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• Assessment of the adequacy of maternal blood flow requires an understanding that the baseline flow is substantially increased and is further augmented during labor and delivery.

• The increased cardiac output of pregnancy is often diminished, especially in late pregnancy, in the supine position by uterine compression of the vena cava and abdominal aorta. Placing the patient in the left lateral decubitus position is an important management principle in shock.

• The normal hyperventilation of pregnancy results in a respiratory alkalosis with a compensatory metabolic acidosis. The normal arterial blood gas values in pregnancy include a $PO2>100$ mm Hg, a $PCO2$ of 27 to 34 mm Hg, and a serum bicarbonate concentration of 18 to 21 mEq/L.

• Fetal viability depends on adequate oxygen delivery. Maternal cardiac output is the critical determinant of placental blood flow and fetal oxygen delivery. Diminished placental blood flow is particularly dangerous if superimposed on maternal anemia or hypoxemia. Fetal oxygen delivery can be improved by optimizing maternal cardiac function, transfusing blood to increase oxygen carrying capacity, and providing supplemental oxygen.

• In critically ill gravidas, fetal monitoring should be performed when available and in collaboration with obstetrics clinicians. Changes in fetal heart rate can be a sign of inadequate oxygen delivery. In addition to fetal heart rate monitoring, the parameters of oxygen delivery and acid-base status in the mother are generally the best measures of the adequacy of oxygen delivery to the fetus.

• Hemorrhage in pregnancy can be massive and may require extraordinary fluid resuscitation, blood product replacement, and early surgical consultation.

• In pregnancy, sepsis is rare but can be severe. Source control and early surgical evaluation for obstetric infections are essential. Vasoactive drugs may be indicated in refractory hypotension to preserve maternal cardiac output and fetal oxygen delivery.

• Preeclampsia is a multisystem disorder of vascular dysfunction characterized by hypertension and proteinuria. Central nervous system dysfunction, coagulopathy, pulmonary edema, renal dysfunction, and liver function abnormalities may occur. Early recognition and well-timed delivery are crucial.

• When severe or when associated with preeclampsia, treatment of hypertension in pregnancy may require intravenous agents: labetalol and hydralazine are preferable to nitroprusside.

• Cardiopulmonary resuscitation in pregnancy includes consideration, when feasible, of emergent cesarean section in selected patients.

• In evolving respiratory failure, early elective intubation and mechanical ventilation are recommended to gain airway access in a controlled setting and to avoid respiratory crisis.

• The reduced functional residual capacity (FRC) and increased oxygen consumption in pregnancy increase the risk of hypoxemia during intubation or hypoventilation.

• Decisions regarding labor and delivery are important management issues. Cesarean section is a more controlled mode of delivery. However, even with adequate sedation and analgesia, the physiologic stress of surgery may make vaginal delivery a better option in the nonemergent setting and when the mother is capable of labor.

• The increased volume of distribution and glomerular filtration rate may affect dosing of medications in pregnancy.

• Successful management of critical illness in pregnancy requires a ...

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