1. Plasma volume will increase 40–50%, but erythrocyte volume will only increase by 20% resulting in a dilutional anemia.
   
2. Heart rate will decrease due to dextrorotation of the heart resulting in a functional outflow obstruction.
   
3. Supine blood pressure will be increased due to increased venous return as a result of increased plasma volume and aortocaval compression.
   
4. Respiratory rate will be decreased due to a decrease in minute ventilation and as a compensation for physiologic metabolic alkalosis.
   
5. Functional residual capacity will increase more than 25% preventing atelectasis that may result from the gravid uterus.

Physiologic changes of pregnancy are extensive and can be observed in many of the organ systems. The altered physiology results from various hormonal and anatomic alterations that affect the woman body during pregnancy. Clinicians in an ICU setting must be aware of such alterations as these physiologic changes of pregnancy can have a significant impact on resuscitative efforts. Plasma volume will increase by 40–50%, but erythrocyte volume by only 20% resulting in a dilutional anemia leading to a decreased oxygen carrying capacity; therefore, answer A is correct. As a result, heart rate will increase by 15–20 beats per minute and cardiac output will increase by 40%, which can result in increased CPR circulation demands (Answer B). An increase in dextrorotation of the heart may occur and will be noted with increased EKG left axis deviation. Blood pressure and venous return will be decreased in the supine position as a result of aortocaval compression, which will result in a decreased cardiac output by up to 30% (Choice C). As such, care should be taken in positioning with left uterine displacement. Minute ventilation will be increased noted by an increased respiratory rate (progesterone‐mediated), as well as an increased tidal volume (progesterone‐mediated) resulting from an increased oxygen demand and increased oxygen consumption by up to 20% (Choice D). These changes may affect resuscitative efforts as a result of a baseline compensated respiratory alkalosis (decreased arterial PCO₂ and decreased serum bicarbonate) with a decreased buffering capacity and a rapid decrease of PaO₂ in hypoxia. Anatomic changes will additionally result in a decreased functional residual capacity by 25%, thus decreasing ventilatory capacity (Choice E). Resuscitative efforts may be aided by electronic fetal heart rate monitoring. Electronic fetal heart rate monitoring reflects uteroplacental perfusion and fetal acid‐base status; therefore, changes in fetal heart rate monitoring (changes in baseline variability or new decelerations) should prompt reassessment of maternal blood pressure, oxygenation, ventilation, acid–base balance, or cardiac output.

Answer: A

American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins‐ Obstetrics. ACOG Practice Bulletin No. 211: Critical care in pregnancy. Obstetrics and Gynecology 2019 May; 133(5):e303–e319.

1. pH in the third trimester will be altered by anatomical effect of the gravid uterus reflecting a decreased minute ventilation and therefore a respiratory acidosis.
   
2. PaCO₂ cannot be used as a marker of increased work of breathing in the obstetric patient as it will not change due to required compensation of a baseline metabolic acidosis.
   
3. PaCO₂ of 40 mm Hg is concerning for progressive respiratory failure in this patient.
   
4. PaO₂ is irrelevant in the pregnant patient and is expected to decrease explained by a decrease in the minute ventilation associated with the third trimester of pregnancy.
   
5. Serum bicarbonate levels will be increased on laboratory evaluation in the third trimester of pregnancy due to increased buffering required to compensate for the respiratory acidosis associated with the decreased minute ventilation.

Respiratory insufficiency can naturally occur in the critically ill obstetric patient, and vigilance is warranted as pulmonary symptoms can rapidly progress to respiratory failure. Minute ventilation in pregnancy is increased reflected by an increased respiratory rate (progesterone‐mediated), as well as an increased tidal volume (progesterone‐mediated). This results from an increased oxygen demand and increased oxygen consumption due to the fetus, which may be increased by 20%. PaO₂ will not vary significant from the nonpregnant state through the third trimester, and most of the changes are due to increased minute ventilation. The obstetric patient will demonstrate a baseline‐compensated respiratory alkalosis (decreased arterial PCO₂ and decreased serum bicarbonate) on ABG interpretation. Anatomic changes will additionally result in a decreased functional residual capacity by 25%, thus decreasing ventilatory capacity. The pH is normal, and there is a compensated respiratory alkalosis and not acidosis. An increasing PaCO₂ implies that the work of breathing is increasing and a PaCO₂ of 40 mm Hg in a pregnant patient, although normal in the nonpregnant state, is concerning for progressive respiratory failure (Choice B). The PaO₂ is normal or higher than in the nonpregnant state. Typically, the serum bicarbonate will be decreased due to compensated respiratory alkalosis and not increased (Choice E).

