A 19-year-old G1P0 woman at 20 weeks’ gestation complains of the acute onset of pleuritic chest pain and severe dyspnea. She denies a history of reactive airway disease or cough. She has no history of trauma. On examination, her temperature is 98°F (36.6°C), heart rate (HR) is 120 beats per minute (bpm), blood pressure (BP) is 130/70 mm Hg, and respiratory rate (RR) is 40 breaths per minute. The lung examination reveals clear lungs bilaterally. The heart examination shows tachycardia. The fetal heart tones are in the range of 140 to 150 bpm. The oxygen saturation level is 89%. Supplemental oxygen is given.
» What test would most likely lead to the diagnosis?
» What is your concern?
ANSWERS TO CASE 15:
Pulmonary Embolus in Pregnancy
Summary: A 19-year-old G1P0 woman at 20 weeks’ gestation complains of the acute onset of pleuritic chest pain and severe dyspnea. On examination, her H R is 120 bpm and RR is 40 breaths per minute. The lung examination reveals clear lungs bilaterally. The oxygen saturation is low.
Test most likely to lead to the diagnosis: Spiral computed tomography or ventilation/ perfusion (V/ Q) imaging of the lungs.
Concern: Pulmonary embolism.
ANALYSIS
Objectives
1. Understand that pleuritic chest pain and severe dyspnea are common presenting symptoms of pulmonary embolism.
2. Know that the pregnant woman is predisposed to deep venous thrombosis due to venous obstruction and a hypercoagulable state.
3. Understand that the spiral computed tomography (CT ) or V/ Q imaging scan is an initial diagnostic test for pulmonary embolism.
Considerations
This 19-year-old woman at 20 weeks’ gestation complains of the acute onset of severe dyspnea and pleuritic chest pain. The physical examination confirms respiratory distress due to tachycardia and tachypnea. The lungs are clear on auscultation, and the patient does not complain of cough or fever, which rules out reactive airway disease or significant pneumonia. Clear lungs also speak against pulmonary edema.
The patient has significant hypoxia with oxygen saturation of 89%, which translates to a partial pressure of 58 mm H g (life-threatening). Thus, the most likely diagnosis is pulmonary embolism. Although many diagnostic tests should be considered in the initial evaluation of a patient with respiratory distress (such as arterial blood gas, chest radiograph, electrocardiograph), in this case, a CT pulmonary angiogram (CTPA), also referred to as spiral/ helical CT, or ventilation-perfusion (V/ Q) scan would likely lead to the diagnosis. The D-dimer assay may also be used in nonpregnant patients with a low pretest probability for pulmonary embolism (PE). The test has been shown to have a good negative predictive value, making it useful in ruling out pulmonary embolism if negative. However, since an elevated D-dimer level is normally found in pregnant patients, the assay would have limited value in this case.
If the imaging confirms pulmonary embolism, then the patient should receive anticoagulation to help stabilize the clot and decrease the likelihood of further venous thromboembolism. Pregnancy itself leads to an increased risk for thromboembolism by causing venous stasis and decreased outflow due to the mechanical effect of the uterus on the vena cava; additionally, the high estrogen levels induce a hypercoagulable state due to the increase in clotting factors, particularly fibrinogen.
APPROACH TO:
Respiratory Distress in Pregnancy
DEFINITIONS
DEEP VENOUS THROMBOSIS:Blood clot involving the deep veins of the lower extremity, rather than just the superficial involvement of the saphenous system.
PULMONARY EMBOLUS: Blood clot that is lodged in the pulmonary arterial circulation, usually arising from a thrombus of the lower extremity or pelvis.
HELICAL COMPUTED TOMOGRAPHY PULMONARY ANGIOGRAM:
H igh-resolution imaging using intravenous (IV) contrast with multiple sections to allow for three-dimensional analysis and examination for vascular filling defects in the pulmonary vasculature.
MAGNETIC RESONANCE ANGIOGRAPHY: H igh-resolution magnetic resonance imaging using IV contrast to assess for vascular defects, typically not used in pregnancy due to the gadolinium.
