Trauma
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Question 30 of 216
A 25 year old woman, known to be pregnant, is brought into ED by ambulance following a major road traffic collision. She is haemodynamically unstable and you are considering your potential options for management of both mother and foetus. Which of the following is an assessment of foetal viability?
Answer:
Foetal viability is the ability of a human foetus to survive outside the uterus. In a trauma or cardiac arrest situation, a quick assessment of foetal viability is obtained by palpating the fundal height. Once the fundus reaches the level of the umbilicus, the fundal height in centimeters is approximately equivalent to the gestational age (i.e. 24 cm, 30 cm, and 34 cm measured from the symphysis pubis to the fundus is approximately equivalent to 24, 30, and 34 weeks' gestation, respectively). At 20 weeks' gestation the fundus is at the level of the umbilicus. Twenty-three to 24 weeks' gestation is considered the minimum age for foetal viability. In view of this, when the fundal height is 3–4 cm or more above the umbilicus the foetus should be considered as potentially viable (conversely, if fundal height is below the umbilicus, the foetus is unlikely to be viable).Trauma in Pregnancy
Obstetrics & Gynaecology / Trauma
Last Updated: 13th February 2021
Anatomical differences in pregnancy
- The uterus remains an intrapelvic organ until approximately the 12th week of gestation, when it begins to rise out of the pelvis. By 20 weeks, the uterus is at the umbilicus, and at 34 to 36 weeks, it reaches the costal margin. During the last 2 weeks of gestation, the fundus frequently descends as the fetal head engages the pelvis.
- As the uterus enlarges, the intestines are pushed cephalad, so that they lie mostly in the upper abdomen. As a result, the bowel is somewhat protected in blunt abdominal trauma, whereas the uterus and its contents (fetus and placenta) become more vulnerable. However, penetrating trauma to the upper abdomen during late gestation can result in complex intestinal injury because of this cephalad displacement. Clinical signs of peritoneal irritation are less evident in pregnant women; therefore, physical examination may be less informative. When major injury is suspected, further investigation is warranted.
- During the first trimester, the uterus is a thick walled structure of limited size, confined within the bony pelvis. During the second trimester, it enlarges beyond its protected intrapelvic location, but the small fetus remains mobile and cushioned by a generous amount of amniotic fluid. The amniotic fluid can cause amniotic fluid embolism and disseminated intravascular coagulation following trauma if the fluid enters the maternal intravascular space. By the third trimester, the uterus is large and thin-walled. In the vertex presentation, the fetal head is usually in the pelvis, and the remainder of the fetus is exposed above the pelvic brim. Pelvic fracture(s) in late gestation can result in skull fracture or serious intracranial injury to the fetus. Unlike the elastic myometrium, the placenta has little elasticity. This lack of placental elastic tissue results in vulnerability to shear forces at the uteroplacental interface, which may lead to placental abruption.
- The placental vasculature is maximally dilated throughout gestation, yet it is exquisitely sensitive to catecholamine stimulation. An abrupt decrease in maternal intravascular volume can result in a profound increase in uterine vascular resistance, reducing fetal oxygenation despite reasonably normal maternal vital signs.
Physiological differences in pregnancy
- Blood volume and composition
- Plasma volume increases steadily throughout pregnancy and plateaus at 34 weeks of gestation.
- A smaller increase in red blood cell (RBC) volume occurs, resulting in a decreased haematocrit level (i.e. physiological anaemia of pregnancy). In late pregnancy, a haematocrit level of 31% to 35% is normal.
- Healthy pregnant patients can lose 1,200 to 1,500 mL of blood before exhibiting signs and symptoms of hypovolemia. However, this amount of haemorrhage may be reflected by fetal distress, as evidenced by an abnormal fetal heart rate.
- The white blood cell (WBC) count increases during pregnancy. It is not unusual to see WBC counts of 12,000/mm3 during pregnancy or as high as 25,000/mm3 during labour.
- Levels of serum fibrinogen and other clotting factors are mildly elevated. Prothrombin and partial thromboplastin times may be shortened, but bleeding and clotting times are unchanged.
