Cardiovascular system:
Plasma volume increases by 50 % which leads to dilutional anemia and reduced oxygen-carrying capacity. Signs of hemorrhagic shock appear late.
Heart rate is increased by 15–20 beats and cardiac output by 40 % due to the pressure of gravid uterus on IVC. These lead to increase in CPR demands.
Uterine blood flow is about 10 % of the cardiac output at term so there is high chance of massive hemorrhage in uterine injuries.
Systemic vascular resistance and arterial blood pressure decrease.
Coagulation cascade is in activated state; hence, tendency for thrombosis is increased.
Decreased venous return due to the pressure of gravid uterus leads to increased CPR demands.
Respiratory system:
Respiratory rate is increased leading to a state of physiologic hyperventilation.
Oxygen consumption increases by 20 %, so hypoxia develops more quickly.
Hyperventilation, decreased residual capacity, and arterial pCo2 decrease the buffering capacity, so acidosis is more likely.
Mucosal congestion and laryngeal edema lead to difficult airway.
Other changes:
Decreased gastric motility and relaxed lower esophageal sphincter lead to the risk of aspiration.
Enlarged uterus causes reduced venous return, supine hypotension, and difficulty in respiration.
Increased weight during pregnancy leads to difficult airway management.
Hypertrophied pelvic vasculature predisposes for massive retroperitoneal hemorrhage.
Bowel and bladder are more susceptible for injury due to the upward displacement by uterus.
Placenta: lack of elasticity of placenta predisposes it to abruptio placenta leading to release of placental thromboplastin or plasminogen activator from the myometrium.
Musculoskeletal: pelvic ligament laxity, protruding abdomen, and change in the center of gravity lead to pelvic widening, lordosis, gait instability, and tendency of fall.
Types of Trauma in Pregnancy
1.
Blunt trauma
Automobile accidents
Physical abuse
Sexual assault
Falls
Aggravated assaults
2.
Penetrating trauma
Knife wound
Gunshot wound
3.
Burn injury
Blunt Injury
Besides motor vehicle accidents, assaults, abuse, and falls are frequent causes of serious blunt trauma in pregnancy.
The main concerns are immediate assessment of maternal effects of trauma, emergency treatment, and evaluation of collateral effects on fetus.
Problems in blunt abdominal trauma:
1.
The enlarged uterus loses the protection of the bony pelvis.
2.
Increased chances of retroperitoneal hemorrhage as the pelvic vessels are engorged.
Amniotic fluid provides some protection to fetus by absorbing the thrust of trauma, dissipating the force of the blow by transmitting it equally in all directions.
Risks to the Mother
Maternal mortality from blunt trauma is estimated to be about 7 % [2]. It includes placental abruption, preterm labor, massive fetomaternal hemorrhage, uterine rupture and fetal loss, amniotic fluid embolism, and DIC. Splenic hemorrhage is the most common cause of intraperitoneal hemorrhage followed by uterine rupture. Retroperitoneal hemorrhage may occur secondary to rupture of the pelvic venous plexus.
Risks to the Fetus
Factors Associated with Increased Fetal Mortality after Trauma
1.
Maternal hypotension
2.
High maternal Injury Severity Score
3.
Ejection from a motor vehicle
4.
Maternal pelvic fracture
5.
Automobile versus pedestrian accidents
6.
Maternal history of alcohol use
7.
Young maternal age
8.
Motorcycle crashes
Assessment of a Pregnant Patient with Blunt Trauma
All pregnant women should be evaluated in a medical setting. The assessment and management of a case of blunt abdominal trauma depends upon the gestational age, degree of maternal injury, and mechanism of injury.
The physical examination may be unreliable and difficult due to the displacement of abdominal content by gravid uterus and stretching of peritoneum, diminishing the response to peritoneal irritation.
Penetrating Trauma
With the progress of pregnancy, there are changes in intra-abdominal organs in position with important implications. Penetrating injury to the upper part of the abdomen is more likely to be associated with multiple gastrointestinal injuries due to upward pushing of bowel by enlarged uterus. Organs involved are small bowel, liver, colon, and stomach in decreasing frequency. Injuries to the lower quadrants of the abdomen during the third trimester almost exclusively involve the uterus which may be advantageous to the mother due to the protective effect of the uterus and amniotic fluid resulting in less destruction to other organs. It is rare for a projectile to clear the posterior wall of the uterus so the maternal viscera are often spared. If the uterus is involved in penetrating trauma, fetal injury may occur in 70 % [3] of cases. Gunshot wounds to the uterus carry a maternal mortality of 7–9 % [2]. In case of injury before 37 weeks, fetal mortality is higher [2].
In cases of trauma in the upper abdomen, surgical exploration is generally recommended. In trauma involving lower abdomen, a more conservative approach, including observation, wound exploration, and laparoscopy, remains an option if maternal and fetal status is reassuring [4].
Stab wounds which do not appear to penetrate beyond the abdominal wall have been managed nonoperatively, whereas laparotomy is usually indicated with evidence of peritoneal penetration, particularly if intraperitoneal hemorrhage or bowel perforation is suspected.
