Care of the Critically Ill Parturient: Easy as ABCDE

Erin Brokl, MSN, RN, ACNP-BC*
University of Pittsburgh Medical Center
Department of Critical Care Medicine
University of Pittsburgh
Pittsburgh, Pennsylvania, USA

Marie R. Baldisseri, MD, FCCM**
University of Pittsburgh Medical Center
Department of Critical Care Medicine
University of Pittsburgh
Pittsburgh, Pennsylvania, USA

Most pregnant patients are young, healthy and have an uneventful peripartum course. Less than 1% of women who deliver become so critically ill that their acuity requires admission to an intensive care unit (ICU).(1-3) The illness may be directly related to pregnancy, or it may be another medical illness that complicates or exacerbates the pregnancy. To educate intensivists and other practitioners who may infrequently care for the critically ill parturient, we have provided a simple mnemonic device highlighting a few of the critical care nuances that apply to the critically ill pregnant woman and her fetus.

A: Airway
The pregnant woman has a difficult airway because of the underlying physiologic changes associated with pregnancy, namely edema of the upper respiratory tract. This is a direct result of increased blood volume, total body water and interstitial fluid as well as hormone-induced mucosal edema and hypervascularity in the nasopharyngeal, oropharyngeal and laryngopharyneal mucosa.(4-6)

Whether endotracheal intubation is elective or emergent, sufficient time should be taken to evaluate the parturient’s airway and then properly position the patient in a sniffing position with neck flexed and head extended at the atlanto-occipital joint. “Ramping” of the upper body may also be required as weight gain and enlarged breasts may contribute to difficult placement of an artificial airway.(4) Because of her extremely high risk for aspiration of gastric contents, assume the parturient has a full stomach and utilize rapid sequence induction with cricoid pressure as the induction method of choice for intubation.(4)

Aspiration can be severe and life threatening in this population, and the risk is increased because of hormone-induced laxity in the lower esophageal sphincter tone and anatomical changes in the position of the gastroesophageal junction and stomach from the growing gravid uterus.(4) Aspiration risk also may be increased by gastric insufflation of air if bag-mask ventilation is prolonged without sufficient cricoid pressure.(4)

Multiple attempts at airway manipulation should be minimized to avoid bleeding and worsening edema of the upper airway, and a smaller than usual endotracheal tube size may be necessary to pass through edematous vocal cords. The American Society of Anesthesiologists’ Difficult Airway Algorithm may be applied to the parturient at any time so as to prevent catastrophic harm to the mother and fetus from hypoxemia.

B: Breathing
As she nears term gestation, the pregnant woman develops a chronic respiratory alkalosis with a secondary, compensatory metabolic acidosis as a result of decreased functional residual capacity (FRC), expiratory reserve volume, residual volume and total lung capacity from upward displacement of the diaphragm by the uterus. These changes are exacerbated when a parturient lies in the supine position where her FRC may fall an additional 25%.(6) In pregnancy, a normal pH may be 7.4 to 7.47; PaCO2 will range from 27 to 34 mm Hg with bicarbonate levels in the 18 to 22 mEq/L range secondary to increased renal bicarbonate excretion.(5-8) Minute ventilation increases by 40% to 50% because of increased tidal volumes, while the respiratory rate remains relatively unchanged from the nonpregnant state.(7) These respiratory system changes are driven by hormonal effects on the brain’s respiratory center, start near the end of the first trimester, and continue until delivery.(5) Because of these physiologic changes, the parturient has decreased pulmonary reserve, thus making respiratory failure the most common critical care issue she faces. A PaCO2 greater than 35 mm Hg in a pregnant patient is indicative of impending respiratory failure. Once mechanical ventilation is initiated, care should be taken to achieve a PaCO2 less than or equal to this value. Permissive hypercapnia may be cautiously utilized in the pregnant woman. Frequent evaluation of maternal PaCO2 and concurrent fetal monitoring are required to assess fetal tolerance of a changing maternal acid-base status.

In addition to her decreased FRC, the parturient has increased oxygen consumption (VO2) of approximately 20%.(6) She and her fetus are more susceptible to hypoxemia, so the fraction of inspired oxygen should be titrated to achieve arterial oxygen saturation of at least 94%. Healthcare providers should have a low threshold for intubation in the setting of maternal hypoxemia, and endotracheal intubation may be favored over noninvasive positive pressure ventilation because of the increased risk of aspiration from hormone-induced gastroesophageal sphincter laxity. To avoid these complications, the parturient should be intubated by the most experienced provider present.