- Cardiovascular system
- Cardiac output: After the 10th week of pregnancy, cardiac output can increase by 1.0 to 1.5 L/min because of the increase in plasma volume and decrease in vascular resistance of the uterus and placenta, which receive 20% of the patient’s cardiac output during the third trimester of pregnancy. This increased output may be greatly influenced by the mother’s position during the second half of pregnancy. In the supine position, vena cava compression can decrease cardiac output by 30% because of decreased venous return from the lower extremities.
- Heart rate: During pregnancy, the heart rate gradually increases to a maximum of 10–15 beats per minute over baseline by the third trimester. This change in heart rate must be considered when interpreting a tachycardic response to hypovolaemia.
- Blood pressure: Pregnancy results in a fall of 5 to 15 mmHg in systolic and diastolic pressures during the second trimester, although blood pressure returns to near normal levels at term. Some pregnant women exhibit hypotension when placed in the supine position, due to compression of the inferior vena cava. This condition can be corrected by relieving uterine pressure on the inferior vena cava. Hypertension in the pregnant patient may represent preeclampsia if accompanied by proteinuria.
- Venous pressure: The resting central venous pressure (CVP) is variable with pregnancy, but the response to volume is the same as in the non-pregnant state. Venous hypertension in the lower extremities is present during the third trimester.
- ECG: The axis may shift leftward by approximately 15 degrees. Flattened or inverted T waves in leads III and AVF and the precordial leads may be normal. Ectopic beats are increased during pregnancy.
- Respiratory system
- Minute ventilation increases primarily due to an increase in tidal volume. Hypocapnia (PaCO2 of 30 mm Hg) is therefore common in late pregnancy. A PaCO2 of 35 to 40 mm Hg may indicate impending respiratory failure during pregnancy.
- Anatomical alterations in the thoracic cavity seem to account for the decreased residual volume associated with diaphragmatic elevation, and a chest x-ray reveals increased lung markings and prominence of the pulmonary vessels.
- Oxygen consumption increases during pregnancy. Thus it is important to maintain and ensure adequate arterial oxygenation when resuscitating injured pregnant patients.
- In patients with advanced pregnancy, when chest tube placement is required it should be positioned higher to avoid intra-abdominal placement given the elevation of the diaphragm.
- Administer supplemental oxygen to maintain a saturation of 95%. The fetus is very sensitive to maternal hypoxia, and maternal basal oxygen consumption is elevated at baseline.
- Gastrointestinal system
- Gastric emptying is delayed during pregnancy, so early gastric tube decompression may be particularly important to prevent aspiration of gastric contents.
- The mother’s intestines are relocated to the upper part of the abdomen and may be shielded by the uterus. The solid viscera remain essentially in their usual anatomic positions.
- Urinary system
- The glomerular filtration rate and renal blood flow increase during pregnancy, whereas levels of serum creatinine and urea nitrogen fall to approximately one-half of normal pre-pregnancy levels.
- Glycosuria is common during pregnancy.
- Musculoskeletal system
- The symphysis pubis widens to 4 to 8 mm, and the sacroiliac joint spaces increase by the seventh month of gestation. These factors must be considered in interpreting x-ray films of the pelvis.
- The large, engorged pelvic vessels surrounding the gravid uterus can contribute to massive retroperitoneal bleeding after blunt trauma with associated pelvic fractures.
- Neurological system
- Eclampsia is a complication of late pregnancy that can mimic head injury. It may be present if seizures occur with associated hypertension, hyperreflexia, proteinuria, and peripheral oedema.
- Expert neurological and obstetrical consultation frequently is helpful in differentiating among eclampsia and other causes of seizures.
Mechanism of Injury
- Blunt injury
- The abdominal wall, uterine myometrium, and amniotic fluid act as buffers to direct fetal injury from blunt trauma. However, fetal injuries may occur when the abdominal wall strikes an object, such as the dashboard or steering wheel, or when a pregnant patient is struck by a blunt instrument. Indirect injury to the fetus may occur from rapid compression, deceleration, the contrecoup effect, or a shearing force resulting in placental abruption.