Answer: C

Hegewald MJ, Crapo RO . Respiratory physiology in pregnancy. Clinics in Chest Medicine 2011; 32:1–13.

Mighty HE . Acute resp failure pregnancy. Clinical Obstetrics and Gynecology 2010; 53(2):360–368.

1. The most common admission diagnosis requiring ICU care for the obstetric patient is multisystem organ failure resulting from sepsis.
   
2. Recently, maternal mortality rates in the United States have been reported to be rising while maternal morbidity is decreasing, thus ICU evaluation postpartum is recommended.
   
3. Postpartum hemorrhage and preeclampsia‐related complications are the most common reasons for ICU admission in the obstetric patient.
   
4. Hemorrhage postpartum is a rare event as physiologic changes in pregnancy include a decrease in total blood volume and a decreased cardiac output due to increased uterine perfusion requirements.
   
5. Obstetric patient ICU admission is common and is reported at over 25/1,000 deliveries.

Sepsis and multisystem organ failure are not the most common diagnoses for ICU admission as it is only approximately 5% of obstetric‐related ICU admissions (Choice A). The most common reasons for an obstetric patient to require admission to an ICU are preeclampsia‐related complications and postpartum hemorrhage. The percentage of ICU admissions in the obstetric patient has been reported at 21.5% for postpartum hemorrhage and 32.5% for maternal hypertension. Complications related to preeclampsia include eclampsia, intracerebral hemorrhage, pulmonary edema, renal insufficiency, liver injury, and placental abruption (Choice C).Global maternal mortality rates are reported to be decreasing, but maternal morbidity has been reported to be increasing currently at 2.5% of hospital deliveries in the United States (Choice B). Pregnancy results in multiple physiologic changes including an increase in total blood volume, cardiac output and uterine blood flow, hemorrhage may result from placenta previa, placental abruption, uterine atony, and secondary coagulopathies (Choice D). Additional reasons obstetric patients may require ICU admission are related to obstetric sepsis, obstetric heart disease, and complications related to anesthesia. Obstetric patient admission to an ICU has been reported in approximately 2–4/1000 deliveries in developed countries (Choice E).

Answer: C

Einav S, Leone M. Epidemiology of obstetric critical illness. International Journal of Obstetric Anesthesia 2019 Nov; 40:128–139.

Intensive Care National Audit and Research Centre. Female admissions (aged 16–50 years) to adult, general critical care units in England, Wales and Northern Ireland reported as “currently pregnant” or “recently pregnant”. London (UK): ICNARC; 2013.

Pollock W, Rose L, Dennis CL . Pregnant and postpartum admissions to the intensive care unit: a systematic review. Intensive Care Medicine 2010; 36:1465–1474.

Zeeman GG . Obstetric critical care: a blueprint for improved outcomes. Critical Care Medicine 2006 Sep; 34(9 Suppl):S208–S214.

1. Lifesaving medical interventions in a critically ill obstetric patient must be reviewed by the obstetrics team to avoid teratogenic complications.
   
2. Care of the critically ill obstetric patient in the ICU involves the care of two patients (mother and fetus) simultaneously with no priority in optimization.
   
3. Diagnostic imaging in the obstetric ICU patient is contraindicated due to teratogenic effects to the fetus.
   
4. Clinical status of the fetus has the highest priority in the management of the critically ill obstetric patient.
   
5. When caring for obstetric ICU patients, the mother is the primary priority as fetal status is predicted on optimization of the maternal condition.

