Master Class

Be Prepared to Manage Severely Injured Pregnant Women


 

Patients are bearing children at older ages and are more active than the obstetric populations of generations ago. They are in the workplace, out on the roads, and exposed to common causes of trauma, such as motor vehicle accidents and falls.

It is helpful to know the numbers and be aware of the significance of the problem. Trauma in pregnancy is significantly more frequent, for instance, than the genetic problems we encounter and screen for in our practices.

As ob.gyns., we are bound to be called to treat trauma in pregnancy at some point, and it is important that we be prepared to optimally manage the seriously injured pregnant woman as either a primary manager or as an advisor or consultant, whatever the situation and phase of evaluation and treatment demand.

The Causes

The vast majority of women who experience trauma (95%–96%) suffer injuries from blunt, rather than penetrating, types of trauma. Most of these injuries, in turn, are a result of motor vehicle accidents.

Motor vehicle accidents are the leading cause of death in women aged 12-51 years and the leading cause of trauma in women of childbearing age, accounting for well over half of the major injuries experienced by pregnant women.

Falls are the second most common cause of blunt trauma.

Although relatively infrequent, penetrating trauma—often caused by gunshot wounds—is still a reality. Penetrating trauma leads to significant injury to the fetus more often than to the mother, because the mother's abdominal organs are shielded by the gravid uterus.

As ob.gyns., we can help our patients decrease injury in motor vehicle accidents by urging them to use seat belts. When worn correctly—with the lap belt fitting under the belly and close to the hips, and the shoulder belt resting between the breasts and over the shoulder—seat belts with shoulder restraints can definitively reduce the risk of death and injury for both the mother and fetus.

It is also important to remember that domestic or interpersonal violence may be more frequent during pregnancy than at other times. Such abuse is a less evident cause of blunt trauma, but a very real one. The incidence of interpersonal violence can be as high as 14%–20% in pregnant teenagers, and probably averages about 10%–11% in pregnant women overall.

When taking care of women who report injuries from falls and other events that do not correlate with the overall history or physical exam, we must—in a private and safe environment—address the possibility of partner abuse. We should also remind ourselves that women who are physically abused have a higher incidence of infection, low maternal weight gain, maternal alcohol and drug abuse, and low-birth-weight babies.

Physiologic Changes

Ob.gyns. will sometimes serve as consultants or advisors in managing trauma during pregnancy, and at other times will serve as primary managers. In any case, optimal evaluation and management require both teamwork (an integrated effort of multiple specialties) and a central role for the ob.gyn., whose understanding of the physiologic changes of pregnancy is vital to management decisions.

Key changes that occur secondary to pregnancy most often alter the patient's cardiovascular, hematologic, respiratory, urinary, gastrointestinal, and endocrine systems.

Cardiac output increases during pregnancy by 1-1.5 L/min, with a dramatic increase in the percentage of cardiac output that goes to the uterus. By week 36, the uterus receives up to 600 mL/min of blood—which represents about a tenth of the mother's cardiac output—compared with 60 mL/min in the nonpregnant state. Consequently, trauma to the uterus can result in significant hemorrhage and shock.

Blood volume increases by 45%–50% during pregnancy, and can be instrumental in concealing signs of shock from hypovolemia. Along with this, however, the amount of all clotting factors also increases, which predisposes the pregnant patient to embolic risks as well as coagulopathy from disseminated intravascular coagulation (DIC).

The respiratory system adapts for its role of oxygen delivery to the fetus. Tidal volume increases, with an overall increase in minute ventilation. Changes that result from this adaptation are a lowering of the maternal CO2 level and a decrease in alveolar residual volume. This can further result in a respiratory alkalotic state, which is corrected with a renal decrease in bicarbonate (a compensated respiratory alkalosis). The decreased residual volumes render the pregnant patient more susceptible to alveolar collapse and respiratory compromise.

Under these circumstances, it may be prudent to consider early intubation of the pregnant patient with respiratory compromise in order to preserve the exchange of gases across the fetoplacental unit.

Renal blood flow is increased in pregnancy, with a concomitant increase in creatinine clearance and a tendency to more rapidly clear drugs that are renal dependent.

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