Due to the risk of fetal hypoxia, early airway management is highly recommended in caring for the pregnant trauma patient, especially if the patient is obtunded or displaying signs of respiratory compromise [25]. The emergency physician should have a low threshold for intubation and mechanical ventilation and anticipate a difficult airway [30].

Intubation failure rate has been reported to be higher in pregnant patients due to the various anatomical and physiological changes that occur in pregnancy. Diaphragmatic elevation decreases forced vital capacity. The relative hypocapnia of pregnancy, together with a baseline decrease in functional residual capacity and residual volume, results in decreased oxygen reserves. There is a propensity toward faster desaturation during rapid sequence intubation (RSI); therefore preoxygenation is vital [31–35]. Normal pregnancy causes fluid retention and weight gain resulting in mucosal edema and therefore narrower airways. This also increases airway resistance and decreases overall respiratory system compliance. Endotracheal tubes with diameters 0.5–1.0 mm smaller than standard tube sizes should be used on the first attempt, with smaller tubes prepared as backup [36]. In addition, there is increased aspiration risk during intubation for the pregnant trauma patient due to the ascending and enlarging uterus which places increased pressure on intestinal and stomach contents; at the same time progesterone-mediated smooth muscle relaxation reduces the tone of the lower esophageal sphincter [37, 38]. A low threshold for the placement of a nasogastric tube for gastric decompression prior to RSI is recommended.

The majority of RSI medications, including paralytics, analgesics, anesthetics, or sedatives, are category C under the FDA pregnancy pharmacology safety guidelines (Table 11.1). Exceptions include ketamine, which is category B, and benzodiazepines that are category D (Table 11.2). There are no current recommendations or guidelines to suggest the use of one medication over another or dose adjustments for RSI in the pregnant patient [31–33].

If mechanical ventilation is initiated, minute ventilation should be managed to maintain PaCO₂ levels around 30–32 mm Hg, as hypocapnia is physiologic in late pregnancy. A PaCO₂ >32 mmHg in a pregnant patient suggests respiratory insufficiency and a level >40 mmHg, respiratory failure [30]. Fetal survival is entirely dependent upon uterine perfusion and oxygen delivery.

Avoidance of an acidotic state is essential as it is thought to result in uterine vasoconstriction [34].

Targets of SaO2 > 95% and PaO2 > 70 mm Hg ensure fetal oxygen delivery; PaO2 < 60 mmHg has been associated with compromise of fetal oxygenation [28, 35, 37, 39]. In the event of a pneumo−/hemothorax, the chest tube should be placed 1–2 interspaces higher due to diaphragmatic elevation in order to avoid entering the abdomen [25].

Plasma blood volume steadily increases throughout pregnancy; therefore a pregnant patient may lose up to 2 L of blood before showing any signs of circulatory instability [25]. Cardiac output is also increased and can result in rapid hemorrhage. Serum HCO3 < 19 may be an early indication of circulatory compromise.

In the event of hemorrhage, the fetus is at risk for reduced blood supply because maternal circulation preferentially shunts blood away from the uterus. Furthermore, uterine compression of abdominal and pelvic vasculature after 20-week gestation can result in decreased venous return and resultant “supine hypotensive syndrome.” Patients should be placed in the left lateral decubitus position when possible or the uterus should be manually displaced to the left of the midline [26, 40, 41]. Angulations of the patient on the backboard to achieve a slight left lateral decubitus position of 15° to 30° or right lateral decubitus positioning are acceptable alternatives [30, 40]. Intravenous (IV) access, whether central or peripheral, should be established above the level of the diaphragm due to possible uterine compression of abdominal and pelvic vasculature [30].

When treating a pregnant trauma patient, the clinician should avoid the pitfall of attributing hypotension to supine hypotensive syndrome and should ensure that the patient is not hemorrhaging. Recommendations on resuscitative blood pressure goals are extrapolated from perioperative cesarean section patients. The American Heart Association (AHA) recommends a goal for systolic blood pressure (SBP) of >100 mm Hg or greater than 80% of the patient’s baseline blood pressure [42]. Alternatively, the mean arterial pressure (MAP) can be targeted to a value of >65 mmHg as extrapolated from studies in nonpregnant patients. In order to maintain uterine perfusion, hypotension should be aggressively managed. Urinary output is the most sensitive prognosticator of maternal cardiovascular collapse [43]. It is recommended that early requisition and utilization of blood products, specifically CMV antibody-negative or leukocyte-reduced, Rh-negative products, must be transfused in a 2:1:1 (red blood cell/plasma/platelets) ratio given the relative hemodilution in pregnant women [44]. Vasopressors may reduce uterine flow and therefore placental perfusion, but the benefits of correcting maternal hemodynamics are of primary concern. The preferential use of phenylephrine has increased in popularity due to recent studies demonstrating less hypotension and improved fetal acid-base status compared to the once previously utilized ephedrine [45].