Management principles of obstetric patients admitted to the ICU follow similar principles as compared to nonpregnant patients. Therefore, many patient care decisions might be impacted by the patient’s status (antepartum vs postpartum) and should therefore be made in a multidisciplinary fashion collaboratively between the critical care, obstetrics/gynecology, and neonatology teams. However, all critical care intensivists should be aware of the basic management of teratogenic complications and reliance of others (Choice A). While it has been generally accepted that care of the obstetric patient in the ICU involves the care of two patients (mother and fetus) simultaneously, the principle follows that the woman’s interest is paramount, and fetal status is predicted on optimization of the maternal condition (Choice C). Maternal stabilization is therefore the first priority when taking care of an obstetric ICU patient (Choices B and D). Medical interventions and diagnostic imaging may be modified to an extent but should not be withheld due to fetal concern (Choice C). Imaging will depend on the study but is not always contraindicated if needed to treat the mother.

Answer: E

American College of Obstetricians and Gynecologists’ Committee on PracticeBulletins—Obstetrics. ACOG Practice Bulletin No. 211: critical care in pregnancy. Obstetrics and Gynecology 2019 May; 133(5):e303–e319.

Guidelines for diagnostic imaging during pregnancy and lactation. Committee Opinion No. 723. American College of Obstetricians and Gynecologists [published erratum appears in Obstet Gynecol 2018;132:786]. Obstetrics and Gynecology 2017; 130:e210–e2106.

1. Based on the patient’s symptoms and lack of documented organ failure, ICU admission is not required.
   
2. The patient should not be admitted to an ICU setting as the physiological criteria used to diagnose sepsis in the nonpregnant population often overlap in normal pregnant women.
   
3. Pregnancy has been associated with immunologic changes resulting in an increased protection and immunity to infection, and therefore ICU care is not warranted in the obstetric patient with signs of infection.
   
4. Clinical parameters that should prompt ICU evaluation in pregnant women include heart rate > 120 bpm, oxygen saturation <95%, and maternal agitation.
   
5. Pre‐existing medical problems such as chronic liver disease, obesity, and congestive heart failure have no association with increased risk for sepsis during pregnancy.

Maternal ICU admission has been classified to result from etiologies directly related to pregnancy (obstetric hemorrhage, hypertensive disease of pregnancy, puerperal sepsis, thrombo‐embolic phenomena, fatty liver), those indirectly related to pregnancy (pre‐existing disease exacerbation) and those coincidental to pregnancy (trauma, non‐puerperal sepsis). It has been reported that sepsis is responsible for approximately 5% of obstetric‐related ICU admissions. The most common cause for ICU involves complications related to preeclampsia (32.5%), and the second most common cause for ICU admission is related to postpartum hemorrhage (21.5%). While the symptoms the patient is presenting with may be the result of infection and may not meet traditional ICU admission criteria as there is no evidence of organ failure and/or the requirement for a life‐saving intervention, clinical deterioration in an obstetric patient may be masked by multiple physiologic changes that occur normally in pregnancy. Additionally, the physiological criteria conventionally used to diagnose sepsis in the nonpregnant population often overlap both in normal pregnant women and in those with sepsis/infection. In response, the National Partnership for Maternal Safety developed a list of clinical parameters termed “maternal early warning criteria” that should prompt ICU evaluation.

These include systolic BP (mm Hg) < 90 or > 160, diastolic BP (mm Hg) > 100, heart rate (beats per minute) < 50 or > 120, respiratory rate (breaths per minute) <10 or >30, Oxygen saturation on room air at sea level <95%, Oliguria (ml/hr) <35 for > or equal to 2 hrs, maternal agitation, confusion or unresponsiveness, patient with preeclampsia reporting non‐remitting headache or shortness of breath (Choices A and B). Additionally, pregnancy has been associated with immunologic changes resulting in an increased susceptibility to infection (Choice C). Pre‐existing medical problems such as chronic liver disease, obesity, and congestive heart failure are associated with increased risk for sepsis during pregnancy (Choice E). Treatment for maternal sepsis follows the same recommendations as for the nonpregnant patient with timely diagnosis, fluid resuscitation, and early antibiotic therapy. Early antibiotic therapy (within the first hour) is recommended to reduce mortality, and each hour of delay is associated with an increase in mortality.

Answer: D

Carcopino X, Raoult D, Bretelle F, Boubli L, Stein AQ . Fever during pregnancy: a cause of poor fetal and maternal outcome. Annals of the New York Academy of Sciences 2009; 1166:79–89.

