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<< Trauma In Pregnancy: Double Jeopardy (2008)
Diagnostic Studies
Laboratory Tests
A trauma laboratory panel is ordered following major trauma and generally includes a complete blood count, basic chemistry panel, toxicology screen, and lactate and base deficit. It should be taken into account when interpreting these laboratory panels that the physiological changes of pregnancy alter some laboratory values. One of the most critical changes to be aware of in the setting of trauma is the physiologic anemia of pregnancy. Blood volume increases by 50% in pregnancy with red blood cell production increasing by only about 30%, resulting in a dilutional “anemia.” Some of the other laboratory values that are changed in pregnancy are:
Elevated D-dimer, decreased fibrinogen, and elevated fibrin split products may be seen with abruption of the placenta but are not sensitive or specific and cannot be used to definitely rule out abruption.
Kleihauer-Betke Testing
There is some controversy in the literature regarding the utility of routine use of Kleihauer-Betke (KB) testing in pregnancy. The KB test detects the presence of fetal cells in the maternal circulation and is used as an indicator of maternal fetal hemorrhage. Currently, the test is an acid elution test based on the relative greater stability of fetal hemoglobin in an acid solution, but newer flow cytometry techniques may provide greater accuracy.
It is estimated that as little as 0.0001 mL of fetal blood can cause maternal sensitization in Rh-negative mothers. Therefore, the American College of Emergency Physicians and the American College of Obstetrics and Gynecology recommend the routine administration of Rho(D) immune globulin (RhIG) to all Rh-negative mothers following even minor trauma.5,15 In major trauma, it is generally accepted to use the KB test to determine the need to administer additional doses of RhIG. The dose is 30 mL of RhIG for every 30 cc of fetal hemorrhage.
The utility of using the KB test routinely for all pregnant trauma patients as a general predictor of obstetric complications is unclear. One study examined the incidence of positive KB tests in a retrospective cohort of 151 pregnant trauma patients as compared to 100 asymptomatic patients in a prenatal clinic; it found no difference in the number of positive tests. Of note, there were very few positive tests in each group (2.6% and 5.1% respectively). The authors concluded that the KB test was not specific for abruption of the placenta and provided no clinically useful information as a screening test.16 Another retrospective review of 71 pregnant trauma patients found that independent of the severity of illness, a positive KB test was a predictor of preterm labor; conversely, none of the 46 patients with a negative KB test went on to have contractions. This study recommended routine use of the KB test to screen patients who are more at risk for preterm labor or abruption and to limit the duration of monitoring in asymptomatic patients with a negative test.17 Further prospective research with larger numbers of patients may help shed light on this issue.
Diagnostic Imaging In Pregnant Trauma Patients
X-rays and computed tomography (CT) scans are a standard part of the initial evaluation of a trauma patient, and a patient will often receive several radiographic studies following a major trauma. Balancing the risk of radiation exposure to the fetus with the need to diagnose injuries in the mother is an important consideration. The East Society of Trauma Surgeons and the American College of Obstetrics and Gynecology have issued guidelines that are helpful when making decisions regarding imaging in pregnancy.2,4 It is well established that exposure of the fetus to less than 5 rads is considered safe.4 Table 3 lists the radiation dose to the fetus from common studies performed in pregnancy. Multiple studies can be performed as needed and still be well below this threshold. Of course, it is beneficial to avoid unnecessary studies and place a lead shield over the fetus if possible.
Ultrasound
Ultrasound has become an important tool in the assessment of the pregnant patient with trauma. A retrospective review of 3976 female trauma patients found that 114 were pregnant and incidental pregnancy was diagnosed at the time of the trauma in 13 patients.18 In a follow-up study of 144 patients, ultrasound detected the new pregnancy in 8 of 9 patients with a gestational age of less than 8 weeks; the authors recommended using ultrasound as a screening tool for pregnancy in female trauma patients of reproductive age.19 Focused abdominal sonography in trauma (FAST) has been well established for the detection of intraperitoneal hemorrhage following trauma. In a retrospective review of 127 pregnant patients who had FAST examinations, ultrasound detected hemoperitoneum in 5 of 6 patients with hemoperitoneum at surgery. While the study has a small number of injuries, the FAST examination seems to have a similar accuracy in pregnant as well as non-pregnant patients (Figure 2).20 Ultrasound can also be used to quickly assess the pregnancy, with documentation of the fetal heart rate, and the presence of amniotic fluid (Figures 2, 3, and 4).21
Magnetic Resonance Imaging
Early evidence suggests that in pregnant patients with non-traumatic abdominal pain, magnetic resonance imaging (MRI) is a reasonable option to avoid the radiation associated with CT scans. It is plausible that MRI may soon provide a viable alternative to evaluate for intraabdominal injuries following trauma as well, but this has not been well studied to date.