- Compared with restrained pregnant women involved in collisions, unrestrained pregnant women have a higher risk of premature delivery and fetal death. The type of restraint system affects the frequency of uterine rupture and fetal death. Using a lap belt alone allows forward flexion and uterine compression with possible uterine rupture or placental abruption. A lap belt worn too high over the uterus may produce uterine rupture because it transmits direct force to the uterus on impact. Using shoulder restraints in conjunction with a lap belt reduces the likelihood of direct and indirect fetal injury, presumably because the shoulder belt dissipates deceleration force over a greater surface area and helps prevent the mother from flexing forward over the gravid uterus. Therefore, in the overall assessment it is important to determine the type of restraint device worn by the pregnant patient, if any. The deployment of airbags in motor vehicles does not appear to increase pregnancy-specific risks.
- Penetrating injury
- As the gravid uterus grows larger, the other viscera are relatively protected from penetrating injury. However, the likelihood of uterine injury increases. The dense uterine musculature in early pregnancy can absorb a significant amount of energy from penetrating objects, decreasing their velocity and lowering the risk of injury to other viscera. The amniotic fluid and fetus also absorb energy and contribute to slowing of the penetrating object. The resulting low incidence of associated maternal visceral injuries accounts for the generally excellent maternal outcome in cases of penetrating wounds of the gravid uterus. However, fetal outcome is generally poor when there is a penetrating injury to the uterus.
Assessment and management
To optimise outcomes for the mother and fetus, clinicians must assess and resuscitate the mother first and then assess the fetus before conducting a secondary survey of the mother.
Primary survey
- Mother
- Ensure a patent airway, adequate ventilation and oxygenation, and effective circulatory volume.
- If ventilatory support is required, intubate pregnant patients, and consider maintaining the appropriate PCO2 for her stage of pregnancy (e.g. approximately 30 mmHg in late pregnancy).
- Uterine compression of the vena cava may reduce venous return to the heart, thus decreasing cardiac output and aggravating the shock state. Manually displace the uterus to the left side to relieve pressure on the inferior vena cava. If the patient requires spinal motion restriction in the supine position, logroll her to the left 15–30 degrees (i.e. elevate the right side 4–6 inches), and support with a bolstering device, thus maintaining spinal motion restriction and decompressing the vena cava.
- Because of their increased intravascular volume, pregnant patients can lose a significant amount of blood before tachycardia, hypotension, and other signs of hypovolemia occur. Thus, the fetus may be in distress and the placenta deprived of vital perfusion while the mother’s condition and vital signs appear stable. Administer crystalloid fluid resuscitation and early type-specific blood to support the physiological hypervolaemia of pregnancy. Vasopressors should be an absolute last resort in restoring maternal blood pressure because these agents further reduce uterine blood flow, resulting in fetal hypoxia.
- Baseline laboratory evaluation in the trauma patient should include a fibrinogen level, as this may double in late pregnancy; a normal fibrinogen level may indicate early disseminated intravascular coagulation.
- Perform any indicated radiographic studies because the benefits certainly outweigh the potential risk to the fetus.
- Fetus
- Abdominal examination during pregnancy is critically important in rapidly identifying serious maternal injuries and evaluating fetal well-being. The main cause of fetal death is maternal shock and maternal death. The second most common cause of fetal death is placental abruption.
- Placental abruption
- Placental abruption is suggested by vaginal bleeding (70% of cases), uterine tenderness, frequent uterine contractions, uterine tetany, and uterine irritability. In 30% of abruptions following trauma, vaginal bleeding may not occur. Uterine ultrasonography may be helpful in the diagnosis, but it is not definitive. CT scan may also demonstrate placental abruption. Late in pregnancy, abruption may occur following relatively minor injuries.
- Uterine rupture
- Uterine rupture, a rare injury, is suggested by findings of abdominal tenderness, guarding, rigidity, or rebound tenderness, especially if there is profound shock. Frequently, peritoneal signs are difficult to appreciate in advanced gestation because of expansion and attenuation of the abdominal wall musculature. Other abnormal findings suggestive of uterine rupture include abdominal fetal lie (e.g. oblique or transverse lie), easy palpation of fetal parts because of their extrauterine location, and inability to readily palpate the uterine fundus when there is fundal rupture. X-ray evidence of rupture includes extended fetal extremities, abnormal fetal position, and free intraperitoneal air. Operative exploration may be necessary to diagnose uterine rupture.
- Fetal heart rate monitoring
- Fetal distress can occur at any time and without warning. Fetal heart rate is a sensitive indicator of both maternal blood volume status and fetal well-being. Fetal heart tones should be monitored in every injured pregnant woman.