VENTILATION-PERFUSION SCAN IMAGING PROCEDURE: Using a small amount of intravenous, radioactively tagged albumin, such as technetium, in conjunction with a ventilation imaging, with inhaled xenon or technetium, in an effort to find large ventilation-perfusion mismatches suggestive of pulmonary embolism.
DUPLEX ULTRASOUND FLOW STUDY:Ultrasound technique using both realtime sonography and Doppler flow to assess for deep venous thrombosis (DVT).
CLINICAL APPROACH
Respiratory distress is an acute emergency and necessitates rapid assessment and therapy. Oxygen is the most important substrate for the human body, and even 5 or 10 minutes of severe hypoxemia can lead to devastating consequences. H ence, a quick evaluation of the patient’s respiratory condition, including the respiratory rate and effort; use of accessory muscles, such as intercostal and supraclavicular muscles; anxiety; and cyanosis; may indicate mild or severe disease. (See Figure 15– 1 for one algorithm to evaluate dyspnea in pregnancy.) The highest priority is to identify impending respiratory failure, since this condition would require immediate intubation and mechanical ventilation. Pulse oximetry and arterial blood gas studies should be ordered while information is gathered during the history and physical. A cursory and targeted history directed at the pulmonary or cardiac organs, such as a history of reactive airway disease, exposure to anaphylactoid stimuli such as penicillin or bee sting, chest trauma, cardiac valvular disease, chest pain, or palpitations, are important. Meanwhile, the physical examination should be directed at the heart and lung evaluation. The heart should be assessed for cardiomegaly and valvular disorders. The lungs should be auscultated for wheezes, rhonchi, rales, or absent breath sounds. The abdomen, back, and skin should also be examined.
A pulse oximetry reading of <90% corresponds to an oxygen tension of <60 mm Hg. Supplemental oxygen should immediately be given. An arterial blood gas should be obtained to assess for hypoxemia, carbon dioxide retention, and acid– base status. These findings should be evaluated in the context of the physiological changes in pregnancy (see Table 15– 1). A chest radiograph should be performed rather expeditiously to differentiate cardiac versus pulmonary causes of hypoxemia. A large cardiac silhouette may indicate peripartum cardiomyopathy, which is treated by diuretic and inotropic therapy; pulmonary infiltrates may indicate pneumonia or pulmonary edema. A clear chest radiograph in the face of hypoxemia suggests pulmonary embolism, although early in the course of pneumonia, the chest x-ray may appear normal.
The diagnosis of pulmonary embolism may be made presumptively on the basis of high clinical suspicion, hypoxemia, and a clear chest x-ray. In some cases, intravenous heparin is initiated prophylactically while confirmatory testing is ordered. Diagnostic algorithms differ, but chest x-ray followed by either CTPA or V/ Q scan has been shown to be an effective strategy in pregnant patients. Although controversial, CTPA and V/ Q scan appear to provide comparable accuracy in diagnosis PO2 >85 mm Hg, Oxygen saturation >95%
YES NO
Careful examination
Observation
Provide oxygen
Pulmonary findings ?
Cons ider CXR
Exam: rales
CXR:
pulmonary
infiltrates and/or
cardiomegaly
Exam: extensive CXR: clear
wheezing
CXR: clear
Consider:
• Pneumonia
• CHF
• ARDS
• Atelectesis
Test for pulmonary
embolus
• V/Q scan
• Spiral CT
Dx: As thma
• β-Mimetics
• Steroids
• Oxygen
Figure 15–1. Algorithm for evaluation of dyspnea in pregnancy.
as well as similar levels of radiation. The choice of imaging modality will depend on physician preference, patient contraindications, and the speed at which the test can be obtained. Many institutions have CTPA more readily available compared to V/ Q scan. If the patient presents with symptoms of concurrent DVT, compression ultrasonography of the proximal veins should be ordered first.
Once the diagnosis of acute thromboembolism is confirmed, the pregnant woman is usually placed on full intravenous anticoagulation therapy for 5 to 7 days.