Diagnostic Peritoneal Lavage
There is very little in the literature discussing the use of diagnostic peritoneal lavage (DPL) to detect intraperitoneal hemorrhage in pregnant patients. A recent study describes experience with 2500 DPLs in one trauma center. In this series, 92 patients were pregnant and DPL was performed using an open supraumbilical approach with no complications.22 Most reviews recommend using the open technique on pregnant patients to avoid inadvertently puncturing the uterus with the catheter.1,10One obvious advantage of DPL is the avoidance of radiation from a CT scan. However, many solid organ injuries no longer require an operation, and in a hemodyamically stable patient, it is likely that a positive DPL would be followed by a CT scan to determine the specific source of the hemorrhage. One possible role for a DPL would be the rapid triage of an unstable hypotensive patient to determine if the source of the hemorrhage is intraabdominal. Even so, DPL is rarely performed on pregnant patients in most centers.
Cardiac Toco Monitoring
As soon as the mother is stabilized, a cardiac toco monitor should be placed to assess the fetal heart rate and the presence of uterine contractions. Fetal distress is often the first sign of placental abruption and may be an early sign of impending hemorrhagic shock in the mother. The normal fetal heart rate is 110-160 BPM. Fetal distress may manifest by fetal heart rate decelerations, tachycardia, bradycardia, or a flat baseline. Figure 5illustrates examples of these changes. In general, every patient over 20 weeks should have a period of cardiac toco monitoring following major or even minor trauma directly to the abdomen. Some authors recommend 4 hours of monitoring; others, including the EAST guidelines, recommend 6 hours of monitoring.2,10,12 If uterine contractions or fetal heart rate abnormalities are seen, the patient should be admitted for monitoring for at least 24 hours.
A trauma laboratory panel is ordered following major trauma and generally includes a complete blood count, basic chemistry panel, toxicology screen, and lactate and base deficit. It should be taken into account when interpreting these laboratory panels that the physiological changes of pregnancy alter some laboratory values. One of the most critical changes to be aware of in the setting of trauma is the physiologic anemia of pregnancy. Blood volume increases by 50% in pregnancy with red blood cell production increasing by only about 30%, resulting in a dilutional “anemia.” Some of the other laboratory values that are changed in pregnancy are:
- Decreased hematocrit
- Decreased blood urea nitrogen (BUN)
- Increased white blood cell count
- Decreased platelets
- Increased clotting factors
- Increased D-dimer, fibrinogen
Elevated D-dimer, decreased fibrinogen, and elevated fibrin split products may be seen with abruption of the placenta but are not sensitive or specific and cannot be used to definitely rule out abruption.
Kleihauer-Betke Testing
There is some controversy in the literature regarding the utility of routine use of Kleihauer-Betke (KB) testing in pregnancy. The KB test detects the presence of fetal cells in the maternal circulation and is used as an indicator of maternal fetal hemorrhage. Currently, the test is an acid elution test based on the relative greater stability of fetal hemoglobin in an acid solution, but newer flow cytometry techniques may provide greater accuracy.
It is estimated that as little as 0.0001 mL of fetal blood can cause maternal sensitization in Rh-negative mothers. Therefore, the American College of Emergency Physicians and the American College of Obstetrics and Gynecology recommend the routine administration of Rho(D) immune globulin (RhIG) to all Rh-negative mothers following even minor trauma.5,15 In major trauma, it is generally accepted to use the KB test to determine the need to administer additional doses of RhIG. The dose is 30 mL of RhIG for every 30 cc of fetal hemorrhage.