Severity of Injuries
All patients with major injuries require hospitalization where surgical and obstetric facilities are available due to high rate of mortality. Even minor injuries are associated with complications as fetomaternal hemorrhage, so it needs careful attention.
Classification of Major Trauma in Pregnancy
Table 1 shows criteria for major trauma in pregnancy. If any one criterion (except systolic BP*) is present from any category (vital signs, injury pattern, or mechanism of injury), trauma is considered “major.”
Vital signs criteria
Conscious state | Altered level of consciousness |
Respiratory rate | <10 or >30 breaths/min |
SpO2 (room air) | <95 % |
Heart rate | >120 bpm |
aSystolic BP | <90 mmHg |
Injury pattern criteria
Penetrating or blast injury to the head, neck, chest, abdomen, pelvis, axilla, or groin |
Significant blunt injury to a single region of head, neck, chest, abdomen, pelvis, or axilla |
Injury to any two or more body regions of the head, neck, chest, abdomen, pelvis, or axilla |
Limb amputation above the wrist or ankle |
Suspected spinal cord injuries |
Burns >20 % or other complicated burn injury to the hand, face, genitals, and airway and respiratory tract |
Serious crush injury |
Major compound fracture or open dislocation with vascular compromise |
Fractured pelvis |
Fractures involving two or more of the following: femur, tibia, humerus |
Mechanism of injury criteria
Ejected from vehicle |
Fall from height >3 m |
Involved in an explosion |
Involved in a high impact motor vehicle crash with incursion into the occupants compartment |
Involved in a vehicle rollover |
Involved in a road traffic collision in which there was a fatality in the same vehicle |
Entrapped for >30 min |
Pedestrian impact |
Motorcyclist impact >30 kph |
Minor Trauma
Any trauma injury that does not meet the criteria for defining major trauma.
Traumatic Complications in Pregnancy
Vaginal bleeding.
Preterm rupture of membranes.
Placental abruption.
Maternal pelvic fractures.
Fetal death.
Fetal fractures, especially skull, clavicles, and long bones.
Intracranial hemorrhage.
Indirect injury is generally due to fetal hypoxia secondary to maternal hypotension, fetal hemorrhage, placental abruption, cord injury, uterine injury, or other injury.
Other: spontaneous abortion, preterm delivery, and Rh isoimmunization.
Uterine Contractions and Preterm Labor
The most common obstetric problem during trauma is uterine contractions. Myometrial and decidual cells, damaged by contusion or placental separation, release prostaglandins that stimulate uterine contractions. Progression to labor depends upon the size of uterine damage, the amount of prostaglandins released, and the gestational age of the pregnancy. Occasional uterine contractions, the most common finding after trauma in pregnant women, are not associated with adverse fetal outcomes and resolve within a few hours in 90 % of cases.
The occurrence of eight or more uterine contractions per hour for more than four hours is associated with placental abruption. Uterine contractions, which occur in 39 % [8] of pregnant trauma patients, may progress into preterm labor.
Risk factors, outside of trauma, associated with preterm labor include cardiovascular disease, hypertension, preeclampsia, eclampsia, diabetes, smoking, placenta previa, abruptio placenta, infection, and physical abnormalities. The diagnosis of preterm labor is made by the presence of 3 contractions in 20 min plus cervical change or a cervix that is 2 cm dilated and less than 1 cm in length which can be done by serial cervical examinations [8].
Spontaneous Abortion
Traumatic injuries may result in spontaneous abortion before the 20th week of gestation. The most common signs and symptoms include abdominal pain or cramping and vaginal bleeding.
Placental Abruption
Placental abruption results as the inelastic placenta shears away from the elastic uterus during sudden deformation of the uterus. It is one of the most common injuries, usually associated with blunt trauma, and accounts for 50–70 % of fetal losses [8]. Incidence of abruption increased with the severity of injury, from 8.5 % in non-injured pregnant women involved in car accidents to 13 % in women with severe injuries [6]. Maternal mortality from abruption is less than 1 %, but fetal death ranges from 20 to 35 %.
Diagnosis is based on the presence of abdominal pain, vaginal bleeding, uterine tenderness, amniotic fluid leakage, maternal hypovolemia, a uterus larger than normal for the gestational age, or a change in the fetal heart rate, but it can also be present in asymptomatic mothers.
Ultrasound is also not sensitive enough to rule out abruption, necessitating the use of routine posttraumatic fetal cardiotocographic monitoring.
Uterine Rupture
The risk of uterine rupture is 1 % in pregnant trauma patients (Schwaitzberg 2014). The most common cause of uterine rupture is severe blunt trauma to the abdomen, from a vehicular crash when the pelvis strikes the uterus, leading to rupture. Some uterine rupture also involves penetrating trauma.
Such an injury may result in serosal hemorrhage or abrasions; avulsion of the uterine vasculature with hemorrhage; complete disruption of the myometrial wall with extrusion of the fetus, placenta, or umbilical cord into the abdominal cavity; or complete uterine avulsion.
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