Laboratory Studies
Laboratory studies in the evaluation of the pregnant trauma patient may include the following:
-
Determination of CBC: Pregnancy-induced leukocytosis peaks to levels of 12,000-18,000 per cubic millimeter during the third trimester. During labor, levels as high as 25,000 per cubic millimeter may occur.
-
Determination of electrolyte and glucose levels
-
Blood typing and crossmatching
-
Rhesus (Rh) blood group determination (Administer Rho(D) immune globulin [RhoGAM] if the mother is Rh negative)
-
Urine pregnancy testing, if the status is unknown in a female of reproductive age with trauma
-
Urinalysis
-
Assessment of coagulation profile (Most coagulation factors rise throughout pregnancy, although laboratory values remain unchanged except for fibrinogen levels, which nearly double in value.)
-
Kleihauer-Betke testing: This test (an acid elution test in which adult hemoglobin is eliminated while fetal hemoglobin is resistant and hence stains) is used to detect fetal-to-maternal hemorrhage in excess of that which can be treated with a standard dose of 300 mcg of Rho(D) immune globulin (RhoGAM). In the event of fetal distress, a positive test result may indicate life-threatening hemorrhage in the fetal circulation. The test is useful in Rh-negative mothers because the standard dose of RhoGAM (300 mcg) covers only up to 15 mL of fetal red cells (30 mL of fetal whole blood). In major trauma, additional fetal red cells may come into contact with maternal blood, and the Kleihauer-Betke test helps to determine how much additional RhoGAM to administer. Although this test is usually only indicated for the Rh-negative pregnant patient with major trauma, some advocate its use in all patients as it may correlate with risk for preterm labor. However, it is neither sensitive nor specific for this outcomesoit should be used with caution or not at all.
-
Toxicology screening
-
D-dimer: Some obstetricians advocate use of D-dimer testing to help in determining the course of action for placental abruption.
-
Base deficit: In patients with blunt abdominal trauma, data show that base deficit is an early available important indicator to identify intra-abdominal injury. [9]
Imaging Studies
Radiologic examinations must be interpreted in the context of pregnancy-related changes. For example, increased AP diameters, mild pulmonary vascular cephalization, cardiomegaly, and a slightly widened mediastinum are seen in normal pregnancy. Similarly, pelvic radiographs show normal widening of the sacroiliac joints and symphysis pubis.
Radiologic examinations should not be deferred because of the presence of the fetus. Data about injury to the fetus secondary to diagnostic radiology are only suggestive. The 3 primary concerns are the following: radiation-induced cancer, loss of viability, and radiation-induced malformation (small head size). Usually, adverse effects are not expected until the dose is in the 50-100 mGy range (mGy = 0.1 rad). The acquisition of an anteroposterior pelvic radiograph delivers a 0.16-mGy dose to the fetus, while typical dose from CT scanning of the pelvis is approximately 20-50 mGy.
Data about radiation-induced cancer after in utero exposure suggest that risks for radiation-induced cancer fatality, in children younger than 14 years, may be on the order of 1 in 15,000 children. These results occur when each fetus is exposed to 1 mGy of radiation in utero during the second or third trimester. The risk ratio for a 50-mGy exposure is about 1:300. Risk of first-trimester exposure may be higher, but data are less specific.
Loss of viability of the fetus is possible if radiation exposure occurs within 2 weeks of conception. For most diagnostic abdominal examinations, this risk probably is less than 1%. All risk estimates related to this possibility at diagnostic dose levels are derived from animal data. Data suggest that, during this period, no increased risk of malformation exists.
Malformation (small head size) is also a concern. Findings from animal studies suggest a threshold of about 100 mGy, with the most vulnerable period during embryonic development (2-8 wk after conception). Data collected from those affected by the bombings of Hiroshima and Nagasaki suggest that head size may be slightly reduced as a result of exposure to radiation (< 200 mGy). However, reduction in intelligence did not occur when exposure occurred during the 2nd to 8th weeks after conception. A tendency toward induced intellectual deficit from the 8th to 15th weeks after conception was observed (during this period, the brain undergoes rapid neuron development and migration); however, data are uncertain.
As a general rule, abdominal CT should be avoided in early pregnancy because other diagnostic modalities, such as ultrasonography and diagnostic peritoneal lavage, are acceptable alternatives. CT does, however, allow for better visualization of retroperitoneal and intrauterine injuries. Head and chest CT may be used when indicated because the amount of radiation is much less and because few, if any, alternative diagnostic modalities exist.
Ultrasonography
Assess fetal viability and for multiple gestations.
Assess the size, gestational age, and position of the fetus.
Ultrasonography can depict free intraperitoneal fluid or hemorrhage in the mother. The focused assessment with sonography for trauma (FAST) examination has become routine in many trauma centers and has been shown to have high sensitivity and accuracy in the hands of emergency clinicians and trauma surgeons.
MRI
No reports of adverse effects (but few data) exist.
Ventilation-perfusion (V/Q) scanning
No reports of adverse effects (but few data) exist.
Other Tests
Cardiotocographic monitoring
All pregnant trauma victims of 20-24 weeks of gestational age or greater should be placed on a fetal monitor.
Fetal distress may be the first sign of maternal hemodynamic compromise because the mother will maintain her vital signs by shunting blood away from the relatively low-resistance uterus.
A minimum of 4 hours of monitoring is suggested, even after minor abdominal or flank trauma, to identify patients that might experience placental abruption. This is because clinical signs and symptoms or abruption, such as vaginal bleeding, abdominal pain and tenderness, and uterine tenderness, are often absent.
Monitoring for 24 hours is suggested with major trauma or signs of obstetric decompensation, such as persistent uterine contractions, vaginal bleeding, premature rupture of the membranes, or fetal heart rate tracing that causes concern.
Ultrasonography has less than 50% sensitivity in diagnosing placental abruption because the density of a fresh clot of blood behind the placenta is the same as the placenta itself.
Electrocardiography
The electrocardiography (ECG) may change as the diaphragm elevates.
It may show a left-axis deviation with flattened T waves and, possibly, a Q wave in leads III and aVF.
Do not mistake these changes for the ischemic or traumatic changes in blunt chest trauma.
Procedures
Diagnostic peritoneal lavage (DPL)
This study is rarely used nowadays with the advent of ultrasonography. It may be indicated in the pregnant patient where avoidance of radiation exposure through the use of CT is desired and in whom ultrasonography is either unavailable or equivocal. DPL is safe if performed above the umbilicus with an open technique (lower risk of complications such as inadvertent uterine and fetal injury).
Perimortem cesarean delivery
This is performed for two indications: In the case of certain maternal death due to severe head injury or other non-resuscitatable cause, the indication is to save the fetus. In the case of maternal cardiac arrest due to a potentially resuscitatable cause such as a cardiac event or severe blood loss, the indication for the perimortem cesarean delivery is to remove the fetus so as to remove a nonvital organ from the maternal circulation and therefore facilitate the resuscitation.
In either indication, perform this within 4 minutes of cardiac arrest to support neurologic function of the fetus.
The key to rapid delivery is the use of large of incisions.
Perform a midline vertical incision from the xiphoid to the pubis through all layers of the abdominal wall. If the placenta is in an anterior position, cut through it and address the bleeding only after the fetus is delivered.
Perform a midline vertical incision through the upper uterine segment.
Then, remove the neonate, perform suctioning, clamp and cut the cord, and resuscitate the neonate.
Continue resuscitation of the mother.