The utility of using the KB test routinely for all pregnant trauma patients as a general predictor of obstetric complications is unclear. One study examined the incidence of positive KB tests in a retrospective cohort of 151 pregnant trauma patients as compared to 100 asymptomatic patients in a prenatal clinic; it found no difference in the number of positive tests. Of note, there were very few positive tests in each group (2.6% and 5.1% respectively). The authors concluded that the KB test was not specific for abruption of the placenta and provided no clinically useful information as a screening test.16 Another retrospective review of 71 pregnant trauma patients found that independent of the severity of illness, a positive KB test was a predictor of preterm labor; conversely, none of the 46 patients with a negative KB test went on to have contractions. This study recommended routine use of the KB test to screen patients who are more at risk for preterm labor or abruption and to limit the duration of monitoring in asymptomatic patients with a negative test.17 Further prospective research with larger numbers of patients may help shed light on this issue.
Diagnostic Imaging In Pregnant Trauma Patients
X-rays and computed tomography (CT) scans are a standard part of the initial evaluation of a trauma patient, and a patient will often receive several radiographic studies following a major trauma. Balancing the risk of radiation exposure to the fetus with the need to diagnose injuries in the mother is an important consideration. The East Society of Trauma Surgeons and the American College of Obstetrics and Gynecology have issued guidelines that are helpful when making decisions regarding imaging in pregnancy.2,4 It is well established that exposure of the fetus to less than 5 rads is considered safe.4 Table 3 lists the radiation dose to the fetus from common studies performed in pregnancy. Multiple studies can be performed as needed and still be well below this threshold. Of course, it is beneficial to avoid unnecessary studies and place a lead shield over the fetus if possible.
Ultrasound
Ultrasound has become an important tool in the assessment of the pregnant patient with trauma. A retrospective review of 3976 female trauma patients found that 114 were pregnant and incidental pregnancy was diagnosed at the time of the trauma in 13 patients.18 In a follow-up study of 144 patients, ultrasound detected the new pregnancy in 8 of 9 patients with a gestational age of less than 8 weeks; the authors recommended using ultrasound as a screening tool for pregnancy in female trauma patients of reproductive age.19 Focused abdominal sonography in trauma (FAST) has been well established for the detection of intraperitoneal hemorrhage following trauma. In a retrospective review of 127 pregnant patients who had FAST examinations, ultrasound detected hemoperitoneum in 5 of 6 patients with hemoperitoneum at surgery. While the study has a small number of injuries, the FAST examination seems to have a similar accuracy in pregnant as well as non-pregnant patients (Figure 2).20 Ultrasound can also be used to quickly assess the pregnancy, with documentation of the fetal heart rate, and the presence of amniotic fluid (Figures 2, 3, and 4).21
Magnetic Resonance Imaging
Early evidence suggests that in pregnant patients with non-traumatic abdominal pain, magnetic resonance imaging (MRI) is a reasonable option to avoid the radiation associated with CT scans. It is plausible that MRI may soon provide a viable alternative to evaluate for intraabdominal injuries following trauma as well, but this has not been well studied to date.
Diagnostic Peritoneal Lavage
There is very little in the literature discussing the use of diagnostic peritoneal lavage (DPL) to detect intraperitoneal hemorrhage in pregnant patients. A recent study describes experience with 2500 DPLs in one trauma center. In this series, 92 patients were pregnant and DPL was performed using an open supraumbilical approach with no complications.22 Most reviews recommend using the open technique on pregnant patients to avoid inadvertently puncturing the uterus with the catheter.1,10One obvious advantage of DPL is the avoidance of radiation from a CT scan. However, many solid organ injuries no longer require an operation, and in a hemodyamically stable patient, it is likely that a positive DPL would be followed by a CT scan to determine the specific source of the hemorrhage. One possible role for a DPL would be the rapid triage of an unstable hypotensive patient to determine if the source of the hemorrhage is intraabdominal. Even so, DPL is rarely performed on pregnant patients in most centers.
Cardiac Toco Monitoring
As soon as the mother is stabilized, a cardiac toco monitor should be placed to assess the fetal heart rate and the presence of uterine contractions. Fetal distress is often the first sign of placental abruption and may be an early sign of impending hemorrhagic shock in the mother. The normal fetal heart rate is 110-160 BPM. Fetal distress may manifest by fetal heart rate decelerations, tachycardia, bradycardia, or a flat baseline. Figure 5illustrates examples of these changes. In general, every patient over 20 weeks should have a period of cardiac toco monitoring following major or even minor trauma directly to the abdomen. Some authors recommend 4 hours of monitoring; others, including the EAST guidelines, recommend 6 hours of monitoring.2,10,12 If uterine contractions or fetal heart rate abnormalities are seen, the patient should be admitted for monitoring for at least 24 hours.
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