Later, the therapy is generally switched to subcutaneous therapy to maintain the aPT T at 1.5 to 2.5 times control (if unfractionated heparin is used) for at least 3 months after the acute event. H eparin, which is a potent thrombin inhibitor that blocks conversion of fibrinogen to fibrin, combines with antithrombin III to stabilize the clot and inhibit its propagation. Both unfractionated heparin and low molecular weight heparin (LMW H ) are safe to use in pregnancy as they do not cross the placenta. LMW H has the advantages of fewer bleeding complications and freedom from aPT T monitoring to assess therapeutic anticoagulation. After 3 months, either full heparinization or “prophylactic heparinization” doses can be utilized for the remainder of the pregnancy and for 6 weeks postpartum. Warfarin is associated with teratogenicity and is rarely used in pregnancy.
Estrogen products, such as oral contraceptive agents, are relatively contraindicated in women diagnosed with pulmonary embolism. Prophylactic anticoagulation for future pregnancies is more controversial, but is often used. Although pregnancy itself may induce thrombosis, many experts advise obtaining tests for other causes of thrombosis such as protein S and protein C deficiency, prothrombin gene
G20210A, antithrombin III activity, Factor V Leiden (FVL) mutation, hyperhomocysteinemia, and antiphospholipid antibodies. Aside from antiphospholipid syndrome, which is typically treated with aspirin and heparin during pregnancy, the remaining thrombophilias without prior history of VTE are usually not given anticoagulation during pregnancy. Specifically, heterozygous Factor V Leiden mutation in the absence of prior VTE is usually not given anticoagulation; however, homozygous FVL or a prior history of VTE confers a much higher thrombosis risk and generally requires anticoagulation.
Table 15-1 • NORMAL ARTERIAL BLOOD GAS CHANGES IN PREGNANCY
Parameter
Nonpregnant
Value
Pregnant
Value Comment
pH 7.40 7.45 Respiratory alkalosis with partial metabolic
compensation
PO
2 (mm Hg) 90–100 95–105 Increased tidal volume leads to increased
minute ventilation and higher oxygen level
PCO
2 (mm Hg) 40 28 Higher tidal volume leads to increased minute
ventilation and lower PCO
2
HCO
3 (mEq/L) 24 19 Renal excretion of bicarbonate to partially
compensate for respiratory alkalosis, leads to
lower serum bicarbonate, making the pregnant
woman more prone to metabolic acidosis
www.myuptodate.com158 CASE FILES: OBSTETRICS AND GYNECOLOGY
Deep Venous Thrombosis
Deep venous thrombosis (DVT ) occurs in slightly < 1% of pregnancies. The pregnant state increases the risk fivefold due to the venous stasis with the large gravid
uterus pressing on the vena cava and the hypercoagulable state due to the increase
in clotting factors. Cesarean delivery further increases the risk of DVT. Although
clots involving the superficial venous system pose virtually no danger and may be
treated with analgesia, DVT is associated with pulmonary embolism in 40% of
untreated cases. The risk of death is increased tenfold when pulmonary embolism
is unrecognized and untreated. Therefore, early diagnosis and anticoagulation
treatment are crucial.
Signs and symptoms of DVT include deep leg pain, linear cords palpated along
the calf, and tenderness and swelling of the lower extremity. A 2-cm difference in
leg circumferences is also highly suggestive. Unfortunately, none of these findings
are very specific for DVT, and in fact, the examination is normal in half of patients
with DVT. H ence, imaging tests are necessary for confirmation.
In pregnancy, the diagnostic test of choice is Doppler ultrasound imaging, which
usually employs a 5- to 7.5-MH z Doppler transducer to measure venous blood
flow with and without compression of the deep veins. This modality is nearly as
sensitive and specific as the time-honored method of contrast venography.
Management of DVT is primarily anticoagulation with bed rest and extremity
elevation. Anticoagulation therapy is the same as pulmonary embolism treatment
with full intravenous doses for 5 to 7 days, followed by subcutaneous therapy for
at least 3 months after the acute event. After 3 months, either full or prophylactic
heparin doses can be utilized for the remainder of the pregnancy and for 6 weeks
postpartum. Patients who have additional risk factors for thromboembolism outside of pregnancy may need long-term anticoagulation.