Einav S, Leone M. Epidemiology of obstetric critical illness. International Journal of Obstetric Anesthesia 2019 Nov; 40:128–139.

Lazariu V, Nguyen T, McNutt LA, Jeffrey J, Kacica M . Severe maternal morbidity: a population‐based study of an expanded measure and associated factors. PLoS One 2017; 12:e0182343.

Mhyre JM, D’Oria R, Hameed AB, Lappen JR, Holley SL, Hunter SK, et al. The maternal early warning criteria: a proposal from the national partnership for maternal safety. Obstetrics and Gynecology 2014; 124:782–786.

Oud L, Watkins P . Evolving trends in the epidemiology, resource utilization, and outcomes of pregnancy‐associated severe sepsis: a population‐based cohort study. Journal of Clinical Medical Research 2015; 7:400–416.

1. Pregnant women are at decreased risk of developing ARDS and needing mechanical ventilation when compared with nonpregnant women.
   
2. ARDS in pregnancy could be from the development of amniotic fluid embolism.
   
3. In contrast to the nonpregnant patient, the lungs of the obstetric patient with ARDS demonstrate increased compliance with a decreased work of breathing yet with an associated hypoxemia.
   
4. The management of ARDS currently involves low‐tidal‐volume ventilation with the priority placed on normalizing arterial blood gases and PaO₂/FiO₂ ratios.
   
5. ARDS in pregnancy is rarely seen and due to increased lung compliance, low tidal volume ventilation strategies are not recommended.

Acute respiratory distress syndrome may result as a response to a variety of insults. It is characterized by diffuse inflammation, increased fluid in the lung (non‐cardiogenic pulmonary edema) due to increased vascular permeability, bilateral lung infiltrates, severe progressive hypoxemia with loss of aerated lung units and increased shunt fraction, and decreased lung compliance. Pregnant women are at increased risk of developing ARDS and needing mechanical ventilation compared with nonpregnant women (Choice A). ARDS in pregnancy is seen most commonly in the setting of sepsis with infections such as influenza and pyelonephritis. It can also be seen as a complication of obstetric diagnoses such as preeclampsia, amniotic fluid embolism, and infections of pregnancy such as chorioamnionitis and endometritis (Choice B). As defined by the ARDS Definition Task Force, the onset of respiratory failure must be within 1 week of a known clinical event with evidence of bilateral opacities on chest imaging and no other identifiable etiology such as cardiac failure or fluid overload. The degree of ARDS severity (mild, moderate, severe) is based on oxygenation as measured by the partial pressure of arterial oxygen to fraction of inspired oxygen (PaO ₂ /FiO ₂ ) ratio of less than 300. It is further subclassified into mild (PaO₂/FiO₂ 200–300), moderate (PaO₂/FiO₂ 100–200), and severe (PaO₂/FiO₂ less than 100). The lungs of the obstetric patient with ARDS demonstrate decreased compliance with an increased work of breathing and hypoxemia (Choice C). Although mechanical ventilation will be required, high concentrations of oxygen and the physical effects of positive pressure ventilation often required can result in damage to the lungs. The management of ARDS currently involves low‐tidal‐volume ventilation limiting inflation pressures rather than trying to normalize arterial blood gases. To reduce iatrogenic ventilator‐associated injuries, hypercapnea and some degree of hypoxia are acceptable (Choice D). All patients with ARDS including pregnant patients should target a lower tidal volume 4–6 mL/kg predicted body weight and maintenance of plateau pressure between 25 and 30 cm H₂O. Although no studies have evaluated the efficacy of low tidal volume strategy in pregnant and postpartum women, similar to the nonpregnant patient (Choice E). Additionally, management concentrates on elucidating the etiology, minimizing ongoing injury and supportive therapy. Maternal mortality may be as high as 35–60%, and most often results from multiple organ dysfunction syndrome.

Answer: B

The Acute Respiratory Distress Syndrome Network (ARDSNet). Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. The New England Journal of Medicine 2000; 342:1301–1308.

Catanzarite V, Willms D, Wong D, Landers C, Cousins L, Schrimmer D . Acute respiratory distress syndrome in pregnancy and the puerperium: causes, courses, and outcomes. Obstetrics and Gynecology 2001; 97:760–764.

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