. Because fetal hemoglobin avidly binds CO, hyperbaric oxygen is recommended for all symptomatic pregnant patients and asymptomatic patients with a venous CO level greater than 15%.37
Electrical Injury. Traditional teaching emphasizes that even low-voltage electrical injuries are associated with a significant risk of poor fetal outcomes and fetal demise.38-40 Pathophysiologically, this is attributable to the high conductivity of amniotic fluid, putting the fetus at risk when the offending current "crosses" the uterus. There is no debate that major electrical injuries, lightning strikes, and Taser-gun injuries pose a major risk.41,42
A review of 31 patients by Einarson and colleagues points out that most electric injuries in pregnancy are due to 110 V household current, with no proven difference in outcomes.43 Given the lack of certainty on this issue, it seems reasonable to assess fetal well-being immediately in all pregnant patients suffering electric injury. In the absence of fetal distress and maternal indications for admission (loss of consciousness, persistent neurological symptoms, history of cardiac disease, abnormal maternal ECG), a 4-hour period of fetal monitoring is reasonable. With most significant maternal injuries or any signs of fetal distress, immediate obstetric consultation and a longer period of maternal and fetal monitoring are indicated.
Conclusion
Management of the injured pregnant patient presents unique challenges to the emergency physician. A thorough knowledge of the differences between a pregnant and a non-pregnant trauma patient is imperative to adequately care for the pregnant trauma patient. Ultimately, maternal stabilization should be the primary focus to ensure the best possible outcome for both mother and fetus.
References
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2. Fildes J, Reed L, et al. Trauma: The leading cause of maternal death. J Trauma 1992;32:643-645.
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Resuscitation in the pregnant patient is an uncommon occurrence, estimated at 1 in 30,000 deliveries, yet it is unique in its potential to save not one, but two lives.Subscribe Now for Access
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