AMNIOTIC FLUID EMBOLISM
Another clinical scenario that can present similarly to pulmonary embolism is
amniotic fluid embolism (AFE). This occurs when amniotic fluid enters the maternal circulation and subsequently causes obstruction and vasoconstriction of the
pulmonary vessels due to fetal debris and vasoactive substances in the fluid. The
patient may present with sudden dyspnea, hypoxia, hypotension, and coagulopathy. Fetal heart tones often become nonreassuring secondary to hypoperfusion.
AFE most often occurs during labor or immediately postpartum. It is considered an
exceedingly rare event, which is difficult to predict, but there are some risk factors
associated with AFE: caesarian delivery, instrumental vaginal delivery, induction of
labor, traumatic delivery, placental abruption, placenta accreta, advanced maternal
age, and grandmuliparity. The rate of maternal mortality ranges from 20% to 60%
and is typically due to cardiovascular collapse. Treatment is largely supportive with
immediate delivery if there is rapid maternal or fetal decompensation.
MATERNAL MORTALITY
Recent studies on maternal death have shown a pregnancy-related mortality ratio
of 16 per 100 000 live births in the United States, with a slight upward trend
www.myuptodate.comSECTION II: CASES 159
over the years. Ratios are higher in African-American women and tend to increase
with maternal age. The most common overall etiology for maternal mortality is
embolism of all types, followed by cardiovascular conditions and infection. Recent
rates of mortality due to hemorrhage, hypertensive disorders, embolism, and anesthesia complications have declined, whereas cardiovascular conditions and infectious causes have increased. This suggests that the increasing number of pregnant
women with comorbid health conditions may be playing a role in maternal adverse
outcomes.
COMPREHENSION QUESTIONS
15.1 A 32-year-old woman pregnant at 29 weeks’ gestation is noted to have symptoms concerning for a pulmonary embolism. The evaluation included chest
radiograph, arterial blood gas, EKG, and CT pulmonary angiogram. A diagnosis of pulmonary embolism is made. Which of the following is most likely
to be present in this patient?
A. Dyspnea
B. Chest pain
C. Palpitations
D. Hemoptysis
E. Sudden death
15.2 A third-year medical student is assigned to perform a chart review of the cases
of maternal mortality occurring in a hospital over the past 20 years. When the
cases are collated, the student organizes the deaths by etiology. Which of the
following is most likely to be the common underlying mechanism of death?
A. Uterine atony
B. H ypercoagulable state
C. H ypertensive disease
D. Sepsis
E. Rupture of pregnancy through the fallopian tube
15.3 A 28-year-old otherwise healthy woman is found incidentally to have a factor
V Leiden mutation (heterozygous). She is pregnant at 14 weeks’ gestation.
Which of the following is the best management of this patient?
A. Aspirin therapy
B. Expectant management
C. Coumadin (Warfarin) therapy
D. Heparin therapy
www.myuptodate.com160 CASE FILES: OBSTETRICS AND GYNECOLOGY
15.4 A 29-year-old G1P0 woman at 14 weeks’ gestation is seen in the emergency
room for possible diabetic ketoacidosis. The emergency room physician is
evaluating the arterial blood gas which has been performed, and the findings
are listed below. Based on these findings, which of the following is the most
accurate statement?
pH 7.45; PO 2 103 mm H g; PCO 2 31 mm H g; H CO 3 18 mEq/ L
A. The markedly decreased bicarbonate level indicates that the patient likely
has DKA.
B. The decreased PCO
2 indicates that the patient is likely having a panic attack.
C. This arterial blood gas result is normal for pregnancy.
D. The elevated arterial pH reading likely indicates a metabolic alkylosis
condition.
15.5 A 19-year-old G1P0 woman at 29 weeks’ gestation has reactive airway disease. She has received two nebulized albuterol inhalant treatments with still
some wheezing. H er arterial blood gas findings are listed below. Based on
these findings, which of the following is the most accurate statement?
pH 7.40; PO 2 94 mm H g; PCO 2 35 mm H g; H CO 3 20 mEq/ L
A. The low PO
2 level indicates significant exacerbation of the reactive airway disease.