It is important to note that the majority of pregnant women, approximately 70%, will report dyspnea, secondary to decreased FRC and anemia, although they will eventually have a normal peripartum course.(9) If the patient’s dyspnea has an acute onset, she should be evaluated for life-threatening etiologies, including dilated cardiomyopathy, valvular heart disease, venous thromboembolism, pneumonia or exacerbation of underlying pulmonary or cardiac disease.(9)

C: Circulation
A decrease in the systemic vascular resistance is a normal physiologic change associated with pregnancy, so one can expect a very mild decrease in diastolic blood pressure, approximately 5 to 10 mm Hg, in the second trimester.(7,10) Hypotension that is more profound than this is cause for concern given a parturient’s markedly increased total blood volume. Physical examination may also reveal a third heart sound and systolic ejection murmur, both of which can be attributed to the parturient’s increased intravascular volume.(7)

As gestation progresses, cardiac output increases by approximately 30% to 50%.(4,7,10) A gravid uterus compresses the inferior vena cava and aorta and thus decreases a woman’s preload, putting her at risk for syncope, hypotension and bradycardia when she is in the supine position.(5,10-11) These signs and symptoms can be avoided by placing a Cardiff wedge or pillow under her right hip, which displaces the uterus to the left at an angle of 27°, relieving aortocaval compression.(11) This maneuver is particularly important in the event of a cardiac arrest situation. Alternatively, if no Cardiff wedge is available, the patient may remain supine with a rescuer manually displacing the uterus up and leftward while cardiopulmonary resuscitative efforts ensue. A “human wedge” may also be used, whereby a rescuer kneels on the floor, sitting on the soles of his feet with the patient’s back resting on the rescuer’s thighs.(11) Advanced cardiac life support algorithms are the same whether or not the patient is pregnant. Survival for both the pregnant mother and her fetus is dependent on brisk maternal resuscitation, return of spontaneous circulation and adequate systemic tissue oxygenation and delivery. Although cardiac arrest in parturients occurs infrequently, some of the major etiologies of cardiac arrest in this population include massive pulmonary embolism, amniotic fluid embolism, hemorrhage, trauma, preexisting cardiac disease, or primary respiratory arrest.(6,8,11,12)

D: Delivery
Delivery of the fetus may be necessary if the woman is at an advanced stage of her pregnancy and lung compliance or oxygenation is problematic, if she develops cardiac arrest or if severe obstetric complications arise. Uteroplacental flow increases from 2% of cardiac output in a nonpregnant woman to 30% of cardiac output in a pregnant woman.(11) Cardiac output increases by 60% to 80% after spontaneous vaginal delivery and by 30% after cesarean delivery.(11) Each parturient admitted to the ICU should have a predetermined delivery plan that is individualized to her current medical illness. Risk-benefit analysis of emergent cesarean delivery also should be a consideration before clinical deterioration, whether actual or theoretical. If perimortem delivery is indicated to improve maternal hemodynamic status or in the setting of maternal cardiac arrest, it should be rapid and occur within four minutes of onset of arrest of circulation to minimize untoward neonatal neurologic sequelae.(6,8,11,12) Subsequently, delivery and its associated improvement in cardiac output and relief of aortocaval compression may have maternal benefit and allow for a rapid return of maternal spontaneous circulation. Cardiopulmonary resuscitative efforts should continue during the delivery.

E: Early Transfer
If your institution is unable to provide all multiprofessional resources needed to care for a critically ill pregnant woman and possibly her neonate, early and rapid transfer to a tertiary or quaternary care center that specializes in the management of high-risk obstetrics is of the utmost importance. If the critically ill parturient is already in such a facility, early consultation and close collaboration and communication among intensivists, maternal-fetal medicine specialists, anesthesiologists and neonatologists can facilitate achieving optimal health and can minimize complications.(3,8)

Airway, breathing and circulation are the lifeblood of ICU work and patient survival. When it comes to caring for the critically ill pregnant woman, those same principles apply, albeit with a few significant caveats that are worth remembering. Additionally, consider emergent fetal delivery to aid maternal well-being, as well as early transfer to a high-risk obstetrics facility. Although catastrophic maternal complications occur infrequently, appropriate supportive care during critical illness can save two lives.

References:

1.  Mahutte NG, et al. Obstetric admissions to the intensive care unit. Obstet Gynecol. 1999;94:263-266. 

Disclosures:
 
*Author has no disclosures to report

**Author has no disclosures to report