- Initial fetal heart tones can be auscultated with Doppler ultrasound by 10 weeks of gestation. The normal range for fetal heart rate is 120 to 160 beats per minute. An abnormal fetal heart rate, repetitive decelerations, absence of accelerations or beat-to-beat variability, and frequent uterine activity can be signs of impending maternal and/or fetal decompensation (e.g. hypoxia and/or acidosis) and should prompt immediate obstetrical consultation.
- Perform continuous fetal monitoring with a tocodynamometer beyond 20 to 24 weeks of gestation. Patients with no risk factors for fetal loss should have continuous monitoring for 6 hours, whereas patients with risk factors for fetal loss or placental abruption should be monitored for 24 hours. The risk factors are maternal heart rate > 110, an Injury Severity Score (ISS) > 9, evidence of placental abruption, fetal heart rate > 160 or < 120, ejection during a motor vehicle crash, and motorcycle or pedestrian collisions.
Secondary survey
- During the maternal secondary survey, follow the same pattern as for nonpregnant patients.
- Indications for abdominal computed tomography, focused assessment with sonography for trauma (FAST), and diagnostic peritoneal lavage (DPL) are also the same. However, if DPL is performed, place the catheter above the umbilicus using the open technique.
- Be alert to the presence of uterine contractions, which suggest early labor, and tetanic contractions, which suggest placental abruption.
- Evaluation of the perineum includes a formal pelvic examination, ideally performed by a clinician skilled in obstetrical care. The presence of amniotic fluid in the vagina, evidenced by a pH of greater than 4.5, suggests ruptured chorioamniotic membranes. Note the cervical effacement and dilation, fetal presentation, and relationship of the fetal presenting part to the ischial spines.
- Because vaginal bleeding in the third trimester may indicate disruption of the placenta and impending death of the fetus, a vaginal examination is vital. However, repeated vaginal examinations should be avoided.
- The decision regarding an emergency cesarean section should be made in consultation with an obstetrician.
- CT scans can be used for pregnant trauma patients if there is significant concern for intra-abdominal injury. An abdomen/pelvis CT scan radiation dose approaches 25 mGy, and fetal radiation doses less than 50 mGy are not associated with fetal anomalies or higher risk for fetal loss.
- Admission to the hospital is mandatory for pregnant patients with vaginal bleeding, uterine irritability, abdominal tenderness, pain or cramping, evidence of hypovolaemia, changes in or absence of fetal heart tones, and/or leakage of amniotic fluid. Care should be provided at a facility with appropriate fetal and maternal monitoring and treatment capabilities. The fetus may be in jeopardy, even with apparently minor maternal injury.
Definitive care
- Obtain obstetrical consultation whenever specific uterine problems exist or are suspected. With extensive placental separation or amniotic fluid embolisation, widespread intravascular clotting may develop, causing depletion of fibrinogen, other clotting factors, and platelets. This consumptive coagulopathy can emerge rapidly. In the presence of life-threatening amniotic fluid embolism and/or disseminated intravascular coagulation, immediately perform uterine evacuation and replace platelets, fibrinogen, and other clotting factors, if necessary.
- As little as 0.01 mL of Rh-positive blood will sensitise 70% of Rh-negative patients. Although a positive Kleihauer-Betke test (a maternal blood smear allowing detection of fetal RBCs in the maternal circulation) indicates fetomaternal hemorrhage, a negative test does not exclude minor degrees of fetomaternal haemorrhage that are capable of isoimmunising the Rh-negative mother. All pregnant Rh-negative trauma patients should receive Rh immunoglobulin therapy unless the injury is remote from the uterus (e.g. isolated distal extremity injury). Immunoglobulin therapy should be instituted within 72 hours of injury.
Intimate partner violence
Intimate partner violence is a major cause of injury to women during cohabitation, marriage, and pregnancy, regardless of ethnic background, cultural influences, or socioeconomic status.
Indicators that suggest the presence of intimate partner violence include:
- Injuries inconsistent with the stated history
- Diminished self-image, depression, and/or suicide attempts
- Self-abuse and/or self-blame for injuries
- Frequent ED or doctor’s office visits
- Symptoms suggestive of substance abuse
- Isolated injuries to the gravid abdomen
- Partner insists on being present for interview and examination and monopolises discussion
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