B. The PCO
2 level indicates significant retained PCO 2 and a worrisome
respiratory failure.
C. The arterial blood gas is normal in pregnancy.
D. The serum bicarbonate level is elevated for pregnancy and indicates metabolic alkalosis.
15.6 A 27-year-old G1P0 is at 31 weeks’ gestation. She is seen by her physician
for right leg pain and calf tenderness. A Doppler flow study indicates a deep
venous thrombosis of the right lower extremity. Which of the following is a
reason for the increased incidence of venous thromboembolism in pregnancy?
A. Venous stasis
B. Decreased clotting factors levels
C. Elevated platelet count
D. Endothelial damage
15.7 A 38-year-old G2P1 woman had been diagnosed with a deep venous thrombosis of the right leg when she was at 8 weeks’ gestational age. She has been
on subcutaneous heparin therapy for 6 months. Which of the following is the
most likely result of long-term heparin therapy?
A. Osteoporosis
B. Thrombophilia
C. Fetal intracranial hemorrhage
D. Diabetes mellitus
www.myuptodate.comSECTION II: CASES 161
ANSWERS
15.1 A. Dyspnea is the most common symptom of pulmonary embolus, whereas
tachypnea is the most common sign. Another common symptom is pleuritic
chest pain. A person with a pulmonary embolus may also experience palpitations or feel like they are having an anxiety attack. Few patients will have
hemoptysis. However, these symptoms are not nearly as common as dyspnea.
Sudden death is uncommon, but is more likely in a massive embolus. Patients
with a pre-existing heart or lung condition are at increased risk of mortality.
When a patient presents with dyspnea, the clinician should prioritize the
examination and assessment toward the possibility of significant hypoxia.
15.2 B. Embolism (both thrombotic and amniotic)is the most common cause of
maternal mortality. Pregnant women are predisposed to deep venous thromboses due to the obstructive effects the growing uterus has on the great vessels (ie, vena cava) and the hypercoagulable state of pregnancy, which persists
for about 6 weeks postpartum. H emorrhage typically occurs postpartum,
usually due to uterine atony. The readily available blood products decrease
the likelihood of death. H ypertensive disease is not typically deadly at the
time of diagnosis and can be medically managed before, during, and after
pregnancy. Ectopic pregnancies are usually not deadly unless rupture occurs
and the patient goes into shock. Though this can occur, it is less common
than embolism. Patients usually present with early signs (ie, vaginal bleeding) and symptoms (ie, adnexal pain) of an ectopic pregnancy before rupture
occurs. Sepsis can also send a patient into shock; however, there are usually
signs and symptoms of a bacterial infection (ie, fever, chills, vomiting) that
will prompt medical intervention before there is progression to shock.
15.3 B. A patient who is heterozygous for FVL mutation and never had a VTE
episode is at low risk for developing VTE in pregnancy. Generally, these
patients are expectantly managed and not given anticoagulation. However, if
she had a prior DVT or pulmonary embolism, or was homozygous for FVL
mutation, then heparin (usually low molecular weight) would be advisable.
15.4 C. This arterial blood gas is normal in a pregnant woman. Pregnancy induces a
respiratory alkalosis with partial metabolic compensation. This is the reason the
serum bicarbonate level is decreased as compared to the nonpregnant patient.
