PULMONARY EMBOLISM IN PREGNANCYLyle Patterson, M.D.Emergency Medicine Resident St. John Hospital and Medical Center Mrs. Hill is a 26 year old female who is G1P0 with an EGA of 26 weeks confirmed by last menstrual period and first trimester ultrasound. She received prenatal care with her private OB/GYN and was routinely seen in the office once a month prior to the current visit. Mrs. Hill presented to her OB/GYN physician complaining of a three day history of pelvic pain without abdominal cramping or vaginal bleeding. The pelvic pain was nondescript and not associated with any other symptoms. A thorough review of systems was essentially negative. An ultrasound done in the office was normal in regards to fetus and placenta. The patient was reassured that her pregnancy was progressing normally and to return in one week for follow-up. The patient presented to the emergency department the next day complaining of continuing, nondescript pelvic pain, shortness of breath, and anxiety. The patient noted no vaginal bleeding, vaginal discharge, vaginal cramping, change in fetal movement, constipation, urinary symptoms, or previous cardio-pulmonary disease. The patient’s medical history was significant for a previous UTI two years ago. Mrs. Hill’s surgical history revealed a tonsillectomy at the age of five. She only took prenatal vitamins and was allergic to sulfa. A social history revealed no tobacco use, no alcohol intake since the beginning of pregnancy, and no illicit drug use. Mrs. Hill’s vitals in the emergency department were: temperature 98.9, BP 108/64, HR 116, RR 26, and an O2 sat of 92% on room air. The patient appeared anxious, well-nourished, and in mild respiratory distress. Cardiopulmonary examination revealed tachycardia without murmurs, and lung sounds were equal bilaterally without wheezes, rales, or rhonchi. The abdominal examination was completely negative except for a gravid abdomen that was nontender, without rigidity, and without rebound. The lower extremities revealed mild, 1+ edema of the lower extremities without erythema. The patient had no calf tenderness and a negative Homan’s sign. The patient was placed on oxygen via NC at 2 liters which improved her O2 sat to 96%. The attending physician ordered an EKG which revealed sinus tachycardia with nonspecific T wave changes in the lateral and precordial leads without ST elevation/depression or Q waves. A CBC revealed mild microcyctic anemia with a Hb of 11.2 and Hct of 33.5. A BMP was within normal limits. A D-Dimer was elevated at 740. The patient’s LFT’s, calcium, magnesium, CPK, troponin, uric acid, and UA were normal. The physician suspected a pulmonary embolism with the clinical symptoms, positive D-Dimer and ordered a bilateral Doppler ultrasound of the lower extremities which was interpreted as negative for DVT by the radiologist. The patient continued to complain of shortness of breath and anxiety. Mrs. Hill also continued to be tachycardic with a HR above 110. The attending ED physician consulted OB/GYN who recommended IV fluids and a CTA Thorax with abdominal shielding to evaluate for pulmonary embolism. The CTA was positive for acute bilateral proximal pulmonary embolism.
Mrs. Hill was started on heparin and admitted to the MICU and
transferred to the obstetrics floor on hospital day two. She had an
uneventful hospital stay, was changed from intravenous heparin to
Lovenox SQ 1mg/kg q12, and discharged on hospital day three with close
follow-up instructions. Pregnancy is a well-established risk factor for venous thromboembolism (VTE). The risk of venous thromboembolism in pregnant women is estimated to be four times as great as the risk in non-pregnant women, at 1.72 per 1000 pregnancies (1). Pulmonary embolism is also the leading cause of maternal death in the United States (1). The commonly used clinical prediction rules for venous thromboembolic events, such as the Wells Scoring system, have not been validated in pregnancy. This leaves the emergency medicine physician with an important question, how do I evaluate and diagnose VTE in pregnant patients? The ELISA D-Dimer is a sensitive screening test for thromboembolic events, unfortunately, D-dimer levels increase progressively with each trimester of pregnancy. (2). While a normal D-dimer level in a low-risk patient essentially rules out a venous thromboembolic event, how does the emergency physician rule out a VTE in a pregnant patient with an elevated D-dimer? The next logical step in evaluation of VTE with a positive D-dimer is compression ultrasonography. Compression ultrasonography is a relatively safe and noninvasive test that does not expose the fetus to radiation. The sensitivity and specificity of compression ultrasonography reach 97% and 94% respectively in the general population (3). However, in pregnant patients with a normal compression ultrasound and suspicion of pulmonary embolism, further diagnostic evaluation is indicated (4). This is especially true in pregnancy, where pelvic vein and iliac vein thrombosis is felt to be more likely and harder to diagnose with ultrasound secondary to the inability to directly compress the affected veins and associated body habitus.
The emergency physician must then decide, what is the most appropriate
next step? A chest radiograph should be evaluated in order to rule out
an alternative diagnosis and guide further diagnostic evaluation. The
most appropriate next step in evaluating the patient for pulmonary
embolism is either CT pulmonary angiography or V/Q scan. The CT
pulmonary angiography delivers lower levels of radiation to the fetus
(3-131uGy) than V/Q lung scanning (640-800 uGy) (4,5,6). This is an
important consideration in regards to fetal safety and considering only
slightly more than half of physician specialists know that V\Q lung
scanning exposes the fetus to more radiation than CT pulmonary
angiography (5).
VTE is a serious
medical condition, especially in pregnancy where pulmonary embolism is
the leading cause of death in the United States (1). The appropriate
thrombophilic work-up for VTE in pregnant patients is beyond the scope
of this discussion, but should be determined in consultation with
OB/GYN, Fetal Maternal Medicine, and Hematology. The treatment of VTE in
pregnant patients, however, should be initiated immediately with either
LMWH or after 5-10 days with UFH. LMWH, such as enoxaparin, is
considered safe and effective, with fewer bleeding complications (7).
The recommended starting dose is enoxaparin 1 mg/kg SQ BID or dalteparin
100 IU/kg SQ BID. However, if the patient is hospitalized, slightly
higher starting doses may be required secondary to increased renal
clearance and plasma volume occurring during pregnancy (7). Warfarin has
been associated with first trimester fetal complications and CNS
abnormalities after exposure in any trimester and is not routinely used
in the treatment of VTE during pregnancy (7). The use of vena cava
filters in pregnancy is reserved for special cases of extensive deep
venous thrombosis or recurrent VTE after proper anticoagulation. The use
of thrombolytics in pregnancy has not been extensively studied, but may
be appropriate when the patient is unstable and there is risk of
maternal death. # # # Posted:
Tuesday, July 17, 2011
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