15.5 B. This arterial blood gas reveals a PCO 2 of 35 mm H g, which is elevated. In
the face of reactive airway disease, this retained PCO 2 is worrisome, and may
indicate respiratory failure. Initially, with asthma, hyperventilation should be
associated with a decreased PCO
2. When the PCO 2 increases, fatigue, ineffective ventilation, or respiratory failure are possibilities.
15.6 A. Venous stasis is one of the main factors contributing to the hypercoagulable state in pregnancy. Venous stasis is present due to the uterus compressing the vena cava. Usually, the platelet count is slightly lower in the pregnant
state. The lower limit of normal is 150 000/ mm3 in the nonpregnant patient
www.myuptodate.com162 CASE FILES: OBSTETRICS AND GYNECOLOGY
and 120 000/ mm3 in the pregnant woman. There is an increased level of
clotting factors in pregnancy, and this along with venous stasis are the two
factors that increase the risk of DVT in a pregnant woman fivefold. Endothelial damage is part of Virchow’s triad (stasis, hypercoagulability, and endothelial damage) that contributes to thrombosis. It typically does not play a role
during the pregnancy, but rather in the postpartum period when delivery,
especially if surgical, may have caused some vascular damage.
15.7 A. The most common side effect of long-term heparin use in pregnancy is
osteoporosis, usually not apparent unless on the agent for at least a month.
The mechanism is thought to be overactive osteoclast activity as well as
decreased osteoblast activity. Thrombocytopenia and bleeding episodes are
other adverse effects. Heparin-induced thrombocytopenia occurs in < 0.5%
of pregnant women on subcutaneous heparin, and is less common than in
nonpregnant individuals. Thrombocytopenia usually is manifest within the
first 10 days of heparin use. Both unfractionated heparin and LMW H are
associated with thrombocytopenia. Although there is conflicting evidence,
LMW H may have a lower incidence of osteoporosis.
CLINICAL PEARLS
» The diagnosis of pulmonary embolism is suspected in a patient with
dyspnea, a clear chest radiograph, and hypoxemia. It is confirmed with
imaging tests such as ventilation-perfusion scan or CT pulmonary
angiogram.
» The most common presenting symptom of pulmonary embolism is dyspnea.
» Amniotic fluid embolism may present during delivery with sudden
hypoxia, hypotension, coagulopathy, and fetal distress.
» The most common cause of maternal mortality is embolism (both thromboembolism and amniotic fluid embolism).
» APO
2 of <80 mm Hg in a pregnant woman is abnormal.
» The physical examination is not very useful in assessing for deep venous
thrombosis (DVT).
» Venous duplex Doppler sonography is an accurate method to diagnose
DVT.
» After a DVT or pulmonary embolus is diagnosed, anticoagulation is indicated for at least 3 months.
» The most common locations for DVT after gynecologic surgery are the
lower extremities and the pelvic veins.
» Heterozygous Factor V Leiden mutation in the absence of prior VTE
usually does not require anticoagulation during pregnancy.
www.myuptodate.comSECTION II: CASES 163
REFERENCES
American College of Obstetricians and Gynecologists. Prevention of deep vein thrombosis and pulmonary embolism. ACOG Practice Bulletin 84. Washington, DC; 2007.
American College of Obstetricians and Gynecologists. Thromboembolism in pregnancy. ACOG Practice Bulletin 123. Washington, DC; November 2011.
Castro LC, Ognyemi D. Common medical and surgical conditions complicating pregnancy. In: H acker
NF, Gambone JC, H obel CJ, eds. Essentials of Obstetrics and Gynecology. 5th ed. Philadelphia, PA:
Saunders; 2009:191-218.
Clark SR. Amniotic fluid embolism. Obstetrics and Gynecology. 2014;123(2 Pt 1):337-348.
Creanga AA, Berg CJ, Syverson C, Seed K, Bruce FC, Callaghan W M. Pregnancy-related mortality in
the United States, 2006-2010. Obstetrics and Gynecology. 2015;125(1):5-12.
Cunningham FG, Leveno KJ, Bloom SL, H auth JC, Gilstrap LC III, Wenstrom KD. Pulmonary disorders. In: Williams Obstetrics. 22nd ed. New York, N Y: McGraw-H ill; 2005:1055-1072.
Leung AN, Bull TM, Jaeschke R, et al. American Thoracic Society documents: an official American
Thoracic Society/ Society of Thoracic Radiology Clinical Practice Guideline—evaluation of suspected pulmonary embolism in pregnancy. Radiology. 2012;262(2):635-646.
www.myupt
Nhận xét
Đăng nhận xét